University of Nebraska - Lincoln DigitalCommons@University of Nebraska - Lincoln

Dissertations and Student Research in Entomology Entomology, Department of

Summer 7-30-2021

The Impacts of Cover Crops Species and Termination Dates on Arthropod Activity in a Corn Production System

Julia N.D. Campos University of Nebraska-Lincoln

Follow this and additional works at: https://digitalcommons.unl.edu/entomologydiss

Part of the Entomology Commons

N.D. Campos, Julia, "The Impacts of Cover Crops Species and Termination Dates on Arthropod Activity in a Corn Production System" (2021). Dissertations and Student Research in Entomology. 72. https://digitalcommons.unl.edu/entomologydiss/72

This Article is brought to you for free and open access by the Entomology, Department of at DigitalCommons@University of Nebraska - Lincoln. It has been accepted for inclusion in Dissertations and Student Research in Entomology by an authorized administrator of DigitalCommons@University of Nebraska - Lincoln.

THE IMPACTS OF COVER CROP SPECIES AND TERMINATION DATES ON

ARTHROPOD ACTIVITY IN A CORN PRODUCTION SYSTEM

by

Julia Nogueira Darte Campos

A THESIS

Presented to the Faculty of

The Graduate College at the University of Nebraska

In Partial Fulfillment of Requirements

For the Degree of Master of Science

Major: Entomology

Under the Supervision of Professors Anthony Justin McMechan and Robert J. Wright

Lincoln, Nebraska

July 2021

THE IMPACTS OF COVER CROP SPECIES AND TERMINATION DATES ON

ARTHROPOD ACTIVITY IN A CORN PRODUCTION SYSTEM

Julia Nogueira Duarte Campos, M.S.

University of Nebraska, 2021

Advisors: Anthony Justin McMechan and Robert J. Wright

Cover crops can reduce soil erosion, increase water infiltration, and provide an alternative strategy for weed management in cropping systems. Cover crops change the landscape composition by increasing plant biodiversity, potentially impacting pests and beneficial insects. Ecological principles suggest that cover crop management can influence the arthropods in the subsequent cash crop. However, the impact of management strategies such as cover crop species and termination date on arthropod activity in corn systems is not well understood. The objective of this study was to determine the impact of grass cover crop species (wheat, cereal rye, and triticale) in combination with four spring termination dates on arthropod activity. Field studies were conducted in 2018 and 2019 at two locations in Nebraska. Field plots followed a split-plot randomized complete block design with three or four replications. Cover crop termination time was the whole plot treatment, including four termination dates relative to corn planting (-20d, -10d, 0d, and

+5d). Split-plot treatments consisted of the three cover crop species plus a no cover crop treatment as a control. Cover crop biomass and extended leaf height were collected before each termination date in the spring. Arthropod activity was evaluated using pitfall traps installed at the V3, V6, and V10 corn stages of development. Almost 318,000

arthropods were collected and classified to order. Overall, cover crops did not increase pest pressure in any location or year. These results provide growers additional information tools to manage cover crops, reduce risks, and increase beneficial arthropod populations in corn systems.

i

ACKNOWLEDGMENTS

I would like to thank God for all the blessings He gave me throughout my whole life, including the opportunity to pursue my master’s degree and for all the amazing people I had the chance to meet. I would like to thank Drs. Justin McMechan and Robert Wright for their trust in me, all the advice and resources they provide during my program. I also want to say thank you to Dr. Christopher Proctor for being my committee member as well as serving as an example of faith to me. I must express my gratitude to Dr. Justin

McMechan for his valuable guidance during the whole time.

I thank all the incredible lab members that helped me through my journey- Elliot Knoell,

Gabriela Carmona, Osler Ortez, Vilma Montenegro, Debora Montezano, Juan Cardona,

Tauana Almeida, Dania Ozorio, Regina Stacke, Earl Agpawa, Mikaelison Silva, and

Kristin Stark. I really appreciated all the help and support you gave me, and I would not have done without your partnership. I am also thankful to my friends in the department-

Sajjan Grover, Blessing Ademokoya, Molly Darlington, Jordan Reinders, and Matthew

Welter for being there when I needed help and friendship.

A special thanks to Dr. John Ruberson for guiding our department during a pandemic environment and still creating a friendly community within the Entomology Department, invariably with positive energy and willingness to help.

Thanks to all the faculty and staff of the Entomology Department for being so helpful, especially Marilyn Weidner, Kathy Schindler, Marissa Kemp, and Jeri Cunningham, for the life-saving situations you participated in my program. ii

I also want to thank Emily Robinson, a Ph.D. student in the Statistics Department, and all the SC3L Helpdesk consultants that play an important role in my research data analysis.

Thanks for all the support and private classes you happily dedicated to my project, Emily.

I could not leave out my family members that encouraged me more than anything with positive words and strong examples in my life. I want to thank my mother, Silvia, and my father, Geraldo, for being amazing parents and all my relatives for every smile during the million video calls. I also want to remember my relatives that could not be with us today, in special my unbelievable cousin Leticia that was and will ever be my biggest inspiration.

I was fortunate to find a family in Lincoln as well, and without their support, I would never accomplish what I did so far. Thank you – Deb Stephens, Mike and Sherri Bossard,

Ron and Judy Spaulding, John Brejda, Ândrea Reis, Mayara Salvian, Jackson Teixeira,

Elisa Pucu, Murilo Pires, Joaquin Siado, Josefa Samper, Trevor and the Family Hedges.

Thanks to my MIP family- Daniel Chaves, Mirian Pimentel, Izailda Barbosa, and

Obiratanea Haanen.

iii

TABLE OF CONTENTS

CHAPTER 1 ...... 1

Literature Review ...... 1

Cover Crops ...... 2

Cover Crop Benefits ...... 3

Cover Crop Species...... 7

Cover Crop Termination Method...... 10

Cover Crop Termination Time...... 12

Cover Crop-Arthropod Interaction ...... 14

References ...... 17

CHAPTER 2 ...... 24

Impact of Cover Crop Species and Termination Date on Arthropod Activity in a

Corn Rotation System...... 24

Introduction ...... 25

Material and Methods ...... 30

Measurements During Cover Crop Growth...... 30

Biomass ...... 30

Extended Leaf Height ...... 31

Measurements During Corn Growth ...... 31

Arthropod Injury Assessment ...... 31

Arthropod activity ...... 32

Corn Yield ...... 33 iv

Results ...... 34

Measurements During Cover Crop Growth...... 34

Biomass ...... 34 Extended Leaf Height ...... 35 Measurements During Corn Growth ...... 37

Arthropod Activity ...... 37 Corn Yield ...... 48 Discussion...... 51

References ...... 56

Tables ...... 58

Figures ...... 62

v

LIST OF TABLES

Table 2.1 Total arthropod activity groups collected and their percentages of the total per location and year...... 58

Table 2.2. Natural log and equivalent mean of Araneae, Orthoptera, and total arthropod activity collected during at V3, V6, and V10 corn stages at ENREC in 2018...... 59

Table 2.3. Natural log and equivalent mean of Coleoptera, Diptera, and Orthoptera activity collected at V3, V6, and V10 corn stages at ENREC in 2019...... 60

Table 2.4. Natural log and equivalent mean of Acari, Collembola, Diptera, Hymenoptera,

Hemiptera, and total activity collected at V3, V6, and V10 corn stages at SCAL in 2018..

...... 61

vi

LIST OF FIGURES

Figure 2.1. Biomass by cover crop termination date relative to corn planting (B) and cover crop species (A) for ENREC 2018...... 62

Figure 2.2. Biomass for each cover crop termination date relative to corn planting and cover crop species for ENREC 2019...... 63

Figure 2.3. Cover crop biomass for each termination date relative to corn planting (A) for

SCAL 2018 and cover crop biomass per cover crop termination date relative to corn planting and cover crop species (B) for SCAL 2019...... 64

Figure 2.4. Cover crop extended leaf height for each cover crop termination date relative to corn planting and cover crop species for ENREC 2018 (A) and ENREC 2019 (B) .... 65

Figure 2.5. Cover crop extended leaf height per cover crop termination date relative to corn planting and cover crop species for SCAL 2018 (A) and SCAL 2019 (B) ...... 66

Figure 2.6. Natural log of Acari activity collected at pitfall traps per sampling period at

V3, V6, and V10 corn stage per cover crop species at ENREC in 2018...... 67

Figure 2.7. Natural log of Acari activity collected at pitfall traps per sampling period at

V3, V6, and V10 corn stage per cover crop species at ENREC in 2018 ...... 68

Figure 2.8. Natural log of Diptera activity collected at pitfall traps per cover crop termination date relative to corn planting (A) and per sampling period at V3, V6, and V10 corn stage (B) at ENREC in 2018...... 69

Figure 2.9. Natural log of Collembola activity collected at pitfall traps per sampling period at V3, V6, and V10 corn stage per cover crop species at ENREC in 2019 ...... 70 vii

Figure 2.10. Natural log of Collembola activity collected at pitfall traps per sampling period at V3, V6, and V10 corn stage per cover crop species at ENREC in 2019...... 71

Figure 2.11. Natural log of Araneae activity collected at pitfall traps per sampling period at V3, V6, and V10 corn stage per cover crop termination date relative to corn planting at

ENREC in 2019 ...... 72

Figure 2.12. Natural log of total activity collected at pitfall traps per sampling period at

V3, V6, and V10 corn stage per cover crop termination date relative to corn planting at

ENREC in 2019 ...... 73

Figure 2.13. Natural log of Araneae activity collected at pitfall traps per sampling period at V3, V6, and V10 corn stage per cover crop species at SCAL in 2018 ...... 74

Figure 2. 14. Natural log of Orthoptera activity collected at pitfall traps per cover crop termination date relative to corn planting per cover crop species at SCAL in 2018. Red dash lines indicate the mean equivalent of the natural log scale...... 75

Figure 2.15. Natural log of Diptera activity collected at pitfall traps per cover crop termination date relative to corn planting per cover crop species at SCAL in 2018. Red dash lines indicate the mean equivalent of the natural log scale...... 76

Figure 2.16. Natural log of Coleoptera activity collected at pitfall traps per cover crop species treatment (A) and per pitfall sampling period at V3, V6, and V10 corn stage (B) at

ENREC in 2018. Red dash lines indicate the mean equivalent of the natural log scale ... 77

Figure 2.17. Natural log of Collembola activity collected at pitfall traps per sampling period at V3, V6, and V10 corn stage per cover crop termination date relative to corn planting at SCAL in 2019 ...... 78 viii

Figure 2.18. Natural log of Hymenoptera activity collected at pitfall traps per sampling period at V3, V6, and V10 corn stage per cover crop termination date relative to corn planting at SCAL in 2019 ...... 79

Figure 2.19. Natural log of Araneae activity collected at pitfall traps per cover crop termination date relative to corn planting per cover crop species at SCAL in 2019...... 80

Figure 2.20. Natural log of Coleoptera activity collected at pitfall traps per cover crop termination date relative to corn planting per cover crop species (A), per pitfall sampling period at V3, V6, and V10 corn stage per cover crop species (B), per pitfall sampling period at V3, V6, and V10 corn stage per cover crop termination date relative to corn planting (C) at SCAL in 2019 ...... 81

Figure 2.21. Natural log of Hemiptera activity collected at pitfall traps per sampling period at V3 and V6 corn stage per cover crop species (A) and per cover crop termination date relative to corn planting (B) at SCAL in 2019 ...... 82

Figure 2.22. Natural log of Orthoptera activity collected at pitfall traps per cover crop termination date relative to corn planting per cover crop species (A) and per pitfall sampling period at V3, V6, and V10 corn stage per cover crop species (B) at SCAL in 2019

...... 83

Figure 2.23. Natural log of Acari activity collected at pitfall traps per cover crop termination date relative to corn planting per cover crop species (A) and per pitfall sampling period at V3, V6, and V10 corn stage per cover crop termination date relative to corn planting (B) at SCAL in 2019...... 84

Figure 2.24. Natural log of Diptera activity collected at pitfall traps per cover crop termination date relative to corn planting per cover crop species (A) and per pitfall ix sampling period at V3, V6, and V10 corn stage per cover crop termination date relative to corn planting (B) at SCAL in 2019...... 85

Figure 2.25. Natural log of total activity collected at pitfall traps per cover crop termination date relative to corn planting per cover crop species (A) and per pitfall sampling period at

V3, V6, and V10 corn stage per cover crop termination date relative to corn planting (B) at SCAL in 2019 ...... 86

Figure 2.26. Corn yield per cover crop termination date relative to corn planting and cover crop species for ENREC 2018 (A) and ENREC 2019 (B)...... 87

Figure 2.27. Corn yield per cover crop species for SCAL 2018 (A) and per cover crop termination date relative to corn planting and cover crop species for SCAL 2019 (B).

Different letters indicate a significant difference at P <0.05...... 88

1

CHAPTER 1

Literature Review

2

Cover Crops

A cover crop is a non-cash crop cultivated additionally to the main cash crop in an area for conservation purposes. Annual or perennial plants can be used as cover crops, and they can be arranged as a monoculture with a single cover crop species planted or as a mixture with multiple species in the same field. Cover crops are plants cultivated with the primary goal of covering the ground. In Nebraska, cover crops are typically planted in the fall, remaining in the field until the following spring to enhance the field's quality and productivity through improved soil structure and a reduction in soil erosion (Bottenberg et al. 1997, CTIC 2017, Nichols et al. 2020).

A wide variety of plant species can be used as a cover crop, such as grasses, legumes, and brassicas. Each species has specific characteristics that can provide benefits for an area. Grasses and legumes are the most widely used cover crops in corn and soybean rotation systems. Leguminous crops can be divided into winter annual or summer annual cover crops. One of the main reasons to utilize legume cover crop type is the plant's ability to fix nitrogen from the air and incorporate it into the soil. However, grass cover crops can utilize nutrients that were leftover in the soil from the previous cash crop. The most commonly used grasses are categorized as annual cereals, annual or perennial forages, and warm-season grasses. Grasses have a dense fibrous root system and can establish rapidly to aid in reducing soil erosion. Biomass from grass cover crops can also enhance soil organic matter. In addition, cover crop biomass can also help suppress weeds (Nichols et al. 2020) and increase biodiversity (Elhakeem et al. 2019) in the area. However, grasses often consume a lot of nitrogen to reach maturity (the 3 maximum amount of biomass accumulation), which reduces the nitrogen available for the following crop. This problem can be prevented by terminating plants before the maturity phase. Early termination will likely maximize the benefits related to nitrogen usage of grass cover crops in the system.

Some of the cereal grasses used as cover crops are cereal rye (Cereale secale L.), wheat (Triticum aestivum L.), barley (Hordeum vulgare L.), oats (Avena sativa L.), and triticale (x Triticosecale Wittmack). Even though all of them are cereal grasses, they have different attributes that should be considered in the species selection, such as the ability to germinate, establishment time, biomass production, and adaptability to different environments.

The use of cover crops has increased by more than 8% per year between 2013 and

2017 in the USA, according to the 2017 USDA Agriculture Census. A large part of this increase has occurred in the Corn Belt states, with 15.4 million acres of cover crops planted in 2017. In Nebraska, cover crops increased 109.3% from 357,264 to 747,903 acres in 2012 and 2017, respectively (USDA NASS 2017).

Cover Crop Benefits It is well known that cover crops have many benefits for the environment and agricultural production systems (Bayer et al. 2000, Deb et al. 2013, Kaye and Quemada

2017). These benefits are often a result of increased water infiltration, reduction in soil erosion, or as an alternative management tactic for weed control (Crutchfield et al. 1986,

Langdale et al. 1991, Joyce et al. 2002). 4

Studies on the benefits of cover crops in terms of the economics in an agricultural system are limited in the literature (Blanco-Canqui et al. 2015). The lack of sufficient evidence or studies on the economics where cover crops are used and their value likely varies depending on soil type, weather conditions, region, and management practices.

Other more established systems such as no-tillage systems were realized for their economic benefits when they became a long-term practice. An increase of $10.50 per acre was observed compared to the minimal tillage system (Schnitkey et al. 2016).

Historically, the early adoption of cover crops was centered around the need to reduce soil erosion (Parker 1915). Cover crops keep the soil in place when water moves on the surface, and the vegetation above the soil surface helps to dissipate the raindrop energy impact (Wischmeier and Smith 1978).

Cover crops can reduce evaporation and increase water availability for plants by increasing water retention (Basche et al. 2016) and water infiltration (Blanco-Canqui et al. 2011) in the soil. Cover crops will also protect the soil surface against erosion by absorbing most of the raindrop impact from irrigation or rainfall, delaying runoff, and enhancing soil surface roughness (Blanco-Canqui et al. 2011, Basche, Kaspar, et al.

2016). In addition, model simulations suggested that areas with cover crops are less susceptible to soil particle breakdown, which reduces a subsequent surface seal formation in case of heavy rainfall (Joyce et al. 2002). There is also evidence of the improved water-holding capacity of soils within the root zone in areas with cover crops (Joyce et al.

2002, Qi and Helmers 2010). 5

Cover crops have been shown to reduce losses of dissolved nutrients in the soil in

Missouri, but the reduction varies according to each nutrient analyzed (Zhu et al. 1989).

In Missouri, phosphorus loss was reduced 7% to 61% using cover crops, and nitrogen losses were reduced by 35% to 77% (Zhu et al. 1989). In New York state, a 74% reduction in total phosphorus loads in runoff was observed when cover crops were used

(Kleinman et al. 2005). Those results indicate that, by reducing water erosion, cover crops also improve water quality and reduce pollution in water sources (Blanco-Canqui et al. 2015).

Cover crops have the potential to suppress weeds in agricultural systems; however, the efficacy of weed suppression depends on many factors, such as cover crop growth, biomass production, and termination date and method (Mirsky et al. 2011).

Furthermore, the impact of cover crops on weed populations can occur in two ways, through direct or indirect weed suppression (Teasdale et al. 2007). The direct effect is a result of the living mulches in the field whereas the indirect effect can result from a physical or chemical suppression and manipulations of nutrient cycles by cover crops

(Teasdale et al. 1991, Teasdale and Mohler 2000, Weston and Duke 2003).

Since many cover crops are planted in the fall in the midwestern U.S., plant residues following the spring termination will help suppress the weed populations early in the cash crop season (Uchino et al. 2009). The competition for light, water, and nutrients can reduce weed emergence, consequently reducing the production of seeds, which will reduce the soil weed seed bank in the area (Teasdale and Mohler 2000). The direct competition between cover crops and weeds can be quantified by measuring the biomass 6 production of plants (Akbari et al. 2019). The impact of cover crop biomass production on weed density; however, can differ depending on the weed species; most perennial weed species are not affected by residues under the soil surface (Facelli and Pickett

1991). However, annual broadleaf weeds can be strongly impacted by cover crop biomass and weed suppression can increase as cover crop biomass production is higher (Mirsky et al. 2011). Furthermore, the quantity of cover crop residue produced is more important than the source as a factor for weed suppression (Teasdale and Mohler 2000).

Indirect or direct chemical impacts on weeds can occur because of allelochemical production in plants (Einhellig 1994). Some cover crop species are known to produce allelochemicals in large quantities, and one example is a cereal rye cultivar named

Wheeler that can produce 2,4-dihydroxy-1,4- (2H) benzoxazine-3-one (DIBOA) in higher concentrations later in the season (Reberg-Horton et al. 2005). High levels of

DIBOA reduce root elongation in weeds, and it is two or three times more effective on small-seeded rather than large-seeded weeds (Burgos and Talbert 2000). Allelochemical mechanisms that suppress weeds are not well understood; however, the physical barrier is considered the primary mechanism for weed suppression with cover crops (Teasdale and

Mohler 2000).

Many cover crop benefits reported in the literature are the results of a long-term strategy (Blanco-Canqui et al. 2011, Basche et al. 2016). However, contributions can be obtained in a short period of time after cover crop adoption (Dabney et al. 1988, Mirsky et al. 2011, Kulagowski et al. 2016). Some of the short-term benefits from cover crops include the reduction of soil erosion, nitrogen cycling, and surface nutrient loading (Roth 7 et al. 2017). However, even with all the cover crop research conducted so far, there is a lack of information on the economic benefits, allelochemical mechanisms of weed suppression, and impacts on the arthropod community (Schipanski et al. 2014).

Cover Crop Species Cover crops can be divided into groups, such as grasses, legumes, and brassicas.

Within groups, some species will respond differently to pH levels, soil type and fertility, precipitation, temperature, solar radiation, and other abiotic factors. The selection of the cover crop species is an essential component for maximizing cover crop benefits based on the growers' needs or goals.

Maximizing the biomass production of a cover crop is a common goal, and species selection can be a critical factor in a different environment. Non-winterkilled species produce greater biomass than winter-killed cover crops. However, winter-killed species, such as forage radish, can produce more biomass during the fall before a killing frost. Cover crops that survive the winter will resume their growth in the spring; therefore, they have a larger final biomass accumulation (Akbari et al. 2019).

Uchino et al. (2011) correlated plant height and biomass coverage from the cover crop with weed suppression. The study found that even though oat was the tallest cover crop, it did not suppress weeds efficiently compared with cereal rye, a species with a shorter structure. Species that produce more aboveground biomass will better inhibit weed growth (Uchino et al. 2011). A meta-analysis on cover crop biomass production found that the biomass of a cover crop was inversely proportional to the density and biomass of weeds (Osipitan et al. 2019). A subsequent study has supported the previous 8 results showing that as cover crop biomass increased, there was a reduction in weed biomass (Ranaldo et al. 2020).

Grass cover crops are commonly used because of the extensive root system and rapid establishment, essential factors for reducing soil erosion. Additionally, they can produce residues in large quantities, increasing organic matter to the soil, besides increasing weed suppression. (SARE 2017). As a result, a significant emphasis has been placed on grass cover crops since it is the leading group adopted in the Corn Belt region in the USA

Cereal rye (Cereale secale L.) is a commonly used cover crop in the Midwest

(Singer 2008) due to its rapid germination and allelopathic properties that aid in weed suppression (Barnes and Putnam 1983, Shilling et al. 1985). Weed biomass can be reduced up to 50 to 75% throughout the season when rye cover crop residues are left after spring termination (Masiunas et al. 1995, Moyer et al. 2000). Nagabhushana et al. (2001) identified rye as having the highest weed suppression among cover crops evaluated.

Besides that, the control of broadleaf weeds during the early season was between 80 to

90% using rye as a cover crop.

Corn yield after cereal rye cover crop has presented conflicting results (Martinez-

Feria et al. 2016). Some authors observed a yield reduction of corn planted after rye cover crop previously present in the field (Singer and Kohler 2005, Singer 2008, Pantoja et al. 2015). In contrast, other authors did not observe a yield reduction in their system at

Iowa State (Basche et al. 2016) 9

Wheat (Triticum aestivum L.) is typically cultivated as cash crop; however, it can be planted as a cover crop and provides similar benefits compared to other cereal cover crops (SARE 2007). Wheat has low cost, is a versatile cover crop, and its management is often familiar for growers (Adeyemi et al. 2020). In Illinois, wheat was able to uptake from the soil up to 25 kg N ha-1 when the cover crop was terminated in early April

(Weidhuner et al. 2019). Rye usually produced more dry biomass than wheat as a cover crop, but weed biomass was the same when both cover crop species were compared

(Reddy 2001). Some of the benefits that wheat can bring to a farm are preventing soil erosion, weed suppression, scavenging excess nutrients, and increased organic matter

(SARE 2007).

Triticale (x Triticosecale Wittmack) is a grass species obtained by wheat and cereal rye cross (Stace 1987). The first plants were infertile, and after some breeding techniques, the new species was fertile and able to adapt to different environmental conditions (Mergoum et al. 2009, Blum 2014). Triticale is an important crop that combines the efficiency to use nutrients as cereal rye and increased grain production and nutritional qualities as wheat (Furman et al. 1997, Dennett et al. 2013). Triticale showed an excellent biomass accumulation and yield production; it can be compared with cereal rye and even superior to wheat for those criteria (Mergoum and Macpherson 2004,

Kavanagh and Hall 2015).

Globally, triticale has been cultivated on over four million hectares each year for grain production (FAOSTAR, 2014). In the USA, triticale was used to feed animals and recently was adopted as a cover crop (Blount et al. 2017b). Even though triticale has the 10 potential to be used as a cover crop, it is still confined to a relatively small number of acres in the USA. Compared to wheat or cereal rye, triticale has not received much attention in breeding and funding programs (Blum 2014). This lack of investment is likely due to triticale's reduced qualities for human consumption and high seed price compared with other cereals (Blount, et al. 2017a). Until recently, growers were not covered by crop insurance when they used triticale plants as a cover crop species (USDA,

2017). However, the high performance in several environmental conditions makes triticale an advantageous option over wheat and other cover crop species (Blum 2014,

Kavanagh and Hall 2015).

Cover Crop Termination Method At least eight methods for terminating cover crops have been reported in studies and can affect how the cover will benefit the following cash crop (Carmona et al. 2021).

Growers can terminate cover crops using mechanical or chemical methods. Most conventional farmers utilize chemical applications to terminate cover crops, whereas organic producers will rely on tillage and other methods such as roller crimper (Price et al. 2009). Regardless of the crop system in which cover crops are implemented, the termination method selected should be the most efficient.

Rye, wheat, and black oat were terminated using different rates of glyphosate alone or followed by the rolling method. Mechanical termination applied after glyphosate applications did not increase plant control for any of the three cover crop species (Prince et al. 2009). In this study, rolling immature cereal cover crops did not provide benefits, 11 whereas glyphosate at 0.84 kg ae/ha was effective when used on less mature plants

(Prince et al. 2009).

Price et al. (2009) conducted a study to compare rolling crimping and chemical termination; there was a yield increase in rolling treatments compared with chemical termination in a cotton production system. Those results show that rolling can be a helpful method for organic farms as a mechanical method of termination. It can conserve more soil moisture with more mature winter cover crops when compared with standing crops while rolling less mature cereal cover crops does not provide benefits (Price et al.

2009).

Conventional growers can terminate winter cover crops and annual grasses using glyphosate-based herbicide applications. In broadleaf cover crops, the termination can be improved by adding 2,4-D or dicamba to the glyphosate solution (Cornelius and Bradley

2017). Chemical applications using glyphosate alone can effectively terminate cereal rye

(Zadoks Growth Scale 50, first spikelet of head just visible), wheat (Zadoks Growth

Scale 59, all heads out of sheath), and black oat (Zadoks Growth Scale 50, first spikelet of head just visible) (Price et al. 2009). Ideally, cover crops should be terminated with one herbicide application to reduce operational costs. Galloway and Weston (1996) obtained successful control of rye and vetch mixtures after a single glyphosate application, however, this response can vary with different cover crop groups. For clover cover crops, first application only initially suppressed the plants, which required additional operations. Even with herbicide applications available, conventional growers face challenges identifying the best moment or product to apply. 12

Cover Crop Termination Time The timing of termination of a cover crop relative to its stage, cash crop planting date, and weather conditions are critical factors to consider in order to avoid additional applications or yield losses in the subsequent cash crop. Ideally, cover crops should be terminated at the point where biomass production promotes the maximum benefit while also reduced risk of cover crops becoming a weed or a source for pathogens or pests in the area.

To help growers achieve their goals related to conservation benefits and reduce potential impacts on their subsequent cash crops, the USDA Natural Resource

Conservation Service created termination guidelines (NRCS 2019). The USA is divided into four termination zones (NRCS 2019), providing recommendations for the latest date to terminate a cover crop based on limited water availability.

Depending on the method used, early termination of a cover crop can be effective

(Prince et al. 2009). Low doses of glyphosate or rolling method alone were not successful in controlling immature cover crop species (Prince et al. 2009). The same pattern was also shown by Ashford and Reeves (2003), who concluded that there was no difference between cover crop types, but the plant stage was the main factor to determine the effectiveness of cover crop termination using the roller method. When used alone, the roller-crimper did not kill the plants at flag leaf stage effectively. In contrast, the roller- crimper increased its efficacy at the anthesis developmental stage but was still less effective than chemical methods. When the cover crops rye, wheat, and black oat were at the milk stage of development, the roller-crimper showed 93% effectiveness at 13 termination, which represents a cost reduction of $26.28/ha by using only roller-crimper instead of glyphosate application after the plants reached anthesis (Ashford and Reeves

2003).

Herbicide applications are typically most effective early in the spring when the plants are small. Cornelius and Bradley (2017) tested 18 herbicide treatments at different application dates, which showed that the early April cover crop control was higher than early May applications. They also observed a difference in cover crop termination varying within cover crop group, the control of broadleaf cover crops was more effective using paraquat treatments in May than in April application (Cornelius and Bradley 2017).

Cover crops accumulate a large amount of biomass in spring, and as a result the termination date can significantly impact their total biomass. Duiker (2014) tested rye, wheat, barley, annual ryegrass, hairy vetch, crimson clover, and rape cover crops and analyzed biomass production three times during the season during early-May mid-May, and early-June. On average, the biomass production in June was double compared to early and middle May. In addition, Mirsky et al. (2011) showed an increase of 37% of the biomass accumulation for the average between Aroostook rye, Wheeler rye, and cereal rye/hairy vetch in an interval of 10 days. Wagger (1989) reported increased biomass levels specific for each species by delaying termination by only two weeks. His results showed an enhancement of 39%, 41%, and 61% of biomass production on rye, crimson clover, and hairy vetch, respectively. In contrast, Wayman et al. (2015) tested early and late termination treatments relative to the cover crop species development using rye

(three varieties), barley, and hairy vetch (four varieties); and found no differences 14 between termination dates. Environmental conditions, especially temperature, during the experiment were considered responsible for similar biomass accumulation.

The risk of seedling diseases can also be affected by the timing of the cover crop termination. Cereal rye treatments terminated closer to the corn planting date had increased seedling disease, reduced corn emergence, and reduced yield compared to terminations occurring ten days before planting corn (Acharya et al. 2017). Late termination of winter cereal cover crops can increase seedling disease and stand loss and decrease plant vigor and corn yield (Smiley et al. 1992, Rothrock et al. 1995, Dabney et al. 1996, Bakker et al. 2016, Sharma-Poudyal et al. 2016). The risks of plant pathogen carry over from cover crops can be reduced by terminating cover crops two to three weeks before cash crop planting date (Munawar et al. 1990, Raimbult et al. 1991, Ball

Coelho et al. 2005).

Cover Crop-Arthropod Interaction Cover crops can increase the biodiversity in the landscape when in rotation with other cash crops (Andow 1991a). It is expected that areas with a larger plant diversity will have a larger diversity of arthropods (Root 1973). In addition, cover crops may create a favorable environment for natural enemies by offering alternative food sources, such as pollen or nectar, or even refuge (Landis et al. 2000).

Planting cover crops increases the chance of a higher abundance of natural enemies, consequently causing negative effects on the pest population (Sunderland and

Samu 2000, Symondson et al. 2002, Langellotto and Denno 2004, Letourneau et al.

2011). Previous research has found that cover crops had positive effects on natural enemy 15 populations (Prasifka et al. 2006, Schmidt et al. 2007) and adverse effects on insect pests

(Tillman et al. 2004, Koch et al. 2012). However, the relationship between cover crop adoption and how pest and beneficial arthropods can be impacted in a rotation system is not entirely understood (Cardina et al. 1996, Landis et al. 2000, Shearin et al. 2008,

Dunbar et al. 2017).

Many factors can influence the arthropod presence in a cover crop system. Some of the factors are abiotic, such as rain, sunlight, temperatures, and soil type. Most of the time, growers have little or no control over these abiotic factors. There are also biotic factors related to management strategies that growers can control, such as the type and species of cover crops used, and when to plant and terminate cover crops. All these factors can likely influence arthropod population diversity and abundance.

Shearin et al. (2008) compared four cover crop systems (cereal rye/vetch, clover/oat, pea/oat, and brassica/buckwheat) against control plots without plants; they found that Harpalus rufipes Latreille (Coleoptera: Carabidae) activity was three times higher in cover crop treatments than in the control areas. Dunbar et al. (2017) also studied the impact of cover crops on arthropods, and there was a limited effect on beneficial arthropods caused by cereal rye as a cover crop. From Dunbar's experiment, a single group of arthropods (Coleoptera: Carabidae) was positively affected by the rye cover crop presence compared to no-cover crop treatments. Most of the research on cover crop management and its impacts on the arthropod community was published after 1990, indicating that this area of knowledge has a lot to be discussed (Landis et al. 2000). 16

Arthropod groups are expected to be affected differently with an increase in plant diversity. A study made with different cover crop combinations showed that when adults of H. rufipes (Coleoptera: Carabidae) that were released on cover crop plots (pea/oat and rye/vetch) were recaptured in the same treatment more often when compared with the control treatment without cover crops (Shearin et al. 2008). In another study, insects belonging to the family Gryllidae (Order: Orthoptera) were significantly more present in the control plots (without cover crops) than areas with rye as a cover crop (Dunbar et al.

2017). Considering pest species, the response to plant diversity can vary. Comparing different levels of plant diversity, monophagous and polyphagous pest abundance can respond differently (Root 1973, Andow 1991b).

17

References

Acharya, J., M. G. Bakker, T. B. Moorman, T. C. Kaspar, A. W. Lenssen, and A. E. Robertson. 2017. Time interval between cover crop termination and planting influences corn seedling disease, plant growth, and yield. Plant disease. 101: 591– 600.

Akbari, P., S. J. Herbert, M. Hashemi, A. V. Barker, and O. R. Zandvakili. 2019. Role of Cover Crops and Planting Dates for Improved Weed Suppression and Nitrogen Recovery in No till Systems. Communications in Soil Science and Plant Analysis. 50: 1722–1731.

Andow, D. A. 1991a. Yield Loss to Arthropods in Vegetationally Diverse Agroecosystems. Environmental Entomology. 20: 1228–1235.

Andow, D. A. 1991b. Vegetational Diversity and Arthropod Population Response. Annu. Rev. Entomol. 36:561-586.

Arbuckle, J. G., and G. Roesch-McNally. 2015. Cover crop adoption in Iowa: The role of perceived practice characteristics. Journal of Soil and Water Conservation. 70: 418–429.

Bakker, M. G., J. Acharya, T. B. Moorman, A. E. Robertson, and T. C. Kaspar. 2016. The Potential for Cereal Rye Cover Crops to Host Corn Seedling Pathogens. Phytopathology. 106: 591–601.

Ball Coelho, B. R., R. C. Roy, and A. J. Bruin. 2005. Long-term effects of late-summer overseeding of winter rye on corn grain yield and nitrogen balance. Can. J. Plant Sci. 85: 543–554.

Barnes, J. P., and A. R. Putnam. 1983. Rye residues contribute weed suppression in no- tillage cropping systems. J Chem Ecol. 9: 1045–1057.

Basche, A. D., S. V. Archontoulis, T. C. Kaspar, D. B. Jaynes, T. B. Parkin, and F. E. Miguez. 2016. Simulating long-term impacts of cover crops and climate change on crop production and environmental outcomes in the Midwestern United States. Agriculture, Ecosystems & Environment. 218: 95–106.

Basche, A. D., T. C. Kaspar, S. V. Archontoulis, D. B. Jaynes, T. J. Sauer, T. B. Parkin, and F. E. Miguez. 2016. Soil water improvements with the long-term use of a winter rye cover crop. Agricultural Water Management. 172: 40–50.

Bayer, C., J. Mielniczuk, T. J. C. Amado, L. Martin-Neto, and S. V. Fernandes. 2000. Organic matter storage in a sandy clay loam Acrisol affected by tillage and cropping systems in southern Brazil. Soil and Tillage Research. 54: 101–109. 18

Blanco-Canqui, H., M. M. Mikha, D. R. Presley, and M. M. Claassen. 2011. Addition of Cover Crops Enhances No-Till Potential for Improving Soil Physical Properties. Soil Science Society of America Journal. 75: 1471–1482.

Blanco-Canqui, H., T. M. Shaver, J. L. Lindquist, C. A. Shapiro, R. W. Elmore, C. A. Francis, and G. W. Hergert. 2015. Cover Crops and Ecosystem Services: Insights from Studies in Temperate Soils. Agronomy Journal. 107: 2449–2474.

Blount, A. R., R. D. Barnett, P. L. Pfahler, J. W. Johnson, G. D. Buntin, and B. M. Cunfer. 2017. Rye and Triticale Breeding in the South. 2.

Blount, A. R., B. Myer, C. Mackowiak, and R. Barnett. 2017. Triticale as a Forage Crop for the Southeastern United States. 4.

Blum, A. 2014. The abiotic stress response and adaptation of triticale — A review. Cereal Research Communications. 42: 359–375.

Bottenberg, H., J. Masiunas, C. Eastman, and D. Eastburn. 1997. Yield and Quality Constraints of Cabbage Planted in Rye Mulch. Biological Agriculture & Horticulture. 14: 323–342.

Burgos, N. R., and R. E. Talbert. 2000. Differential activity of allelochemicals from Secale cereale in seedling bioassays. Weed Science. 48: 302–310.

Cardina, J., and D. H. Sparrow. 1996. A Comparison of Methods to Predict Weed Seedling Populations from the Soil Seedbank. Weed Science. 44: 46–51.

Cornelius, C. D., and K. W. Bradley. 2017. Herbicide Programs for the Termination of Various Cover Crop Species. Weed Technol. 31: 514–522.

Crutchfield, D. A., G. A. Wicks, and O. C. Burnside. 1986. Effect of Winter Wheat (Triticum aestivum) Straw Mulch Level on Weed Control. Weed Science. 34: 110–114.

CTIC. 2020. Report of the 2019-2020 National Cover crop Survey. Conservation Technology Information Center/North Central Region Sustainable Agriculture Research and Education Program/American Seed Trade Association, West Lafayette, IN. https://www.ctic.org/files/CoverCropSurvey%202020%2024mb.pdf

Dabney, S. M., J. D. Schreiber, C. S. Rothrock, and J. R. Johnson. 1996. Cover Crops Affect Sorghum Seedling Growth. Agron. J. 88: 961–970.

Deb, S. K., M. K. Shukla, P. Sharma, and J. G. Mexal. 2013. Soil water depletion in irrigated mature pecans under contrasting soil textures for arid Southern New Mexico. Irrig Sci. 31: 69–85. 19

Dennett, A. L., K. V. Cooper, and R. M. Trethowan. 2013. The genotypic and phenotypic interaction of wheat and rye storage proteins in primary triticale. Euphytica. 194: 235–242.

Duiker, S. W. 2014. Establishment and Termination Dates Affect Fall-Established Cover Crops. Agronomy Journal. 106: 670–678.

Dunbar, M. W., A. J. Gassmann, and M. E. O'Neal. 2017. Limited Impact of a Fall- Seeded, Spring-Terminated Rye Cover Crop on Beneficial Arthropods. Environmental Entomology. 46: 284–290.

Facelli, J. M., and S. T. A. Pickett. 1991. Plant Litter: Light Interception and Effects on an Old-Field Plant Community. Ecology. 72: 1024–1031.

Furman, B. J., C. O. Qualset, B. Skovmand, J. H. Heaton, H. Corke, and D. M. Wesenberg. 1997. Characterization and Analysis of North American Triticale Genetic Resources. Crop Sci. 37: 1951–1959.

Galloway, B. A., and L. A. Weston. 1996. Influence of Cover Crop and Herbicide Treatment on Weed Control and Yield in No-Till Sweet Corn ( Zea mays L.) and Pumpkin ( Cucurbita maxima Duch.). Weed technol. 10: 341–346.

Joyce, B. A., W. W. Wallender, J. P. Mitchell, L. M. Huyck, S. R. Temple, P. N. Brostrom, and T. C. Hsiao. 2002. INFILTRATION AND SOIL WATER STORAGE UNDER WINTER COVER CROPPING IN CALIFORNIA'S SACRAMENTO VALLEY.

Kaspar, T. C., and M. G. Bakker. 2015. Biomass production of 12 winter cereal cover crop cultivars and their effect on subsequent no-till corn yield. Journal of Soil and Water Conservation. 70: 353–364.

Kavanagh, V., and L. Hall. 2015. Biology and Biosafety, pp. 3–13. In Eudes, F. (ed.), Triticale. Springer International Publishing, Cham.

Kaye, J. P., and M. Quemada. 2017. Using cover crops to mitigate and adapt to climate change. A review. Agron. Sustain. Dev. 37: 4.

Kleinman, P. J. A., P. Salon, A. N. Sharpley, and L. S. Saporito. 2005. Effect of cover crops established at time of corn planting on phosphorus runoff from soils before and after dairy manure application. Journal of Soil and Water Conservation. 60: 311.

Koch, R. L., P. M. Porter, M. M. Harbur, M. D. Abrahamson, K. A. G. Wyckhuys, D. W. Ragsdale, K. Buckman, Z. Sezen, and G. E. Heimpel. 2012. Response of Soybean Insects to an Autumn-Seeded Rye Cover Crop. Environ Entomol. 41: 750–760. 20

Landis, D. A., S. D. Wratten, and G. M. Gurr. 2000. Habitat Management to Conserve Natural Enemies of Arthropod Pests in Agriculture. Annu. Rev. Entomol. 45: 175–201.

Langdale, G. W., R. L. Blevins, D. L. Karlen, D. K. McCool, M. A. Nearing, E. L. Skidmore, A. W. Thomas, D. D. Tyler, and J. R. Williams. 1991. Cover crop effects on soil erosion by wind and water.

Langellotto, G. A., and R. F. Denno. 2004. Responses of invertebrate natural enemies to complex-structured habitats: a meta-analytical synthesis. Oecologia. 139: 1–10.

Letourneau, D. K., I. Armbrecht, B. S. Rivera, J. M. Lerma, E. J. Carmona, M. C. Daza, S. Escobar, V. Galindo, C. Gutiérrez, S. D. López, J. L. Mejía, A. M. A. Rangel, J. H. Rangel, L. Rivera, C. A. Saavedra, A. M. Torres, and A. R. Trujillo. 2011. Does plant diversity benefit agroecosystems? A synthetic review. Ecological Applications. 21: 9–21.

Martinez-Feria, R. A., R. Dietzel, M. Liebman, M. J. Helmers, and S. V. Archontoulis. 2016. Rye cover crop effects on maize: A system-level analysis. Field Crops Research. 196: 145–159.

Masiunas, J. B., L. A. Weston, and S. C. Weller. 1995. The Impact of Rye Cover Crops on Weed Populations in a Tomato Cropping System. Weed sci. 43: 318– 323.

Mergoum, M., and H. G. Macpherson. 2004. Triticale Improvement and Production. Food & Agriculture Organization.

Mergoum, M., P. K. Singh, R. J. Peña, A. J. Lozano-del Río, K. V. Cooper, D. F. Salmon, and H. Gómez Macpherson. 2009. Triticale: A “New” Crop with Old Challenges. Cereals. 267–287.

Miguez, F. E., and G. A. Bollero. 2005. Review of Corn Yield Response under Winter Cover Cropping Systems Using Meta‐Analytic Methods. Crop Sci. 45: 2318– 2329.

Mirsky, S. B., W. S. Curran, D. M. Mortenseny, M. R. Ryany, and D. L. Shumway. 2011. Timing of cover-crop management effects on weed suppression in no-till planted soybean using a roller-crimper. Weed Science. 59: 380–389.

Moyer, J. R., R. E. Blackshaw, E. G. Smith, and S. M. McGinn. 2000. Cereal cover crops for weed suppression in a summer fallow-wheat cropping sequence. Can. J. Plant Sci. 80: 441–449.

Munawar, A., R. L. Blevins, W. W. Frye, and M. R. Saul. 1990. Tillage and Cover Crop Management for Soil Water Conservation. Agron. J. 82: 773–777. 21

Osipitan, O. A., J. A. Dille, Y. Assefa, E. Radicetti, A. Ayeni, and S. Z. Knezevic. 2019. Impact of Cover Crop Management on Level of Weed Suppression: A Meta-Analysis. Crop Science. 59: 833–842.

Pantoja, J. L., K. P. Woli, J. E. Sawyer, and D. W. Barker. 2015. Corn Nitrogen Fertilization Requirement and Corn-Soybean Productivity with a Rye Cover Crop. Soil Science Society of America Journal. 79: 1482–1495.

Parker, E. C. 1915. Field Management and Crop Rotation: Planning and Organizing Farms; Crop Rotation Systems; Soil Amendment with Fertilizers; Relation of Animal Husbandry to Soil Productivity; and Other Important Features of Farm Management. Webb Publishing Company.

Prasifka, J. R., N. P. Schmidt, K. A. Kohler, M. E. O’Neal, R. L. Hellmich, and J. W. Singer. 2006. Effects of Living Mulches on Predator Abundance and Sentinel Prey in a Corn–Soybean–Forage Rotation. Environmental entomology. 35: 9.

Price, A. J., F. J. Arriaga, R. L. Raper, K. S. Balkcom, T. S. Komecki, and D. W. Reeves. 2009. Comparison of Mechanical and Chemical Winter Cereal Cover Crop Termination Systems and Cotton Yield In Conservation Agriculture. 13: 8.

Qi, Z., and M. J. Helmers. 2010. Soil Water Dynamics under Winter Rye Cover Crop in Central Iowa. Vadose Zone Journal. 9: 53–60.

Raimbult, B. A., T. J. Vyn, and M. Tollenaar. 1991. Corn Response to Rye Cover Crop, Tillage Methods, and Planter Options. Agron. J. 83: 287–290.

Ranaldo, M., S. Carlesi, A. Costanzo, and P. Bàrberi. 2020. Functional diversity of cover crop mixtures enhances biomass yield and weed suppression in a Mediterranean agroecosystem. Weed Res. 60: 96–108.

Reberg-Horton, S. C., J. D. Burton, D. A. Danehower, G. Ma, D. W. Monks, J. P. Murphy, N. N. Ranells, J. D. Williamson, and N. G. Creamer. 2005. Changes over time in the allelochemical content of ten cultivars of rye (Secale cereale L.). J Chem Ecol. 31: 179–193.

Root, R. B. 1973. Organization of a Plant-Arthropod Association in Simple and Diverse Habitats: The Fauna of Collards (Brassica Oleracea). Ecological Monographs. 43: 95–124.

Rothrock, C. S., T. L. Kirkpatrick, R. E. Frans, and H. D. Scott. 1995. The influence of winter legume cover crops on soilborne plant pathogens and cotton seedling diseases. Plant Disease. 79: 167–171.

Schmidt, N. P., M. E. O'Neal, and J. W. Singer. 2007. Alfalfa Living Mulch Advances Biological Control of Soybean Aphid. Environmental entomology. 36: 9. 22

Schnitkey, G., J. Coppess, and N. Paulson. 2016. Costs and Benefits of Cover Crops: An Example with Cereal Rye https://farmdocdaily.illinois.edu/2016/07/costs-and- benefits-of-cover-crops-example.html

Sharma-Poudyal, D., T. C. Paulitz, and L. J. du Toit. 2016. Timing of Glyphosate Applications to Wheat Cover Crops to Reduce Onion Stunting Caused by Rhizoctonia solani. Plant Disease. 100: 1474–1481.

Shearin, A. F., S. Chris Reberg-Horton, and E. R. Gallandt. 2008. Cover Crop Effects on the Activity-Density of the Weed Seed Predator Harpalus rufipes (Coleoptera: Carabidae). Weed sci. 56: 442–450.

Shilling, D. G., R. A. Liebl, and A. D. Worsham. 1985. Rye (Secale cereale L.) and Wheat (Triticum aestivum L.) Mulch: The Suppression of Certain Broadleaved Weeds and the Isolation and Identification of Phytotoxins, pp. 243–271. In Thompson, A.C. (ed.), The Chemistry of Allelopathy, ACS Symposium Series. American Chemical Society, Washington, D.C.

Singer, J. W. 2008. Corn Belt Assessment of Cover Crop Management and Preferences. Agron. J. 100: 1670–1672.

Singer, J. W., and K. A. Kohler. 2005. Rye Cover Crop Management Affects Grain Yield in a Soybean-Corn Rotation. Crop Management. 4: 1–6.

Smiley, R. W., A. G. Ogg, and R. James Cook. 1992. Influence of glyphosate on Rhizoctonia root rot, growth, and yield of barley. Plant Disease. 76: 937–942.

Stace, C. A. 1987. Triticale: A Case of Nomenclatural Mistreatment. Taxon. 36: 445– 452.

Sunderland, K., and F. Samu. 2000. Effects of agricultural diversification on the abundance, distribution, and pest control potential of spiders: a review. Entomologia Experimentalis et Applicata. 95: 1–13.

Symondson, W. O. C., K. D. Sunderland, and M. H. Greenstone. 2002. Can Generalist Predators be Effective Biocontrol Agents? Annu. Rev. Entomol. 47: 561–594.

Teasdale, J. R., C. E. Beste, and W. E. Potts. 1991. Response of Weeds to Tillage and Cover Crop Residue. Weed sci. 39: 195–199.

Teasdale, J. R., C. B. Coffman, and R. W. Mangum. 2007. Potential Long-Term Benefits of No-Tillage and Organic Cropping Systems for Grain Production and Soil Improvement. Agron. J. 99: 1297–1305. 23

Teasdale, J. R., and C. L. Mohler. 2000. The quantitative relationship between weed emergence and the physical properties of mulches. Weed Science. 48: 385–392.

Thelen, K. D., D. R. Mutch, and T. E. Martin. 2004. Utility of Interseeded Winter Cereal Rye in Organic Soybean Production Systems. Agronomy Journal. 96: 281– 284.

Tillman, G., H. Schomberg, S. Phatak, B. Mullinix, S. Lachnicht, P. Timper, and D. Olson. 2004. Influence of Cover Crops on Insect Pests and Predators in Conservation Tillage Cotton. Journal of economic entomology. 97: 16.

Uchino, H., K. Iwama, Y. Jitsuyama, K. Ichiyama, E. Sugiura, and T. Yudate. 2011. Stable Characteristics of Cover Crops for Weed Suppression in Organic Farming Systems. Plant Production Science. 14: 75–85.

USDA NASS, U. 2017. USDA National Agricultural Statistics Service Census of Agriculture 2017.

Vaughan, J. D., and G. K. Evanylo. 1998. Corn Response to Cover Crop Species, Spring Desiccation Time, and Residue Management. Agron. J. 90: 536–544.

Wagger, M. G. 1989. Time of Desiccation Effects on Plant Composition and Subsequent Nitrogen Release from Several Winter Annual Cover Crops. Agron. J. 81: 236– 241.

Wayman, S., C. Cogger, C. Benedict, I. Burke, D. Collins, and A. Bary. 2015. The influence of cover crop variety, termination timing and termination method on mulch, weed cover and soil nitrate in reduced-tillage organic systems. Renewable Agriculture and Food Systems. 30: 450–460.

Weston, L. A., and S. O. Duke. 2003. Weed and Crop Allelopathy. Critical Reviews in Plant Sciences. 22: 367–389.

Wischmeier, W. H., and D. D. Smith. 1978. Predicting Rainfall Erosion Losses: A Guide to Conservation Planning. Department of Agriculture, Science and Education Administration.

Zhu, J. C., C. J. Gantzer, S. H. Anderson, E. E. Alberts, and P. R. Beuselinck. 1989. Runoff, Soil, and Dissolved Nutrient Losses from No-Till Soybean with Winter Cover Crops. Soil Science Society of America Journal. 53: 1210–1214.

24

CHAPTER 2

Impact of Cover Crop Species and Termination Date on Arthropod Activity in a

Corn Rotation System

24

25

Introduction

Cover crops have shown many benefits in the agricultural systems, including increasing water infiltration, reduced soil erosion, and an alternative tactic for weed management (Crutchfield et al. 1986, Langdale et al. 1991, Joyce et al. 2002). However, it is unclear how cover crop management strategies can impact the arthropod activity and communities in the agroecosystem. Cover crop adoption has been shown to increase biodiversity in a landscape when used in crop rotation systems (Andow 1991). As a result, we expect that areas with greater diversity of plants will result in a larger number of arthropods (Root 1973), including beneficial arthropods.

Cover crops have the potential to optimize the habitat and environment for beneficial arthropods by providing alternative food sources, such as pollen or nectar, or even refuge (Landis et al. 2000). The addition of cover crops has been shown to increase natural enemies’ abundance; consequently, it has the potential to negatively affect pest populations (Sunderland and Samu 2000, Symondson et al. 2002, Langellotto and Denno

2004, Letourneau et al. 2011). Studies have already reported the positive impacts of cover crops on natural enemy populations and the negative effects on insect pests (Tillman et al. 2004, Koch et al. 2012). Prasifka et al. (2006) observed positive correlations between

European corn borer (Ostrinia nubilalis Hubner; Lepidoptera: Crambidae) and ground beetle (Coleoptera: Carabidae) with an increase of predator abundance and consumption of O. nubilalis in areas with cover crops. Schmidt et al. (2007) reported 45% more natural enemies and a delay in Aphis glycines Matsumura (Hemiptera: Aphididae) establishment in areas with alfalfa as a cover crop. The reduction of pest pressure can be associated with the increase of natural enemies as a result of the cover crop presence; however, pest 26 pressure reduction has been observed even without natural enemies’ enhancement

(Bottenberg et al. 1997). Koch et al. (2012) observed a significant reduction in density of bean leaf beetle (Cerotoma trifurcate Foster; Coleoptera: Chrysomelidae) in rye plots even though predator insect densities did not differ.

The relation between cover crop adoption and its impact on pests and beneficial arthropods in a rotation system is not entirely understood (Cardina and Sparrow 1996,

Landis et al. 2000, Shearin et al. 2008, Dunbar et al. 2017). Differences in arthropods’ response in cover crops are likely, in part, due to differences in cover crop management strategies. Although arthropods are not expected to be considered, growers have the ability to adjust their cover crop system through plant species selection, planting date, and termination method and time; all of which can potentially impact arthropod activity and communities (Hammond 1990, Leslie et al. 2017, Rivers et al. 2017, Carmona et al.

2019).

According to the last agriculture census in the U.S., cover crop acreage increased more than 8% per year from 2013 to 2017 (USDA NASS 2017). The Corn Belt region was responsible for a large part of this increment, with 15.4 million acres planted with cover crops in 2017 (USDA NASS 2017). There was a 109.3% increase of cover crop acres planted in Nebraska from 2012 to 2017 (USDA NASS 2017).

Grasses, legumes, and brassicas represent the most relevant plants used as cover crops. Grasses are commonly used because of their extensive root system and rapid establishment, two factors that are critical for reducing soil erosion (SARE 2017). In addition, grasses can produce large quantities of residues that increase organic matter in the soil and suppress weeds. As a result, a large emphasis has been placed on grass cover 27 crops due to the potential to mitigate important agricultural issues in the Corn Belt region in the U.S.

Past research in cover crops and arthropods has also focused on grass species prior to corn or soybean crops. About 55.3% of the published studies used grass cover crops such as cereal rye (Cereale secale L.), wheat (Triticum aestivum L.), and triticale (x

Triticosecale Wittmack). These three species were reported in 61.5% of field experiments as single species plots (Carmona et al. 2021). This number reflects the importance of these three species in cover crop systems.

Termination methods used in cover crop research have varied over the years and by geographic location. In a conventional cover crop-corn system, most growers (54%) in

Indiana, Illinois, Iowa, and Minnesota terminate cover crops using the chemical method;

33% of the growers opted to terminate cover crops using tillage, and some producers used both methods to terminate cover crops (13%) (Singer 2008). These termination methods reflect published literature, where 42% of the papers reported herbicide applications as cover crop termination method, followed by mower (18%), roller (10%), disk (10%), forage harvest (6%), cut (2%), plow (2%), and tillage (2%) (Carmona et al.

2021).

One of the primary considerations for cover crop management is the termination date prior to planting a cash crop. The USDA Natural Resources Conservation Service

(NRCS) established the guidelines for cover crop termination in U.S. (USDA 2014) that are divided into four cover crop zones for optimal management. Nebraska is divided into two zones; the western counties in zone 2, where cover crops should be terminated at least 15 days before the cash crop planting date. In contrast, eastern Nebraska is classified 28 as zone 3 with cover crop termination recommended at or before planting the following crop (USDA 2014). These guidelines are based on the potential for limited water availability for the following cash crop. Such guidelines do not take into account possible pest risks that cover crops create with delayed termination dates (Carmona et al. 2019).

Based on the literature, most of the cover crop research focuses on one management condition, either a single cover crop species with one to three termination timing or few species with one termination date (Carmona et al. 2021). Focusing on a single management condition is useful for finding a specific answer and can reduce the complexity of a study. However, it limits the ability to understand the complexity of the system.

Historical research on cover crops and arthropods have generally lacked the information necessary to draw any correlation between arthropod activity and cover crop characteristics such as plant height or biomass (Carmona et al. 2021). In addition, arthropod evaluations have focused on single, or few species analyzed as a result of the time and labor those projects require. This project directly addresses these limitations by combining three grass cover crop species and four termination dates that better reflect a combination of management strategies available to growers. Quantifying arthropod presence via pitfall, cover crop metrics, plant injury, and yield will provide a strong foundation to develop the best management practices to reduce the risk of arthropod pests and maximize benefits from cover crop systems.

To determine if cover crop species and termination time can impact arthropod activity in the transition to corn, a field experiment was conducted using cereal rye, wheat, and triticale in combination with four termination dates (-20d, -10d, 0d, and +5d 29 relative to corn planting date). Agronomic data on the cover crops (biomass and extended leaf height) as well as arthropod activity and corn yield to measure the risks or benefits that cover crops can contribute to corn production.

30

Material and Methods

The cover crop field study was conducted over two years at the Eastern Nebraska

Research and Extension Center (ENREC) near Mead, NE, and at the South Central

Agricultural Lab (SCAL) near Clay Center, NE. The experimental design was a split-plot randomized complete block with three or four replications during 2018 and 2019, respectively. The main plot factor was cover crop termination date. Within termination date, cover crops were terminated at four different dates, with the first termination occurring at 20 days before corn planting (-20d), a second at ten days before corn planting (-10d), third at corn planting day (0d), and the last termination at five days after corn planting (+5d).

The split-plot factor was the cover crop species with treatments consisting of three species and a no cover crop plot as a control. We used wheat (Triticum aestivum L.), cereal rye (Secale cereale L.), and triticale (×Triticosecale Wittmack) species planted with a rate of 90 Kg ha -1.

Cover crops were planted in October of 2017 and 2018 at both locations into soybean stubble. During the spring of 2018 and 2019, cover crops were terminated using glyphosate at 2.34 L ha-1 (32oz/acre) + AMS at 140.30 L ha-1 (15 gallons/acre) + water.

Details of corn varieties, planting dates, and harvest dates are presented in Table 1.

Measurements During Cover Crop Growth

Biomass

Before each cover crop termination date, plots were sampled for cover crop biomass and extended leaf height. Two locations for the cover crop biomass samples 31 were randomly selected from an area near the edges at the opposite side of each plot.

Each cover crop biomass sample was collected using a standard PVC rectangle (0.19 m2).

Cover crop plants within the rectangle area were cut at the soil surface and placed in a paper bag. Samples were placed into the dryer for 5-7 days, and the dry weight was measured. The average for each treatment (plot) was then statistically analyzed using a

Linear Mixed Model (PROC GLIMMIX) in SAS 9.4 with a two-way ANOVA treatment design to determine the effect of cover crop species and termination dates, as well as their interaction on cover crop biomass.

Extended Leaf Height

Extended leaf height measures were collected in conjunction with the biomass samples prior to each termination date. Three measurements were taken by randomly stopping on the diagonal path across the plot. A ruler was placed at the soil base, and the leaves were pulled up to measure the maximum length. The average leaf height was calculated for each plot, and the data were analyzed using a Linear Mixed Model (PROC

GLIMMIX) in SAS 9.4 with a two-way ANOVA treatment design to determine the effect of cover crop species and termination dates, as well as their interaction on cover crop extended leaf height.

Measurements During Corn Growth

Arthropod Injury Assessment

Injury assessments from pests were taken at two separate times during the early corn vegetative stages (V3 and V6). During each evaluation, a row directly adjacent to the center two rows was randomly selected. Each assessment area was 4.5 meters in a row, and the evaluation started 1.5 meters from the edge of the plot. Data collected from 32 each row consisted of the number of plants, plant stage, gaps, and injured plants within a row. When a gap was present, seeds or seedlings were dug up to assess any injury.

Arthropods present in the sampled area were collected in each plot and sample time.

Arthropod injury assessments were not analyzed as a result of low pest pressure across sites and years.

Arthropod activity

Arthropod activity was measured using pitfall traps placed in the center of the plot; the traps remained active for approximately four days during the V3, V6, and V10 stage corn. Each pitfall trap consisted of a 1.60 L cup (12.0 cm diameter, 13.8 cm height) with a smaller cup 0.74 L (11.0 cm diameter, 7.8 cm height) inside holding 0.24 L (8 oz) of propylene glycol antifreeze. After five days, the antifreeze was collected using a plastic bag and brought to the laboratory for arthropod identification. The samples were filtered using a thin cloth that retained the arthropods. Water was used to remove any arthropods that were attached to the plastic bag. After the filtration, the arthropods were transferred to a petri dish with alcohol 70%. A stereomicroscope was used to count and identify the arthropods. Arthropods belonging to the Class Insecta were classified to order or family level and the other arthropods were separated into broader groups. All arthropods were stored in alcohol 70% for preservation purposes. The arthropod activity data was normalized to four days of pitfall traps presence in the experiment area. The data were analyzed using the Generalized Linear Mixed Model (PROC GLIMMIX) with negative binomial distribution and a log function in SAS 9.4. Tukey’s adjustment was used on pairwise comparison tests to control for type I error rates. Tukey’s LSD was reported at an 훼 = 0.05 significance level. 33

Corn Yield

Yield data was collected from the two center rows in each plot. The plots were mechanically harvested using a plot combine with the exception of hand harvesting at

ENREC in 2018. Grain yields were corrected to 13% moisture before any statistical analysis was conducted. The data were analyzed using a Linear Mixed Model (PROC

GLIMMIX) in SAS 9.4 with a two-way ANOVA treatment design to determine the effect of cover crop species and termination dates, as well as their interaction on corn yield.

34

Results

After the data analyses were conducted considering year and location as fixed effects, there was significant interaction between year, location, cover crop species, cover crop termination dates. Therefore, each year-site was analyzed separately, considering the split-plot randomized complete block design. The cover crop termination date represents the main plot effect and cover crop species the split-plot effect.

Measurements During Cover Crop Growth

Biomass For ENREC 2018, cover crop biomass was different between termination dates

(F3,6 = 5.56, P-value = 0.0362) (Fig. 2.1A) and cover crop species (F2,16 = 7.51, P-value =

0.0050) (Fig. 2.1B). Greater cover crop biomass was observed in +5d termination date

(386.02 kg ha-1) compared with the -20d (122.29 kg ha-1) and with the -10d (124.99 kg ha-1) termination date, while the 0d (311.27 kg ha-1) cover crop termination date did not differ from any termination date (Fig. 2.1A). Cereal rye had the highest biomass accumulation (331.67 kg ha-1), followed by triticale (205.87 kg ha-1) and wheat (170.88 kg ha-1) (Fig. 2.1B). There was not a significant two-way interaction between cover crop species and termination dates (F6,16 = 1.88, P-value = 0.1464).

For ENREC 2019, a significant interaction occurred between cover crop species and cover crop termination date (F6,24 = 5.55, P-value = 0.0010) (Fig. 2.2) as a result of cereal rye (1105.36 kg ha-1) having greater cover crop biomass at 0d compared to wheat

-1 -1 (818.08 kg ha ; t24 = 4.25, P-value = 0.0008) or triticale (573.20 kg ha ; t24 = 7.87, P- 35 value <.0001) whereas differences were observed only between cereal rye and triticale at

+5d cover crop termination date (t24 = 3.00, P-value = 0.0163).

For SCAL 2018, cover crop biomass differed between termination dates (F3,6 =

36.35, P-value = 0.0003) (Fig. 2.3A) with the greatest cover crop biomass occurring at

+5d (1018.12 kg ha-1) cover crop termination date compared to 0d (403.93 kg ha-1), -10d

(244.59 kg ha-1), and -20d (151.00 kg ha-1) cover crop termination dates. No differences were observed between cover crop species (F2,16 = 0.46, P-value = 0.6413).

For SCAL 2019, a significant interaction between cover crop species and termination date was observed (F6,24 = 3.65, P-value = 0.0102) (Fig. 2.3B). The interaction was caused by a lack of difference between cover crop species at -20d (F2,24 =

0.05, P-value = 0.9538) and -10d (F2,24 = 0.40, P-value = 0.6776) termination dates whereas cereal rye (2919.13 kg ha-1) had a significantly greater cover crop biomass

-1 compared to wheat (2160.25 kg ha ; t24 = 4.14, P-value = 0.0011) at +5d cover crop termination date.

Extended Leaf Height For ENREC 2018, only the cover crop species terminated at 0d and +5d relative to corn planting met the threshold for NRCS guidelines (15.6 cm). A significant interaction between cover crop termination date and cover crop species was identified

(F6,16 = 7.96, P-value = 0.0004) (Fig. 2.4A) as a result of the cover crop extended leaf height being similar between the three cover crop species at the -20d (F2,16 = 1.36, P- value = 0.2847) and -10d (F2,16 = 0.90, P-value = 0.4279) cover crop termination dates, while cereal rye (25.60 cm) had a greater extended leaf height compared to wheat (13.83 36 cm; t16 = 8.45, P-value <.0001) and triticale (4.5 cm; t16 = 7.98, P-value <.0001) at 0d with similar differences between these species at +5d cover crop termination date where cereal rye (28.1 cm) was greater than wheat (9.33 cm; t16 = 6.27, P-value <.0001) and triticale (21.66 cm; t16 = 4.60, P-value = 0.0008).

For ENREC 2019, only the cover crop species terminated at -20d relative to corn planting did not meet the NRCS threshold guidelines (15.6 cm) for cover crop termination. A significant interaction between cover crop species and cover crop termination date (Fig. 2.4B) was observed (F6,24 = 4.18, P-value = 0.0051). The interaction was a result of cereal rye (30.00 cm) having greater extended leaf height compared to triticale (25.38 cm; t24 = 3.84, P-value = 0.0022) whereas cereal rye did not differ from wheat (28.00 cm; t24 = 1.66, P-value = 0.2411) at 0d cover crop termination date. In contrast, cereal rye (35.46 cm) had a greater leaf height relative to triticale (27.16 cm; t24 = 6.88, P-value <.0001) and wheat (27.04 cm; t24 = 6.98, P-value <.0001) at the

+5d cover crop termination date.

For SCAL 2018, all cover crop species terminated at -20d as well as wheat and triticale terminated at -10d relative to corn planting did not meet the NRCS threshold guidelines (15.6 cm) for cover crop termination. A significant interaction between cover crop termination date and cover crop species (Fig. 2.5A) was identified (F6,16 = 4.94, P- value = 0.0049). The interaction was a result of a greater cereal rye (36.77 cm) cover crop extended leaf height at +5d cover crop termination date compared to triticale (30.11 cm; t16 = 5.61, P-value = 0.0001) and wheat (29.77 cm; t16 = 5.89, P-value <.0001) whereas no statistical differences were observed between the cover crop species for any of the 37 other termination dates -20d (F2,16 = 0.09, P-value = 0.9154), -10d (F2,16 = 1.67, P-value

= 0.2201), and 0d (F2,16 = 0.15, P-value = 0.8655).

For SCAL 2019, all cover crop species regardless of termination date relative to corn planting met the NRCS threshold guidelines (15.6 cm) for cover crop termination. A significant interaction between cover crop species and cover crop termination date (Fig.

2.5B) occurred (F6,24 = 15.42, P-value <.0001) as a result of no differences between cover crop species at -20d (F2,24 = 0.36, P-value = 0.6989) and -10d (F2,24 = 2.36, P-value =

0.1159) cover crop termination dates whereas cereal rye (0d: 52.83 cm; +5d: 61.66 cm) had a greater cover crop extended leaf height at 0d termination dates compared to triticale

(39.45 cm; t24 = 7.39, P-value <.0001) and wheat (39.70 cm; t24 = 7.25; P-value <.0001) cover crop species.

Measurements During Corn Growth

Arthropod Activity ENREC 2018

Of the 15 arthropod groups collected in the pitfall samples, a total of 50,522 individual organisms were identified. Of these organisms, six arthropod taxa were found to have at least 1% of the total activity (Collembola: 81.2%, Acari: 9.3%, Diptera: 2.5%,

Coleoptera: 2.3%, and Orthoptera: 1.8%, Araneae: 1.3%) (Table 2.1); therefore, those groups and the total arthropod activity were analyzed.

Coleoptera did not have statistical differences for main effect of cover crop species (F3,24 = 0.73, P-value = 0.5467), termination date (F3,6 = 0.63, P-value = 0.6193), and pitfall sampling period (F2,64 = 1.21, P-value = 0.3035). Two-way interactions were 38 not significant between termination date and cover crop species (F9,24 = 1.57, P-value =

0.1807), cover crop termination date and pitfall sampling period (F6,64 = 1.56, P-value =

0.1747), or cover crop species and pitfall sampling period (F6,64 = 1.61, P-value =

0.1596). No tree-way interaction was observed (F18,64 = 0.60, P-value = 0.8891).

Araneae, Orthoptera, and the total arthropod activity did not have any significant three- or two-way interaction; the only significant main effect was the pitfall sampling period (Table 2.2). Araneae activity (F2,64 = 3.70, P-value = 0.0302) in pitfall samples collected at the V10 corn stage had statistically greater activity followed by V3 and V6 corn stages. Orthoptera (F1,32 = 166.27, P-value <.0001) was only collected in pitfall samples at V6 and V10 corn stage, with V6 having significantly lower activity compared to the V10 corn stage. Total arthropod activity (F2,64 = 214.55, P-value < 0.0001) was greater in pitfall samples collected at the V6 corn stage followed by V6 and V10 corn stages.

Acari activity had a significant two-way interaction between cover crop species and pitfall sampling period (F6,64 = 2.28, P-value = 0.047) (Fig. 2.6). The interaction occurred as a result of no differences between cover crop species in pitfall samples collected at V3 and V6 corn stages whereas Acari activity in wheat (17.81) was greater than no cover crop (8.33; t64 = -2.71, P-value = 0.0415) when pitfall samples were collected at V10 corn stage.

Collembola activity had a significant two-way interaction between cover crop termination date and pitfall sampling period (F6,64 = 2.24, P-value = 0.0506) (Fig. 2.7).

This interaction occurred as a result of no differences between termination dates at the pitfall samples collected at the V3 corn stage whereas Collembola activity at +5d 39

(315.52) was significantly lower compared to the other cover crop termination dates (-

20d: 556.8, t64 = 2.55, P-value = 0.0623; -10d: 514.77, t64 = 2.19, P-value = 0.1358; and

0d: 495.34, t64 = 2.02, P-value = 0.1908) when sampled at the V6 corn stage.

Diptera activity had significant differences in activity for cover crop termination date (F3,6 = 5.01, P-value = 0.0449) (Fig. 2.8A) and pitfall sampling period (F2,64 = 7.02,

P-value = 0.0018) (Fig. 2. 8B). Diptera activity at -10d (5.88) cover crop termination date was significantly lower compared with -20d (9.96) and +5d (9.12) cover crop termination dates, while -10d was not different from the 0d (7.48) cover crop termination date.

Diptera activity was lower for pitfall samples collected at V10 corn stage (6.03) compared to V3 (9.46) and V6 (8.80) corn stages.

ENREC 2019

Of the 49,361 individual organisms collected from pitfall traps, a total of six arthropod taxa groups were identified representing more than 1% of the total activity

(Collembola: 63.2%, Acari: 22.6%, Coleoptera: 5.4%, Diptera: 4.3%, Orthoptera: 1.9%, and Araneae: 1.3%,) (Table 2.1). As a result, these groups and the total arthropod activity were further analyzed.

Coleoptera, Diptera, and Orthoptera activity did not have any significant two- or three-way interactions, the only significant main effect was the pitfall sampling period

(Table 2.3). For Coleoptera (F2,96 = 17.82, P-value <.0001), lower activity was observed in pitfall samples collected at V3 and V6 corn stage when compared to the V10 corn stage. Diptera activity (F2,96 = 2.65, P-value = 0.0756) in pitfall samples collected at the

V3 corn stage had greater activity compared to V10, while no difference was observed between V6 and the other corn stages (V3 and V10). Orthoptera activity (F1,48 = 137.01, 40

P-value <.0001) was only present in pitfall samples collected at V6 and V10 corn stages, with greater activity been observed at V10 compared to V6.

Collembola activity had a significant interaction between cover crop species and pitfall sampling period (F6,96 = 2.53, P-value = 0.0256) (Fig. 2.9). This interaction was a result of no differences between cover crop species in pitfall samples collected at V3

(F3,96 = 1.49, P-value = 0.2215) and V10 (F3,96 = 0.98, P-value = 0.4038) corn stage, whereas the no cover crop (97.20) was significantly lower compared to cereal rye (174.2; t96 = -3.3, P-value = 0.0073) and wheat (167.24; t96 = -3.07, P-value = 0.0146) at V6 corn stage.

Acari activity had a significant interaction between cover crop termination date and pitfall sampling period (F6,96 = 2.77, P-value = 0.0159) (Fig. 2.10). This interaction was caused by a lack of difference between cover crop termination dates in pitfall samples collected at V3 (F3,96 = 0.30, P-value = 0.8247) and V6 (F3,96 = 1.36, P-value =

0.2599) corn stages, whereas Acari activity from 0d (56.05) was significantly greater compared to -20d (32.04; t96 = -2.46; P-value = 0.073) cover crop termination date at V10 corn stage.

For Araneae activity, the interaction between termination date and pitfall sampling period was approaching significance (F6,96 = 2.08, P-value = 0.0623) (Fig.

2.11). Araneae activity at the -20d (4.34) termination date at the V6 corn stage was greater compared to the same treatment (2.55) at the V10 corn stage (t96 = 2.56, P-value =

0.0317). In contrast, all the other cover crop termination dates did not differ significantly from each other at any pitfall sampling periods. 41

For total arthropod activity a significant interaction between termination date and pitfall sampling period (F6,96 = 2.08, P-value = 0.063) (Fig. 2.12). The interaction occurred as a result of no differences between termination dates in pitfall samples collected at V3 (F3,96 = 0.14, P-value = 0.9361) and V6 (F3,96 = 0.89, P-value = 0.4496) corn stage, while the total activity of 0d (392.43) was greater compared to -20d (262.17; t96 = -2.78, P-value = 0.033) termination date in pitfall samples collected at V10 corn stage.

SCAL 2018

Pitfall traps collected total of 38,102 individual organisms of which eight taxa were found to have more than 1% of the total activity (Collembola: 62.4%, Acari: 11.2%,

Coleoptera: 10.6%, Diptera: 8.4%, Hemiptera: 1.2%, Araneae: 2.7%, Orthoptera: 1.8%, and Hymenoptera: 1.1%) (Table 2.1); therefore, those groups and total arthropod activity were analyzed.

Acari, Collembola, Hymenoptera, Hemiptera, and the total activity did not have any significant three- or two-way interaction; the only significant main effect was the pitfall sampling period (Table 2.4). Acari activity (F2,64 = 78.12, P-value <.0001) was greater in pitfall samples collected at the V6 corn stage, followed by V10 and then V3 corn stages. Collembola activity (F2,64 = 6.44, P-value = 0.0028) was significantly greater in pitfall samples collected at the V3 corn stage compared to V6 and V10 corn stages.

Hymenoptera activity (F2,64 = 13.90, P-value <.0001) was greater in pitfall samples collected at V3 compared to the V10 corn stage, while Hymenoptera activity at V6 was not statistically different from V3 and V10 corn stages. Hemiptera activity (F2,64 = 12.76,

P-value <.0001) was greater in pitfall samples collected at the V6 corn stage, followed by 42

V3 and then V10 corn stages. The total arthropod activity (F2,64 = 4.47, P-value = 0.0152) was greater in pitfall samples collected at the V3 corn stage compared to samples at V6 and V10 corn stages.

Araneae activity had a statistically significant interaction between cover crop species and pitfall sampling period (F6,64 = 2.61, P-value = 0.0251) (Fig. 2.13). The interaction was a result of no significant differences between cover crop species in pitfall samples collected at the V3 (F3,64 = 0.97, P-value = 0.4128) and V6 (F3,64 = 0.77, P-value

= 0.5166) corn stage, while the no cover crop (7.99) was greater compared to triticale

(2.84; t64 = 3.46, P-value = 0.0052) and wheat (3.90; t64 = 2.59, P-value = 0.0562) at V10 corn stage.

Orthoptera activity had a significant interaction between cover crop species and cover crop termination date (F9,24 = 2.93, P-value = 0.0172) (Fig. 2.14). This interaction occurred as result of no differences between any of the cover crop species at -20d (F3,24 =

2.53, P-value = 0.0809), -10d (F3,24 = 1.22, P-value = 0.3254), and 0d (F3,24 = 1.27, P- value = 0.3079) termination dates, whereas no cover crop (12.88) had significantly greater Orthoptera activity than triticale (3.25; t24 = 2.93, P-value = 0.0074) at +5d termination date.

Diptera activity had a significant interaction between cover crop species and termination dates (F9,24 = 2.20, P-value = 0.0595) (Fig. 2.15). This interaction was a result of greater Diptera activity on cereal rye (25.55) compared to triticale (15.31; t24 =

2.64, P-value = 0.0644) at -20d cover crop termination date, whereas no differences between cover crop species at -10d (F3,24 = 1.39, P-value = 0.2699) and 0d (F3,24 = 0.99, 43

P-value = 0.4133) termination dates. Differences occurred between wheat (26.98) and triticale (15.25; t24 = -2.96, P-value = 0.0322) also at the +5d termination date.

Coleoptera activity varied by cover crop species (F3,24 = 2.81, P-value = 0.0609)

(Fig. 2.16A) and pitfall sampling period (F2,64 = 20.41, P-value <.0001) (Fig. 2.16B).

Coleoptera activity on wheat (30.34) cover crop species was significantly greater compared to the no cover crop (22.10), while cereal rye (27.28) and triticale (24.17) did not differ from any of the treatments. Coleoptera activity was statistically greater at pitfall samples collected at V10 (34.76), followed by V3 (24.85) and V6 (19.85) corn stages.

SCAL 2019

Of 108,450 individual organisms collected from pitfall traps, eight arthropod taxa were determined to have more than 1% of the total activity (Collembola: 51.5%, Acari:

18.9%, Coleoptera: 15.2%, Diptera: 5.9%, Orthoptera: 3.4%, Araneae: 1.9%,

Hymenoptera: 1.6%, and Hemiptera: 1.3%) (Table 2.1); therefore, those groups and the total arthropod activity were analyzed.

Collembola activity had a significant interaction between termination date and pitfall sampling period (F6,96 = 6.74, P-value <.0001) (Fig. 2.17). The interaction was caused by greater Collembola activity at 0d (737.18) compared with all the other termination dates (-20d: 271.15, t96 = -4.67, P-value <.0001; -10d: 380.93, t96 = -3.08, P- value = 0.0140; +5d: 300.08, t96 = 4.19, P-value = 0.0004) at pitfall samples collected at the V3 corn stage. In contrast, +5d (213.53) did not differ from 0d (192.21; t96 = -0.49, P- value = 0.9614) cover crop termination date at the V6 corn stage. No differences between any cover crop termination dates at pitfall samples collected at the V10 corn stage (F3,96 =

1.59, P-value = 0.1957). 44

Hymenoptera activity had a significant interaction between cover crop termination date and pitfall sampling period (F6,96 = 3.59, P-value = 0.003) (Fig. 2.18).

The interaction occurred as result of no differences between termination dates in pitfall samples collected at V3 (F3,96 = 1.88, P-value = 0.1385), whereas +5d (7.32) was statistically greater compared to -20d (2.28; t96 = -4.04, P-value = 0.0006) and -10d (3.21; t96 = -2.99, P-value = 0.0184) cover crop termination dates in pitfall samples collected at

V6 corn stage. No statistical differences occurred between the four termination dates at

V10 (F3,96 = 1.94, P-value = 0.1289).

Araneae activity showed a significant interaction between cover crop species and termination date (F9,36 = 3.41, P-value = 0.004) (Fig. 2.19). This interaction occurred as a result of no differences between any of the cover crop species at -20d (F3,36 = 0.34, P- value = 0.7932) termination date whereas followed by greater Araneae activity in the no cover crop (13.19) compared to triticale (4.46; t36 = 2.96, P-value = 0.0267) and wheat

(3.65; t36 = 3.45, P-value = 0.0075) in pitfall samples collected at -10d cover crop termination date. In addition, the no cover crop treatment at 0d (4.64) termination date was statistically lower compared to triticale (12.30; t36 = -2.67, P-value = 0.0531) for the same termination date. Lastly, the no cover crop at +5d (4.80) termination date was lower in activity compared to wheat (13.47; t36 = -2.85, P-value = 0.0345).

Coleoptera activity varied between cover crop species and termination date (F6,36

= 4.16, P-value = 0.001) (Fig. 2.20A). This interaction occurred as a result of greater

Coleoptera activity in the no cover crop treatment at the -20d (31.37) and -10d (26.44) termination date whereas the no cover crop treatment had lower Coleoptera activity at the

0d (30.13) and +5d (25.02) compared to the other cover crop species. A significant 45 interaction between cover crop species and pitfall sampling period was also identified

(F6,96 = 3.05, P-value = 0.009) (Fig. 2.20B). The interaction was a result of significant lower Coleoptera activity in the no cover crop treatment (18.46) compared to triticale

(34.82; t96 = -3.22, P-value = 0.0094) and wheat (36.42; t96 = -3.45, P-value = 0.0046) in pitfall samples collected at the V3 corn stage. In contrast, there were no significant differences in Coleoptera activity between cover crop species in pitfall samples collected at the V6 and V10 corn stages. A two-way interaction between termination date and pitfall sampling period was also identified (F6,96 = 5.79, P-value <.0001) (Fig. 2.20C).

This interaction was a result of lower Coleoptera activity for the -20d (V3: 20.71; V6:

6.62) and -10d (V3: 18.64; V6: 6.67) termination date in pitfall samples collected at V3 and V6 corn stages compared to the 0d (V3: 41.63; V6: 15.29) and +5d (V3: 41.23; V6:

26.22) termination dates. Coleoptera activity in pitfall samples collected at the V10 corn stage was greater at +5d (189.56) compared to -10d (77.67; t96 = -3.93, P-value = 0.0009) and 0d (77.67; t96 = -2.97, P-value = 0.0194) termination dates.

Hemiptera activity varied between cover crop species and pitfall sampling period

(F3,48 = 5.52, P-value = 0.0024) (Fig. 2.21A) and termination date and pitfall sampling period (F3,48 = 13.83, P-value <.0001) (Fig. 2.21B). The interaction between cover crop species and pitfall sampling period was a result of lower Hemiptera activity in the no cover crop treatment (1.66) compared to cereal rye (9.78; t48 = -5.4, P-value <.0001), triticale (9.10; t48 = -5.06, P-value <.0001), and wheat (14.37; t48 = -6.69, P-value <.0001) cover crop species in pitfall samples collected at the V3 corn stage whereas no differences occurred between cover crop species in pitfall samples collected at V6 corn stage (F3,48 = 1.27, P-value = 0.2956). The interaction between cover crop termination 46 date and pitfall sampling period was a result of greater Hemiptera activity at the 0d

(26.01) termination date compared to -20d (1.72; t48 = -8.60, P-value <.0001), -10d (6.31; t48 = -5.50, P-value <.0001), and +5d (7.50; t48 = 4.80, P-value <.0001) termination dates in pitfall samples collected at the V3 corn stage, whereas the 0d (2.31) had a lower

Hemiptera activity compared to the +5d (6.56; t48 = -3.46, P-value =0.0061) cover crop termination date at the V6 pitfall sampling period.

Orthoptera activity differed for termination date and pitfall sampling period (F6,96

= 4.26, P-value = 0.0008) (Fig. 2.22A) and between cover crop species and pitfall sampling period (F6,96 = 3.46, P-value = 0.0039) (Fig. 2.22B). The interaction between cover crop termination date and pitfall sampling period occurred as a result of greater

Orthoptera activity in the 0d (7.77) compared to -20d (3.55; t96 = -2.97, P-value = 0.0193) termination date at pitfall samples collected at the V3 corn stage whereas, -20d (2.21) was lower compared to 0d (4.67; t96 = -2.57, P-value = 0.0565) and +5d (7.34; t96 = -4.25,

P-value = 0.0003) in pitfall samples collected at the V6 corn stage. There were no differences between the cover crop termination dates in pitfall samples collected at V10 corn stage. The interaction between cover crop species and pitfall sampling period was a result of lack of differences between cover crop species in pitfall samples collected at the

V3 and V6 corn stage, whereas the no cover crop treatment (34.81) was greater than wheat (21.34; t96 = 2.52, P-value =0.0625) at V10 corn stage.

Acari activity had differed between cover crop species and termination date (F9,36

= 2.33, P-value = 0.0346) (Fig. 2.23A). This interaction occurred as a result of no differences between cover crop species at the -20d, -10d, and 0d cover crop termination dates whereas greater Acari activity occurred in wheat (116.22) compared to the no cover 47 crop treatment (59.72; t36 = -3.04, P-value =0.0216) at the +5d cover crop termination date. Acari activity also varied between cover crop termination date and pitfall sampling period (F6,96 = 4.87, P-value = 0.0002) (Fig. 2.23B). The interaction was mainly caused by a lack of differences between termination dates in pitfall samples collected at V3 (F3,96

= 1.69, P-value = 0.1740). Acari activity at the +5d termination date (108.2) was greater compared to -20d (48.32; t96 = -3.95; P-value = 0.0008) termination date at the V6 corn stage. A similar difference was observed between +5 termination date (78.99) and -20d

(44.63; t96 = -2.79; P-value = 0.0318) in pitfall samples collected at V10 corn stage.

For the Diptera activity, a significant interaction between cover crop species and termination dates was observed (F9,36 = 5.12, P-value = 0.0002) (Fig. 2.24A). The interaction was a result of a lack of difference between cover crop species at the -20d

(F3,36 = 0.85, P-value = 0.4777), -10d (F3,36 = 1.70, P-value = 0.1849), and 0d (F3,36 =

1.23, P-value = 0.3124) termination dates. In contrast, Diptera activity was greater in the wheat (79.40), followed by the triticale cover crop species (38.92) compared to the cereal rye (24.92) and no cover crop treatment (17.08) at the +5d cover crop termination date. In addition, the interaction between cover crop termination date and pitfall sampling period was statistically significant (F6,96 = 3.05, P-value = 0.0089) (Fig. 2.24B). The interaction was mainly caused by a lack of differences between 0d (33.21) and +5d (35.39) termination dates in pitfall samples collected at V3, while +5d (28.05) was statistically greater compared to 0d (12.29; t96 = -3.43; P-value = 0.0049) cover crop termination date with pitfall samples collected at V6 corn stage. No differences occurred between 0d

(27.94) and +5d (39.13) in pitfall samples collected at the V10 corn stage. 48

Total activity varied between cover crop species and cover crop termination date

(F9,36 = 2.62, P-value = 0.0193) (Fig. 2.25A) and between cover crop termination date and pitfall sampling period (F6,96 = 11.25, P-value <.0001) (Fig. 2.25B). The interaction between cover crop species and cover crop termination date was a result of no differences occurring between any cover crop species at the -20d, -10d, and 0d cover crop termination dates whereas the no cover crop treatment (270.89) had a lower total arthropod activity at the +5d compared to cereal rye (484.46; t36 = -2.62; P-value =

0.0587), triticale (534.57; t36 = -3.07; P-value = 0.0204), and wheat (682.26; t36 = -4.17;

P-value = 0.001) cover crop species. The interaction between cover crop termination date and the pitfall sampling period was mainly caused by great total arthropod activity in the

0d (1000.88) termination date compared to the other cover crop termination dates (-

20d:438.78; -10d: 562.8; +5d: 492.98) in pitfall samples collected at V3. In contrast, +5d

(V6: 328.68; V10: 344.23) and 0d (V6: 410.70; V10: 505.41) termination dates did not differ in pitfall samples collected at V6 and V10 corn stages. In addition, +5d (V6:

410.70; V10: 505.41) was significantly greater compared to -10d termination date at V6

(220.33; t96 = -3.87, P-value = 0.0011) and V10 (290.13; t96 = -3.45, P-value = 0.0045) corn stages, while +5d was not different from the other termination dates at V10 corn stage.

Corn Yield For ENREC 2018, the yield varied from 8,693 kg ha-1 (cover crop termination date: 0d; cover crop species: triticale) to 10,428 kg ha-1 (cover crop termination date:+5d; cover crop species: triticale) (Fig. 2.26A). Corn yield did not have a significant two-way 49 interaction between cover crop termination date and cover crop species (F9,24 = 0.91, P- value = 0.532). No differences were observed for termination date (F3,6 = 0.95, P-value =

0.4753) or cover crop species (F3,24 = 0.78, P-value = 0.5171).

For ENREC 2019, the yield varied from 10,926 kg ha-1 (cover crop termination date: +5d; cover crop species: wheat) to 13,875 kg ha-1 (cover crop termination date: -

20d; cover crop species: cereal rye) (Fig. 2.26B). Similar to the previous year, no two- way interaction occurred (F9,36 = 0.74, P-value = 0.6670) and there were no differences for termination date (F3,9 = 0.92, P-value = 0.4688); cover crop species (F3,36 = 1.12, P- value = 0.3540).

For SCAL 2018, corn yield varied from 8,345 kg ha-1 (cover crop termination date: +5d; cover crop species: triticale) to 11,127 kg ha-1 (cover crop termination date: -

10d; cover crop species: triticale) (Fig. 2.27A). Differences were observed between cover crop species (F3,24 = 5.56, P-value = 0.0048) where the no cover crop treatment had greater yield (10,729 kg ha-1) compared to triticale (9,858 kg ha-1) and cereal rye (9,453 kg ha-1), while wheat (10,101.00 kg ha-1) did not statistically differ from any of the cover crop species treatments.

SCAL 2019 had a lower numerical yield than other years and locations due to a hail event (date) that resulted in an early than anticipating corn harvest by about 20 days.

The yield varied from 6,988 kg ha-1 in the +5d termination date for the triticale species to

8,179 kg ha-1 in the -10d termination date for the no cover (Fig. 2.27B). A significant interaction between cover crop species and cover crop termination date was observed

(F9,36 = 3.16, P-value = 0.0066). The interaction was a result of a greater corn yield in

-1 -1 triticale (8,150.23 kg ha ) comparing to no cover crop treatment (7,154.61 kg ha ; t24 = - 50

2.78, P-value = 0.0410) at the -20d cover crop termination date, while the opposite occurred at the +5d cover crop termination date (triticale: 6,988.37 kg ha-1; no cover crop:

-1 7,927.28 kg ha ; t24 = 2.62, P-value = 0.059).

51

Discussion

In this four-year-site study, we expected that the cereal rye would have more cover crop biomass production followed by triticale and wheat, combined with later cover crop termination dates (+5d > 0d > -10d > -20d relative to corn planting date). We hypothesized that treatments with greater cover crop biomass would have more arthropod activity. Moreover, we expected that treatments with more significant cover crop biomass accumulation would create a favorable microhabitat for the arthropod community. The results partially supported our hypothesis, once the year-site with higher biomass accumulation (SCAL 2019; 3200 kg ha-1) had the greater cover crop biomass production with the larger arthropod activity (108,450 arthropods collected).

The results of this study indicate a greater biomass production in treatments late terminated relatively to corn planting (0d and +5d). Throughout the two-year-site field experiment, the 0d and +5d cover crop termination dates had more biomass production when compared to the early two cover crop termination treatments (-20d and -10d relative to corn planting). With the temperature increase in early spring, biomass production can be impacted by the termination date. A similar increment in cover crop biomass production based on termination dates has been observed in other studies. An increase of 39% in cereal rye biomass production has been observed when the cover crop species were terminated two weeks apart (Wagger 1989). Mirsky et al. (2011) observed cover crop biomass enhancement of 37% on average (4,050 up to 10,000 kg ha -1) within a ten-day delay on cover crop termination timing. Even though Wayman et al. (2015) did not observe differences in biomass production between early and late cover crop termination, the authors attributed the absence of differences to the growing degree days 52 variation between the two years of the experiment. Our results agree with Wagger (1989) since it was observed that cover crop species have a different biomass production response by delaying cover crop termination within a few days.

Cereal rye was the cover crop species with the greatest biomass production except at SCAL 2018, which did not have significant differences between cover crop species.

Many studies measured the benefits from cover crop biomass accumulation in areas where cereal rye is grown (Mirsky et al. 2011, Ranaldo et al. 2020). Even though the weed biomass was not explored in this study, it has been reported that the relation between the enhancement of cover crop biomass production can reduce the density and biomass of weed plants (Osipitan et al. 2019, Ranaldo et al. 2020). Cereal rye has also been more efficient in weed suppression when compared with other cover crop species

(Uchino et al. 2011). These results reinforce the importance and potential of using cereal rye as a cover crop to provide agronomic benefits to the corn production system.

The adoption of cover crops has doubled in the past five years (USDA NASS

2017); however, growers are concerned with pest transition from overwinter cover crops to their cash crops (CTIC 2017). Even though some recent studies have reported increased risk in pest pressure when using cover crops (Koch et al. 2012, Dunbar et al.

2016, Carmona et al. 2019), this four year-site field study showed that pest pressure was not significant within the management conditions installed. Despite the cover crop biomass production that varied from 100 kg ha-1 in ENREC 2018 to 3,200 kg ha-1 SCAL

2019, there was no pest pressure observed during the two year study. The most critical moment for pest transition in a cover crop-corn rotation is the early cash-crop season.

The literature reports the possible risk of a wheat stem maggot infestation migrating from 53 the cover crop to the cash crop (Carmona et al. 2019). However, the field conditions explored in this study indicate that cereal rye, triticale, and wheat terminated within the

USDA guidelines can offer benefits of cover crop usage and can be an alternative for growers to increase plant biodiversity in the area.

Besides cover crop biomass variation within treatments, landscape plant diversity is another critical factor to be considered when accounting for arthropod activity. Low pest pressure can be related to the high density and diversity of natural enemies (Schmidt et al. 2007). The enemies hypothesis predicts a greater abundance of predators and parasitoids in more diverse ecosystems. (Root 1973, Andow 1991). Previous studies observed the beneficial impacts that cover crops could improve agricultural systems, enhancing the beneficial arthropod communities (Clark et al. 1993, Schmidt et al. 2007,

Shearin et al. 2008). One fact that could be explored in future studies is the size of the research plots. Due to the high mobility of most ground-dwelling arthropods, treatments could be impacted by the adjacent plots. The larger size of research areas for this type of research should be considered in future studies.

Although it was not determined in this study, there is likely a biomass accumulation threshold that may be necessary to observe significant ecological interactions between cover crops and arthropods. The environment scenario with greater cover crop biomass production (SCAL 2019) showed two-way interactions for all the arthropod taxa analyzed and a more evident potential prey-predator interaction.

Specifically, Araneae activity increased at the later cover crop termination dates. Araneae activity was lower at the no cover treatments compared to other cover crop species at 0d and +5d cover crop termination dates. 54

Similarly, Coleoptera and Acari activity followed the same pattern, presenting greater arthropod activity in the later cover crop termination date (+5d) at cover crop plots compared to the no cover treatment. However, we hypothesized that Acari might prefer the environment with greater cover crop biomass accumulation (+5d) over time. It is important to highlight the potential arthropod mobility between plots. Acari could migrate from early cover crop termination dates (-20d, -10d, 0d) to the +5d termination date after herbicide application to terminate the cover crops occurred.

Out of all the taxa interactions (28), nine arthropod taxa analyzed did not respond to either factor (cover crop termination dates or cover crop species); the activity of those groups was only affected by pitfall sampling dates. Besides that, taxa showing temporal patterns related to pitfall sampling dates have been reported by Dunbar et al. (2017).

Collembola activity varied within the pitfall sampling dates at ENREC 2018, increasing its activity from V3 to V6 corn stage, followed by a considerable reduction in activity at the V10 corn stage. Similar temporal variation of community behavior was observed from Carabidae (O’Rourke et al. 2008, Dunbar et al. 2017) and Gryllidae (Carmona and

Landis 1999, Dunbar et al. 2017).

Corn yield evaluations following cover crops varied between sites and years.

Even though there are reports of corn yield reduction after cereal rye (Singer and Kohler

2005, Singer 2008), yield reduction is not always observed in cover crop areas (Basche et al. 2016). No differences in yield observed at ENREC in 2018 and 2019. However, at

SCAL 2018, corn yield was greater in the no cover plots than cereal rye and triticale cover crop species. At SCAL 2019, the lower corn yields were observed in cereal rye (0d termination date) and triticale (+5d termination date). In contrast, the greatest corn yield 55 was observed in the no cover (-10 termination date) and triticale (-20d termination date); however, it is important to note that a hail event in SCAL on June 14th in 2019, had an impact on corn yield results. The relationship between cover crops and corn yield needs further investigation, but these results should not be the only criteria when growers decide to incorporate or not cover crops. The entomological and agronomic benefits that cover crops can provide to a corn production system should be considered.

In summary, this study explored cover crop species and termination dates to determine the impacts on arthropod activity. There was no increase in pest pressure in areas with cover crops when compared with no cover plots. This result can help growers to make their decision when adding a cover crop in the area. Even at the year-site with the highest biomass production with the greatest arthropod activity, the majority of organisms observed were beneficial arthropods. These results can be used for future research to explore the benefits of cover crop biomass production on arthropod communities and correlate with soil-water availability and weed suppression. 56

References

Andow, D. A. 1991. Vegetational Diversity and Arthropod Population Response. Annu. Rev. Entomol. 36:561-586.

Cardina, J., and D. H. Sparrow. 1996. A Comparison of Methods to Predict Weed Seedling Populations from the Soil Seedbank. Weed Science. 44: 46–51.

Carmona, G. I., L. M. Delserone, J. N. D. Campos, T. Ferreira de Almeida, D. Vieira Branco Ozório, J. David Betancurt Cardona, R. Wright, and A. J. McMechan. 2021. Does Cover Crop Management Affect Arthropods in the Subsequent Corn and Soybean Crops in the United States? A Systematic Review. Annals of the Entomological Society of America. 114 (2), 151-162.

Carmona, G. I., J. Rees, R. Seymour, R. Wright, and A. J. McMechan. 2019. Wheat Stem Maggot (Diptera: Chloropidae): An Emerging Pest of Cover Crop to Corn Transition Systems. Plant Health Progress. 20: 147–154.

Crutchfield, D. A., G. A. Wicks, and O. C. Burnside. 1986. Effect of Winter Wheat (Triticum aestivum) Straw Mulch Level on Weed Control. Weed Science. 34: 110–114.

Dunbar, M. W., A. J. Gassmann, and M. E. O’Neal. 2017. Limited Impact of a Fall- Seeded, Spring-Terminated Rye Cover Crop on Beneficial Arthropods. Environmental Entomology. 46: 284–290.

Hammond, R. B. 1990. Influence of Cover Crops and Tillage on Seedcorn Maggot (Diptera: Anthomyiidae) Populations in Soybeans. Environmental Entomology. 19: 510–514.

Joyce, B. A., W. W. Wallender, J. P. Mitchell, L. M. Huyck, S. R. Temple, P. N. Brostrom, and T. C. Hsiao. 2002. Infiltration and soil water storage under winter cover cropping in california’s sacramento valley. Transactions of the ASAE 45(2) DOI: 10.13031/2013.8526

Landis, D. A., S. D. Wratten, and G. M. Gurr. 2000. Habitat Management to Conserve Natural Enemies of Arthropod Pests in Agriculture. Annu. Rev. Entomol. 45: 175–201.

Langdale, G. W., R. L. Blevins, D. L. Karlen, D. K. McCool, M. A. Nearing, E. L. Skidmore, A. W. Thomas, D. D. Tyler, and J. R. Williams. 1991. Cover crop effects on soil erosion by wind and water. Pp. 15-22. In W.L. Hargrove (editor) Cover Crops for Clean Water, Soil and water Conservation Society, Ankeny, Iowa. 57

Leslie, A. W., K.-H. Wang, S. L. F. Meyer, S. Marahatta, and C. R. R. Hooks. 2017. Influence of cover crops on arthropods, free-living nematodes, and yield in a succeeding no-till soybean crop. Applied Soil Ecology. 117–118: 21–31.

Rivers, A., C. Mullen, J. Wallace, and M. Barbercheck. 2017. Cover crop-based reduced tillage system influences Carabidae (Coleoptera) activity, diversity and trophic group during transition to organic production. Renew. Agric. Food Syst. 32: 538–551.

Root, R. B. 1973. Organization of a Plant-Arthropod Association in Simple and Diverse Habitats: The Fauna of Collards (Brassica Oleracea). Ecological Monographs. 43: 95–124.

Shearin, A. F., S. Chris Reberg-Horton, and E. R. Gallandt. 2008. Cover Crop Effects on the Activity-Density of the Weed Seed Predator Harpalus rufipes (Coleoptera: Carabidae). Weed sci. 56: 442–450.

Singer, J. W. 2008. Corn Belt Assessment of Cover Crop Management and Preferences. Agron. J. 100: 1670–1672.

USDA NASS, 2017. 2017 Census of Agriculture: United States summary and state data. Geographic Area Series. 1.

USDA, N. R. C. Service. 2014. Cover crops. (https://plants.usda.gov/about_cover_crops.html).

58

Tables

Table 2.1 Total arthropod activity groups collected and their percentages of the total per location and year. Percentages in bold represent arthropod taxa that were individually analyzed (> 1% of the total).

59

Table 2.2. Natural log and equivalent mean of Araneae, Orthoptera, and total arthropod activity collected during at V3, V6, and V10 corn stages at ENREC in

2018. Pitfall sampling periods were compared within each arthropod taxa. Different letters within the lines indicate a significant difference at P <0.05.

60

Table 2.3. Natural log and equivalent mean of Coleoptera, Diptera, and Orthoptera activity collected at V3, V6, and V10 corn stages at ENREC in 2019. Different letters within the lines indicate a significant difference at P <0.05.

61

Table 2.4. Natural log and equivalent mean of Acari, Collembola, Diptera,

Hymenoptera, Hemiptera, and total activity collected at V3, V6, and V10 corn stages at SCAL in 2018. Different letters within the lines indicate a significant difference at

P <0.05.

62

Figures

Figure 2.1. Biomass by cover crop termination date relative to corn planting (B) and cover crop species (A) for ENREC 2018. Different letters indicate a significant difference at P <0.05.

63

Figure 2.2. Biomass for each cover crop termination date relative to corn planting and cover crop species for ENREC 2019.

64

Figure 2.3. Cover crop biomass for each termination date relative to corn planting

(A) for SCAL 2018 and cover crop biomass per cover crop termination date relative to corn planting and cover crop species (B) for SCAL 2019. Different letters indicate a significant difference at P <0.05.

65

Figure 2.4. Cover crop extended leaf height for each cover crop termination date relative to corn planting and cover crop species for ENREC 2018 (A) and ENREC

2019 (B). Dash line red indicates cover crop extended leaf height threshold for termination (15.6 cm) according to NRCS guidelines.

66

Figure 2.5. Cover crop extended leaf height per cover crop termination date relative to corn planting and cover crop species for SCAL 2018 (A) and SCAL 2019 (B). Dash line indicates cover crop extended leaf height threshold for termination (15.6 cm) according to NRCS guidelines.

67

Figure 2.6. Natural log of Acari activity collected at pitfall traps per sampling period at V3, V6, and V10 corn stage per cover crop species at ENREC in 2018. Red dash lines indicate the mean equivalent of the natural log scale.

68

Figure 2.7. Natural log of Acari activity collected at pitfall traps per sampling period at V3, V6, and V10 corn stage per cover crop species at ENREC in 2018. Red dash lines indicate the mean equivalent of the natural log scale.

69

Figure 2.8. Natural log of Diptera activity collected at pitfall traps per cover crop termination date relative to corn planting (A) and per sampling period at V3, V6, and

V10 corn stage (B) at ENREC in 2018. Red dash lines indicate the mean equivalent of the natural log scale. Different letters indicate a significant difference at P <0.05.

70

Figure 2.9. Natural log of Collembola activity collected at pitfall traps per sampling period at V3, V6, and V10 corn stage per cover crop species at ENREC in 2019. Red dash lines indicate the mean equivalent of the natural log scale.

71

Figure 2.10. Natural log of Collembola activity collected at pitfall traps per sampling period at V3, V6, and V10 corn stage per cover crop species at ENREC in 2019. Red dash lines indicate the mean equivalent of the natural log scale.

72

Figure 2.11. Natural log of Araneae activity collected at pitfall traps per sampling period at V3, V6, and V10 corn stage per cover crop termination date relative to corn planting at ENREC in 2019. Red dash lines indicate the mean equivalent of the natural log scale.

73

Figure 2.12. Natural log of total activity collected at pitfall traps per sampling period at V3, V6, and V10 corn stage per cover crop termination date relative to corn planting at ENREC in 2019. Red dash lines indicate the mean equivalent of the natural log scale.

74

Figure 2.13. Natural log of Araneae activity collected at pitfall traps per sampling period at V3, V6, and V10 corn stage per cover crop species at SCAL in 2018. Red dash lines indicate the mean equivalent of the natural log scale.

75

Figure 2. 14. Natural log of Orthoptera activity collected at pitfall traps per cover crop termination date relative to corn planting per cover crop species at SCAL in

2018. Red dash lines indicate the mean equivalent of the natural log scale.

76

Figure 2.15. Natural log of Diptera activity collected at pitfall traps per cover crop termination date relative to corn planting per cover crop species at SCAL in 2018.

Red dash lines indicate the mean equivalent of the natural log scale.

77

Figure 2.16. Natural log of Coleoptera activity collected at pitfall traps per cover crop species treatment (A) and per pitfall sampling period at V3, V6, and V10 corn stage

(B) at ENREC in 2018. Red dash lines indicate the mean equivalent of the natural log scale. Different letters indicate a significant difference at P <0.05.

78

Figure 2.17. Natural log of Collembola activity collected at pitfall traps per sampling period at V3, V6, and V10 corn stage per cover crop termination date relative to corn planting at SCAL in 2019. Red dash lines indicate the mean equivalent of the natural log scale.

79

Figure 2.18. Natural log of Hymenoptera activity collected at pitfall traps per sampling period at V3, V6, and V10 corn stage per cover crop termination date relative to corn planting at SCAL in 2019. Red dash lines indicate the mean equivalent of the natural log scale.

80

Figure 2.19. Natural log of Araneae activity collected at pitfall traps per cover crop termination date relative to corn planting per cover crop species at SCAL in 2019.

Red dash lines indicate the mean equivalent of the natural log scale.

81

Figure 2.20. Natural log of Coleoptera activity collected at pitfall traps per cover crop termination date relative to corn planting per cover crop species (A), per pitfall sampling period at V3, V6, and V10 corn stage per cover crop species (B), per pitfall sampling period at V3, V6, and V10 corn stage per cover crop termination date relative to corn planting (C) at SCAL in 2019. Red dash lines indicate the mean equivalent of the natural log scale.

82

Figure 2.21. Natural log of Hemiptera activity collected at pitfall traps per sampling period at V3 and V6 corn stage per cover crop species (A) and per cover crop termination date relative to corn planting (B) at SCAL in 2019. Red dash lines indicate the mean equivalent of the natural log scale.

83

Figure 2.22. Natural log of Orthoptera activity collected at pitfall traps per cover crop termination date relative to corn planting per cover crop species (A) and per pitfall sampling period at V3, V6, and V10 corn stage per cover crop species (B) at SCAL in

2019. Red dash lines indicate the mean equivalent of the natural log scale.

84

Figure 2.23. Natural log of Acari activity collected at pitfall traps per cover crop termination date relative to corn planting per cover crop species (A) and per pitfall sampling period at V3, V6, and V10 corn stage per cover crop termination date relative to corn planting (B) at SCAL in 2019. Red dash lines indicate the mean equivalent of the natural log scale.

85

Figure 2.24. Natural log of Diptera activity collected at pitfall traps per cover crop termination date relative to corn planting per cover crop species (A) and per pitfall sampling period at V3, V6, and V10 corn stage per cover crop termination date relative to corn planting (B) at SCAL in 2019. Red dash lines indicate the mean equivalent of the natural log scale.

86

Figure 2.25. Natural log of total activity collected at pitfall traps per cover crop termination date relative to corn planting per cover crop species (A) and per pitfall sampling period at V3, V6, and V10 corn stage per cover crop termination date relative to corn planting (B) at SCAL in 2019. Red dash lines indicate the mean equivalent of the natural log scale.

87

Figure 2.26. Corn yield per cover crop termination date relative to corn planting and cover crop species for ENREC 2018 (A) and ENREC 2019 (B).

*ns indicates no statistical significance at P <0.05.

88

Figure 2.27. Corn yield per cover crop species for SCAL 2018 (A) and per cover crop termination date relative to corn planting and cover crop species for SCAL 2019 (B).

Different letters indicate a significant difference at P <0.05.