Developing Integrated Pest Management Tactics for Squash Vine Borer

THESIS

Presented in Partial Fulfillment of the Requirements for the Degree Master of Science in the Graduate School of The Ohio State University

Michael Charles McFarland

Graduate Program in Entomology

The Ohio State University

2017

Committee:

Dr. Celeste Welty (advisor)

Dr. Reed Johnson

Dr. Matt Kleinhenz

Copyrighted by

Michael Charles McFarland

2017

Abstract

Squash vine borer (Melittia cucurbitae; Lepidoptera: Sesiidae) is a serious insect pest of squash and pumpkins in the United States and can cause 100% crop loss in gardens and 25% crop loss in commercial crops. The pest can be controlled by frequent applications of insecticide, but growers are seeking control tactics that are more sustainable. Several chemical and non-chemical tactics for managing M. cucurbitae were evaluated for this project.

A field trial was conducted three times to test the use of unharvested zucchini as a trap crop for a cash crop of zucchini. Three factors were compared at each at two levels: harvest status, planting time, and row covers. The infestation rate of M. cucurbitae in earlier plantings was significantly higher than in late plantings. Unharvested plants and row covers had inconsistent effects; infestation was higher in unharvested plants than harvested plants in two of three trials, and infestation was higher in plants started under row covers than no covers in two of three trials. Earlier planted zucchini had higher yields than late plantings, while row covers had no influence on yield.

A field trial was conducted in each of two years to test the effect of delayed planting time and row covers on infestation of M. cucurbitae at a garden scale. All of the garden sites had early and late plantings of zucchini, and half of the gardens used row covers. In both years, zucchini planted earlier had higher infestation rates compared to

ii later plantings, but the differences were statistically significant in only one year.

Zucchini without row covers had higher infestation rates but the differences were not significant either year. Earlier plantings had higher yields than later plantings.

A field trial on chemical control of M. cucurbitae on zucchini evaluated the efficacy of three insecticides applied at various frequencies, in each of two years.

Insecticide applications began after M. cucurbitae adults were consistently caught in a pheromone trap near the field. In both years, the differences among treatments were not significant for either infestation rate or yield.

A laboratory experiment tested the influence of insecticides commonly used for control of M. cucurbitae on two beneficial natural predators: the multicolored Asian lady beetle, Harmonia axyridis (Coleoptera: Coccinellidae), and the insidious flower bug,

Orius insidiosus (Hemiptera: Anthocoridae). Predators were exposed to five common garden insecticides indirectly by enclosure on leaves with fresh residues. Mortality was recorded after 24 and 48 hours. Acetamiprid caused significantly higher mortality than the water control for both H. axyridis and O. insidiosus. Permethrin caused significantly higher mortality compared to the water control for H. axyridis. Spinosad did not cause significantly higher mortality compared to the water control for both H. axyridis and O. insidious.

Planting earlier, using row covers, and leaving the zucchini unharvested could be the key components for a trap crop to draw M. cucurbitae away from a zucchini cash crop. Delaying planting by four weeks reduces the infestation rates of M. cucurbitae but also reduces the yields of the zucchini.

iii

Acknowledgments

I would like to thank my advisor, Dr. Celeste Welty, for all of her time, advice and support. I also would like to thank my advisory committee for their suggestions throughout my project, and Yi Lu for her help with the statistical analysis. I would like to thank Glenn Mills and the Waterman Agricultural and Natural Resources Laboratory crew for their help with harvesting and plot preparation. I would like to thank my collaborators for letting me use their gardens and for their help recording data. I would like to thank Chad Kramer, Brian Mysonhimer, Susan Ndiaye and James Radl for their help collecting data and setting up plots. I would like to thank the Ohio Vegetable and

Small Fruit Research and Development Program for their financial support. I would also like to thank my parents for their support.

Vita

May 2010...... Saline High School

May 2014...... B.S. Horticulture, Michigan State University

2014 to 2016 ...... Graduate Teaching Associate, Center for

...... Life Sciences Education

2016 to present ...... Graduate Teaching Associate, Department

of Entomology, The Ohio State University

Fields of Study

Major Field: Entomology

Table of Contents

Abstract ...... ii

Acknowledgments ...... iv

Vita...... v

List of Figures ...... ix

List of Tables...... xi

Chapter 1: Squash Vine Borer: Introduction and Literature Review...... 1

1.1 Introduction...... 1

1.2 Background...... 1

1.2.1 Range and Hosts ...... 1

1.2.2 Life cycle ...... 2

1.2.3 Monitoring ...... 3

1.2.4 Chemical control...... 3

1.2.5 Biological control...... 4

1.2.6 Compatibility of biological control and chemical control ...... 5

1.2.7 Compatibility of chemical control to pollinators ...... 6

1.2.8 Mechanical control...... 7

1.2.9 Cultural control...... 8

1.3 Rationale and significance ...... 10

1.4 References ...... 12 vi

Chapter 2: Evaluating factors affecting zucchini as a trap crop for squash vine borer...... 16

2.1 Introduction ...... 16

2.2 Materials and Methods ...... 18

2.3 Results ...... 20

2.4 Discussion...... 22

2.5 References ...... 25

2.6 Figures ...... 27

2.7 Tables...... 31

Chapter 3: Delayed planting for squash vine borer management in home garden squash...... 33

3.1 Introduction ...... 33

3.2 Materials and Methods ...... 35

3.3 Results ...... 38

3.4 Discussion...... 39

3.5 References ...... 41

3.6 Figures ...... 43

3.7 Tables...... 47

Chapter 4: Intensity of insecticide spray schedules as a factor in control of squash vine borer……………………………………………………………………………...48

4.1 Introduction ...... 48

4.2 Materials and Methods ...... 51

4.3 Results ...... 53

4.4 Discussion...... 54 vii

4.5 References ...... 57

4.6 Figures ...... 59

4.7 Tables...... 61

Chapter 5: Susceptibility of natural enemies to insecticides used in home garden plantings of cucurbit crops ...... 64

5.1 Introduction ...... 64

5.2 Materials and Methods ...... 66

5.3 Results ...... 68

5.4 Discussion...... 69

5.5 References ...... 71

5.6 Tables...... 74

Bibliography...... 76

viii

List of Figures

Figure 1: Infestation rates of squash vine borer in early and late plantings of zucchini...27

Figure 2: Infestation rates of squash vine borer for zucchini with row covers (RC) and without row covers (NoRC)……………………………………………………………...28

Figure 3: Infestation rates of squash vine borer for zucchini plants that were harvested…………………………………………………………………………………29

Figure 4: The number of SVB adults caught in the pheromone traps at Waterman Farm in 2015 and 2016; mean of three traps…………………………………………………...30

Figure 5: The mean infestation rates of squash vine borer in zucchini for each treatment separately and combined (2015)…………………………………………………………43

Figure 6: The mean infestation rates of squash vine borer in zucchini for each treatment separately and combined (2016)…………………………………………………………44

Figure 7: The mean yield per zucchini plant over the entire season for each treatment separately and combined (2015)…………………………………………………………45

Figure 8: The mean yield per zucchini plant over the entire season for each treatment separately and combined…………………………………………………………………46

Figure 9: The mean number of squash vine borer adults caught in three pheromone traps at Waterman Farm, Columbus, Ohio, in 2015…………………………………………..59

Figure 10: The mean number of squash vine borer adults caught in three pheromone traps at Waterman Farm, Columbus, Ohio, in 2016……………………………………..60

List of Tables

Table 1: Yield per zucchini plant for the entire season for each treatment that was harvested for planting time………………………………………………………………31

Table 2: Yield per zucchini plant for the entire season for each treatment that was harvested for row covers vs. no row covers……………………………………………...32

Table 3: The mean infestation rates and the yield over the entire season for zucchini with a early trap-crop plant and zucchini without an early trap-crop plant…………………...47

Table 4: The average infestation rates of squash vine borer for each treatment in 2015 and 2016………………….………………………………………………………………61

Table 5: The average yield per plant in number of zucchini over the entire season for each treatment in 2015 and 2016, Columbus, Ohio……………………………………...62

Table 6: The average yield per plant in kg for the entire season for each treatment in

2015 and 2016……………………………………………………………………………63

Table 7: The average mortality rates of multicolored Asian lady beetle after 24 and 48 hours for the direct and indirect exposure and indirect exposure bioassays……………..74

Table 8: The average mortality rates of O. insidiosus after 24 hours for the direct bioassay…………………………………………………………………………………..75

Chapter 1: Squash Vine Borer: Introduction and Literature

Review

1.1 Introduction

Squashes are some of the most popular vegetables grown in home gardens and on commercial vegetable farms, but squash plants are often killed by the squash vine borer

(SVB), Melittia cucurbitae (Lepidoptera: Sesiidae) before they have reached their yield potential. As a key pest of squash and pumpkins, SVB causes up to 100% crop loss in home gardens and 25% crop loss in commercial fields (Pearson, 1995). To reduce the amount of damage by SVB, gardeners and commercial growers use various management tactics such as row covers, delayed planting, and insecticide applications, although most of these methods have not been thoroughly tested and compared.

1.2 Background

1.2.1 Range and Hosts

SVB is a pest found in the eastern United States, southeastern Canada, Mexico, and recently Brazil (Becker & Eichlin, 1984; Klun, Schwarz, Leonhardt, & Cantelo,

1990; Krinski, 2015). It targets the cucurbit species Cucurbita maxima (Hubbard squash, buttercup squash, and giant pumpkins) and Cucurbita pepo (summer squash, zucchini,

1 acorn squash, and common pumpkins) (Howe & Rhodes, 1973). Other cucurbits such as

Cucurbita moschata (butternut squash) are not very susceptible to SVB, most likely due to stem toughness (Howe & Rhodes, 1973).

1.2.2 Life cycle

As with all insects that develop by complete metamorphosis, the life cycle of SVB has egg, larval, pupal and adult stages. Winter is spent as a pupa in the soil. Around the middle of June in Connecticut, the SVB starts to emerge from the soil as an adult (Friend,

1931). Adult males live for an average of three days after emerging, while female adults live for an average of four days (Canhilal, Carner, Griffin, Jackson, & Alverson, 2006).

The adults mate, and females lay eggs at the base of main stem and leaf stalks of cucurbit plants (Friend, 1931). Each female can lay between 150 to 200 eggs per season (Friend,

1931). Eggs take 7-11 days to hatch, and the young larvae then burrow into the stem of the plant (Canhilal et al., 2006). From a management perspective, the first-instar larva is the most important part of the life cycle because insecticides will kill larvae only during the short time that young larvae are on the outside of the stem. Once larvae are inside the stem, applications of contact insecticide will no longer affect them. Larvae stay inside the plant for four to six weeks, feeding on the stem tissue. If the host dies during this time, larvae can move to a different plant (Friend, 1931). After the larval stage is complete, the larva exits the plant, burrows into the soil, and forms a pupa (Friend, 1931).

The number of generations per year depends on location. In the northern U.S, there is only one generation per year, while in southern U.S, there are two generations per year

(Canhilal et al., 2006; Friend, 1931). 2

1.2.3 Monitoring

To properly manage SVB, growers need to know when adults are emerging so that management tactics can be used at the best time. SVB can be monitored in traps baited with synthetic female sex pheromone that attracts males, which allows the grower to estimate the SVB population size over time (Pearson, 1995). The most effective pheromone trap for monitoring SVB is a conical mesh trap (Jackson, Canhilal, & Carner,

2005). Monitoring the plants by scouting for entry holes and frass on the outside of the lower stem can reveal initial damage by SVB, but can underestimate damage when holes are on the underside of the stem that is difficult or impossible to observe without damaging the plant (Hahn & Burkness, 2007). In one study, researchers looked for adults resting under leaves instead of holes in the stems because they were trying for early detection, to prevent larvae from getting into the stem as opposed to simply seeing if the plants are infested or not (Brust, 2010). Some symptoms of SVB infestation are similar to those of bacterial wilt of cucurbits and cucurbit yellow vine disease, which can lead to incorrect diagnoses and subsequent treatment of the crops.

1.2.4 Chemical control

One of the most common forms of control for SVB is to use insecticides before the larva can bore into the plant (Brust, 2010). Spraying weekly for six weeks after SVB adults begin to emerge is a schedule that is sometimes used for SVB control (Brust,

2010). However, the optimal timing and number of sprays is uncertain, and spraying six times might lead to overuse of insecticide and a negative impact on the environment. By

3 scouting for adult females under leaves and using pheromone traps, the number of insecticide applications can be reduced by 50% (Brust, 2010).

Several insecticidal chemicals are used to control SVB. Researchers found that bifenthrin plus zeta-cypermethrin (Hero 1.24EC), endosulfan (Thionex 3EC), carbaryl

(Sevin XLR) all resulted in significantly lower infestations of squash vine borer compared to untreated zucchini using four applications (Welty & Jasinski, 2008).

Researchers have found that there was a significantly lower infestation rate of SVB when using spinosad (Entrust 80 WP) compared to an untreated control in 2012 and 2013 but not in 2014 (Seaman, Lange, Luton, & Shelton, 2012; Seaman, Lange, & Shelton, 2013,

2014).

1.2.5 Biological control

Squash vine borer is susceptible to an egg parasitoid (Telenomus sp.,

Hymenoptera: Platygastridae), and the adults are occasionally preyed upon by robber flies (Diptera: Asilidae), but the larva is not known to be affected by natural enemies

(Friend, 1931). The impact of these natural enemies on squash vine borer populations is unknown. One of the few cases of documented biological control was with entomopathogenic nematodes. When Steinernematid nematodes were applied to the stem and soil, the infestation rates were significantly lower in two of three trials compared to the untreated check (Canhilal & Carner, 2006).

There are natural enemies that attack other common pests of cucurbits such as the striped cucumber beetle (Acalymma vittatum, Coleoptera: Chrysomlidae) and the squash bug (Anasa tristis, Hemiptera: Coreidae). Cucumber beetle is attacked by Celatoria 4 setosa (Diptera: Tachinidae), and squash bug is attacked by Trichopoda pennipes

(Diptera: Tachinidae) and two egg parasitoids: Gryon pennsylvanicum (Hymenoptera:

Platygastridae) and Ooencyrtus anasae (Hymenoptera: Encyrtidae) (Olson & Nechols,

1995; Smyth & Hoffmann, 2010; Tracy & Nechols, 1987; Worthley, 1924). In addition to these specialist natural enemies, generalist predators such as lady beetles (Coleoptera:

Coccinellidae) are often found in cucurbit plantings (Kim, Kim, & Kim, 2008). Other generalists such as green lacewings (Neuroptera: Chrysopidae), brown lacewings

(Neuroptera: Hemerobiidae), hover flies (Diptera: Syrphidae), pirate bugs (Hemiptera:

Anthocoridae), ground beetles (Coleoptera: Carabidae), and wolf spiders (Araneae:

Lycosidae) are occasionally found in cucurbits (Molly Dieterich Mabin, personal communication).

1.2.6 Compatibility of biological control and chemical control

The impact of some insecticides on some natural enemies has been documented in some crop systems. For parasitoids such as braconids, the adult female mortality rate after 24 hours was increased after being released in a glass vial treated with the insecticides acetamiprid and permethrin (Toshiharu & Minakuchi, 2012).

One of the most common generalist natural enemies is the multi-colored Asian lady beetle (MALB), Harmonia axyridis (Coleoptera: Coccinellidae). MALB is susceptible to several insecticides such as acetamiprid, for all life stages; imidacloprid, for eggs and larvae; and etofenprox, for eggs and larvae (Youn, Seo, Shin, Jang, & Yu,

2003). Other insecticides such as spinosad do not lead to immediate mortality, but can reduce the survival of the first instar larva, prolong the development time, and decrease 5 the fertility of female MALB (Galvan, Koch, & Hutchison, 2005).

In the case of another generalist, the insidious flower bug (Orius insidiosus,

Hemiptera: Anthocoridae), the effects of insecticides have varied based on the active ingredient and application method tested. In one study, the mortality rates of O. insidiosus when fed eggs treated with spinosad were 47.8% for males and 54.6% for females, compared to controls that had less than 10% mortality rates (Elzen, 2001).

However, O. insidiosus treated with spinosad had significantly higher fecundity rates compared to the control (Elzen, 2001). O. insidiosus that were treated with spinosad or imidacloprid had significantly higher mortality rates in Petri dish bioassays than they did in caged field plots and caged greenhouse plants (Studebaker & Kring, 2003). Spinosad was not considered to be toxic in the field and greenhouse setting, while imidacloprid was moderately toxic in the same settings; both were considered extremely toxic in Petri dish bioassays (Studebaker & Kring, 2003).

1.2.7 Compatibility of chemical control to pollinators

Chemical control can also impact the health of pollinators, but this varies widely for different insecticides and on the time of day that insecticide is applied. Permethrin had a higher toxicity than azinphosmethyl, carbaryl, and methyl parathion, when honey bees were treated directly (Danka, Rinderer, Hellmich, & Collins, 1986). In addition to having a high toxicity, a sub-lethal dose of permethrin, when applied directly, can alter honey bee behavior compared to bees that were untreated (Cox & Wilson, 1984).

However permethrin can be applied to fields safely without harming bees, depending upon the time of day that the insecticide is applied (Pike, Mayer, Glazer, & Kious, 1982). 6

When permethrin was applied at 5:30-7:30 AM in sweet corn throughout the season, the die off rates for the bees remained normal, although the permethrin did repel most honey bees from the fields (Pike et al., 1982). Spinosad is another insecticide that can be harmful to bees. When compared to chlorfluazuron and oxymatrine, spinosad has the lowest LD50 value of the three when the insecticide is ingested orally (Rabea, Nasr, &

Badawy, 2010). In another study, spinosad had lower LD50 values than lambda- cyhalothrin and Bacillus thuringiensis when applied directly to the bee (Bailey, Scott-

Dupree, Harris, Tolman, & Harris, 2005). However it is important to note that in the same study, bees that were exposed to residual contact with spinosad did not have increased mortality compared to the control (Bailey et al., 2005; Miles, 2003). To avoid killing pollinators with insecticide, spraying in the evening is advised because that is when the pollinators are not active in fields, which prevents the pollinators from being directly exposed to insecticides (Hooven, Sagilli, & Johansen, 2013).

1.2.8 Mechanical control

Some gardeners and commercial growers consider chemical control to be undesirable, especially among those who prefer an organic approach, thus mechanical control is sometimes used for SVB management. Some gardeners will cut open an infested plant and remove the SVB larva manually (Britton, 1919). However, this can be time consuming and impractical on large farms. Another way that gardeners control SVB is to wrap the base of plants with tape or plastic to prevent the SVB female from laying eggs on the stems (Capinera, 2001). While wrapping might not be as time consuming or as damaging to the plant compared to manual larva removal, wrapping is practical only 7 on a small scale because it is labor intensive.

Row covers can be used by both gardeners and commercial growers to exclude pests. A row cover is a lightweight cloth that is installed over the plants and allows sunlight and water to pass through, but excludes pests. For a row cover to be effective, it needs to be deployed before the insect can infest the plants, and needs to be removed once female flowers appear, to allow bees to pollinate the flowers. For effective SVB management, row covers should be deployed before SVB adult emergence in June to prevent the adults from laying eggs on the squash plants. Although there is no published report on use of row covers for SVB control, row covers have been effective for controlling other cucurbit pests. Row covers have been shown to reduce the amount of damage to zucchini caused by silverleaf whitefly (Bemisia tabaci) (Qureshi, Midmore,

Syeda, & Playford, 2007). The use of row covers reduced the densities of whitefly and aphid in zucchini when compared to the untreated control (Costa, Johnson, & Ullman,

1994). Row covers also produced higher zucchini yields when compared to insecticide alone, under high pest pressure from silverleaf whiteflies (Qureshi et al., 2007). Row covers increased the yields of cucumbers compared to bare soil in a study done in Mexico

(Ibarra-Jiménez, Quezada-Martin, & de la Rosa-Ibarra, 2004).

1.2.9 Cultural control

Altered planting time and trap cropping are cultural tactics to potentially control

SVB. If a grower delays the planting of cucurbit crops for several weeks, it might reduce

SVB infestation, because SVB adults prefer to lay their eggs on larger, more mature plants and the adults might leave the area if the host plants are not large enough (Hahn & 8

Burkness, 2007). Late plantings could also be used in conjunction with an early planting; in this scenario, the early planting would act as a trap crop, which is an adjacent crop that is more attractive than the main crop. It is recommended that trap crops are used on about 10% of the total crop area (McPherson & Newsom, 1984; Shelton & Badenes-

Perez, 2006). A trap crop can be a different species of crop than the main planting, or it can be the same crop used in a more appealing way. One example is Blue Hubbard squash used as a trap crop with the main crop of butternut squash, for management of striped cucumber beetle (Adler & Hazzard, 2009). Using a trap crop such as Hubbard squash has reduced the use of insecticides by up to 94% for striped cucumber beetle in

Massachusetts (Cavanagh, Hazzard, Adler, & Boucher, 2009). In most cases, the trap crop is planted a few weeks before the main crop (Hokkanen, 1991). A trap crop can be deployed along the perimeter or in strips within the main crop (Boucher, Ashley, Durgy,

Sciabarrasi, & Calderwood, 2003).

For this project, we evaluated unharvested zucchini as a trap crop, based on the results reported by Welty and Jasinski (2008), for a trial in which insecticides were evaluated to determine which were most effective at reducing SVB infestation. The trial in 2008 was done twice: once in a field that did not have any of the zucchini fruit harvested, and once in an adjacent field that was harvested twice per week. Although the

SVB population in both fields showed similar trends in response to insecticides, there was a large difference in infestation rate by SVB. The unharvested zucchini plants had

53% infestation in untreated control plots versus 15% infestation in untreated control plots in the harvested field. These results indicate that the SVB were more attracted to

9 the zucchini plants that were unharvested, which makes us propose that unharvested zucchini plants could potentially be used as a trap crop for a cash crop of harvested zucchini or other cucurbits.

1.3 Rationale and significance

Despite the long history of SVB being one of the most destructive garden pests, there is a lack of published research on integrated pest management techniques, particularly in a garden setting. The goal of this project was to evaluate and compare several SVB management tactics, both individually and in combination. Gardeners and commercial growers need detailed information on chemical and non-chemical approaches to managing SVB, and information on how to integrate multiple tactics into their pest management strategy. Growers will benefit from comparative data for several management options, particularly the timing of chemical and mechanical control tactics.

The information generated by this project will help growers with their decisions about choosing the most effective and appropriate tactics to use for control of SVB, while causing minimal negative effects on beneficial insects and the surrounding environment.

Controlling the SVB by integrated multiple tactics is supported by recent public interest in improved food security by reducing the yield loss of zucchini and other squash crops.

This project had four objectives.

Objective 1: To test the relative effects of unharvested zucchini, row covers, and planting time on the infestation rates of SVB.

Hypothesis 1. Unharvested zucchini plants will be more attractive to SVB than

zucchini plants harvested on a regular basis, and thus will act as a trap crop. 10

Hypothesis 2. Early planted zucchini will be more attractive to SVB than late-

planted zucchini and thus will act as a trap crop.

Hypothesis 3. Zucchini started under row covers will grow larger and thus be

more attractive to SVB once row covers are removed, compared to zucchini

grown without row covers.

Hypothesis 4. The most effective combination of factors for a trap crop will be

early planted zucchini that is started under row covers and left unharvested.

Objective 2: Evaluate delayed planting dates, with and without the use of row covers, to reduce the infestation rates of SVB in home gardens.

Hypothesis 1. Planting later will reduce the infestation rates compared to planting

early.

Hypothesis 2. The adjusted planting date will have a greater effect than row

covers.

Objective 3: Determine the optimal number of insecticide sprays needed to control SVB in commercial fields, when using a botanical insecticide that has less persistence than a conventional synthetic insecticide.

Hypothesis. Using four applications of botanical insecticide will control SVB as

effectively as six applications, but two applications will be inadequate.

Objective 4: Assess how insecticides that are commonly used to control SVB can affect natural enemies found in cucurbit fields.

Hypothesis. Some insecticides will negatively affect some natural enemies and

others will not.

1.4 References

Adler, L., & Hazzard, R. (2009). Comparison of perimeter trap crop varieties: effects on herbivory, pollination, and yield in butternut squash. Environmental Entomology, 38(1), 207-215.

Bailey, J., Scott-Dupree, C., Harris, R., Tolman, J., & Harris, B. (2005). Contact and oral toxicity to honey bees (Apis mellifera) of agents registered for use for sweet corn insect control in Ontario, Canada. Apidologie, 36(4), 623-633.

Becker, V., & Eichlin, T. (1984). Correct name for the neotropical squash-vine borer (Sesiidae: Melittia)[Central America, South America]. Journal of the Lepidopterists' Society, 38(1), 13-14.

Boucher, T. J., Ashley, R., Durgy, R., Sciabarrasi, M., & Calderwood, W. (2003). Managing the pepper maggot (Diptera: Tephritidae) using perimeter trap cropping. Journal of Economic Entomology, 96(2), 420-432.

Britton, W. E. (1919). Insects attacking squash, cucumber and allied plants in Connecticut. Connecticut Agricultural Experiment Station, Bulletin 216, 39-42.

Brust, G. E. (2010). Squash vine borer (Lepidoptera: Sesiidae) management in pumpkin in the mid-Atlantic. Journal of Applied Entomology, 134(9-10), 781-788.

Canhilal, R., & Carner, G. R. (2006). Efficacy of entomopathogenic nematodes (Rhabditida: Steinernematidae and Heterorhabditidae) against the squash vine borer, Melittia cucurbitae (Lepidoptera: Sesiidae) in South Carolina. Journal of Agricultural and Urban Entomology, 23(1), 27-39.

Canhilal, R., Carner, G. R., Griffin, R. P., Jackson, D. M., & Alverson, D. R. (2006). Life history of the squash vine borer, Melittia cucurbitae. Journal of Agricultural and Urban Entomology, 23(1), 1-6.

Capinera, J. (2001). Handbook of vegetable pests: Gulf Professional Publishing.

Cavanagh, A., Hazzard, R., Adler, L., & Boucher, J. (2009). Using trap crops for control of Acalymma vittatum (Coleoptera: Chrysomelidae) reduces insecticide use in butternut squash. Journal of Economic Entomology, 102(3), 1101-1107.

Costa, H. S., Johnson, M. W., & Ullman, D. E. (1994). Row covers effect on sweetpotato whitefly (Homoptera: Aleyrodidae) densities, incidence of silverleaf, and crop yield in zucchini. Journal of Economic Entomology, 87(6), 1616-1621.

Cox, R. L., & Wilson, W. T. (1984). Effects of permethrin on the behavior of individually tagged honey bees, Apis mellifera L.(Hymenoptera: Apidae). Environmental Entomology, 13(2), 375-378.

Danka, R. G., Rinderer, T. E., Hellmich, R. L., & Collins, A. M. (1986). Comparative toxicities of four topically applied insecticides to Africanized and European honey bees (Hymenoptera: Apidae). Journal of Economic Entomology, 79(1), 18-21.

Elzen, G. (2001). Lethal and sublethal effects of insecticide residues on Orius insidiosus (Hemiptera: Anthocoridae) and Geocoris punctipes (Hemiptera: Lygaeidae). Journal of Economic Entomology, 94(1), 55-59.

Friend, R. (1931). The squash vine borer. Connecticut Agricultural Experiment Station, Bulletin 328, 588-607.

Galvan, T., Koch, R., & Hutchison, W. (2005). Effects of spinosad and indoxacarb on survival, development, and reproduction of the multicolored Asian lady beetle (Coleoptera: Coccinellidae). Biological Control, 34(1), 108-114.

Hahn, J., & Burkness, S. (2007). Squash vine borer management in home gardens. University of Minnesota. Retrieved from http://www.extension.umn.edu/garden/insects/find/squash-vine-borers/

Hokkanen, H. M. (1991). Trap cropping in pest management. Annual Review of Entomology, 36(1), 119-138.

Hooven, L., Sagilli, R., & Johansen, E. (2013). How to reduce bee poisoning from pesticides. Oregon State University. Retrieved from https://catalog.extension.oregonstate.edu/sites/catalog/files/project/pdf/pnw591_1. pdf

Howe, W., & Rhodes, A. (1973). Host relationships of the squash vine borer, Melittia cucurbitae with species of Cucurbita. Annals of the Entomological Society of America, 66(2), 266-269.

Ibarra-Jiménez, L., Quezada-Martin, M., & de la Rosa-Ibarra, M. (2004). The effect of plastic mulch and row covers on the growth and physiology of cucumber. Animal Production Science, 44(1), 91-94.

Jackson, D. M., Canhilal, R., & Carner, G. R. (2005). Trap monitoring squash vine borers in cucurbits1, 2. Journal of Agricultural and Urban Entomology, 22(1), 27-39.

Kim, Y. H., Kim, H. Y., & Kim, J. H. (2008). Occurrence of cotton aphids (Aphis gossypii) and lady beetles (Harmonia axyridis) on Hibiscus syriacus Linne: Are the aphids a pest of cucurbits? Entomological Research, 38(3), 211-215.

Klun, J., Schwarz, M., Leonhardt, B., & Cantelo, W. (1990). Sex pheromone of the female squash vine borer (Lepidoptera: Sesiidae). Journal of Entomological Science, 25(1), 64-72.

Krinski, D. (2015). First report of squash vine borer, Melittia cucurbitae (Harris, 1828)(Lepidoptera, Sessidae) in Brazil and South America: distribution extension and geographic distribution map. Check List, 11(3), 1625.

McPherson, R., & Newsom, L. (1984). Trap crops for control of stink bugs (Hemiptera, Pentatomidae) in soybean. Journal of the Georgia Entomological Society, 19(4), 470-480.

Miles, M. (2003). The effects of spinosad, a naturally derived insect control agent to the honeybee. Bulletin of Insectology, 56, 119-124.

Olson, D., & Nechols, J. (1995). Effects of squash leaf trichome exudates and honey on adult feeding, survival, and fecundity of the squash bug (Heteroptera: Coreidae) egg parasitoid Gryon pennsylvanicum (Hymenoptera: Scelionidae). Environmental Entomology, 24(2), 454-458.

Pearson, G. (1995). Sesiid pheromone increases squash vine borer (Lepidoptera: Sesiidae) infestation. Environmental Entomology, 24(6), 1627-1632.

Pike, K., Mayer, D., Glazer, M., & Kious, C. (1982). Effects of permethrin on mortality and foraging behavior of honey bees in sweet corn. Environmental Entomology, 11(4), 951-953.

Qureshi, M. S., Midmore, D. J., Syeda, S. S., & Playford, C. L. (2007). Floating row covers and pyriproxyfen help control silverleaf whitefly Bemisia tabaci (Gennadius) Biotype B (Homoptera: Aleyrodidae) in zucchini. Australian Journal of Entomology, 46(4), 313-319.

Rabea, E. I., Nasr, H. M., & Badawy, M. E. (2010). Toxic effect and biochemical study of chlorfluazuron, oxymatrine, and spinosad on honey bees (Apis mellifera). Archives of Environmental Contamination and Toxicology, 58(3), 722-732.

Seaman, A. J., Lange, H., Luton, B., & Shelton, A. M. (2012). Squash vine borer control with insecticides allowed for organic production, 2011. Arthropod Management Tests, 37(1), E81.

Seaman, A. J., Lange, H., & Shelton, A. M. (2013). Squash vine borer control with insecticides allowed for organic production, 2012. Arthropod Management Tests, 38(1), E56.

Seaman, A. J., Lange, H., & Shelton, A. M. (2014). Squash vine borer control with insecticides allowed for organic production, 2013. Arthropod Management Tests, 39(1), E65.

Shelton, A., & Badenes-Perez, F. (2006). Concepts and applications of trap cropping in pest management. Annual Review of Entomology, 51, 285-308.

Smyth, R. R., & Hoffmann, M. P. (2010). Seasonal incidence of two co-occurring adult parasitoids of Acalymma vittatum in New York State: Centistes (Syrrhizus) diabroticae and Celatoria setosa. BioControl, 55(2), 219-228.

Studebaker, G. E., & Kring, T. J. (2003). Effects of insecticides on Orius insidiosus (Hemiptera: Anthocoridae), measured by field, greenhouse and petri dish bioassays. Florida Entomologist, 86(2), 178-185.

Toshiharu, T., & Minakuchi, C. (2012). Insecticides and Parasitoids, Insecticides - Advances in Integrated Pest Management. InTech, 115-141

Tracy, J., & Nechols, J. R. (1987). Comparisons between the squash bug egg parasitoids Ooencyrtus anasae and O. sp.(Hymenoptera: Encyrtidae): development, survival, and sex ratio in relation to temperature. Environmental Entomology, 16(6), 1324- 1329.

Welty, C., & Jasinski, J. (2008). Squash vine borer control on zucchini in Ohio. Ohio State University. Retrieved from http://entomology.osu.edu/welty/pdf/OhioZucchini2008_FinalReport.pdf

Worthley, H. (1924). The biology of Trichopoda Pennipes Fab (Diptera, Tachinidae), a Parasite of the Common Squash Bug. Psyche, 31, 57-77.

Youn, Y.-N., Seo, M., Shin, J., Jang, C., & Yu, Y. (2003). Toxicity of greenhouse pesticides to multicolored Asian lady beetles, Harmonia axyridis (Coleoptera: Coccinellidae). Biological Control, 28(2), 164-170.

Chapter 2: Evaluating factors affecting zucchini as a trap crop

for squash vine borer

2.1 Introduction

Squashes are some of the most popular vegetables grown in home gardens and on commercial vegetable farms, but squash plants are often killed by the squash vine borer

Row covers can be used by commercial growers to exclude pests. A row cover is a lightweight cloth that is installed over the plants and allows sunlight and water to pass through, but excludes pests. For a row cover to be effective, it needs to be deployed before the insect can infest the plants, and needs to be removed once female flowers appear, to allow bees to pollinate the flowers. For effective SVB management, row covers should be deployed before SVB adult emergence in June to prevent the adults from laying eggs on the squash plants. Although there is no published report on use of

16 row covers for SVB control, row covers have been effective for controlling other cucurbit pests. Row covers have been shown to reduce the amount of damage to zucchini caused by silverleaf whitefly (Bemisia tabaci) (Qureshi, Midmore, Syeda, & Playford, 2007).

The use of row covers reduced the densities of whitefly and aphid in zucchini when compared to the untreated control (Costa, Johnson, & Ullman, 1994). Row covers also produced higher zucchini yields when compared to insecticide alone, under high pest pressure from silverleaf whiteflies (Qureshi et al., 2007). Row covers increased the yields of cucumbers compared to bare soil in a study done in Mexico (Ibarra-Jiménez,

Quezada-Martin, & de la Rosa-Ibarra, 2004).

Altered planting time and trap cropping are cultural tactics to potentially control

SVB. If a grower delays the planting of cucurbit crops for several weeks, it might reduce

SVB infestation, because SVB adults prefer to lay their eggs on larger, more mature plants and the adults might leave the area if the host plants are not large enough (Hahn &

Sciabarrasi, & Calderwood, 2003).

Our objective for this trial was to see how planting time, row covers and leaving zucchini unharvested affect the infestation rates of zucchini by squash vine borer. The hypothesis for this experiment would be that planting early, leaving the zucchini unharvested, and using row covers would make the most attractive trap crop for squash vine borer.

2.2 Materials and Methods

The experimental design was a randomized complete block with eight treatments and four blocked replicates. Treatments were three factors each at two levels: planting time (early versus late), row covers (with versus without), and harvest status (unharvested vs. harvested regularly). Each plot had one row of five zucchini plants spaced two feet apart. Rows were 6 feet apart, and there was a 12 ft bare alley between blocks. In 2015, the trial was done at one location. In 2016, the trial was done at each of two locations within the same farm. The trial was conducted at OSU’s Waterman Agricultural and

Natural Resources Laboratory in Columbus, Ohio in both years.

The zucchini variety used was ‘Spineless Perfection’ from Johnny’s Selected

Seeds (Winslow, Maine) in 2015 and from Seedway (Hall, NY) and Harris Seeds

(Rochester, NY) in 2016. Seeds were planted in plug trays in a greenhouse on 30 April and 1 June 2015, and 25 April and 25 May 2016. Black plastic mulch was installed in 18 rows before the zucchini were transplanted. Early planting treatments were established by transplanting on 21 May 2015 and 18 May 2016. Late planting treatments were established by transplanting 18 June 2015 and 15 June 2016. After transplanting, all plants received a soil drench of Admire Pro (imidacloprid; Bayer Crop Science, Research

Triangle Park, NC) at 10.5 fluid oz per acre, to prevent cucumber beetle damage. Admire

Pro was chosen because it has no effect on Lepidopterans, including squash vine borer.

Row covers (72-inch Agribon 19; Johnny’s Selected Seeds, Winslow, Maine) were deployed on half of the plots immediately after transplanting and application of

Admire Pro. Row covers were removed after the first female flower was found. Row covers were removed 23 June and 19 July 2015 and 20 June and 6 July 2016, for early and late plantings respectively.

The squash vine borer adult emergence was monitored with three Heliothis pheromone traps (Great Lakes IPM Incorporated, Vestaburg, MI) with a squash vine borer lure (Great Lakes IPM Incorporated, Vestaburg, MI). Traps were set up in early

May and were checked three times per week. The traps were used to see how the squash vine borer emergence dates related to when the zucchini when row covers were removed.

Zucchini fruit that were 6 inches or longer were harvested every 2-3 days from 23

June to 13 August 2015 and from 21 June to 22 August 2016. Zucchini yield was measured as number of fruit harvested and as weight (in kg) per plot. Yield was analyzed by ANOVA in R (R Development Core Team, 2014).

To evaluate the SVB infestation rate, a destructive evaluation was made at the end of the season. Each zucchini plant was cut at the base of the main stem, then split in half

19 to about one foot above ground. The stem was examined for any frass, tunneling, or larvae that were on the outside or inside of the plant. If a plant was dying or severely wilting, then the destructive evaluation was done early starting 22 July in 2015 and 28

July in 2016 for that plant. Once per week, the plots were checked for dying plants to make sure that they were evaluated before they decayed. The final destructive evaluation took place immediately after the final harvest. The number of zucchini plants that had signs of squash vine borer infestation was recorded for each plot then the percentage infested was calculated. Infestation rates were analyzed using logistic regression in R (R

Development Core Team, 2014).

2.3 Results

The effect of planting time was that the late plantings of zucchini had significantly lower infestation rates by SVB than early plantings in 2015 (P < 0.01) and in both the north and south fields in 2016 (P < 0. 01) (Figure 1). The infestation rates varied from a low of 1% in late plantings in 2016, to a high of 64% in early plants for

2015.

The influence of row covers on the infestation rates of SVB was not as consistent as the effect of planting date. In 2015, there was no significant difference in the infestation rates between zucchini with row covers and zucchini without row covers (P =

0. 71) (Figure 2). However for both the north and south fields in 2016, the zucchini with row covers had significantly higher infestation rates than those without row covers

(north: P < 0.01; south: P < 0.01; Figure 2). Compared to the planting time treatments,

20 the infestation rates of row cover treatments had a smaller range, from a low of 15% in the north field without row covers to a high of 41% in the 2015 field without row covers.

The infestation rates for harvested versus unharvested plants showed the most variation of the three factors evaluated (Figure 3). Unharvested plants had significantly higher infestation rates than harvested plants only in the north field in 2016 (P < 0. 01), while in the 2015 field, the unharvested plants had only slightly higher infestation rates than in harvested plants (P = 0. 14). In the 2016 south field, the unharvested plants had a slightly lower infestation rate than the unharvested plants (P = 0. 36).

The yield expressed as the average number of fruit produced per plant over the entire season showed that the zucchini planted early, with and without row covers, had significantly higher yields than the zucchini planted late in all three fields (2015: F =

25.65; df = 1, 429; P < 0. 01; north 2016: F = 22.94; df = 1, 365; P < 0.01; south 2016; F

= 11.88; df = 1, 365; P < 0.01) (Table 1). The same trend in the effect of planting date was seen for the yield expressed as weight, (2015: F = 22.65; df = 1, 429; P < 0. 01; north 2016: F = 12.65; df = 1, 365; P < 0.01; south 2016; F = 10.22; df = 1, 365; P <

0.01) (Table 1).

The number of harvested fruit in plots with row covers versus without row covers, planted early and late, was not significant in any year (2015: F = 1.66; df = 1, 429; P =

0.2; north 2016; F = 1.24; df = 1, 365; P = 0.27; south 2016; F = 0.4, df = 1, 365; P =

0.53). There was also no significant difference between plants with or without row covers when weight was measured, in any of the fields (2015: F = .439; df = 1, 429; P =

0. 51; north 2016: F = 0.98; df = 1, 365; P = 0.32; south 2016; F = 11.88; df = 1, 365; P =

0.47).

2.4 Discussion

The goal of this trial was to find out what factors would make a good trap crop. A good trap crop should be more attractive to the target pest than the main crop and should require no more maintenance than the main crop. The main crop should have strong yields and be profitable, while the profitability of the trap crop is not as important because its purpose is to reduce the yield losses in the main crop. Factors that are associated with higher infestation rates will be ideal for a trap crop, while factors associated with lower infestation rates would be ideal for the main crop. However, the main crop needs to take into account the yield to determine whether or not a factor would be economically viable.

Our most constant finding in this study was that a four-week delay in planting significantly reduced the infestation of squash vine borer infestations in zucchini. A reason for this finding was likely that the later plants were smaller during the peak emergence of SVB. When given the choice between the small plants that were planted in June and the larger plants that were planted in May, the squash vine borer prefers the thicker stems of the earlier planting. However, the infestation rate for the late plantings was not zero, likely due to infestation by the individuals that emerged later in the season when the plants had thicker stems. The trend of lower yields in the later plantings than the earlier plantings is a concern. Lower yield was likely due to the plants having a shorter growing season due to being planted four weeks later. 22

We had expected either of two outcomes from use of row covers as they relate to infestation by SVB: row covers might result in lower infestation by SVB if the row covers were in place during the time of oviposition, or they might result in higher infestation by SVB if they were in place so early that they allowed faster growth of the plants, and the larger plants were then exposed to SVB once the row covers were removed. We saw the first outcome in 2015, although differences were not statistically significant, and we saw the second outcome in 2016 at both sites. The timing of SVB adult emergence was similar in 2015 and 2016 (Figure 4) but the row covers had a significant effect on infestation only in 2016.

In studies in Iowa, infestation rates of SVB were significantly higher in zucchini grown with row covers than in zucchini grown without row covers in one year (Tillman,

Nair, Gleason & Batzer 2015) but not in the next year (Tillman et al., 2015). One reason is that Tillman et al. (2015) were spraying insecticide for SVB after they reached a threshold, which also would reduce the infestation rates, whereas our study did not use any insecticides to target SVB; we used only used imidacloprid, which does not affect

SVB (C. Welty, personal communication). It should also be noted that the main focus of the study by Tillman et al. (2015) was not on SVB management but on comparing row cover and strip tillage systems with plasticulture systems. Their use of row covers also was not associated with a significant difference in yield as expressed in weight or number of fruit, compared to zucchini without row covers.

When comparing the SVB infestation rates between the zucchini plants left unharvested and the zucchini plants that were harvested, the unharvested plants were

23 significantly more infested in only one of the three fields tested. The differences in infestation between harvested and unharvested plants in the other two fields were not significant. This is not strong enough evidence to confirm the findings in the 2008 study that found the infestation rates were significantly higher in the unharvested zucchini plants compared to the zucchini plants that were harvested on a regular basis (Welty &

Jasinski, 2008). However, this could be due to the fact that the unharvested zucchini plants in the 2008 study were concentrated throughout one entire field, while the unharvested zucchini plants in our fields were small plots that were intercropped with zucchini plants that were harvested on a regular basis. It could be that SVB is more strongly attracted to a large patch of unharvested zucchini plants and that the attractiveness is diminished when the proportion of unharvested zucchini plants is reduced.

In our study, the differences in yield between zucchini with row covers and zucchini without row covers was not significant. Past studies have indicated that row covers can increase the yield of zucchini (Ibarra-Jiménez et al., 2004). In the Iowa study, the researchers found that the use of row covers was not associated with a significant difference in yield as expressed in weight or number of fruit, compared to zucchini without row cover (Tillman et al., 2015). One reason for this difference could be that the

Ibarra (2004) study was done in Mexico while both the Tillman (2015) and our SVB trial were done in the northern U.S. The Warmer climate of Mexico could influence the yields.

The zucchini in our trial that were planted earlier had a significantly higher yield compared to zucchini planted later. However, it should be noted that the late plantings were planted much later than the normal planting time for zucchini. For a main crop, planting in mid June would hurt the yield as much or more than the damage caused by

SVB.

Based on our results, planting a trap crop earlier than the main crop would increase its effectiveness. To reduce yield loss from planting later, the main crop could be deployed less than four weeks after the trap crop or the trap crop could be planted earlier in the year such as the first of May. In a follow-up study, it would be interesting to deploy unharvested zucchini as a perimeter trap crop or as strips within a field to evaluate whether that could make it more attractive to squash vine borer than having it intercropped as it was in this study.

2.5 References

Adler, L., & Hazzard, R. (2009). Comparison of perimeter trap crop varieties: effects on herbivory, pollination, and yield in butternut squash. Environmental Entomology, 38(1), 207-215.

Hahn, J., & Burkness, S. (2007). Squash vine borer management in home gardens. University of Minnesota. Retrieved from http://www.extension.umn.edu/garden/insects/find/squash-vine-borers/

Hokkanen, H. M. (1991). Trap cropping in pest management. Annual Review of Entomology, 36(1), 119-138.

Ibarra-Jiménez, L., Quezada-Martin, M., & de la Rosa-Ibarra, M. (2004). The effect of plastic mulch and row covers on the growth and physiology of cucumber. Animal Production Science, 44(1), 91-94.

McPherson, R., & Newsom, L. (1984). Trap crops for control of stink bugs (Hemiptera, Pentatomidae) in soybean. Journal of the Georgia Entomological Society, 19(4), 470-480.

Pearson, G. (1995). Sesiid pheromone increases squash vine borer (Lepidoptera: Sesiidae) infestation. Environmental Entomology, 24(6), 1627-1632.

R Development Core Team. (2014). R: A language and environment for statistical computing. In. Vienna, Austria: R Foundation for Statistical Computing.

Shelton, A., & Badenes-Perez, F. (2006). Concepts and applications of trap cropping in pest management. Annual Review of Entomology, 51, 285-308.

Tillman, J., Nair, A., Gleason, M., & Batzer, J. (2015). Rowcovers and strip tillage provide an alternative to plasticulture systems in summer squash production. HortScience, 50(12), 1777-1783.

Welty, C., & Jasinski, J. (2008). Squash vine borer control on zucchini in Ohio. Ohio State University. Retrieved from http://entomology.osu.edu/welty/pdf/OhioZucchini2008_FinalReport.pdf

2.6 Figures

Figure 1: Infestation rates of squash vine borer in early and late plantings of zucchini, with other factors combined, at one site in 2015 and at two sites in 2016, in Columbus,

Ohio. Analysis was separate for each site and year.

Figure 2: Infestation rates of squash vine borer for zucchini with row covers (RC) and without row covers (NoRC), with other factors combined, at one site in 2015 and at two sites in 2016, in Columbus, Ohio. Analysis was separate for each site and year.

Figure 3: Infestation rates of squash vine borer for zucchini plants that were harvested

(Har) and unharvested (UnHar), with other factors combined, at one site in 2015 and at two sites in 2016, in Columbus, Ohio. Analysis was separate for each site and year.

3.5

2.5

1.5 2015 2016 1 Mean # of Adults per Trap per day 0.5

0 3-Jul 5-Jun 4-Sep 7-Aug 10-Jul 17-Jul 24-Jul 31-Jul 12-Jun 19-Jun 26-Jun 14-Aug 21-Aug 28-Aug 22-May 29-May

Figure 4: The number of SVB adults caught in the pheromone traps at Waterman Farm in 2015 and 2016; mean of three traps.

2.7 Tables

Treatment Number of fruit per plant Weight (kg) of fruit per plant 2015 2016 2016 south 2015 2016 north 2016 south north Early planting 9.4 A 5.2 A 3.7 A 3.8 A 2.6 A 1.8 A Late planting 5.2 B 3.7 B 2.7 B 1.9 B 1.8 B 1.3 B P < 0.01 P < 0.01 P < 0.01 P < 0.01 P < 0.01 P < 0.01

Table 1: Yield per zucchini plant for the entire season for each treatment that was harvested, at one site in 2015 and at two sites in 2016, in Columbus, Ohio. Within each column, treatments with the same letter are not significantly different.

Treatment Number of fruit per plant Weight (kg) of fruit per plant 2015 2016 2016 south 2015 2016 north 2016 south north No Row Cover 7.1 A 4.3 A 3.3 A 2.7 A 2.1 A 1.6 A Row Cover 7.6 A 4.6 A 3.1 A 3.0 A 2.3 A 1.5 A P = 0.2 P = 0.27 P = 0.53 P = 0.51 P = 0.32 P = 0.47

Table 2: Yield per zucchini plant for the entire season for each treatment that was harvested, at one site in 2015 and at two sites in 2016, in Columbus, Ohio. Within each column, treatments with the same letter are not significantly different.

Chapter 3: Delayed planting for squash vine borer

management in home garden squash

3.1 Introduction

Squashes are some of the most popular vegetables grown in home gardens and on commercial vegetable farms, but squash plants are often killed by the squash vine borer,

Melittia cucurbitae (Lepidoptera: Sesiidae) before they have reached their yield potential.

As a key pest of squash and pumpkins, squash vine borer causes up to 100% crop loss in home gardens and 25% crop loss in commercial fields (Pearson, 1995). To reduce the amount of damage by squash vine borer, gardeners and commercial growers use various management tactics such as row covers, delayed planting, and insecticide applications, although most of these methods have not been thoroughly tested and compared.

Row covers can be used by gardeners and commercial growers to exclude pests.

A row cover is a lightweight cloth that is installed over the plants and allows sunlight and water to pass through, but excludes pests. For a row cover to be effective, it needs to be deployed before the insect can infest the plants, and needs to be removed once female flowers appear, to allow bees to pollinate the flowers. For effective squash vine borer management, row covers should be deployed before squash vine borer adult emergence in June to prevent the adults from laying eggs on the squash plants. Although there is no 33 published report on use of row covers for squash vine borer control, row covers have been effective for controlling other cucurbit pests. Row covers have been shown to reduce the amount of damage to zucchini caused by silverleaf whitefly (Bemisia tabaci)

(Qureshi, Midmore, Syeda, & Playford, 2007). The use of row covers reduced the densities of whitefly and aphid in zucchini when compared to the untreated control

(Costa, Johnson, & Ullman, 1994). Row covers also produced higher zucchini yields when compared to insecticide alone, under high pest pressure from silverleaf whiteflies

(Qureshi et al., 2007). Row covers increased the yields of cucumbers compared to bare soil in a study done in Mexico (Ibarra-Jiménez, Quezada-Martin, & de la Rosa-Ibarra,

2004).

Altered planting time and trap cropping are cultural tactics to potentially control squash vine borer. If a grower delays the planting of cucurbit crops for several weeks, it might reduce squash vine borer infestation, because squash vine borer adults prefer to lay their eggs on larger, more mature plants and the adults might leave the area if the host plants are not large enough (Hahn & Burkness, 2007). Late plantings could also be used in conjunction with an early planting; in this scenario, the early planting would act as a trap crop, which is an adjacent crop that is more attractive than the main crop. It is recommended that trap crops are used on about 10% of the total crop area (McPherson &

Newsom, 1984; Shelton & Badenes-Perez, 2006). A trap crop can be a different species of crop than the main planting, or it can be the same crop used in a more appealing way.

One example is Blue Hubbard squash used as a trap crop with the main crop of butternut squash, for management of striped cucumber beetle (Adler & Hazzard, 2009). Using a

34 trap crop such as Hubbard squash has reduced the use of insecticides by up to 94% for striped cucumber beetle in Massachusetts (Cavanagh, Hazzard, Adler, & Boucher, 2009).

In most cases, the trap crop is planted a few weeks before the main crop (Hokkanen,

1991). A trap crop can be deployed along the perimeter or in strips within the main crop

(Boucher, Ashley, Durgy, Sciabarrasi, & Calderwood, 2003).

Using the concept of trap cropping would be different on the garden scale than in a commercial field due to the limited space available. The objective of this project is to test the management tactics of delayed planting and row covers at the garden scale to see if these tactics alone or together have any impact on the infestation rates of squash vine borer.

3.2 Materials and Methods

A field trial was done with a factorial design that had two factors each at two levels: planting time (early versus late) and row covers (with versus without). The early date was typical of what most gardeners use, and the late date was four weeks later than the typical planting date. The trial was conducted at ten sites in Franklin and Delaware

Counties. Collaborators on the project were thirteen gardeners associated with the local

Master Gardener Volunteer Program. Each site had four zucchini plants planted early and four zucchini plants planted late, with plants 2 feet apart.

At five of the ten sites, row covers (83 inch wide Agribon 19, Johnny’s Selected

Seed; Winslow, Maine) were installed immediately after transplanting, anchored firmly to the soil by garden staples, and removed once the first female flower was found. Row covers were removed on 19 June for the early planting in 2015, between 16 June and 17 35

June for the early planting in 2016, between 2 July and 23 July for the late planting in

2015 and between 15 July and 21 July for the late planting in 2016.

‘Spineless Perfection’ (Johnny’s Selected Seeds; Winslow, Maine) zucchini seeds were started in a greenhouse on 30 April for the early treatment and on 1 June for the late treatment, and transplanted on 14 May and 15 May for the early treatment and 11 June and 12 June for the late treatment in 2015. Due to a crop failure at Johnny’s Selected

Seeds in 2016, zucchini seed in 2016 was purchased from Horticultural Products and

Services (Randolph, WI). In 2016, seeds were started in a greenhouse on 25 April for the early treatment and on 25 May for the late treatment, then transplanted on 19 May and 20

May for the early planting and 16 June and 17 June for the late planting. Plants that died within two weeks of the initial transplant date were replaced.

To prevent damage by cucumber beetles, without affecting squash vine borer, two tactics were used. At sites for which the gardener permitted insecticide, plants were treated immediately after transplanting with a soil drench of imidacloprid (Bayer

Advanced Fruit, Citrus & Vegetable Insect Control Concentrate; Bayer Crop Science LP;

Research Triangle Park, NC). At sites for which the gardener did not permit insecticide use, the gardener was provided with an aspirator (BioQuip products Inc.; Rancho

Dominguez, CA) and requested to use it several days per week for mechanical removal of cucumber beetles.

In 2016, an additional trial was done to evaluate the use of a single early plant that was left unharvested as a trap crop for a slightly later set of plants. At each of ten sites, four zucchini were transplanted, at a 2-foot spacing, at the typical planting time of mid

May. Five sites had an additional zucchini transplanted two weeks earlier than the remaining four zucchini plants, and five sites did not have the additional plant. The trap plants were seeded in a greenhouse on 25 April then transplanted on 12 May and 13 May.

The main crop plants were started in a greenhouse on 18 May then transplanted on 25

May and 26 May at all 10 sites. Plants that died no more than one week after the initial transplant date were replaced.

In both trials, collaborators of the project were given control over the method of site preparation and the amount and type of fertilizer used. Gardeners were asked to control cucumber beetles, keep the plants watered, and record the number of zucchini fruit six inches or larger that were harvested, by date.

All sites were inspected once per week to verify the health of the plants and to maintain the sites by weeding, cucumber beetle removal, row cover repair, and row cover removal. At the end of the growing season, or earlier if any plants died, each zucchini plant was cut at the base and the stem was cut open to check for presence of squash vine borer larva or frass or tunneling, to determine if it was infested. The plants were cut to check for squash vine borer from 24 July until 29 September 2015 and from 14 July until

23 September 2016. These destructive evaluations were done once any plant was starting to die, before desiccation could occur. The collaborators submitted their harvest data at the end of the season. Infestation rates were analyzed using logistic regression in R studio and the harvest data were analyzed using one-way ANOVA in R (R Development

Core Team, 2014).

3.3 Results

In 2015, the late-planted zucchini had significantly lower infestation rates than the early-planted zucchini when all row cover and no row cover plantings were combined (P

< 0.01) (Figure 5). There was no significant difference in infestation between the zucchini with row covers and zucchini without row covers with the early and late plantings combined (P = 0.70). At sites without row covers, the zucchini planted early had significantly higher infestation rates than the late planting (P < 0.01). The sites where the zucchini was planted under row covers, there was no significant difference between planting early and planting late (P = 0.99).

In 2016, the opposite effect was observed; the early plantings did not have significantly different infestation rates from the late plantings (P = 0.99), while zucchini plants without row covers had significantly higher infestation rates than zucchini plants with row covers (P = 0.01) (Figure 6). For zucchini planted under row covers; the early plantings had significantly higher infestation rates than the late plantings (P = 0.01).

The differences in yield between early versus late treatments in 2015 were not statistically significant for zucchini without row covers (F = 2.9; df = 1,8; P = 0.13) or with row covers (F = 5.1; df = 1,8; P > 0.05) but when the early and late treatments were combined, the difference was significant (F = 7.4; df = 1,18; P = 0.01) (Figure 7). When comparing the yields of zucchini with and without row covers, the differences in yield also were not significant (F = 1.2; df = 1,18; P = 0.30). In 2016, the difference between early versus late planting was not significant in the zucchini without row covers (F = 2.0; df = 1,8; P = 0.19) or with row covers (F = 4.5; df = 1,6; P = 0.07) (Figure 8). There

38 were also no significant differences in yield when with or without row covers were combined (F = 2.9; df = 1,16; P = 0.11).

In the trap plant trial in 2016, there was no significant difference in infestation rates between the zucchini plants adjacent to a trap plant and the plants without the trap plant (P > 0.99) (Table 3). For the trap plant trial, there was no significant difference between the yields of zucchini with a trap plant and without a trap plant (F = 0.1; df =

1,7;P > 0.99).

3.4 Discussion

In this study, planting four weeks late resulted in significantly lower infestation in

2015 but not in 2016. However, the infestation levels in 2016 were numerically lower in four of the late plantings even though they were not statistically significant. The reason for the differing results in the two years might be the small plot sizes, which were used to simulate the size of an actual garden. The problem with small plot sizes is that they are more vulnerable to variation than larger sample sizes. A factor that added to the variation was that the zucchini with row covers in 2015 and without row covers in 2016 had one of the sites removed from the analysis due to incomplete data.

For the effect on yield, there was a trend for the earlier zucchini to have higher yields although it was not significantly higher. Some of the gardens had productive yields in the early plantings but then did not have a single zucchini fruit in the late plantings, possibly due to the late planting having inadequate space or had inadequate water to develop a normal root system.

After documenting lower yields of plantings delayed by four weeks in 2015, the trap plant trial in 2016 used only a two-week gap between planting the main crop plants and the trap plant, instead of four weeks, to reduce the lower yields. In the trap plant trial, there was no difference between the infestation rates of the zucchini with a trap plant and without a trap plant. One possible reason for this was that the trap plants at all five sites were infested with two-spotted spider mite in the greenhouse before they were planted, while the main crop plants never had the spider mite infestation. Although an attempt was made to manage spider mites by spraying Insecticidal Killing Soap

(Woodstream Corp., Lititz, PA) and releasing multicolored Asian lady beetle larva, the trap plants remained weak. During the first two weeks after transplanting, some of the trap plants had minimal growth. As a result, the main crop plants quickly outgrew the trap plants, which could have made the main plantings equally appealing to SVB because the plants were the same size. Even at sites at which the trap plants that did not have their growth hampered by two-spotted spider mites, the SVB infestation rates were the same. However, only one year of data was obtained, so if the trial were repeated with healthier plants, or with a 3-week gap between planting dates, then the conclusions might be different.

In conclusion, there was some benefit to delaying planting by four weeks because the zucchini planted later did have lower infestation rates when compared to the normal early plantings even though the difference was significant only in 2015. However the yield data showed that while the later plantings have lower infestation rates, there also was a trend for them to have lower yields. In future research, the differences in yield

40 could be mediated by delaying planting by two or three weeks instead of four weeks.

These findings show that delayed planting is not a stand-alone management tactic for

SVB but might be one component of a multi-tactic approach to managing this pest in gardens.

3.5 References

Adler, L., & Hazzard, R. (2009). Comparison of perimeter trap crop varieties: effects on herbivory, pollination, and yield in butternut squash. Environmental Entomology, 38(1), 207-215.

Hahn, J., & Burkness, S. (2007). Squash vine borer management in home gardens. University of Minnesota. Retrieved from http://www.extension.umn.edu/garden/insects/find/squash-vine-borers/

Hokkanen, H. M. (1991). Trap cropping in pest management. Annual Review of Entomology, 36(1), 119-138.

Ibarra-Jiménez, L., Quezada-Martin, M., & de la Rosa-Ibarra, M. (2004). The effect of plastic mulch and row covers on the growth and physiology of cucumber. Animal Production Science, 44(1), 91-94.

McPherson, R., & Newsom, L. (1984). Trap crops for control of stink bugs (Hemiptera, Pentatomidae) in soybean. Journal of the Georgia Entomological Society, 19(4), 470-480.

Pearson, G. (1995). Sesiid pheromone increases squash vine borer (Lepidoptera: Sesiidae) infestation. Environmental Entomology, 24(6), 1627-1632. 41

R Development Core Team. (2014). R: A language and environment for statistical computing. In. Vienna, Austria: R Foundation for Statistical Computing.

Shelton, A., & Badenes-Perez, F. (2006). Concepts and applications of trap cropping in pest management. Annual Review of Entomology, 51, 285-308.

3.6 Figures

Figure 5: The mean infestation rates of squash vine borer in zucchini for each treatment separately and combined, for planting date and row cover experiment at garden sites in

Franklin County, Ohio, in 2015. Each set of two bars that are the same color were analyzed together.

Figure 6: The mean infestation rates of squash vine borer in zucchini for each treatment separately and combined, for planting date and row cover experiment at garden sites in

Franklin and Delaware Counties, Ohio, in 2016. Each set of two bars that are the same color were analyzed together.

Figure 7: The mean yield per zucchini plant over the entire season for each treatment separately and combined, for planting date and row cover experiment at garden sites in

Franklin County, Ohio, in 2015. Each set of two bars that are the same color were analyzed together.

Figure 8: The mean yield per zucchini plant over the entire season for each treatment separately and combined, for planting date and row cover experiment at garden sites in

Franklin and Delaware Counties, Ohio, in 2016. Each set of two bars that are the same color were analyzed together.

3.7 Tables

Treatment Infestation Rate Yield: mean number of fruit per plant With Trap Plant 85% 8.8 No Trap Plant 100% 9.7

Table 3: The mean infestation rates of squash vine borer and the yield over the entire season for zucchini with an early trap-crop plant and zucchini without an early trap-crop

plant, Franklin and Delaware Counties, Ohio, 2016.

Chapter 4: Intensity of insecticide spray schedules as a factor

in control of squash vine borer

4.1 Introduction

Squashes are some of the most popular vegetables grown on commercial vegetable farms, but squash plants are often killed by the squash vine borer, Melittia cucurbitae (Lepidoptera: Sesiidae) before they have reached their yield potential. As a key pest of squash and pumpkins, squash vine borer causes up to 100% crop loss in home gardens and 25% crop loss in commercial fields (Pearson, 1995). To reduce the amount of damage by squash vine borer, gardeners and commercial growers use various management tactics such as row covers, delayed planting, and insecticide applications, although most of these methods have not been thoroughly tested and compared.

Winter is spent as a pupa in the soil. Around the middle of June in Connecticut, the squash vine borer starts to emerge from the soil as an adult (Friend, 1931). Adult males live for an average of three days after emerging, while female adults live for an average of four days (Canhilal, Carner, Griffin, Jackson, & Alverson, 2006). The adults mate, and females lay eggs at the base of main stem and leaf stalks of cucurbit plants

(Friend, 1931). Each female can lay between 150 to 200 eggs per season (Friend, 1931).

Eggs take 7-11 days to hatch, and the young larvae then burrow into the stem of the plant

(Canhilal et al., 2006). From a management perspective, the first-instar larva is the most important part of the life cycle because insecticides will kill larvae only during the short time that young larvae are on the outside of the stem. Once larvae are inside the stem, applications of contact insecticide will no longer affect them. Larvae stay inside the plant for four to six weeks, feeding on the stem tissue. If the host dies during this time, larvae can move to a different plant (Friend, 1931). After the larval stage is complete, the larva exits the plant, burrows into the soil, and forms a pupa (Friend, 1931). The number of generations per year depends on location. In the northern U.S, there is only one generation per year, while in southern U.S, there are two generations per year (Canhilal et al., 2006; Friend, 1931).

To properly manage SVB, growers need to know when adults are emerging so that management tactics can be used at the best time. SVB can be monitored in traps baited with synthetic female sex pheromone that attracts males, which allows the grower to estimate the squash vine borer population size over time (Pearson, 1995). The most effective pheromone trap for monitoring squash vine borer is a conical mesh trap

(Jackson, Canhilal, & Carner, 2005). Monitoring the plants by scouting for entry holes and frass on the outside of the lower stem can reveal initial damage by squash vine borer, but can underestimate damage when holes are on the underside of the stem that is difficult or impossible to observe without damaging the plant (Hahn & Burkness, 2007).

In one study, researchers looked for adults resting under leaves instead of holes in the stems because they were trying for early detection, to prevent larvae from getting into the stem as opposed to simply seeing if the plants are infested or not (Brust, 2010).

One of the most common forms of control for squash vine borer is to use insecticides before the larva can bore into the plant (Brust, 2010). Spraying weekly for six weeks after squash vine borer adults begin to emerge is a schedule that is sometimes used for squash vine borer control (Brust, 2010). However, the optimal timing and number of sprays is uncertain, and spraying six times might lead to overuse of insecticide and a negative impact on the environment. By scouting for adult females under leaves and using pheromone traps, the number of insecticide applications can be reduced by

50% (Brust, 2010).

Several insecticidal chemicals are used to control squash vine borer. Researchers found that bifenthrin plus zeta-cypermethrin (Hero 1.24EC), endosulfan (Thionex 3EC), carbaryl (Sevin XLR) all resulted in significantly lower infestations of squash vine borer compared to untreated zucchini using four applications (Welty & Jasinski, 2008).

Researchers have found that there was a significantly lower infestation rate of squash vine borer when using spinosad (Entrust 80 WP) compared to an untreated control in

2012 and 2013 but not in 2014 (Seaman, Lange, Luton, & Shelton, 2012; Seaman, Lange,

& Shelton, 2013, 2014). A study with buttercup squash in Ohio in 2012 showed excellent control of squash vine borer with six applications of pyrethrins + PBO

(Evergreen) whereas a similar trial in 2011 that used insecticide applications to target only cucumber beetles and not SVB had poor SVB control (C. Welty, personal communication). Our objective in this study was to determine the effect of different numbers of sprays for a botanical based insecticide for controlling squash vine borer and if fewer than six sprays can be used for effective control.

4.2 Materials and Methods

The trial was set up in a randomized complete block design with six treatments and four blocked replicates. For the insecticide treatments, pyrethrins + piperonyl butoxide (PBO) was applied on three schedules: a low intensity schedule in which it was applied twice (weeks one and three), a medium intensity schedule in which it was applied four times (weeks one through four), and a high intensity schedule in which it was applied six times (weeks one through six). The pyrethrins + PBO treatments were compared with two products applied on the low intensity schedule: a restricted-use pyrethroid (weeks one and three) and a general-use neonicotinoid product (weeks one and three). The sixth treatment was an untreated control.

The pyrethrins + PBO product used was Evergreen (McLaughlin Gormley King

Company; Minneapolis, MN) at 8 fl oz/A (a median rate) in 2015 and 16 fl oz/A (the maximum rate on the label) in 2016. The general-use product used was Assail

(acetamiprid; United Phosphorus, Inc.; King of Prussia, PA) soluble granule formulation at 5.3 fl oz/A. The pyrethroid poduct used was Gladiator (zeta-cypermethrin + avermectin

B1; FMC Corporation; Philadelphia, PA) emulsifiable in water formulation at 19 fl oz/A.

The zucchini ‘Spineless Perfection’ (Johnny’s Selected Seeds; Winslow, Maine) was seeded in 72-cell plug trays on 30 April 2015 and 25 April 2016. Plots were established by transplanting into black plastic much on 22 May 2015 and 16 May 2016 at

Waterman Agricultural and Natural Resources Laboratory in Columbus, Ohio. Plants that died within the first two weeks were replaced. For control of cucumber beetles, an

51 application of Admire Pro (imidacloprid as a suspension concentrate formulation) at 10.5 fl oz/acre was made as a transplant drench.

In 2015, each plot consisted of 20 zucchini plants with 10 plants in each of two rows, with 2 ft spacing between plants, 5 feet between rows, and a 10 ft bare alley between adjacent plots. Plots in 2015 were placed along two sides of a soybean field to maximize the edge effect and prevent spray drift between plots. The acetamiprid treatment was included in only in two of the four blocks due to a planting error in 2015.

The trial in 2016 consisted four long rows, with each row defined as a blocked replicate. Within each row were 6 plots. Each plot contained 15 zucchini plants. There was a 10-foot bare alley between adjacent plots and a 15-foot bare ally between rows.

The timing of the first application was ten days after squash vine borer adults were consistently found in Heliothis pheromone traps (Trécé Incorporated, Adair, OK) with a squash vine borer lure (Great Lakes IPM Incorporated, Vestaburg, MI) next to the field, which was on 12 June 2015 and 13 June 2016. The first applications were made on

22 June 2015 and 24 June 2016. Treatments were applied with a Solo backpack sprayer

(Solo, Newport News, VA) model #425 with a Twin Jet 8004 nozzle tip (Spraying

Systems Company, Wheaton, IL) that applied 108.9 gallons per acre. Applications were made in the evening to avoid spraying pollinators.

To evaluate the infestation rate, a destructive evaluation was made at the end of the season. Each zucchini plant was cut at the base of the main stem then split it in half, up to about 30 cm above ground. The stem was examined for any frass, tunneling, or larva on the outside or inside of the plant. If a plant was dying, the destructive evaluation

52 was done early, starting on 22 July 2015 and 28 July 2016. The final destructive evaluation took place immediately after the final harvest. The number of zucchini plants that had signs of squash vine borer infestation for each plot was recorded, then the infestation rate was calculated. The infestation rates were analyzed using logistic regression in R (R Development Core Team, 2014).

To determine if there were differences in yield among treatments, the number and weight of zucchini fruit harvested were recorded for every plot. Harvesting began on 19

June 2015 and 21 June 2016. Any zucchini 6 inches or longer was harvested. The zucchini was harvested every 2-3 days until the final harvest on 23 August 2015 and 17

August 2016 for a total of 33 harvests in 2015 and 28 harvests in 2016. The results were analyzed using one-way ANOVA in R (R Development Core Team, 2014).

4.3 Results

In both 2015 (Figure 9) and 2016 (Figure 10), a sustained catch of squash vine borer started in early June, and peak emergence occurred in late June. The number of squash vine borer caught in pheromone traps declined until mid July, and the counts remained low until August when the emergence of a smaller second generation was detected.

In both years, there were no significant differences among treatments (Table 4).

In both years, plots treated with Gladiator had the lowest infestation rate: 5.4% in 2015 and 3.3% in 2016 (Table 4). The treatment that had the highest infestation rate was different each year: the untreated plots had the highest infestation (29%) in 2015 and the

Evergreen treatment with four applications had the highest infestation (23%) in 2016. 53

The yield, expressed as the cumulative number of zucchini fruit per plant, was not significantly different among treatments in either year. In 2015, plots treated with

Evergreen with four applications had the highest average yield 20.7 fruit per plant and

Evergreen with two applications had the lowest yield with 18.3 fruit per plant (F = 0.32; df = 5, 13; P = 0.89; Table 2). In 2016, zucchini treated with Assail had the highest yield, with 21.3 fruit per plant and Evergreen with six applications had the lowest yield with 19 fruit per plant (F = 0 .89; df = 5, 615; P = 0.49; Table 5).

The yield expressed as the cumulative weight of fruit per plant was also not significantly different among treatments in either year. Zucchini treated with Evergreen four times had the highest weight among treatments, with 8.6 kg per plant for the entire season and Evergreen with two applications had the lowest with 7.6 kg per plant (F =

0.486; df = 5, 717; P = 0.79; Table 3) in 2015. In 2016, zucchini treated with Assail had the highest total weight with 10.5 kg per plant, and zucchini treated with Evergreen six times produced the lowest weight with 9.0 kg per plant (F = 1.4; df = 5, 663; P = 0.21;

Table 6).

4.4 Discussion

Our applications of insecticides covered the peak squash vine borer emergence in both years but with all six of the applications being completed by late July, the zucchini were exposed to the smaller second generation, which could have allowed additional infestation. One change made between 2015 and 2016 was that the rate of Evergreen was increased because of its poor efficacy at the lower rate used in 2015.

The infestation rates in both 2015 and 2016 did not differ significantly among treatments, which was likely related to low infestation rates in the untreated control. In

2015, frequent and large amounts of precipitation led to some adjustments in the timing of the applications such as having to re-apply the insecticide or having to delay the spray by one day. This could have influenced the effectiveness of the insecticides but does not explain the low infestation rates for the untreated control. In 2016, precipitation was not as prevalent but some pumpkins and yellow squash were planted nearby a few weeks after the zucchini, which could have also lowered the infestation rates of later generations of squash vine borer in this trial by providing additional resources for them. Although the zucchini plants were the largest cucurbits in the area in the beginning of the summer, the pumpkin and squash plants eventually grew to be as large as the zucchini plants, which the later generation of squash vine borer could have selected.

In other insecticide trials involving squash vine borer, inconsistent infestation rates have been known to occur. A foliar insecticide trial conducted in Virginia found no significant difference in the number of healthy plants that were not damaged by squash vine borer among four insecticide treatments: lambda-cyhalothrin (Warrior II), cyazypyr

(HGW86 10SE) + methylated seed oil (MSO), esfenvalerate (Asana XL) + MSO, and chlorantraniliprole (Coragen) + MSO, all with four applications (Kuhar, Doughty,

Wimer, & Jenrette, 2012). Likewise, an organic insecticide trial in 2014 also did not show any significant differences in squash vine borer infestation among an untreated control and five insecticide treatments: heat-killed Burkholderia spp. Strain A396

(Venerate), Chromobacterium subtsuge strain PRAA4-1 (Grandevo), azadirachtin +

55 pyrethrins (Azera), Bacillus thuringiensis (Javelin WG), spinosad (Entrust 80 WP), using three applications for each (Seaman, Lange, & Shelton, 2014). In two earlier trials,

Entrust and Bacillus thuringiensis (Agree) had significantly lower infestation rates of squash vine borer compared to the untreated control (Seaman, Lange, Luton, & Shelton,

2012; Seaman, Lange, & Shelton, 2013). In trials with conventional insecticides, researchers found that bifenthrin plus zeta-cypermethrin (Hero 1.24EC), endosulfan

(Thionex 3EC), and carbaryl (Sevin XLR) all had significantly lower infestations of squash vine borer compared to untreated zucchini using four applications (Welty &

Jasinski, 2008). Another trial also did not find a significant difference between

Evergreen, Asana (esfenvalerate), Pyganic (pyrethrins), Thiodan (endosulfan) and an untreated control for the number of plants with squash vine borer damage using four to six applications (Welty, 2006).

When comparing the yields either by weight or in number of fruit, none of the insecticide treatments showed a significant increase in yield compared to the untreated control. This implies that squash vine borer infestations did not do enough damage to significantly impact the yields. Squash vine borer is capable of having a significant impact on yields such as pumpkins (Brust, 2010) but in our trial the yields did not have much variation. In an Ohio trial with Hubbard squash, differences in yield by both weight and number of zucchini were not significant (Welty, 2006).

Based on our data, the impact of the number of sprays needed to control squash vine borer by pyrethrins + PBO was inconclusive. Future research on this topic could try using multiple sites to be sure to find sites at which the pest pressure is high enough to

56 cause economic damage. It is important to note that in both years, the zucchini treated with Gladiator had the lowest infestation rates even though the differences between treatments were not significant. The Gladiator treatment was only applied two times but still had lower infestation rates, which could imply that the number of applications for effective control would vary, based on the insecticide used. In the case of Gladiator, which is in the pyrethroid group of insecticides, has a longer presence in the field compared to pyrethrin and acetamiprid likely led to the better control even with the same number of applications or fewer than used for the other chemicals. In future studies it would be interesting to test the number of applications of other insecticides such as

Gladiator and Assail.

4.5 References

Brust, G. E. (2010). Squash vine borer (Lepidoptera: Sesiidae) management in pumpkin in the mid-Atlantic. Journal of Applied Entomology, 134(9-10), 781-788.

Friend, R. (1931). The squash vine borer. Connecticut Agricultural Experiment Station, Bulletin 328, 588-607.

Hahn, J., & Burkness, S. (2007). Squash vine borer management in home gardens. University of Minnesota. Retrieved from http://www.extension.umn.edu/garden/insects/find/squash-vine-borers/

Jackson, D. M., Canhilal, R., & Carner, G. R. (2005). Trap monitoring squash vine borers in cucurbits1, 2. Journal of Agricultural and Urban Entomology, 22(1), 27-39.

Kuhar, T. P., Doughty, H., Wimer, A., & Jenrette, J. (2012). Evaluation of foliar insectisides for the control of foliar insects in summer squash in Virgina, 2011. Arthropod Management Tests, 37(1), E56.

Pearson, G. (1995). Sesiid pheromone increases squash vine borer (Lepidoptera: Sesiidae) infestation. Environmental entomology, 24(6), 1627-1632.

R Development Core Team. (2014). R: A language and environment for statistical computing. In. Vienna, Austria: R Foundation for Statistical Computing.

Seaman, A. J., Lange, H., Luton, B., & Shelton, A. M. (2012). Squash vine borer control with insecticides allowed for organic production, 2011. Arthropod Management Tests, 37(1), E81.

Seaman, A. J., Lange, H., & Shelton, A. M. (2013). Squash vine borer control with insecticides allowed for organic production, 2012. Arthropod Management Tests, 38(1), E56.

Seaman, A. J., Lange, H., & Shelton, A. M. (2014). Squash vine borer control with insecticides allowed for organic production, 2013. Arthropod Management Tests, 39(1), E65.

Welty, C. (2006). Control of squash vine borer by insecticides. Ohio State University. Retrived from http://entomology.osu.edu/welty/pdf/SquashVineBorerReport2006.pdf

Welty, C., & Jasinski, J. (2008). Squash vine borer control on zucchini in Ohio. Ohio State University. Retrieved from http://entomology.osu.edu/welty/pdf/OhioZucchini2008_FinalReport.pdf

4.6 Figures

6 SVB1 5 SVB2 4 SVB3 3 Total Mean # SVB caught per day

0 3-Jul 5-Jun 4-Sep 7-Aug 10-Jul 17-Jul 24-Jul 31-Jul 12-Jun 19-Jun 26-Jun 14-Aug 21-Aug 28-Aug 22-May 29-May

Figure 9: The mean number of squash vine borer adults caught in three pheromone traps at Waterman Farm, Columbus, Ohio, in 2015. SVB 2 was the trap next to the chemical trial.

6 SVB1 5 SVB2 4 SVB3 3 Total Mean # SVB caught per day

0 6-Jul 1-Jun 8-Jun 3-Aug 13-Jul 20-Jul 27-Jul 15-Jun 22-Jun 29-Jun 10-Aug 17-Aug 24-Aug 31-Aug

Figure 10: The mean number of squash vine borer adults caught in three pheromone traps at Waterman Farm, Columbus, Ohio, in 2016. SVB 3 was the trap next to the chemical trial.

4.7 Tables

Treatment Mean percentage of plants infested by squash vine borer 2015 2016 Untreated 29.1% a 8.3% a Evergreen, 2 applications 25.9% a 6.7% a Evergreen, 4 applications 13.8% a 23.3% a Evergreen, 6 applications 21.3% a 6.7% a Assail, 2 applications 15.7% a 5.0% a Gladiator, 2 applications 5.4% a 3.3% a P = 0.25 P = 0.26

Table 4: The average infestation rates of squash vine borer for each treatment in 2015 and 2016, Columbus, Ohio. Within each column, means followed by the same letter are not statistically different.

Treatments Zucchini yield as number of Zucchini yield as number of fruit, 2015 fruit, 2016 Untreated 18.8 a 19.7 a Evergreen, 2 applications 18.3 a 20.5 a Evergreen, 4 applications 20.7 a 20.0 a Evergreen, 6 applications 19.0 a 19.0 a Assail, 2 applications 18.8 a 20.9 a Gladiator, 2 applications 19.4 a 21.3 a P = 0.89 P = 0.49

Table 5: The average yield per plant in number of zucchini over the entire season for each treatment in 2015 and 2016, Columbus, Ohio. Within each column, means followed by the same letter are not statistically different.

Treatments Zucchini yield in kg of fruit, Zucchini yield in kg of fruit, 2015 2016 Untreated 7.8 a 9.0 a Evergreen, 2 applications 7.6 a 10.2 a Evergreen, 4 applications 8.6 a 9.9 a Evergreen, 6 applications 7.8 a 9.0 a Assail, 2 applications 7.8 a 10.5 a Gladiator, 2 applications 8.0 a 10.5 a P = 0.79 P = 0.21

Table 6: The average yield per plant in kg for the entire season for each treatment in

2015 and 2016, Columbus, Ohio. Within each column, means followed by the same letter are not statistically different.

Chapter 5: Susceptibility of natural enemies to insecticides

used in garden plantings of cucurbit crops

5.1 Introduction

Squashes are some of the most popular vegetables grown in home gardens and on commercial vegetable farms, but squash plants are often killed by the squash vine borer

Several insecticidal chemicals are used to control SVB. Researchers found that bifenthrin plus zeta-cypermethrin (Hero 1.24EC), endosulfan (Thionex 3EC), carbaryl

(Sevin XLR) all resulted in significantly lower infestations of squash vine borer compared to untreated zucchini using four applications (Welty & Jasinski, 2008).

2014). However, one of the negative effects of using insecticides is that they can harm

64 non-target insects such as natural enemies that can help to keep other pest populations under control.

2003). Other insecticides such as spinosad do not lead to immediate mortality, but can reduce the survival of the first instar larva, prolong the development time, and decrease the fertility of female MALB (Galvan, Koch, & Hutchison, 2005).

In the case of another generalist, the insidious flower bug (Orius insidiosus,

One of the limitations of previous studies is that they used insecticides that are primarily for commercial use. The goal of this bioassay was to test insecticides that are marketed for home garden use for their effects on natural enemies, to determine the relative impact on predators found in cucurbits.

5.2 Materials and Methods

There were four to six treatments comprised of three to five common garden insecticides and one control. The insecticides and rates used were pyrethrins + piperonyl butoxide (PBO) (Pyrethrin Garden Insect Spray Concentrate; Bonide Products

Inc., Oriskany, NY), 9.2 ml per 473 ml (16 fl oz) of water; permethrin (Eight Insect

Control Vegetable Fruit and Flower Concentrate; Bonide Products Inc., Oriskany, NY),

7.4 ml per 473 ml of water; acetamiprid (Ortho Flower, Fruit & Vegetable Insect Killer

Concentrate; The Ortho Group, Marysville, OH), 5.5 ml per 473 ml of water; carbaryl

(Sevin Concentrate Bug Killer; TechPac LLC, Atlanta, Georgia), 5.6 ml per 473 ml of water; and spinosad (Captain Jack’s Deadbug Brew Concentrate; Bonide Products Inc.,

Oriskany, NY), 7.4 ml per 473 ml of water; and a control treatment of tap water.

Insecticide concentrations were calculated based on the rates recommended on the product labels for cucurbits.

Three of the trials tested the indirect effect of fresh insecticide residue on insects that were not treated directly. For these bioassays, each insecticide was applied with a spray bottle (SprayMaster; King of Prussia, PA) to both sides of a cut leaf piece. Each side of the leaf piece was air dried for 20-30 minutes before being placed in the test arena. For one additional trial, the combined effects of direct and indirect exposure of 66 insects to insecticide were tested by spraying the insects with the treatment before placing them in the arenas with treated leaf pieces.

Two species tested in the adult stage were the multicolored Asian lady beetle

(MALB) and the insidious flower bug, Orius insidiosus. MALB were field-collected one to three weeks prior to the bioassay from apple trees, spirea shrubs, and other sites around

Columbus, OH and held in plastic jars with excised flowering weeds and aphids as food sources. O. insidiosus were field collected from sweet corn silk using aspirators, 24-hours or less before the bioassay, and held in plastic vials with pieces of corn tassel.

For MALB, the test arena was an 8-ounce clear plastic food container, 11.4 cm

(4.5 inch) diameter, 3.8 cm (1.5 inch) depth (Solo; Urbana, Ill). Each treatment had four replicates, with one arena per replicate, and five beetles per arena. The test substrate was a 5.1 cm by 5.1 cm leaf piece that was cut from field-grown yellow squash, yellow zucchini, or peas. The arenas were arranged in randomized complete blocks on plastic trays with one block per tray. Trays were held in a growth chamber at 22o C with 16:8

L:D photoperiod. Trials were initiated on 29 June 2015 for the combined direct plus indirect exposure test using yellow squash leaves, and on 28 July 2015 (yellow zucchini leaves) and 25 May 2016 (pea leaves) for the indirect exposure tests.

For O. insidiosus bioassays, the test arena was a 20-ml glass vial, 5.1 cm height, with a screw-cap lid. There were six treatments with 20 replications for each, with one arena per replicate, and one insect per arena. The test substrate was a 2 cm by 4 cm zucchini leaf piece. The vials were completely randomized and placed in a growth

67 chamber at 26o C with a 16:8 L:D photoperiod. The bioassay was initiated on 22 July

2016.

Mortality was evaluated after 24 and 48 hours. Each insect was classified as alive, moribund, or dead. To be classified as alive, the insect had to be able to move one body length on its own after gentle prodding. An insect was considered dead if it did not move even when prodded with forceps. It was considered moribund if it could not move one full body length even if it could move some of its appendages. The mortality rates combined dead and moribund individuals, and were analyzed by one-way ANOVA in R studio (R Development Core Team, 2014).

5.3 Results

For the direct plus indirect exposure bioassay for MALB, all of the insecticides tested caused significantly higher mortality compared to the water control after 24 (F =

361; df = 3,12, P < 0.1) and 48 hours (F = 243; df = 3,12; P < 0.1) (Table 7). The MALB bioassay for indirect exposure in 2015 showed that treatment with permethrin, acetamiprid, and carbaryl caused significantly higher mortality than pyrethrin + PBO, spinosad, and water, after 24 hours (F = 64.5; df = 5,18; P < 0.01) and 48 hours (F =

40.5; df = 5,18; P < 0.01) (Table 7). In 2016, treatment with permethrin caused a significantly higher mortality rate than water and spinosad treatments after 24 hours (F =

14.3; df = 3,12; P < 0.01) and 48 hours (F = 9.5; df = 3,12; P < 0.01) (Table 7).

Treatment with permethrin did not cause significantly higher mortality than pyrethrins +

PBO after 24-hours (P = 0.10) but did cause significantly higher mortality after 48 hours

(P = 0.04). 68

In the O. insidiosus bioassays, treatment with acetamiprid caused significantly higher mortality than water, carbaryl, and spinosad (F = 4.8; df = 5,18; P < 0.01) (Table

8). Permethrin and pyrethrins+ PBO both caused significantly higher mortality than treatments with water (P < 0.01) and carbaryl (P = 0.02). None of the other treatments caused mortality that was significantly different than the control.

5.4 Discussion

The chemical permethrin was one of the few chemicals used that had high mortality rates for both MALB and O. insidiosus. In a bioassay with O. insidiosus on corn, researchers found that permethrin caused significantly higher mortality rates than the control (Al-Deeb, Wilde, & Zhu, 2001); this is similar to the results of our bioassay.

When acetamiprid was applied to MALB both directly and indirectly, the mortality rates were higher than the control for both types of exposure. The O. insidiosus that were exposed to acetamiprid had the highest mortality rates of all the treatments. Like permethrin, both MALB and O. insidiosus exposed to acetamiprid had higher mortality rates which implies that these chemicals should not be used in conjunction with biocontrol.

The application of carbaryl to MALB led to higher mortality rates than all other treatments except permethrin. When carbaryl was tested in bioassays on MALB in another study, the mortality rates were 100% (Smith & Krischik, 2000); although we used carbaryl in only one bioassay, the high mortality rate we found was consistent with this previous study. The O. insidiosus exposed to carbaryl did not have any significant

69 differences in mortality rates compared to the control, implying that O. insidiosus could survive applications of this insecticide.

In our trials, pyrethrins + PBO was toxic when sprayed directly onto the insect, but when the insects received only indirect exposure to the insecticide, the mortality rate was not significantly different than the control; this is similar to the results of a field trial that tested the effect of pyrethrins on MALB, in which researchers found that the insecticide did not significantly reduce the number of MALB compared to an untreated check (Galvan, Burkness, & Hutchison, 2006); although this was a field trial, the researchers’ findings for pyrethrins are similar to the results of our bioassay. When O. insidious was exposed to pyrethrins + PBO in our study, there was a significantly higher mortality compared to the control. One study found that pyrethrins + azadirachtin caused significantly higher mortality rates when compared to the control (Pazzini and Roach,

2015). Although pyrethrins were in the product used, it also contained azadirachtin, while the insecticide we used had only the synergist PBO, which means that the mortality rates of these studies cannot be compared directly.

When spinosad was applied to MALB in our bioassays, the mortality rates were lower than MALB treated with carbaryl and permethrin. Other studies that tested the mortality rate of MALB have produced similar results. One trial found that the mortality rates of MALB adults exposed to spinosad were not significantly different than the control, with single and multiple applications; the mortality rates of MALB ranged from

4.1 to 9.1% when treated with spinosad (Musser & Shelton, 2003), which is similar to the

0 to 25% mortality rate after exposure to spinosad found in our bioassays. For our O.

70 insidiosus bioassay, indirect exposure to spinosad did not cause a significant increase in the mortality rate compared to the control. In another report, researchers also found that spinosad did not cause a significantly higher mortality rate of O. insidiosus compared to the control (Studebaker & Kring, 2003); the bioassays in this study were repeated multiple times and produced results similar to ours although our trial was done only once.

Insecticides containing spinosad or pyrethrins + PBO do not have significant toxic effects on MALB based on our findings and past studies. Permethrin consistently causes increased mortality of MALB compared to the control. O. insidiosus seems to be less affected by spinosad or carbaryl, while permethrin seems to cause significant mortality .

However, with O. insidiosus, no firm conclusions can be made based on only one bioassay trial. Additional replicates of these bioassays need to be conducted with O. insidiosus to determine whether or not these insecticides significantly affect mortality of these natural enemies. Our tentative conclusion is that gardeners who are striving to incorporate biological control into their garden cucurbit management plan but have the need to use insecticide to control cucumber beetles, squash bug, and other pests, should avoid using permethrin, acetamiprid, carbaryl, and pyrethrins + PBO, but use spinosad instead. Future research could conduct bioassays on other natural enemies and test other insecticides.

5.5 References

Al-Deeb, M. A., Wilde, G. E., & Zhu, K. Y. (2001). Effect of insecticides used in corn, sorghum, and alfalfa on the predator Orius insidiosus (Hemiptera: Anthocoridae). Journal of Economic Entomology, 94(6), 1353-1360.

Galvan, T., Burkness, E., & Hutchison, W. (2006). Efficacy of selected insecticides for management of the multicolored Asian lady beetle on wine grapes near harvest. Plant Health Prog. doi, 10, 1094.

Musser, F. R., & Shelton, A. M. (2003). Bt sweet corn and selective insecticides: impacts on pests and predators. Journal of Economic Entomology, 96(1), 71-80.

Pearson, G. (1995). Sesiid pheromone increases squash vine borer (Lepidoptera: Sesiidae) infestation. Environmental Entomology, 24(6), 1627-1632.

Pezzini, D. T., & Koch, R. L. (2015). Compatibility of flonicamid and a formulated mixture of pyrethrins and azadirachtin with predators for soybean aphid (Hemiptera: Aphididae) management. Biocontrol Science and Technology, 25(9), 1024-1035.

R Development Core Team. (2014). R: A language and environment for statistical computing. In. Vienna, Austria: R Foundation for Statistical Computing.

Seaman, A. J., Lange, H., Luton, B., & Shelton, A. M. (2012). Squash vine borer control with insecticides allowed for organic production, 2011. Arthropod Management Tests, 37(1), E81.

Seaman, A. J., Lange, H., & Shelton, A. M. (2013). Squash vine borer control with insecticides allowed for organic production, 2012. Arthropod Management Tests, 38(1), E56.

Seaman, A. J., Lange, H., & Shelton, A. M. (2014). Squash vine borer control with insecticides allowed for organic production, 2013. Arthropod Management Tests, 39(1), E65.

Smith, S., & Krischik, V. (2000). Effects of biorational pesticides on four coccinellid species (Coleoptera: Coccinellidae) having potential as biological control agents in interiorscapes. Journal of Economic Entomology, 93(3), 732-736.

Welty, C., & Jasinski, J. (2008). Squash vine borer control on zucchini in Ohio. Ohio State University. Retrieved from http://entomology.osu.edu/welty/pdf/OhioZucchini2008_FinalReport.pdf

5.6 Tables

Treatment Mortality after direct and Mortality after indirect Mortality after indirect indirect exposure on exposure on yellow exposure on pea leaves, yellow squash leaves, zucchini leaves, 5/25/2016 6/29/2015 7/28/2015 24 hours 48 hours 24 hours 48 hours 24 hours 48 hours Water 5% a 10% a 5% a 10% a 5% a 5% a Spinosad - - 10% a 25% a 0% a 5% a Pyrethrin + 100% b 100% b 15% a 30% a 45% a 55% ab PBO Acetamiprid 100% b 100% b 80% b 90% b - - Carbaryl - - 90% b 100% b - - Permethrin 100% b 100% b 100% b 100% b 95% b 95% b P value P < 0.01 P < 0.01 P < 0.01 P < 0.01 P < 0.01 P < 0.01

Table 7: The average mortality rates of multicolored Asian lady beetle after 24 and 48 hours for the direct and indirect exposure and indirect exposure insecticide bioassays.

Within each column, mortality rates followed by same letter are not significantly different.

Treatment Mortality rate

Water 5.0% a

Pyrethrins + PBO 65.0% bc

Permethrin 66.7% bc

Acetamiprid 90.0% c

Carbaryl 22.2% a

Spinosad 35.0% ab

P < 0.01

Table 8: The average mortality rates of Orius insidiosus after 24 hours for indirect bioassays. Mortality rates followed by the same letter are not significantly different.

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