Post-Dispersal Predation of Common Lambsquarters and Common Waterhemp Seeds in Three Tillage Regimes

Iowa State University Capstones, Theses and Retrospective Theses and Dissertations Dissertations 1-1-2005 Post-dispersal predation of common lambsquarters and common waterhemp seeds in three tillage regimes Rocio van der Laat Iowa State University Follow this and additional works at: https://lib.dr.iastate.edu/rtd Recommended Citation van der Laat, Rocio, "Post-dispersal predation of common lambsquarters and common waterhemp seeds in three tillage regimes" (2005). Retrospective Theses and Dissertations. 20970. https://lib.dr.iastate.edu/rtd/20970 This Thesis is brought to you for free and open access by the Iowa State University Capstones, Theses and Dissertations at Iowa State University Digital Repository. It has been accepted for inclusion in Retrospective Theses and Dissertations by an authorized administrator of Iowa State University Digital Repository. For more information, please contact [email protected]. Post-dispersal predation of common lambsquarters and common waterhemp seeds in three tillage regimes by Rocio van der Laat A thesis submitted to the graduate faculty in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE Major: Crop Production and Physiology (Weed Science) Program of Study Committee: Micheal D.K. Owen, Major Professor Matthew Z. Liebman Jon J. Tollefson ·~ Iowa State University Ames, Iowa 2005 ii Graduate College Iowa State University This is to certify that the Master's thesis of Rocio van der Laat has met the thesis requirements of Iowa State University Signatures have been redacted for privacy iii To Ignacio, Ramon and my parents iv TABLE OF CONTENTS ABSTRACT Vl CHAPTERl.GENERALINTRODUCTION 1 Introduction 1 References 7 CHAPTER 2. QUANTIFICATION OF POST-DISPERSAL WEED SEED PREDATION AND INVERTEBRATE ACTIVITY-DENSITY IN THREE TILLAGE REGIMES 14 Abstract 14 Introduction 15 Materials and Methods 18 Quantification of post-dispersal weed seed predation in the field 19 Identification and quantification of possible insect seed predators 20 Estimating feeding ability and weed seed preference of possible predators under laboratory conditions 20 Statistical Analysis 22 Results 22 Post-dispersal weed seed predation in the field 22 Identification and quantification of possible insect seed predators 23 Feeding ability and weed seed preference under laboratory conditions 25 Discussion and Conclusions 26 Sources of Materials 31 v Acknowledgments 31 References 31 CHAPTER 3. GENERAL CONCLUSIONS 47 Conclusions 47 Recommendations for Future Research 48 Acknowledgments 49 Vl ABSTRACT Post-dispersal predation of common lambsquarters (Chenopodium album (Toum.) L.) and common waterhemp (Amaranthus tuberculatus (Moq.) Sauer.) seeds was evaluated in conventional, reduced and no-tillage regimes in Boone, IA. Glyphosate resistant com and soybean were planted in 2003 and 2004, respectively. The level of seed predation was quantified using different insect exclusion treatments. We also identified some of the potential seed predators in the field and their preference and consumption of weed seeds in laboratory experiments. We observed no consistent differences in common lambsquarters and common waterhemp seed predation among tillage regimes. The main predators of common lambsquarters and common waterhemp seeds were invertebrate organisms. The most abundant invertebrates captured in pitfall traps were field crickets ( Gryllus pennsylvanicus De Geer [Gryllidae, Orthoptera]) and a ground beetle (Harpalus pensylvanicus Burmeister [Coleoptera, Carabidae]). Under field conditions, there was a significant correlation between common lambsquarters and common waterhemp seeds predated and the activity-density of field crickets and ground beetles. Weed seed predation by insects can play an important role in plant population dynamics. Annual weed populations depend primarily on the soil seedbank. Therefore, the reduction of the weed seedbank, as a consequence of insect predation, might play an important role in reducing weed populations in the field. Understanding the impact that the activity-density of weed seed predators has on the weed seedbank can help determine the best management practices for lowering weed populations. CHAPTER I GENERAL INTRODUCTION Introduction Research on weed control and weed biology has increased over the years due to the evolution of herbicide resistance and adaptation to control practices. This allowed weeds to thrive in agronomic production systems, becoming one of the most important pests in agricultural fields (Buhler et al., 1997; Monaco et al., 2002). Weeds compete effectively for light, nutrients, and moisture with crops thus causing significant reductions in yields and negatively affecting crop production by increasing weed control costs (Liebman, 2001). Two weeds that have become economically important throughout the North Central Region of the United States are common waterhemp (Amaranthus tuberculatus (Moq.) Sauer.) and common lambsquarters (Chenopodium album (Toum.) L.). The success of these weeds is due to their adaptation to agronomic production and weed management systems, making them increasingly difficult to control (Buhler, 1995; Manley et al., 2001; Derksen et al., 2002; Locke et al., 2002). Common waterhemp is an annual weed that is native of the Midwestern United States. It has become one of the most problematic pest in soybean (Glycine max (L.) Merr.) (Mayo et al., 1995) and com (Zea mays L.) (Anderson et al., 1996b) fields in the last decade. Common waterhemp can reduce soybean yields by 43% (Hager et al., 2002) and up to 74% for com (Steckel and Spague, 2004). Several factors have helped common waterhemp become such a successful weed. It produces large numbers of small seeds (0.9-1.2 mm in diameter) (Stubbenddieck et al., 1995) that can be easily spread throughout the field by 2 water, wind, vertebrates or invertebrates, and machinery. In addition, Buhler and Hartzler (2001) observed that common waterhemp could remain viable after 4 years in the soil seedbank, indicating that it is a persistent seed. Another characteristic of common waterhemp is that its seed dormancy regulation is highly dependent on environmental conditions (Leon and Owen, 2003) and its seedling emergence period is longer than most weeds in the Midwest Region. Also, conservation and no-tillage have increased in soybean and com production, and they favor weed species that produce small seeds (Buhler, 1992). Another factor that has made common waterhemp such an important weed is the fact that many populations have evolved herbicide resistance. There are numerous reports of common waterhemp biotypes that are resistant to acetolactate synthase (ALS)-inhibiting herbicides (Horak and Peterson, 1995; Hinz and Owen, 1997; Foes et al., 1998) as well as triazine herbicides (Anderson et al., 1996a, 1996b) and protoporphyrinogen oxidase inhibiting herbicides (Shoup et al., 2003). Also, common waterhemp populations in Iowa, Illinois and Missouri have demonstrated variable response and consistently incomplete control to commercial doses of glyphosate, suggesting the initial evolution of resistance to this herbicide (Zelaya and Owen, 2000; Smeda and Schuster, 2002). Common lambsquarters is an annual weed widely distributed all over the world, and a frequent weed in Iowa com and soybean fields. There are several factors that make this weed difficult to control. For example, it is highly competitive, adaptive and capable of producing thousands of small seeds per plant (Harrison, 1990) that can remain viable in the soil for many years (Conn and Deck, 1995). Common lambsquarters is well adapted to current crop production systems such as crop rotation and reduced tillage systems (Thomas and Frick, 1993; Barberi and Mazzoncini, 2001; Shrestha et al., 2002). In addition, common 3 lambsquarters has evolved resistance to herbicides such as atrazine (Dekker and Burmester, 1989; Myers and Harvey, 1993). The fact that many problematic weeds have evolved resistance to herbicides reduces their effectiveness as a control tactic. Other control tactics must be used, in addition to herbicides, to develop an effective management program for these weeds. Tillage such as conventional tillage, reduced tillage, and no-tillage, can effectively complement other weed control tactics and improve integrated weed management programs. Different tillage regimes disturb the soil at different levels and thus change the soil surface, moisture, temperature, and affect weed emergence patterns and seedbanks (Buhler et al., 1997). For example, in conventional tillage, weed seed distribution is relatively uniform throughout the tillage profile after a period of time (Mohler, 1993). However, in reduced and no-tillage regimes, 60% of weed seeds remain in the upper 5 cm of soil surface (Clements et al., 1996). Conventional tillage has been a very common crop production practice. In this tillage regime, residues from previous crops are plowed into the soil, and weed seeds are thus concentrated near the depth of plowing after a single moldboard plow (Mohler, 1993; Hoffman et al., 1998; Buhler et al., 2001 ). Conventional tillage controls weeds by killing emerged weeds and by burying seeds to depths that prevent seed germination or successful seedling emergence (Monaco et al., 2002). Even though this tillage regime controls weeds, it also increases water depletion and soil erosion (Monaco et al., 2002). Therefore, farmers are using reduced and no-tillage to prepare the soil in order to minimize problems. In reduced tillage, more crop residue

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