HORTICULTURAL ENTOMOLOGY Effect of Silver Reflective Mulch and a Summer Squash Trap Crop on Densities of Immature Bemisia argentifolii (Homoptera: Aleyrodidae) on Organic Bean HUGH ADAM SMITH, ROSALIE LYNNE KOENIG, 1 HEATHER JANE MCAUSLANE, AND ROBERT MCSORLEY Department of Entomology and Nematology, University of Florida, Gainesville, FL 32611 J. Econ. Entomol. 93(3): 726Ð731 (2000) ABSTRACT Polyethylene mulch with a reßective silver stripe and a yellow summer squash, Cucurbita pepo L., trap crop were tested alone and in combination as tactics to reduce densities of Bemisia argentifolii Bellows & Perring eggs and nymphs, and incidence of bean golden mosaic geminivirus on snap bean, Phaseolus vulgaris L. Egg densities were consistently higher on squash than on bean, but egg densities and virus incidence were not lower on bean grown with squash than on bean grown in monoculture. Silver reßective mulch reduced egg densities compared with bean grown on bare ground during the Þrst week after crop emergence for 2 of the 3 yr that the study was conducted. However, egg suppression by silver mulch was not enhanced by the presence of a squash trap crop when both tactics were combined. The obstacles to suppressing B. argentifolii through the use of trap crops are discussed. KEY WORDS pest management, intercropping, polyculture, cultural control, geminivirus, vector management Bemisia argentifolii BELLOWS &PERRING, also known as the B strain of Bemisia tabaci (Gennadius), has be- come a serious pest of horticultural and agronomic crops throughout warm regions of the world (Brown et al. 1995). In addition to causing mechanical damage, B. argentifolii has been associated with several new plant disorders, and dozens of new geminiviruses (Pol- ston and Anderson 1997). In 1993, bean golden mosaic virus, vectored by B. argentifolii, reached epidemic proportions for the Þrst time in Florida (Blair et al. 1995), the foremost producer of snap bean (Phaseolus vulgaris L.) in the United States (National Agricultural Statistics Service 1998). Bemisia has developed resis- tance to most classes of pesticides (Dittrich et al. 1990, Denholm et al. 1996), forcing conventional growers to seek nonchemical alternatives for Bemisia manage- ment. The systemic insecticide imidacloprid (Bayer) is currently effective for controlling B. argentifolii (Polston et al. 1994), but is not an option for organic growers, who face special challenges in the manage- ment of virus vectors. Reßective plastic mulches contribute to whiteßy management programs by providing early-season pro- tection from whiteßy-vectored viruses (Suwwan et al. 1988, Kring et al. 1990, Csizinsky et al. 1999). Whiteßy adults are apparently repelled by UV wavelengths reßected by silver and aluminum pigments on the plastic mulch (Stansly and Schuster 1999). However, reßective mulches tend to lose their efÞcacy as shade from the crop canopy increases (Csizinsky et al. 1997). Reßective mulches alone do not provide sufÞcient protection from whiteßy damage (Schuster et al. 1989), and so have been tested in combination with other tactics such as pesticides (Powell and Stofella 1993, Natwick and Mayberry 1994). Bemisia argentifolii has demonstrated differential rates of oviposition on various hosts (Blua et al. 1995, Chu et al. 1995, Tsai and Wang 1996). Certain hosts have been tested as trap crops for management of B. argentifolii because of these apparent crop prefer- ences. The results of trap cropping with soybean (Glycine max L., McAuslane et al. 1995), melon (Cu- cumis melo L., Perring et al. 1995), and WrightÕs ground cherry (Physalis wrightii Gray, Ellsworth et al. 1994) have been inconclusive. However, Schuster et al. (1996) delayed the onset of Bemisia-transmitted virus by intercropping tomato, Lycopersicon esculen- tum Mill., with squash, Cucurbita pepo L. In addition, Al-Musa (1982) reduced levels of B. tabaci nymphs and the onset of tomato yellow leaf curl symptoms by intercropping tomato with cucumber, Cucumis sa- tivus L. The current study was conducted as part of an effort to Þnd methods for managing B. argentifolii that are suitable for organic growers. Silver reßective mulch and a squash trap crop were tested alone and in com- bination to determine their effect on virus incidence, yield, and densities of immature B. argentifolii on snap bean compared with bean grown in monoculture on bare ground. We hypothesized that squash might draw 1 RosieÕs Organic Farm, Gainesville, FL. 0022-0493/00/0726Ð0731$02.00/0  2000 Entomological Society of America Downloaded from https://academic.oup.com/jee/article/93/3/726/2217198 by guest on 01 January 2023