Crop Protection 21 (2002) 921–928 Use of UV reflective mulch to delay the colonization and reduce the severity of Bemisia argentifolii (Homoptera: Aleyrodidae) infestations in cucurbits Charles G. Summers a, *, James J. Stapleton b a Department of Entomology, University of California, One Shields Avenue, Davis, CA 95616, USA b Kearney Agricultural Center, Statewide IPM Project, 9240 S. Riverbend Avenue, Parlier, CA 93648, USA Received 2 January 2002; received in revised form 26 March 2002; accepted 29 March 2002 Abstract Effectiveness of UV reflective plastic mulch for the management of silverleaf whitefly (Bemisia argentifolii Bellows and Perring) was evaluated in selected cucurbits. The reflective mulch repelled silverleaf whitefly adults in pumpkin (Cucurbita maxima Duchesne), cucumber (Cucumis sativus L.) and zucchini squash (Cucurbita pepo L.). Reduced colonization by B. argentifolii adults resulted in reduced populations of nymphs and a delay and reduction in the incidence of silverleaf in pumpkin and zucchini squash. Reflective mulch was as effective in reducing nymphal B. argentifolii populations as was a pre-plant soil application of imidacloprid. Zucchini squash, pumpkin and cucumber yields were significantly higher in plants grown over reflective mulch than in those grown over unmulched soil. Zucchini squash yields from plants grown over reflective mulch also were higher than from plants grown in plots receiving a pre-plant application of imidacloprid. This study confirmed that UV reflective plastic mulch can be used to manage B. argentifolii and the mulches give protection equal to that provided by imidacloprid. r 2002 Elsevier Science Ltd. All rights reserved. Keywords: Bemisia argentifolii; Reflective mulch; Cucurbits; Imidacloprid 1. Introduction Silverleaf whitefly (Bemisia argentifolii Bellows and Perring) is a serious pest of cucurbits including zucchini squash (Cucurbita pepo L.), cucumber (C. sativus L.), and pumpkin (Cucurbita maxima Duchesne). Whitefly management through chemical application has not been particularly effective (Denholm et al., 1996; Horowitz and Ishaaya, 1996) and B. argentifolii has the potential to rapidly develop resistance to all classes of insecticides (Horowitz and Ishaaya, 1996; Denholm et al., 1996; Prabhaker et al., 1998; Elbert and Nauen, 2000). While some success in reducing whitefly densities with pre- dators and parasitoids has been reported in protected culture (Hoddle and Van Driesche, 1999; Liu and Stansly, 1999) there are few examples of effective field level biological control in vegetable cropping systems (Heinz, 1996; Hoelmer, 1996). UV reflective mulches have been used successfully to reduce and delay the buildup of aphids and the incidence of aphid-borne virus diseases in many vegetable crops by reducing the incidence of alate aphids alighting on the plants (Chalfant et al., 1977; Conway et al., 1989; Brown et al., 1993; Summers et al., 1995). Results of the effectiveness of reflective mulches in repelling whiteflies, however, have been mixed. Webb and Linda (1992), while finding fewer alate aphids on squash plants grown over white mulches than on plants grown over bare soil, found no differences in the number of adult B. tabaci (Gennadius) on plants grown over either surface. Powell and Stoffella (1993) reported that numbers of B. tabaci collected on yellow sticky traps placed above squash and tomato plants were not reduced in plants growing over polyethylene mulches coated with reflective aluminum paint compared to those growing over non-UV reflective, black polyethy- lene. They also found no significant differences in the *Corresponding author. Tel. +1-559-646-6564; fax: +1-559-646- 6593. E-mail addresses: chasum@uckac.edu (C.G. Summers), jim@uck- ac.edu (J.J. Stapleton). 0261-2194/02/$ - see front matter r 2002 Elsevier Science Ltd. All rights reserved. PII:S0261-2194(02)00067-4