Influence of Cover Crop and Intercrop Systems onBemisia argentifolli(Hemiptera: Aleyrodidae) Infestation and Associated Squash Silverleaf Disorder in Zucchini

Abstract

Field experiments were conducted to evaluate the effects of cover cropping and intercropping on population densities of silverleaf whitefly, Bemisia argentifolli Bellow and Perring, and the incidence of squash silverleaf disorder (SSL) in zucchini, Cucurbita pepo L., in Oahu, HI. Two cover crops, buckwheat (BW), Fagopyrum esculentum Moench, and white clover (WC), Trifolium repens L., or sunn hemp (SH), Crotolaria juncea L., and an intercropped vegetable, okra, Abelmonchus esculentus L., were evaluated during the 2003, 2005, and 2006 growing seasons, respectively. Population densities of whiteflies and SSL severity varied during the three field experiments. In 2003, the severity of SSL and percentage of leaves displaying symptoms were significantly lower on zucchini plants in WC than BW plots throughout the crops' growth cycle. Additionally, the percentage of leaves per plant displaying SSL symptoms was significantly greater in bare-ground (BG) compared with the pooled BW and WC treatments on each inspection date. In 2005, zucchini intercropped with okra had lower numbers of adult whiteflies and resulted in significantly lower severity of SSL than pooled BW and WC treatments. During 2006, zucchini grown with SH had significantly lower numbers of all whitefly stages (i.e., egg, immature, and adult) and less SSL severity symptoms than BW. Despite these differences in whitefly numbers and SSL severity, marketable yields were not significantly lower in BW compared with WC or SH treatment plots during the study. The mechanisms underlying these results and the feasibility of using cover crops and intercrops to manage B. argentifolli and SSL are discussed.

Growth and yield of zucchini squash (Cucurbita pepoL.) as influenced by a sunn hemp living mulch

“…This was shown in a similar study where yields of zucchini plants inter-planted into a buckwheat (Fagopyrum esculentum Moench) and white clover (Trifolium repens L.) living mulch were significantly higher than in monoculture plots (Manandhar et al 2009;. …”

“…Companion plants have been shown to reduce pest populations and damage by functioning as physical barriers, camouflaging host plants and deterring pest colonization (Hooks et al 1998;Boucher & Durgy 2004;Frank & Liburd 2005;Cavanagh et al 2009;Manandhar et al 2009). Additionally, several studies have shown that the companion planting tactic can be effectively used to delay the onset of insect caused plant diseases and phytotoxemias in cucurbit crops (Frank & Liburd 2005;Nyoike et al 2008;Manandhar & Hooks 2011).…”

“…Conversely, zucchini fruit yield was significantly greater in SH than in BG plots at the Queenstown site. Several studies have shown the benefits of sunn hemp regarding pest suppression of weeds, insects and diseases (Collins et al 2008;Manandhar et al 2009;Manandhar & Hooks 2011;Marahatta et al 2012). For these reasons, inter-planting zucchini squash into sunn hemp may be recommended as a means to help manage pests associated with zucchini plantings.…”

Sustainable Horticultural Systems

“…), lady beetles, lacewings, spiders, assassin bugs, minute pirate bugs, and ground beetles. Careful timing of the planting of insectary plants can help enhance population densities of predatory insects or insect parasitoids that could result in a reduction of insect transmitted viral diseases (Mandanhar et al 2009). …”

Impact of crimson clover dying mulch on two eggplant insect herbivores

“…Cover crops are well known and used for their ability to increase soil quality features but their potential use as a tool to help suppress insect pest populations is less recognized. However, cover crops in the form of plant diversification can be used to help mitigate problems associated with insect pests, directly through reduced colonization (Frank and Liburd 2005) and indirectly by decreasing the occurrence of insect caused plant viruses and phytotoxemias (Hooks and Fereres 2006;Manandhar et al 2009). Cruciferous crops are probably the most studied plants with respect to evaluating the impact of plant mixtures on insect population dynamics (Hooks and Johnson 2003).…”