Association of the Sweetpotato Whitefly with a Silverleaf Disorder of Squash

Abstract

<jats:p>The sweetpotato whitefly, <jats:italic>Bemisia tabaci</jats:italic> (Gennadius), was associated with symptoms of a silverleaf disorder of acorn squash <jats:italic>(Cucurbita pepo</jats:italic> L. cvs. Table King Bush and Table Ace) in cage studies in the greenhouse. Symptoms appeared on uninfested leaves that developed after plants were infested with the whitefly. When the infested lower leaves were removed and the young leaves protected from infestation with insecticides, new growth was asymptomatic or nearly so and symptomatic leaves remained symptomatic. Symptom expression was related more to nymphal density than to adult density since the relationship between log nymph density and symptoms was linear when adult densities were equal.</jats:p>

Diversity in landraces of summer squash from Jordan

“…Significant negative associations of leaf silvery with stem colour, number of pistillate flowers and number of fruits per plant were obtained. These associations agreed with the observations of Schuster et al (1991) who reported that stem and fruit colour appear to be lighter than usual in leaf silvering plants. Increasing intensity of leaf silvering resulted in increasing number of staminate flowers per plant (r = 0.27, p = 0.001) and in decreasing number of pistillate flowers per plant (r = -0.13, p = 0.04) and fruit number per plant (r = -0.18, p = 0.04) which consequently resulted in yield reduction (Burger et al, 1988).…”

“…On the other hand, it was believed that silvery leaf acts as repellant to aphids and thus lowers the incidence of virus disease (Shifriss, 1981;Davis & Shifriss, 1983). Although the silvery leaf trait is genetically controlled (Scarchuck, 1954;Shifriss, 1982;Burger et al, t988), several environmental factors induce leaf silvering including atmospheric pollution (Simons et al, 1988) water stress (Burger et al, 1988;Paris et al, 1987) or toxins released from sweetpotato whitefly breeding activity Paris et al, 1993;Schuster et al, 1991); Yokomi et al, 1990). The variability of the leaf silvery trait in landraces is possibly under genetic Control, since all plants of the check cultivars showed complete leaf silvering.…”

Characterization of antibiosis and antixenosis to the whitefly silverleaf Bemisia tabaci B biotype (Hemiptera: Aleyrodidae) in several squash varieties

“…Squash leaf silvering is a physiological disturbance induced by the feeding of B. tabaci B biotype whitefly nymphs. Starting at leaf veins, it spreads out covering the entire foliar surface (Burger et al 1983;Paris et al 1987;Simons et al 1988;Schuster et al 1991), and the same happens with branches and fruits (Simons et al 1988). Besides increasing light reflection, silvering reduces the chlorophyll content of the leaves causing a decrease in crop yield (Burger et al 1988).…”

Identification of molecular markers associated with resistance to squash silverleaf disorder in summer squash (Cucurbita pepo)

“…Severely symptomatic plants can exhibit stunting and yield reduction (Jimenez et al 1995;Simons et al 1988). The symptoms of SSL disorder are induced by feeding immature nymphs of the silverleaf whitefly [Bemisia argentifolii (formerly known as Bemisia tabaci Gennadius, B strain)] (Costa et al 1993;Schuster et al 1991). Silvering symptoms are expressed on new leaves upon maturation distal to the site of the nymph feeding (Jimenez et al 1995;Schuster et al 1991).…”

“…The symptoms of SSL disorder are induced by feeding immature nymphs of the silverleaf whitefly [Bemisia argentifolii (formerly known as Bemisia tabaci Gennadius, B strain)] (Costa et al 1993;Schuster et al 1991). Silvering symptoms are expressed on new leaves upon maturation distal to the site of the nymph feeding (Jimenez et al 1995;Schuster et al 1991). The expression of symptoms is dependent on density of nymphs present, level of environmental stress, and cultivar (Paris et al 1993a).…”