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J. Farías-Larios, M. Orozco-Santos, and N.R. Ramírez-Vazquez

Bemisia argentifolii is a major pest of melon crop in key production areas of Mexico. Foliar applications of chemical insecticides for their management have been ineffective. The purpose of this research was to evaluate the use of commercial formulations of Beauveria bassiana and different rates for biological control of silverleaf whitefly in cantaloupe melon grown under tropical conditions. Experimental plots were treated with three rates of Mycotrol ES and only an of Naturalis-L or Endosulfan as conventional insecticide. Treatments were arranged in a randomized complete-block design with four replicates. Effects of the treatments on B. argentifolii larval and adult populations and the amount of damage to the foliage and yield melon were recorded. There was not a significant difference between Mycotrol ES rates in nymphs and adults killed. Mycotrol ES, Naturalis and Endosulfan have a similar effect on nymphs and adults control. The nontreated control melon plants had significantly greater number of silverleaf whitefly nymphs and adults than Mycotrol ES, Naturalis-L and Endosulfan treatments. Also, marketable yield was lower for the nontreated control melon plants due to higher whitefly infestations. Results from this study indicate that B. bassiana use resulted in consistently lower whitefly infestations compared to the control. The field results are promising and confirmed the potential of B. bassiana as a microbial control agent against B. argentifolii in melon crop under tropical conditions.

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Charles G. Summers, Albert S. Newton Jr., and Kyle R. Hansen

Six table grape (Vitis vinifera L.) cultivars and 10 species of tree fruit were evaluated in cage tests to determine their susceptibility to colonization by the silverleaf whitefly (Bemisia argentifolii Bellows and Perring). The table grape cultivars Thompson Seedless, Perlette, Flame Seedless, Ruby Seedless, Christmas Rose, and Redglobe were all colonized. In a field nursery, with naturally occurring silverleaf whitefly populations, `Zinfandel', `Sirah', and `Chardonnay' were more heavily colonized than were `Merlot', `Thompson Seedless', or `Redglobe'. The tree crops `Kerman' pistachio (Pistacia vera L.), `Calimyrna' fig (Ficus carica L.), `Nonpareil' almond [Prunus dulcis (Mill.) D.A. Webb], and `Fuyu' persimmon (Diospyros kaki L.) were colonized in cage tests. Silverleaf whitefly failed to establish colonies on caged `O'Henry' peach [Prunus persica (L.) Batsch.], `Fantasia' nectarine [P. persica (L.) Batsch. var. nectarina (Ait.f.) Maxim.], `Casselman' plum (P. salicina Lindl.), `Tilton' apricot (P. armeniaca L.), `Granny Smith' apple (Malus domestica Borkh.), and `Hayward' kiwifruit [Actinidia delicoisa (A. Chevalier) C.F. Liang et A.R. Ferguson].

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Barbara E. Liedl, Darlene M. Lawson, Kris K. White, Joseph A. Shapiro, William G. Carson, John T. Trumble, and Martha A. Mutschler

Acylsugars, the primary components of the exudate secreted by type IV trichomes of Lycopersicon pennellii (Corr.) D'Arcy LA716, mediate the resistance of this accession to silverleaf whitefly, Bemisia argentifolii Bellows & Perring, n. sp. Reduction in the settling of the adult silverleaf whiteflies correlates with the concomitant increase in applied acylsugars. Oviposition of B. argentifolii is also affected by acylsugars, resulting in a reduction in the number of eggs and nymphs found; however, acylsugars do not affect hatching of nymphs. The threshold amount of acylsugars required for deterring settling and oviposition is under the amount of acylsugars (50 to 70 μg·cm–1) required for control of other insects.

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A.A. Csizinszky and D.J. Schuster

Field studies were conducted for three seasons, Fall 1994, Spring 1995, and Fall 1995 on the effect of UV-reflective films (mulches) on fruit yields and on the silverleaf whitefly [Bemisia argentifolii (Bellows and Perring)] of staked, fresh-market tomatoes (Lycopersicon esculentum Mill). The UV-reflective mulches were metallized aluminum (ALU) and painted aluminum (PAL) on either black or white plastic film. The AL and SL mulches were evaluated with and without a white (fall) or black (spring) 25-cm-wide painted band in the bed center. Controls were the conventional white (fall) or black (spring) polyethylene mulches. Highest reflected energy (μmol·m–2·s–1) to the plants at 25 cm from the mulch surface was measured on the ALU without white painted band or on PAL on white or black mulch with white painted band. Lowest energy was reflected from the white or black controls. Whitefly populations in the fall were lower on the ALU than on the PAL mulches. In the spring, when whitefly populations were low, number of whiteflies on tomato leaves were similar with all treatments. The proportion of plants with symptoms of the silverleaf whitefly transmitted tomato mottle virus (TMoV) were highest on controls. Yields in the fall were similar with UV-reflective or with white mulch. In the spring, fruit size and marketable yields were greater (P < 0.05) on plants with PAL on white plastic film without black band than on black control.

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Cindy L. McKenzie and Joseph P. Albano

viruses have all appeared for the first time in Florida since the introduction of biotype B ( Blair et al., 1995 ; Kring et al., 1991 ). Biotype B was described in 1994, although not universally accepted as a new species, Bemisia argentifolii , or

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Kristen Young and Eileen A. Kabelka

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 on maturation

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M. Marutani, L. Yudin, D. Nafus, F. Cruz, and V. Santos

The outbreak of a new whitefly was first reported in Summer 1993 at two sites in the southern part of Guam. Vegetable crops heavily damaged by this pest included cucumber, yardlong beans, and tomato. At present, the whitefly is found infesting tomato, eggplants, cucumbers, watermelon, and other vegetable crops throughout the island. The whitefly was identified as Bemisia argentifolii with the characteristics of a wide host range and the presence of silvering leaves on cucurbits. A larval parasitoid was recovered from eggplant and tomato leaves. The efficacy of pesticides against the pest is being investigated.

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Mark W. Farnham and Kent D. Elsey

Resistance of a Brassica oleracea germplasm collection (broccoli, Italica Group; cauliflower, Botrytis Group; and collard and kale, Acephala Group) to silverleaf whitefly (SLW; Bemisia argentifolii Bellows and Perring) infestation was evaluated using several measures of insect infestation (including adult vs. nymph counts) taken at plant growth stages ranging from seedling to mature plant. An initial study was conducted in an outdoor screen cage artificially infested with the SLW adults; subsequent field trials relied on natural infestations. The glossy-leaved lines (`Broc3' broccoli, `Green Glaze' collard, and `SC Glaze' collard) had low SLW infestations in cage and field tests. SLW adult counts were less variable than similar comparisons using nymphal counts, although adult and nymph counts were positively and significantly correlated at late plant stages. Based on this study, comparing relative SLW adult populations would be a preferred criterion for identifying B. oleracea resistance to this insect.

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C.S. Vavrina, P.A. Stansly, and T.X. Liu

Household detergents were evaluated in field studies on fresh-market tomato (Lycopersicon esculentum Mill.) for insecticidal and phytotoxic effects. Laboratory bioassays were used to examine the toxicity of a household liquid dish detergent on small nymphs of silverleaf whitefly, Bemisia argentifolii Bellows and Perring. The detergents tested proved to be more toxic to whitefly nymphs than the commercial insecticidal soap. Detergent treatments were applied to tomato with a commercial high pressure hydraulic sprayer at 0%, 1%, 2%, 4%, and 8% (by volume) initially and at 0%, 0.25%, 0.5%, 1.0%, and 2.0% (by volume) in subsequent tests. As detergent rate, frequency of application, or both increased, plant dry weight accumulation and fruit yield decreased. Applying detergent also increased time to fruit maturity. A once-a-week application of 0.25% to 0.5% detergent initially applied 2 weeks after transplanting alleviated phytotoxicity and yield reduction problems.

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Robert P. Rice Jr. and Michael Crane

Twenty-four poinsettia cultivars (Euphorbia pulcherrima) were exposed to a population of greenhouse whitefly (Trialeurodes vaporariorum) and silverleaf whitefly (Bemisia argentifolii) for 6 weeks. Evaluation was based on the number of immature whitefly present on each of the marked leaves. The poinsettias that produce white bracts were more heavily infested with immature stages of whitefly than those cultivars that produce red bracts, while those that produce pink bracts were intermediate. There was a wide range in degree of whitefly infestation among poinsettia cultivars. Leaf trichome density also explained a portion of the variance in whitefly oviposition rates among several of the cultivars. Cultivars with high trichome densities sustained less whitefly oviposition than did cultivars with low trichome densities. Certain cultivars tested showed an appreciable natural resistance to whitefly (`Freedom Red', `Freedom Bright Red', `Red Velvet', `Cranberry Punch', `Pepride').