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A. A. Csizinszky and D. J. Schuster

Two insecticidal spray frequencies, 0 and 3x per week, against the sweetpotato whitefly, Bemisia tabaci Gennadius, were evaluated at three K rates, 190, 380 and 760 kg.ha-1, for their effect on whitefly population, fruit yield and incidence of irregular ripening on tomato, Lycopersicon esculentum Mill., cv. Sunny. Whitefly populations were reduced with three weekly sprays, but not by K rates. Early yields were best with three weekly sprays and with the highest K rate. For the season, yield of extra large (≥ 70 mm diameter) fruit was reduced with three weekly sprays and with increasing K rates. Proportions of irregularly ripened fruits were similar with either spray frequency, but were reduced at the highest K rate.

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R.W. McMahon, R.K. Lindquist, B.D. Baith, T.L. Makin, and M.L. Casey

A 2-year demonstration study was conducted to compare the effectiveness of two sources of Encarsia formosa (EF) on the biological control of the sweetpotato whitefly (SPWF) (Bemisia tabaci Gennadius) on poinsettias (Euphorbia pulcherrima Wild.). Commercially produced EF were raised on the greenhouse whitefly (GHWF) (Trialuerodes vaporariorum Westwood), while the locally produced EF were raised on the SPWF. Results showed that SPWF populations were reduced considerably both years, and maximum nymph parasitism ranged from 60% to >80%. No large differences were observed in the ability of EF to control SPWF populations whether raised on SPWF or GHWF nymphs. This study suggests that there is potential for controlling SPWF populations on poinsettia by EF in conjunction with an integrated pest management (IPM) program.

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Monica Ozores-Hampton, Philip A. Stansly, and Eugene McAvoy

from the center part of the plot three times on 7, 22, and 29 May 2007 (66, 91, and 98 DAT) and 7, 21, and 30 Apr. 2008 (93, 107, and 116 DAT). Evaluations. Sweetpotato whitefly populations were monitored weekly in 2007 and 2008 by carefully inverting

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Harry S. Paris, Peter J. Stoffella, and Charles A. Powell

`Striato d'Italia' (cocozelle group) and `Clarita' (vegetable marrow group) summer squash were grown in the greenhouse and field in the presence of sweetpotato whiteflies (Bemisia tabaci Germ.) and their susceptibility to leaf silvering was compared. Silvering was less severe in `Striato d'Italia' in the greenhouse and field.

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Prabin Tamang, Kaori Ando, William M. Wintermantel, and James D. McCreight

season melon production (for October–December harvest) in Arizona and the southern inland portions of California (Imperial Valley, Coachella Valley and Palo Verde Valley) have been devastated by the combination of sweetpotato whitefly ( Bemisia tabaci

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K.D. Elsey and M.W. Farnham

The relative resistance of 18 cultivars of Brassica oleracea L. to attack by the sweetpotato whitefly [Bemisia tabaci (Gennadius)] was studied in screen cage (spring), field (autumn), and laboratory tests. The B. oleracea entries consisted of six types, including 16 green and two red cultivars. Cabbage (Capitata Group) and broccoli (Boytrytis Group) were less infested than other crops in a screen cage test, with kale, collard (Acephala Group), and brussels sprouts (Germmiter Group) experiencing relatively high and kohlrabi (Gongtlodes Group) intermediate infestations. Relative ranking of crops was similar in an autumn field study, with the exception of brussels sprouts, which had an intermediate level of infestation. Differences in numbers of whiteflies among cultivars within crops were negligible or inconsistent, except that red cultivars of brussels sprouts (`Rubine') and cabbage (`Red Acre') were much less infested than green cultivars. In a laboratory test, differences of whitefly oviposition and nymphal survival and development were small, indicating that nonpreference factors, rather than antibiosis, are the best explanations for differences in the numbers of whiteflies among the B. oleracea cultivars that were tested,

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James D. McCreight

Lettuce infectious yellows virus (LIYV), transmitted by the sweetpotato whitefly, (Bemisia tabaci Genn.), seriously affected melon (Cucumis melo L.) production in the lower desert areas of the southwest United States from 1981 through 1990. Melon plant introduction (PI) 313970 was previously found resistant to LIYV in naturally infected field tests and controlled-inoculation greenhouse tests. Data from F1 and segregating generations from crosses of PI 313970 with LIYV-susceptible lines indicated that resistance in this accession is conditioned by a dominant allele at a single locus designated Lettuce infectious yellows (Liy).

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Aliya Momotaz, Jay W. Scott, and David J. Schuster

Tomato is widely grown and economically one of the most important vegetable crops worldwide, with a value of over $1.4 billion in the United States alone ( USDA, 2008 ). Biotype B of the sweetpotato whitefly (SPWF), also known as the silverleaf

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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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Samuel F. Hutton, Jay W. Scott, and David J. Schuster

by the sweetpotato whitefly, Bemisia tabacai (Genn.). Yield losses resulting from this virus have been severe ( Polston and Anderson, 1997 ), and this disease is the major limiting factor in tomato production for many areas ( Lapidot and Friedmann