Factors affecting the attack rate of Bemisia tabaci on cucumber

Abstract

-The objective of this work was to determine the effects of rainfall, temperature, predators, parasitoids, plant age, leaf chemical composition, levels of leaf nitrogen and potassium, besides density of leaf trichomes, on attack intensity of Bemisia tabaci biotype B on the Cucumis sativus. An increase in the number of whitefly adults and nymphs per leaf was observed with plant aging. A higher number of whitefly adults per leaf and eggs cm -2 was verified in the apical part than in the middle and bottom part of the plants canopy. However, the higher number of whitefly nymphs was observed in the mid-part than in the apical and bottom part of the plant canopy. The incidence of whitefly nymphs was negatively affected with foliar nitrogen. Pentacosane and octacosane positively affected whitefly adults and the first compound also affected the nymphs of this pest species.Index terms: Cucumis sativus, whitefly, allelochemicals, nitrogen, trichomes. Fatores que afetam o ataque de Bemisia tabaci em pepinoResumo -O objetivo deste trabalho foi determinar os efeitos de pluviosidade, temperatura, predadores, parasitóides, idade de planta, composição química foliar, níveis de nitrogênio e potássio foliares, assim como de densidade de tricomas, na intensidade de ataque de Bemisia tabaci biótipo B em Cucumis sativus. Observaram-se maiores números de adultos e de ninfas de mosca-branca por folha com o aumento de idade de plantas. Adultos por folha e ovos cm -2 foram encontrados com maior freqüência na parte apical do que na parte mediana e basal do dossel das plantas. Entretanto, observou-se maior número de ninfas desse inseto no terço mediano do que nos terços apical e basal. Nitrogênio foliar afetou negativamente ninfas de mosca-branca. Pentacosano e octacosano afetaram positivamente adultos e o primeiro composto afetou também as ninfas dessa praga.

Morphological Identification of Aphid Species Infesting Some Ornamental plants in Taif Governorate

“…(Kamel and Gengaihi 2009) cited that total flavonoids group that is considered as a secondary plant metabolite had no biological activity either as anti-feedant or as repellant to different cucumber sap sucking insects. (Leite et al 2006) demonstrated that plant chemical composition, levels of nitrogen and potassium beside density and structure of leaf trichomes can affect on intensity of pest attack.…”

Incidence of cotton whitefly Bemisia tabaci (Gennadius, 1889) (Hemiptera: Aleyrodidae) infesting cucumber (Cucumis sativus L.) cultivars with reference to cultivar susceptibilities

“…Populations of whitefly increased with increasing temperatures and decreasing relative humidity (MAKLAD et al 2012, HANAFY et al 2014. A non-significant effect of temperature and rainfall was recorded on the occurrence of B. tabaci on cucumber by LEITE et al (2006). EL-LAKWAH et al (2011) indicated that the mean temperature had a significant effect on B. tabaci populations, but that RH% had no significant effect.…”

The impact of cucumber nitrogen nutrition on life history traits of Tetranychus urticae (Koch) (Acari: Tetranychidae)

“…Mites tend to feed on well-watered host plants (Sadras et al, 1998). Moreover, it is known that higher nitrogen concentration commonly contributes to an increase in leaf area and a reduction in trichome density of leaves (Kerpel et al, 2006;Leite et al, 2006;Haghighi et al, 2011). So, these characteristics may improve TSSM activities (Alba et al, 2009), because it is difficult for mites to settle on leaves which have a great density of trichomes.…”