Localized migration and dispersal by the sweet potato whitefly, Bemisia tabaci

Abstract

Laboratory populations of the sweet potato whitefly, Bemisia tabaci, have been shown to consist of both migratory and trivial flying morphs. The behavior of these forms as part of the process of short-range migration was examined under field conditions. Insects were marked in a field of melons using fluorescent dust during two consecutive growing seasons. During the first growing season, passive traps used to collect living whiteflies, were placed along 16 equally spaced transects radiating from the field to a distance of up to 1.0 km. Wind out of the north-east consistently carried migrating whiteflies to traps placed along transects in the south-western quadrant because cold air drainages dictate wind direction during early morning hours in the desert South-west. For this reason, during the second season traps were laid out over fallow ground in a rectangular grid extending 2.7 km to the south-west of the marked field. If dispersal was entirely passive, patterns could be described using a diffusion model. Statistical examination of the data, howèver, demonstrated that the distribution on all days was patchy. Geostatistical techniques were used to describe the observed patchiness. Traps in the immediate vicinity of the marked field caught more whiteflies than the daily median. Large numbers were also collected from near the periphery of the grid. White-flies were far less prevalent in the grid's center. As a result, the distribution of captured whiteflies can be described as bimodal. These patterns confirm behavior observed in the laboratory, i.e., a portion of the population are trivial fliers that do not engage in migration and are consequently captured in traps near the field, and a portion initially respond to cues associated with skylight, ignoring cues provided by the ground, and fly for a period of time before landing in distant traps. During both years movement out of the field had an exaggerated directional component on 13 of 14 days.

Selectivity of Whitefly Traps in Cotton for Eretmocerus eremicus (Hymenoptera: Aphelinidae), a Native Parasitoid of Bemisia argentifolii (Homoptera: Aleyrodidae)

“…The increasing unsuitability of the cotton as a feeding site may also have increased local flight activity of adult whiteflies and increased the chances of their flying onto the colorless traps in their flight path. Byrne et al (1996) have shown that factors such as crop drydown can change the response to visual spectral cues and subsequent flight behavior of B. argentifolii. This may explain the lack of decreasing trap catches on the colorless traps.…”

Aleytrap: An instrumentation to handle adult whitefly, Bemisia tabaci, Gennadius

“…Rangaraju and Chenulu (1980) initiated the efforts to overcome this problem, describing an effective method to count adult whiteflies on crops under field conditions by covering the sample plant with a bell jar of a height according to the respective crops, however, the time consumption is too much in this method. Apart from the bell jar and leaf turn method, the yellow sticky traps (Lloyd, 1921), muffin fan traps (Byrne et al, 1996) and CC-Trap consisting of transparent disposable cup (Chu and Henneberry, 1998) have also been developed but none of these can be used in counting per plant population in scientific experiments. Some attempts made by different authors to count adult whiteflies by employing various methods on different host plants are listed in Table 1.…”

“…Yellow sticky trap (Chu and Henneberry, 1998) and muffin fan trap (Byrne et al, 1996) are also in use but they help only in providing the information on natural occurrence of aleyrodid adults in a particular cultivated area, besides yellow sticky traps which also capture other insects having fondness of yellow color (Chu and Henneberry, 1998). Chu and Henneberry (1998) has developed a new trap (CC Trap) consisting of transparent disposable cup and proved its superiority over yellow sticky trap but these traps cannot count the per plant population of whitefly adults on their respective host plants.…”

Large-scale, spatially-explicit test of the refuge strategy for delaying insecticide resistance

“…When suitable crops are present, most individuals move within fields or short distances from fields, whereas ∼6% move 2-3 km from source fields (21)(22)(23). In simulation modeling that incorporated this dispersal dimorphism, refuges of cotton and other whitefly host plants delayed B. tabaci resistance, whereas pyriproxyfen-treated cotton accelerated the evolution of resistance (24).…”