Simulating the location of Bemisia tabaci biotype B (Hemiptera: Aleyrodidae) nymphs on tomato plants

The distribution of herbivorous insects within plants is expected to be correlated with the distribution of plant characteristics associated with high survival probabilities. For instance, oviposition and feeding site selection of the Silverleaf Whitefly (SLWF), Bemisia tabaci biotype B, is known to be driven by nitrogen content, microclimate and concentration of phagostimulants. We hypothesize that the relatively invariant distribution of nitrogen content and phagostimulants within tomato plants makes feasible the development of an algorithm to simulate the spatial distribution of SLWF immatures on virtual tomato plants. We developed an algorithm that relies on the probability of infestation per node, leaf sector and within the leaflet area to generate the location of a given number of SLWF nymphs on virtual tomato plants. To estimate the probabilities of infestation, different numbers of SLWF adults were released on individual plants and the resulting number of nymphs per leaflet was counted. The infested leaflets were scanned to record the location of each nymph within the leaflet area. We found that distribution of probabilities of infestation among plant nodes is described well by a beta-binomial distribution. Within leaves, nymph counts among leaflets were described well by a negative-binomial distribution and the spatial pattern within the leaflet area was described using the distribution of distances from each nymph to the midrib. The algorithm was validated using field data from the literature. The use of simulated nymph locations within plants is discussed in light of its application for the appropriate selection of biocontrol agents.