Print PageThe gypsy moth, Lymantria dispar, is a voracious defoliator of hardwood trees. One method of controlling this pest uses the naturally-occurring baculovirus LdNPV, which kills and liquefies larvae. To effectively use this virus as a biocontrol agent, it is necessary to know how likely it is that gypsy moths might develop resistance to it. For disease resistance to spread, individuals must vary in their susceptibility to infection and this variability must be heritable. While it is known that risk of LdNPV infection varies among individual gypsy moths, the biological traits causing this variability are less understood.
My aim is to determine the extent to which larval feeding behavior affects risk of LdNPV infection. In previous work, I created a mathematical model to predict the probability of infection given feeding history, as well as an agent-based simulation to create realistic feeding bouts on digitized leaves. To understand if feeding behavior changes in the presence of LdNPV-infectious cadavers, I conducted a field experiment where larvae were allowed to feed on branches of five leaves, with one leaf contaminated with cadavers. For each of the larvae, I recorded the movement rate, number of feeding locations, and number of leaves eaten. I used this data to simulate larvae feeding on tree branches.
Results/Conclusions
Gypsy moth feeding behavior does not change in the presence of cadavers. Larvae feeding on the cadaver-treated branches move between leaves at the same rate as controls (W(67,67) = 2217.5, p = 0.91). Cadaver presence also has no effect on the number of leaves eaten (poisson GLM: Z= 0.705, p = 0.481). Additionally, we compared the fraction of feeding bouts eaten on the cadaver-contaminated leaves with the fraction eaten on a random control leaf and found no difference between the two treatments (Χ2 (df =1) = 0.5716, p = 0.4496). These results are surprising as it is known that larvae avoid consuming LdNPV-infectious cadavers. We conclude that cadaver avoidance is a behavior that is expressed only in proximity to a cadaver and does not affect larval movement or feeding location.
The agent-based simulation of larval feeding indicates that non-random feeding behavior causes transmission of the LDNPV to increase nonlinearly with increasing larval densities. Feeding behavior may therefore have the potential to play a role in gypsy moth-LdNPV dynamics. The future direction of this project includes creating a larger agent based model to simulate populations of larvae feeding in trees containing LdNPV-infectious cadavers.
