A simulation model of the population dynamics of Helicoverpa armigera (Hübner) on pigeonpea Cajanus cajan (L.) Millsp., in southern India is described. Differences in the magnitude and timing of H. armigera populations between 1986 and 1987 can be accounted for by two factos: the time of first flowering of the crop and the numbers of immigrant moths. Simulated populations of early-instar larvae, the target life stage for insecticides, are particularly sensitive to the onset and duration of moth immigration, the time of flowering, moth age at immigration, and the development time of young larvae. The most effective application times for one, two and three simulated sprays are 10 days after flowering (d.a.f.), 10 and 14 d.a.f. and 6, 10 and 14 d.a.f., respectively. These timings are effective for a feasible range of variation in the key components of the model. With larvae that are resistant to the insecticide and the insecticides of short residual action, the timing of applications is most critical. Even three well-timed sprays are unlikely to maintain densities of resistant larvae within acceptable limits unless immigration is very low or conservative damage assumptions are made. One or two insecticide applications should provide adequate control of susceptable larvae in most circumtances.
Holt, J.; King, A.B.S.; Armes, N.J. Use of simulation analysis to assess Helicoverpa armigera control on pigeonpea in southern India. Crop Protection (1990) 9 (3) 197-206. [DOI: 10.1016/0261-2194(90)90164-3]