Spatial patterns of Tuta absoluta and heterorhabditid nematodes

摘要

The tomato lea miner, Tuta absoluta, is a serious pest that can spread rapidly and damage tomato production substantially. Understanding the spatial distribution of the pest population and its natural enemies under specific conditions will aid in the formation and application of integrated control strategies against the pest. The dispersion parameter of T. absoluta larval population derived from Taylor's Power Law was studied at plant, leaf and leaflet scales in three tomato fields in Egypt. Values of b, the distribution parameter of the Power Law, increased from plant to leaflet, indicating a more aggregated distribution as the size scale diminished. Data transformations were calculated from parameters of the Power Law fitted to the data obtained across the three fields and compared with log and square root transformations. Using baiting technique with Galleria mellonella, entomopathogenic nematodes (EPN) were not detected from the three fields but were found in 29 out of 30 soil samples obtained from a nearby mango orchard. Mortality of T. absoluta larvae caused by Heterorhabditis species isolated from the orchard ranged from 90.0 to 96.7% suggesting that its inundative release for pest control may be feasible. Horizonta1. spatial patterns of the nematodes were aggregated within the orchard, with individual soil samples being imich more likely to contain sufficient nematodes to infect multiple G. mellonella larvae than was predicted based on the total number of positive soil samples. The distribution of EPN-infected G. mellonella larvae within a series of extractions was random in 27 out of the 29 samples; the larvae were aggregated in the two remaining positive samples. The possibility of finding infected G. mellonella larvae in the positive samples was not more than that expected by chance.