Targeting diamondback moths in greenhouses by attracting specific native parasitoids with herbivory-induced plant volatiles.

We investigated the recruitment of specific parasitoids using a specific blend of synthetic herbivory-induced plant volatiles (HIPVs) as a novel method of pest control in greenhouses. In the Miyama rural area in Kyoto, Japan, diamondback moth (DBM) (Plutella xylostella, Lepidoptera: Plutellidae) larvae are an important pest of cruciferous crops in greenhouses, and Cotesia vestalis (Hymenoptera: Braconidae), a larval parasitoid of DBM, is found in the surrounding areas. Dispensers of HIPVs that attracted C. vestalis and honey feeders were set inside greenhouses (treated greenhouses). The monthly incidence of DBMs in the treated greenhouses was significantly lower than that in the untreated greenhouses over a 2-year period. The monthly incidences of C. vestalis and DBMs were not significantly different in the untreated greenhouses, whereas monthly C. vestalis incidence was significantly higher than monthly DBM incidence in the treated greenhouses. Poisson regression analyses showed that, in both years, a significantly higher number of C. vestalis was recorded in the treated greenhouses than in the untreated greenhouses when the number of DBM adults increased. We concluded that DBMs were suppressed more effectively by C. vestalis in the treated greenhouses than in the untreated greenhouses.

Abundances of a bean bug and its natural enemy in seminatural and cultivated habitats in agricultural landscapes.

To determine differences in distribution patterns between the soybean pest Riptortus pedestris F. (Hemiptera: Alydidae) and its egg parasitoid Ooencyrtus nezarae Ishii (Hymenoptera: Encyrtidae) in source and cultivated habitats, we compared their abundances in soybean fields and forest edges, which were assumed to be the overwintering sites of R. pedestris. We set synthetic attractant-baited traps for both species over 2 yr in mid-August, just before R. pedestris normally colonizes soybeans. During one of the 2 yr, we also examined the rate of parasitism using an egg trap. The numbers of both R. pedestris and O. nezarae trapped at forest edges were higher than the numbers caught in soybean fields, suggesting that forest edges are important source habitats. Compared with R. pedestris, the abundance of O. nezarae in soybean fields was considerably lower than in forest edges, presumably because of differences in their dispersal abilities and their responses to landscape structure and resource distribution. Better pest control service by O. nezarae was provided at forest edges than in soybean fields. Therefore, when using pest control by O. nezarae in soybean fields, spatial arrangement and distance from the forest edge should be considered.

A baculovirus-encoded protein tyrosine phosphatase gene induces enhanced locomotory activity in a lepidopteran host.

Enhanced locomotory activity (ELA), such as wandering, is a normal behavior that occurs at the end of the larval stage in lepidopteran (butterflies and moths) insects. Baculovirus infection can also induce ELA in lepidopteran larvae. The belief is that the virus induces this behavior to increase its transmission [Goulson, D. (1997) Oecologia 109, 219-228]. Here we show that a baculovirus-encoded protein tyrosine phosphatase (PTP) gene (ptp) induces ELA that is activated by light. ELA was induced in silkworm Bombyx mori infected with the baculovirus B. mori nucleopolyhedrovirus (BmNPV) beginning at approximately 3.75 days postinfection (p.i.) and continued until 4.75 days p.i. The intensity of the ELA was dramatically reduced immediately before death at 5.25 days p.i. Light activated the intensity of the ELA by approximately 3-fold, and larvae with ELA showed positive phototropism. ELA was not induced in larvae of B. mori infected with a BmNPV ptp knockout mutant (BmPTPD). However, when a silkworm-derived ptp gene (Bmptp-h) was inserted into BmPTPD, ELA was partially recovered. Bmptp-h was identified from silkworms at 2 days after the start of the natural wandering stage. The deduced amino acid sequence of Bmptp-h showed 48.2% identify (80.7% similarity) to the deduced amino acid sequence of BmNPV ptp. On the basis of the high homology and larval stage at which Bmptp-h was isolated, we postulate that the modern baculovirus may have acquired its ptp gene from an ancestral host and that this gene was selectively maintained because it increases virus transmission.