Chikara Ishijima

Field Efficacy and Transmission of Fast- and Slow-Killing Nucleopolyhedroviruses that Are Infectious to Adoxophyes honmai (Lepidoptera: Tortricidae)

The smaller tea tortrix, Adoxophyes honmai (Lepidoptera: Tortricidae), is an economically important pest of tea in Japan. Previous work showed that a fast-killing nucleopolyhedrovirus (NPV) isolated from A. orana (AdorNPV) and a slow-killing NPV isolated from A. honmai (AdhoNPV) are both infectious to A. honmai larvae. Field application of these different NPVs was conducted against an A. honmai larval population in tea plants, and the control efficacy and transmission rate of the two NPVs were compared. The slow-killing AdhoNPV showed lower field efficacy, in terms of preventing damage caused by A. honmai larvae against the tea plants, than the fast-killing AdorNPV. However, AdhoNPV had a significantly higher horizontal transmission rate than AdorNPV. These results show that AdorNPV is suitable as an inundative agent, while AdhoNPV is an appropriate inoculative agent.

Occurrence of the Tea Tortrix Complex and their Parasitoids in Pesticide-Free Tea Fields in Shizuoka Prefecture, Japan

The occurrence of the tea tortrix complex and its parasitoids in pesticide-free tea fields from 2006 to 2008 was investigated by using light traps and sticky suction traps, respectively, in order to examine the interaction between them. The numbers of both Adoxophyes honmai Yasuda and Homona magnanima Diakonoff trapped by light traps were observed to decrease from 2006 to 2008, and the rate of decrease in the case of the former was higher than that in the case of the latter. The most numerous parasitoids trapped by suction sticky trap were Trichogramma spp., followed by Apanteles adoxophyesi Minamikawa. Ascogaster reticulata Watanabe and Bracon adoxophyesi Minamikawa were found to be trapped rarely. Although the numbers of both Trichogramma spp. and A. adoxophyesi trapped by sticky suction traps between 2006 and 2007 were observed not to be different, the numbers of them drastically decreased in 2008. The numbers of A. reticulata and B. adoxophyesi were observed to decrease from 2006 to 2008. Particularly in 2008, they were found to be trapped rarely. We also compared seasonal changes in the numbers of tea tor trix complex with Trichogramma spp. and A. adoxophyesi. As a result, the number of trapped Trichogramma spp. adults reached a peak 10 to 28 days (average : 19.9 days) and 2 to 25 days (average : 15.7 days) after the peak in the number of A. honmai and H. magnanima adult females, respectively. The number of trapped A. adoxophyesi adults reached a peak 2 to 48 days (average : 26.1 days) and 1 to 39 days (average : 21.8 days) after the peak in the number of A. honmai and H. magnanima adult females, respectively. In addition, a comparison of the seasonal changes in the number of