Crop loss assessment caused by litchi fruit borer, Conopomorpha sinensis (Lepidoptera: Gracillariidae)
1998
Supatra Dolsopon | Nantarat Supakamnerd | Montri Dasananda (Department of Agriculture, Bangkok (Thailand). Horticultural Research Inst. Plant Protection Group. Chiangrai Horticultural Research Center)
Fruit shedding of lychee were usually occurred 40-90 percent after fruit set throughout the season under fruit bagging and no bagging conditions. Fruit bagging had no effect on fruit drop in lychee and decreased in longan, and also provided protection from the infestation of C. sinensis. Fruit drop of lychee was increased with no bagging due to litchi fruit borer, fruit crack and fruit browning disease which are the main effects of yield reduction. Harvested fruit of longan were 61.82 percent in 1995 and 56.28 percent in 1996 under bagging conditions. But there were only 22.55 and 23.06 percent of lychee fruit that had been harvested. It was found that under no bagging conditions, 8.86 percent of lychee and 1.03 percent of longan were infested by C. sinensis in 1995. Similarly, in 1996 there were 8.52 and 1.58 percent in lychee and longan respectively. It is clear that bagging can be used to protect fruit damaged by C. sinensis. However, 6.25 percent of fruit browning disease were obviously seen in lychee under bagging conditions. This never happens in longan. Mature fruit of longan and lychee were randomly harvested. Apparently 19.34 percent of lychee were not infested by fruit borer whereas 65.41 percent were destroyed. 8.4 percent of fruit had brownskin. Moreover 6.74 percent of lychee were simultaneously damaged by fruit browning disease and fruit borer. 89.89 percent of harvested fruit of longan were not attacked but 9.93 percent were contaminated by fruit borer. Insect parasitoids of C. sinensis were observed. Five species of larval parasitoids have been found, all of them are solitary ectoparasitoids. Three species of braconid were Phanerotoma sp., Colastes sp. and Pholestesor sp. Another two ichneumonids were identified as Goryphus sp. and Paraphylax sp. Infested fruit fall by C. sinensis were parasitised 49.07 percent. There were only 4.18 percent of parasitism on lychee and 7.28 percent on longan leaves.
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