Preferred direction site of the sugar-cane field to infestation by Pulvinaria tenuivalvata (Newstead) and its relation with parasitized Coccophagus scutellaris Hymenoptera Aphelinidae

Abstract

This research aims to evaluate the effects of biotic factors on the population density of the sugar cane soft scale P. tenuivalvata. Population estimation was performed in different sites of the sugar cane field, i.e, east, north, south, west and field center. Results show that, scales proportionally increased from May to December in all field sites and the scales wereintensively through September, October and November. Plants located in the west site intensively harbored the highest population of scales, followed by north site. The number of scales on plant in west and south sites was approximately similar. The field center harbored the lowest scale population. These results reveal that the west direction followed by north are preferred by this insect in its various stages . This could be attributed to the direction of the wind which always blows from north to west carrying crawlers to these directions where it may aggregate for feeding and growth. During the two successive seasons of the study, data also revealed the incidence of the Aphelinidae parasite Coccophagus scutellaris (Aphelinidae: Hymenoptera) parasitizing the different immature stages (except 1 st instar) and mature stage (adult females). The influence of such parasite on the insect was significant in both seasons. In conclusion, there are many biotic factors that can affect the population density of the sugar cane soft scale P. tenuivalvata. This can assist to avoid the difficult application of the insecticide and minimize the population of the environment. natural enemies (parasites).