Ecological and biological studies on aphids and their associated predatory spiders on two field crops at Qalubyia governorate, Egypt.

Abstract

In Egypt, as in other countries, plant production for human and livestock consumption is threatened by a wide range of insects and arthropod species. Among the serious pests that cause big loss of field crops as broad bean and maize are the cowpea aphid, Aphis craccivora and the corn leaf aphid, Rhopalosiphum maidis. Biological control involves the use of natural enemies to control pests. Generally, spiders are considered to be one of the most important predators which can be used as biological control agents of several important agricultural insect pests. This study included the following points: 1. Seasonal dynamics of Aphis craccivora and Rhopalosiphum maidis: The cowpea aphid, Aphis craccivora and the corn leaf aphid, Rhopalosiphum maidis are common pests of broad bean and maize crop which are considered as economically important crops, mainly for their use as a food for human in Egypt.

a. This study was conducted at Qaha research station, Qalubyia governorate during two successive years, 2017and 2018 on broad bean and maize crops. Infestation on broad bean and maize started with low incidence in winter (January) and early summer (May& June), respectively. The monthly levels of A. craccivora infestation was gradually increased to reach two peaks in February and in March and represented 33.6 & 37.2% of the total collected life stages in the broad bean season 2017 and one peak 38.5% in March 2018. Also, the monthly level of R. maidis infestation was gradually increased to reach maximum in August and represented 42.7% & 41.8% of the total collected life stages in the maize season 2017 and 2018, respectively. b. In both infested crops, the immature life stages were the most abundant life stage of the total stages collected in each month and the unwinged (apterous) adult females predominated winged (alate) females monthly collected.

c. The obtained results revealed that infestation with winged females started relatively late on each crop sometimes reaching February and July on broad bean and maize, respectively. Also, winged females started disappearing during the last month (April & September, respectively) of the season of each crop.

d. Generally, the total number collected of each of A. craccivora and R. maidis life stages was higher in 2018 season than 2017 season on each of broad bean and maize crop while the infestation with total life stages of A. craccivora and R. maidis was higher on broad bean crop (419&548 aphid stages) than on maize crop (234&385 aphid stages) during the two successive years.