Parasitism of Beet Armyworm (Spodoptera exigua) Larvae by Cotesia ruficrus (Hymenoptera: Braconidae) in Egyptian Clover Fields

Abstract

Clover, Trifolium alexandrinum L. is the key fodder winter crop, for feeding livestock in Egypt, particularly with a sharp decline in meat and dairy production. One of the important insect pests attacking clover is the beet armyworm, Spodoptera exigua Hübner (Lepidoptera:Noctuidae) which feeds upon clover stems and leaves, and in severe infestation, it can defoliate the plants resulting in considerable foliage reduction. The current investigation was conducted at clover fields in Rasheed district, Beheira Governorate, during the 2020/2021 and 2021/2022 seasons, to monitor the population fluctuations of S. exigua as well as the fluctuations of the larval end parasitoid, Cotesia ruficrus (Haliday) (Hymenoptera: Braconidae) and its efficiency against S. exigua larvae. The first infestation by the beet armyworm was detected on November 1st with 28.00±2.00- 30.00±2.00 larvae, and the highest pest densities were recorded in April and May. The parasitism of S. exigua larvae was recorded started from mid-March up to mid-May. The numbers of the parasitoid،s clusters were low during January, February and March, and were notably high during April and May. This study revealed that C. ruficrus attacked the larvae of S. exigua in clover fields, particularly during April and May, with overall parasitism percentage of 14.41±1.21 - 17.86±1.00%. Thus, the parasitoid, C. ruficrus could be considered as an efficient control element in the integrated pest management (IPM) of the beet armyworm, S. exigua.