Population dynamics of pests and some of their predators in soybean field under influence of herbicidal applications of Toxaphene.

Abstract

Population response of phytophagous arthropods and natural enemies to toxaphene, based on its use as a herbicide (two applications at the dose of 3.36 kg of a.i./ha) to control sicklepod, Cassia obtusifolia, was studied on soybean Glycine max (L.) Merrill, in a large field experiment of 0.04 ha parcels in a diversified agroecosystem at Madison Co., in North Florida, USA, during the 1980 crop reason. Only intensive toxaphene treatment appears to have affected population of Spissistilus festinus (Membracidae). Timing and intensity of sprays signiftcantly decreased and increased the levels of the noctuid pests,  Anticarsia gemmatalis and Heliothis zea, respectively. Populations of the predators Nabis roseipennis (Nabidae), and Solenopsis invicta (Formicidae) decreased while larvae of Chrysopa rufilabris (Chrysopidae) and Labidura riparia (Labiduridae) increased significantly following toxaphene applications. Populations of L. riparia augmented independently of the prey density of A. gemmatalis; however, nabids and geocorids showed a progressive and weak density dependent response to A. gemmatalis. Migratory activity of the predator Calosoma alternans was strongly associated with the presence of high levels of A. gemmatalis caterpillar populations.