Manipulation of environment to facilitate use of nematodes in biocontrol of insects

Abstract

The pre- and postparasitic phases of entomophilic nematodes are exposed to different microenvironments which should be changed in order to facilitate the use of nematodes as biological control agents of insects. The mixing of “thick water” with nematodes prior to spraying on exposed surfaces retards nematode desiccation and so increases the mortality of forest and agricultural insect pests. Aquatic larvae of Simulium vittatum and of Culiseta inornata feed fastest at 20 and 25 C, respectively, and so engulf more infective larvae of Neoaplectana carpocapsae (DD-136). When exposed to N. carpocapsae (DD-136) on potato foliage, the percentage of encapsulated nematodes in the haemocoel of adult Leptinotarsa decemlineata was less than in the third stage nymphs. The percentage of unencapsulated, dead nematodes was greatest in the nymphal stages. The value of baits and phagostimulants to increase the insects' oral uptake of infective nematodes and of the manipulation of the insect's physiological processes so as to modify its susceptibility to nematodes is discussed.