The Management of Helicoverpa Species by Entomopathogenic Nematodes

Abstract

Helicoverpa spp. are major polyphagous insect pests of agricultural, horticultural and ornamental crops and are widely distributed in tropical and subtropical regions of the world. The crop production has been severely threatened by increasing difficulties in controlling these pests as they have developed high levels of resistance to commonly used insecticides. The integrated pest management programmes are used to suppress pest numbers below threshold level by combining different control tactics such as monitoring of pest populations, manipulation of cultural practices, host–plant resistance including deployment of transgenic crops, biological control and judicious use of insecticides, etc. Nevertheless, this pest is not brought under control. Among microbial control agents, entomopathogenic nematodes have shown potential in controlling insect pests in cryptic and epigeal (soil surface) habitats compared with exposed foliage. The outcome of foliar applications indicates that nematode alone is not effective on foliage; as a consequence, Helicoverpa larvae escape nematode’s pathogenic attack and continue damaging fruiting bodies. The control option at soil-dwelling stages could play a crucial role in the management of this pest at the time when larva is finding a hiding place in crack, crevices or loose soil in the field to undergo pupation. Therefore, charging nematode in irrigation water could substantiate an approach to suppress the forthcoming generations of Helicoverpa species, thus preventing adult emergence, subsequent migration and damage to succeeding host crops.