Comparison of Efficacy of Entomopathogenic Nematodes Combined with Antidesiccants Applied by Canopy Sprays Against Three Cotton Pests (Lepidoptera: Noctuidae)

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Abstract
Ways to reduce larval populations of the cotton pests Earias insulana (Boisduval), Heliothis armigera Hübner, and Spodoptera littoralis (Boisduval) by using the entomopathogenic nematode Steinernema carpocapsae (strain Mexican) were defined. In a screening assay, the survival at low relative humidities of nematode infective juveniles (IJs) treated with the antidesiccants Biosys 627 (15 and 20% wt/wt), Folicote (6% wt/wt), and natural wax (18% wt/wt) were three times higher than the control (25%). None of the antidesiccants tested, with the exception of New Film, had any adverse effect on nematode viability in aqueous solutions. Application to the foliage of 500 and 1,000 IIs/ml in water was required to attain > 85% control of E. insulana and S. littoralis, respectively, on bean plants. Addition of the antidesiccants Biosys 627 (20% wt/wt), natural wax (18% wt/wt), or Folicote (6% wt/wt) to the nematode suspension had a similar effect on insect mortality, with lower nematode concentrations (125 and 250 Us/ml for E. insulana and S. littoralis, respectively). In the case of H. armigera, nematode suspension at a concentration as high as 5,000/ml water resulted in only 22% control. Addition of the antidesiccants resulted in a 4-fold increase (to 85-95%) of insect mortality. In microplot experiments, foliage application of S. carpocapsae ‘Mexican’ (250 Us/ml) mixed with Folicote (6% wt/wt) resulted in a 61% reduction in the persistence of S. littoralis larvae on cotton plants. Damage to the foliage was reduced by 46% compared with the control. Substantial reduction (76%) of E. insulana larvae was achieved by application of 125 Ils/mi mixed with Folicote (6% wt/wt).

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