Evaluation of Helicoverpa armigera Nucleopolyhedrovirus (HearNPV) for Control of Helicoverpa armigera (Lepidoptera: Noctuidae) on Citrus in South Africa

Abstract

A concentration of 1.15×10⁷ OBs/mL of HearNPV, sprayed using a knapsack, resulted in a 100% reduction in Helicoverpa armigera larval infestation within 7 days on tomato plants in a hot house environment. A 10-fold lower concentration, 1.15×10⁶ OBs/mL, resulted in a 100% reduction within 16 days. These two concentrations reduced damage to tomatoes by 81 and 69%, respectively. In two field trials on navel oranges, the lower concentration and an additional even lower concentration of 7.26×10⁵ OBs/mL, both resulted in a 100% reduction in H. armigera infestation within 14 days or longer. H. armigera damage to fruit was reduced by up to 84 and 75%, respectively, in the two trials. Rejection for export was reduced by 96 and 62%. This could imply a saving of US$339 per hectare compared to the untreated control. These results were better than those achieved with Bacillus thuringiensis and various standard chemical insecticides used in the same trials. Reasons for these results are discussed.

Keywords:

• Helicoverpa armigera
• nucleopolyhedrovirus
• HearNPV
• citrus
• navel oranges
• tomatoes
• azadirachtin
• Bacillus thuringiensis
• chlorpyrifos
• parathion
• mevinphos

Acknowledgments

We thank the Parks Department of the Nelson Mandela Metropole Municipality for the use of their hot-house, Patensie Sitrus Beperk for the use of Paksaam Farm and Michael Price for the use of Daisydelle Farm. We thank Outspan International for funding this work and Tim Grout for reviewing the manuscript.