Oviposition preferences of Pickleworm (Diaphania nitidalis) with implications for management through trap crops and companion planting

Pickleworm (Diaphania nitidalis Lepidoptera: Crambidae) is currently found on four of the major Hawaiian Islands attacking cucurbits. The current management approach for this pest is the use of weekly insecticide applications typically with broad-spectrum insecticides. This approach is unsustainable due to increased risk of pesticide resistance and because it diminishes natural enemy and pollinator populations in the crop. This study investigated the potential of using Cocozelle squash as a trap crop and watermelon as a companion plant to manage pickleworm on cantaloupe through a series of female oviposition preference experiments. Gravid female pickleworm moths were given a choice between a leaf of Cocozelle squash, cantaloupe, and watermelon to lay their eggs on. This was compared to the female response when presented with only cantaloupe leaves and when presented with only bean leaves (non-host). When females had the choice of leaves from the three plant species they laid a significantly higher proportion of their eggs on the cantaloupe leaf. When presented with only bean leaves the females laid fewer eggs in comparison to the egg amounts laid in other trials, indicating that the females did not prefer to lay their eggs on this plant even in a no-choice situation. Based on this leaf preference experiment, it would appear that this management strategy might not be appropriate for this pest. However further whole plant preference experiments may shed more light on the female preference when she is given a higher amount and diversity of plant surface area to lay her eggs on.