European Corn Borer (Ostrinia nubilalis) in Potatoes (Solanum tuberosum) and the use of Trichogramma Species as an Agent for Biological Control

The European corn borer (Ostrinia nubilalis, ECB) has been observed at pest levels in potato crops on PEI since 1987 and is now considered a primary pest of potatoes in the Maritimes. ECB egg masses are currently used as an indicator of the level of ECB infestation in potatoes, with crop scouts using 2 egg masses per ten plants as an action threshold. Research plots using different artificially created ECB egg mass levels were established at the Harrington Research Farm using two potato varieties, Russet Burbank and Shepody. While the relationship between increasing ECB egg mass levels and larvae numbers is clear and significant (p<0.05), the effect of increasing ECB egg mass levels on tuber yields is less clear. There is evidence that the control threshold can be raised to 4 egg masses per ten plants in both Russet Burbank and Shepody potatoes without affecting tuber yields.;There is a significant linear relationship between ECB larval holes and larval tunnels (R2 = 0.83-0.93, p<0.001), as well as between ECB larval holes and larvae (R2= 0.70-0.74, p<0.001) for both Shepody and Russet Burbank potatoes. Regression equations were calculated for these two relationships which make it possible to estimate ECB damage, in the form of tunnels, and ECB larval levels from the number of ECB larval holes in potato stems.;Trichogramma wasps are internal parasites of primarily lepidopteran insect eggs, which makes them attractive as biological control agents of insect pests such as the European corn borer. Three species of Trichogramma, T. brassicae, T. pretiosum, and T. minutum were tested as biocontrol agents of European corn borer in potatoes both in laboratory choice tests and in small scale trials in potato fields. Mated T. brassicae females showed some interest in parasitizing ECB eggs when given a choice between them and the eggs of the facultative host, Ephestia kuehniella, although they still preferred the eggs of E. kuehniella 2 to 1 over ECB eggs. In an initial trial in organic research plots T. brassicae showed a significant (p<0.05) reduction of ECB larval holes, tunnels, and larvae, but these results were not repeated in field and cage trials in organic and conventionally managed potato fields.