Novel application of gels as potential carriers for beneficial insects

Seven agricultural gels were tested as potential carriers for the eggs of 2 predators, Perillus bioculatus (F.) and Podisus maculiventris (Say) (Heteroptera: Pentatomidae). Gels were tested for their effects on egg hatch in petri dishes, covered and uncovered, using 3 viscosities. Egg hatch in petri dishes was generally higher in polyacrylamide gels (Aquastore F and Terra-sort GB) and starch-based gels (SGP 104K and Waterlock B-100) than in hydroxycellulose-based N-Gel or alginate-based Keltose. Egg hatch was lower in covered versus uncovered dishes, and also lower in high viscosity versus low or medium viscosity gels; however, high viscosities were necessary to stick eggs to plant leaves. Four gels from the petri dish trials were tested on eggplant (Solanum melongena L.) and potato plants (Solanum tuberosum L.) in the greenhouse using both predators. The polyacrylamide gels (Aquastore F and Terra-sorb GB) consistently resulted in the highest percentage hatch: hatch rates using these gels were equivalent to the control for P. maculiventris on eggplant, and 19 -46% lower than controls on other predator-plant combinations. Hatch data from eggs stored with and without Aquastore F or Terra-sorb GB at 5, 10, or 15 degrees C for 5, 10, or 15 d were compared with those stored at 25 degrees C, with and without gel. Eggs stored in gel did not hatch. Percentage hatch of eggs of both predators stored without gel was lowered by increased storage duration, but was less affected by temperature. Gel amendments (H2O2 and spreader/stickers) decreased hatch rates in gels. Possible explanations for the varying effects of the gels on egg hatch are discussed. Delivery of predator eggs in gels in the future may have practical use in augmentative biological control programs.