Abundance versus precision: an ovipositional analysis of Delia radicum and Delia platura on crucifer crops in Nova Scotia.
Citation
Harris, E, Hillier, NK, and Blatt, S. 2019. Abundance versus precision: an oviposition analysis of Delia radicum and Delia platura on crucifer crops in Nova Scotia. Joint Annual Meeting of the ESC/CSEE and AES, Fredericton, August.
Plain language summary
Root maggots are a serious agricultural pest across the globe. Some species are specialists on certain families of plants while others are generalists feeding on a wide range of plant families. In crucifer crops, Delia radicum is a specialist species, feeding on multiple members of the family Brassicaceae. Also found in these fields are the generalist species, Delia platura (seedcorn maggot) and Delia florilega (bean seed maggot). Field surveys in Nova Scotia crucifer crops (radish, rutabage, broccoli, cauliflower and cabbage) found all three species to be present as adults, but only D. radicum was found damaging the crop. In the laboratory, D. radicum was observed to select older plant stages for oviposition while D. platura would oviposit (lay eggs) on younger plant stages. When D. platura eggs were placed on plants, D. radicum would alter their oviposition pattern. The interaction between these two species suggests potential new avenues for a more specific trapping method.
Abstract
Delia radicum (Diptera: Anthomyiidae), cabbage maggot, is a specialist on crucifers such as cabbage and broccoli. A generalist species, Delia platura (seedcorn maggot) is reported to feed on crops such as bean, rutabaga and cabbage. Competition between these species has not been studied. Laboratory studies evaluated D. platura and D. radicum for oviposition on cabbage, broccoli and radish. Experiments were done at four plant stages (germination, cotyledon, first true leaf, second true leaf), with two mating pairs of a species placed on a single plant, covered with a 2 L plastic bottle dome and placed , in a growth chamber for 48 hours. Each trial had 6 plants with D. platura, 6 with D. radicum, and 4 controls (no plant). Each trial was repeated 5 times for each plant stage. Eggs were counted and recorded. Preliminary laboratory results show D. platura to be attracted to soil, and will oviposit on controls, while having only slight preference to the germination and cotyledon stages. D. radicum will only oviposit on plants, preferring the later stages.