Management of Delia (Diptera: Anthomyiidae) through selectively timed planting of Phaseolus vulgaris (Fabaceae) in Atlantic Canada
Citation
Silver, N., Hillier, K., Blatt, S. (2018). Management of Delia (Diptera: Anthomyiidae) through selectively timed planting of Phaseolus vulgaris (Fabaceae) in Atlantic Canada. The Canadian Entomologist, [online] 150(5), 663-674. http://dx.doi.org/10.4039/tce.2018.36
Plain language summary
Root maggots (Delia species) are known pests of vegetable crops. In Nova Scotia and Prince Edward Island, there are two species of root maggot found in field-grown bean: the seedcorn maggot (D. platura) and bean seed maggot (D. florilega). We used field studies to document the relationship between planting date and occurrence of Delia damage on bean roots. Bean seed sowed in mid-June had higher crop yield (more beans/plant) and lower root damage rating compared with earlier plantings. In 2016 and 2017, plantings sown in late May and early June showed high damage ratings and low plant survival. Plantings sown during late June and early July had low damage ratings but also low yields. Laboratory experiments studied which plant growth stage (of 8 stages examined) and which variety (2 varieties tested) was most preferred by the seedcorn maggot for feeding or egg-laying. Greater numbers of eggs were laid on plants at early growth stages, with no difference observed between the varieties. Root damage was greatest on early growth stages. Our findings provide an opportunity for growers to time their sowing to avoid the egg laying phase of the seedcorn maggot.
Abstract
Delia Robineau-Desvoidy (Diptera: Anthomyiidae), including Delia platura (Meigen), are known pests of vegetable crops. Here, three studies were conducted to examine the relationship between Delia species and Phaseolus vulgaris Linnaeus (Fabaceae). Field studies documented a relationship between planting date and occurrence of Delia damage on P. vulgaris. Plantings in mid-June resulted in higher crop yields (mean bean pods per plant) and reduced damage ratings compared with earlier plantings. Late-May and early-June planting dates were not favourable, as they resulted in high damage ratings and low plant survival. Late-June and July plantings resulted in low damage ratings but low crops yields. Growth chamber experiments examined oviposition preference of D. platura females at eight phenological stages for two varieties of P. vulgaris. Results indicated significantly higher oviposition rates on bean plants at early phenological growth stages, with no significant varietal preference shown by maggots. Laboratory experiments quantified the impact of D. platura larval infestation on two P. vulgaris varieties at two growth stages. Results indicated no significant difference in variety choice. Recommendation for planting P. vulgaris to coincide with Delia phenology using a degree-day model is discussed.