Evaluation of foliar and seed treatments for integrated management of root rot and pea leaf weevil in field pea and faba bean
Citation
Willsey, T., Patey, J., Vucurevich, C., Chatterton, S., Carcamo, H. (2021). Evaluation of foliar and seed treatments for integrated management of root rot and pea leaf weevil in field pea and faba bean. Crop Protection, [online] 143 http://dx.doi.org/10.1016/j.cropro.2021.105538
Plain language summary
Field pea and faba bean are important pulse crops grown in Canada. The yield of these crops can be affected by root diseases and pea leaf weevil, an insect that feeds on the nitrogen-fixing nodules of these crops. Root rot and pea leaf weevil often occur together on the roots, and may interact to cause more damage to roots. Field trials were performed at 2 location in southern Alberta in 2016 and 2017 to determine if a combination of fungicide and insecticide treatments would reduce root damage and increase yield. Diseased roots were also tested to determine which pathogens were present. The fungicide seed treatments did not reduce disease levels in any of the years because there were too many different kinds of pathogens. Disease onset also occurred later in the season when seed treatments products would no longer have any activity. The insecticide seed treatment was effective in reducing nodule damage cause by pea leaf weevil larva feeding. Because of the overwhelming effect of root rot on root health, it was not possible to determine if there were any in-field interactions between the disease and the insect pest. An effective method of managing root rot, and potential interaction with pea leaf weevil, is still required.
Abstract
Increased production of field pea (Pisum sativum L.) and faba bean (Vicia faba L.) in Canada has led to a greater incidence of disease and the range expansion of insect pests. Several soil-borne pathogens cause root rot in these crops, while the feeding activity of the pea leaf weevil (Sitona lineatus L.) significantly reduces nitrogen fixation. As pathogens and pea leaf weevil larva are associated with the roots of their mutual host, there is potential for synergistic interactions to occur that may ultimately reduce yield. Field trials at three locations in southern Alberta in 2016 and 2017 evaluated the use of insecticidal and fungicidal seed treatments, a foliar insecticide spray, alone and in combination, and nitrogen amendment as strategies to reduce impacts of both root rots and pea leaf weevil. The fungicides ethaboxam and fludioxonil did not reduce disease severity in pea or faba bean during the two-year field study. Quantitative PCR assays demonstrated that the pathogens Aphanomyces euteiches and Fusarium spp. co-infect pea roots under field conditions, but pathogen levels were not consistently reduced by any of the treatments. The insecticide thiamethoxam reduced nodule and foliar herbivory, whereas the foliar insecticide, lambda-cyhalothrin, and nitrogen fertilization at seeding had no consistent impact. No single or combined treatment protected yield or seed quality, therefore an effective method of managing these constraints to pea and faba bean production is still required.