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Pea Leaf Weevil – New Pest of Field Pea and Faba Bean in Western ND (05/03/18)

A new NDSU Extension publication E1879 Integrated Pest Management of Pea Leaf Weevil in North Dakota was printed this April.

Pea Leaf Weevil – New Pest of Field Pea and Faba Bean in Western NDe1879 Part1.thumb.

A new NDSU Extension publication E1879 Integrated Pest Management of Pea Leaf Weevil in North Dakota was printed this April. It summarizes the distribution, biology, scouting & E.T., and pest management strategies for pea leaf weevil for pulse crop growers. Since the adult is difficult to scout for and foliar applied insecticides have limited control of pea leaf weevil, systemic insecticide seed treatments are currently one of the better strategies to reduce adult defoliation, egg laying and larval feeding on the root nodules. There are two active ingredients registered in field peas: thiamethoxam (Cruiser 5F, Cruiser Maxx) and imidacloprid (Attendant 600, Dyna-Shield imidacloprid 5, Gaucho 600, Senator 600FS, other generics). Some producers / crop consultants have called wondering what the best rate of insecticide seed treatment is for control of pea leaf weevil in field peas.

Canadian researcher, Dr. Hector Cárcamo, has studied different rates of thiamethoxam for control of pea leaf weevil in greenhouses grown field peas [Cárcamo et al. 2012. J. Insect Science 12: 151. 12pp. (http://www.insectscience.org/12.151)].

During seedling stages (2nd-5th nodes), they found that2018 05 02 1705.knodel adult foliage damage was reduced in the plants with a 30 and 50 g a.i. per 100 kg seed dose compared to the untreated check (see graph). The 50 g a.i. per 100 kg seed dose is equivalent to the labeled rate of Cruiser 5F (1.28 fl. oz. per cwt). However, adult mortality was only 15-30%. Egg laying and egg viability were also lower in females that feed on pea foliage treated with thiamethoxam. Larval survival and larval feeding on root nodules were lower only at the 2nd node stage and no effect was observed at the 5th node stage suggesting that the toxic residual declined at later crop stages. The bottom line is to use the highest labeled rate of the insecticide seed treatment to provide the most efficacious treatment for management of pea leaf weevil. Even with a high rate of insecticide seed treatments, it is important to know that there could be some damage to the nodules and yield loss, especially with high weevil populations.

(Note: Mention of any products are giving as examples only and do not imply an endorsement nor discrimination against any products not mentioned by the author or university.)

 

Janet J. Knodel

Extension Entomologist

 

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