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Results of 2016 NW Pea and Lentil Survey for Insect Pests (09/15/16)

A scouting program located in northwest North Dakota was initiated in 2016, and included monitoring for several major insect pests of field peas and lentils from late May to mid-August.

Results of 2016 NW Pea and Lentil Survey for Insect Pests

A scouting program located in northwest North Dakota was initiated in 2016, and included monitoring for several major insect pests of field peas and lentils from late May to mid-August. Support was provided by the Northern Pulse Growers Association for a full time crop scout (Adam Carlson, NDSU) to survey fields in Williams, Divide, Mountrail, McKenzie and Burke Counties.

A total of 164 lentil and 89 pea fields were surveyed in NW North Dakota. Pulse crops were surveyed from the 1-leaf stage (seedling) through R7 mature stages. Maps of the pest data from the 2016 NW Pea and Lentil Survey in North Dakota were uploaded weekly onto the NDSU IPM website.

Cutworms are an early season pest of pulse crops, clipping off young plants and killing them. Pulse crops are more susceptible to cutworm damage than small grains, because cut plants do not grow back (grains compensate by tillering). Cutworms were common and observed damaging plants in 59% of lentil and 42% of pea fields surveyed. The percentage of plants damaged by cutworms ranged from 2% to 18% in lentils and 2% to 17% in peas. Some fields had significant plant stand losses due to cutworm feeding injury and required an insecticide treatment. Maps depict populations of cutworms during the most susceptible crop stages – early vegetative stages.

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Grasshoppers were found in 83% of lentil and 89% of pea fields surveyed from late May through the end of the survey. The range of grasshoppers per 4 sweeps (= 1 yd2) was from 1 to 18 in lentils and 1 to 17 in peas. Most lentil and pea fields were generally below recommended treatment levels for field margins (50-75 per yd2 for nymphs and 21-40 per yd2 for adults).

Pea aphids were found in 52% of lentil and 64% of pea fields surveyed from early June through early August. Pulse crops are most susceptible to pea aphids in the flowering through the early pod stage, which can result in lower yields due to less seed formation and smaller seed size. The economic thresholds using a 15-inch diameter sweep net are an average of 30 to 40 aphids per sweep in lentils and 10 aphids per sweep in pea. In lentils, pea aphid populations ranged from 1-21 aphids per sweep and were sub-economic all season. In peas, pea aphids ranged from 1-12 per sweep with higher economic populations (>10 aphid per sweep) occurring late in crop maturity. As a result, pea aphids did not pose a risk to the NW crop this late in the season. Maps depict populations of pea aphids during the most susceptible crop stages - flowering to early pod.

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For Lygus bugs, an insecticide treatment is recommended when 10 Lygus per 25 sweeps are present during flowering to pod development (until seeds within the pod have become firm) in either lentils or peas. Lygus bugs were found in 46% of lentil and 43% of pea fields surveyed from flowering through maturity. Fortunately, all populations of Lygus bugs observed were not economically in surveyed fields, and ranged from 1-4 per 25 sweeps in lentils and 1-3 per 25 sweeps in peas. Maps depict populations of Lygus bug during the most susceptible crop stages - flowering to early pod.

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Janet J. Knodel                                                                                                                                      Audrey Kalil

Extension Entomologist                                                                                Plant Pathologist, NDSU WREC

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