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Pea Leaf Weevil - Frequently Asked Questions | |
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| | What is Pea Leaf Weevil’s lifecycle and how does it damage my pea crop?
There is one generation of pea leaf weevil per year. The adult pea leaf weevil over-winters in alfalfa or other perennial legumes. When the temperature rises above 17 degrees Celsius in the spring, pea leaf weevil moves into annual legume crops by flying or walking a short distance.
Primarily feeding on field pea, pea leaf weevil may feed on other grain legumes like lentil, but there seems to be something inexplicably unique about field pea vegetation that results in the weevil laying eggs. Therefore the weevil does little damage to crops like lentil. Adults feed on pea leaf margins producing a characteristic scalloped (notched) appearance (figure 1).
| Figure 1. Pea Feeding Damage (photo: L Dosdall) |
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Eggs are laid in the soil near the stem of pea plants. After hatching from the eggs, the larvae proceed downwards to primarily feed on pea nodules resulting in partial or complete inhibition of nitrogen fixation by the pea plant. The main damage to the pea plant is caused more by nodule damage than by foliage damage.
What is the potential range of pea leaf weevil?
Entering into the 2008 crop year, crop insect forecasters are informing us that in 2007 the pea leaf weevil expanded its range and the intensity of damage increased. Please refer to the 2012 Pea Leaf Weevil Forecast map on the provincial Ropin’ the Web web-site.
What type of control measures are available to me at this time and what is the action threshold?
One strategy is to use an insecticide seed treatment. Syngenta’s Cruiser 5FS has received emergency use registration to control pea leaf weevil. Syngenta claims Cruiser 5FS does not antagonize with inoculants.
Pea leaf weevil can also be controlled using a foliar applied insecticide like Matador. The objective is to control the adults before they lay eggs. Therefore, it is important to use insecticide control when the pea plant is very young. The action threshold is to spray at the 2 to 3 node stage when one or more feeding notches appear on 30% (3 out of 10 plants along a seeded row) of the pea seedlings and as long as these 30% have received feeding damage to the plant’s clam leaf (the most recently emerged leaves). If feeding damage occurs only on the lower leaves and not on the clam leaf, the weevil has probably already laid eggs and there is no use in spraying. Therefore, growers should look for damage on the clam leaf and not on the lower leaves. Matador is both a contact and ingestion insecticide, so there is some residual effect.
The pea leaf weevil can fly a long distance (a few km). Since the weevil enters the field from the outside, initial damage will occur along the field borders. Therefore, it may be economically wise for farmers to spray insecticide on the field borders if damage is restricted to this area.
For more information, please see the following links:
Pea Leaf Weevil
2009 Pea Leaf Weevil forecast
Prepared by Neil Whatley, Ag-Info Centre, Alberta Agriculture and Rural Development |
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For more information about the content of this document, contact the Ag-Info Centre.
This information published to the web on April 23, 2008.
Last Reviewed/Revised on January 19, 2012.
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