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| Wednesday, January 03, 2007 |
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Frequently
Asked Questions - Cabbage Seedpod Weevil
What does the
Cabbage Seedpod Weevil look like?
The adult Cabbage Seedpod Weevil is a small, ash-grey beetle, three to four mm (1/6 in.) long. Characteristically, it is a hard-bodied insect with mouthparts that include a long snout. The larvae are white, grub-like organisms that feed within the seedpod of the host plants.
What damage does Cabbage Seedpod Weevil cause? Plants commonly attacked by the weevil include members of the Brassicaceae or mustard family, including cultivated crops and weed species. Flower buds and pods are the main parts vulnerable to damage. Because the damage is concentrated on these sections, the damage is substantially higher compared to the damage caused by insects to leaves and other vegetative parts. What is the lifecycle of the Cabbage Seedpod Weevil? There is one generation per year. The adults over-winter in Saskatchewan and emerge in the spring migrating from weeds into host crops. They feed and mate, with the females laying eggs onto developing pods. After hatching, the larvae feed within the developing pod - consuming seeds. When mature, the larvae exit through the pod wall, dropping to the ground to pupate. Later, the emerging adults will feed on the plants causing additional damage. It takes the weevil close to eight weeks to complete development from egg hatch to adult.
Which areas of the province is Cabbage Seedpod Weevil a threat?
An on-going monitoring program has been in effect since 1997. Since then, Cabbage Seedpod Weevil has infested areas extending from the Alberta border to areas as far east as Morse, SK.. A map, produced every year, indicates the areas of infestation along with insect numbers. In 2006 there have been weevil infestations requiring control in the Maple Creek area.
Sweep nets are required to help monitor fields for Cabbage Seedpod Weevil. Monitoring should begin at the early bud stage up through the flowering stage. Sweep perimeter areas, as well as interior sites using 180° sweeping motions. Choose 10 sites within
each field and estimate the average number of weevils. Often, infestations will be more concentrated in field margins early in the season. Control measures may only be needed in the concentrated areas. For information on how to use sweep nets see SAF's Economic Thresholds of Insect Pests at www.agr.gov.sk.ca under Crops | Integrated Pest Management | Insects. How do I control Cabbage Seedpod Weevil? Cultural control methods include interception strategies (using specific crops to trap insects before the protected crop generates buds). Planting non-host crops (e.g. cereals, pulses) or resistant crops such as yellow mustard (Sinapis alba) will help to avoid damage from this insect. There are registered insecticides available to control this insect in crops. See the Saskatchewan Agriculture and Food's 2006 Guide to Crop Protection for more information. The threshold for spraying is when three to four weevils are caught per sweep. The best time to spray is when the crop is in the 10 to 20 per cent flowering stage. Spraying should be done later in the day to minimize impact on beneficial insects (parasites) that help to control Cabbage Seedpod Weevil populations.
Are there any natural biological controls that affect the Cabbage Seedpod Weevil? Two species of wasps have been found on the Prairies: Microctonus melanopus is a wasp that parasitizes adult weevils, and Trichomalis perfectus, is a wasp that attacks weevil larvae within the pods. They are a very important biological control organisms that affect Cabbage Seedpod Weevil populations. Links: Alberta Agriculture, Food and Rural Development
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