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Manitoba Agriculture, Food and Rural Initiatives

Manitoba Insect Update

June 8, 2009                   

Compiled by: John Gavloski, Entomologist, Manitoba Agriculture, Food and Rural Initiatives, Crops Knowledge Centre,
Phone: 204-745-5668; Fax: 204-745-5690

To report observations of insect activity or control that may be of interest or importance to others in Manitoba, please send messages to the above contact addresses.

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Summary

Cutworm numbers are high in some sunflower and canola fields in central Manitoba. Flea beetle feeding in canola is a concern in many areas of Manitoba.

Recent Insect Concerns and Observations

Cutworms in sunflowers and canola: Cutworms are at levels of concern in many fields in the central region of the province. Sunflowers are the crop that seems to be the most affected so far, although there have been some canola fields sprayed for cutworms as well. Of several samples I have looked at from sunflower fields, all have been dingy cutworms. Most are in their middle instars (stages of growth). Most of our problem species of cutworms grow through 6 instars before becoming pupae, at which time their damage for the season is done.

MAFRI has a factsheet on cutworms, which was revised in the spring of 2009, on its website. It can be viewed at: https://www.gov.mb.ca/agriculture/crops/insects/fad06s00.html

Note the “V” shaped markings on the back of the dingy cutworm. I’ve also heard them referred to as “tire tracks”. These are quite different than the distinct reddish lines on the redbacked cutworm. The red lines on the redbacked cutworm are broken by a white line surrounded by black (refer to the picture in the factsheet).

These are just a couple of the more common species of cutworms in Manitoba, but there are many others. So if you find some and are not sure of the species, feel free to send in a sample. Not all cutworms develop at the same rate, and some feed only belowground and rarely come above ground as larvae. This makes these species harder to control then species that spend more time above ground. These are a couple of reasons why it is good to know what species of cutworms are most common in a field. It is quite possible that may fields will have more than one or several species of cutworms; what is important is knowing the dominant species.

Flea beetles on Canola: There is still concern over flea beetle feeding on canola, on some applications of foliar insecticides. Due to the abnormally slow growth of canola this year, the effectiveness of insecticides in the seed treatments are wearing off before canola can grow to the more resistant 3 to 4 leaf stages. Because of this, and other potential problems such as cutworms, farmers and agronomists are encouraged to scout canola fields for potential problems, regardless of the seed treatments that may have been used. Flea beetles will feed more on warm, calm days than on cooler days.

 

Surveys and Forecasts

Bertha armyworm:
Although the traps for adult moths of bertha armyworm are usually set up in early June, the cool conditions this year will have slowed development of the adult moths within the pupae. It is anticipated that there will not be many moths emerging before the third week in June. So if traps have not been set up yet, we should aim to have all the bertha armyworm traps set up by the end of the week of June 15-19th.

Diamondback Moth :
Data and interpretation of data from traps for diamondback moth adults can be found at: https://www.gov.mb.ca/agriculture/crops/insects/db/index.html
Very few diamondback moth have been recorded so far.

Grasshoppers: The species of grasshoppers that have potential to get to pest status should be starting to hatch. Models have been developed to predict the hatch of these species of grasshoppers. Maps estimating hatching dates can be found at: http://research.uleth.ca/spg/.
Models predicted that hatch is just starting in most of Manitoba and should peak in mid to late June. Grasshopper egg development is one to two weeks later than normal this year.