Insects Found but Not Needing to be Controlled Yet

2009 – Issue 11

There were still a couple of reports of cutworms in Saskatchewan this past week but it appears as if larval feeding is winding down as they are beginning to pupate. More information on cutworms is available at: https://canola-council.merchantsecure.com/canola_resources/product22.aspx

The cabbage seedpod weevil threat is also winding down in southern Alberta and southwestern Saskatchewan as many crops are well into or have finished flowering. Only fields that are just coming into flower are still at risk. Reports are that populations were lower than last year and in many fields were below threshold. The economic threshold for the weevil is 20 to 30 weevils in 10 sweeps, depending on crop price. More information is available in the cabbage seedpod weevil section at the following link: http://www.canola-council.org/contents10b.aspx

All across western Canada there were reports of increasing grasshopper populations, but the recent wet conditions seemed to have slowed their attack for the time being. Grasshoppers may become a concern in canola adjacent to fields cut for hay as the insects migrate to continue feeding. Continue scouting for grasshoppers because if caught early perimeter spraying may be all that is needed.  A specific economic threshold for grasshoppers in canola has not been established as it is not a preferred host crop, but it is currently considered to be in the range of 7 to 14 per m2, depending on the crop value and cost for control. More information on grasshoppers is available at the following link: http://www1.agric.gov.ab.ca/$department/deptdocs.nsf/all/agdex6463

Insect monitoring traps collected 26 adult diamondback moths near Indian Head, SK recently. However, populations of larvae observed in parts of Saskatchewan are below the economic threshold of 100 to 150 larvae per m2 in immature and flowering fields or 200 to 300 larvae per m2 in flowering and podded fields. Scott Hartley, Saskatchewan Ministry of Agriculture, indicates it is getting too late in the season for multiple generations of this insect to become a threat. More information on diamondback moth is available at the following link:http://www.agriculture.gov.sk.ca/Default.aspx?DN=688b2f99-ad99-423d-900c-c01a1c45d8a1

Cabbage root maggots were reported in Saskatchewan and Alberta.  A number of fields in central Alberta had considerable damage. Drier conditions earlier this spring are generally not favorable for root maggots so it is a bit surprising to see significant damage (as many as 3 maggots per plant root). Unfortunately there are only cultural management tools for this insect pest. More information on cabbage maggot is available at: http://www.gov.mb.ca/agriculture/crops/insects/fad04s00.html

 

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