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Manitoba Insect and Disease Update: April 27, 2012

Compiled by:

  • John Gavloski, Entomologist
    Manitoba Agriculture, Food and Rural Initiatives
    Phone: (204) 745-5668
    Fax: (204) 745-5690.
  • Holly Derksen, Plant Pathologist
    Manitoba Agriculture, Food and Rural Initiatives
    Phone: (204) 750-4248
    Fax: (204) 745-5690

To report observations on insects or plant pathogens that may be of interest or importance to farmers and agronomists in Manitoba, please send messages to the above contact address.

To be placed on an E-mail list so you will be notified immediately when new Manitoba Insect and Disease Updates are posted, please contact John Gavloski at the address or numbers listed above.

Recent Insect and Plant Pathogen Activity

Canola

Flea beetles: Striped flea beetles (Phyllotreta striolata) have been emerging and feeding on volunteer canola since late-March. We often see striped flea beetles emerge earlier than the crucifer flea beetle (Phyllotreta cruciferae) which can be the more damaging species of flea beetle in Manitoba.

The seed treatments for protecting canola from flea beetle feeding generally last 3 to 4 weeks. When canola is seeded under conditions that result in quick germination and early growth the seed treatments can protect the plants from flea beetle feeding until the plants have several true leaves, after which they can compensate well for flea beetle feeding. Seeding under conditions that may result in slow emergence and slow early growth could mean that that the seed treatment wears out while the seedlings are still vulnerable to flea beetle feeding. So the level of flea beetle feeding may be something to pay attention to if early-seeded canola takes a long time to get established.

In the photo below, the 2 flea beetles at the top are striped flea beetles and the flea beetle below is a crucifer flea beetle. The photo also shows the feeding pits caused by flea beetles.

Surveys and Forecasts

Diamondback moth Present Early in Manitoba in 2012: Diamondback moths were first detected in Manitoba in a pheromone-baited trap near Carman during the week of March 22-31; 2 moths were caught in the trap in this initial week. Since then 36 more moths have been caught in this trap. A trap near Morris set up in mid-April caught 48 diamondback moths during the week of April 16th to 22nd.

Diamondback moths are present early this year. What this means for canola growers once the crop emerges is hard to say until we start getting some more data from across the province over the next couple of weeks. What remains to be determined is how widespread are these early populations, how well will they do establishing this first generation, and what will the populations of parasitoids that regulate their populations be like.

Table 1. Highest cumulative trap counts for diamondback moth in Manitoba as of April 24, 2012

Location Cumulative Trap count
Morris 48
Carman 38
Sewell 21
St. Adolphe 7

A reminder that traps for monitoring the presence of adults of diamondback moth should now be set up.

Aster Leafhoppers: Large populations of aster leafhoppers have recently been reported in southwest Minnesota. Although aster leafhopper can potentially overwinter to some degree on the Canadian prairies, usually overwintering survival is considered to be low and the high majority of what ends up here moves in from the south. We will keep watching the progression of these populations of aster leafhopper.

Research

We want your insects! There are several research projects planned for this summer where we are trying to collect insects or looking for fields to take samples from. So if you come across fields where the following insects are easy to find, or the following cropping situation are present, please let me know. The information we gain from these studies will be of future help to you.

Cutworms: Cutworms are needed for a project studying parasitism in our local populations of cutworms. This project aims to gain a better understanding of cutworm parasitoids, and whether there are ways we can create conditions to enhance levels of these parasitoids. So please let us know if you are finding cutworms in any fields. Save some for the study, or we will come to the field to collect them. Please contact Dr. Barb Sharonowski at the University of Manitoba (204-474-7485) or myself (204-745- 5668).

Wireworms: Wireworms are once again being collected for a survey on the species of wireworms found across Canada. Having our local species known will better enable us to predict the success of various management strategies. How to collect wireworms and where to send them is described on page 14 and 15 of the following Wireworm Field Guide. Or contact me and we can come collect some.

Red Clover fields: We are trying to determine if we potentially have an insect called red clover casebearer in Manitoba, and if so in what levels. If you happen to know of any fields with lots of red clover, white clover, or alsike clover, and don't mind having a trap placed in the field, please contact me and let me know.

Soybeans/alfalfa/pea fields in close proximity: For a study on the population dynamics of aphids and some of their natural enemies, we are looking for soybean and pea fields next to or close to alfalfa fields. Having fields of all 3 crops in close proximity would be even better, and ideal for the study. If you have such a situation and don't mind entomologists removing some of the insects form your field periodically, please contact Dr. Alejandro Costamagna at the University of Manitoba (202-474-9007) or myself (204-745-5668).

So instead of complaining about the insects in your fields this summer, donate them to science.


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