Manitoba
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Manitoba Agriculture, Food and Rural Initiatives

Manitoba Insect Update

June 17, 2008                   

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.

To be placed on an e-mail list to be notified when new Manitoba Insect Updates are posted, please contact John Gavloski at the address or numbers listed above.


Summary

Cutworms and flea beetles continue to be of concern in localized area. Counts of diamondback moth adults in pheromone-baited traps have increased in the southeast. 

Recent Insect Concerns and Observations

Cutworms: Cutworm populations have still been a concern in many fields, mainly in the central region of the province. Consider the staging of cutworms however before making control decisions this late in the spring. Species that overwinter as larvae, such as dingy cutworm, will likely be fully grown and may be starting to pupate already. So just because a field is showing cutworm feeding, if young cutworms that could still be potentially doing more feeding damage are not present, there would be no economic benefit to treating the field with insecticide.

 

Surveys and Forecasts

Diamondback moth: Counts of adult diamondback moth have remained low across most of Manitoba. However, a few higher counts have been recorded from traps and adults observed in fields in the southeast part of the province. The highest counts so far from traps in Manitoba are: 41 near Steinbach, 31 near Emerson, and 15 near Niverville. These counts are not alarming, but agronomists and those growing cruciferous crops such as canola may want look for larvae when scouting fields. Data from the diamondback moth trapping program and an interpretation of the data are available at: https://www.gov.mb.ca/agriculture/crops/insects/db/index.html

Bertha Armyworm: Traps for monitoring adults of bertha armyworm are now set up. So far there are no reports of moths having been captured in these traps. The cool spring will have delayed emergence of the  moths.

Grasshoppers and other insects: Our species of grasshoppers that potentially could be pests seem to be early in their emergence still. In most areas that have been assessed counts have been low, although I have heard of some higher counts in the western part of the province. Most of the grasshoppers we are finding are in their first or second (out of 5) juvenile growth stages. So they don’t have wings and are not yet moving far from overwintering sites. It would be too early to be concerned over control of such populations, and in areas that we have looked at the current numbers would not be there to justify it.

My summer student has been checking cereal fields again this year for the possible existence of cereal leaf beetles in Manitoba. There has never been a report of cereal leaf beetle in Manitoba, but we check for it annually since it has been located in some counties of North Dakota. So far we have not been able to detect cereal leaf beetle in any fields we have looked at. So if you see someone taking sweep net samples in cereal crops over the next couple of weeks, cereal leaf beetle could be what they are looking for. 

Insect Identification Quiz

 

Question: These grasshoppers were among some spotted while sampling roadside vegetation last week. Are any of these potential pest species?

Answer: The grasshopper with the shorter antennae is a juvenile of the twostriped grasshopper. This is a species that when populations get high enough can be a crop pest. The grasshopper with the longer antennae is a species of katydid. The antennae of katydids are quite long, often as long as or longer than the body. None of our species of katydids are harmful to crops, even when populations are high. All of our potential pest species of grasshoppers belong to a group known as the short-horned grasshoppers. As the name implies, they all have short antennae.

While sampling the ditches and field edges for grasshoppers in the central part of Manitoba recently, the majority of grasshoppers present in many areas were katydids. Don’t confuse these with grasshoppers that potentially could be pests.