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Manitoba Agriculture, Food and Rural Initiatives

Manitoba Insect Update

July 27, 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

Aphids are becoming more noticeable in some cereal fields in the eastern part of the province. Soybean aphid has been found in Manitoba, but only at very low levels.

Recent Insect Concerns and Observations

Aphids on soybeans: The first soybean aphids for this year have been found in a field in the Roland area. They have so far only been found or reported from this one field, and were in very low numbers; most plants had none, a few plants had very small colonies. Agronomists and farmers should be checking fields for soybean aphids, but so far there is nothing significant to report.
Aphids in cereals: Aphid populations have become noticeable, although not yet economical, in some cereal fields. Most reports have been from the eastern region of the province, particularly the Morris area. Bird cherry-oat aphid, which is a darker aphid, appears to be the dominant species in many of these fields. They are a darker shade of green than many of the other aphid species common on cereals and sometimes look almost black. The economic threshold for aphids in cereal crops is 12-15 per stem prior to the soft dough stage. Once cereal crops reach the soft dough stage aphid control is no longer likely to be economical.

Bird cherry-oat aphid

Wheat Midge: Wheat midge emergence is expected to be anywhere from 50% complete to full emergence, based on degree day accumulation. Maps can be viewed at: http://www.cwb.ca/public/en/farmers/weather/midge/
A reminder that once the wheat crop has flowered (the heads will have anthers), the wheat heads are no longer susceptible to damage from wheat midge. Insecticide applications beyond the flowering stage, or when wheat midge levels are below economic threshold, are not recommended as they will not provide an economic return. Insecticide applications for wheat midge will also adversely affect parasitic wasp levels. Parasitic wasps can regulate wheat midge populations to below economic levels. Insecticides applied late or when wheat midge levels are low can cause more harm than good by destroying these natural enemies, reducing the natural controls available in subsequent years.


Surveys and Forecasts

Bertha Armyworm Forecasting: Counts of moths from pheromone-baited traps continue to increase in some regions, but still rate as low risk. Highest cumulative counts so far have been from the South Parkland region; Hamiota (277), Miniota (240), and Elkhorn (234). A trap in the North Parkland near Mink Creek has a cumulative count of 188. These still rate as low risk (less than 300). Based on this, we are not expecting it to be a bad year for bertha armyworm. Data can be viewed at:
https://www.gov.mb.ca/agriculture/crops/insects/bertha/index.html

Grasshopper Survey: A reminder for farm production advisors and those wanting to participate in the annual grasshopper survey that counts are done during August, when the majority of grasshoppers are in the adult stage. This year grasshopper development is later than normal, so in some areas counts may have to be delayed until adult grasshoppers are prevalent. The grasshopper survey protocol is located at: https://www.gov.mb.ca/agriculture/crops/insects/fad95s00.html