Manitoba
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Manitoba Agriculture, Food and Rural Initiatives

Manitoba Insect Update

July 20, 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.

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


Summary

Levels of barley thrips on barley and pea aphids on field peas continue to be of concern, primarily in the southwest. Cereal leaf beetle has been recorded in Manitoba for the first time in the Northwest.

Recent Insect Concerns and Observations

Barley thrips: There continues to be reports of high levels of barley thrips from the southwest region. A reminder that research has showed that treatment of barley for barley thrips is only effective if applied before heading is complete.
 
Aphids on peas: High levels of pea aphids are present in some field of field peas in the southwest. Some have been wondering about the ideal timing of control to maximize yield benefits should populations be above economic threshold. Research from Manitoba has found that yield was enhanced most when a single application was made as soon as 50% of the crop had young pods. Control at the early pod stage provides protection through the pod formation and elongation stages, which are very sensitive to aphid damage. Most of the damage that aphids do to peas is to the pods before they start to fill. If most of the pods have already started to fill, spraying may be too late and may not be economical.

Lack of insect pests currently in canola
: Some that have been out scouting canola fields have been commenting on how few pest insects are currently being found in flowering canola fields. Diamondback moth larvae are generally at very low levels, and lygus bugs currently have not been found to be abundant in canola. The reassurance that spraying for insects in canola during flowering is not likely to economical is good news for both canola growers and beekeepers. Keep up the good job with the crop scouting.

Cereal Leaf Beetle in Manitoba
: Cereal leaf beetle has been found in some cereal fields in the northwest. This is an insect that potentially can do economic damage to cereals, and has not been found in Manitoba before. Levels being found are not of economic concern to growers, but what is needed is to know the extent of the distribution in Manitoba. This is where farmers, agronomists, and others scouting cereal fields can help. Read the factsheet at the link below and get to know the appearance of the larvae and adults. Although the information regarding regulation is no longer current, the factsheet provides good photos of the adults, larvae and feeding. They are quite distinctive. Larvae are usually covered with a secretion of mucus and faecal material, giving them a shiny black, wet appearance. If you think you have these in a field, please contact myself or a MAFRI representative. You can send samples to myself or the Crop Diagnostic lab for identification if desired. If would be good if we can determine the extent of the distribution. We may also request some be collected to determine the level of parasitism. Parasites can be effective at reducing the effect of this insect, and knowing where it is occurring, and the level of parasitism, enables us to determine whether we should be attempting to introduce parasites into a region.
http://www.agf.gov.bc.ca/cropprot/clbeetle.htm

 

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 counts so far are from traps near Miniota (217), Elkhorn (193), Hamiota (187), and Russell (153). These still rate as low risk (less than 300), although weekly counts are still increasing and may not have peaked yet in some areas. Data can be viewed at:
https://www.gov.mb.ca/agriculture/crops/insects/bertha/index.html

Wheat Midge Emergence: The Canadian Wheat Board produces maps that predict based on growing degree days when wheat midge emergence should be starting and peaking. Maps will be updated regularly until the end of July. The maps show that enough degree days have been accumulated for wheat midge to be emerging in most wheat growing areas of Manitoba, and emergence may be at 50% or higher in some areas of southern Manitoba. Maps can be viewed at: http://www.cwb.ca/public/en/farmers/weather/midge/