Story Posted: July 14, 2010

Insect Monitoring Update, July 14, 2010

Greetings! This week's insect update includes: Bertha armyworm, Wheat Midge, Thrips, Grasshoppers, Crop Profiles, Western Committee on Crop Pests, Wind Trajectories and Cereal Rust Diseases, and weather information.

Bertha armyworm (Mamestra configurata)
The degree-day accumulations for the predicted emergence of Bertha armyworm adults in 2010 are shown below. The prairies have accumulated 90-100% of the heat requirements necessary for adults to emerge from pupae in the soil.

Wheat Midge (Sitodiplosis mosellana)
Keep in mind that 10%, 50% and 90% emergence of adult wheat midge should occur after 693, 784 and 874 degree-days (base 5oC), respectively. Areas including the red, purple and pink portions of the map below indicate where sufficient heat units have accumulated for wheat midge to emerge as of July 12, 2010.

Thrips (Thysanoptera)
There have been a few reports of thrips in canola again this year. Thrip infested flowers tend to result in curled & distorted pods (see below), which in turn, are predisposed to drop prematurely. Thrips are minute, slender-bodied insects with rasping-sucking mouthparts and feed by rasping the surface of canola buds and sucking up the liberated plant fluid. When population levels are high, thrips can also be found feeding on exposed leaf surfaces. Both adults and nymphs cause damage. Flower thrips have a very extensive range of hosts, including cereals and broadleaved crops such as canola. Flower thrips feed on the thick fleshy petals, pistils, and stamens of the flower and buds.

The presence of thrips on canola was documented in the 1980's (Burgess and Weegar; Canadian Entomologist 120: 815-819). At that time, they found that there were nine species of thrips present in canola beginning in pre-bloom; Frankliniella tritici was the most common, followed by Thrips tabaci and Taeniothrips vulgatissimus. Burgess & Weegar felt that all three species may potentially be having an economic impact on canola because they were appearing throughout canola bloom. Our surveys in Saskatchewan in 1999 indicated that T. vulgatissimus was present in all canola fields sampled (n=30).

The density of thrips was estimated by counting the number of thrips on 20cm plant stalk samples (n=10 per field). The densities of thrips ranged from 2 to 44 thrips per 20 cm stalk. If extrapolated to the overall plant, densities could range from 50 to 2000 per plant. In 2000, only infested fields (n=12) between Duck Lake and Nipawin were examined. The number of thrips in these fields ranged from 2 to 120 thrips per raceme (20cm). Estimated damage (curled or missing pods) ranged from an average of 2% to 40%.

Grasshoppers (Orthoptera: Acrididae)
As of July 12, the model predicted that 3.4% of the eggs had not yet hatched. The model predicts that the majority of the grasshopper populations is at 3rd(28.9%), 4th (37.2%), or 5th (19.1%) instar stages. Approximately 1.7% of the population is at the adult stage.

	Prov Location Average of % 1st Average of % 2nd Average of % 3rd Average of % 4th Average of % 5th Average of % Adult MB Brandon 0 0 0.38 54.7 40.0 4.9 MB Carman 0 0 0 16.8 65.6 17.7 MB Dauphin 0 0 1.0 25.0 65.7 8.2 MB Melita 0 .06 5.4 59.7 29.6 5.3 MB Swan River 1.3 7.7 42.3 14.1 34.6 0 SK Estevan 0 0 2.05 19.5 67.8 10.7 SK Kindersley 5.4 8.1 21.6 32.4 32.4 0 SK Maple Creek 6.1 7.3 24.4 48.8 13.4 0 SK Melfort 2.6 7.5 51.8 32.2 5.9 0 SK Prince Albert 0 1.6 31.7 55.6 11.0 0 SK Regina 0 .06 1.7 77.5 20.7 0 SK Rosetown 0 1.2 21.97 61.6 15.2 0 SK Saskatoon 0 1.2 8.8 65.5 24.5 0 SK Scott 1.3 .23 35.7 28.98 5.4 0 SK Swift Current 3.99 39.9 37.9 15.97 2.0 0 SK Val-Marie .33 1.5 25.9 59.7 12.5 0 AB Calgary 6.8 15.2 40.5 20.3 0 0 AB Edmonton 0 5.8 53.8 32.7 0 0 AB Fairview .61 1.5 56.5 36.5 4.8 0 AB Fort Vermilion 3.2 1.9 33.3 46.8 14.8 0 AB Grande Prairie 5.6 15.6 56.9 20.1 0 0 AB Halkirk 24.6 0 30.1 16.4 0 0 AB High Level 5.6 19.6 51.7 22.3 .83 0 AB Lethbridge 0 4.96 29.1 43.97 21.99 0 AB Manning 3.3 9.8 55.5 26.1 0 0 AB Medicine Hat 0 3.03 12.7 58.6 25.7 0 AB Red Deer 0 8.8 46.9 13.2 0 0   Average 2.6 6.0 28.9 37.2 19.1 1.7

Crop Profiles. This from the Pest Management Centre website:
Crop profiles are documents that provide crop production and pest management information on a commodity basis. National in scope, they identify gaps in pest management and issues faced by growers. Click for crop profile information in the Agri-Food Canada website.

The baseline information provided in crop profiles supports the development of risk reduction strategies as well as regulatory work of the Pest Management Regulatory Agency (PMRA) of Health Canada. They are a source of current pest management information for Agriculture and Agri-Food Canada (AAFC), PMRA, provinces, industry, growers and grower organizations. Crop profiles are developed through an extensive consultative process and are reviewed by industry and provincial specialists. Detailed pest management data is collected in the main provinces producing a particular commodity by means of focus group completion of a survey tool, the Canadian Expert Poll on Crop Protection, developed by the PMRA. Completed crop profiles undergo regular review and updates.

There are currently Crop Profiles available for 29 crops, including canola, lentils, peas and wheat. For further information, please contact the crop profile co-ordinator Marilyn Dykstra (click to email Marilyn).

Western Committee on Crop Pests - Guide
John Gavloski recently updated the Cereal Crops and Grain Corn chapter for the WCCP’s “Guide to Integrated Control of Plant Pests”. The revised chapter will be available as soon as it is posted on the Western Forum on Pest Management website: http://www.westernforum.org/

Wind Trajectories and Cereal Rust Diseases
You may recall that the utility of wind trajectories, initially designed to track migrations of Diamondback moth into Canada, is also being assessed as an early-warning system for cereal rust diseases by Kelly Turkington (AAFC-Lacombe). Kelly just prepared this update for last week:

Cereal rusts represent a unique challenge for western Canadian cereal producers. In contrast to cereal leaf spot diseases and fusarium head blight, most cereal rusts do not typically overwinter in western Canada. Thus, crop rotation does not reduce the risk of rust outbreaks and as a consequence effective management of cereal rusts depends on either growing resistant varieties (if available) or applying an in-crop fungicide application for susceptible varieties.

The choice of which variety to grow is a relatively easy decision, which can be made during the previous fall and winter. However, the decision to spray a fungicide can be difficult to make, especially during a busy growing season. Whether to spray a fungicide will depend on the when disease appears in the crop and its level, weather conditions, the variety being grown, crop yield potential, and commodity price.

The ultimate goal of using a foliar fungicide is to protect green leaf area in the upper cereal canopy since these leaves contribute most to yield and grain filling. Routine scouting will be a key strategy to determine whether there is a risk of rust in any individual crop and whether fungicide is needed to protect the upper leaves of the cereal canopy. In general, cereal rusts, especially for wheat and barley, will overwinter on cereals and grasses in the southern USA and northern Mexico, although stripe rust can also overwinter in the Pacific Northwest (PNW) and California. Rust spores (also known as urediniospores) are blown northward by wind currents, affecting successive northerly winter and spring cereal crops. In the prairie region, rust spores will typically arrive in mid to late June.

Spread of cereal rusts into western Canada from locations in the USA will depend on the following factors:

• Disease severity and pathotypes at the point of origin
• Release and turbulent transfer of spores into upper atmosphere air parcels
• Movement and direction of air parcels
• Spore survival during long distance transport
• Deposition of spores over at risk locations in western Canada
• Crop growth stage for at risk locations
• Prevailing weather conditions for at risk locations

Risk Interpretation Summary for the Period July 1 - 7, 2010

• Stripe rust from the Pacific Northwest (PNW) – Low to moderate risk for the week
• Cereal rusts from the south and central Midwest regions of the US – Limited risk for stem rust; low to moderate risk for stripe and leaf rust

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