Story Posted: June 09, 2010

Insect Monitoring Update, June 9, 2010

Across Saskatchewan and Alberta temperatures were 2-5°C below normal (Drought Watch website). Overall, May 2010 temperatures were similar to 2009, though in 2009 temperatures were coolest in southeast SK and MB. Environment Canada is forecasting above normal temperatures for the period of June to August (Environment Canada Seasonal Forecast). David Giffen has the degree-day database up and running again for 2010, so going forward we will be keeping track of insect development, starting with bertha armyworm this week.

In general though, it appears that eastern portions of the prairies are slightly ahead of the rest of us, as of Monday. See map below of degree-day accumulations (base 5°C).

1. Bertha Armyworm (Mamestra configurata)
You will recall that the adult counts in pheromone traps were very low across most of the prairies in 2009 (Figure 1 below). Degree-day accumulations for predicted emergence of adult bertha armyworm in 2010 (right-hand map in Figure 2) are slightly ahead of what we were seeing last year at this time (Figure 2). Southern MB has been accumulating more heat units than SK and AB so far this spring. The green-coloured pockets represent 45-60%; the light green represents 60-75%; and the yellow represents 75-90% of heat units required for adult emergence. There is also a small orange patch south of Winnipeg that suggests adults, if present, may begin to emerge soon in that area. So if they are not already in place, the pheromone traps should be installed shortly, especially in the eastern area of the prairies. Stay tuned for further updates.

2. Diamondback moth (Plutella xylostella)
There continued to be a few wind parcels arriving over SK and MB this past week, however, it looks like this trend will drop off over the next few days. Lloyd, Ross and I are in the process of completing a bio-climate model for Diamondback moth (DBM). Given the influx of adults in May this year, we were interested in using the model to predict the risk to canola due to the number of generations that could potentially occur by August. The objective was to determine if weather conditions might permit DBM to produce an additional generation before the end of the growing season (before August 31). More specifically, we were interested in the potential number of DBM generations at about the time that canola might be podding. The model was initialized with two start dates May 1 and May 15 (e.g. dates when adults arrived on the prairies). Current weather conditions to date were used to start the simulations, and Long-Term-Normal weather data were then used to extrapolate into the future. Ross provided two maps (below) that show the projected date of occurrence of the 4th generation (arriving adults plus three additional generations). The first map is a projection for DBM arriving on May 1. The map shows that a fourth generation could appear by August 11 in southeast SK and MB. In the scenario where DBM arrived on May 15, the model predicted that a fourth generation would occur approximately 1 week later. Given the Environment Canada forecast of above-normal temperatures for the summer of 2010, next week we will have data to compare DBM generation in years that had warmer growing seasons (such as 1998, 2006 and 2007).

3. Grasshoppers (Acrididae)
Last week, we provided some output from our grasshopper model to give you a sense of how potential grasshopper hatch was progressing this spring. In summary, the cool conditions have continued to delay grasshopper development. As of Monday, June 7th, the model predicted that less than 40% of the eggs have hatched. Percentage hatch ranges from 16% near Kindersley, SK up to 38% near Medicine Hat, AB and Brandon, MB.

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