Story Posted: August 04, 2010
Insect Monitoring Update, August 04, 2010
Greetings! This week's insect update includes: Pre-Harvest Intervals, Lygus bugs, Economic thresholds, Grasshoppers, 2010 Grasshopper Forecast, Wheat Midge.
Pre-Harvest Intervals
A reminder to pay attention to the interval between insecticide application and swathing or direct-harvesting. The shortest pre-harvest interval for available insecticides registered for use in canola is seven days.
Lygus bugs (Lygus spp.)
Economically damaging populations of lygus bugs have been sprayed in canola in the south Peace River region of Alberta this past week. Producers in this area are grappling with drought-stressed canola and high numbers of lygus. Refer to the table below (courtesy Manitoba Agriculture, Food and Rural Initiatives) for updated economic threshold values for lygus bugs in canola:
John Gavloski reported this week the following: "Economical levels of lygus bugs continue to be found in some fields of confection sunflowers (Refer figure below, left). Where economical, insecticides should ideally be applied between the R4 to R5.1 stage. Evening application is preferred. Lygus bugs are not known to be of economical concern in oilseed sunflowers.
Another plant bug called ragweed plant bug, Chlamydatus associatus, can also commonly be found on sunflower heads this time of year. Ragweed plant bugs are not known to be harmful to sunflowers, although no research has been done on its feeding habits on sunflowers. Below are pictures of an adult lygus bug and a ragweed plant bug on sunflowers."
"Small insects called minute pirate bugs (see figure below) can also commonly be found on sunflowers this time of year. These are beneficial insects that eat other insects and insect eggs, and are found in many crops. In sunflowers, they have been recorded as feeding on the eggs and young of banded sunflower moth, although they would likely feed on any insect egg or small, soft bodied insects they could catch on the plants."
Grasshoppers (Orthoptera: Acrididae)
Just to refresh the topic, the 2010 Grasshopper Forecast Map is below. Grasshopper reports surfaced this week from various locations in Saskatchewan and in the BC Peace. Producers reported grasshoppers at some sites in Saskatchewan and control applied for grasshoppers in lentils near Swift Current SK. Grasshoppers (4th and 5th instar stages) were readily found in roadside sites near Lethbridge AB, Maple Creek SK, and Swift Current SK last week. In the BC Peace, grasshoppers have done damage to dry cereals and forage grasses west of Dawson Creek (Groundbirch area) and the Golata Creek area (East of Fort St. John and north of the Peace River).
As of August 3, the grasshopper model predicted that 5.8% of the population were at 4th instar, 37.3% were at 5th instar, and 54.9% of grasshoppers were at adult stages (Refer to table below for site predictions). In comparison, grasshoppers collected from the field on 28 July 2010 from sentinel sites in Saskatchewan were less advanced compared to the model predictions. The field-collected grasshoppers sampled averaged as the following stages: 33.9% at fourth instar, 24.6% at fifth instar and 19.7% were at adult stage (N=183 grasshoppers from 7 sites).
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| Prov |
Location |
Average of % at 4th instar |
Average of % at 5th instar |
Average of % at Adult stage |
| AB |
Calgary |
19.6 |
58.8 |
13.7 |
| AB |
Edmonton |
4.9 |
76.8 |
12.2 |
| AB |
Fairview |
1.7 |
79.2 |
19.1 |
| AB |
Grand Prairie |
12.6 |
80.5 |
0.0 |
| AB |
Halkirk |
30.8 |
59.6 |
5.8 |
| AB |
High Level |
19.2 |
69.0 |
10.4 |
| AB |
Lethbridge |
0.0 |
28.5 |
71.5 |
| AB |
Manning |
26.6 |
58.4 |
7.5 |
| AB |
Medicine Hat |
0.0 |
4.0 |
96.0 |
| AB |
Red Deer |
17.2 |
63.8 |
0.0 |
| MB |
Brandon |
0.0 |
0.1 |
99.9 |
| MB |
Carman |
0.0 |
0.0 |
100 |
| MB |
Dauphin |
0.0 |
1.1 |
98.9 |
| MB |
Melita |
0.0 |
2.7 |
97.3 |
| MB |
Swan River |
2.7 |
48.0 |
49.3 |
| SK |
Estevan |
0.0 |
0.0 |
100 |
| SK |
Kindersley |
3.1 |
28.1 |
68.8 |
| SK |
Maple Creek |
6.4 |
14.1 |
79.5 |
| SK |
Melfort |
3.4 |
62.5 |
34.0 |
| SK |
Prince Albert |
0.0 |
40.9 |
59.1 |
| SK |
Regina |
0.0 |
0.0 |
100 |
| SK |
Rosetown |
0.1 |
28.8 |
71.1 |
| SK |
Saskatoon |
0.0 |
5.1 |
94.9 |
| SK |
Scott |
1.5 |
61.3 |
37.2 |
| SK |
Swift Current |
2.1 |
77.1 |
20.8 |
| SK |
Val-Marie |
0.1 |
20.3 |
79.7 |
| |
Average |
5.8 |
37.3 |
54.9 |
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Wheat Midge (Sitodiplosis mosellana)
This week’s degree-day map uses a different colour palette. The majority of the prairies have accumulated sufficient heat units for no less than 50-100% of wheat midge to emerge.
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