Story Posted: July 28, 2010
Insect Monitoring Update, July 28, 2010
Greetings! This week's insect update includes: Diamondback Moth, Grasshoppers, Wheat Midge, and West Nile Mosquito.
Diamondback Moth (Plutella xylostella)
High numbers of diamondback moth larvae have been reported in eastern Manitoba, in Saskatchewan and in southern Alberta this past week. While on survey, AAFC staff based at Saskatoon reported more than 500 DMB larvae per 25 sweeps compared to 2009 when mean DMB counts of 3.2 larvae per 25 sweeps were observed (ranging up to a maximum of 27 larvae per 25 sweeps). Ross Weiss noted that, given high numbers of larvae have been collected prior to July 21, 2010, one might expect pupation and another generation of adults to occur before the end of July with the potential to result in high larval densities in early August as the majority of Saskatchewan's canola fields enter the pod stage.
While a sweep-net is efficient for detecting larvae, inspection and ultimately pulling and tapping whole plants is the recommended method to monitor for diamondback moth larvae (click to view a PDF of the Diamondback Moth Monitoring Protocol).
The economic threshold for diamondback moth larvae is applied at mid-pod stage in canola. As canola matures, normal senescence of leaves combined with the availability of juicy, developing pods can result in larvae feeding on the exterior of pods. Severely damaged pods fail to produce healthy seed and later these same pods are prone to shattering in dry, hot, windy weather but also when swathed or direct-harvested.
Keep in mind that applying the economic threshold is important economically AND biologically –
beneficial wasp species (Diadegma insulare, Microplitis plutellae, Diadromus subtilicornis) which specifically seek out and parasitize diamondback moth larvae and pupal stages are out in fields plus species of flies, wasps, lacewings, plant bugs, pirate bugs, beetles, and spiders all prey on diamondback moth larvae!
Grasshoppers (Orthoptera: Acrididae)
As of July 26, the model predicted that the grasshopper population would be at the 4th (22.0%) and 5th (42.6%) instar stages while 26.5% of the population would be adults.
 |
|
|
| |
| Prov |
Location |
Average of % at 4th instar |
Average of % at 5th instar |
Average of % at Adult stage |
| MB |
Brandon |
0.0 |
22.6 |
77.4 |
| MB |
Carman |
0.0 |
1.5 |
58.1 |
| MB |
Dauphin |
0.0 |
14.0 |
86.0 |
| MB |
Melita |
0.6 |
25.7 |
69.5 |
| MB |
Swan River |
19.7 |
42.1 |
36.8 |
| SK |
Estevan |
0.0 |
4.9 |
86.1 |
| SK |
Kindersley |
21.2 |
39.4 |
36.4 |
| SK |
Maple Creek |
10.1 |
68.4 |
15.2 |
| SK |
Melfort |
21.1 |
70.6 |
5.7 |
| SK |
Prince Albert |
8.1 |
81.1 |
10.8 |
| SK |
Regina |
0.0 |
57.1 |
42.9 |
| SK |
Rosetown |
4.7 |
75.4 |
19.9 |
| SK |
Saskatoon |
2.2 |
61.0 |
36.8 |
| SK |
Scott |
7.5 |
58.3 |
0.0 |
| SK |
Swift Current |
52.1 |
41.7 |
4.2 |
| SK |
Val-Marie |
3.2 |
81.9 |
14.9 |
| AB |
Calgary |
53.8 |
23.1 |
0.0 |
| AB |
Edmonton |
54.8 |
33.3 |
0.0 |
| AB |
Fairview |
49.8 |
46.1 |
2.3 |
| AB |
Grande Prairie |
57.5 |
33.3 |
0.0 |
| AB |
Halkirk |
18.9 |
45.3 |
0.0 |
| AB |
High Level |
53.5 |
37.1 |
0.0 |
| AB |
Lethbridge |
9.3 |
63.1 |
27.5 |
| AB |
Manning |
62.6 |
26.5 |
0.0 |
| AB |
Medicine Hat |
3.1 |
39.6 |
57.3 |
| AB |
Red Deer |
58.6 |
15.5 |
0.0 |
| |
Average |
22.0 |
42.6 |
26.5 |
|
|
|
|
|
Grasshoppers collected on 22 July 2010 from sentinel sites near Saskatoon were less advanced compared to the model predictions. The grasshoppers sampled averaged as the following stages: 8.6% at first instar, 12.3% at second instar, 20.6% at third instar, 28.3% at fourth instar, 24.3% at fifth instar and 5.9% were at adult stage (N=325 grasshoppers from 7 sites).
Wheat Midge (Sitodiplosis mosellana)
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 26, 2010.
West Nile Mosquito (Culex tarsalis)
The Public Health Agency of Canada (www.phac-aspc.gc.ca/wnv-vwn/index-eng.php) reports no confirmed cases of West Nile virus in humans in 2010. The degree-day map, produced by David Giffen for the health agencies, indicates the regions of the prairies and the respective heat accumulations for Culex tarsalis. Areas in Manitoba are now accumulating sufficient heat units for Culex tarsalis.
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