Story Posted: August 18, 2010

Insect Monitoring Update, August 18, 2010

Please enjoy the penultimate weekly update for the year! This week's insect update includes: Flea beetles, Grasshoppers, Lygus bugs, Large numbers of ground beetles.

Flea beetles (Chysomelidae: Phyllotreta striolata, Phyllotreta cruciferae, Pyslliodes punctulata)
Newly emerging flea beetles were observed again this week in canola. Research by Julie Soroka of AAFC has shown that high numbers of flea beetles (up to 350 per plant) on canola ranging in growth stages 5.2-5.3 (estimated using Harper and Berkenkamp 1975) and growing under adequate moisture suffered no measurable losses.

Grasshoppers (Orthoperta: Acrididae)
Grasshoppers suffering from Entomophthora grylli Fres. have been observed in several field in Saskatchewan. Dead grasshoppers similar to the photo below were noted in these fields. Here's the abstract from a paper that Pickford and Riegert wrote in 1964:

R. Pickford and P. W. Riegert 1964. The Fungus Disease Caused by Entomophthora grylli Fres., and its Effects on Grasshopper Populations in Saskatchewan in 1963. The Canadian Entomologist 96: 1158-1166.

Abstract: A widespread epizootic of the fungus disease caused by Entomophthora grylli Fres. occurred among grasshoppers in Saskatchewan in 1963. Camnula pellucida (Scudder), in particular, suffered high mortality and was nearly wiped out in those areas of central and east-central Saskatchewan where heavy infestations had been present. Weather was warm and humid during the outbreak with above normal rainfall in the seriously affected areas.

Field-cage studies showed that proper timing of rainfall was essential for continuation and spread of the disease. Rainfall shortly after death of the diseased grasshopper induced profuse growth of conidiophores along with intense discharge of conidia. When death occurred during hot, dry weather, no sporulation was noted and the insects rapidly dried up. The interval from infection to death of the grasshopper was about 13 days.

The fungus disease also developed in natural field populations of Melanoplus bivittatus Say, but none was noted in field cages where this grasshopper was being reared alongside of or together with C. pellucida that were dying continuously from the disease; this suggests that different strains of E. grylli were involved.

As of August 16, the grasshopper model predicted that 1.7% of the population were at 4th instar, 10.8% were at 5th instar, and 87.4% of grasshoppers were at adult stages (Refer to table below for site predictions). In comparison, grasshoppers collected from the field on August 11, 2010, from sentinel sites in Saskatchewan were less advanced compared to the model predictions. The field collected grasshoppers sampled averaged as the following stages: 20.1% at fourth instar, 37.6% at fifth instar and 35.4% were at adult stage (N=189 grasshoppers from 7 sites).

	Prov Location Average of % at 4th instar Average of % at 5th instar Average of % at Adult stage AB Calgary 6.0 30.0 64.0 AB Edmonton 6.3 5.0 88.8 AB Fairview 0.0 2.4 97.6 AB Grand Prairie 6.0 22.6 71.4 AB Halkirk 2.0 34.0 64.0 AB High Level 0.7 33.6 65.6 AB Lethbridge 0.0 0.0 100 AB Manning 3.4 72.9 19.5 AB Medicine Hat 0.0 0.0 100 AB Red Deer 19.3 64.9 15.8 MB Brandon 0.0 0.0 100 MB Carman 0.0 0.0 100 MB Dauphin 0.0 0.0 100 MB Melita 0.0 0.0 100 MB Swan River 0.0 2.9 97.1 SK Estevan 0.0 0.0 100 SK Kindersley 0.0 3.3 96.7 SK Maple Creek 0.0 1.4 98.6 SK Melfort 0.0 3.8 96.2 SK Prince Albert 0.0 0.0 100 SK Regina 0.0 0.0 100 SK Rosetown 0.0 0.0 100 SK Saskatoon 0.0 0.0 100 SK Scott 0.0 1.4 98.6 SK Swift Current 0.0 2.2 97.8 SK Val-Marie 0.0 0.0 100   Average 1.7 10.8 87.4

Also, from John Gavloski who reported from Manitoba that, "We were out collecting on Wednesday and Thursday this week for a pre-harvest diagnostic clinic, and a large proportion of the grasshoppers we collected (probably over half) were still nymphs. The twostriped and migatory grasshoppers were the dominant species; with the twostriped being the most common species in most of our collections. We were surprised by the number of younger grasshoppers." John sent along a photo taken in a bean plot.

Lygus bugs (Miridae: Lygus spp.)
The Canola Council of Canada this week reported that, "much of southern and central Alberta and parts of western Saskatchewan still have high levels of lygus bug feeding. Lygus bug numbers are up to 10 times economic control thresholds in fields from Crossfield to Penhold, Alberta."

Large numbers of ground beetles (Coleoptera: Carabidae)
Kevin Floate (AAFC-Lethbridge) passed along the following: "Albertan carabidophiles received scattered reports last week concerning large numbers of ground beetles at various locations in south-central Alberta (so far, near Pickardville, Vegreville, Camrose, Wetaskawin). The species has been identified from two locations as Amara littoralis (6-7mm in length). Species of ground beetles rarely reach such high numbers and tend to be helpful. They often eat pest insects and the seeds of various weed species. They are not crop pests nor do they sting or bite. The current large numbers are likely a temporary phenomenon that will soon pass."

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