Insects: Cutworms and flea beetles on canola continue to be the insects of greatest concern. The cool, damp weather from the last few days would have slowed cutworm feeding, and the soil moisture, where not excessive, may help the plants compensate for feeding. Cutworm levels are quite variable, hard to find in some fields, more noticeable in others. So scout for potential cutworm feeding on emerging plants and dig for the larvae if you find an area that is showing signs of cutworm feeding. Precautionary insecticide applications, if cutworm levels are not economical, is not encouraged because of the potential damage to beneficial invertebrates.
Plant Pathogens: Rain has not only provided enough moisture for crops, but also for pathogens causing various crop diseases. Look for early signs and symptoms of diseases in crops. Scout! Scout! Scout!
Submitted by: John Gavloski, Entomologist & Pratisara Bajracharya, Field Crop Pathologist, Manitoba Agriculture
Fusarium head blight risk for wheat is moderate to low in different areas of Manitoba. Most of the wheat crops have finished flowering and thus at low risk. By end of the month, Fusarium head blight risk maps may not be needed.
Grasshoppers continue to be a concern in some fields.
Canola growers should be checking canola for Lygus bugs. Lygus can potentially be of concern when they feed on the pods of canola if levels are high, although feeding to flowering crops is not likely to be economical as canola has a very good ability to compensate for damage to flowers, especially when soil moisture is good. So far Lygus levels appear to be below economic levels in canola, with a few exceptions in the Eastern part of Manitoba.
Note: For those monitoring traps for bertha armyworm, the traps can be removed after you do your counts this week. We have enough weeks of data to know what the regional risks are. Overall trap counts in Manitoba were quite low this year. A map of the cumulative counts, as of July 28th, is posted in the update, and risk maps are also posted at the following MAFRD website (the July 28th map will be posted tomorrow): http://www.gov.mb.ca/agriculture/crops/insects/bertha-armyworm-forecast.html
Submitted by: John Gavloski, Entomologist & Vikram Bisht, Pathologist, MAFRD
Insect and disease activity continues to be low on crops in Manitoba.
The cool temperature has slowed the emergence of many insects.
There is no evidence to date of any major movement of insects that get blown into Manitoba form the southern U.S., such as diamondback moth and aster leafhopper.
The update provides information on the following topics:
Grasshoppers: When will emergence likely start? Degree day models can be used to forecast anticipated dates of emergence for these pest species. Based on such models it will likely be early-June before we see a start to the emergence of these species of grasshoppers in most areas.
Recent Rain and Grasshoppers? The recent rains will likely do very little to negatively impact the survival of our pest species of grasshoppers.
Insect Monitoring Programs. Updates on diamondback moth, wireworms & cutworms.
The 2 main species of flea beetles in canola in Manitoba are the striped and crucifer flea beetles.
These are potentially a concern from the time canola emerges until about the 3 to 4 leaf stage in canola.
Seed treatments will provide early season control. None of the seed treatments currently registered work as well under cool, wet conditions as they do in warmer, drier conditions.
Insecticide effectiveness can vary with the species of flea beetle. Neonicotinoid-based seed treatments (Helix, Prosper) work well against crucifer flea beetle, but control will be less on striped flea beetle. This is not a developed insecticide resistance, just natural variation in effectiveness between species.
Are larvae of click beetles. Will have 3 small pair of legs at the front the body, but don’t have the fleshy prolegs at the back like cutworms.
Feeding is all underground.
Foliar insecticides will not be effective.
Seed treatments can stop wireworms from damaging young crops, however current seed treatments result in little mortality of the wireworms.
Are hard to monitor; bait balls can be used, but growing vegetation and other sources of CO2 near a bait ball will compete for wireworms and reduce effectiveness.
Practices that result in quick germination and early growth can help minimize damage form, wireworms.
It will probably be early-June before we see much hatch of our potential pest species of grasshoppers this year.
Any larger grasshoppers seen in May will not be pest species.
Heavy rains and standing water will not kill grasshopper eggs. Newly hatched grasshoppers, however, are quite susceptible do being killed because of heavy rains. So heavy rains in April or May will likely do little to our pest species of grasshoppers. Heavy rains in June could potentially reduce populations significantly.
Areas that had lush green vegetation late last year, such as along field edges, are more likely to have higher concentrations of grasshopper eggs, and early-season grasshopper levels will be heaviest in these areas. These areas should be monitored in June.
If grasshopper control is needed:
Control of young grasshoppers is more effective than controlling adults
Control may only be needed along field edges or areas where they are concentrated early.
Bran baits (with an attractant that lures the grasshopper to the bait) as well as foliar sprays are available.