Most of Saskatchewan is expected to escape major insect infestations in the coming growing season.
But Scott Hartley, the province’s insect specialist, has compiled forecasts that show some growers could face high numbers of wheat midge, grasshoppers, cabbage seedpod weevil and other pests.
It all depends on where the crop is and what the weather is like, Hartley said.
Wheat midge
“Wheat midge appears to be much improved,” he said. “We’re still in a position where there are hot spots and control will likely be required.”
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But the levels won’t be anything like last year, when the midge map showed a high risk throughout the moist dark brown, black and grey soil zones.
“Probably one of the things lacking in ’08 was parasitism,” he said.
Parasitic wasps lay their eggs inside midge larvae. The parasite is dormant over winter but in the spring grows quickly and destroys the midge. Benefits of the parasite aren’t seen until the following year.
Hartley said the conditions weren’t favourable for parasitism last year but are returning to normal this year.
He also said climatic conditions and crop staging are keys to midge control.
Dry conditions can delay midge development and early seeding can help the crop pass the susceptible stage before midge emerges.
This year, the highest risks are several rural municipalities around Saskatoon, Prince Albert and Yorkton.
Hartley said even if the risk is low, producers should be monitoring their fields because populations can rebound.
His map is based on about 450 samples, four from each RM used.
Grasshoppers
Saskatchewan Crop Insurance Corp. staff monitored 1,200 sites in late fall 2008 to observe adult grasshoppers and estimate populations for 2009.
Hartley said the highest numbers will be seen in the south, with severe risks from south of Swift Current to north of Elrose, and in the Lipton and Southey regions. The southeastern corner shows moderate risk.
Last year, control was required mainly in lentil crops, where the economic threshold is only two grasshoppers per sq. metre.
Hartley said producers looking for ways to save money should examine the grasshoppers in their fields to see if they really are pests. Not all species damage crops.
“It’s an opportunity to get a little better handle on what the populations (of different species) are” when the numbers are low, Hartley said.
There are some general rules of thumb to identify which grasshoppers are pests and which are not.
For example, any grasshopper flying before June is not a pest, and any grasshopper making a sound is not a pest.
The grasshopper identification and control guide, produced by the federal and provincial governments and Pulse Canada, explains how to identify species and what to do about them. It is available from the Agriculture Knowledge Centre in Moose Jaw.
Bertha armyworm
There is good news on the Bertha armyworm front.
“We definitely seem to be on the end of the outbreak,” Hartley said.
Typically, there is a two- or three-year cycle of high numbers followed by a 10-year break.
“We saw greatly reduced numbers in ’07 and even more in 2008.”
There is still potential for problem areas but officials will monitor the situation with pheromone traps in June and July.
Cabbage seedpod,pea leaf weevil
Weevils are on the move.
The cabbage seedpod weevil, which prefers canola and brown and oriental mustard, has moved in from Alberta and is heading north and east.
“It’s making some pretty good inroads,” Hartley said.
The weevil has been found as far east as Regina and Indian Head and as far north as Lloydminster. It is expected to be at its highest numbers in the Swift Current area.
Hartley said the economic populations are still largely in the southwest and producers will want to keep an eye on their crops.
Cabbage seedpod weevils can also be found in cruciferous weeds such as wild mustard and stinkweed. That sets them apart from other weevils.
The pea leaf weevil has also moved in from Alberta and is expanding its zone.
“It’s fairly new to us in the province,” Hartley said.
Research is still determining what chemical control could be used for pea leaf weevil.
Right now, the control is a seed treatment and foliar spray.
Dale Risula, special crops specialist, told a recent pulse growers’ symposium that early scouting is critical to detect this weevil.
Root maggots
High levels of root maggots in canola were a concern in central and northern areas with moist conditions last year.
“If people do perceive they’ll be in the same situation again, their only option is seeding options,” Hartley said.
By that he means seeding at heavier rates.
There is no chemical control, and producers should consult the Canola Council of Canada for more information and advice.
Other pests growers will contend with include cutworms, wireworms and flea beetles.
Hartley said producers should obtain a copy of the 2009 Guide to Crop Protection, which outlines insect, weed and disease control products.
The book was produced in December, and he said an addendum will be made in April if there are any changes.
In coming weeks, we will feature insect reports from other regions of the West.
