PORTAGE LA PRAIRIE, Man. – Manitoba sunflower growers were warned this month that there are three pest insects likely to pose the greatest menace to their crops in 2004.
Of most concern are cutworms and lygus bugs, said provincial entomologist John Gavloski, but grasshoppers could also pose a threat.
“At this point, I would probably say cutworms and lygus bugs are our two biggest concerns,” he said during the National Sunflower Association of Canada annual general meeting on Dec. 5.
The cutworm population goes in cycles, rising and falling over a three- to five-year period.
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Based on that cycle, there’s a likelihood they will be back in high numbers in 2004, Gavloski said.
The concentration of cutworms tends to be highest in fields where there were weedy patches or late flowering crops the previous year, he said.
Entire fields do not have to be sprayed if producers scout carefully and identify the areas where the insect appears to be concentrated.
Although lygus bugs are also a worry, Gavloski said the outlook could change between now and the growing season because they are susceptible to winterkill.
The lygus bug is mainly a concern to growers of confectionary sunflowers. The bug burrows through the hull and damages the seed, making it unappealing to consumers.
Research to determine the economic threshold for spraying lygus bugs is ongoing. However, Gavloski said there are indications that the threshold may be as low as one bug per plant in confection crops.
Grasshoppers are poised to be a big problem in much of Manitoba in 2004. They were abundant this year and their egg-laying activities set the stage for a potential scourge in the coming growing season.
“Our grasshopper forecast looks horrible for next year,” Gavloski said. “Lots of areas of the province are red.”
Gavloski touched on some other insects of interest to sunflower growers.
The sunflower beetle population took a big fall this year, he said. He expected that will translate into a lower prevalence of the insect in 2004, but he advised growers to scout as a precaution.
The sunflower midge hit fields hard in the Red River Valley three or four years ago, but has been less of a concern since then. The midge likes fields with moist soil, which means heavy infestations are less likely outside the valley.
“Overall, it was pretty much a non-issue last year,” Gavloski said.
There could be a resurgence, particularly in the Red River Valley, if 2004 brings a moist spring with standing water in fields.
As for the thistle caterpillar, Gavloski said it probably won’t be a problem. The caterpillar overwinters in the southern United States and relies on wind to carry it into the northern tier states and Canada. The kind of wind needed to bring it to Manitoba usually occurs only once every 10 to 15 years.
