2020 forecast maps
Meers says that this forecast map is based on a lot of hard work done by agriculture fieldmen across the province. In late August, they conducted a grasshopper count in their counties, municipal districts and special areas – covering several thousand fields in the process. From that information, the forecast map was built.
“So, what’s showing? That’s the question,” he says. “We have a developing issue in southern Alberta – Lethbridge County, Foremost, Warner, Willow Creek and up into Vulcan County.”
He adds that the numbers were fairly high last fall, following the dry weather that was in the area.
“We have a forecast of fairly substantial risk through much of that south central and southwestern crop production area with a little hotspot in the MD of Acadia. Fairly high numbers were showing up in north central Alberta and the Peace, but we have something else going on up there.”
He says that the population of grasshoppers in those northern areas are now almost exclusively Bruner’s Spur-throated grasshoppers, and it seems to be following an every-other-year outbreak.
“Even though our forecast shows there will probably be grasshopper issues in 2020, our experience tells us that the next time we’ll have grasshopper problems in that area will likely be 2021. We have higher grasshopper populations during the odd-numbered years.”
“The reason we haven’t changed the forecast is we just don’t have the research to back up the pattern. Research is currently underway to validate the 2 year lifecycle of Bruner’s grasshopper.”
Meers says that wheat midge risks are relatively low in the Peace although there will be individual field risks.
“In central Alberta, the risk is still reasonably low, but we have higher numbers of wheat midge in the survey. It is definitely something to watch through much of that area. Wheat midge is incredibly low in southern Alberta.”
“The wheat stem sawfly is not a forecast map per se, but it gives a very strong indication,” he explains. “Research has started on converting it to a forecast, and we will see it as a forecast map in the future.”
He says that sawfly numbers are climbing in the dry parts of southern Alberta – Vulcan, Willow Creek, Lethbridge, MD of Acadia, Foremost and 40 Mile.
2019 survey maps
Even though this is a 2019 survey map, Meers says inference can be made based on what was seen and what happened to bertha armyworm populations.
He adds that there are 3 different stories for 3 different regions in the province
“We had high populations up in the Peace, central Peace, around Falher, over into Birch Hills, south of Manning and into the MD of Peace River. There was a fairly substantial outbreak with many acres sprayed.”
“Central Alberta was rather moderate and scattered, and there was very little spraying. Southern Alberta was a little bit elevated over the previous year, and there was some limited spraying for bertha armyworm in southern Alberta as well.
“Surmising based on trends, we’re 2 years into the outbreak in the Peace,” he explains. “There will likely be a third year which may be more limited depending on weather conditions.”
“It looks like it’s backing off in central Alberta, so I think we’re through the risk in 2020. If the lack of snow and -35 C temperatures a few weeks back doesn’t kill them off, we’re looking at a building population in southern Alberta.”
He adds that pheromone monitoring through June and July of 2020 will be the most important part of the process.
“It will tell us where the risk areas are. We are already starting to look at getting the trap sites set up again through our cooperators. We had 326 sites in 2019, and we would like to maintain in that number. “Insect survey technologist Shelley Barkley is already getting sites lined up for 2020. If you are interested, contact her at email@example.com.”
“Cabbage seedpod weevil has been through a 3 year low where we are just seeing the very, very early seeded fields that get sprayed and virtually nothing else sprayed,” Meers explains.
He notes a few interesting things with this survey. “It looks like we have a slight build in the population in 2019, so we’ll see how that plays out in 2020, but I expect a bigger population in 2020 based on the trend.”
“The severity in the Calgary, Trans-Canada Highway area and north is down from what it has been in previous years. There are very few cabbage seedpod weevils north of Highway 1.”
“But, we are finding cabbage seedpod weevil up to Edmonton and to the northeast of Edmonton at very, very low numbers. It is questionable whether that population has established, but right now, it’s not an issue.”
He adds that cabbage seedpod weevil does not like extended cold winters, and that may be what’s holding it out of central Alberta more than in the southern part of the province.
“We’re finding it in the Peace, but it is not an issue,” he adds. “We have a fairly high population in Edmonton and the northwest area of Central Alberta. Producers should consider seed treating in that area – Westlock, Barrhead, Lac Ste. Anne, down through Parkland County and Leduc.”
“The rest of Central Alberta pea leaf weevil is pretty low. It’s a traditional population in southern Alberta – lower than normal but producers should still be seed treating.”
Winter and insects
“First and foremost,” says Meers, “snow is a great insulator. If you get a foot of snow and it’s -40 C, at soil surface it’s still only around 0 to -5 C.”
He says that the real damage to overwintering insects takes place when there is extended cold, -35 to -40 C and no snow cover.
“That combination is deadly to some insects, and bertha armyworm is one of those. Some insects that are not really hardy, like diamondback moth and some of the aphids, are typically killed off by even moderately cold weather.”
“Some insects like sawfly and grasshoppers are very hardy, and it’s not going to matter what the winter does. The weevils – cabbage seedpod and pea leaf – seem to be sensitive to extended winters. So if January’s cold continues into March, it will affect the population.”
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