Latest forecast map shows several hotspots to watch, but predictions depend on weather and could change with rain or cool conditions
When the lilacs begin to bloom, check the fields for grasshoppers.
It’s a matter of timing, not of direct relationship.
The grasshoppers that fly early in spring, before the lilacs reveal their blossom beauty, are not the ones farmers need to worry about, says Alberta Agriculture livestock and forage specialist Grant Lastiwka.
But the hoppers that appear at about the same time as lilac bloom bear watching to see if they develop in sufficient numbers to warrant action.
The 2016 Alberta grasshopper forecast map, prepared by the insect pest monitoring network, indicates several likely hot spots for grasshoppers this year.
A large area north and south of Edmonton, particularly around Westlock, could see high numbers and so could an area north of Grande Prairie.
Counts done last year also indicate potential for severe pressure from grasshoppers west and northwest of Lethbridge and west and south of Medicine Hat.
However, those predictions will depend largely on weather, and so far the generally hot and dry conditions are just what grasshoppers like. Heavy rain and cool conditions this month could markedly reduce numbers.
Lastiwka said ranchers can limit grasshopper development on pastures by not letting cattle graze too soon and by employing twice-over rotational grazing.
“Wait for grazing readiness, and after the three, three and a half leaf stage, remove a portion … then let the green solar panel come.”
Research from North Dakota shows season-long grazing allows cattle to frequent certain favoured spots, creating areas of low vegetation and higher temperatures ideal for grasshopper development.
“It translates into an ability to consume more per day, to get bigger per day and to get to the point in time where they can fly and cover distances, causing more damage thereafter,” Lastiwka said.
In hot, dry weather, plants grow slowly and there is more bare soil available, which favours grasshoppers.
“Once they get to the third instar (growth stage), then they can eat more and as they can eat more, they create their own little habitat. If they bare things off, they allow for the warmth to occur earlier in the morning and the warmth to be higher during the day. That all ends up creating a more successful grasshopper growth cycle.”
Lastiwka referred to Montana and North Dakota research indicating grasshopper numbers were three times higher on pastures with season long grazing compared to those with a twice-over rotation.
Lastiwka and insect management specialist Scott Meers collaborated on an alert to farmers and ranchers to ensure they keep watch on grasshopper populations and take preventive measures where possible.
A dry fall in 2015 forced some ranchers to graze pasture more heavily than desired, Lastiwka said.
Putting cattle out too early, while grass is growing slowly amid dry conditions, could encourage more grasshopper development. He suggested waiting until plants are in at least the three-leaf stage before turning out the cattle. Then graze for about 30 percent removal and move the cattle elsewhere.
Lastiwka has cattle of his own and he is still providing feed rather than grazing them.
“I had a lot of grasshoppers last year and I didn’t see them do any damage, but there was a lot.”
That direct experience led him to encourage others to make an action plan now to limit grasshoppers rather than have to spray for them later in the season.
The insect forecast map is a useful guide but management is key, he added.
“We know that good grazing management can be a mitigating tool.”