Grasshopper Numbers Increase

OMAHA (DTN) -- When John Anderson welcomed visitors on June 24 to the Kane Lake Ranch near Merritt, British Columbia, he talked about the spring dryness, the danger of wildfires and the grasshoppers.

To illustrate the latter, the rancher walked into the grass. With each step, large numbers of small grasshoppers flew up in every direction. "They're pretty small right now," he pointed out. They weren't a big problem -- yet -- but the question was what damage they'd do to ranchers' pastures once those grasshoppers became adults.

Now, in late July, people in parts of Canada and the United States are sharing on social media about grasshopper damage on farms and ranches; there have even been some tweets saying large swarms of grasshoppers are showing up on radar on rainless days.

DTN Ag Meteorologist John Baranick said while it's not impossible, it is actually hard to see insect swarms on radar. It usually needs to be close to the radar dome, on cloudless days, and in the morning or evening if they're swarming around.

"Usually, it's not the middle of an afternoon. But sometimes you can pick that up, insect swarms or bats, right at dawn or dusk -- Texas is a good example of that -- right at dawn they come back, and you pick that up, too," Baranick said.

HIGHER GRASSHOPPER NUMBERS

Crop progress reports have recently been increasingly mentioning grasshoppers on both sides of the north/south border. In North Dakota, crop scouts headed into the fields for the 2023 Spring Wheat and Durum Tour this week were expecting to see grasshoppers in the fields. The North Dakota Wheat Commission report noted for its report this week that "Grasshopper pressures are higher than normal in many areas." (DTN Crops Editor Jason Jenkins is participating on this year's tour. Look for daily updates and final yield estimates on www.dtnpf.com and on Twitter.)

"Crop damage this past week is mostly due to dry conditions and grasshoppers," noted the Saskatchewan Crop Report released on July 20. "Producers are encouraged to look at their economic thresholds while scouting for grasshoppers." Manitoba's July 25 Crop Report stated that producers in some areas are seeing grasshopper activity picking up, and some are spraying pastures for grasshoppers. Some are also finding grasshoppers in their cereal crops and around edges of fields.

ECONOMIC THRESHOLDS FOR GRASSHOPPERS

Economic thresholds for grasshopper densities in rangeland vary from eight to 40 grasshoppers per square yard. The thresholds are influenced by several factors, including the cost of control product, projected forage yield, and the value of forage considered for treatment, explained Extension educator Dave Boxler in the University of Nebraska-Lincoln CropWatch newsletter posted in early June.

Unfortunately, at the same time that cattle producers are attempting to save as much of their precious pastures as they can for their cattle during the hot, dry summer, they have competition.

"Grasshoppers consume up to 50% of their body weight every day in forage. A rate of just 2.7 grasshoppers per square yard equals 12,971 grasshoppers per acre. An acre with 69.7 grasshoppers per square yard equates to the consumption of forage by one cow per day," Boxler wrote.

DROUGHT YEARS INCREASED PROBLEM

This summer's grasshopper problem has actually been years in the making and was warned about last fall, when the 2023 Rangeland Grasshopper Hazard Map was released based on the 2022 adult survey.

"Pasture grasshopper species that are most damaging are found in areas with less than 30 inches of annual rainfall," wrote Boxler in June. "The western two-thirds of Nebraska fall into this rainfall category. With the occurrence of consecutive years of drought, grasshopper outbreaks are possible. The past several years, southwestern, south-central and western Nebraska have experienced below-normal precipitation. This type of weather pattern can play a large role in rangeland grasshopper outbreaks, and monitoring grasshopper numbers is important to figuring out what action may be required."

But some of those areas that expected heavy infestations, such as western Nebraska, have now received more rain this year than they have in the prior couple years.

Looking at the 2022 map of where grasshoppers were expected to be bad in summer this year, Baranick noted, "Montana and North Dakota, where this map was expecting grasshoppers, including western Nebraska, they had a bunch of rain, and those areas aren't in drought ... They came out of it the last few months; their rain had been fairly decent."

But Baranick can see where the grasshopper problem began. "Going back to two years ago, it was definitely drought in those areas -- fall of 2021 they were in D3, D4 drought, looking at that map -- Montana, North Dakota, into western Nebraska. (The grasshoppers) laid their eggs that fall, they have been there all last year and munched on all kinds of stuff." Even after drought started to come back in late August to October last year, the precipitation returned in early spring/early summer in those areas. "We had plenty for them to munch on, forages and crops."

SEVERITY BASED ON WEATHER

Samantha Daniel, with Perkins County Extension in Grand, Nebraska, wrote for UNL's July 7 CropWatch newsletter about how precipitation and temperature can affect grasshopper outbreak severity.

"Because grasshoppers tend to thrive in dry, hot conditions while outbreaks can be severely limited by cool, wet spring weather, producers in eastern Nebraska might see an increase in outbreaks this summer, while western Nebraska grasshopper populations may be reduced. It is still recommended that producers throughout the state scout their fields and select proper treatment protocols when needed," she wrote.

Daniel offered advice on how to scout for grasshoppers.

"Randomly select an area several feet away and visualize a 1-square-foot area around that spot. Walk toward this spot and count the number of grasshoppers you see in or jumping out of this area. Repeat this procedure 18 times and divide the total number of grasshoppers by two. This will give you the number of grasshoppers per square yard. Economic thresholds for grasshoppers range from eight to 40 grasshoppers per square yard, depending on a variety of factors. Keep in mind that control is easiest before grasshoppers reach the adult stage," she explained.

Boxler suggested the sample sites be 50-75 feet apart.

DROUGHT AREAS AFFECTED

There remain areas that have had below-normal precipitation for several years; current drought conditions in the U.S. and Canada have increased the grasshopper challenges.

While there are more than 600 species of grasshoppers in North America, only a few cause economic harm, said a Saskatchewan government website about grasshoppers. "The species that are considered pests are economically important because under ideal food and weather conditions, they multiply quickly and when present in large numbers they can cause severe crop damage."

UNL's Boxler said grasshopper eggs normally overwinter until the ground temperatures reach 50 to 55 degrees Fahrenheit. "Most species reach the adult stage 30 to 50 days after hatching," he wrote. "Approximately 50 species of grasshoppers are found on rangeland in Nebraska, though generally fewer than 10 species ever reach economic levels, accounting for 95% of the damage. Grasshoppers defoliate grass by direct feeding on leaf and stem tissue and by cutting off leaves or stems."

(See more about the types and life cycles of grasshoppers at https://www.saskatchewan.ca/… and https://beef.unl.edu/….)

GRASSHOPPER IMPACT

In Canada's Prairies, "Although the majority of damage has been to cereal grains, other crops can be seriously affected. In a more diversified agricultural landscape where cereals are often rotated with other crops such as canola, lentil and peas, grasshoppers continue to cause significant economic loss in Saskatchewan," stated a grasshopper overview page posted by the Saskatchewan government.

"Forage losses are seldom estimated, but it has been shown in Alberta that even a moderate infestation of 10 grasshoppers/square meter can consume 16%-60% of the available forage depending on the condition of the forage stand. The type and extent of crop damage will depend upon the type of crop, how well the crop is growing, the number of grasshoppers present, and whether or not adequate cultural and chemical controls are used," stated the government website.

HOT, DRY CONDITIONS AFFECT NUMBERS

The rising temperatures and continued dryness in the Canadian Prairies isn't helping farmers battle the grasshoppers, Baranick pointed out. "This year hasn't been very favorable for them. Right along the international border and north into Saskatchewan and southern Alberta, in the Prairies, it's been very dry for almost all summer."

As for the areas of Canada and the U.S. where higher grasshopper populations exist, temperatures will continue in the 90s and triple digits, although Montana and North Dakota will see a front come through on July 26 that will help bring temperatures down a bit afterward.

GRASSHOPPER CONTROL

In CropWatch, Daniel suggested controlling grasshoppers with insecticides and baits. "The insecticides currently registered for use on rangeland are Dimilin, Malathion and Carbaryl. Rates for these products are listed on the labels. If larger grasshoppers are targeted, the higher-labeled rates should be used. Other insecticides are labeled for control of grasshoppers in forages, grasses, alfalfa and other crops."

Boxler explained more about control: "A grasshopper integrated pest management (IPM) program called Reduced Agent and Area Treatment (RAAT) was developed by researchers at the University of Wyoming to improve grasshopper control in pastures and rangeland. This chemical control strategy utilizes the insecticide Dimilin, which interferes with the molting process of grasshoppers.

"Dimilin is applied in alternating strips, reducing application costs by 50% to 60% and reducing the amount of insecticide used by 65% to 70%, compared to conventional broadcast treatments," said Boxler. "The RAAT system provides up to 85% control, depending upon rate of growth of the forage, the size of the grasshoppers and the coverage obtained." He also encouraged people to contact their local university extension office to learn more about other grasshopper control options.

Elaine Shein can be reached at elaine.shein@dtn.com

Follow her on Twitter @elaineshein

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