LETHBRIDGE – An increase in temperature and changes to local precipitation patterns caused by climate change could allow three minor insect pests to expand their range and severity.
Owen Olfert, a research scientist with Agriculture Canada in Saskatoon, said climate is the dominant factor determining the distribution and abundance of most insects.
He said moisture will be the wild card in territory expansion for the cereal leaf beetle, cabbage seedpod weevil and pollen beetle.
With a 3 C increase in temperature and no change in precipitation patterns, all three insects would significantly expand their territory.
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A drop of 40 percent in precipitation with the temperature increase would result in a greater increase in insect range.
However, if the temperature increase came with a 40 percent increase in precipitation, then the predicted range for these bugs would decrease.
Olfert said the pollen beetle could become an established pest at lower temperatures than the other two insects. He said a temperature increase of 3 C could allow the beetle to establish at Fort Smith, N.W.T., compared to a required 4 C increase for cabbage seedpod weevil and 5 C for cereal leaf beetle.
Under current climatic conditions, the range of the cereal leaf beetle is limited to Canada’s southern cereal-growing regions. With a 3 C temperature increase, the predicted range moves 430 kilometres north to the 56th parallel from the 52nd. Moose Jaw is at about 50 degrees latitude and Prince Albert is about 53.
In Manitoba, a 5 C temperature increase would move the insect’s range 600 km north to the 56th parallel from the 50th.
Flin Flon is around 54 degrees latitude and Churchill is around 58.
With the cabbage seedpod weevil, studies suggest a 3 C temperature increase would allow the insect to populate the northern Prairies. The weevil could extend north 400 km in Manitoba, 500 km in Saskatchewan and 600 km in Alberta.
With the pollen beetle, studies suggest a 3 C increase in temperature would extend the northern limits about 350 km in Saskatchewan and Manitoba.
“Bioclimatic modeling software like Climex can produce models that describe the potential distribution and relative abundance of a species based on climate. With warming conditions and changes in precipitation patterns, there’s a good chance this will influence insect populations, improving their ability to spread and colonize new areas,” Olfert said.
“Historically, surface temperature has increased almost 1 C over the past 100 years. The largest temperature increase has occurred in the high latitudes in the northern hemisphere, which has implications for (western Canadian farmers), more so than some of the tropical countries.
“There has also been an increase in continental drying and the risk of drought. That has contributed to an increase in the growing season. For this part of the country, the estimate is that in the last 40 years, the growing season has increased one to four days. That’s important for insects and crops.”
Olfert said low greenhouse gas emission predictions suggest a temperature increase of 1 C to 3 C over the next 20 to 30 years. High emission estimates predict it could be 3 C to 7 C higher on the Prairies.
Unlike temperature, Olfert said climatologists are not as certain about changes in precipitation, but most agree it will be highly variable. They also believe the effects of climate change will be more noticeable in northern latitudes than near the equator.
“What does this mean for insect pests? Climate and weather is a big driver of insect pest population distribution, as well as population increase and decrease,” Olfert said.
“Longer growing seasons might alter the timing of emergence of some of the pests that overwinter. Warmer temperatures usually mean an increase in growth and developmental rates, which shortens up the generation time. The warmer it is, insects eat faster and eat more. Less cold stress will reduce overwintering mortality rates.
“It may reduce biodiversity. The pests doing really well under warmer conditions may experience a surge and dominate insect populations. And the extreme variability of weather may reduce the efficacy of pesticides registered under typical environmental conditions and may have a negative impact on some of the natural enemies.”
Olfert said a number of western Canadian researchers think it is important to see how these warming conditions and changing precipitation patterns might affect insect populations.
“The approach we use is a bioclimatic simulation model. These models are used to predict the distribution and abundance of insect pests based on climate data, and species specific biological information. The more you know about the insect of interest – how it reacts to heat, cold, drought and rain – the better off you are in terms of applying climate data to it,” he said.
“Very important in these climate models are stress factors: cold, heat, drought and wet stress. All are combined in a modeling approach to come up with a suitability or ecoclimatic index, which describes the suitability of specific locations based on climate, for a given species.”
Researchers have developed bioclimatic models for the cabbage seedpod weevil, pollen beetle and cereal leaf beetle, published the models and then looked at applying the incremental scenarios based on what the climatologists were telling them.
“Instead of using the weather data for the last 30 years, we incorporated the weather data the climatologists said might happen over the next few years. We looked at temperature increases a degree at a time, up to seven degrees warmer, and precipitation, plus and minus, up to 60 percent.”
Olfert said the cabbage seedpod weevil was first found on the British Columbia mainland in the 1930s. It’s common in the U.S. Northwest, and as far south as Georgia. Now it occurs in canola in B.C., Alberta and Saskatchewan.
“The current range could expand greatly if we have consistently warmer summers,” Olfert said.
“Using GIS (geographic information systems), the estimate we have is they could occur 450 to 500 km further north than it currently is.”
The pollen beetle model was produced based on records in the Maritimes, Quebec and Ontario. The insect is a potential pest of canola.
“It might not be in outbreak proportions, but there is some potential for establishment of the pollen beetle in the Prairies,” he said.
“We would expect the range to increase significantly in the northern regions across the Prairies.”
The cereal leaf beetle was first reported in Michigan in 1962 and is now found in much of North America.
“Based on our model runs, we found that a temperature increase of three degrees would result in these three species emerging about three weeks earlier in the year. Because the growing season is longer, they’d have a longer period to feed and cause crop damage,” Olfert said.
“Longer growing seasons translate into longer periods of time that they’re available for locating the host crop, feeding, reproducing and migrating to suitable overwintering sites.”
With all three insects, the researchers predicted a major shift north under climate change.
They also say it’s possible crops can be grown in these areas if weather systems allow a climate suitable for crop production
“A study of arable soils in North America north of 55 degrees and west of 110 predicted that if CO2 emissions doubled – equivalent to a 3.8 C increase – there could be an increase in arable land almost equal to the current amount of arable land in the Canadian Prairies,” Olfert said.
“The results suggest many areas are vulnerable to the range and abundance of insect pests. The risks associated with these species will become more severe in terms of their abundance and their ability. The reason we’re doing this is to investigate future adaptation strategies in advance of the shift of these pest species.”
