Know crop values, pest numbers before you spray

Spraying to control insect pests costs money. Knowing when it makes economic sense to do so depends on the severity of the problem – and the worth of the crop, experts say.

According to Brian Voth, president of IntelliFARM Inc., – a grain marketing company in Western Canada - spending more to protect higher-value crops, like canola, makes more sense to his clients. This is particularly true given the accordingly higher investment required to produce each acre.

The cost-to-profit ratio for lower-value commodities might not pencil-out.

“There’s a lot of incentive to do what’s necessary to ensure that crop yields everything it can,” Voth says. “If [oats] are at $3 a bushel, you can afford some loss there before it would make economic sense to go and spray.”

James Tansey, provincial insect and vertebrate pest management specialist with the Saskatchewan Ministry of Agriculture, also says pest tolerance thresholds generally decrease with a higher commodity price and reduced control cost.

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Know insect numbers

Making a recommendation to spray requires a lot of counting, says Emma Epp, a certified crop advisor and crop sales specialist with AGRIS Co-operative in southwestern Ontario.

“We would be trapping insects, counting insect populations and determining what the thresholds are at the current crop stage,” Epp says. “The habit would be creating good integrated pest management practices.”

Keeping the farm's crop advisor up-to-speed and listening to them when they say a pest has reached its peak threshold, she says, is important.

“We will only recommend spraying if it is essential to spray,” Epp says.

Know your budget

Overall, Voth says knowing whether pest control makes objective sense requires a real, working budget. However, not every farm has one.

“Once they have that cost of production, go and plug in those scenarios... It's really easy to run a what-if scenario to see how it changes the cost and input ratio,” says Voth. “If it’s questionable, I would ask what the point is.”

Tansey reiterates the cost of any control effort should be carefully calculated so as not to exceed crop returns. This involves accounting for all the control costs – including fuel, labour, wear on machinery and even the effects on beneficial insects. 

“Knowledge of the biology and identity of the pests is essential and will increase the predictability and efficacy of control efforts,” Tansey says.

“Don’t just spray if there are insects, in the broad sense, in a field. If they are not pests, or pests but not at economic levels, you are wasting money.”

Bottom line

Experts advise careful consideration of the costs of protecting crops from harmful insects before making the decision to spray. Issues like crop value, the farm's integrated pest management practices and the cost of spraying should also be considered.

Article by: Matt McIntosh