TABER, Alta. – Mark Goettel walks methodically down the rows of
potatoes, plucking shiny, pink beetles from the leaves and dropping
them into a plastic bottle.
The Agriculture Canada insect pathologist is fascinated by the life
cycle of the Colorado potato beetle.
Getting close to the voracious insects helps him learn how they live,
reproduce and die. Close scrutiny will also show him how to kill them
fast and efficiently.
“This year is worse than the last several years because it was a very
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mild winter,” he said.
“The warmer it is the faster the insects will grow.”
North American potato growers have fought the beetle since the
mid-1800s using a variety of insecticides. Today resistance is a
growing problem in Manitoba and Eastern Canada.
“None of the chemicals worked and the populations of the beetles really
went up very dramatically within a couple years,” he said.
So far resistance has not been found in Alberta’s 54,000 acres of
commercial production.
Many southern Alberta producers rely on Thimet, which is laid in the
furrows during seeding. It keeps most insects away, but some foliar
insecticides may be needed later in the season for further control.
Alberta has traditionally had only minor insect problems, but the
chance of beetles becoming a serious pest increases yearly as potato
acres expand and rotations are shortened.
The adults burrow into the ground and can survive because frigid
temperatures do not extend deep into the soil.
Hot weather stimulates them.
“They are originally from South America and Mexico so they do well in
the heat,” he said.
They crawl well and can fly once temperatures reach 27 C. Some drift
great distances in the wind so they can appear in fields that were
previously free of insects.
Control methods can be creative.
Farmers in Eastern Canada have lined trenches with plastic around their
fields. The insects cannot crawl up the plastic and perish in the
ditches.
Genetically modified potatoes with built-in beetle resistance would
have been useful had public pressure not forced major food processors
to reject them.
“The public is just not ready to accept them,” Goettel said.
“Until that happens, they won’t be on the market.”
GM potatoes could delay the development of an insect resistance
problem, but growers need to plant at least 20 percent of their acres
to non-GM potatoes to prevent resistance.
” If you had a situation where you had a beetle resistant to the GMO,
chances are it would then breed with one of those feeding on the
non-GMO plant.
“You would then dilute the resistance gene. When you have a population
that always has the same genes, it is very important that they
interbreed.”
Another problem is that commonly used chemicals are powerful and kill
good insects such as ladybugs and stink bugs.
Ladybugs eat potato beetle eggs, while stink bugs attack the larvae
that feed on the potato foliage.
Researchers at Agriculture Canada’s research centre in Lethbridge,
Alta., are studying a fungus called beauveria bassiana that has been
registered in the United States and Europe as a foliar application.
It produces a spore that attaches itself to the insect and eventually
kills it.
This process naturally occurs in the soil. The potato beetle has two
stages of life in the soil when the fungus could attack it.
“We’re looking to see how much of the fungus is naturally in southern
Alberta and is there anything we can do it increase the mortality,”
Goettel said.
