'Anything goes' with insect populations provincial entymologist warns

Tuesday, January 8, 2008

by MARY BAXTER

To kill off pests such as bean leaf beetles, low temperatures for a sustained period of time are needed, Baute said. Yet what will happen is anybody’s bet, she admitted, noting that a current thaw may be enough to trick the pests to emerge just in time for temperatures to plunge and kill them. Baute was highlighting some of the emerging pest trends in the province and neighbouring jurisdictions. Among these:

- There is a higher incidence of grubs appearing in hay fields and some soybean fields. Baute suggested the June beetle rather than the European chafer might be causing the problem.

- In Michigan, the Asiatic garden beetle grub injures corn seeds and seedling roots. The adults feed on leaves and other aboveground parts of corn but are considered to cause greater injury to turf grass and other host plants.

- Provincial officials are also on the alert for Western bean cutworm, which has caused significant damage in the U.S. Midwest. The larvae of the insect feed on ears of corn. So far, she has not captured any of the insects here but Baute nevertheless plans to ramp up monitoring this year. “They are pretty voracious,” she said, noting one larva can cause a 3.7-bushel a year loss.

- Yellow underwing moth is causing some concern in Michigan. Previously, the insect was never known to cause crop damage. That changed last fall. Thousands of the caterpillars were found around homes and in hay fields as well as small grain fields.
Like armyworms they move in large numbers and feed at the base of plants, said Baute. The difference is that this insect is more cold resistant so the damage occurs later in the fall.

Climate change is likely the reason behind the northern migration of many of these pests. “Our climate basically becomes the middle, Midwest (U.S.) states kind of temperature,” Baute said.

Ironically, another factor may be the success new technology has had in controlling pests such as corn rootworm. The technology may also be “killing off the beneficials that were feeding on other pests,” she said, providing an opportunity for secondary pests, such as corn-hungry millipedes to thrive.

Baute noted both Ontario and Michigan experienced a flush of aphids in early May.

“They were only in the fields that were planted on May 5 and were up by May 10,” she said. In Ontario, natural predators such as fungus and a certain kind of wasp were having an impact on infestations, providing from 10 to 25 per cent population control. BF