Be on the lookout for beetles and midges PDF Print
Local Content - Local Agriculture
Written by Greg Price   
Thursday, 22 March 2012 14:20

While there has not been substantial crop damage that has occurred from a couple of prominent pests found in southern Alberta, vigilance is still needed when combating the cereal leaf beetle and the wheat midge.
“Irrigated wheat is nearly-perfect conditions for wheat midge. We have had problems with wheat midge in the County of Newell, who have recorded significant losses,” said Scott Meers, an insect management specialist with Alberta Agriculture and Rural Development, to the crowd at the Heritage Inn during a presentation on identifying area crop pests. “It’s totally possible to happen in your community.”
The last few years, surveying has been done for the wheat midge in the Municipal District of Taber. A wheat midge is a small fly that looks like a small orange mosquito that emerges from the larva stage in the spring after irrigation, usually in late June or early July.
“If your wheat is just beginning to head at that time, which it probably is, then your wheat is at risk of being infected.”
Wheat remains susceptible to wheat midge from when the head is visible up to flowering (anthesis) where eggs are laid on the shaft.
“So from heading to anthesis, that is usually for your entire crop that is around two weeks. You can tighten that up with heavier seeding rates,” said Meers of the wheat crop vulnerability stage to wheat midge. “The small time frame is the kicker in all this. I think in southern Alberta we can get around this insect by making sure we get our wheat in as early as we can. If it gets to anthesis stage, you are out of the danger zone.”
Field scouting for wheat midge should be in as favourable conditions as possible, which include winds less than 10 kilometres an hour and temperatures under 15-degrees Celsius in the evening.
If you are suspicious of wheat midge, go out when the sun starts to set and sweep really hard on your wheat crop and if you find little orange specs, you likely have wheat midge. The threshold for scouting is one adult for every four or five wheat heads.
“They are not day active, they are active at that time of night when you start to feel the humidity rise, which is when they come out,” said Meers.
The good news in Alberta in combating wheat midge is a type of wasp that serves as a parasitoid, laying an egg in the egg of the wheat midge and consuming the midge from the inside.
For that purpose, farmers should not apply insecticide after flowering because it will not affect the wheat midge at that point of crop maturation, but will get rid of the beneficials of the parasitoid in the wasp. Another tip is not to plant continuous wheat rotations.
“We are finding wheat midge in your county, it’s not bad yet, but it certainly has the potential, especially if you like to grow wheat on wheat,” said Meers.
The cereal leaf beetle was discovered in Lethbridge and Taber counties in 2005 and as far back as 1966 in Canada in southern Ontario and is now found in all Canadian provinces that grow wheat.
“There are far more (cereal leaf beetles) in winter wheat than in spring wheat. Generally it looks to be the biggest pest in winter wheat,” said Meers.
The Lethbridge research station is setting up ideal situations for the cereal wheat beetle so as to encourage the parasitoid tetrastichus julis to combat the beetle.
“In the Crescent Valley, this insect has completely suppressed the population of cereal leaf beetles. It is a very effective parasitoid,” said Meers, adding Taber showed a parasitism rate of 48 per cent for 2008/2009. “It is showing it is accomplishing something. This insect without any parasitism can completely wipe out a good crop.”
The cereal leaf beetle is about 3/16th of an inch long with a metallic blueish-back wing, but it is the larvae that causes the big damage which looks like a bird dropping on a leaf.
“This one is here and we’ve found some fields that are near threshold and we’ve seen some fields that have been sprayed and they probably didn’t need to be,” said Meers. “This is one area that if you are suspicious of it, get them to look at it and get a careful assessment and if it needs to be sprayed then spray it.”

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