A mix of pests and diseases on the roster for #crop2020

Wheat midge, wheat stem sawfly, net blotch and other things to look out for

A stem infected by root rot shows signs of shredding, shattering and the development of a sclerotial body. The central cavity (pith tissue) has been destroyed, which is characteristic of stem rot.
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There are several diseases and pests farmers might want to keep an eye out for this growing season.

“It’s kind of a hodgepodge this year,” said Jeremy Boychyn, agronomy research extension specialist with Alberta Barley and Alberta Wheat.

The southern part of the province has had consistent issues with grasshoppers because it has been so dry the past few years. But in the Peace as well as northwestern and north-central parts of the province, hoppers are on a biannual cycle — last year, there were high numbers in the north but they were low in 2018.

“Potentially it’s not high risk (this year),” said Boychyn. “That said, it’s still worth going out and taking a look and seeing if there is any progress there. It shouldn’t be high risk in the north, but it’s important to keep an eye out.

“Producers want to be scouting early, and controlling populations of grasshoppers when they are younger, rather than when they are older.”

Farmers should also sign up for Prairie Pest Monitoring Network updates at prairiepestmonitoring.blogspot.com, he said. The updates include weather reports, which can indicate what pests may soon be an issue.

Wheat stem sawfly was a problem last year around Vulcan, Willow Creek and Forty Mile, which means there could potentially be problems again this year. These pests damage plants by depositing their eggs in the stalks. The emerging larva chew their way through the stalks, cutting them and causing lodging.

“They had seen about 10 to 15 per cent cutting in their fields last year,” said Boychyn. “This year, producers would want to use a solid stem variety in their cereals.”

The Lillian variety has been moved to the Hard Red Spring class, leaving Landmark, Adamant and Hughes registered as Canadian Western Red Spring semi-solids.

“Producers who saw cutting last year are going to want to go out late June, and early July and start sweeping for those,” he said. “There’s not much a producer can do rather than be aware that they have the potential for cutting.”

Hollow stem rot-infected stem on the left, healthy stem with intact pith tissues on the right. photo: Kelly Turkington

Fields are at risk if producers catch two female flies in every 10 sweeps. (Wheat stem sawflies look like miniature wasps, and females are distinguishable because they have an ovipositor — used for inserting eggs into stalks — on their back ends.)

“There is no way to spray for them. You have to be aware that you are at risk if you sweep and see high amounts,” said Boychyn.

The only solution is to try to harvest before cutting happens.

Wheat midge has been an issue in the central area east of Edmonton. Producers in this area should be using midge-tolerant wheat and scout their fields during head emergence.

“That’s when it is most at risk. Look for one wheat midge for five heads, as a threshold for spraying on that,” he said.

Alberta Agriculture and Forestry has pest forecast maps at alberta.ca.

Wireworms are a potential problem in the south, and producers should look for thinning patches in their cereal crops. Wireworms can be visible if the producer digs up the crop, as there will be bore holes through the seed or underground part of the plant. Wireworms are different sizes, depending on the life cycle, and are multi-sectional worms that are a pale-beige colour.

“If you see them this year, they are very likely to be there next year,” said Boychyn.

Syngenta has come out with a new control product for wireworms, and BASF will have a new control product available next year, he said.


Periods of steady rain are also a signal to up scouting — for weeds early in the season and diseases such as leaf spot in cereals later on — said Kelly Turkington, a research scientist with Agriculture and Agri-Food Canada.

“It will be important for producers to scout their fields on a regular basis,” said Turkington.

Diseases are highly dependent on in-season weather conditions, so it is hard to make predictions about what will happen, he said.

Some plant pathogens are polycyclic pathogens.

“There may be a small amount of infected crop residue in your field, but if you have a variety that is more on the susceptible side, these pathogens will produce spores released from the residue and they will infect the crop earlier in the season,” he said.

Some diseases can cycle in less than seven days and some take 10 to 14 days.

“Some of the diseases build up from seedling stage to weed management stage, stem elongation and flag leaf emergence,” said Turkington. “You can see it developing early in the season and that gives you a forecast of what’s coming down the pipeline.”

Producers should also review the scouting they did last year, as well as what happened at harvest, to estimate the disease risk potential for this year.

For example, there may be some more inoculum on crop residues this year due to the wet conditions last year.

“If you’re not planting directly on the field, that’s a good thing. If you’re planting adjacent to a field, you might have more issues this year,” he said.

Fusarium head blight and fusarium granarium can produce spores that move from field to field.

There was a fair amount of sclerotinia in canola around Edmonton and Lloydminster last year, so producers in those areas should look out for the disease.

Turkington also recommends signing up for updates from the Prairie Crop Disease Monitoring Network.

Farmers can determine what diseases might be a threat by paying attention to the past couple of years of disease history, the crops and varieties they plant, and the disease rating.

In cereals, the main diseases are likely to be scald, net blotch and spot blotch in barley and septorias and tan spots in wheat. Blackleg in canola might also be a problem.

“That’s information you can use within the current season,” said Turkington. “You can use that information and help tailor it to your spraying, help make choices and help you plan your current applications.”

About the author


Alexis Kienlen

Alexis Kienlen lives in Edmonton and has been writing for Alberta Farmer since 2008. Originally from Saskatoon, Alexis is also the author of two collections of poetry, a biography, and a novel called "Mad Cow."



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