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The Prairie Giants Crop Report

Field observations at your fingertips

July 17, 2020

Taylor Kurtenbach

Welcome to the Prairie Giants Crop Report! We’ll be breaking down our observations from the field into a concise, semi-regular report.

Barley Thrips
Last week, we began receiving reports from multiple farmers of bent over heads in their wheat fields. Who is the culprit? Barley thrips (Limothrips denticornis)! Although the name may be misleading, the adults can be found in other hosts including oats, winter cereals and spring/durum wheat.

Adults are small (1.1 – 1.8 mm), narrow and dark brown/black in colour. Larvae are even smaller (0.25 – 1.8 mm), narrow and white/pale green in colour. Both the adult and larval stages feed on plant tissue by puncturing the cells and sucking out the contents, resulting in distorted and discoloured tissues. Under high pressure, heads may be bleached, and gooseneck shaped. Drought conditions may exacerbate thrip pressure due to increased population levels of this pest and stressed plants.

Unfortunately, the damage is already done at heading, and no control measures can be taken at this time. Barley thrips can be scouted when the flag leaf is first visible until the head is fully emerged from the boot. Adults can be found by rolling away the flag leaf from the stem; if 7-8 thrips are found per stem prior to head emergence, a chemical application may be warranted.
Barley Thrip Damage
Barley Thrip Damage
Barley Thrip Damage
Cereal Leaf Beetle Damage

Cereal Leaf Beetles 
Cereal leaf beetles, as their name suggests, are found in several cereal crops including oats, barley and wheat. Adults overwinter, emerging in the spring to lay 50 – 275 eggs on the upper leaf surface. Larvae, once hatched, proceed to feed on the leaf for 2 – 3 weeks until they pupate.

Larval feeding results in a “window pane” effect, as pictured. Although rare, yield can be affected if the flag leaf is stripped. Larvae are 4 – 5 mm long, with a round body and covered in faecal matter. Adults also feed on the leaves, but often do not cause economic injury.
Did you know there is a parasitoid, Tetrastichus julis, that helps to control cereal leaf beetles? Thank goodness for good insects!!

Wheat Stem Maggots
Have you ever seen white heads in your still green wheat crop? This is due to wheat stem maggots! Eggs are laid on leaves near the stem, hatching into larvae which feed inside the stem killing it and the head above.  

Little of the crop tends to be affected, 1 – 5 %, so no measures need to be taken!

Check out this great resource for more information: http://publications.gc.ca/collections/collection_2018/aac-aafc/A59-23-2018-eng.pdf

Wheat Stem Maggot Damage
Wheat Stem Maggot Damage

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