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Crop Diagnostic Lab Report

Week of July 12 - July 16, 2010

Cereals Three samples of wheat showing a physiological purpling, chlorosis and necrosis of leaves were received this week (South Parkland). Previously samples received with similar symptoms were all of the cultivar Kane and this time two were cultivar Glenn. Cultivars with the cultivar Amidon in their parentage seem to be the ones that show this symptom pattern and both Kane and Glenn have Amidon in their parentage. The symptoms are related to a reaction of the plants to stress. Three samples of wheat with a leaf burn caused by environment were received (Red River, Pembina). Leaf tip burn is often related to strong wind. One sample of winter wheat with a physiological leaf spot was received (Eastman). One sample of wheat with Septoria leaf spot was received (Red River).

One sample of oats with crown rust and Septoria leaf spot was received (Red River).

Oil Seeds One sample of canola was diagnosed with leaf injury from downy mildew (Southwest).  

Canola – downy mildew can appear as necrotic spotting on upper leaf surface surface and underside of leaf may have spotting that looks somewhat water soaked in early stages.

Three samples of flax with chemical injury symptoms were received (Southwest). One sample of flax was diagnosed with pasmo (Southwest).

Flax – chlorosis of the growing points can be caused by glyphosate or group 2 herbicide exposure.

One sample of sunflower was received with symptoms suspected of being related to lightening injury was received (Southwest). Lightening strikes tend to cause rapid kill of broadleaved plants with affected patch roughly circular and center of the patch dying out completely with plants around the outside of the patch showing various symptoms of wilting, dying off or poor growth.

Beans/Peas/Lentils One sample of soybean was found to be affected by Septoria leaf spot (Red River). One sample of soybean was diagnosed with anthracnose (Red River). One sample of soybean was diagnosed with group 2 herbicide injury (Red River). One sample of soybean was diagnosed with root rot caused by Pythium, Phytophthora and Fusarium (Red River).

Soybean – reddening of the veins on the underside of the leaves can be caused by group 2 herbicide.

One sample of peas was found to be affected by Fusarium root rot (Southwest). One sample of peas was diagnosed with both Ascochyta and anthracnose (Southwest).

One sample of cranberry beans was diagnosed with Sclerotinia stem rot (Red River).

Forage One sample of alfalfa with heavy development of common leaf spot was received (South Parkland).

Alfalfa – common leaf spot.

Fruit One sample of sour cherry had anthracnose leaf spot (Red River).

Vegetables/Potatoes/Herbs One sample of greenhouse tomato was diagnosed with leaf injury caused by thrips (Red River). One sample of tomato with chemical injury was received (Southwest). One sample of onion showing slight wilting of leaves was found to be affected by the disease known as Fusarium basal plate rot (Pembina).

Two samples of potato were diagnosed with Verticillium wilt (Red River). Four samples of potato with leaf injury from environmental conditions were received (Red River, Southwest, Central Plains). Four samples of potato with late blight were received (Central Plains).

Trees and Shrubs One sample of spruce showing a pattern of needle burn and wilted new growth suspected of being a toxicity reaction was received (Red River). One sample of spruce with a spruce bud scale infestation was received (Central Plains). Heavy development of sooty mould frequently occurs with infestations of this insect.


Spruce – heavy development of a black mould known as sooty mould is a common occurrence with a heavy infestation of spruce bud scale. The sooty mould itself is unsightly but not harmful to the tree.

One sample of ornamental apple affected by both fireblight and the disease known as apple scab was received (Valleys North). One sample of basswood with chemical injury was received (Central Plains). One sample of poplar with Phyllosticta leaf spot was received (Central Plains). One sample of amur maple affected by severe iron chlorosis was received (South Interlake). One sample of ash showing symptoms of decline was received. Plate tests on the sample pieces did not reveal any disease organism although sometimes small twig and branch samples from such trees miss the site of infections which can’t be detected beyond the infection point even though symptoms can be evident far beyond the place where the vascular tissues have been compromised (Central Plains). One sample of oak showing brown leaf spotting caused by the disease known as anthracnose was received (Red River). In that case the owner thought the tree had been damaged by chemical because of the extensive leaf spotting present. Weather conditions this season have been ideal for some tree leaf diseases like oak anthracnose.

Weeds Weed this week included cow-parsnip (Red River), common mallow (Southwest), motherwort (North Interlake), wild bergamot (Southwest) and a Polygonum sp. (Southwest).

Insects A spotted cucumber beetle was submitted for identification this week and was found in canola. It is not a pest of canola. Area where this was found was not reported by the submitter.

The Diagnostic Lab Report is prepared by Mardi Desjardins, Crop Diagnostic Centre, Manitoba Agriculture, Food and Rural Initiatives, 201-545 University Crescent, Winnipeg, Manitoba R3T 5S6. Phone: 204-945-7707 Fax: 204-945-4327.

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