Crop Diagnostic Lab Report

 

Week of June 22 - 26, 2009

This week we processed two samples of wheat (Red River) and one sample of barley (North Parkland) with symptoms of both stress and root rot. One sample of wheat and one sample of barley were diagnosed with common root rot (Central Plains, South Interlake). When plants are under stress from unfavourable field or environmental conditions, they tend to be more vulnerable to attack from root disease fungi. Three samples of barley showed development of net blotch (Red River, South Interlake, Southwest). There was one sample of winter wheat with group 1 chemical injury and root rot (South Parkland). One barley sample (Pembina) and one wheat sample (South Parkland) showed symptoms of stress likely related to deep seeding. One sample of wheat had yellowing of older leaves believed to be related to environmental stress (South Parkland). One sample of wheat had white spotting and flecking that appears to be related to some kind of insect feeding injury (Red River). One sample of winter wheat had injury to leaves from a contact herbicide (Red River). Contact chemical injury may sometimes be mistaken for a fungus leaf spot.

Wheat – necrotic (brown) and chlorotic (yellow) spotting of winter wheat flag leaves caused by exposure to a contact herbicide.

Wheat – white flecking or spotting of leaves that is consistent with insect feeding injury. Note the leaf to the right of the picture with spots aligned in rows.

One sample of sunflower with rust was diagnosed (Red River). One sample of sunflower with group 4 chemical injury was received (Pembina). One sample of flax with heat canker injury was received (Red River). One sample of flax with chemical injury related to group 2 herbicide or glyphosate was received (Red River). Symptoms of these two chemical groups can cause similar symptoms on flax. Four samples of canola with severe stunting and proliferation of growth from the leaf axils were diagnosed with injury from group 2 herbicide (Southwest).

Flax – note the pinched area at the soil line caused by heat canker on the 3 plants to the left.

One sample of peas with leaf miner injury on leaves and yellowing related to stress was received (South Parkland). Two samples of peas with Fusarium root rot were received (Red River, Southwest).

One sample of alfalfa with a combination of spring black stem and lepto leaf spot was diagnosed (Red River).

For spruce, one sample was received with development of Stigmina lautii but was suspected of also having a vascular problem (South Interlake). Tree samples (green ash, willow, poplar) with chemical injury symptoms were received (Southwest). One sample of green ash with very severe leaf injury from ash plant bug was received (Red River). Even when the injury is severe, a single season of leaf loss from insects does not usually have any significant impact on an otherwise healthy tree. One sample of basswood with development of mite galls on leaves was received (Red River) and a few other inquiries have also been received about galls on the basswood leaves. The galls are caused by a mite and in some seasons can be very numerous but don’t do any injury to the tree.

Basswood – these galls are caused by a mite.

One sample of cotoneaster with abnormally slow growth and small tufts of narrowed leaves was received (Red River) and diagnosed with glyphosate translocation injury. If exposure to glyphosate occurs on trees or shrubs in late summer or fall, symptoms may be observed the following season with symptoms of slow growth, small cupped or narrowed leaves and growth tending to have an appearance of tufts of growth. Symptoms can vary somewhat depending on the particular type of tree or shrub and how much chemical was taken in by the plant.

cotoneaster – abnormally narrowed leaves and tufted growth caused by an exposure of glyphosate last season.

Weed identifications for this week included downy brome (Southwest, Pembina), hoary puccoon (North Parkland), three flowered avens (North Parkland), arrow leaved colt’s foot (Southwest), tufted hair grass (Red River), narrow leaved hawk’s beard (Red River), marsh yellow cress (Red River), oak leaved goosefoot (Red River).

 

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.