Crop Diagnostic Lab Report

 

Week of June 15 - 19, 2009

We have had a slow start to the season because of environmental conditions. Samples are finally starting to come into the lab on a regular basis.

This week brought several samples of wheat with tanspot (Southwest, Red River). One sample of wheat with complaints of yellowing was received and was found to be affected by a combination of stress factors and root rot disease (Red River). Root rot can be ruled out as a primary factor when symptoms are evident on a number of plants but careful examination reveals evidence of root necrosis on only a few. One sample of wheat was received (South Parkland) showing symptoms consistent with group 1 herbicide injury, likely related to application of the chemical close to an episode of frost. Newer leaves of the affected plants were symptom free.

Wheat - tanspot showing yellow halos around the spots.

Wheat - showing yellowing and spotting of older leaves due to group 1 herbicide.

One sample of peas with leaf yellowing was received (Southwest). The yellowing present was observed at the same location (on the same leaf pairs) on each plant and was determined to be caused by environmental factors with frost suspected as the causal agent. One sample of sunflowers was received (SouthWest) that showed severe mottle of the cotyledon leaves and some mottle of first true leaves with some plants also showing distortion of the first pair of true leaves. Symptoms were believed to be frost related. Newer emerging leaves were growing normally.

Peas – same leaf pairs on each plant showing yellowing with frost being the suspected cause.

Sunflowers – mottle of leaves and distortion of first true leaves due to frost injury.

A number of inquiries regarding mysterious yellow powder have been received. We also received a question about “opening buds that are brownish and are not growing new shoots and needles” on spruce trees. The two occurrences are related. Spruce trees in some areas have been producing an abundance of pollen cones and an abundance of pollen to the degree that the pollen is highly visible on the ground and other surfaces in some cases. The production of large numbers of reproductive cones is stimulated by environmental conditions that occurred in the previous season. Reports of the abundant pollen production have come from the Red River, South Interlake, and North Parkland areas but could also be happening in other areas. Twigs producing the pollen cones may have little new shoot growth as in the photo below. Pollen production in pine is all beginning to occur.

Spruce – abundant produce of male (pollen producing) cones has occurred this season.

For spruce, two samples were received (North Parkland, Red River) that both had multiple problems including Stigmina needle blight, mite injury and an infestation of spruce bud scale. Several tree samples (green ash, Siberian elm) with chemical injury symptoms were received (Red River). Two samples of pine with evidence of brown mottling of needles were received (Southwest) for which the cause currently remains undetermined. One sample of Japanese lilac affected by Phyllosticta leafspot was received (Eastman). In this case leaves were puckered due to the infections occurring before the leaves had fully expanded and when the leaves did expand, the dead spots could not expand resulting in leaf puckering and distortion. Leaf spot diseases caused by many fungi on many hosts can cause the puckering effect when infections occur before leaves are fully expanded.

Lilac – leaf puckering resulted from early infection of Phyllosticta leaf spot.

Weed identifications for this week included waterpod (South Parkland), common peppergrass (Southwest), downy brome (Red River), water smartweed (Red River), meadow brome (Red River), and purslane speedwell (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.