Crop Diagnostic Lab Report

 

Week of July 27 - 31, 2009

Four samples of wheat diagnosed with Wheat Streak Mosaic Virus (Pembina, South Parkland, Central Plains).  One sample of wheat with complaint of yellowing and browning on the sheath below the flag leaf was diagnosed as injury from thrips (South Parkland).  Thrips are very small insects that hide inside the sheatha and feed by rasping on the sheath tissue but will also feed on leaves.  Two samples of wheat of cultivar Kane with complaints of necrotic and purple blotching of leaves were received (South Interlake, Eastman).  The problem is believed to be physiological but cause is currently unknown.  One sample of wheat was diagnosed with Fusarium root rot (Eastman).  One sample of wheat was diagnosed with environmental leaf tip burn and tan spot (Central Plains).  One sample of wheat was diagnosed with chemical drift injury suspected to be caused by glyphosate (Red River).  One sample of barley was diagnosed with net blotch (Central Plains).  One sample of barley was diagnosed with root rot (Pembina).

Wheat – the bleached appearing areas on the stem sheath are from feeding injury by thrips.  The middle stem also has a spot of injury from a chewing insect.

 

One sample of soybean with poor growth due to iron deficiency was diagnosed (Red River).  One sample of soybean with anthracnose and Fusarium root rot was diagnosed (Red River) and one with just Fusarium root rot (Eastman).  One sample of soybeans with Phytophthora root rot was diagnosed (South Interlake).  One sample of soybean with brown spot (Septoria) leaf spot (South Interlake).  One sample of soybean with root rot from Pythium and Fusarium was diagnosed (Red River).  Two samples of soybean with bacterial blight was diagnosed (Red River, Southwest).  One sample of soybean with symptoms of poor color and poor growth was found to be affected by stress rather than disease (Eastman).

Soybean – bacterial blight causes brown spotting, spots may have a yellow halo, damaged leaf areas may tatter.

Soybean – these soybean plants affected by Phytophthora root rot show a brown discoloration moving up the stem but other diseases can cause similar symptoms.

Soybean – this soybean plant was found to be affected by anthracnose.  The black dots on the browned stem area are the spore producing structures (acervuli) of Colletotrichum, the fungus that causes anthracnose.

 

One sample of canola with plants of greatly varying size and development was determined to be due to uneven emergence and field factors (Red River).  One sample of canola with pale flower colour and poor pod development was diagnosed with a suspected sulphur deficiency (Red River).  One sample of flax with dead plants and yellowing plants was found to be affected by Fusarium wilt (Pembina).

Two samples of canaryseed with symptoms of poor colour and poor growth were diagnosed with stress symptoms due to possible nutrient deficiency (Red River).  One sample of corn was found to be affected by root rot (North Parkland).

One sample of parsnips had leaf bronzing symptoms and was diagnosed with environmental injury (Central Plains).  One sample of tomatoes that had displayed a sudden wilting of plants was diagnosed with Verticillium wilt (South Interlake).  One sample of hydroponic greenhouse cucumbers with leaf chlorosis and necrosis was diagnosed with a combination of nutrient deficiency and Pythium root rot (Southwest).

One sample of strawberry with dying plants and poor fruit development was diagnosed with black root rot (Central Plains).  Black root rot of strawberry is a common problem in Manitoba in areas with heavy poorly drained soils and is caused by a complex of several different disease organisms.  One sample of raspberry with yellowing and browning of leaves was found to have a severe infestation of spider mites on the leaves (Pembina).

One sample of pine with Dothistroma needle blight and possible chemical injury was diagnosed (Valleys North).  One sample of spruce with injury from mites and stress was received (North Parkland).  One sample of elm with dieback symptoms was diagnosed with Dutch elm disease (Pembina).  One sample of poplar with severe dieback symptoms was diagnosed with Cytospora canker (Red River).  This disease is common on poplar and can do serious damage to trees under stress from drought or nutrient deficiency.

Weed identifications for this week were flixweed (North Interlake), swamp milkweed (South Interlake), lamb’s quarters (South Interlake) and water hemlock (North Parkland).

 

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.