Pests & Crop Diseases

Your Land, Your Investment!

Why You Should be Always Scouting for Pests


Scouting your fields on a regular basis is crucial in comprehensive pest management decision - making. Why treat your field for Grasshoppers when there is no significant damage being done or vice versa when the damage is already done? Either side is most often environmentally and economically irresponsible. This is where solid scouting techniques come into play. During the growing season fields should be scouted on a weekly basis and even a daily basis depending on the economic threshold of the pest. When scouting you should be documenting what you find. If you do find a pest, you want to be able to have a short term and potentially long term plan. A good sweep net is a solid investment in your pest scouting management. 

Click here for an excellent guide for proper field scouting techniques.



Crop Diseases

  • Blackleg (Leptosphaeria maculans) Declared a Pest in Alberta

Blackleg is a fungal disease found in canola across the province and western Canada. In 2017, 25 fields in Saddle Hills County were surveyed and tested for Blackleg – one tested positive. Blackleg is characterized by white round to irregular shaped spots on the leaves; usually dotted with tiny black spots (pycnidia). Lesions on the stem are usually found around the base or at points of leaf attachment. Blackleg infection on leaves prevent proper absorption of sunlight while lesions on the stem prevent water and nutrients from reaching the pods and seeds – leading to reduced yield. Scout for Blackleg around swath timing, clip 10 – 20 stems just above soil level and using the Blackleg Field Rating Scale determine level of infection(Figure below). If blackleg is present (1 - 5), it is encouraged to have longer rotations (3-5 years) and use a blackleg resistant canola varieties when canola is seeded.

Blackleg

Video Blackleg Disease and Resistance Management - Click Here

  • Fusarium Graminearum Declared a Pest in Alberta

In 2017, 25 fields in Saddle Hills County were randomly collected and tested in the county for Fusarium Graminearum; 3 fields tested positive. It is a common fungal disease of cereal crops: wheat, barley and oats. F. Graminearum reduces yield as well as grain quality. Infected kernels may contain mycotoxins such as vomitoxin(Deoxynivalenol) that causes reduced feed intake, fertility and potentially death in livestock. The infection may not always be visible but is distinguished by early maturing reddish colored kernels in the head (Figure below). Managing F. Graminearum begins with clean, healthy seed along with regular seed health testing followed by treatment of seed, longer cereal rotations and growing varieties with higher levels of resistance. 

Fusarium


  • Clubroot (Plasmodiophora brassica) declared a Pest in Alberta

Clubroot was first discovered in Alberta around the Edmonton area in 2003. In 2017, the first confirmed case in the Peace Region was found in Big Lakes County and later that same year in Greenview. It is a soil – borne disease in canola that overwinters. The disease causes galls to form on the root system (Figure below). These galls cut of water and nutrient supply and lead to premature death. Currently there are no solutions for clubroot once the soil is infested. Management practices can be done to mitigate the chance of getting clubroot; not bringing equipment from infected counties (agriculture as well as oil and gas). Once the soil is infected; sanitation of equipment, longer crop rotations and the use of resistant varieties can be used to reduce spore load.  

Clubroot

Source:www.canolacouncil.org/canola-enclopedia/diseases/clubroot/about-clubroot

Other Resources:

Clubroot Video Click Here.

Crop Rotations: Issues and Opportunity – AB Ag and Forestry


  • Sclerotinia

Sclerotinia is one of the most destructive fungal diseases found in canola. It overwinters in the soil and crop stubble. The severity of infection is variable between years as well as regions and fields. Sclerotinia becomes more prevalent with tighter canola rotations (found commonly in the Peace), higher yield targets (increased crop density), rainfall (humidity) and timing of flowering. The infection is often discovered when it is too late. The infected pedals of the canola flower fall down onto the junctions of the canola plant (Figure below). Due to Sclerotinia being highly variable due to environmental conditions it is encouraged to keep track of field history as well as regular foliar fungicide spraying.
Sclerotinia

Source: Justine Cornelsen

Sclerotinia ChecklistClick Here.


Insects

  • Grasshoppers

There are 80 different species of grasshoppers in the Canadian Prairies alone; the most common pest grasshopper in recent years have been the two-striped grasshopper (Figure below) and the clear-winger grasshopper (cereal and grass). Crop pest grasshoppers hatch in late May and early June, are brownish black in color and have tiny triangular wing buds. Pest species of grasshoppers are also silent. Grasshopper pressure has an increased occurrence in drier climates. They are able to have multiple generations per year.

 

Economic Threshold: 10 grasshoppers/m2 and above if feeding is evident.

Grasshoppers

Source: insectsofalberta.com

Link to an excellent source of material on Grasshopper pressure - Click Here.

  • Diamondback Moth

In 2017, there was an increase infestation of Diamondback Moths in the Peace Region. Diamondbacks occur throughout North America in canola and mustard crops. They migrate northward from infested areas on wind currents and are able to produce as many as 4 generations/year. Crop damage occurs at the larvae stage (Figure 1) when they feed on the leaves as well as other green tissue. Scout for Diamondbacks in late July – August at least twice a week. To check insect pressure; remove plants in 12” square (0.1m) and beat the plants out onto a clean surface and count the larvae.

Economic threshold:  20 to 30 larvae/0.1 m2 (about 12” square) at the advanced pod stage. This works out to approximately two to three larvae/plant if plant population is close to 100 plants/m2).

Diamondback

Photos: Roy Ellis

For more on the Diamondback Moth – Click Here.

 

  • Wheat Midge

Wheat Midge (Sitodiplosis mosellana) is found in most areas in the world where wheat is grown and significant damage to wheat crops has been reported and found in Western Canada. Crop damage occurs in the larvae stage when the larvae feed on the developing kernel causing it to shrivel, crack and become deformed. With no visible external signs, it often gets mistaken for frost or drought damage. Damage will vary amongst locations as well as in individual heads. Monitoring of wheat fields between heading and flowering is crucial to identify infestation and to take appropriate action.

Inspections should be carried out later in the evening (after 8:30 p.m.) in at least four locations in the field, when female midge are most active. They are most active when temperature is above 15°C and when wind speed is less than 10 km/h. Some management practices that can be used to control midge populations are: avoid continuous wheat cropping, early seeding or early maturing varieties and maintaining parasitic wasp populations.

Wheat Midge

For additional information please click here.

 

  • Flea Beetles

Flea beetles (Coleoptera: Chrysomelidae) feed on plants of the mustard family grown across Canada. Two main species are found to cause significant damage; Crucifer flea beetle and striped flea beetle. Flea Beetles only have 1 generation per year in Western Canada; overwintered adults emerge and feed on canola in the spring and in the fall their adult offspring feed. They overwinter near the surface in crop trash and grass. They become active when we have extended periods of warm weather in April and May. The larvae feed on root hairs and taproots of seedlings while the adults feed on cotyledons and sometime the stems. Damage to the crop is most prevalent in the first two weeks after seedling emergence.

Once the crop is at the 3 – 4th leaf stage the plant is established and able to outgrow the damage. Scouting for flea beetles should begin the fall prior – if high populations are present, look into a seed treatment to provide extended control. Agronomic practices that encourage good stand establishment and rapid growth will reduce the impact of flea beetles on yield.  The economic threshold for flea beetles is 25% defoliation which is based on 75 – 150 plants per square meter. 

Flea Beetles

Flea Beetle

For additional information please visit Canola Council of Canada’s link here.

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