NDSU Extension - Mercer County


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Foxtails, Sunflower Rust, Emerging Spruce Disease

foxtails, weeds, sunflower rust, sunflower fields, spruce disease, needle cast

Submitted by Craig Askim, Extension Agent, Agriculture and Natural Resources


Green/yellow foxtails seem to be taking over the county this year. These weeds are not noxious but they can spread quickly so you don’t want them to go to seed.

Foxtail grasses are loaded with seeds now. In a lawn, mow these seed heads before they scatter seeds to the ground. In a garden, pull these shallow-rooted weeds. Green and yellow foxtails are annual grasses. The good news is these foxtail weeds in your yard today will die from frost. The bad news is every plant can produce up to 10,000 seeds before it dies.

You can prevent green and yellow foxtail seeds from emerging in a lawn by using pendimethalin. This herbicide is often mixed in springtime fertilizers to prevent crabgrass from emerging. Crabgrass and foxtails can be controlled with this application. Apply in April.

Foxtail barley is a short-lived perennial often found in recently disturbed sites such as new residential areas. It is shallow rooted and can be cultivated or pulled out. A spot spray of glyphosate (Roundup) is another option. A strategy to reduce foxtails is to develop a thicker lawn. Thick lawns will naturally fade out foxtail and other emerging weeds in the future. Thin lawns can be improved this fall by over-seeding (August 15 to September 15 is best) and fertilizing in late September.

Sunflower Rust

Producers are encouraged to scout for sunflower rust in sunflower fields. NDSU field scouts found sunflower fields in the R3 stage with rust in western North Dakota. Incidence was 66% and severity was 24%, well above the treatment threshold for this disease. Sam Markell, NDSU Plant Pathologist, said any infection with 1% or more severity should be treated.  More information on sunflower rust can be found in the NDSU Sunflower Production Guide.

Emerging Spruce Disease

Stigmina needle cast is becoming more prevalent on spruce trees in North Dakota. It is deemed as an aggressive pathogen that may be very hard to manage. Colorado blue and Black Hills’ white spruces are both susceptible. Spruce needle diseases are commonplace, especially in plantings where trees are planted close to one another. Rhizosphaera needle cast is most common and can be controlled with two applications of chlorothaloni per year for two years. In contrast, Stigmina needle cast requires three or more applications for four to five years.

The best way to deal with these diseases is to avoid them. Black Hills’ white and Norway spruces are generally more resistant to needle diseases than Colorado blue spruce.  Avoid planting new spruces near old spruces showing disease. Reduce drought stress. Consider mulching around trees and irrigating during dry weather. Avoid sprinkling water on branches of spruce. You should space trees to allow for sunlight and air circulation within the planting and thin shelterbelts as they mature.  Do not shear spruce trees since this creates a dense growth of needles that is likely to stay humid longer. More information is available in the NDSU publication The Old and the New: Two Needle Diseases of Spruce in North Dakota – F1680.


Until Next Time!


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