NDSU Extension - Cavalier County

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8/6/2014

Crop disease pressure remains fairly low with the dry weather as of late, though some days were fairly humid.   As of this writing we are only seeing scab in isolated fields where incidence is quite low.   The same with sclerotinia in canola- a few fields have some incidence but most are white mold free!   The worst field I’ve found had over 75 percent of the plants infected with white mold in lodged areas but dead plants still produce some seed so yield loss is typically less than half the % infection.  Unfortunately this heavily infected field had a fungicide applied! 

Canola Blackleg is variable from field to field but mostly at low levels or levels that will not seriously impact yields.  Patches or scattered dead plants with no bleaching of the stem, just dying of the entire plant from the soil line up is typically blackleg.  You need to cut into the lowest part of the stem to positively identify blackleg as the inner tissue will be darkened to black hence the name blackleg!  The aggressive form of blackleg will typically be on field borders and causes severe lodging.

CLUBROOT:  Unfortunately, Clubroot was found in another field in Cavalier County this week so it is of utmost importance that we identify every single field that has clubroot or it will spread very rapidly throughout the area.   Once we identify the infected fields our only option is to clean, clean and clean all equipment that leaves the field as this disease spreads with not only plant material but soil particles!

Keeping canola a major crop in the region will take a futile approach to identify all fields with clubroot!  Then to follow good rotations and keep the disease confined to the field.  With this being such a devastating disease we will hold a couple meetings next week - one on Tuesday the 12th and another on Thursday the 14th at the Langdon Research Extension Center starting a 9 a.m.   Samples of actual clubroot at various stages will be on display and other identification keys to look for while swathing canola will be reviewed in detail.   Meeting portion should be completed in less than an hour but samples and other information will be at the center until noon these days.   Any questions please give me a call - or if someone wants additional meeting dates or times.  Stay vigilant on this one!!

SOYBEAN APHID SCOUTING ALERT: In southern Minnesota soybean aphid populations are growing fast with these moderate temperatures (high 70s F to low 80s F) and many new colonies and winged aphids are present in fields.  Locally very few if any aphids can be found but some fields in the southern part of the state are near the economic threshold level and will required treatment. The economic threshold is an average of 250 soybean aphids per plant, 80% incidence of an aphid on plants and increasing populations. Remember soybean aphid infestations are spotty and populations can vary field to field, so scout each individual field. Avoid counting the white-casted skins of aphid nymphs; they are not live aphids.  We also are observing an increase in beneficial ‘good’ insects in many fields. Waiting until the economic threshold will help conserve these good insects and mitigate insecticide treatments.

SUNFLOWERS: Continue to scout sunflowers for red sunflower seed weevil, banded sunflower moth, sunflower moth and Lygus bugs through R5.7 (70% pollen shed). North Dakota insect maps from the 2013 National Sunflower Association Sunflower Survey are available for banded sunflower moth, sunflower moth, Lygus bug, and other insect pests at:

SCOUT FOR SUNFLOWER RUST: As sunflowers begin to bloom it is important to scout for sunflower rust. Sunflower rust was found on volunteers and wild sunflowers early in the growing season, and environmental conditions have been very favorable for rust development, making disease development likelyRust is favored by free moisture, particularly heavy dews and/or fog.

*The IPM scout survey also indicates increasing grasshopper numbers along field margins. Monitor grasshopper feeding (in dry areas) in row crops as ditches are hayed and small grain fields are harvested.

*Dry bean leaf rust is being found in eastern portion of the state

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