Purple top wilt has been reported by many potato producers. As you may recall the aster leafhoppers arrived in North Dakota in large numbers earlier this summer.
NDSU field scouts also look for wheat stem maggot injury, and they observed the white wheat heads due to wheat stem maggot feeding in 42% of fields surveyed last week, with these fields having an average of 6% of heads affected.
IPM field scouts surveyed 73 wheat fields during the second week of July. The average growth stage of these fields was early milk, at least two weeks ahead of the average growth stage in 2011.
IPM scouts looked at 38 wheat fields during the 4th of July week. The average growth stage for the wheat surveyed was at the end of flowering.
Goss’s wilt in corn was confirmed by the NDSU Plant Diagnostic Lab last week in a sample of corn leaves from Richland County. This disease was confirmed in five of six samples tested last year by the NDSU Plant Diagnostic Lab, and was independently confirmed in corn in 2011 by various seed corn companies.
Cercospora leaf spot is the most common and damaging foliar disease of sugarbeet in Minnesota and North Dakota. The disease is caused by the fungus Cercospora beticola which overwinters in infected sugarbeet debris.
White mold is a concern in broadleaf crops once they enter bloom. Below is a brief review of favorable environmental conditions, crop susceptibility, and fungicide timing for white mold.
The ND IPM field scouts surveyed 94 wheat fields during the last week of June. The average growth stage across all fields was early flowering, but ranged from flag leaf emergence to early dough stage.
We have not evaluated fungicides for stripe rust control in ND, but wheat pathologists from states (such as KS, NE, AR, WA, OH) with a long history of stripe rust have, over many locations and years.
Wheat: Last week, ND IPM scouts looked at 77 wheat fields. The average growth stage was mid- to full head emergence.
As canola enters bloom it becomes susceptible to white mold. Growers may be considering applying a fungicide to help manage the disease.
A few more observations of wheat leaf rust have been reported this past week, but the big news now is that stripe rust has increased substantially over the past week in some areas.
In the last couple days I have received multiple questions concerning the canola that got hail damage in the North Central/Northeast part of the state. The questions mostly revolved around the crops susceptibility to white mold.
Last week I wrote an article about the early spore stages of sunflower rust being identified in Manitoba. Since then, the aecia stage has been identified in North Dakota.
Heavy rains across parts of ND this week will increase the risk of small grain diseases. To determine fungicide need, growers and agronomists need to know the crop growth stage, crop condition, and disease potential.
Weekly results of the scouting data accumulated during the IPM survey across the state are posted online.
Wheat leaf rust, caused by Puccinia triticina, was detected in winter wheat by field scouts in ND on June 18, in Cass County in the east and in Slope County in the southwest. Leaf rust was at trace levels. This is the first NDSU confirmed detection of wheat leaf rust this year. We don’t know the race of leaf rust detected; in recent years many of the leaf rust races present were ones that could defeat a wheat leaf rust resistant gene called Lr21, found in some of the most commonly grown spring wheat cultivars in our area.
Pockets of stripe rust are continuing to be found across the state, with the disease showing up primarily in eastern counties and in areas that have had more rain, but detections are still hit and miss in a region. Stripe rust symptoms have been seen in winter and spring wheat fields.
The fusarium head blight forecasting website provides valuable information. (www.wheatscab.psu.edu)
The optimum fungicides for managing Fusarium head blight are Prosaro or Caramba. These two fungicides provide greater reduction in FHB severity and DON levels than other fungicides, but they must be applied correctly because the target for application is the narrow, vertical grain head, not the leaves.