ISSUE 11 July 13, 2006
WHEAT AND BARLEY OBSERVATIONS, July 3-7
Wheat: NDSU IPMís summer field scouts surveyed 97 wheat fields during the week of July 3-7. The average growth stage of these crops during that week was Zadoks 67 = flowering, with a range from jointing to late dough stage.
With the high temperatures, most of the crop is maturing fast, and in the driest parts of the state, even being cut for hay.
During the first week in July, tan spot was found in almost every field, with average severity on flag leaves at 6.7%. Septoria leaf spot detections increased, found in 33% of the fields, with an average severity of 16.2%. Leaf rust was observed in 27.8% of the surveyed fields, and average severity of leaf rust in infected fields was 2.2%. Loose smut was found in 36% of post-heading wheat fields.
Wheat stem maggot incidences from 1-15% were commonly reported by the field scouts.
Barley: Seven barley fields were surveyed across the state and spot blotch fungal leaf spot was found in all fields. The only other problem of note in barley was the presence of aphids and thrips in most fields.
Fusarium head blight was detected in one surveyed wheat field in Sargent county, at 2% incidence. Apart from the IPM survey, Dr. Shaukat Ali of the Plant Pathology Department, observed a 2% incidence of scab on July 11, in a wheat field planted onto corn stubble, near Sabin, MN. Nearby fields, not on corn ground, had no observed scab.
Extension Plant Pathologist
WHITE MOLD: WHATíS THE RISK FOR THIS YEAR?
Iíve recently had some questions regarding the risk of white mold for this year, and if fungicide applications are still needed with the hot and dry weather. To answer this question, the basic biology of the white mold fungus, Sclerotinia sclerotiorum, should be addressed. To get the fungus started off on the right foot, at least 1 to 2 inches of rain are needed in the 10 to 14 days before the crop begins to flower. This moisture is required so that the fungal sclerotia (overwintering structures) in the soil will produce the mushroom-like fruiting bodies called apothecia (see figure). Ascospores, which are released from the apothecia, cause the infections on crops; however, the foliage in the canopy must be wet for 1 or 2 days before any infections can occur. These ascospores are also very sensitive to heat. The foliage must remain wet for the disease to progress. At temperatures above 85 , infection and disease development will not occur. With the white mold fungusí large dependence upon moisture and inability to be active in high temperatures, it is unlikely that it will be causing damage to crops this year. Many susceptible crops such as soybean, canola, and dry bean have been flowering through the hot and dry weather and will most likely escape infection for this year without a need for a fungicide.
Apothecia of Sclerotinia sclerotiorum emerging from sclerotia
(courtesy J. Venette)
SECTION 24(c)LABEL FOR QUADRIS ON SAFFLOWER
A section 24(c) label for the use of Quadris fungicide on safflower to control Alternaria leaf spot was recently approved. According to the label, 6 to 15.5 fl oz/A can be applied, with no more than 27.5 fl oz/A being applied per season. There is a 30 day PHI. If an application is needed, the first application should be applied at early bud. For a copy of the label, go to the ND Dept of Ag Pesticide website at:
or the NDSU Extension Pesticide website at:
The label will expire on December 31, 2006.
Carl A. Bradley
Extension Plant Pathologist