Late blight NOT confirmed at this time
Late blight has NOT been confirmed at this time in southern Idaho. Samples that were submitted for identification turned out to be gray mold (caused by Botrytis). At this time, rumors of late blight in Elmore County and in the Rupert/Burley area have not been confirmed.
The weather has been favorable for late blight development, however, and it is recommended that any suspicious lesions be evaluated by trained personnel.
No confirmed late blight but storms increase chances of dise
Storms increase chances of late blight disease outbreak
By Phill Wharton
Even though late blight has not been found in Idaho so far this year, the thunderstorms that were widespread throughout the south of the state over the past weekend (June 20 and 21) and the heavy rain that we have had in the past three weeks created ideal conditions for potential late blight outbreaks in many locations. Late bight outbreaks are favored by wet weather with moderate temperatures (59 – 78°F), high humidity and frequent rainfall.
With the confirmed findings of late blight in 2008 and these conditions being prevalent in large areas of the state, the probability for the occurrence of outbreaks in manly locations throughout the state is high. Whether a late blight outbreak occurs or not depends on the presence of the late blight pathogen. In the spring, the late blight pathogen can be transmitted from infected tubers in cull piles or volunteers to potato foliage by airborne spores. Infected seed potatoes are also an important source of disease. Some infected tubers may rot in the soil before emergence, and not every plant that emerges from an infected tuber will contract late blight. Spores may be spread from infected plants in one field to healthy plants in surrounding fields by wind, splashed rain, mechanical transport and animals.
With the increased risk for late blight, efforts must be made to monitor crops closely for the incidence of disease. Particularly after plants close across the rows, look for late blight in the lower portions of the plant where the foliage stays wet longer. Scouting should be concentrated in areas of the field most likely to remain wet for the longest period of time, such as the center tower of pivot irrigation system and areas missed by fungicide applicators such as the edges of fields. Low spots where soil moisture is highest and parts of the field shaded by windbreaks are examples of areas where scouting should be intensified. If a field is thought to have late blight, care should be taken not to spread the disease from field to field when scouting. Disposable pants and rubber boots that can be washed after leaving a field should be worn if late blight is suspected or was found in a field. Late blight inoculum can also be spread from field to field on equipment, so this should also be washed after leaving the field.
As the risk of disease becomes greater, crop monitoring should be intensified. Late blight lesions may be confused with those of early blight (Alternaria solani) and gray mold (Botrytis cinerea) which are less severe diseases, thus it is important that an accurate identification of the disease symptoms is made and late blight is confirmed by a qualified diagnostician. If you think that you have late blight in your field you should contact the University of Idaho at 208 397 4181 for instructions on how to submit a disease sample, or contact your local crop consultant. With optimal weather conditions for a potential late blight outbreak, all growing regions in Idaho should be considered at risk with regard to the disease. A protectant spray should be applied before row closure, followed by another application 10 to 14 days later and then make fungicide applications based on current environmental conditions. Programs based on chlorothalonil (e.g. Bravo WS, Echo 90 DF, Equus DF) or EBDC-containing products (e.g. Dithane, Manzate, Manex, Penncozeb) will reduce the risk of disease development. Consult your local advisor for appropriate rates and additional combinations. If the disease is confirmed, interventive chemical control measures should be used.
To keep updated on the threat of late blight, call the late blight hot line at 800-791-7195.
Aphids in Wheat
High levels of aphid in winter wheat have been reported to me by a consultant. If wheat has reached the milk stage insecticide applications are not advised according to PNW Insect Handbook. For further information see http://uspest.org/pdf/reb88.pdf or http://uspest.org/pnw/insects?06SMGR01.dat .
Stripe Rust found in Winter Wheat
Active stripe rust was found in Idaho on Weston hard red winter wheat in a commercial field in the American Falls area on June 22, 2009. Weston was in milk stage, and stripe rust was found throughout the plant canopy. Infection was not severe, and was only 5% in severity and 8-10% incidence throughout the field. Stripe rust was found in Minidoka County north of Burley in Declo hard red winter wheat, and reported in northern Utah in winter wheat.
Stripe rust was also found on lower leaves of Moreland hard red winter wheat in breeding plots. Pustules were not actively sporulating, and Moreland was in early grain fill. (This was the Neeley area south west of American Falls.)
Most winter wheat is past the window of allowable fungicide application. Spring wheat varies in growth stages (depending upon elevation) from tillering to late boot. Excellent conditions exist for wheat production, especially in dryland production, where in some areas record-breaking rainfall has resulted in yield potential not seen in decades. Cold temperatures and frequent heavy rainfall has provided excellent conditions for the spread of stripe rust, but I have yet to see stripe rust in spring wheat or severe infections in winter wheat. NOW is the time to scout spring wheat fields for active pustules. Fungicide applications (up to labeled rate and growth stage) will control stripe rust. Always check labels and follow label directions. Additional information for control and pictures of stripe rust are available on our website at http://www.ag.uidaho.edu/scseidaho/ then click on "Disease Information" and then "Stripe Rust Information."
I have seen no stem rust or leaf rust. Other diseases found include Pythium and eyespot (Pseudocercosporella). Black chaff in wheat and bacterial stripe in barley have caused problems due to sleet and hail storms, and barley scald has progressed to the flag leaf in some commercial barley production fields in the Magic Valley around Twin Falls.
Juliet Windes
Juliet Marshall Windes
Cereals Cropping Systems, Agronomy and Pathology Assistant Professor
1776 Science Center Drive Suite 205
Idaho Falls, ID 83402-1575
208-529-8376 office
208-390-4859 mobile
208-522-2954 FAX
powdery mildew in sugarbeets
The Amalgamated Sugar Company Field Representatives are saying that now is the time to plan your treatments for powdery mildew in sugarbeets.
While mildew has not yet been found in the Treasure Valley, White Satin Field staff say the modes of action of the mildew chemistries work best if treatments are applied before mildew is found in the field. They are recommending mildew applications in the west end of the Treasure Valley the week after July 4 regardless of whether or not your fields are surface or sprinkler irrigated. You may also want to include an insecticide treatment for black bean aphid or loopers in the mildew tank mix. CONTACT YOUR WHITE SATIN FIELD REPRESENTATIVE FOR INFORMATION REGARDING THESE TREATMENT RECOMMENDATIONS AND ROTATION OF CHEMISTRIES.
