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corn earworm

Corn    Treasure Valley - Idaho

Posted on: July 16, 2009 by Jerry Neufeld

The University of Idaho CIS 366 entitled “Timing Corn Earworm Control,”states that summer moths will begin laying eggs in fresh corn silk at approximately 1300 growing degree days (GDD). Egg hatch and larvae attack will begin about 73 GDD later.

According to the Oregon State University GDD model for Corn Earworm (http://uspest.org/cgi-bin/ddmodel.pl?clm), we are currently at 956 GDD in the Caldwell area and 1003 GDD in the Parma area. We are accumulating approximately 22 GDD per day. We will hit 1300 GDD in the Caldwell area on approximately 8/1 and 1300 GDD in the Parma area on approximately 7/28. Those fields with fresh silk at 1300 GDD are most vulnerable to attack from corn earworm larvae.

The following information was taken from CIS 366 regarding corn earworm.
Corn can be “scouted” for corn earworm eggs to predict possible infestation levels. Examine 10 silk masses (about 2-day old) on each edge of a field but only in those fields which are beginning to silk or are silking. Examining a field in late silk for the first time is worthless; most of the eggs, if any were present, are already hatched, and the damage cannot be prevented.

When the egg counts average 1 egg per 2 silk masses, about 100% ear infestation will occur in the field and other fields of like maturity in the vicinity. With 1 egg per 2 silk masses, about 1 inch of each ear tip will be damaged; 1 egg per silk mass will result in about 2 inches of the ear tip damage, etc. When the days and nights are warmer than usual, the damage may double because the earworm will develop faster than the corn.

Fields should be scouted about every 2 to 4 days, depending on temperatures. Once economic egg levels are reached, determined on the basis of damage expected, further scouting is unnecessary. All fields which silk after that time in that vicinity will be subject to damage.

No chemical control will control worms in the ears, so sprays must be timed to control the larvae on the silk before the worms enter the ears. Make the first application when the plants are 50 percent silk, and repeat in 5 to 7 days or as necessary.

For control information from the 2009 Pacific Northwest Insect Management Handbook go to the following web address: http://uspest.org/pnw/insects. In the drop down boxes click on “commercial vegetables” and then “sweet corn.”

» Corn Earworm Egg

» Corn Earworm Larvae

No confirmed late blight but storms increase chances of dise

All Crops    All Locations

Posted on: June 30, 2009 by Phill Wharton

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.

powdery mildew in sugarbeets

Sugarbeets    Treasure Valley - Idaho

Posted on: June 25, 2009 by Jerry Neufeld

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.

Late blight forecast for southern Idaho for 2009

Potato    All Locations

Posted on: June 12, 2009 by Jeff Miller

Our cool, wet spring has created an environment favorable for the development of late blight. A prediction model developed at the University of Idaho by Henderson et al. indicates that the likelihood of late blight development is relatively high. The forecast value is highest in the Fort Hall area and lowest in Parma. The actual occurrence of late blight and the date of first appearance will be affected by subsequent weather and fungicide application patterns.

The forecast in 2008 was also relatively high early in the season, but hot, dry weather was likely responsible for the limited development of late blight. It is critical to scout fields. Any area of the field where plant leaves and stems stay wet for extended periods of time (e.g. near the center points of pivots, irrigation overlaps, along mainlines, near windbreaks) should be scouted intensely. The use of a protectant fungicide is recommended prior to row closure.

A full discussion of different fungicides labeled for late blight control, along with information on application method and frequency is attached here and also available at:

http://www.millerresearch.com/reports/Overview_of_Fungicides_for_Late_Blight.pdf

» Fungicide for late blight control

Fruit Advisory

Tree Fruits    Treasure Valley - Idaho

Posted on: June 11, 2009 by Tony McCammon

Codling moth models indicate 35% of Larvae have hatched out. This is the most critical time to protect your fruit as another 30% of first generation larvae will be hatching out this week. This weekend Peach, nectarine, and apricot trees should be protected from the Peach twig Borer. The weather forecasts rain showers off and on for the next week. Use rainfast product for your applications. For more information on Rainfast products, and additional information concerning this alert view the payette county Extension website and check out the June 11 advisory.

» 650_1.pdf

Tree Fruit Pest Advisory

Tree Fruits    Treasure Valley - Idaho

Posted on: June 11, 2009 by Tony McCammon

The Attached Advisory contains Peach twig Borer, Peach tree borer, Codling Moth, White Leafhopper, and western Cherry fruitfly information for Commercial and Home orchardists. View the Payette County Extension Website
for further information.

» 649_1.pdf