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corn earworm

Corn    Treasure Valley - Idaho

Posted on: July 28, 2009 by Jerry Neufeld

Dr. Jim Barbour from the UI Parma R and E Center, Terry Clinton from Crookham Company and I are collaborating on a project to trap corn earworm moths across the Treasure Valley. We set out 12 traps at various locations from near Melba to near Weiser. I am checking the traps every few days and posting the moth counts to this website. Below are the moth counts from this week . Purdue University recommends the treatment threshold to be 10 moths per trap per night. The growing degree day model from Oregon State University is predicting moths will begin laying eggs in fresh corn silk in late July to early August with the egg hatch beginning a few days later.

Date: 7/21/09 to 7/27/09
Location # of Moths caught

South ofWeiser 1 --- 0
South ofWeiser 2 --- 1
NW of Middleton --- 2
North of Wilder --- 7
South of Homedale 1 --- 1
West of Caldwell --- 1
East of Homedale 2 --- 1
NE of Marsing --- 0
North of Melba --- 0
East of Kuna 1 --- 0
East of Kuna 2 --- 0
East of Kuna 3 ---0

Total moths caught --- 13

corn earworm

All Crops    Treasure Valley - Idaho

Posted on: July 22, 2009 by Jerry Neufeld

Dr. Jim Barbour from the UI Parma R and E Center, Terry Clinton from Crookham Company and I are collaborating on a project to trap corn earworm moths across the Treasure Valley. We set out 12 traps at various locations from near Melba to near Weiser. I will check the traps every few days and post the moth counts to this website. Below are the moth counts from yesterday. Purdue University recommends the treatment threshold to be 10 moths per trap per night. The growing degree day model from Oregon State University is predicting moths will begin laying eggs in fresh corn silk in late July to early August with the egg hatch beginning a few days later.

Date: 7/17/09 to 7/21/09

Location # of Moths caught


South ofWeiser 1 --- 0
South ofWeiser 2 --- 0
NW of Middleton --- 0
North of Wilder --- 0
South of Homedale 1 --- 7
West of Caldwell --- 0
East of Homedale 2 --- 4
NE of Marsing --- 1
North of Melba --- 0
East of Kuna 1 --- 0
East of Kuna 2 --- 2
East of Kuna 3 --- 0

Total 14

» Corn Earworm Adult Moth

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.