Weekly Field Crops Pest Report 2007

View From The Field

Eastern NYS
Ken Wise, NYS IPM

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It’s April… It’s snowing? The calendar tells us another growing season is here and with it time for another series of our NYS IPM Weekly Field Crops Pest Report. This year we plan to distribute the report two ways. The first is just like last year’s report in that we will send it to the field crop agricultural extension educators throughout NYS. The second option is that we will send the pest report website location once a week by email to the Cornell field crop list serve. We hope you find the information in the report to be timely, easy to use, and even a little entertaining. Please send us your feedback so that we can best meet the needs of our audience. Our contact information is always listed at the end of the report.

Last year at this time I was already scouting alfalfa. This year the only crop I have been able to monitor so far is triticale at the Cornell Research Farm plots at Valatie. Here is a photo of one disease I observed there:

These plots, unfortunately, contained a high incidence of snow mold (See photo and article below for more information)

Snow Mold in Cereal Grains

Eastern NYS
Ken Wise, NYS IPM

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Pink snow mold (Fusarium nivale) and speckled snow mold (Typhula species) are the two main fungi that cause this disease. Pink snow mold is by far more common than speckled snow mold.

Disease Cycle

Fusarium infects living plants as conidia or mycelium. Typhula over-winters as sclerotia in plant debris or soil.

When the spores of speckled snow mold or pink snow mold germinate they infect the leaves of the plant. The older leaves that touch the soil surface under the snow canopy are first infected. The crowns may or may not become infected. Fungi under the canopy of snow will continue to develop eventually producing conidia or sclerotia. The disease is most aggressive at temperatures that are slightly above freezing.

Signs in the Field

Many times snow mold occurs in patches in the field after the snow melts. You will observe a fungal mass on the leaves that appears pinkish, whitish or gray. Many times the leaves will have brown-black fungal bodies which are called sclerotia. The leaves could be partly or entirely killed. If snow mold infects the crown it will kill the plant. If the crown is not infected most likely new leaves will grow back and the plant should produce grain.

Scouting Wheat Diseases in the Snow?!?!

Julie Dennis, NYS IPM Program

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What? We should be scouting wheat fields for early season diseases while the snow is still flying? Seriously, once this new-fallen snow melts, it’s time to get out and check how the wheat is doing this spring. Wheat fields I’ve observed lately greened up in late March, and are now blanketed with a fresh coating of snow, marking time until a warm up.

Once your scouting begins, watch for bare spots. Bare spots in fields at this time of year are not unusual, and wheat diseases may be to blame. Unhealthy plants do not grow vigorously in the spring due to infection with pathogens that cause root and crown rots. Many different fungal organisms cause root and crown rot diseases of wheat, and it is often difficult to distinguish which causal agent is present. The most common organisms that cause root and crown rots include Fusarium and Pythium. Seedling blights and rots are more likely to be severe under excessively wet conditions and when soil temperatures are too low for good growth. Plants injured from frost heaving, resulting from repeated freezing and thawing, are especially vulnerable. Over the past winter, most areas had plenty of snow cover to insulate plants, so dormant plants were pretty well protected from the elements.

Fusarium seedling blight: Seedlings and tillering plants infected with Fusarium seedling blight are generally stunted and yellow, and the crown, roots, or lower stem take on a brown to reddish-brown water-soaked rotten appearance. If plants survive, they have a brittle, stunted appearance and are paler green than healthy plants. Plant death can result in patchy stand reduction. The Fusarium fungi can survive in plant residue or as dormant spores in the soil for several moths.

Pythium root rot: The “water mold” that causes Pythium root rot may first infect the seedlings in fall-planted wheat, though seedlings are rarely killed. The stunting of seedlings resulting from Pythium infection may go unnoticed until other plants in the field begin healthy, vigorous growth in the spring. Roots of infected plants begin to turn brown then disintegrate beginning at the root tips. Plant mortality can occur if infection is severe enough for the rotted roots to break away from the crown. Pythium spores survive several years in soil without a host, and spores are present in all soil types. Infection of plants is greatest in cold, wet, clay soils.

Temperatures in the low 20’s last week may have resulted in spotty frost injury to tillering plants. Resulting yellowing of leaf tips may be similar in appearance to viral disease and nutrient deficiency symptoms. Once plants get growing, any minor injury will be quickly outgrown.

Planting Bt Corn This Year? Don’t Forget the Refuge

Julie Dennis, NYS IPM

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Use of Bt corn for management of corn rootworm (CRW) has become a common practice across New York State. European corn borer (ECB) is not as significant a threat as rootworm, but Bt corn is also available for this pest. Many of our hybrid choices are “stacked” - meaning they contain Bt traits to management both of these pests. Regardless of the targeted pest or pests, a non-Bt refuge must be planted when a Bt corn crop is planted. Why is a refuge planted?

1. To keep a portion of the population from being exposed to the Bt toxin

2. To prevent the development of CRW or ECB populations resistant to Bt

Because the EPA requires growers by law to plant a refuge - 20% of the acres must be planted to Bt corn. When the seed is purchased, an agreement to plant the refuge is signed.

If pests become resistant, this tool will be lost. (Remember, having more options available allows us to better implement IPM!)

Here’s a brief overview of refuge requirements for Bt Rootworm corn: (The refuge requirements are more strict for CRW than for ECB, so if CRW requirements are followed, you’re all set for both pests)

• Plant at least 20% of corn acres with a corn hybrid that does not contain Bt technology for CRW

• The refuge can be treated with soil insecticide or seed applied insecticide, but NOT with other Bt insecticides

• Plant the refuge at the same time as the Bt corn, in a field with similar crop history

• Plant the refuge within the field or in an adjacent corn field (your neighbor’s corn field is NOT considered your refuge!)

Options for the configuration of refuge include:

• Adjacent to Bt corn field (not further away than a road, path, or ditch)

• Field end rows or field perimeter

Mixing of non-Bt seed with Bt rootworm seed for inter-planting is not permitted

National Asian Soybean Rust Report (April 9th)

Gary C. Bergstrom-Cornell University

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A record breaking frost On April 7/8 resulted in temperatures in the Florida Panhandle below freezing for several hours. The impact of the freezing temperatures on the rapidly growing kudzu in this area will not be known for several days, but it could reduce the build up and potential spread of soybean rust for several weeks. Prior to this frost event, warmer temperatures had increased the growth of kudzu throughout the Southeast. Scouting efforts have increased on new growth of kudzu vines and on newly emerged soybeans from recently planted sentinel plots. Soybean rust has been detected on kudzu in 9 counties in Florida and in five counties in each of Georgia and Alabama. In some counties, the infected kudzu has been destroyed and rust in some of those locations is no longer found. The disease was also detected on soybeans in one county in Texas, but that field has since been cultivated and planted with corn. See the USDA Public PIPE website.

Clipboard Checklist

Keith Waldron-NYS IPM

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General:

• Walk fields to check tile flow, check and clear drainage outlets. Look for line breaks.

• Observe wet areas and plot on aerial photo of farm for future drainage considerations and crop decisions

• Maintain crop records by field, including variety, planting date, pesticides used, nutrient inputs including manure, etc.

• Watch for early season weeds: winter annuals, chickweed, henbit, field penny cress, shepherd's purse, giant ragweed, lambsquarters, Pennsylvania smartweed, common sunflower

• Store snow shovel, summerize sno-blower?

Alfalfa and Small Grains:

• Monitor alfalfa for Alfalfa Snout Beetle (In Oswego, Jefferson, Cayuga, Wayne, Lewis, St. Lawrence, Clinton, Essex, and Franklin counties)

• Monitor alfalfa for Alfalfa weevil as weather continues to warm

• Evaluate established legume stands for winter damage, determine average alfalfa stand count, adjust crop plans if necessary

• Monitor winter grain fields for overwintering survival, virus disease symptoms, goose damage

Corn:

• Prepare land for corn if it is dry enough and begin planting the last week of April if it is dry (even if it is cold!)

Pastures:

• Check and mend fences as needed.

• Check crop growth

• Review/Plan rotation system

Storage:

• Check forage allocation and anticipate feed program adjustments as forages from previous year are used up

• Plan where forages should be stored for optimum allocation next feeding season

Equipment:

• Arrange for custom weed control or check your own application or cultivator equipment for repairs.

• Check nozzles, pumps, etc., recalibrate pesticide application equipment regularly before use.

• Calibrate manure spreaders - maintain records on amount spread per field

Contact Information

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Julie Dennis:
IPM Area Educator, Livestock and Field Crops, Western NY
Phone: (315) 331-8415
Fax: (315) 331-8411
Email: js38@cornell.edu

Keith Waldron: NYS Livestock and Field Crops IPM Coordinator
Phone: (315) 787 - 2432
Fax: (315) 787-2360
Email: jkw5@cornell.edu

Ken Wise: Eastern NYS IPM Area Educator: Field Crops and Livestock
Phone: (518) 434-1690
Fax: (518) 426-3316
Email: klw24@cornell.edu