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NY Weekly Field Crop Pest Report, 2005

May 5, 2005 Volume 4 Number 3

1. View from the Field

2. Alfalfa Snout Beetles on the March…

3. When Do Weeds Wake-up in the Spring?

4. Seed Decay and Seedling Diseases of Corn

5. Alfalfa Crown Rot

6. Stagonospora Nodorum Blotch-Small Grains

7. Growing Degree Days in NYS

8. Why did the Dandelions Get Into the Alfalfa Field

9. Clipboard Checklist

10. Contact Information

View from the field

Ken Wise, NYS IPM

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Hello Field Croppers:

Tactical Agriculture (TAg) is a program most of you are familiar with. This year the LFC IPM team is again working with local CCE personnel to implement TAg programs across NY. New this year, thanks to a grant from the NE Soybean Board, we will conduct the first soybean TAg program in NYS. This new effort will be launched in Oneida, Orleans, and Cayuga Counties. Local leadership for these county-based TAg teams will be provided by Jeff Miller, Mike Stanyard and Shawn Bossard.

Traditional TAg teams (Corn and Alfalfa) will be offered in Lewis County (Jennifer Beckman), Franklin County (Mathew Copper) and in Essex County (Anita Deming).

For specific information and TAg resources view the following webpage: NYS IPM Tactical Agriculture Program

Alfalfa Snout Beetles on the March

Keith Waldron, NYS IPM

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It's time for the annual alfalfa snout beetle fun run. Warmer spring temperatures signal alfalfa snout beetle (ASB) adults to begin their emergence from the fields where they have been feeding as larvae on alfalfa roots for the past two years. In addition to alfalfa, other host plants for ASB include: red clover, dock, wild carrot, quackgrass, and white clover. Nonhosts, i.e. good crops to have in rotation to minimize ASB losses include: corn, wheat, oats, soybeans, potatoes, and birdsfoot trefoil.

The annual ASB emergence occurs about the time the shadbush (Amelanchier sp., aka Juneberry, Serviceberry) blooms. When adults emerge they tend to migrate in mass numbers often in a northeast or northwest direction searching for greener alfalfa fields. Once in a suitable location they feed on new alfalfa shoots and lay eggs that hatch into the voracious root feeding larvae. Under the right conditions ASB migrations can be quite impressive with thousands of beetles seen marching along roadsides from point A to point B. On cooler days, however, the marches go on but are more sporadic, with less numbers of beetles at any one time. Such was the case at a location in Jefferson county last Friday. A slow but steady stream of beetle movement...

Alfalfa snout beetles (ASB) are root-feeding weevils found only in northern New York State along Lake Ontario and the St. Lawrence (Clinton to Cayuga), southern Ontario's Wolfe Island and Grenville and Leeds counties, and in central Europe.

ASB's are mottled gray, humpbacked, 1/2 inch long, do not fly, and are all females.

File written by Adobe Photoshop® 4.0File written by Adobe Photoshop® 4.0

Much larger than alfalfa weevil, alfalfa snout beetles can totally destroy an alfalfa field in as little as one year. Larvae are legless, white, 1/2 inch long, and can be found feeding on alfalfa roots within a foot of the soil surface in mid to late summer. Larvae feed on side roots, and girdle the main taproot causing death to the plant. In early fall the larvae move deeper in the soil where they spend the winter. The following spring the larvae move 10-12 inches from the surface, pupate by mid-summer and become inactive adults, which remain in the soil until the following spring. ASB damage in the spring looks similar to winter killed alfalfa with plants failing to "green up".

Insecticides are not recommended to control ASB, however, two possible avenues of management are currently being researched to control this pest in the future: resistant alfalfa varieties (Don Viands and Cornell's Plant Breeding Forage Group) and biological control using entomopathogenic nematodes (Elson Shields and Graduate Students in Cornell's Entomology Department).

When do weeds wake up in the spring?

Ken Wise, NYS IPM

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It is a good idea to know when certain weeds wakeup in the spring! Knowing when weed species germinate or break dormancy helps to select and time management programs that are the most effective. Weed emergence can be anticipated by considering their response to growing degree-day accumulation (48F Base Temp.) The following chart lists some of common weed species and the accumulated GDD's at which their first flush (i.e. 10%) can be expected to emerge. There are, of course, other factors that affect weed emergence such as cloud cover, soil type, soil moisture, crop residue, and crop rotation.

Group 0(Emergence occurs in fall or early spring)
Winter annuals normally complete emergence prior to planting of corn.
Examples: horsetails (mares tail), white cockle, field penny cress, shepherd's purse

Group 1(Emergence begins several weeks prior to corn planting, GDD <150)
Examples: giant ragweed, lambsquarters, Penn. Smartweed, common sunflower

Group 2(Emergence begins soon, before or at corn planting, GDD 150-300)
Examples: common ragweed, green foxtail, velvetleaf

Group 3(Emergence begins at the end of corn planting season, GDD 250-400)
Examples: yellow foxtail, black nightshade, common cocklebur, wild proso millet

Group 4(Emergence begins after corn emergence, GDD 350 >)
Examples: large crabgrass, fall panicum, waterhemp, morning glory species

Source: Iowa State University Extension Publication, IPM 64

Seed Decay and Seedling Diseases of Corn

Julie Stavisky, NYS IPM & Ken Wise, NYS IPM

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Corn planting is starting, so disease pests that affect emerging seedlings are not far behind. Early season corn seed and seedling diseases can reduce plant populations, and corn does not compensate for gaps in the stand like other crops are able to. Stunting of early plant growth resulting from non-lethal seedling diseases can lead to slower maturity and a decrease in overall plant size.

Seed Decay
Seed decay is caused by a number of soil-inhabiting fungi such as Pythium, Fusarium, Diplodia, Rhizoctonia and Penicillium. These fungi can infect seed before it germinates, causing mortality. Seeds infected with decay fungi are discolored and soft. Many times fungal material may grow on the seed. If you are digging around in the soil to investigate those gaps in the row, a seed that has rotted may be completely decomposed and therefore cannot be found. This can make tracking down the culprit a little difficult!

Seedling Blight
Sometimes the seed may germinate and grow but will die as the plant emerges from the soil. Seeding blights are caused by many of the same fungi that cause seed decay. Seedling blight symptoms include discolored seedling coleoptiles and roots. Seedlings may have a wet, rotted appearance before they reach the soil surface. Above ground symptoms of blight may include seedlings that turn yellow, wilt and die.

Factors that contribute to both seed decay and seedling blights may include cold, wet soils. These unfavorable conditions can lead to slow emergence and slow growth of seedlings. Plant or seed injury from fertilizer burn, incorrect herbicide application, or soil crusting can add to plant stress at the vulnerable seedling stage. Fortunately, planting high quality corn seed is common practice, and fungicide seed treatments are a normal part of the spring routine for many producers. These practices prevent many outbreaks of seed decay and seedling blight.

For more information on early season disease management see: our brochure on Field Corn Diseases.

Alfalfa Crown Rot

Ken Wise, NYS IPM

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While walking alfalfa fields at SUNY Cobleskill this week I discovered many plants that had frost heaved out of the ground. I cut open the tap root and most of the plants showed signs of rot in the crown. Crown rot normally occurs in older fields where there has been a history of stress, heavy traffic or grazing, poor drainage, fertility and pH problems, previous insect damage, etc. Plants exhibiting crown rot appear stunted and have few stems. Crown rot progresses slowly in the crown and taproot area of the plant. In many situations, crown rot cannot be attributed to a single pathogen. Several fungi (Fusarium spp., Phoma, Pythium, Rhizoctonia) as well as some bacteria, have been implicated in the disease. Often, a complex consisting of several of the pathogens attacks the plant. The way to tell if a plant has the disease is to dig up (not pull up) a plant showing symptoms. Then use a knife to split open the crowns and roots. Healthy tissue should be white, moist, and firm. Rotted tissue usually has a black or brownish- red color, but the color may vary from yellowish to pinkish or gray. For more information on alfalfa wilts and rots check out our online publication: Alfalfa Rots and Wilts

Stagonospora nodorum blotch- Small Grains

Ken Wise, NYS IPM

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At the Cornell Research Farm in Valatie, I discovered stagonospora nodorum blotch on the lower leaves in Tom Kilcer’s triticale plots. Splashing rain or thunderstorms can move spores from field surface to the plant wheat seed can be contaminated from spores when it is harvested. This disease may also be in the residue on the surface of the field. Greatest yield losses occur when the flag leaf and the next two lower leaves become infected by the time the wheat flowers in late May. Symptoms usually appear within two or three weeks of head emergence. Leaf lesions begin as very dark brown flecks or spots, sometimes with a yellow halo. These small irregular lesions expand into oval light brown lesions with dark brown centers. On wheat heads the lesions begin as either grayish or brownish spots on the chaff, usually on the upper third of the glume. As lesions enlarge, they become dark brown and the centers turn grayish-white in color as tiny brown or black dots (pycnidia) develop within them.

File written by Adobe Photoshop® 4.0

Growing Degree Days in NYS

Keith Waldron, NYS IPM

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Accumulated Growing degree days (48F Base)

March 1 -  May 1, 2005

Batavia: 70.9
Chazy: 31.2
Clifton Park: 130.1
Geneva: 81.4
Ithaca: 67.3
Mexico: 44.1
Prattsburg: 50.1

Why did the Dandelions get into the Alfalfa Field?

Ken Wise, NYS IPM

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When walking alfalfa fields at the SUNY Cobleskill Farm this week I came across many dandelions. If you think about this, every place that a dandelion was growing was one less place for an alfalfa plant. The obvious consequence is a loss of yield and hay quality potential. The bigger question is why? There are many potential reasons weeds may encroach into alfalfa. Many times it is an older alfalfa field that is slowly declining and allowing space for other weeds to grow. An old stand? Disease or insect pressure? Harvest Interval? Compaction? Fertility or pH? In the SUNY Farm fields mentioned above there appeared to be a lot of frost heaving and root & crown rot. This creates open space for dandelions and other weeds to successfully establish.

Clipboard Checklist

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General:

Update field records: variety, planting date/rate, pesticides used, nutrient inputs including manure, other important field observations, etc.

Note wet spots in field for future drainage.

Pest Monitoring Priorities:

Alfalfa:

alfalfa weevil, alfalfa snout beetle, weeds, crown rot

Small Grain Cereals:

Winter Wheat: Cereal leaf beetle, virus diseases, weeds

Spring Grains: Cereal leaf beetle, seedling diseases, weeds

Field Corn:

Weeds, damping off / seedling blights, seed corn maggot

Upcoming Events:

Grass harvest start by May 15 (NY)

Corn planting finish by May 15, if soil conditions allow

Contact Information

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Julie Stavisky: 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