Weekly Field Crops Pest Report 2006

View From The Field

Ken Wise, NYS IPM

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There were many pests to see at the Cornell University Research Farm in Valatie this week including alfalfa weevil, clover-root curculio adults on alfalfa and Stagonospora nodorum blotch on triticale. Oh yes, a few weeds emerging too.

Clover-root curculio adult weevils can often be found cruising alfalfa this time of year. Adults nip at leaves and their below the ground feeding grub-like larvae feed on root nodules and damage alfalfa roots, which can predispose plants to infection by root diseases.

Unfortunately, there is not much we can currently do to manage this insect with the expectation of rotating a different crop. This pest builds in population in a field over time. These small weevils are 1/8 inch long and 1/16 inch wide with short, broad snouts. The adult weevil is brownish-black and covered with grayish hair and scales. Adult curculios chew the margins of leaves leaving C shaped notches. Clover-root curculio larvae feed below-ground on nodules, small rootlets, and chew out portions of the main root. As a result of larval feeding on roots, diseases such as fusarium crown and root rot can enter the plant. Clover-root curculio will feed on several types of clover and alfalfa.

I discovered Stagonospora nodorum blotch on the lower leaves of triticale in Tom Kilcer’s research plots. Splashing rain or thunderstorms can move spores from field surface on to the plant. This fungal pathogen may also reside in residue on the field surface. In wheat, 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. 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. 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.

Cornell Pest Management Guidelines On-line

Keith Waldron, NYS IPM

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Looking for Cornell Pest Management Guidelines on-line? See http://ipmguidelines.org/ for your one stop Cornell guidelines information connection. This website has links to all Cornell Pest Management Guidelines On-Line including: Berry Crops, Field Crops, Floral and Greenhouse Crops, Grapes, Herbaceous Perennials, Livestock, Pests Around the Home, Tree Fruit, Trees and Shrubs, Vegetable Crops and Wildlife Damage Management.

Cornell Guide to Integrated Field Crop Management: WWW.fieldcrops.org.

Watch for Virus Diseases of Winter Wheat

Julie Stavisky, NYS IPM

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With the warm, dry conditions last week, then the weekend rain storms, winter wheat stands are vigorously growing. But with our cool late April weather, this is the prime time to monitor fields for wheat spindle streak mosaic virus and yellow dwarf.

Wheat spindle streak mosaic virus (WSSMV) symptoms are yellow-green dashes or streaks with tapered ends, running parallel to the leaf veins. A soilborne fungus that attacks the roots of wheat in the fall transmits WSSMV. Symptoms often show up on plants in wet soils, but excessive moisture in the spring is not required for infection to occur. Cool spring temperatures like we are now experiencing are ideal for continued development of WSSMV. As temperatures warm, plants usually outgrow the disease. Click here to see photos of WSSMV

Yellow dwarf symptoms include yellowing of leaf tips, sometimes progressing to red or purple colors. Several species of aphids common in New York transmit yellow dwarf. If winter wheat was planted too early in the fall, aphids may have had time to infest and infect plants. If yellow dwarf infections occur in the spring, instead, symptoms will appear later. Stay tuned to the Pest Report for updates. Photos of symptoms can be seen atYellow dwarf affecting a whole field and Yellow dwarf: healthy vs. diseased plant

Rescue treatment options to eliminate infections from viral disease are not available. Fortunately, severe outbreaks of viral diseases are uncommon in wheat in NY since resistance is present in most of the commonly grown cultivars. However, scouting now for these diseases, and submitting suspicious samples for correct identification to the Cornell Plant Disease Diagnostic Clinic (http://plantclinic.cornell.edu/) has the value of verifying the presence of these diseases. Next time wheat is planted in the same field, preventative management, such as planting a resistant cultivar, becomes an easy choice.

Alfalfa Weevil Creeps into Fields-Alfalfa

Ken Wise, NYS IPM

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This week I discovered a few adults, eggs and 1st instar alfalfa weevil larvae at the Cornell University Research Farm in Valatie. There was only about 5% tip feeding in each field. Newly hatched larvae are about 1/16 inches long and yellow to light green in color. As larvae feed, grow and molt they become green with white stripes down their back. Larvae have a dark brown head. Larvae ultimately grow to reach 3/8 inches long before pupation about early June in New York. Recall that these larger larvae have big appetites and are responsible for 80% of the alfalfa lost to weevil feeding. Check out these websites for correct identification: Alfalfa Weevil Eggs and Alfalfa Weevil Larvae. Check out our on-line publication, IPM for Alfalfa Weevil.

Remember the base temperature for alfalfa weevil is 48F to determine developmental growth stage.

Accumulated Growing Degree Days for March 1 to April 25

Location	Base 48 F	Base 50 F
Batavia	98	70
Chazy	44	27
Clifton Park	146	110
Geneva	92	63
Ithaca	72	48
Mexico	61	36
Prattsburg	44	24

Winter Annual Weeds Alert

Julie Stavisky, NYS IPM

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Winter annual weeds are popping up in wheat fields and reduced-tillage fields all across our area. Among the most commonly observed so far this spring are henbit, purple deadnettle, common chickweed, and corn chamomile. The wild mustards (including yellow rocket, shepherd’s purse, and wild radish) are also present, but they are still in their rosette stages and thus are not yet catching our attention. Stay tuned to the pest report next week for more information. Winter annuals germinate in the fall, overwinter as seedlings, and flower and go to seed in the spring.

Let’s highlight a couple winter annuals to watch for while scouting:

Corn Chamomile plants are mostly still in the rosette stage. The rosettes are small and low to the ground, with finely divided foliage. The small daisy-like flowers may be seen starting in mid-May. Click here for a photo of corn chamomile

Henbit: The small tubular pink to purple flowers are seen in the upper whorls of leaves. Stems are square, as is typical of the mint family. Lower leaves are heart-shaped, while the upper leaves are deeply lobed.

Purple deadnettle is flowering like crazy after the warm weather last week. This weed also has a square stem and small tubular flowers that appear in the upper whorls of leaves. Leaves are triangular in shape and less deeply lobed than henbit. The upper leaves of purple deadnettle are purple, and the flowers are pale purple. Photos to help you distinguish henbit from purple deadnettle can be seen on this web page from Michigan State University: Henbit vs. Purple Deadnettle

Winter annuals present the most significant pest problem in winter wheat, where the life cycle of the weed matches the life cycle of the crop. Wheat is now actively growing, and the winter annual weeds are competing for nutrients and moisture. If scouting indicates that herbicides are necessary, applications should be made no later than the fully tillered stage of wheat development. More information on weed management options in wheat can be found in the small grains section of the online version of The 2006 Cornell Guide for Integrated Field Crop Management: http://ipmguidelines.org/fieldcrops/5-SmallGrainCrops/5.09Weeds.htm

Alfalfa Snout Beetles on the March: A Dubious Sign of Spring?

Keith Waldron, NYS IPM

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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. Last week Dr. Elson Shields and his entomology crew sounded the call to view alfalfa snout beetles in their annual migration.

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

Alfalfa snout beetles (ASB) typically emerge a few weeks before of our other alfalfa munching beetle, the alfalfa weevil, and are more than twice their size. ASB's are mottled gray, humpbacked, 1/2 inch long, do not fly, and are all females. Adult alfalfa snout beetles leave alfalfa fields this time of year in mass (by the tens of thousands) in search of new alfalfa fields to lay their eggs. Once they find a suitable location ASB’s feed on new alfalfa shoots and lay eggs that hatch into the voracious root feeding larvae. While adult feeding can trim the tops of alfalfa and other hosts, it’s larval feeding, associated root damage, the potential for disease infection and overwintering injury that contribute to the real coup de grace and stand loss. Alfalfa snout beetle 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".

Alfalfa Snout Beetles in your neighborhood? In addition to alfalfa, other host plants for ASB include: red clover, dock, wild carrot, quackgrass, and white clover. ASB control is best achieved with a three year rotation of alfalfa with a row crop. Nonhosts, i.e. good crops to have in rotation to minimize ASB losses include: corn, wheat, oats, soybeans, potatoes, and birdsfoot trefoil. Insecticides are not recommended to control ASB.

Future control options? Cornell researchers are currently looking into two possible avenues of future ASB management: 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). Wish them luck!

Alfalfa snout beetles feeding on bedstraw plants near the edge of an alfalfa field in Jefferson county.

Small Grain Rust Alert

Gary Bergstrom, Cornell University

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The USDA Cereal Rust Bulletin (April 18) reports that wheat leaf rust is prevalent throughout the southern U.S. this spring. Colleagues in Ontario and Pennsylvania have also found locally over-wintered leaf rust. So it would not be surprising if we also find some pockets of over-wintered rust in New York, especially areas that had some snow cover this winter. In the past I have found the large aerial rust showers from the southern areas (often arrive with thunderstorms in June) to dwarf the role of any over-wintered, local inoculum, but it would be good to keep an eye on this.

Wheat stripe rust is at low levels so far in the south, especially in the Mississippi Delta states.

Oat crown rust is at low levels in the south. The alternate host buckthorn is breaking bud now in NYS. Watch for the yellow-orange aeciospore stage on developing buckthorn leaves over the next few weeks - aeciospores will infect nearby oat crops.

Some wheat stem rust has been found in Louisiana.

Soybean Rust Updates

Keith Waldron-NYS IPM

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From USDA Soybean Rust Website: http://www.sbrusa.net/

National Commentary (updated: 04/24/06)

Scouting for soybean rust continues on kudzu patches from Florida northward to southern Illinois, and westward to Texas. Many of the soybean sentinel plots have been planted in most southern and some mid-western states. Soybeans in sentinel plots have emerged as far north as central Illinois. Currently, there are no reports of rust on newly planted soybean in 2006 including volunteer plants. Rust has been confirmed in five counties in Alabama, 11 in Florida, four in Georgia, and one in Texas. No new positive counties have been reported since the first week of March. The south has been dry with some recent rains reported in the southeast including Florida to the north and east. The southwest continues to be dry. View state commentaries for detailed reports of planting and scouting information.

Clipboard Checklist

Keith Waldron-NYS IPM

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General:
* Review EPA Worker Protection Standard training and posting compliance needs
* Walk fields to check tile flow, check and clear drainage outlets.
* 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

Alfalfa and Small Grains:
* Monitor alfalfa for Alfalfa Snout Beetle (In Oswego, Jefferson, Cayuga,Wayne, Lewis, St. Lawrence, Clinton, Essex, and Franklin counties)
* Evaluate established legume stands for winter damage, determine average alfalfa stand count, adjust crop plans if necessary
* Monitor for Alfalfa weevil as weather continues to warm
* Check winter grains for adequate stand and plant vigor, monitor for crop stage, disease, weed and insect problems

Corn:
* Begin/Continue corn planting the last week of April

Pastures:
* Check and mend fences as needed.
* Check crop growth
* Review/Plan rotation system

Storage:
* Plan where forages should be stored for optimum allocation next feeding season

Equipment:
* Check corn planter, calibrate, note any parts or repairs needed
*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 application records

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