Weekly Field Crops Pest Report 2008
View from the Field
Eastern NYS-Ken Wise
Alfalfa at both the SUNY Cobleskill Farm and the Cornell Research Farm in Valatie were 18 to 20 inches tall. There was a range of 1st to 3rd instar alfalfa weevil larvae at the SUNY Cobleskill farm, while I did not find any larvae at the Valatie research farm. It is a bit odd because the Valatie site is normally ahead of the Cobleskill site in alfalfa weevil development. I did find substantial numbers of adult alfalfa weevil at the research farm. Other insect pests I found were clover root curculio, tarnished plant bug and clover stem weevil. Clover stem weevil (Ischnopterapion virens) is a tiny blue weevil and a pest of clover. This weevil is native to Europe and is relatively new to the
Clover stem weevil
I found symptoms of spring black stem under the canopy of alfalfa at the SUNY Cobleskill farm. This disease is very common to find in alfalfa fields in NYS. Spring black stem is favored by cool and moist weather in early spring. Symptoms appear as irregularly shaped brown to black spots that can merge to form a larger blotch. This disease can infect the petiole, form elongated blackened areas on the stems, and may be a contributor to crown rot.
Tom Kilcers triticale trials looked good this week and there was only a little disease (Septoria tritici or Stagonospora nodorum blotch) on the very lower leaves. I also scouted grass hay fields at the SUNY Cobleskill farm this week looking for possible armyworm larvae since to the south populations have been very high. I did not find any small larvae but will continue to look at these grass hay fields in the weeks to come. Last week, I stated that I would have an article on insect pests of canola. I will have this article prepared for you next week. Sorry about the delay!
Western NYS-Julie Dennis
Mike Stanyard, NWNY Team, reports that powdery mildew in the spore stage is common in wheat fields, even on flag leaves. The disease is not typically uniform throughout fields.
Weather Outlook May 22, 2008
Rainfall was above normal along the Southern Tier, southern
There were fewer than 25 (base 50) GDD days during the period May 15-21 which put the seasonal total in the 100 to 300 range across much of the state. At this point in the growing season the base 50 GDD accumulation is very close to the 30 year average, but lags the accumulation we saw at this time last year by as much as a week in the eastern part of the state. The accumulation is slightly ahead of last year in the far west.
Unseasonably cool and showery weather will persist through today. Conditions will improve through the weekend, as the upper level low that has sat over the Northeast finally moves out of the area. A ridge of high pressure will build into the region bringing a return to sunshine and a warming trend by the weekend and into early next week. Clearing on Friday will introduce the potential for frost in some areas Friday night into Saturday morning. Temperatures will warm up to above normal by Monday, with highs on Monday exceeding 80 in parts of the state. A cold front is expected to traverse the state Monday evening into Tuesday with a chance of showers and a cool down. High pressure will build again for Tuesday and Wednesday bringing near normal temperatures (highs in the 70s lows in the low 50s).
The longer term outlook (next Wednesday through June 3) is for near or slightly below normal temperatures and below normal precipitation.
Alfalfa Weevil Management: Beneficial Insects Are On Our Side
Alfalfa weevil larvae have been seen in several locations over the past couple of weeks, but widespread damage is not being reported yet. Biological control agents are a significant reason that alfalfa weevil (AW) often remains well below economic thresholds in NY.
Within 10 years of the arrival of the invasive alfalfa weevil in the
While searching for alfalfa weevil pupae later this month or in early June, keep your eyes out for the parasitoid pupae, too. Alfalfa weevil pupae can be found inside small net-like, pea-sized cocoons generally found in lower regions of the plant on or 2-3 inches above the soil surface. The alfalfa weevil pupa is surrounded in a white to tan webbing, often associated with a leaf, and a wasp pupa is instead surrounded by a small hard brown capsule-shaped pupal case (see photos). Enclosed in the brown case is the wasp pupa, which has grown up using the alfalfa weevil larva as its food source.
Alfalfa weevil pupae
Pupae (within their cocoons) of parasitic wasps of Alfalfa Weevil
The two most common parasitic wasps of AW in NY are in the genus Bathyplectes. Their pupae are enclosed within the mahogany colored shells, or cocoons, with white bands (2nd and 3rd from the left in the above photograph). These two parasitoid species tend to lay eggs in the early alfalfa weevil larval stages. Only a single parasitoid can successfully develop in a host weevil larva. The two species can be distinguished from each other as pupae. Batheplectes anurus has a raised white band and the cocoon has the unusual habit of jumping when disturbed. B. curculionis does not have a raised white band, and the cocoons do not jump.
Dont forget to review the NY alfalfa weevil scouting guidelines in our online publication: Alfalfa Weevil Management Guide
Reports of High Levels of Armyworm Infestations to the South
There have been reports of very high levels of true armyworm in the
True armyworm larvae appear smooth, cylindrical, and pale green to brownish when they are still small. Mature larvae are smooth and marked with two orange, white-bordered strips on each side. True armyworm ranges in size from 1/8 inch to 1.5 inches long. There is a website with a photo of armyworm: Armyworm photo
It is important to detect areas of armyworm infestation early, while larvae are still small, since large larvae do most of the feeding and quickly destroy whole stands of corn, grasses and small grains. Because armyworm feeds at night look for chewed leaves, cut stems, lodged plants, pellet-like frass on the ground, and larvae hidden under plant canopy and surface residue. You will need to be aware that armyworms can move from field to field very quickly. Start scouting for the armyworms in May and repeat scouting every 3 days to 5 days. Monitor fields for armyworm larvae when they are less than 1/2 inch long. If there are sufficient numbers and damage is present, an insecticide could be justified. Treat only the affected area and a 20 to 40-foot border around the infestation. Rarely does a whole field need to be treated for armyworm. Larger armyworm larvae, greater than 1/2 inch long, are much more difficult to control. These large larvae are more tolerant of insecticides, reducing the effectiveness and economic viability of this option.
Will Conditions be Favorable for Fusarium Head Blight (Scab) This Year?
One of the most devastating diseases of wheat is Fusarium head blight, or scab. The disease reduces yield by decreasing the number of viable kernels, but the more significant impact is that the fungus in diseased kernels may produce DON, a mycotoxin called deoxynivalenol (DON). DON is sometimes called vomitoxin because of the impact on the digestive system of swine and other animals with simple stomachs. The rejection of infected grain by buyers is the most significant cause for wheat losses to Fusarium head blight.
Scab is caused by airborne spores of the fungus Fusarium graminearum that dwell in nearby or distant crop debris, including corn stalks and wheat straw. This is the same fungus that can cause root, stalk, and ear rots of corn. Since the fungus is very widespread, likelihood of exposure is not reduced sufficiently by crop rotation or other cultural practices. Extended periods of warm, moist weather at crop flowering can cause the florets to be infected just after anther emergence, killing the florets and preventing kernels from developing. Symptoms of scab become visible on emerged heads within weeks after flowering. During early grain fill, the disease shows up as pink to salmon orange on infected kernels. As kernel fill progresses, the infected kernels appear bleached.
There is a valuable predictive tool available online at the Fusarium Head Blight Risk Assessment Tool.
Gary Bergstrom tells us that this model mainly predicts the likelihood of spore build-up based on temperatures and rainfall amounts prior to wheat flowering. Using the new 24-48 hour forecast weather feature of the model, one can also get an idea of the favorability for actual infection. It shows us a ball-park of areas to focus our scouting efforts. Unfortunately, the model does not accurately predict the level of toxin contamination in grain, particularly if there is a sustained rainy spell during grain-fill.
New in our arsenal this season is the availability of Tilt fungicide that provides fair control of scab. Please refer to the table in the article at this link for specific recommendations on wheat fungicides: Wheat Fungicides Options for 2008.
It is important to note that strobilurin fungicides have actually been shown to increase vomitoxin occurrence when applied at heading!
Plant pathologists and plant breeders continue the active development of varieties resistant to Fusarium head blight. Newly released this year is the Cornell variety called Jensen, developed by Mark Sorrells, Cornell Department of Plant Breeding. Jensen has shown more resistance to fusarium head blight (scab) than other white wheat varieties typically planted in NY.
Growing Degree Days and Alfalfa Weevil Development in NYS
March 1 - May 20, 2008
*Indicates missing data
Degree Days for Peak (50%) Occurrence of Alfalfa Weevil Stages
Soybean Rust Status
No new detections of soybean rust have occurred in the
Rust continues to be found in the southern U.S. Active disease is still being reported on kudzu in six counties in
Coordination of soybean rust sentinel plots in
More information on soybean rust can be found at the national soybean rust website.
Emergency contact information (911, local hospital, Chem. Spill emergency contact, other?) posted in central posting area
Review EPA Worker Protection Standard training and posting compliance needs
Maintain crop records by field, including variety, planting date, pesticides used, nutrient inputs including manure, etc.
Watch for winter annual and other early season weeds, any patches of herbicide resistant weeds?
Storage areas cleaned and ready to accept upcoming hay harvest?
Determine plant populations, make notes on emergence problems
Gaps in row? Check for seed corn maggot, wireworm, cutworm, armyworm, seedling blights, birds, seed placement issues
Check no-till fields/fields with high residue or weeds for slug damage
Monitor for weeds, note presence of who, how many and where
Adjust post emergence weed control actions
Monitor winter grains for crop stage (flag leaf?), insect (cereal leaf beetle, armyworm) and disease problems
Check wheat for powdery mildew and soil borne wheat mosaic virus (susceptible varieties such as Harus and Jensen)
Evaluate crop for adequate stand and plant vigor
Alfalfa & Hay:
Monitor alfalfa seedings for weeds, insects & diseases.
Check established alfalfa stands for alfalfa weevil, weed and disease problems.
Timothy stands: check fields for symptoms of cereal rust mite
Storage areas cleaned and ready to accept upcoming harvest?
Field preparations, planter ready, Rhizobium inoculum?
Evaluate stand emergence seedling blights, seed corn maggot, weed assessment
Dairy Livestock Barn Fly Management:
Sanitation, sanitation, sanitation clean animal resting areas, feed troughs, minimize source of moist organic matter i.e. fly breeding areas in barn and in adjacent animal loafing yard
Check waterers, drainage, roof gutters for leaks and potential overspill
Begin fly monitoring: install 3X5 index card fly speck monitoring cards through out barn
Order fly management materials: fly tapes, insecticide baits, natural enemies (parasitoids)
Check storage areas (bunk silos, etc.) for readiness to accept first cutting
Check forage allocation and anticipate feed program adjustments as forages are used up from previous year
Plan where forages should be stored for optimum allocation for feeding
Keep areas around storage bins and silos clean and mowed
Note any repairs needed for recently used equipment: tractors, tillage implements, planters, etc. as they are cleaned and serviced.
Service corn planter as needed. alfalfa harvesting equipment, and tillage implements
Soybean planter and alfalfa harvesting equipment ready?
Calibrate manure spreaders - maintain records on amount spread per field
PESTICIDE EMERGENCY NUMBERS
Small Grains Field Day
*June 5, 2008
Robert B. Musgrave Research Farm
Corn and Alfalfa Field Day
*June 18 at 12:30pm 3:30pm
At the SUNY Cobleskill Farm
Seed Growers Field Day
*Tuesday July 8
NYSIP Foundation Seed Barn
Weed Science Field Days
*Wednesday, July 9, 2008
Valatie Research Farm
9:30 am - Noon
*Wednesday, July 16, 2008
Robert B. Musgrave Research Farm
1:30 pm - 5 pm
Wednesday, July 23, 2008
Robert B. Musgrave Research Farm
Julie Dennis: IPM Area Educator, Livestock and Field Crops,
Keith Waldron: NYS Livestock and Field Crops IPM Coordinator