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Weekly Field Crops Pest Report 2012

May 3, 2012, Volume 11 Number 3

  1. View from the Field
  2. Weather Outlook
  3. Why do Weeds get into the Alfalfa or Clover Fields?
  4. What fields are at risk for Black Cutworm or True Armyworm?
  5. When do I need to use a foliar fungicide on my wheat?
  6. Fusarium Head Blight Update for New York
  7. Growing Degree Days
  8. Clipboard Checklist
  9. Mark Your Calendars
  10. Contact Information

View from the Field

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This week while scouting the Cornell Research Farm in Valatie I found a lot of 1st and second instar larvae. This is a little strange that the growing degree days for alfalfa weevil in the region are at 280. According to the degree days most of them should just be hatching from the eggs now.  This does not account for in the field micro-climates and field to field differences. Tip feeding was at 5 to 15% which is still below threshold. See article below on how to scout for alfalfa weevil.

alfalfa weevil larvae

There were also several clover plants that had died over the last few weeks. I cut open the tap root to discover they had root rot. There were several species of winter annual weeds present in alfalfa and clover.

Weather Outlook

May 3, 2012
Jessica Rennells, Northeast Region Climate Center, Cornell University

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Last week temperatures were below normal for the whole state, most of the state had temperatures 3 to 9 degrees below normal.  Precipitation amounts ranged from just .01 up to an inch.  The base 50 growing degree-days were again low, less than 25 for the state. 

Today we’ll have a chance for scattered showers and thunderstorms, none are expected to be severe.  Temperatures will range from near 70’s in eastern NY to low 80’s in western NY.  Overnight temperatures will be warm in the upper 50’s to low 60’s with increasing chances for showers and thunderstorms.

Friday will be in the mid 70’s to low 80’s with continued chances for showers and thunderstorms, with the possibility for some severe storms with gusty winds.  Lows will be in the mid to upper 50’s with the possibility for showers.

Saturday’s temperatures will cool to the upper 60’s and low 70’s with just a slight chance for scattered showers.  Overnight temperatures will be throughout the 50’s.

Sunday will be mostly sunny with temperatures closer to normal, ranging in the 60’s.  Overnight temperatures will be in the upper 40’s.

Monday will again be sunny with highs in the 60’s.  Lows will be in the low to mid 40’s.

Tuesday’s temperatures will be in the low to mid 60’s with a chance for some scattered showers.  Overnight temperatures will continue in the 40’s.

Wednesday will again be in the low to mid 60’s with a chance for some scattered showers and lows in the 40’s.

The five-day precipitation amounts will range from three quarters of an inch to one and a half inches.  The 8-14 day out look is showing below normal temperatures for the whole state and above normal precipitation just for the eastern edge of the state, mostly the Hudson and ChamplainValleys.

National Weather Service Climate Prediction Service Maps of 8-14 day outlooks

National Weather Service Eastern Region Headquarters watch/warnings map

NRCC Drought Page which features the US Drought Monitor map (updated every Thursday)

Why do Weeds get into the Alfalfa or Clover Fields?

Ken Wise

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When walking alfalfa/clover fields at the Cornell Research Farm in Valatie there were several species of weeds growing in openings that have occurred between the forage. In this case it seems that several of the clover plants had died this year or last year. Some of the clover plants had recently died.

dead clover plant

Dead Clover Plant

After digging them I cut the tap root open to discover root rot. There are a wide range of pathogens that attack the roots of clover and alfalfa.

clover root rot

Root Rot In Clover

There are a few ways they can get into the roots. One is drought stress and could have been the reason they died at Valatie. Earlier in the season the plants were under extreme stress due to the lack of moisture. When a clover or alfalfa is weakened pathogens can take advantage of the plant and enter the root.

The second option is root feeding insects like the larvae of clover root curculio and alfalfa snout beetle. Larval stages of these insects feed on the roots opening them to diseases. Alfalfa snout beetle can also kill the plant from its feeding.  OK… so what does this have to do with weeds? After the plant dies it leaves an open area in the field for weeds to grow. Normally with a good healthy crop the alfalfa and clover can compete with the weeds for space. But once there are openings weed seeds can germinate and fill in the open space as seen in the photo below:

weeds fill in

 If you think about this, every place that a weed is growing is one less place for an alfalfa/clover plant. The obvious consequence is a loss of yield and hay quality potential.

What fields are at risk for Black Cutworm or True Armyworm?

Ken Wise

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There has been a lot of activity with black cutworm and true armyworm moth captures southwest of NY. Indiana is reporting armyworm captures similar to the 2001 infestation. Many of you may remember the year we got HIT with armyworm across the Northeast.  They are also catching a lot of black cutworms in their light traps. On the other hand Penn State has not yet detected a significant flight of black cutworm or true armyworm moths. True Armyworm and Black Cutworm migrate on storms to from the south and southwest north.  In NY we do not have a black cutworm or armyworm detection network. So it is up to producers and area consultants to get out and scout fields. With some of the intense catches in other states and the storms we have gotten it is important to get out in fields. One question to ponder is which fields are at risk?   Both black cutworms and armyworms like similar habitat.

Black cutworm is a generalist feeder and has a large list of host plants including small grains, corn and some vegetables as well as weeds such as bluegrass, curled dock, chickweed, lambsquarters, yellow rocket, and redroot pigweed.

True armyworms are more specialized in their host plant range. They are mostly grass feeders. This includes all small grains, corn, hay fields, pastures and most grassy weeds.

Now the question what fields are at risk?

Small grains like wheat, oats, barley, rye and triticale are all targets for both true armyworm and black cutworm.

Weedy fields of corn. The moths will lay eggs on any of these weedy plants in the field. Once you get out there and spray the weeds they will then crawl to the nearest corn plant and start munching.

No-till fields can be at great risk because they can be weedy early in the season and have a lot of surface residue to hide under during the day. Both armyworm and cutworm are nocturnal feeders.

Fields that are planted to small grains as a cover crop like rye, then burn down with an herbicide and planted to corn can be a prime for supporting armyworm populations.

Grass/alfalfa fields and pasture can be attractive to true armyworms. The armyworms may not feed much on alfalfa, but they will feed on the grasses between the plants.

What to look for in the field is important. You have to look for the larvae. True armyworm larvae appear smooth cylindrical 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. Armyworm photo. It is important to detect armyworm areas 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. Black cutworm larvae vary in color from light gray to black with a pale brown to black head. Larvae have a greasy, shiny appearance with coarse granules present over their body. During the day larvae burrow into the soil next to the corn plant. These larvae curl into a C shape when disturbed. Symptoms of damage occur at night and are leaf feeding, irregular holes in stem, notched and cut or missing plants.

black cutworm and damage

When do I need to use a foliar fungicide on my wheat?

Ken Wise, NYS IPM

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Do you apply fungicide to your wheat each year? Are there really diseases in the field or are you just adding protection? Spraying a fungicide without the knowledge of a fungal disease present and at certain levels is like playing the lottery with 1000 of dollars at once. You DON’T know if there was a problem. You could have saved a lot of money. Plus there is an environmental risk with using fungicides. Remember that fungicides only control fungal diseases. They do not control bacterial or virus borne diseases. Foliar fungicides DO NOT protect from root diseases. The important fungal diseases to consider this time of year are: powdery mildew, rust and Stagonospora nodorum blotch. We will discuss fusarium head blight management in future issues.

The key to managing these foliar fungal diseases are to SCOUT for them. You have to get out of the truck and walk the fields. You will need to assess the upper three leaves for symptoms and signs for the diseases in early to mid-May, before flag leaf emergence.  You will need to assess 20 plants in different areas of the field to get a representative sample of the occurrence of the disease. A representative sample is important because it gives you a better idea of the severity of the disease across the whole field. If assessments are taken in one or two areas you can bias your efforts. Meaning what you sample in the small area might not be what is happening in the rest of the field.

The action threshold is the point at which management actions need to be taken. The action threshold for these diseases is reached if any amount of disease is observed on approximately 50 percent of main tillers. This is the point at which management should be employed… meaning a fungicide is justified.

Next you need to consider the stage of crop development. This will help you decide what family of fungicides should be used.

Crop stage 4-5 (April)
-Tillering Stages
-Half-rate of triazole fungicides. These can be mixed with herbicide

Crop stage 6-10 (Early to Late May)
-Before heading fungicide decision-
-Family of Fungicides: strobilurin, triazole, combination

Crop  Stage 10.1 to 10.5 (Heading)
-Heading to flowering fungicide decision
-Family of Fungicides: triazole

Fusarium Head Blight Update for New York

Gary Bergrstrom, Cornell University Plant Pathology

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Winter wheat development in New York ranges from Feekes growth stage 6 (first node detectable) to stage 8 (flag leaf just visible). Growers are assessing potential freeze damage to their wheat crops resulting from temperatures as low as 19 F 3 weeks ago to more recent cold temperatures as low as 22 F.  Symptoms of soilborne viruses (wheat spindle streak and soilborne wheat mosaic) are obvious now in susceptible varieties, providing a reminder that varieties with resistance should be selected for planting in fall of 2012. Leaf rust which was prevalent on wheat seedlings in certain locations in October 2011 shows no signs of having overwintered locally this year.  Minor levels of powdery mildew have been observed, but relatively little fungal leaf blotch has been observed to date. A decision to apply a foliar fungicide prior to head emergence should be based in large part on detection of powdery mildew, leaf blotches, and/or leaf rust on upper leaves on a majority of tillers. Several fungicides (strobilurin, triazole, or strobilurin plus triazole products)are efficacious and labeled for leaf disease control in New York.  Strobilurin-containing products are not recommended for use on headed wheat because their late application has been associated with elevated levels of the mycotoxin deoxynivalenol (DON).  A critical decision for the majority of wheat producers will be whether to make a single application of triazole fungicide at the onset of flowering, coinciding with the principle infection period for Fusarium head blight.  The triazole fungicides Caramba, Proline, and Prosaro have the greatest efficacy in suppression of Fusarium head blight and reducing the potential for mycotoxin contamination in grain. These materials when applied at flowering will also provide very good control of powdery mildew, rust, and leaf blotches during the critical early grain-filling period.  Growers are urged to consult this Risk Assessment Tool and New York Commentary frequently as a source of information on the regional risk for Fusarium head blight.

Growing Degree Days

Ken Wise, NYS IPM

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CURRENT Accumulated Growing degree days (48F Base):

March 1 - May 2, 2011

Base 48 F
Base 50 F
*Indicates missing data
source: NEWA's Degree Day data page

Clipboard Checklist

Keith Waldron

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*Walk fields to check tile flow, check and clear drainage outlets. Look for line breaks
*Note and record location of wet areas on field maps or aerial photo for future tiling considerations and crop decisions, check for areas of soil erosion
*Maintain crop records by field, including variety, planting date, pesticides used, nutrient inputs including manure, etc.
*Minimize field to field movement of soil and crop debris on equipment, particularly from field with known pest problems such as white mold and Phytophthora.
*Watch for early season weeds: winter annuals, chickweed, henbit, field penny cress, shepherd's purse, giant and common ragweed, purple deadnettle, lambsquarters, redroot pigweed, velvet leaf, Pennsylvania smartweed, common sunflower, quackgrass, foxtail

*Evaluate established legume stands for winter damage (thinning stand, frost heave), determine average alfalfa stand count adjust crop plans if necessary
*Monitor alfalfa for alfalfa weevil
*Monitor new seedings for Pythium blight and Phytopthora Root Rot.
*Monitor alfalfa for Alfalfa Snout Beetle (In Oswego, Jefferson, Cayuga, Wayne, Lewis, St. Lawrence, Clinton, Essex, and Franklin counties)

Small Grains:
*Monitor winter grain fields for over wintering survival, weed issues, check growth stage, number of tillers
*Check stands for soilborne virus diseases, Wheat spindle streak mosaic and Soilborne wheat mosaic and powdery mildew symptoms, cereal leaf beetle, weed escapes, goose damage

*Prepare land and plant corn as soon as conditions allow
*Pre-plant weed evaluation, timing cultivation and/or pre-plant weed management

*Check and mend fences as needed.
*Check crop growth
*Invasive species, plants harmful to livestock
*Review/Plan rotation system

*Remove / clean soil and crop debris from equipment
*Arrange for custom weed control or check your own application or cultivator equipment for repairs.
*Check nozzles, pumps, etc., recalibrate pesticide application equipment before use.
*Carry appropriate / necessary NYS DEC and EPA required documents: (pesticide applicators license, pesticide labels, MSDS sheets, etc.) with application equipment
*Calibrate planting equipment - maintain records on crop planting rate per field
*Calibrate manure spreaders - maintain records on amount spread per field

* Check stored grain bins for temperature, moisture and signs of mold and insects. Aerate, core, transfer grain or treat as necessary

*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

Mark Your Calendars

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CORNELL UNIVERSITY’S SMALL GRAINS MANAGEMENT FIELD DAY, Musgrave Research Farm, 1256 Poplar Ridge Road, Aurora, NY, Thursday June 7, 2012. The Program will run from 10:00am-12:00noon, registration begins at 9:30 am.
An educational program of the Integrated Field Crop, Soil, and Pest Management Program Work Team in conjunction with Cornell Cooperative Extension will be hosting the Small Grains Management Field Day with research demonstrations and presentations of interest to the local farming community.   DEC and CCA credits will be available.  For more information, please contact  Mary McKellar at or 607-255-2177

Contact Information

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Keith Waldron: NYS Livestock and Field Crops IPM Coordinator
Phone: (315) 787 - 2432
Fax: (315) 787-2360

Ken Wise: Eastern NYS IPM Area Educator: Field Crops and Livestock
Phone: (518) 434-1690
Fax: (518) 426-3316