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Weekly Field Crops Pest Report 2011

August 5, 2011, Volume 10 Number 14

  1. View from the Field
  2. Weather Outlook
  3. Scouting for soybean aphids
  4. Western Bean Cutworm Update
  5. Clipboard Checklist
  6. Contact Information

View from the Field

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Potato leafhopper (PLH) is increasing in population levels on alfalfa in Sullivan County reports Patricia Westenbroek. With many fields under drought stress PLH can increase very quickly to damaging levels. Make sure to monitor alfalfa fields for PLH each week until the first frost in the fall. To review how to monitor see our previous issue on scouting for potato leafhopper in alfalfa.
 
Western bean cutworm (WBCW) catches state wide this week were the highest caught this season. See Keith Waldron's WBCW update below.
 
When soybeans are under drought conditions spider mites can be a problem. Make sure when you are scouting soybean aphids look for spider mite damage. See the article from last week's pest report on spider mites in soybeans.
 
Soybean aphids (SBA) remain low so far this season. However, you will still want to keep a close eye on this pest because moderate temperatures in the mid 70's are conducive to population growth. Drought stressed soybean plants are more sensitive to aphid feeding. Field scouts are starting to find winged forms of soybean aphids in the fields. SBA populations on plants at R6 (full size seed in top 4 nodes) or beyond do not typically reduce soybean yield.

Weather Outlook

August 4, 2011

Jessica Rennells, Northeast Region Climate Center, Cornell University

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Temperatures were 0 to 6 degrees above normal this past week.  Precipitation ranged from a tenth of an inch up to two inches.  The base 50 growing degree days ranged from 100 to 175.
 
High pressure will bring dry weather later today with highs in the mid 70's and low 80's.  Tonight temperatures will be in the 50's.
 
Friday will be sunny with temperatures in the 80's.  There is a chance of some afternoon showers and thunderstorms.  Lows will be in the upper 50's and throughout the 60's.
 
Saturday highs will be in the upper 70's into the mid 80's with showers and thunderstorms.  Lows will be in the mid 60's to low 70's.
 
Sunday will be in the low to mid 80's with a chance for showers and thunderstorms.  Overnight temperatures will be throughout the 50's to mid 60's.
 
Monday temperatures will be in the upper 70's and low 80's with a chance of showers.  Lows will be in the mid to upper 60's.
 
Tuesday's highs will be in the upper 70's and low 80's with a slight chance for showers and thunderstorms.  Lows will be in the upper 50's and low 60's.
 
Wednesday's highs will be in the mid 70's to low 80's with showers and thunderstorms possible.  Lows will be in the upper 50's and low 60's.

The five day precipitation amounts will range from a quarter of an inch to one and a half inches.  The 8-14 day outlook is showing normal temperatures and above normal precipitation for the western and northern edges of the state. 

Scouting for soybean aphids

Keith Waldron
NYS IPM

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While soybean aphids remain low, relatively cooler temperatures (72 -77 F) are conducive to population growth on soybeans. Recently winged forms of soybean aphids have been found in fields indicating possible movement and redistribution of local populations and the mid season emigration of aphids from outside NY on weather fronts. You will want to continue to monitor and scout fields weekly.
 
The 250 SBA / plant action threshold is based on an average of aphids per plant over 20-30 plants sampled throughout the field. Regular field visits are required to determine if aphid populations are increasing. Midwestern research has found that treating earlier than this threshold in most cases does not pay for itself.  But if you have aphids at flowering, the SBA population is increasing compared to the previous weeks count, no or insufficient numbers of natural enemies are present, or other limiting factors are present such as drought, the treatment of SBA may be warranted. Yield loss is due to pod abortion and once pods are gone, there is no recovery of yield other than getting seed a bit bigger. This recommendation has held up well over the past 5 years.
 
When scouting fields for soybean aphid, it is just as important to watch for the aphid's natural enemies, including ladybugs, syrphid fly larvae, parasitic wasps, and fungal pathogens. How many SBA's are present? What's 60 or 250 SBA per leaflet look like? Count, estimate and perhaps check out the "Visual Guide For Soybean Aphid Scouting" brochure developed by the U. of WI. (http://www.planthealth.info/pdf_docs/aphid_visual.pdf)  Remember the SBA threshold guideline is 250 SBA's per plant.

In replicated research trials, this threshold has worked well in R1 (beginning bloom, first flower) to R5 (1/8" seed in top 4 nodes) soybeans. Spraying at R6 (full size seed in top 4 nodes) or beyond has not been documented to increase yield. This threshold incorporates an approximate 7-day lead-time between scouting and treatment to make spray arrangements or handle weather delays. If natural enemies were present, it is also suggested recheck fields for aphid numbers to see if the population has been sufficiently reduced by natural enemies.

The USDA recommends the following protocol to monitor soybean aphids.

  1. Select 20 plants at random, each from a different location (not consecutive down the row) so that the 20 plant-sample is representative of the entire plot.  Identify the growth stage of 5 of the 20 plants.
  2. Examine the entire plant beginning with the growing point (newest trifoliate) for soybean aphids.  If plants are in vegetative growth (no pods or flowers) generally only the growing point needs to be examined.  As flowering and pod set occur, examine the entire plant, including pods.  Spend no more than 30 sec to examine an individual plant.
  3. Count aphids per plant when they are below 250 and estimate aphid density when aphid numbers exceed 250. Apterous (wingless) aphids are assumed to be present. Note whether alate (winged) aphids were also observed. Notes could also be used to indicate if any predators or parasitized aphids (mummies) are present or other such noteworthy observations on crop growth and field condition.

Western Bean Cutworm Update

Keith Waldron
NYS IPM

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Total Western Bean Cutworm (WBC) counts have risen substantially in the past week. From 66 traps reporting from 37 counties: total WBC counts for the week of 6/14, 6/21 were 0; 6/28, 7/5 were 2; 7/12 were 13; 7/19 were 76; 7/26 were 32; 8/2 were 522. Topping the charts was a one week total catch in Attica of 92 moths in a dry bean field.  This may be the week of our peak WBC flight.

Our running total for the season for all traps is 922 WBC moths caught. Accumulated trap counts range from 0 to 125, averaging about 14 moths.
Dan Mongeau (Pioneer Seeds) reports WBC moths were also collected in Vermont, Maine and Massachusetts for the first time in the past two weeks.  
In NY is interesting to see how widespread the moths are being caught.
Also you will again note that moths are not being caught in every location or county.

Some background info:
WBC traps are catching Male moths. There is not a good relationship between # of moths caught and the need to spray. However... The numbers of WBC captures does give us an idea of when to time going into the field to look for WBC egg masses. Suggested timing for field corn scouting (coming from info from Ontario and Michigan) is as the catch numbers approach an accumulation of 100 moths in the trap over time. Dry bean scouting may be more conservative. So… If you are in corn (especially pretassel) or dry bean (especially early pod fill) fields near a trap location with a higher WBC count it may be worth taking a quick look for in the adjacent corn field for WBC egg masses or signs of feeding injury. If a corn field adjacent to a dry bean field is at or above the 5% of plants with egg mass threshold guideline, the dry bean field should be monitored for signs of larval feeding on blossoms or pods.

Western bean cutworm females are most attracted to late whorl/early (pre) tassel stage corn.  They lay masses of 50-200 eggs on the top surface of a leaf near the tassel.  Eggs are round, cantaloupe shaped – white when first laid and turn purple before hatching. Eggs may hatch in as few as 6 days under the right environmental conditions. Expect larvae to be found in fields about 1 – 2 weeks after peak flight. The next few weeks will be important for controlling western bean cutworm in any fields in the attractive stage.
 
Monitoring in field and sweet corn: search tassel-emergence and silk stage fields for western bean cutworm eggs and larvae.  The threshold for WBC being used in Michigan and Ontario is 5% of plants with WBC egg masses. As with European Corn Borer, it's important to control western bean cutworm before it enters the ear and is protected from an insecticide application.  

Monitoring – from Tracey Baute's (OMAFRA) "Bug Blog": "Focus scouting efforts to corn fields that have plants with at least a tassel developing in the whorl of the plant to those fields with the tassel fully emerged but not fully shedding yet. These are the fields that seem to be the most attractive for the moths.  And if fields have variable plant heights, there tends to be a higher concentration of eggs on shorter corn in a field first before moving deep in."

WBC scouting in dry beans can be difficult. Egg masses are laid on the underside of leaves and larvae can be very difficult to find – the larvae feed at night and hide in the soil during the day. Ontario and Michigan researchers have found that pod feeding may begin to occur 1 week to 20 days after peak moth flight. If you don't have traps directly in your own field, at least get an idea of when traps in your area have reached peak moth flight.

We have not yet heard of any fields with WBC egg masses, larvae or feeding injury. Anyone out there finding any?

See:

NYS Sweet Corn Pheromone Trap Network Report, WNY trap catches and information on sweet corn pest management

Penn State Pest Watch Regional Map Average Daily Catch of WBC

Clipboard Checklist

Keith Waldron
NYS IPM

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General
* Emergency contact information ("911", local hospital, Chem. Spill emergency contact, other?) posted in central posting area
* Maintain crop records by field, including variety, planting date, pesticides used, nutrient inputs including manure, etc.
* Watch for any patches of herbicide resistant weeds, weed escapes
* Storage areas cleaned and ready to accept hay, wheat harvest
 
Corn:
* Monitor fields for plant vigor, growth stage, R stage pest issues (corn rootworm, European corn borer, armyworm, western bean cutworm, foliar diseases, nutritional deficiencies)
* Check no-till fields/fields with high residue or weeds for slug/snail damage
* Monitor for weeds, note presence of "who", "how many" and "where"
* Monitor tasselling corn fields for presence of corn rootworm beetles.
 
Small Grains:
* Monitor spring grains for harvest potential
* Grain bins ready to accept upcoming harvest? (See Storage Section)
 
Alfalfa & Hay:
* Monitor alfalfa seedings for weeds, insects & diseases.
* Check regrowth of established alfalfa stands for potato leafhopper, weed and disease problems.
* Storage areas cleaned and ready to accept incoming harvest

Soybeans:
* Evaluate stand growth, development and condition
* Monitor fields for soybean aphid, foliar diseases, white mold, natural enemies, weed escapes
 
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 water sources, drainage, roof gutters for leaks and potential overspill
* Continue fly monitoring: install "3X5" index card fly speck monitoring cards throughout barn
* Install/refresh/replenish as needed: fly tapes, insecticide baits, natural enemies (parasitoids
 
Dairy Livestock Pasture Fly Management:
* Monitor animals for presence of pasture fly pests. Treatment guidelines: Horn flies (50 per dairy animal side, 100 per side for beef cattle), face flies (10 per animal face), stable flies (10 per 4 legs). See: http://nysipm.cornell.edu/livestock/default.asp)
* Consider installing biting fly traps to reduce horse, deer and stable fly populations.
 
Storage:
* Keep areas around storage bins and silos clean and mowed
* Check areas around storage bins and silos for vertebrate tunneling
* Check temperature of recently filled stored grain bins and baled hay

Equipment:
* Note any repairs needed for recently used equipment: tractors, tillage implements, planters, sprayers, etc. as they are cleaned and serviced.
* Service hay harvesting equipment as needed.
* Calibrate manure spreaders - maintain records on amount spread per field



PESTICIDE EMERGENCY NUMBERS

Emergency responder information on pesticide spills and accidents CHEMTREC:  800-424-9300

For pesticide information:

National Pesticide Information Center: 800-858-7378

To Report Oil and Hazardous Material Spills in New York State: NYS Department of Environmental Conservation Spill Response: 800-457-7362 (in NYS); 518-457-7362 (outside NYS)

Poison Control Centers: Poison Control Centers nationwide: 800-222-1222

If you are unable to reach a Poison Control Center or obtain the information your doctor needs, the office of the NYS Pesticide Coordinator at Cornell University, 607-255-1866, may be able to assist you in obtaining such information.

Contact Information


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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