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Weekly Field Crops Pest Report 2009

September 03, 2009         Volume 8 Number 19

1. View from the Field

2. Weather Outlook September 2, 2009

3. Two-spotted spider mites in soybeans

4. Alfalfa Snout Beetle in Fall Alfalfa

5. Think Weeds in the Fall!

6. Keeping Pest Records

7. Soybean Rust Update

8. Soybean Aphid Update

9. Clipboard Checklist

10. Contact Information

View from the Field

Ken Wise

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Keith Waldron reports observing soybeans fields in western NY with infestations of two-spotted spider mites. Fields affected had also been treated earlier this season with a pyrethroid insecticide  for control of soybean aphid. Warm weather combined with dry- droughty conditions can increase risk of spider mites becoming a problem in soybeans and field corn. We have relatively few reports of this pest being a problem so far this season but if your fields have been showing drought stress, it would be useful to include monitoring for spider mites in your next field visit.

Weather Outlook September 2, 2009

Jessica Rennells
NOAA Northeast Regional Climate Center, Cornell University

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Temperatures during the last week were below normal for all the state.  Most of the state was 3to 6 degrees below normal. Precipitation ranged from a trace to 3 inches, but most areas had 0.5 to2 inches.  The 2-3 inch totals were in the Mohawk Valley area.  

The Base 50 Growing Degree Days ranged from 25 to 100, lower than last week because of the cooler temperatures.  The entire state is behind last year.  The southern Hudson Valley, part of the Great Lakes, and the St. Lawrence Valley are more than 2 weeks behind last year.  Other areas range from 3 to10 days behind last year.  Compared to normal the state still varies from 2 weeks ahead to 2 weeks behind.  Areas in Broom, Delaware, Herkimer, and Otsego counties are 10 to more than 2 weeks ahead of normal.  Surrounding those counties in part of the Eastern Plateau, Mohawk Valley, and in the Hudson Valley are areas 0 to 10days ahead of normal.  Western NY, western St. Lawrence Valley, and most of the Northern Plateau are 1 to 2 weeks or more behind normal.  Areas in between are 0 to 7 days behind.

No precipitation and mild temperatures areexpected for the next week as high pressure will be in control.  Today?s temperatures will be in theupper 70?s and lows in the 40? s and low 50?s.   We will have a couple more cold nights, but no frostsare expected.   The hightemperatures will be in the mid to upper 70?s Friday through Wednesday withsunny skies.  Friday?s low will bein the upper 40?s to low 50?s, Saturday in the mid 50?s, Sunday upper 40?s tothe north and upper 50?s to the south.   Monday through Wednesday will have low?s in the mid toupper 50?s.  The 8 to 14 dayoutlook shows temperatures above normal for the whole state and precipitationabove normal for the southern half of the state.

Two-spotted spider mites in soybeans

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Two-spotted spider mites are tiny, oval, 8-legged, pale-bodied arachnids.  The feeding of spidermites causes a stippling of leaves.  Severe feeding by many mites causes a bronzing of the leaf.  The injury from spider mite feeding can resemble afoliar fungal disease infection.  Another identifying factor of spidermites is the silk-like webbing they produce.  The webbing can be seen on leaflets and petioles in a heavily infested field.  The mites are able to use the silk to transport by wind to un-infested areas of a field.  When scouting, to help to confirm the presence of spider mites, hold a white piece of paper under a plant.  Tap on the plant, and some of the mites should fall to the paper.  They appear as yellow or yellow brown moving specs.

Spider mites on soybean

Early symptoms of spider mite injury on the upper leaf surface

Spider mite populations can increase extremely rapidly - they can develop from egg to adult in 5 days with high temperatures.  Cool, damp weather often leads to steep declines in spider mite populations by encouraging fungal pathogens to take control.

Spider mites are regular residents of weedy areas at field edges.  During dry weather, if these weed hosts become stressed, spider mites may begin to move into the nearby crop. Thus, an infestation usually begins at field edges and radiates into the field. While a spot-treatment with an insecticide may be helpful to combat the start of a severe infestation, it is critical to scout the whole field.  Low numbers of spider mites can be present before the injury can be seen from a distance.  When chemical control is chosen for spider mite management, it is critical to bear in mind the risks of "flare-ups" from use of pyrethroid insecticides.

Alfalfa Snout Beetle in Fall Alfalfa

Keith Waldron

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Short, chlorotic alfalfa? Alfalfa stands showing signs of premature senescence? Do you grow alfalfa in Oswego, Jefferson, Cayuga, Wayne, Lewis, St. Lawrence, Clinton, Essex or Franklin Counties?

If your farm is located in one of the above NY counties where ASB has been confirmed? watch your alfalfa fields this fall for signs of stress as this is when fields can begin to show symptoms of ASB larval feeding damage. Alfalfa snout beetles (ASB) are root-feeding weevils.  The vast majority of ASB impacts come from direct root loss and plant death caused by ASB larval feeding. ASB feeding damage may be suspected if one detects alfalfa fields with short, chlorotic, or otherwise weakened plants or large areas within fields void of any alfalfa.

In North America these insects are only found only in the nine northern New York counties listed above and in portions of southern Ontario, Canada. The native home of snout beetle is Europe where it can be found from Italy to England and Poland.

Alfalfa snout beetle larvae are legless, white, and ? inch long. ASB larvae are found shallow in the soil when very small but move deep in the soil during mid July to late August (18-24 inches). In September the large larvae move backup to the top 8 and do most of the tap root severing in September and October.  After development is completed, they then move deep in the soil to overwinter. Larvae move deep in the soil in the fall after feeding (18-24?)and remain there for the next 18 months.  Midway through the summer they pupate but remain deep in the soil until the following spring.

If you grow alfalfa in one of the counties mentioned and suspect ASB injury, dig up a few plants showing symptoms getting as much of the root system as possible. Look for damaged, girdled roots and presence of ASB larvae.

ASB damage in the spring looks similar to winter killed alfalfa with plants failing to "green up".

Plant breeding and biological control research is underway at Cornell to develop options to mitigate ASB injury. But for now the best option for managing this important pest is a three year crop rotation with a row crop.

Fall stand counts are an indication of the health of your alfalfa crop. There are a number of pests and crop management issues that can reduce a stand count in alfalfa. The following are guidelines for stand counts in NYS:

Crowns per square foot
Harvest Year
Optimum Stand
Adequate Stand
New Spring Seeding
1st hay year
2nd hay year
3rd and older

Fall scouting before the first hard frost can also reveal pest problems. If you find yellow to brown plants it may indicate one of several different disease problems. These could range from disease problems such as verticillium wilt, leaf spots, fusarium wilt, anthracnose and more. An inspection of the root system can also indicate disease problems. Yellow, reddish-brown to black discolored or damaged roots may indicate presence of phytopthora root rot or verticillium wilt. Premature senescence of alfalfa stands may indicate stress damage by alfalfa snout beetle larvae in those counties with confirmed infestations.

More information on current alfalfa snout beetle management projects using nematodes as biological control agents and efforts to develop resistant alfalfa varieties can be found at the Northern New York Agricultural Development Program's website.

Think Weeds in the Fall!

Ken Wise

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In the fall, many weed species are fully-grown and easily identified. Correctly identifying and recording significant weed infestations and their location is helpful for improving weed management decisions. Knowing the weed type and biology (broadleaf, grass, sedge, summer or winter annual, biennial, or perennial) is critical in selecting the right weed control measures. Remember, while herbicides are widely used for weed control other methods like crop rotation, cultivation, proper fertilization, planting dates, banding pre-emergence herbicides, crop spacing, plant populations, cover crops and combinations of these techniques should also be considered as part of an integrated weed control program. Conduct your fall weed surveys from late August through October. Sketch out a map of the field, walk each 1/4 of the field, and record the identity and relative infestation of the significant populations of weeds you observe. While no economic thresholds have been developed for weeds in New York, we recommend using a weed rating scale. The following scale can help you determine the severity of weed infestations in cornfields.

Evaluating Weed Presence- Weed Rating Scale:
Determine the intensity of each weed species as follows:

None: No weeds present

Few: Weeds present but very few plants within the field. Enough plants to produce seed but not enough to cause significant economic loss in the current year.

Common: Plants dispersed throughout the field, an average of no more than 1 plant per 3 feet (.91m)
of row, or scattered spots of moderate infestation.

Abundant: Fairly uniform concentrations across field. Average concentrations of no more than 1 plant per foot (.30m) of row or scattered spots of severe infestations.

Extreme: More than 1 plant per foot (.30m) of row for broadleaf weeds and 3 plants per foot of row for grasses, or large areas of severe infestations.

So take a few minutes and look at your fields---it will help save on weed control costs and increase crop production. Remember, if you don't look, you will never know what weeds are there.

Keeping Pest Records

Ken Wise

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It is very important to keep records from year to year on certain pest problems that may have occurred. Write down observations that you made over the season. Did potato leafhoppers go over threshold and which field(s)? Were there certain corn diseases present? Did you have corn that had corn rootworm injury? Were there new weeds or weed escapes you did not expect this year? Pick up a pencil and write them down on a field to field basis to better select certain management practices the next season. For example, if you were hit with potato leafhoppers this season and you want to rotate your alfalfa, one management option to consider for the future is use of a potato leafhopper resistant alfalfa variety. Another example might be to select wheat varieties that are resistant to certain diseases. If you had weed escapes you might reconsider your selection of weed control products. Are your pesticide use records up to date? Rates, dates, efficacy, rotational restrictions, etc. It is always important to keep pesticide records up to date.  If you wait too long you may forget what happened in certain fields. So write them down! A sharp pencil beats a dull memory!

Soybean Rust Update

Gary Bergstrom
Plant Pathology, Cornell University

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United States Soybean Rust Commentary (updated: 09/02/09)

On September 2nd, soybean rust was reported in South Carolina for the first time in 2009 in a soybean sentinel plot in Berkeley County. South Carolina is the 8th state to report the disease this year. Soybean rust was also detected in four counties (Arkansas, Ashley, Lonoke, and Monroe) in Arkansas. On September 1st, soybean rust was reported on soybeans in Jefferson and Phillips Counties, Arkansas; Panola County, Mississippi; Macon and Miller Counties, Georgia; and Lee, Macon and Crenshaw Counties, Alabama.

In 2009, soybean rust has been found in eight states and 97 counties in United States, and in two states and five municipalities in Mexico

NY State Soybean Rust Hotline: 607-255-7850

NYSSoybean Rust Website

USDA Soybean RustWebsite

Soybean Aphid Update

Keith Waldron

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Crop Growth Stage Last Modified: 08/28/09

Soybean growth variable across state. Majority of
fields currently reporting late vegetative growth
stages to mid pod fill R5.

Observation and Outlook - Insect Last Modified:08/28/09

Soybean aphid populations have moderated with many fields below threshold. Although field by field variations still exist, SBA's are becoming more difficult to find in some areas including areas where they were once very common. Populations of beneficial arthropods including Coccinelids, syrphid flies, lacewings, parasitic wasps and fungal pathogens reported statewide. Spider mite infestations in soybeans have been reported in some areas of central and western NY.

For more information see: Management Toolbox - Guidelines - USA

Clipboard Checklist

Keith Waldron

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* 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, yields, etc.

* Watch for weed escapes, any patches of herbicide resistant weeds?

Field Corn:

* Note crop growth stage and condition

* Check for European corn borer, armyworm, foliar diseases, vertebrate injury (birds / deer), weed escapes, herbicide injury, nutritional deficiencies, etc.

* Check tasselling / pollinating corn for corn rootworm populations

* Monitor weed populations noting presence of "who", "how many" and "where"

* Check herbicide resistant corn fields for herbicide resistant soybean

Alfalfa & Hay:

* Monitor alfalfa seedings for weeds, for potato leafhopper& diseases.

* Check established alfalfa stands for potato leafhopper, weed and disease problems.

* Storage areas cleaned and ready to accept next harvest?


* Note crop growth stage and condition

* Evaluate stand for soybean aphid, spider mites, deer, weed assessment, foliar disease incidence

* Check herbicide resistant soybean fields for herbicide resistant corn

Dairy Cattle: Livestock Barn Fly Management:

* Monitor animals and facilities for house fly and stable fly populations

* Check facilities for favorable fly breeding conditions (organic matter + moisture): leaks in watering systems, roof gutters for leaks and potential overspill, drainage,

* 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 * Continue fly monitoring: install "3X5" index card fly speck monitoring cards through out barn

* Use, replenish, replace fly management materials: sticky fly tapes/ribbons, insecticide baits, natural enemies (parasitoids), fly population monitoring (3 x 5) spot cards

* Continue release of purchased natural enemies (fly attacking parasitoids)

Dairy Cattle: Pasture Fly Management:

* Monitor animals for presence of face flies, horn flies and stable flies. Action guidelines: face flies (average 10 per animal face), horn flies (average 50 / dairy, 200 / beef cattle per animal side), stable flies average 10 per animal  (all four legs)

* Check feed bunk / water source locations for signs of stable fly breeding (moist undisturbed organic matter ? spilled feed, round bales, etc.), minimize source of moist organic matter i.e. fly breeding areain barn and in adjacent animal loafing yard

* Check paddocks for forage quality / quantity, rotate as appropriate

* Check paddocks for vegetation poisonous to livestock

* Consider use of fly traps to help reduce deer, horse and stable fly populations


* Pre-clean in and around grain storage bins in anticipation of soybean and grain corn harvests.

* Keep areas around storage bins and silos clean and mowed


* Note any repairs needed for recently used equipment: tractors, tillage implements, harvesting equipment, etc. as they are cleaned and serviced.

* Calibrate manure spreaders - maintain records on amount spread per field

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