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Weekly Field Crops Pest Report 2010

April 30, 2010           Volume 9 Number 2

1. View from the Field

2. Weather Update

3. Timothy Stand Assessment

4. Soybean Aphids?

5. Alfalfa Weevil Larvae Development, Damage and Growing Degree Days

6. Clipboard Checklist

7. Contact Information

View from the Field

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The alfalfa at SUNY Cobleskill (April 29) was 6 to 8 inches tall and looked very good. With the colder weather this week alfalfa weevil seems to have gone into hiding. I did see a few tarnished plant bugs. At the Cornell Research Farm in Valatie (April 30) the alfalfa was 8 to 10 inches tall. I did discover a few adult alfalfa weevils and a plethora of tarnished plant bugs. I did not find a single lady beetle this week.

Weather Update

Jessica Rennells
Northeast Climate Center, Cornell University

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Winter 2010 (Dec—Feb) was slightly warm and dry.  The average temperature for the state was 24.1 degree F, 0.8 degrees above normal.  The coldest winter was 14.9 degrees in 1918; the warmest was 30.9 degrees in 2002.  There was 8.63” of precip, just .02” below normal. The driest winter was in 1980 with 4.34”; the wettest in 2008 with 12.05”.  March 2010 was 6.6 degrees above normal with an average temperature of 38.5 degrees. This ranked as the states 6th warmest March. The coldest was in 1916 at 22.2 degrees; the warmest in 1946 at 42.0degrees.  There was 3.43” of precipitation in March, 0.31” above normal.  The driest March was in 1915 with 0.63”; the wettest was in 1913 with 5.62”. There was no snow in Syracuse or Rochester for the first time this March.

Most of the state was 0-3 degrees below normal during the past week.  Though the eastern portion of the state was 0-3 degrees above normal.  A small area in the Adirondacks was the warmest with 3-6 degrees above normal. Precipitation ranged from 0 to 2 inches.  The southern border of the state received 1-2 inches, and the center of the state had half an inch or less. 

During the last week there were less than 25 Base 50 Growing Degree Days for the entire state. The accumulated GDD from March 15 to present are 50-100 for most of the state.  The Adirondacks have had less than 50 and the northern finger lakes region has had 100-150.   The Mohawk Valley is 0-3 days behind last year, but most of the state is 0-7 days ahead of last year.  All of the state is ahead of normal, with most areas 10-14 days ahead of normal. 

The weather will be warming up for the weekend as high pressure builds in before turning more seasonable next week.  Today will be dry with temperatures in the low 50s and 60s.  The overnight lows will still be in the 30s. Fridays temperatures will warm into the 60s and low 70s with lows in the upper 30s and 40s.  Saturday will be warm with temperatures reaching the upper 70s and low 80s.  The low temperatures will be in the 40s and 50s, with the warmer temperatures to the southwest.  There will be a chance of scattered showers in western part of the state.   Sunday we will have continued warm weather with highs in the 70s to low 80s again for most of the state. The northern most of the state will stay in the lower 70s. The lows will be very mild in the upper 50s and around 60.  There will be rain showers for most of the state. Monday will be cooler but still seasonable with temperatures in the 60s for most of the state. Overnight lows will be in the upper 40s and low 50s.  There is a chance for lingering scattered showers. Tuesdays highs will be in the mid 50s to low 60s.  The lows will be in the upper 30s to mid 40s.   Wednesday will be another day in the upper 50s and low 60s with lows in the 30s to low 40s.  Few scattered showers are possible in the southern half of the state.

The five day precipitation amounts range from one to three quarters of an inch.  The 8-14 day outlook is showing temperatures below normal and precipitation above normal.

Looking forward into late spring and early summer drought conditions. NE Ohio, NW Pennsylvania, and western New York are currently abnormally dry and drought development is likely. There has been below average stream flow and low soil moisture. We will keep an eye on this as the spring progresses.

Timothy Stand Assessment

Keith Waldron

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Clear stand of timothy? Stunted areas within field? Drought stress symptoms when soil moisture appears adequate? Top2-6 inches of leaf tips chocolate brown in color? Leaf blades rolled up tightly, or have leaf tip flagging or distortion?

Could be a sign that field has Cereal Rust Mites (CRM) aka Abacarus hystrix (Nalepa). Symptoms of CRM damage include: retarded growth, stunting, and plant discoloration. Injured plants appear to be drought stressed even when adequate moisture is available for plant growth. As with most grasses, the edges of timothy leaves roll together when the plant is under moisture stress.

In recent years, CRM has been a problem in Pennsylvania, Delaware and Maryland. In NY, CRM infestations have been spotty causing potential problems for some timothy hay producers in the Finger Lakes region. A very informal survey several years ago found adult rust mites present in timothy in various places across NY, although economic impacts were not observed or measured.

Severe mite infestations can have two possible negative impacts. Feeding injury causes substantial yield losses and reduces hay quality because of the brown discoloration. Horse producers are reluctant to buy hay that is not the normal color of quality timothy.

This mite is miniscule in size making it not only hard to see, but equally hard to study. How would you know it was there? Compare field observations against the symptoms described above. Pick a few choice leaves showing the brown / flagging leaf tip symptoms, use your most powerful hand lens, look for presence of the tiny mites between leaf veins. (From the fact sheet cited below) Adult rust mites are very small (<1mm).They are spindle-shaped, with four legs and may be white, yellow or orange. You will need a 10 to 20X hand-lens to see them. Evidence of their presence on the plant is off-colored foliage and leaf or bud abnormalities. Large mite populations often produce many elongate, white shed skins. The immature stages are similar to the adult, but smaller. Immatures begin hatching in March, with the peak adult populations being reached peaking in April. Damage is most evident in April and May.

Management? Little is known at this time. The best information comes from PA, DE and MD.

Pennsylvania guidelines: Economic Thresholds - There are no established economic thresholds for this pest. Treatment is recommended, however, in fields with a previous history of cereal rust mites and/or when 25% of the plant tillers exhibit curled tips on the new leaf blades within several weeks following green-up. They continue stating ... "Research is underway to develop better monitoring plans and economic Threshold". For more information see the Cereal Rust Fact Sheet from Penn State.

Note: No insecticide/miticides are registered for use in NY to control CRM.

Soybean Aphids?

Keith Waldron

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No we have not seen any so far this season. However, last summer soybean aphids (SBA) were widespread across NY with many soybean fields reaching the 250 SBA / plant treatment threshold. What might 2010 hold for risk of SBA damage?

Soybean aphids (SBA) spend the winter as eggs along leaf buds of buckthorn, generally in the upper reaches of the buckthorn shrub. SBA eggs hatch in the early spring about the time that buckthorn leaves first begin to expand. The aphids have several generations on buckthorn before developing a winged generation that moves on in search of soybeans. The small egg size and distribution of soybean aphid populations make it a challenge to find the aphids on buckthorn in the spring. One indication of aphid activity can be the presence of ants in the foliage tending aphids and protecting the aphids from predators.

Early season monitoring of buckthorn in the Finger Lakes area this season have not, to date, found evidence of soybean aphid eggs or activity. It is quite possible that we just missed them. Others in Ohio and Pennsylvania have also experienced limited success. In our area, overwintering local SBA populations are often enhanced by an influx of SBA on storm fronts from the Midwest and Ontario about early July.

Since SBA were first detected in NY in 2001, we have observed an odd year / even year cyclical pattern of high and low SBA populations, i.e. odd numbered years such as 2009have had higher populations of SBA than even numbered years.

Entomologists theorize this trend reflects a tendency for natural enemy populations to rise and fall with levels of SBA populations. In high SBA (odd numbered) years natural enemy populations (lady bugs, minute pirate bugs, lacewings, syrphid flies etc.), tend to increase over time feeding on the SBAs, ultimately lowering the number that are available to overwinter. The following year fewer SBAs are available from local buckthorn sources to colonize soybeans. The smaller number of SBAs, however, also means predator species have fewer SBA prey. Fewer predators allow SBA populations to build up over time such that a higher SBA population is available at the end of the season to again migrate to buckthorn. This higher overwintering SBA population is then in place to move in numbers to soybeanst he following season. 

Will 2010 be a big year for SBAs? It is still far too early to tell, but historical trends and early indications might suggest no. Soybean producers are, of course, encouraged to monitor fields closely for signs of soybean aphids this season. We will be scouting for soybean aphids this summer, and if numbers begin to increase, we will inform growers through this newsletter.

Alfalfa Weevil Larvae Development, Damage and Growing Degree Days

Ken Wise

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When the weather starts to warm alfalfa weevil eggs will be laid inside new alfalfa stems. The question after eggs have been laid in stems is, "When will the larvae hatch?"  First instar larvae hatch from eggs at 280 degree-days (base temp. 48F). Newly hatched larvae are about 1/16 inches long and yellow to light green in color.

Alfalfa Weevil Larvae

The 1st instar larvae feed on the inside of the stem for a few days before exiting and moving to the fresh buds and leaflets on the ends of the stems. As the larvae develop they will feed on alfalfa leaflets.

Alfalfa Weevil Feeding Damage

As larvae feed, grow and molt they become green with white stripes down their back, have a dark brown head. Larvae ultimately grow to reach 3/8 inches long before pupation.

Recall that these larger larvae have big appetites and are responsible for 80% of the alfalfa yield lost to weevil feeding.

Alfalfa Weevil Cocoon

Next week we will discuss how to scout and manage for alfalfa weevil.

Growing degree Days for peak (50%) Occurrence of Alfalfa Weevil growth stage:

Stage or Event
Accumulated growing degree days (48F base temperature)
Eggs hatch
Instar 1
Instar 2
Instar 3
Instar 4
Adult Emergence
(Note: for alfalfa weevil predictions use Base Temp of 48F)

CURRENT Accumulated Growing degree days (48F Base)

March 1 -   April 28, 2010

Base 48 F
Base 50 F
*Indicates missing data
source: NEWA

Clipboard Checklist

Keith Waldron

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*Emergency contact information ("911", local hospital, Chem. Spill emergency contact, other?) posted in central posting area

*Walk fields to check tile flow, check and clear drainage outlets. Look for line breaks.

*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: winter annuals: chickweed, henbit, purple deadnettle, field penny cress, shepherd's purse; annuals: giant ragweed, lambsquarters, Pennsylvania smartweed, common sunflower

Alfalfa and Small Grains:

*Monitor alfalfa for alfalfa snout beetle (In Oswego, Jefferson, Cayuga, Wayne, Lewis, St. Lawrence, Clinton, Essex, and Franklin counties)

*Monitor alfalfa for alfalfa weevil as weather continues to warm.

*Evaluate established legume stands for winter damage (thinning stand, frost heave, Brown Root Rot), determine average alfalfa stand count, adjust crop plans if necessary

*Monitor winter grain fields for crop growth stage and condition, virus disease symptoms, cereal leaf beetle, weed pressure, goose damage


*Pre-plant weed evaluation

*Prepare land for corn if it is dry enough and begin planting this week if possible (even if it is cold!)

*Using a Bt hybrid? Have a refuge plan?


*Pre-plant field / weed evaluation

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