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NY Weekly Field Crop Pest Report, 2005

June 17, 2005 Volume 4 Number 9

1. View from the Field

2. Soybean Aphids Have Been Found in Early Emerging Soybeans

3. Soybean Aphid Biological Control: What to Look For

4. Sampling for Potato Leafhopper in Alfalfa

5. Is Corn Under Threat from European Corn Borer Yet?

6. Clipboard Checklist

7. Growing Degree Days in NYS

8. Up Coming Meetings

9. Contact Information

View From the Field

Western NYS

Julie Stavisky

Eastern NYS

Ken Wise

NYS

Keith Waldron

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Soybean TAg meeting in Orleans County this week, soybean aphids were observed. Numbers were very low, with a maximum of 10 per plant seen. Lady beetles were numerous, and we even saw lady beetle eggs.

In spring oats, numbers of cereal leaf beetles have declined from last week. Among other mortality factors responsible for the decline, Leslie Allee (Department of Entomology) and her team of experts confirmed the presence of parasitoids in cereal leaf beetle larvae this week.

This week at a soybean TAg meeting near Westmorland we discover soybean aphids on plants in the V1 stage. The number of aphids per plant ranged for 0 to 50. The mean was around 5 to 10 aphids pre plant and there were outliers with 30 to 50. There were also a few Asian multi-colored and 7-spotted lady beetles feeding on the aphids. There were many broadleaf weeds starting to fill in between the soybean rows. The most common weeds were: common ragweed, common lambsquarter, pigweed, horsenettle and velvetleaf.

I also found my first potato leafhopper this week at the Cornell Research Farm in Valatie. While it was one lone leafhopper it indicated that it has found its way to the Eastern side of the state. There were no soybean aphids in the soybean test plot at the research farm.

Soybean aphids have made their appearance in the northeast and the SBA monitoring network appears to be functioning quite well. We’ve had a few calls in NY regarding SBA’s in VE-V3 soybeans. Management overview so far? No big worries at this time, keep watching fields.

Our SBA populations have been low ca. 6-10 or less per plant typical. (More SBA information later this issue). Ontario Canada starting to see SBA populations last week. Very small pockets of 20-50 per plant on only a few plants in each field. Our northern neighbors have found them at the beginning of June in the past. They report SBA’s observed in areas that have lots of buckthorn (and overwintering eggs) and areas that have no buckthorn, suggesting that some SBA adults could have hitched a ride on weather patterns from the midwest or elsewhere?

Ohio reports SBA numbers about 20-30 per plant in northwest Ohio. Pennsylvania no SBA reports this week. Delaware, where SBA’s are not known to overwinter (lack of buckthorn), so far have not found any SBA’s.

Soybean aphids found in early emerging soybeans

Keith Waldron, NYS IPM

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Time for action or reflection? As they said in Hitchhikers Guide to the Galaxy….

Don’t Panic!

  • What we heard from the field last week …

  • SBA’ are present in unifoliate to V3 beans.

  • SBA’s per plant vary 6-10/plant, some higher.

  • Natural enemy populations variable: Some fields no natural enemies (lady bugs et al) observed, other fields modest numbers of natural enemies found.

  • Near drought conditions in some areas.

  • Some growers concerned over need / value of a preemptive insecticide spray....

The above scenario prompted a review of resources on SBA management. In addition, I shared a few Soybean aphid questions with our Midwestern entomology colleagues who have had considerably more experience with this insect than we have had in NY.

Recall that soybean aphids have only been in the US since 2000, first documented in NY in 2001, so our pool of data on it is somewhat limited. While we have not had many years to watch these insects in action, this is not the first time we have had soybean aphid (SBA’s) in NY beans this early. Fortunately, in those situations SBA populations never exceeded our threshold guidelines. Don’t worry at all? Too early to really tell. Fortunately, we have worked with SBA's in NY and there is also a considerable body of information available to us from Land Grant University research conducted in the Midwest US soybean belt. Based on previous research and our collective experience, we have reasonable insights. Now is the time to monitor fields to watch for SBA’s and document what’s going on. The following is an overview of some pertinent SBA information and some insights our colleagues provided.

Factors Influencing Soybean Aphid Population Dynamics in Soybean

  • Size of colonizing population from buckthorn

  • Soybean variety and quality

  • Mortality from: Predators (such as lady bug beetles, lacewing larvae, syrphid fly larvae, and minute pirate bugs), parasitic wasps that cause aphid mummies, fungal disease outbreaks, heavy thunderstorms

  • Temperature effects on reproductive rate and survival

  • Local re-distribution by winged aphids among fields

  • Dispersal of alates from fields

A number of on-line publications describe these factors in more detail. This particular list is from: MN Soybean Production

See end of this article for more soybean aphid information sources.

SBA threshold guideline - 250 per plant at or near R1.

This action threshold should be 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 250 per plant threshold guideline in most cases does not pay for itself. But if you have aphids at flowering, the SBA population is increasing (few or insufficient numbers of natural enemies present), then yield loss is to pod abortion and once pods are gone, there is no recovery of yield other than getting seed a bit bigger. This recommendation from the Midwest has held up well over the past 4 years.

Will insecticide treatments now (seedling stage, sub 250 SBA threshold) pay dividends down the road? Dr. David Ragsdale, entomologist UMN, recalls data from two aphid outbreak years where a single SBA treatment at V1 or V3 “resulted in no improvement in yield“.

A possible retort… "I'm going over the field with Round Up and the custom application is $9/acre so why not spike the RoundUp with an aphid insecticide?" The question is a matter of NEED rather than convenience. The data we have to date has not shown benefits from insecticide use at this time. Insecticides cost money. Use them when needed but save them for when you’ll get the most return on your investment. Several of the websites at the end of this article discuss this in more detail. Also, consider the other possible implications should insecticides be used now…

Impacts on natural enemies ­ and why you should care...

Over the past 4 years, our NY SBA research with Drs. John Losey and Ann Hajek (Entomology, Cornell) has documented good diversity and numbers of natural enemies in our soybean fields that have SBA populations. Ladybugs, nabids, carabid beetles, parasitoids and fungal pathogens all have been found in our NY soybean fields and are known to do a pretty good job of holding SBA populations in check. Yes, their numbers might be low in the initial part of the season but their numbers can pick up fast and…. aphid populations can be very attractive to hungry predators.

Dr. Ragsdale says their observation in Minnesota has been aphid populations below 50 to 100 per plant can be held in check with Natural Enemies (NE). When aphids are as dense as 50 per plant coccinellids (lady bugs) will begin to lay eggs, syrphids pay attention, Orius (minute pirate bug) does its thing, as do a raft of generalist predators. “Take out aphids and all the NE at V1 and aphids will continue to colonize and do so in "enemy-free space". A grower who treats with RoundUp and an insecticide now may be risking a need for a second insecticide treatment later this season.. Pause, reflect, delay and treat if necessary at the appropriate time.”

Dr. Bob O’Neil, entomologist from Purdue says: “The generalists (predators) in fields can do a pretty good job of preventing & delaying SBA outbreaks. Avoiding sprays below 100 aphids per plant helps give the natural enemies time to work & the higher SBA densities act to bring in more predators (and different species.). Spraying below 100 (or the 250 threshold for that matter) holds promise of creating a natural "enemy-free space"--an open invitation to yearly outbreaks. Grower-education on the role and potential of natural enemies can be an effective counter-point to "get 'em early' mentality inherent in tank mixes.“

Insecticide Use Now and Unexpected Impacts

Droughty conditions can be favorable to spider mite problems in soybeans. Dr. Ragsdale and Dr. Chris DiFonzo (entomologist Michigan State U) urge caution in selecting insecticides under these conditions. Some SBA registered insecticides (such as Warrior, Mustang Max, Pyganic, and others) can also flare spider mite populations.

WARNING: Many aphid species are resistant to insecticides. Multiple or poorly timed insecticide applications favor development of resistance. Scout to ensure insecticides are needed and well timed.

What will soybean aphid populations do over the next two months?

Only time will tell. Over the weekend a number of places across NY experienced thunderstorms and heavy rains. These have likely had devastating effects on SBA populations as the tiny insects were pounded off the seedlings. This also cancelled, at least for now, drought concerns. If you had fields with SBA concerns last week, recheck them.

Some practical advice from Drs. David Voegtlin, (IL Natural History Survey) and Robert O'Neil, (Purdue U) from an article: “Planning for the 205 Soybean Aphid Population” This is a very good overview of the Midwestern SBA management perspective.

Recommendations:

  • Weekly visits to soybean fields to examine even a few plants will help growers keep abreast of aphid population growth in their crop.

  • Use the 250 aphids per plant threshold. To use the threshold properly, it's important to know if the aphid population is increasing and that's why regular field visits are necessary.

  • Don’t panic! Just because there are some aphids in the field does not mean SBA populations will reach the threshold of 250 aphids per plant.

  • The natural enemies in their field are providing free pest control in most fields and in most years.

  • Spraying fields before the threshold only helps to disrupt the control these natural enemies provide and does not guarantee economic control.

  • The temptation to "tank-mix" a little insecticide with an herbicide (or fungicide) application "to get those aphids before they get me" is to be avoided!

  • Looking for aphids, checking the threshold, and then deciding if you need to do something, is the key for this year's aphid pest management.

Concluding remarks regarding soybean aphid treatments?

Wait and see. We are quite a ways off from 250 aphids per plant and reproductive soybean growth stages. It is possible that we may need management intervention later in the season. For now, continue to monitor fields for soybean aphids and for signs of soybean rust. Also know that there are lots of people looking for the aphid across our region and the Midwest and they are networked. If significant changes occur and better information becomes available it will be made available asap through local Extension Service and state Land Grant Universities. Keep in touch, keep informed, and stay tuned.

If someone is truly risk averse and feels compelled to treat.... if at all possible...set up, document, and evaluate a side by side treatment comparison….. We could all benefit from the data!

For more information and further discussion on soybean aphids check out:

Soybean aphid

Note statement at this site regarding tank mixtures (herbicide, insecticide, fungicide) and implications for sprayer specifications, nozzle size, droplet size, spray volume..

Soybean Aphid in Minnesota

Managing Soybean Aphid

U Wisconsin website has had several SBA articles

Planning for the 2005 Soybean Aphid Population

(D. Voegtlin, Center for Ecological Entomology, ILNatural History Survey; and R. O'Neil, Dept. Entomology, Purdue)

Soybean Research Update

(NCentral Soybean Research Program's ­ overview of what they know about SBA)

Soybean Aphid

(Nice factsheet from Ontario, includes images of common natural enemies)

Avoid a Tank Tri-Mix on Soybeans

New York State Soybean Rust Information Center

Soybean Aphid Biological Control: What to Watch For

Julie Stavisky, NYS IPM

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There are many species of lady beetle that voraciously consume soybean aphid. The most efficient predator is the multi-colored Asian lady beetle. (Yes, those are the ones who seek out the warmth of your house in the winter.) The larvae of these lady beetles consume as many as 200 aphids per day, while the adults consume about 150 aphids per day. Other species of lady beetle are not as efficient, but the pink lady beetles and the 7-spotted lady beetle are also effective aphid eating machines.

Other predators include the larvae of syrphid flies, minute pirate bugs, as well as other generalist predatory insects. Additionally, parasitic wasps and fungal pathogens cause aphid mortality. When scouting fields for soybean aphid, be sure to keep an eye out for all of these biological controls. It will be useful to track over time the proportion of aphid-infested plants that have natural enemies present.

Left: Adult Hippodamia parenthesis feeding on a cabbage aphid. (J.Ogrodnick)
Center: Fully grown larva of Harmonia axyridis. (A.T.Eaton)
Right: Lady beetle eggs. (J.K.Clark), University of California Statewide IPM Project (From Biological Control, A Guide to Natural Enemies, Cornell University)

Text Box: Photo from University of Georgia Text Box: Photo from Univ. of Florida
Syrphid fly larva
Minute pirate bug
Aphid “mummy” (evidence of a parasitic wasp)
Aphid infected with fungal pathogen. Photo from C. Neilsen, Cornell

Sampling for Potato Leafhopper in Alfalfa

Ken Wise

NYS IPM

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Scouting alfalfa fields is the key to early detection of potato leafhopper infestations. With the use of a 15-inch diameter sweep net you can determine if a potato leafhopper infestation has the potential to cause economic loss in alfalfa. Scouting for potato leafhopper starts after the first cutting of alfalfa (about the first part of June) till the first fall frost. You will want to use a potato leafhopper sequential sampling plan to determine if an infestation requires management or not. The first thing to do is determine the height of your alfalfa. Smaller plants are more vulnerable to potato leafhopper; thus there are different action thresholds for different heights of alfalfa. The second thing you will need to know is how to sample for potato leafhopper. A sample is 10 sweeps of the net. A sweep is one pass in front of you as you walk through the alfalfa. The return swing is counted as another sweep. Sequential sampling reduces the time spent in each field and tells you whether to treat (management action) or not treat (no management action). Use the following chart to determine potato leafhopper infestation levels.

N= No management needed at this time

T= Management needed as soon as possible

Write down the number of potato leafhoppers for each sample taken on the card. Add each sample to the next, keeping a running total of potato leafhoppers. You will need to take at least 3 samples using the sequential sampling method. On the sequential sampling card “N” is defined as no treatment (no management) needed at this time and “T” is defined as treatment (management) needed within in a week. If the sample is smaller than the “N” number stop and scout 7 days later. If the number of leafhoppers is larger than the “T” number then management action needs to be taken within a week. If the number of potato leafhoppers fall between “N” and “T” then continue and take the next sample till a decision can be determined. A guide with a printable version of the sequential sampling chart can be found in the Potato Leafhopper on Alfalfa Management Guide.

Is corn under threat from European corn borer yet?

Julie Stavisky

NYS IPM

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The first European corn borer adults of the season were caught in Ontario County during the last week of May. (The trapping network in western NY is managed and reported on by Abby Seaman, NYS IPM’s WNY extension educator for vegetables).

What do the first arriving moths mean to us in field corn? The first generation of caterpillars generally only causes minor leaf feeding injury. Corn in the early whorl stages, up to the 6th leave stage, will outgrow the damage that may happen. The greater potential for economic loss from ECB will happen later in the season when they bore into the stalks. Feeding on whorl stage corn looks like this: ECB damage

Full-grown ECB larvae are up to 1 inch long. The larvae are creamy-white to pink in color with a dark brown head capsule. There is a ring of dark colored spots on each segment of the caterpillar.

Clipboard Checklist

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General:

  • Maintain crop production activity records by field, including harvest date, pesticides used, nutrient inputs including manure, etc.

Established Alfalfa and Hay:

  • Monitor for Potato leafhopper

  • Monitor for anthracnose, look for shepherd’s crook symptoms

  • Monitor fields for weeds and diseases: record information on type and location for future cropping decisions.

Corn:

  • Evaluate weeds and adjust post-emergence treatments

    - Cultivate or treat if necessary

  • Monitor insects (cutworm, rootworm, wireworm, etc.), slugs, and foliar diseases (anthracnose leaf blight, eye spot, gray leaf spot, etc.)

  • Pre-Nitrogen Sidedress Soil Test and apply sidedress as needed

Soybeans:

  • Evaluate stand for emergence issues, plant population

  • Begin to monitor for soybean aphids, soybean rust

Small Grains:

  • Check condition of flag leaf for cereal leafbeetle and foliar (and head) diseases

  • Winter Wheat expected to be heading and flowering stages

  • Spring grains have headed out. Continue scouting for powdery mildew and cereal leaf beetle

Pastures:

  • Adjust rotation

Livestock:

  • Insecticidal ear tags for heifers on pasture

  • Manure management and initiate release of biological control agents (parasitic wasps) for house fly and stable fly control in confinement facilities.

  • Check condition of pastures and animals on pastures

    - Adjust pasture rotation as necessary

    - Evaluate need for face fly and stable fly control measures

Equipment:

  • Prepare small grain combining equipment or arrange for custom combining

  • Check grain handling and storage equipment, augers, bins, fans.

Growing Degree Days in NYS

Keith Waldron, NYS IPM

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March 1 - June 15, 2005

Location

Base 48 F

Base 50 F

Batavia

634.3

540.2

Chazy

489.7

412.4

Clifton Park

822.8 

697.6

Geneva

663.0

561.6

Ithaca

585.5

494.3

Mexico

527.3*

444.9*

Prattsburg

544.6

461.6

Source: http://newa.nysaes.cornell.edu/base5005.htm

Note: Alfalfa weevil expected growth stages (Accumulated GDD@48F):

4th instar (550), cocooning (600), pupa (725), adult emergence (815)

Up Coming Events

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July 6 - Wednesday - NY Weed Science Field Day, Valatie Research Farm. Valatie, NY

July 7 - Thursday - Seed Growers' Field Day, NYSIP Foundation Seed Barn, Ithaca, NY (791 Dryden Road, Route 366)

July 13 - Wednesday - NY Weed Science Field Day, Robert B. Musgrave Research Farm, Aurora, NY (Poplar Ridge Road, connects 90 and 34B)

July 14 - Thursday - NY Weed Science Field Day, H. C. Thompson Research Farm, Freeville, NY (10 miles Northeast of Ithaca, Fall Creek Road, Rt. 366 extension)

July 15 - Friday - Aurora Field Day, Robert B. Musgrave Research Farm, Aurora, NY

Contact Information

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Julie Stavisky: IPM Area Educator, Livestock and Field Crops, Western NY
Phone: (315) 331-8415
Fax: (315) 331-8411
Email: js38@cornell.edu

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