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Weekly Field Crops Pest Report 2007

May 1, 2007                Volume 6 Number 3

1. View from the Field

2. Stewarts Wilt Again in 2007?

3. Will Early-Planted Corn Be Vulnerable to Seed Decay and Seedling Diseases?

4. Blind Cultivation in Corn Part 1

5. Virus Diseases of Wheat-What to Look For!

8. National Soybean Rust Update

7. Alfalfa Snout Beetles Begin Spring Emergence

8. Alfalfa Weevil and Growing Degree Days in NYS

9. Clipboard Checklist

10. Contact Information

View From The Field

Eastern NYS
Ken Wise, NYS IPM

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Western NY and Finger Lakes - Julie Dennis-NYS IPM

I visited a buckthorn patch in Ontario County on April 26th. Careful scrutiny of buds and branches revealed no soybean aphid eggs present. Recall that buckthorn is the overwintering host of soybean aphid, a little beast that attacks soybeans. Reports from early April in Ohio indicated that aphid egg hatch occurred immediately following bud break on buckthorn. The buckthorn plants I observed were just on the verge of bud break. Across most of New York State, our winter temperatures were not cold enough to kill soybean aphid eggs. A recent study conducted at the University of Minnesota indicates that soybean aphid eggs can survive to temperatures as cold as -29o. We’ll keep checking buckthorn and keep you posted!

Eastern NY - Ken Wise-NYS IPM

On April 30th I saw my first ladybeetle of the year! It was in an alfalfa field at the Cornell Research Farm at Valatie. The seven-spotted Ladybeetle species was introduced from Europe. It is an effective predator, adults will eat from 3,000 to 4,000 aphids during their lifetime and a single larva can consume 800 to 1,000 aphids.

seven-spotted Ladybeetle

In the last two issues I have talked about snow mold in triticale. Tom Kilcer is evaluating triticale varieties at the Cornell Research Farm at Valatie. From the photo below you can see that some varieties seem to have survived snow mold and other winter stresses better than others. I look forward to the results of Tom’s work.

triticale varieties

The alfalfa snout beetle (ASB) spring emergence has begun in the north country, reports Dr. Elson Shields from the Department of Entomology at Cornell University.

Statewide - Keith Waldron, NYS IPM Program

Dairy Fly Management - IPM Web broadcast - May 3, 2007

A two hour Dairy Fly Management Integrated Pest Management (IPM) teleconference will be presented Thursday, May 3, 2007 from 10 am to noon. This northeast SARE sponsored program will provide extension personnel, producers, veterinarians and other agriculture professionals with an overview on what one needs to know about managing house and stable fly populations in confined dairy facilities.

Speakers include an IPM specialist and two veterinary entomologists from Cornell University and the University of Florida. The workshop will present IPM principles and practices to help producers avoid, minimize, or manage dairy house fly and stable fly populations. Topics will include pest identification and biology, assessment techniques, management including discussions on cultural control, biological control using natural enemies, trapping, insecticides including insecticide resistance and suggestions for additional resources. A portion of the program will be devoted to a "questions from the audience" session.

The workshop will be available as a web streamed broadcast. Access the program here.

Stewart’s Wilt Again in 2007?

Julie Dennis, NYS IPM

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Last year, we heard many reports of Stewart’s wilt in field corn. This bacterial disease can cause serious damage in seedling sweet corn. The damage rarely reaches economic proportions in field corn, but it is eye-catching.

Stewart’s wilt is vectored, or spread, by the corn flea beetle. Corn flea beetles pass the winter as adults at field edges. They dwell under crop debris or just beneath the soil surface. The risk of Stewart’s wilt depends upon the survival of the adult flea beetles over the winter. In a nutshell, if the winter is mild, more flea beetles survive, and the disease will be more severe. What is the threshold for defining a “mild” winter? A table from the University of Illinois showing the predictions of temperatures for Stewart’s wilt occurrence is below:

table showing the predictions of temperatures for Stewart’s wilt occurrence

A predictive tool based on December, January, and February temperatures was first developed, and continues to be refined by, researchers at the University of Illinois.It is not clear the role that other weather-related factors such as snow cover (depth and duration) play in corn flea beetle survival and Stewart’s wilt threat the following summer.

Mike Hoffmann and Jeff Gardner in the Cornell Department of Entomology, and John Gibbons of Ontario County CCE and NYS IPM compiled weather data from this past winter and have made Stewart’s wilt predictions for 2007 based on a similar prediction method developed at Iowa State.

The Iowa State prediction method:

Number of months ³ 24° F

Predicted risk

0

Negligible

1

Low to moderate

2

Moderate to high

3

High

Given the above-average temperatures in December and January, the 2006-2007 winter is considered a moderate one, and the temperatures predict a moderate to high risk of Stewart’s wilt in NY in 2007. Maps are available here.

For a complete report on temperatures across the state, please contact Julie Dennis.

Will early-planted corn be vulnerable to Seed Decay and Seedling Diseases?

Julie Dennis, NYS IPM

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Early planted corn seed will likely sit in cold soils for awhile before seeds germinate, giving them extra time to be vulnerable to seed decay and seedling rots.

Seed Decay
Seed decay is caused by a number of soil-inhabiting fungi such as Pythium, Fusarium, Diplodia, Rhizoctonia and Penicillium. These fungi can infect seed before it germinates, causing mortality. Seeds infected with decay fungi are discolored and soft. Many times fungal material may grow on the seed. If you are digging around in the soil in a few weeks to investigate those gaps in the row, a seed that has rotted may be completely decomposed and therefore cannot be found.This can make tracking down the culprit a little difficult!

Seedling Blight
Sometimes the seed may germinate and grow but then die as the plant emerges from the soil. Seeding blights are caused by many of the same fungi that cause seed decay. Seedling blight symptoms include discolored seedling coleoptiles and roots. Seedlings may have a wet, rotted appearance before they reach the soil surface. Above ground symptoms of blight may include seedlings that turn yellow, wilt and die.

Factors that contribute to both seed decay and seedling blights may include cold (<65oF), wet soils. These unfavorable conditions can lead to slow emergence and slow growth of seedlings. Plant or seed injury from fertilizer burn, incorrect herbicide application, or soil crusting can add to plant stress at the vulnerable seedling stage. Fortunately, planting high quality corn seed is common practice, and fungicide seed treatments are a normal part of the spring routine for many producers. These practices help prevent many outbreaks of seed decay and seedling blight.

Blind Cultivation in Corn Part I

Ken Wise, NYS IPM

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Cultivation has been used for thousands of years to reduce weed competition with row crops. It is only recently that we have had herbicides to control weeds. With concerns for the environment and costs of herbicides, cultivation is slowly starting to be used again by field crop producers. All organic corn producers use cultivation. Interest in revisiting this weed management practice is also increasing among conventional corn producers in New York State.

Timing is Everything! Timing early season weed control is always a very important aspect of maintaining good corn yields. Weeds compete for limited resources. If weed control is delayed until after the V4 stage of corn growth, yields start to drop dramatically. The question by most field crop producers is “how do you control early season weeds with cultivation?”

One method that is being used is “Blind Cultivation” also known as “broadcast weed cultivation”. No, this isn’t done while closing your eyes while driving the tractor… Blind cultivation uses certain kinds of cultivators to disrupt the top 1/2 to 1 inch of soil, uprooting and exposing the newly sprouting weed seedlings to desiccation while the seedling are still very tiny. Scouting fields is a requirement to know when weeds are in the “white root stage,” the stage at which the seed begins to sprout and the seedling hypocotyl is elongating. Blind cultivation works best when it is hot and the sun is hitting the surface of the field. The goal of this method is to kill weeds when they are they most sensitive to disturbance. Normally a blind cultivation occurs a week after planting and again once the corn is 2 to 3 inches tall depending on the cultivator being used.

Planning is essential if you want to use blind cultivation as a means to control annual weeds. One aspect to consider is what kind of cultivation tool will best fit a farming situation? Rotary hoe, flex-tine weeder, and spike tooth harrows are some of the mechanical weeders being used to control early season annual weeds in field corn. Read next week’s pest report for more details describing each of these tools.

Virus Diseases of Winter Wheat -What to look for

Julie Dennis, NYS IPM

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A couple of warm, sunny days recently encouraged vigorous growth of the winter wheat stands that I have been scouting.This is the prime time to monitor fields for wheat spindle streak mosaic virus and yellow dwarf.

Wheat spindle streak mosaic virus (WSSMV) symptoms are yellow-green dashes or streaks with tapered ends, running parallel to the leaf veins. A soilborne fungus that attacks the roots of wheat in the fall transmits WSSMV. Symptoms often show up on plants in wet soils, but excessive moisture in the spring is not required for infection to occur. Cool spring temperatures like we are now experiencing are ideal for continued development of WSSMV. Wheat is at the greatest risk from losses to WSSMV when there are prolonged cool periods in April and May.As temperatures warm, plants usually outgrow the disease. Click here to see photos of WSSMV

Yellow dwarf symptoms include yellowing of leaf tips, sometimes progressing to red or purple colors. Several species of aphids common in New York transmit yellow dwarf. If winter wheat was planted too early in the fall, aphids may have had time to infest and infect plants. If yellow dwarf infections occur in the spring, instead, symptoms will appear later. Stay tuned to the Pest Report for updates. Photos of symptoms can be seen at Yellow dwarf affecting a whole field and Yellow dwarf: healthy vs. diseased plant

Rescue treatment options to eliminate infections from viral disease are not available. Fortunately, severe outbreaks of viral diseases are uncommon in wheat in NY since resistance is present in most of the commonly grown cultivars. However, scouting now for these diseases, and submitting suspicious samples for correct identification to the Cornell Plant Disease Diagnostic Clinic has the value of verifying the presence of these diseases. Next time wheat is planted in the same field, preventative management, such as planting a resistant cultivar, becomes an easy choice.

Soybean Rust Update

Gary Bergstrom
Department of Plant Pathology, Cornell University

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New York State Soybean Rust Information Center

(Updated April 27, 2007 )

NY State is in the process of coordinating soybean rust sentinel plots for the 2007 growing season. Twenty sentinel plots are tentatively planned in the following counties: Cayuga, Chautauqua, Chemung, Chenango, Columbia, Cortland, Jefferson, Montgomery, Oneida, Onondaga, Ontario, Orleans, Oswego, St. Lawrence, Seneca, Steuben, Suffolk, Wayne, and Wyoming. Updates on scouting efforts in these sentinel plots will be posted weekly on the NY State Soybean Rust Information Center. Scouting efforts in the rest of the U.S. are just beginning. Sentinel plots are being planted and monitored in the south. Kudzu is also being scouted from Texas to South Carolina. In 2007, soybean rust has been detected on kudzu in 9 counties in Florida, 5 counties in Georgia and 5 counties in Alabama. The only detection of soybean rust on soybeans this year was in February in Hidalgo County, Texas. The field has since been cultivated and planted with corn.

National Soybean Rust Commentary

(updated: 04/23/07)

There have been no new reports of soybean rust since late March. The disease can no longer be found in many of the previously-infected kudzu patches in Florida, Georgia or Alabama. This is most likely due to the freeze events that occurred in March and early April. Recent dry weather conditions have been unfavorable for soybean rust development in these states. Weather conditions have been more favorable for rust in Texas and the western Gulf Coast states but there have been no new reports of the disease in this region. Scouting efforts have intensified in the south as soybean sentinel plots continue to be planted and monitored. Kudzu patches are also being scouted from Texas to South Carolina. Soybean rust has been detected on kudzu in 9 counties in Florida and in five counties in each of Georgia and Alabama. The disease was also detected on soybeans in one county in Texas, but that field has since been cultivated and planted with corn.

USDA Soybean Rust Website

Alfalfa Snout Beetles Begin Spring Emergence

Ken Wise, NYS IPM

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The alfalfa snout beetle (ASB) spring emergence has begun in the north country, reports Dr. Elson Shields. The expected warm early spring temperatures over the next week or so should enhance ASB viewing opportunities as adults of this unique species emerge and begin moving to new alfalfa fields.

Alfalfa snout beetles (ASB) are root-feeding weevils found only in nine northern New York counties  (Cayuga, Clinton, Essex, Franklin, Jefferson, Lewis, Oswego, St. Lawrence and Wayne). ASB was also discovered on a number of the thousand islands in the early 1960s. and in Prescott Ontario, Canada in 1986.  The native home of snout beetle is Europe where it can be found from Italy to England and Poland.

ASB adults  are mottled gray, humpbacked, 1/2 inch long, do not fly, and are all females. Adult alfalfa snout beetles leave fields void of alfalfa this time of year en mass (by the tens of thousands) in search of new alfalfa fields to lay their eggs. Once they find a suitable location, ASB adults  feed on alfalfa foliage and lay eggs that hatch into root feeding larvae. While adult feeding can trim the tops of alfalfa and other hosts, the vast majority of plant death comes from direct root loss caused by ASB larvae feeding.

Alfalfa snout beetle larvae are legless, white, and 1/2 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 back up 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.

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

Alfalfa Snout Beetles in your neighborhood? In addition to alfalfa, other host plants for ASB include: red clover, dock, wild carrot, quackgrass, and white clover. ASB control is best achieved with a three year rotation of alfalfa with a row crop. Non hosts, i.e. good crops to have in rotation to minimize ASB losses include: corn, wheat, oats, soybeans, and potatoes. Insecticides are not recommended to control ASB.

Thanks Elson for helpful comments and suggestions.

Alfalfa Weevil and Growing Degree Days in NYS

Ken Wise, NYS IPM

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Nate Herendeen reports finding alfalfa weevil eggs in henbit in Western NYS this week, but I have not even seen alfalfa weevil adults yet this season in the East. Remember alfalfa weevil populations can build up over the life of the alfalfa stand. The longer an alfalfa field is in production the higher the risk of alfalfa weevil damage. Adult weevils that enter fields in the spring are light brown and 3/16" long. They have a band of darker brown down the center of their back and a long snout.

If you keep track of growing degree days you can predict when certain stages of alfalfa weevil development occur. Remember that alfalfa weevil’s base temperature for determining its growth stages by growing degree days is 48 degrees F. You should start scouting and sampling fields at about 350 growing degree days. For more information on alfalfa weevil, view the following management guide: IPM 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

280

Instar 1

315

Instar 2

395

Instar 3

470

Instar 4

550

Cocooning

600

Pupa

725

Adult Emergence

815

CURRENT Accumulated Growing degree days (48F Base)
March 1 -April 30th , 2007

Location

Base 48 F

Base 50 F

Batavia

122

96

Chazy

70

56

Clifton Park

154

125*

Geneva

123

98

Ithaca

113

90

Prattsburg

109

87

*Missing Data

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

  • Review EPA Worker Protection Standard training and posting compliance needs

  • Walk fields to check tile flow, check and clear drainage outlets.

  • Maintain crop records by field, including variety, planting date, pesticides used, nutrient inputs including manure, etc.

  • Watch for early season weeds

Corn:

  • Finish corn planting by May 15, if soil conditions allow

  • Use corn insecticide seed treatment in the planter box, if available, or plant insecticide pre-treated seed

  • Monitor for weeds, note presence of "who", "how many" and "where"

  • Adjust post emergence weed control actions

  • Determine corn plant populations, make notes on germination problems

Small Grains:

  • Monitor winter grains for crop stage, insect and disease problems

  • assess crop for adequate stand and plant vigor

Alfalfa & Hay:

  • Monitor alfalfa seedings for weeds, insects & diseases.

  • Check established alfalfa stands for over wintering injury, frost heaving, alfalfa weevil, weed and disease problems.

  • Timothy stands: check fields for symptoms of cereal rust mite

Equipment:

  • Note any repairs needed for corn planter, seeding equipment, alfalfa harvesting equipment, and tillage implements as they are cleaned and lubricated.

  • Service corn planter as needed.

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

Contact Information

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Julie Dennis:
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