Vol. 20, No. 18, August 31, 2005

In this Issue
Corn earworm and European corn borer still a threat to sweet corn, peppers, snap beans and tomatoes
Infectivity rates for aster leafhoppers and aster yellows
Herbicide resistance screening available at MSU Diagnostic Services
Your input requested for next Farm Bill
Preliminary downy mildew control trial
Regional reports
Weather news

Ed Grafius
Entomology

Trap catches of European corn borer and corn earworm moths are generally lower than last week (see graphs), but a very significant threat of damage still exists. Because field corn is more mature than usual for this time of year, corn borer and earworm moths (see photo) will be attracted to other, greener crops for egg laying. European corn borer may attack a wide range of crops in addition to sweet corn, including snap beans, peppers, celery, potatoes and tomatoes.

In addition to attacking sweet corn, corn earworm (see photo) may be a serious problem in snap beans and tomatoes (it is also known as the tomato fruit worm) and may attack a wide range of vegetable crops. Corn earworm eggs are laid directly on the silks of sweet corn and larvae burrow directly into the ear, so sprays must be timed to match the time required for egg hatch. If days and nights are unusually warm for this time of year, sprays may need to be applied at 3- or 4-day intervals to get adequate control.

If treatment is needed, Michigan State University Extension bulletin E-312, Insect, disease, and nematode control for commercial vegetables, is available on the web at: http://web4.msue.msu.edu/veginfo/bu lletins/E312/index.htm

Beth Bishop
Entomology

Aster leafhoppers collected from celery fields in southwest Michigan during mid-August had low rates of aster yellows infection. We have found very few aster yellows-infected celery plants in these fields. At this time we recommend using an infectivity rate of 2 to 3 percent. This translates into a treatment threshold of 12 to 17 ALH per 100 sweeps for celery. Celery within two weeks of harvest does not need to be protected from aster yellows since it takes at least that long for symptoms to develop in infected plants.

Aster leafhoppers collected from carrot fields in Oceana and Mason County during mid-August were found to have infectivity rates of 2 to 5 percent. We recommend a treatment threshold of 10 to 20 leafhoppers per 100 sweeps for carrots in this area. Carrots within three weeks of harvest do not need to be treated to prevent aster yellows.

Steven Gower
MSU Diagnostic Services

Several weed species have developed resistance to popular herbicides used in Michigan. There are at least 15 weed biotypes resistant to one or more herbicides in the state. These herbicide-resistant weed species have been documented in field, vegetable and fruit crops, as well as tree plantations and nurseries throughout Michigan.

Confirming herbicide-resistant weeds in Michigan will provide producers with the knowledge to implement the best possible management strategies. The goal of any resistance management program is to prevent or limit the spread of resistant weeds. If you suspect resistance in any weed species and would like to confirm this, seedheads can be collected upon maturity and submitted to MSU Diagnostic Services for an herbicide resistance screen.

The next several weeks prior to harvest are perfect for collecting mature, high quality weed seed. Select plants that were definitely sprayed (not along field edges or sprayer skips). Harvest seedheads by cutting the stem just below the seedhead. Place seedheads into a brown paper bag or collect seed in a small envelope or container. Never seal plants or seed in plastic!

Fees associated with herbicide-resistant weed testing are generally $50 per sample per herbicide site of action (ie: ACCase inhibitors, ALS inhibitors, Photosynthesis inhibitors). Each additional site of action will be $20 per sample. Two exceptions to these fees are horseweed (a.k.a. marestail, Conyza canadensis) and common lambsquarters (Chenopodium album) collected from Michigan soybean fields. These two weeds will be screened for glyphosate, ALS and triazine resistance at no cost to the Michgian soybean producer. All sample costs are covered by check-off dollars through the Michigan Soybean Promotion Committee.

Please contact Steven Gower (517-432-9693, sgower@msu.ed u ) with any questions regarding sample collection. Send samples to:

MSU Diagnostic Services
Attn: Steven Gower
101 Center for Integrated Plant Systems
East Lansing, MI 48824-1311

U.S. Secretary of Agriculture Mike Johanns has sent out the following message asking for input from the public in forming the next Farm Bill:

“Part of my job is to have a vision for the future of agriculture – a vision that results in programs and policies that support today's farmers, ranchers and rural residents as well as the next generation. Although the current Farm Bill does not expire until 2007, the policies that will replace it are already a hot topic of discussion. That's why I've asked America 's farmers and ranchers to tell us how our farm policy is working and how we can make it better. Starting in July, we are conducting a series of Farm Bill Forums throughout the nation. We want to provide the opportunity for the entire agricultural community to have a say in the policy-making process.

I do not begin this discussion with preconceived notions about the outcome, but I do believe it is important to provide some structure to guide the debate. To help us determine the best course for a new Farm Bill, I've asked our stakeholders to answer six questions that I believe get to the heart of farm policy.

How should farm policy address any unintended consequences and ensure that such consequences do not discourage new farmers and the next generation of farmers from entering production agriculture?

How should farm policy be designed to maximize U.S. competitiveness and our country's ability to effectively compete in global markets?

How should farm policy be designed to effectively and fairly distribute assistance to producers?

How can farm policy best achieve conservation and environmental goals?

How can federal rural and farm programs provide effective assistance in rural areas?

How should agricultural product development, marketing, and research-related issues be addressed in the next Farm Bill?

Comments may be submitted electronically via the Internet at the USDA Farm Bill Forums web page: www.usda.gov/farmbill or by sending an e-mail to FarmBill@usda.gov.

We will use the feedback we receive to help us determine the best course for a new Farm Bill. In addition to addressing the six questions, we will also hold specialized listening sessions on other important programs authorized by the Farm Bill such as food assistance and education.”

Preliminary downy mildew control trial

A downy mildew fungicide trial was established with a grower cooperator in a pickling cucumber field that had early symptoms of disease. Thus far, three applications of fungicides have been made at five-day intervals. A preliminary evaluation was made and the treatments are beginning to show important differences. Programs anchored by Previcur Flex + Bravo have the least amount of disease. Tanos + Mancozeb is also performing well.

We will continue to follow this study and take evaluations through the course of the crop development. At this juncture, my recommendation is as follows:

Previcur Flex + Bravo alternated with Tanos + Mancozeb at 5-day intervals.

As an update to the overall disease situation in Michigan, growers who have used the above program and were able to spray early just after symptoms developed, have reported relatively good yields and fruit quality. For fields that were too far gone with disease when these sprays were applied, yields are down and a high percentage of crooks and nubs are reported.

Thus far, there have not been significant reports of either squash or pumpkins with downy mildew, however, we encourage growers of these crops to remain vigilant and use preventive fungicides for as long as healthy vines are needed.

See images
See graph (pdf)

Any grower wishing to report the occurrence of downy mildew, or with questions of whether they have downy mildew, should contact me on my cell phone at 517-927-4532.

Ron Goldy

Weather
Temperatures were near normal for the period ranging from 71 o to 86 oF for highs and 53 o to 66 oF for lows. Precipitation across the area ranged from 1 to 2 inches. SWMREC continues to be below normal with only 8.7 inches of precipitation since March 1.

Commodity reports
Viruses continue to take a toll on zucchini,yellow squash,cucumbers, pumpkins, fall squash,cantaloupe and other cucurbits. The most common appears to be cucumber mosaic. Powdery mildew has defoliated many pumpkin and fall squash fields. Advanced maturity in these fields may not cause field problems, but storage may be a concern. Growers need to protect pumpkin stems from mildew.

Virus symptoms are also present in peppers.

With recent rain and heavy dews, we are finding canker, bacterial spot and bacterial speck in tomato.

Earworm and corn borers continue to be a problem in sweet corn.

Growers are beginning to remove and bale plastic.

Amy Irish-Brown

We are currently running about 14 to 16 days ahead of average for degree day accumulations in the Grand Rapids and surrounding areas.

Potato and aster leafhoppers are present in many different vegetable fields in various stages.

In vine crops, squash bug are less common than in recent years – numbers are very low. Diseases are much more prevalent in vine crops than insects. Mildews – both powdery and downy – are causing decline of all vine crops earlier than we’d like to see. Viral diseases are also common in vine crops.

In sweet corn, a few corn earworms have been reported in the area, but numbers are low. Sweet corn producers with fields that are just starting to silk should have cover sprays on at this time for corn earworm. Cover sprays for corn borer and earworm in late sweet corn plantings might become more of a concern as field corn begins to die down and these insects might move to more favorable sites, like healthy sweet corn plantings.

In general, fungal and bacterial diseases continue to be an on-going problem in many crops, and it seems difficult for growers to stay ahead of the disease in some areas. Downy mildew continues to be a concern in several crops.

Jim Breinling

Weather
We have had generally good harvest conditions during the past two weeks with seasonal temperatures and light rainfall amounts. Most rainfall occurrences have been in the .25 to .30 inch amounts. Fremont official rainfall during the past 15 days has been 0.57 inch, Ludington has received more with .92 inch recorded. Irrigation has resumed in the Newaygo County area especially since no precipitation is in the forecast for the next week.

Commodity reports
Carrot harvest continues at a steady pace in Newaygo County . Quality is reported to be good. A couple of fields of early processing carrots have also been harvested. Irrigation systems are operating again in carrot fields.

Onion harvest began during the week of August 15 and is now in full swing.

CMV is widespread in snap bean fields. Fields sampled in early August tested positive for CMV are now at normal harvest maturity date. The pod set in these fields is very light. ECB trap counts this week (August 30) were 4-0-0. CEW trap catch on August 30 was nine moths.

Vine crops continue to be threatened by viruses and downy mildew. The hard winter squash seem to be maturing despite the viruses and not yet effected by downy mildew. Harvest of butternut for processing has begun this week as demand for the crop is high. I have seen a field of slicing cucumber in Newaygo County that is severely infected by downy mildew.

Hannah Stevens

Weather
While dry conditions are not as much as an issue at this time with late crops being harvested, late cole crops, beans and others could use more rain. One to 2 inches of rain on Saturday was excellent but brings the total for the entire month of August to only 1.7 inches in central Macomb . Heavy dews and high humidity are putting heavy foliar disease pressure on many crops.

Commodity reports
Worm pressure in sweet corn has been high for European corn borer and corn earworm. Heavy flight of corn borer began two to three weeks ago with corn earworm following closely behind. Both earworms and corn borers can be found in or near the tips and corn borers in the sides or butt of the ear. The entry holes in the husks may be very small and hard to detect. The Bt varieties are naturally much cleaner (although not 100 percent) and growers who have not moved into those varieties are anxious to do so. Supplies of corn are lower now that the compressed harvest is over but there still seems to be enough corn for the retail market. The new SE and Sh2 varieties are very pleasing to consumers.

Many late cucurbit crops are suffering from low fruit set and virus symptoms. The fruit set may be from a combination of very hot weather leading to a reversion of the crop to male blossoms as well as virus pressure which is, in some cases, causing a severe blight. In some cases the foliage looks healthy but fruit is either absent or may be showing the typical mosaic coloration. Melon and watermelon have been of good yield and quality this year, as were early summer squash. However, the late crop of squash is struggling.

The condition of peppers is variable. In some plasticulture fields I have observed tremendous yield and quality. However there are virus symptoms in the crop, both foliage and fruit, particularly in jalapeno. The virus identity has yet to be confirmed.

Virus is severe in many snap bean fields with very low marketable yield.

Bacterial symptoms are not severe in tomato fields I have seen but significant enough to warrant copper applications along with necessary fungicides. Quality is very good this season.

Jeff Andresen
Agricultural Meteorology
Geography

Wednesday morning (August 31), the remnants of Hurricane Katrina were over northwestern Pennsylvania and moving northeastward and away from Michigan, setting the stage for a mostly fair and dry forecast through the upcoming Labor Day weekend. A frontal boundary will move from west to east across the state Thursday, but given almost no moisture in place over the region, will bring only some clouds and a few scattered showers or sprinkles to northern sections of the state. High pressure will move in behind the front, leading to fair and dry weather statewide Friday through at least Monday and possibly into the middle of next week, when the next weather system approaches from the west.

High temperatures will range from the mid- and upper 60s far north Thursday to the low 80s south and continue at those levels through Monday. Low temperatures will range from the mid- and upper 40s north to the mid- to upper 50s south. Medium-range forecast guidance calls for a basic continuation of the pattern currently in place across North America with weak troughs across the Pacific Northwest and New England, and a broad, weak ridge across the Upper Midwest. This ridge will likely lead to more warmer than normal temperatures in the next one to two weeks.

The NOAA Climate Prediction Center6-10 day and 8-14 day outlooks, covering September 5-9 and 7-13 both call for above normal temperatures state- and region-wide. Precipitation totals are forecast to range from below normal levels in southeastern sections of Lower Michigan during the 6-10 day time frame to near normal elsewhere and at near normal levels statewide during the 8-14 day period.