July 23, 2008
In this issue
§ Western bean cutworm: a new corn “worm”
§ Aster leafhoppers and aster yellows
§ Watch for tarnished plant bug
§ Recent foggy, humid weather favors downy mildew
§ Potato disease update
§ Starane Ultra labeled for onions in Michigan
§ Informational meeting on new water use legislation
§ Agricultural field sanitation requirements in Michigan
§ Regional reports
§ Weather
Next issue July 30
Beth Bishop
Entomology
Numbers of European corn borer moths captured during July 15 - 22 are still very low, but should increase soon as the second flight begins. Also, very few corn earworm moths were captured last week. Although the risk from these pests to sweet corn, peppers, snap beans and tomatoes is low, another “worm” pest has appeared.
Western bean cutworm has been a pest in the western
For detailed information on western bean cutworm identification and biology, consult the Field Crops CAT Alert. To summarize, there is one flight, or generation, each year, which usually begins in early to mid-July and continues until mid-August. Females are attracted to corn in the whorl to pretassel stage. Eggs are laid in clusters on the upper surface of leaves. Eggs are white when first laid, but turn purple before hatching. European corn borer egg masses are white at first, but flat, resembling fish scales, unlike the rounded eggs in a western bean cutworm egg mass. Upon hatching, larvae feed on the tassel in the whorl and after the tassel emerges move down to the silk. They feed on the silk for a while and then enter the ear. Unlike corn earworm, the larvae are not cannibalistic, and there can be many western bean cutworm larvae in a single ear.
Sweet corn growers in areas where western bean cutworm are flying should be scouting their fields for egg masses. Check the upper leaves of 20 plants in five different locations in the field. Be sure to check different varieties and corn at different growth stages. Chris DiFonzo has recommended a threshold for field corn of five percent of plants with egg masses. However, the tolerance for worms in sweet corn is considerably lower. Growers with silking corn should already be on a preventative program for European corn borer and corn earworm. However, remember that western bean cutworm prefers corn at the pretassel stage. If western bean cutworm egg masses are found in sweet corn at the whorl or pretassel stage, an insecticide should be applied at tassel emergence. Western bean cutworm larvae are difficult to control when in the silk and impossible to control once in the ear, so insecticides must be timed to tassel emergence. A number of insecticides are registered on sweet corn for control of western bean cutworm, including pyrethroids (Asana, Capture, Baythroid, Mustang Max, Proaxis, Pounce), organophosphates (Lorsban, Penncap-M), Sevin, etc.
Western bean cutworm is not controlled by most varieties of Bt sweet corn. It is also a pest of dry beans, but that crop is less preferred. I have not heard of any reports of western bean cutworms on snap beans, although that is always a possibility later when the population increases and corn becomes less attractive.
Beth Bishop
Entomology
The proportion of aster leafhoppers carrying aster yellows remains moderate. The latest test results from MSU Diagnostic Services indicate that the infectivity rate has decreased in many locations (see table). Because of the variability in infectivity rates, a range of conservative treatment thresholds is suggested.
|
Location and crop |
Date collected |
Infectivity |
Threshold (ALH per 100 sweeps) |
|
|
7-14 |
3.7 % |
8-12 |
|
|
7-10 |
0% |
25 to 35 |
|
|
7-8 & 7-10 |
5% to 10% |
4 to 7 |
|
|
7-9 to 7-14 |
0% |
25 to 35 |
|
|
7-9 & 7-16 |
2.7% |
10-12 |
Beth Bishop
Entomology
Tarnished plant bugs have been invading many vegetable crops, probably as a result of nearby alfalfa fields being cut. Tarnished plant bugs feed on a variety of crops, including many vegetables. In most crops they prefer feeding on flowers and fruit, but can also feed on the tips of asparagus fern, celery petioles and lettuce leaves. Adults are very mobile and can move in and out of fields before they are detected. Tarnished plant bugs have sucking mouthparts and insert a toxic saliva into plants while feeding. They can cause tip die back in asparagus, flower drop in peppers, snap beans and tomatoes, brown, sunken feeding scars or stings in lettuce and celery.
Treatment thresholds have not been established in most crops
for tarnished plant bug. In celery,
Tarnished plant bugs are effectively controlled by a number of insecticides, including pyrethroids, neonicitinoids, and carbamates. Consult bulletin E312: 2008 Insect, Disease, and Nematode Control for Commercial Vegetables for insecticides registered to control tarnished plant bug on your crop.
Mary Hausbeck
Plant Pathology
The wet, foggy and humid weather that occurred over the weekend and extended through the early part of this week will cause downy mildew to increase rapidly and spread. This year’s weather is much more favorable for downy mildew than what we experienced last year. That means that if you were able to control downy mildew on cucumber last year by spraying every 10 days you should not assume that the same approach will work this year. Since the weather is cooler and wetter than last year, fungicide sprays will need to be applied to cucumber more frequently than every 10 days in order to adequately control downy mildew. It is currently recommended that all cucumber growers apply a fungicide at least as often as every seven days. For cucumber growers who find downy mildew in the field, the sprays will need to be tightened up to five-day application intervals.
At this point, there have not been additional fields found
with downy mildew beyond those identified earlier in Monroe and Allegan
counties. However, given the increasing spore counts as determined by the spore
traps, cucumbers in other fields or in homeowner gardens must be infected with
downy mildew, but are not being reported. Updates on the movement of downy
mildew in
We have received some cucumber samples with downy mildew-like symptoms, but found alternaria leaf blight only. We welcome all samples that appear to have downy mildew-like symptoms. We can look at the leaves under the microscope and determine within a few minutes whether there is downy mildew. In some cases, we can arrange to pick up the samples if the location is near the spore trap sites.
Given the extremely favorable weather for downy mildew and the increasing spore counts in some areas of the state, all melon growers should be certain to be using downy mildew fungicides at a spray interval of every 10 days. Melon growers in Monroe and Allegan counties should consider downy mildew fungicide sprays every seven days since the disease is present in those counties and the weather has been very favorable for disease. In previous years, melons have become infected with downy mildew, ranking second behind cucumber in susceptibility to the disease.
I’ve had a lot of questions about how to use the new fungicides Presidio and Revus. Presidio can be used for both downy mildew and Phytophthora crown and fruit rot. The label for Presidio specifies that another fungicide needs to be mixed with Presidio. When using Presidio for control of downy mildew either Bravo of Dithane can be used as a mix partner. When using Presidio to target Phytophthora crown and fruit rot, fungicides such as Gavel or Acrobat can be considered as tank-mix partners. Revus is best used for control of Phytophthora. While I do not think that Revus is one of the top downy mildew fungicides that we have available, it is a good choice for Phytophthora control.
Squash, pumpkin, and zucchini growers can continue to use downy mildew fungicides every 10 days, but should be scouting fields for any early downy mildew infections. In the last few years, downy mildew has not been an especially difficult problem in squash, pumpkin, or zucchini fields.
Melon, pumpkin and squash growers need to remember that powdery mildew has also been found in the state and will need to be scouted and treated. The products used to treat powdery mildew are different than those used to treat downy mildew. So, those growers who are on a downy mildew program will need to make adjustments in their spray program to be protected from both downy mildew and powdery mildew.
Willie Kirk
Plant Pathology
The main diseases to appear in
Foliar diseases such as early blight and brown leaf spot are
starting to appear now and first reports of early die. Growers have been
challenged by frequent rain this year and conditions have been ideal for late
blight in many areas, especially the southwest and southeast growing areas of
Full recommendations for management of these diseases and
others can be found at http://www.potatodiseases.org/index.html.
Daily updates of potato late blight risk are available at http://lateblight.org for all the MAWN sites
in
Bernard Zandstra
Horticulture
The Michigan Department of Agriculture has approved an SLN
(Section 24c) label for use of Starane Ultra (fluroxypyr) on dry bulb onions in
To control broadleaves, apply 0.35 pt of Starane Ultra to weeds less than four inches tall. Please note that only the new formulation of Starane Ultra, which is a 2.8 lb ae/gal formulation, is labeled for onions. The original formulation, Starane 1.5 lb ae/gal, is not labeled for onion. Volunteer potatoes should be four to eight inches tall for optimum control.
Application to onions may be made as a broadcast over the top spray from the 2- to 6- leaf stage. After the 6-leaf stage, Starane Ultra should be applied with drop nozzles as a directed spray. Do not use an adjuvant with Starane Ultra on onions.
For heavy weed infestations, make two applications 10 to 14 days apart. Do not exceed two applications per year. Do not apply within 42 days of onion harvest.
Applicators must have a copy of the label when making applications. The label can be printed from the MSU vegetable website: www.veginfo.msu.edu.
Attend one of these informational meetings during August to better
understand the new water use legislation signed into law by Governor Granholm
on July 9, 2008. There are four locations to choose from:
August
13 9:00 AM to Noon
August
18 9:00 AM to Noon
Tuscola ISD/Technology Center,
August
21 9:00 AM to Noon
Kalamoazoo,
August
22, 9:00 AM to Noon
MSU Extension Office,
For more information, contact Lyndon
Kelley at 269-467-5511 or Steve Miller at 517-353-4456
A pdf of this information is available at www.ipm.msu.edu/cat08veg/pdf/7-23wateruselegislation8-08.pdf.
Vera Bitsch
Agricultural, Food, and Resource Economics,
The Michigan Occupational Safety and Health Administration (MIOSHA) has updated enforcement procedures for field sanitation standards in 2008. Inspections may be based on complaints or referrals, as well as, programmed inspections, which are conducted by MIOSHA personnel as time permits where they see hand-labor operations in the field.
Clean and safe potable water must be readily accessible to all employees. Heat-related illness can be reduced or prevented by drinking enough water and taking other precautions, including suitable clothing. Farm workers experience the highest risk of heat-related illness of all occupations.
Where 11 or more employees have worked on any day during the last 12 months, the water must also be suitably cool for the temperature conditions and dispensed by single-use cups or by fountains.
Toilet and hand washing facilities must be provided whenever work time plus transportation time to and from the field exceeds three hours. One toilet and hand washing facility shall be provided for each 20 employees or fraction thereof. The facilities shall be located together and as close as practical to the work location.
For small operations, where the 11 or more employees rule does not apply, the facilities must be either provided as above or available to employees by using employer furnished transportation.
Employees must be given reasonable opportunity to use these facilities. Toilets shall be ventilated and screened, have self-closing doors lockable from the inside, and constructed to ensure privacy. Toilets shall be operational and include an adequate supply of toilet paper. Hand washing facilities must have an adequate supply of potable water, soap, and single-use towels.
All facilities must be maintained in clean and sanitary conditions and waste shall be disposed in a sanitary manner. Where the 11 or more employees rule does apply, employers must inform all employees about the importance of good hygiene practices to minimize adverse health effects.
More information is available at www.michigan.gov/miosha,
and by calling the MIOSHA General Industry Safety and Health Division at
517-322-1831 or the district supervisor at 616-447-2650. Free consultation and
compliance assistance is available through the MIOSHA Consultation Education
and Training Division (CET) by calling the
To read Dr. Bitsch’s complete newsletter go to her website
at http://www.msu.edu/user/bitsch.
Under “News” click on “Agricultural Field Sanitation” or click on “Agricultural
Labor Issues in
Ron Goldy
Temperatures have been near normal for the period with lows from 60°F to 69°F and highs from 72°F to 89°F. There was 1.5 to over 2.0 inches of rain across the area. High rainfall has made it difficult for field activity in some fields.
Sweet corn harvest volume has increased as more fields come into production. Some fields are showing signs of rust and smut, and tassel feeding born corn borers. Aphids are present in some fields.
Tomato harvest continues with volume also increasing. Hornworm and fruit worms can be found in some fields.
Phytophthora symptoms can be found in pumpkin and fall squash fields. Otherwise plants are growing and runnering well. Early cucumber, zucchini, and yellow squash fields are finished and are being removed with some being replanted. Early virus symptoms are showing up.
Cantaloupe harvest began this week. Watermelons are continuing to size well with harvest at least two weeks away.
Peppers and eggplants continue to grow well with few problems. Harvest is also about two weeks away.
Tarnished plant bugs are present on many crops.
There will be an open house for the High Tunnel system July 31 from 7:00 PM to 9:00 PM at SWMREC.
Bill Steenwyk
Rainfall for the past week varied from less than 0.1 inch in
Belding to one or more inches south of
Celery is being harvested steadily, with the early crop down about 20 percent from normal. On individual farms, yields range from excellent, to nearly nothing where earlier flooding damage was severe. Fusarium blight is present in a number of fields.
Some onion fields
look very good with bulbs sizing beyond two inches. I saw one field where the
leaves have dropped. The early June floods, followed by repeated wet periods
have produced bacterial blight in a number of west
Sweet corn harvest has just begun. No major problems are being reported. Cabbage harvest continues at a good pace. The tomatoes and peppers that I have seen look good, and no reports of problems have come in. The have been reports of phytopthora in some of our vine crops.
Growers should go to www.ipm.msu.edu/cat08veg/pdf/7-23buyinwaiver08.pdf to see a copy of a new USDA announcement entitled "2008 Crop Year Buy-in for Disaster Assistance Programs". This describes how growers have been given extra time to go to their county USDA Farm Service Agency office to purchase "catastrophic risk protection" insurance (CAT), or "Noninsured Crop Disaster Assistance Program" coverage (NAP), to be eligible for USDA crop disaster funds. The cost is $100 per crop, but not more than $300 per producer per county, or $900 total per producer, for all counties, less any previously paid fees for CAT and/or NAP. Contact the local USDA, FSA office for full details.
Norm Myers
Weather has continued to be dry this last week and irrigation is underway where it is available.
The first flush of fern on full season asparagus fields is now fully expanded. Most growers have put down their first fungicide cover. Purple spot and rust are both active and TOM-Cast sensors are building Disease Severity Values quickly because of the foggy mornings.
In carrots, foliar diseases continue to be a big concern in these weather conditions. Some aster yellows are beginning to show up now and aster leafhopper numbers are rising.
Harvest of processing
zucchini is under way. Growers are treating for powdery mildew as needed. Cucumber
beetles are still a big problem in many fields. Powdery mildew is also
beginning to show up on most pumpkin
fields. Unfortunately, we had our first virus case confirmed by MSU Diagnostic Services with both
zucchini yellows and watermelon mosaic type II identified. This isn’t too
surprising since Dr. Chris DiFonzo found winged soybean aphids in
Summer snap bean plantings appear to be growing normally in most areas.
In sweet corn, European corn borer traps were up just a little, but this is the first week that I caught zero corn earworms. Western bean cutworm flight has been way up with one trap catching 103 moths in a week. Egg masses were over threshold on the two field corn sites I scouted, but not on the sweet corn field I scouted.
Jim Breinling
Temperatures continue about normal with highs averaging about 80°F and lows in the low to mid-60°F range. Even though rainfall amounts were low, the humidity levels remained high during the week. Actual rainfall recorded for the week was 0.69-inch at the Ludington Enviro-weather station with most of that measured on July 16. At Fremont only 0.15-inch was reported, but during the week, however thunderstorms formed in the area on July 22, and about 0.25-inch was reported in the Grant area.
Even though incidence of leaf blight is reported, foliage of
carrots in
Onions continue to progress and bulbs are sizing at one to one and a half inches in diameter. Growers report normal insect and disease pressure with crop development possibly a little behind normal at this time due to the cold early season temperatures.
In cucurbit crops, slicing cucumber harvest began this week. Butternut and other winter squash for processing are growing well with first bloom appearing. Striped cucumber beetles were observed in some bloom. Irrigation is being applied at this time on a number of the squash fields. Pumpkin fields in the area are now well established and starting to grow well.
Local sweet corn
is now available in
Snap bean fields
in
Hannah Stevens
Having been out of the area for a couple weeks, I returned to find that many crops were being harvested and others were nearing harvest. The weather has been dramatic in the past few weeks varying from hot and muggy conditions in the low 90s, to a relatively cool 80°F maximum yesterday. However, many areas have experienced rainfall every day this week with total amounts ranging from a trace, to nearly four inches. Several farms were hit with destructive hail and high winds on the evening of July 16.
The new potato crop for the retail market is well underway and is of excellent quality.
Growers are continuing to plant late cole crops. Cabbage and broccoli greens are being harvested.
In sweet corn, the corn borer numbers are very low and growers have been lengthening spray intervals. I noticed a lot of foliar feeding several weeks ago and where sprays were not applied I expect there will be worms in the first ears. It has been a tedious wait for the first harvest, somewhat like watching paint dry, as one grower remarked. This weekend should see the first local harvest of bare soil sweet corn. Plasticulture corn has been on the retail market for about 10 days.
Zucchini and cucumber harvest is in full swing. Muskmelons are beginning to set fruit and watermelons are sizing. Pumpkin and hard squash are beginning to set fruit and fill the rows. Most growers are protecting the crops from fungal diseases, including downy mildew. Anthracnose has been identified on cucumbers in a home garden.
Sudeep Mathew
It was dry during the past week. Humid conditions have
provided favorable environments for disease development and spread. The Enviro-weather
station near
Sweet corn is silking in many fields and harvest is going on in early planted fields. There was some fall armyworm feeding on harvestable sweet corn ears.
Japanese beetles are everywhere. They are present in the fields of sweet corn, cucumbers, peppers and tomatoes. There weren’t any European corn borers or corn earworms found in our traps in the past week.
Cucumber picking is taking place. All the commercial growers are on a continuous spray schedule to restrict further spread of downy mildew. Cucumber beetles (Photo 1) are present in many fields in moderate numbers. Pumpkins are growing steadily. Cantaloupe and melons are being harvested this week. There were few corn borer-type injuries on mature melons and cantaloupe fruits. I found one squash vine borer in the trap.
Cabbage harvest is in full swing. I have seen sclerotinia (white mold) symptom on fully formed heads of cabbage (Photo 2). Cabbage planting is continuing on the fields where sweet corn is harvested. I have learned from many growers that it will continue beyond this week.
Green bell peppers and Hungarian peppers are maturing for harvest. European corn borer feeding was evident on some green bell peppers.
Harvest of market tomatoes began this past week. I saw symptoms of bacterial speck and spot (Photo 3) in the vines of the staked tomatoes. Processing tomatoes are looking good although many plants lost some flowers during the cool nights of this season.
Potatoes are
growing well with green vines and completing canopy closure. There is not much
disease pressure at this time.
Jeff
Andresen
Agricultural Meteorology
Geography
A nearly stationary frontal boundary across the eastern
High temperatures Thursday and Friday should range from the low 70s far north to the low 80s south with lows in the 50s into the low 60s. Similar temperatures are expected this weekend, with highs from the mid-70s north to the low 80s south and lows from the mid-50s south to low 60s far south through Sunday. Further ahead, high pressure is forecast to dominate weather across the region early next week, with fair and slightly cooler than normal conditions expected.
In the medium range period, forecast guidance suggests upper
air troughs across northwestern and northeastern sections of the