The first seasonal flight of European corn borer moths is still occurring in most of Michigan. Corn borer moths were captured in pheromone traps during the period of June 13 to 20 (see graphs). Many sweet corn fields are now vulnerable to corn borer damage. Growers should protect any fields with developing ears. When corn borers hatch, they feed very briefly on the plant surface before boring into the plant. Once inside the plant (most often the ear or the fruit of peppers and snap beans), corn borers are protected from insecticides. Growers must target the newly hatched larvae. This means keeping the plant surface treated with insecticides. During periods of very warm weather, plants are growing quickly (producing lots of unprotected foliage) and spray intervals must be shortened.

Another critical period for corn borer control in sweet corn is tassel emergence. Corn borers commonly feed in the whorl and when the tassel emerges, they migrate to developing ears. Look for larvae, feeding damage and frass in the whorl leaves. Insecticide application may be required to prevent larvae from burrowing in the ears. See previous issues of the Vegetable CAT Alert for more details.

The latest aster leafhopper test results for aster yellows infection are shown in the accompanying table. Very low infectivity rates are still being found in aster leafhoppers from celery fields in southwestern Michigan. Higher infectivity rates are still occurring in leafhoppers from carrot fields in west central Michigan. The recent weather patterns are favorable for bringing new insect immigrants into the state. Growers should check fields for insect pests such as potato leafhoppers and aster leafhoppers.

It has been a relatively quiet week with no new cases of downy mildew found. The two cucumber fields with downy mildew have not been destroyed and will likely be in production for the next four weeks. We are working to determine the threat that these fields pose to the cucumber and cantaloupe producers in the state. The diseased fields have been under an intensive fungicide program to keep the downy mildew limited.

The downy mildew pathogen moves from field to field primarily via air currents. It reproduces via tiny, microscopic spores that act as seeds of the pathogen. Spore traps have been placed in one of the diseased cucumber fields and also in four other Michigan counties: St. Joseph, Allegan, Bay, Van Buren and Monroe.

These traps are research tools that are manufactured in England and cost approximately $5,000 to $6,000 each. Inside of the trap there is a drum that has a cellophane tape with a sticky surface. This tape rotates past an intake orifice at the rate of approximately 2 mm per hour. Anything in the air that flows past the cellophane tape becomes embedded in the sticky material on the tape and includes spores, pollen, insect parts, debris, etc. At the end of 7 days, the cellophane tape is removed from the drum, cut into 24mm segments and is mounted onto a microscope slide. A compound microscope is needed to have enough magnification to identify any downy mildew spores that may be present on the tapes. The spore traps will help to alert us to any influx of spores into those production regions. These traps cannot be used as a substitute for the fungicide sprays. Since we do not have a trap in each field, it is possible that we could miss an isolated spore mass coming into a particular region.

Are fungicide sprays still needed? Yes. Many cucumber and cantaloupe growers have now applied two fungicide sprays and have protection through this week. At this juncture, I recommend that growers continue with the same fungicide program. The recent series of rains will be favorable for downy mildew development.

Alternate these sprays:
Previcur Flex (1.2 pint) + Bravo (or Mancozeb)
Tanos 50DF (8 oz.) + Mancozeb (or Bravo)

Growers of cucumbers or cantaloupes in southeast Michigan region should be on a 5-day alternation program. Growers in the rest of the state should be on a 7-day alternation program. If Previcur Flex is not readily available, two Tanos 50DF applications may be made in a row prior to changing up the spray program with Previcur Flex. The fungicides will be more effective when applied prior to the appearance of downy mildew. Tanos 50DF has a 3-day PHI and Previcur Flex has a 2-day PHI. The addition of Mancozeb increases the PHI to 5 days. Bravo has a 0-day PHI.

Some later planted fields may be covered with a banded application of fungicide. As further sprays are needed, cost becomes difficult to bear. However, with downy mildew present in the state and the weather providing the moisture needed for the disease, I do not think that we have a choice. Fungicides must be applied preventively and frequently.

Downy mildew causes symptoms on leaves that include angular yellow lesions and brown, dead leaf areas (Figure 1). The tell-tale symptom of downy mildew is the dark, purplish/gray fuzz on the underside of the leaf, giving a somewhat “dirty” or “velvety” appearance (Figure 1). This fuzz, which is the accumulation of spores, may be most evident in the morning. Leaves of all ages can become infected, including cotyledons.

As fields are scouted for downy mildew, it is important to know that there are other diseases and leaf injuries that can look similar to downy mildew.

Look-alike diseases: Angular leaf spot can produce symptoms of angular yellow lesions that are often shiny on the leaf surface due to dried bacterial ooze (Figure 2A). Anthracnose, caused by a fungus, produces tan spots on leaves which die and fall out, resulting in a shot-hole appearance. Neither of these diseases produce spores or a “dirty” appearance on leaf undersides.

Look-alike leaf injuries: Herbicide damage can give leaves the appearance of both yellow mottling (Figure 2B) and brown lesions with dead areas which fall out of the leaf, appearing tattered (Figure 2C). Heat stress can also affect leaves, resulting in pale to white spots visible on leaf surfaces (Figure 2D). Heat stress is particularly a problem on plants that were grown under plastic tunnels and may have experienced extreme temperatures. Many Michigan cucumber fields have had cucumber beetle activity during the last 2 weeks. Beetle feeding on leaf undersides can result in the appearance of yellow to brown leaf areas, and when feeding damage is fresh, damaged leaf undersides can look dark green and wet. None of these leaf injuries result in the appearance of “dirty” leaf undersides.

Now available from the MSU Extension Bulletin office: Identifying Natural Enemies in Field Crops, MSU Bulletin inventory number E2949. The cost is $10 per copy, $7 per copy for bulk orders (10 or more copies). (view image) Contact the MSU Bulletin office to order:

117 Central Services
Michigan State University
East Lansing, MI 48824-1001
Phone: 517-353-6740
Fax: 517-353-7168
Office Hours: M-F 8:00am - 5:00pm
http://www.emdc.msue.msu.edu/

Additional information and sample pages from the flip book are at: http://www.ipm.msu.edu/pubs-natural.htm

During last year’s soybean aphid outbreak, I received numerous questions about beneficial insects. Beneficial insects play a critical role in managing soybean aphid populations (I’ve already seen ladybeetles cleaning-up aphid colonies on buckthorn this spring). And populations of many other field crop and vegetable pests are kept in check or reduced by natural enemies. This timely pocket guide (developed by Mary Gardiner, a graduate student in the MSU Biological Control Lab) has color pictures of common beneficial insects – both predators and parasitoids – and spiders. It provides information on identification, lifecycle and diet. The pocket guide has glossy pages and a spiral binding, so you can use it in the field. Although it is geared for field crops, it is appropriate for use in other crops and by homeowners. If you plan to attend the MSU Diagnostic Day on July 21, you will receive a copy of this guide, as we will use it as part of a session on soybean aphid biological control.

Farmers, educators and families are invited to Michigan’s largest agricultural equipment exposition July 18-20 when the 27th annual Ag Expo takes place at Michigan State University (MSU).

The exposition will feature a skid-steer ride and drive, zero-turn mower demonstrations, utility vehicle ride and drives, livestock handling demonstrations, an antique and garden tractor pull (July 19 only), a toy tractor show and an FFA tractor driving contest.

More than 250 commercial exhibitors, including equipment, seed, fertilizer, building and service suppliers will be on site. Visitors can expect to see tractors, implements, trailers and other equipment, and can talk to representatives from manufacturers, dealers and agencies.

“This year’s Ag Expo will offer visitors the opportunity to see new equipment and demonstrations, and we’ve brought back the popular toy tractor show along with a tractor pull event,” says Kirk Heinze, Ag Expo director.

Ag Expo will also feature a number of educational exhibits from MSU colleges and departments. The College of Agriculture and Natural Resources will host a tent with displays and information from the Michigan Agricultural Experiment Station, the MSU Land Policy Program, the Animal Science Department, Project GREEEN (the plant industry initiative at MSU), 4-H Youth Development, and the IPM Program.

Ag Expo features commercial farm equipment from throughout the Midwest and several Canadian provinces on the 35-acre main exhibition site and the 40-acre field demonstration area.

The event runs from 9:00 AM to 4:00 PM, July 18, 8:00 AM to 7:00 PM July 19, and from 8:00 AM to 3:00 PM July 20. Admission to the grounds and parking at Farm Land and Mt. Hope Road are free.

For more information about Ag Expo, call 800-366-7055 or visit www.agexpo.msu.edu. Ag Expo is sponsored by the MSU College of Agriculture and Natural Resources.

Regional reports
1 -- Southwest
Ron Goldy

Tomato staking and tying continues. Plants range from newly set to having 2-inch diameter fruit.

Stakes are being set in pepper plantings. Side shoots continue to develop nicely.

Potatoes are in full bloom. Significant Colorado potato beetle populations can be found on horse nettle, so growers should pay close attention to fields not previously protected

Harvest volume is increasing from tunnel-grown, transplanted zucchini and yellow squash. Non-tunnelled plantings will be harvested soon. Tunnel-grown cucumber harvest should begin this week. Watermelon and cantaloupe transplants are runnering off the plastic and are in early bloom.

Cutworm damage can be found on pumpkins.

3 -- Oceana County
Norm Myers

Commodity reports
Most asparagus growers will be finished with harvest this weekend. The last processor shuts down early next week, but there will be a little fresh picked through next week. Growers are fertilizing and applying herbicide as weather allows. Rust and common asparagus beetle are common on developing fern.

On carrots, aster leafhopper numbers are generally low. Growers are still finding stunted plants with dwarf root systems. A sample has been sent to the MSU lab.

Seed corn maggot problems reported in some fields of vine crops. Pickles are only now getting near the size where we should spray them for downy mildew. There has been some herbicide damage in fields from the heavy rains.

4 -- Mason-Newaygo counties
Jim Breinling

Weather
Rainfall is the weather topic again this week. General and heavy rainfall amount on Sunday, June 18th in Mason County ranged from 2 to 5 inches. Official amount at Ludington MAWN Station was 2.41 inches. Many reports of 3 to 3.5 inches in most of vegetable production area. Just the opposite in Newaygo County with .35 inch in Fremont and less reported in Grant. Temperatures variable during the week with above normal temperatures over the weekend.

Commodity reports
First planting of carrots with ¼ to 3/8 inch diameter roots and 10 to 12 inch tops. Aster leafhopper counts generally remain low.

First onion plantings at 5th leaf 10 to 12 inches in height with ¼ to 3/8 inch diameter bulbs.

Spinach harvest will be completed in our area this week.

Vine crop growers were alerted to occurrence of downy mildew in southeast Michigan.
Striped cucumber beetles very numerous in plantings not treated with soil insecticides.

Winter squash plantings are at 3-4 leaf stage.

Snap bean plantings where European corn borer (ECB) traps are located are at first trifoliate stage. ECB counts were up considerably this week with 27-1-195.

Corn earworm trap placed in sweet corn planting in Mason County this week.

5 -- Macomb, St. Clair and Lapeer counties
Hannah Stevens

In squash, melons and cucumbers, striped cucumber beetles are now active. Much of the crop is in flower so growers should be timing sprays and selecting products to avoid poisoning hives and wild bees. Some row covers are still in place but many have been removed. No reports of downy mildew have come in from this area.

Carrots and onions on muck ground look excellent.

Tomatoes are being tied. The pepper crop is progressing well.

Some early cabbage is being cut while much of the crop is beginning to head. Flea beetles have been a problem on the crucifers, including greens. No serious worm problems have come to my attention.

Beans are beginning to flower and control has been necessary for potato leafhopper as grasses dry.

6 -- Monroe County
Paul Marks

Sweet corn is tasseling in many fields that were planted without the aid of plastic. Corn borer trap counts this week averaged 26, down by 50 percent for the third week in a row. Both eggs and small larva are now found in our fields. Corn earworm adults have not been caught yet.

Cucumber and other vine crops have made tremendous growth with adequate moisture and warm conditions. Pumpkins are ready to begin tipping in many fields. Cucumber beetles continue to ravage unprotected cucurbits. Downy mildew is still limited to one field.

Potatoes are progressing nicely with tuber bulking in early fields and final emergence in the latest fields. Leafhoppers have increased to a point where some fields have now reached threshold for the second time this year. First variegated cutworm adults of the season have been in my traps this week.

Weather news
Jeff Andresen
Agricultural Meteorology
Geography

A fast zonal (west to east) jet stream pattern across the northern U.S. will lead to relatively active weather for the next couple of days. Fair, cooler and drier weather will follow this weekend as a troughing pattern develops across the Great Lakes region. In the short term, the frontal boundary that moved through the state last Sunday (June 18) will approach the state from the south as a warm front Wednesday before temporarily stalling out over southern sections of the state. Combined with a strong upper air disturbance approaching from the northwest and large amounts of Gulf of Mexico moisture from the south, showers and thunderstorms are a good bet over much of the state Wednesday. Depending on how much sunshine is available, some severe thunderstorms are possible, with damaging high winds and hail being the primary threats. Chances for severe weather and the likelihood of rainfall will be greatest across southern sections of the state decreasing northward.

Showers and a few thunderstorms will be possible once again Thursday, primarily across southern sections of the state. Fair and dry weather is expected to develop by Friday statewide and continue through the majority of the upcoming weekend as high pressure moves into the region. Rainfall totals during the next 5 days are projected to remain generally within the quarter to a half inch category, with some 1 inch totals possible across southern sections of the state.

Temperatures will fall from high temperatures Wednesday ranging from the upper 70's far north to the low and mid 80's south back to the 70's to near 80 by Friday continuing through the weekend. Low temperatures will generally range from the 50's north to the 60's south Through Thursday morning, falling back to the mid 40's to mid 50's during the weekend. Overall temperatures during the next 5 days are forecast to generally average 2-4 degrees below the normal. Following a dry weekend, rainfall will be possible once again by next Tuesday as a weather system approaches from the west.

Medium range forecast guidance strongly suggests the establishment of a large upper air ridge across the southwestern U.S. with a troughing feature across the east, which would keep Michigan under the general influence of northwesterly flow aloft in a somewhat benign weather pattern. The 6-10 day and 8-14 day outlooks (covering the 26th-30th of June and the 28th of June through the 4 th of July, respectively) are very similar, calling for near normal temperatures statewide and for below normal precipitation totals. Given good agreement among the various forecasting tools, forecaster confidence in these outlooks is considered greater than normal for the time of year.