It is astounding how many new reports of downy mildew have been made from important cucumber growing regions in the last three days. Several fields in Ohio are now showing symptoms although the fungicide program is keeping the disease in check. Ontario is not faring as well. They are experiencing an outbreak that is not being controlled. It seems they do not have the same effective fungicide tools that United States growers have. Further, Delaware has now reported the first occurrence of downy mildew in that state. To my knowledge, cucumber is the only crop that has been reported with downy mildew.

In Michigan, downy mildew was confirmed on July 7 in a 35-acre cucumber field in Monroe County. This report added to the reports last week of downy mildew on cucumbers in northeast Ohio and Ontario. Surely, the period of extended wet, humid weather that occurred approximately two weeks ago has played a key role in these new outbreaks.

Currently, the newly identified 35-acre cucumber field in Michigan has a very low level of downy mildew because of a good fungicide program (only two infected leaves could be found). This farm is relatively close (2 to 3 miles) to the Michigan farm with the earlier downy mildew outbreak.

What to look for
Downy mildew causes symptoms on the leaves similar to a mosaic or angular leaf spot. 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 (see picture). This fuzz may be most evident in the morning. Leaves of all ages can become infected, including cotyledons.

What to do if you think you have it
Contact your local MSU Extension office immediately. All samples must be examined by someone in my laboratory or by Dr. Jan Byrne in the MSU Diagnostic Services for downy mildew to be confirmed.

Based on MSU trials from last year, Previcur Flex and Tanos 50 DF are the recommended anchor products in a downy mildew fungicide program. These products should be used in alternation so that the downy mildew does not develop resistance. To further delay the development of resistance and enhance the ability of the anchor products (Previcur Flex, Tanos 50 DF) to control disease, a protectant fungicide (mancozeb or Bravo, for example) should be added to each spray.

Spray 1: Previcur Flex (1.2 pt.) + Bravo (or Mancozeb)
Spray 2: Tanos 50 DF (8 oz.) + Mancozeb (or Bravo)

If Previcur Flex is not readily available, two Tanos 50 DF applications can be made in a row prior to changing up the spray program with Previcur Flex. Overall, fungicides are more likely to be effective when applied prior to the appearance of downy mildew. Tanos 50 DF 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.

If you grow watermelons, squash, or pumpkins
Frequent applications (every 7 days) of Mancozeb may be adequate but as the pressure builds in the state, I’m inclined to suggest using Tanos 50DF in alternation with Previcur Flex in the program as well (Note: Remember that Mancozeb is not labeled for use on pumpkin, but you can use Maneb/Manex). If this seems wishy-washy, the problem is that we don’t know whether the downy mildew pathotype in the state can infect these crops. Since all of the pathotypes that infect cucumber also infect cantaloupe, the spray recommendations are obvious for cantaloupes. The waters become murky after that. For instance, two out of the five downy mildew pathotypes that infect cucumbers (and cantaloupe) also infect watermelon. Only one of the five downy mildew pathotypes that infect cucumber (and cantaloupe) can also infect squash and pumpkin.

Here are some thoughts as you consider whether you can justify the cost of a more robust downy mildew program for watermelons, squash, and pumpkins:
There is more time this year than last year for the downy mildew to build up in the state.

It is still very early in the growing season. This is different than last year when downy mildew was detected in August. Downy mildew infections early in the season translate into large yield and quality losses.

Adding Tanos and Previcur Flex to the spray program offers protection from downy mildew and other pathogens that can affect these crops each year in Michigan. Not the least of these is Phytophthora capsici! Since Phytophthora is a cousin to downy mildew, the fungicides that are recommended for downy mildew also offer some control of Phytophthora crown and fruit rot.

You cannot play catch up with downy mildew. Fungicides must be applied preventively to work well.

Previcur Flex or Tanos 50 DF were outstanding products in our MSU trial last year (Note: the Curzate fungicide has one of the active ingredients that is present in Tanos 50 DF and can be used in place of Tanos 50DF). If Curzate is used, it should be mixed with either Bravo or Mancozeb. Curzate should not be used in alternation with Tanos 50DF because they have an important active ingredient in common.

• Weather – Is the weather favorable for downy mildew with rain, high humidity, fog, long dew periods?
• Air currents – Will the air current continue to flow to the east?
• Disease spread – Will downy mildew move beyond southeast Michigan into other areas of the state? Will it infect watermelon, squash, or pumpkin?
• Stage of the crop – Is it close to harvest? The closer you are to the finish line, the better.

While downy mildew is not widespread in the state at this point, each day can bring a report of a new outbreak. We must remain vigilant! Walk those fields, send in suspicious samples, let’s work together to get through this season. My lab (517-355-4576) and Diagnostic Services (517-355-4536) on campus are available to look at any potential downy mildew samples. I can be reached via cell phone at 517-927-4532.

Potato late blight was confirmed in a field in southwest Michigan near the town of Three Rivers. It was found on a variety particularly susceptible to the disease. However, it is highly unlikely that the disease was initiated through seed-borne infection as it appeared seven days after heavy rains and thunderstorms passed through the area. The outbreak has been contained, as the infected area has been desiccated with Diquat and the surrounding crop and fields have been sprayed with Gavel, Curzate, Super Tin and Bravo.

The numbers of European corn borer moths caught in pheromone traps remain low throughout most of Lower Michigan. Some locations (Montcalm County, Mason County, Macomb County) are still catching several moths per trap while others (Ingham County, Oceana County, Monroe County) are catching none (or nearly so). The first flight is over, or nearing its end for most Michigan locations. We expect the second flight of moths at about 1450 to 1500 GDD50. In many parts of southern Michigan that is only one or two weeks away, especially with the predicted very warm weather.

Low to moderate numbers of aster leafhoppers are present in most carrot and celery fields in west Michigan. Recent test results for aster yellows infectivity (conducted by MSU Diagnostic Services) reveal low infectivity rates for leafhoppers collected from celery fields in southwest Michigan. Infectivity rates for leafhoppers collected from carrot fields continue to be higher and are variable. I feel comfortable recommending a treatment threshold of 30 to 35 aster leafhoppers per 100 sweeps for celery fields in southwestern Michigan. Because of the variability in infectivity rates in leafhoppers collected from carrot fields in west central Michigan, I would suggest a treatment threshold of 10 to 25 leafhoppers per 100 sweeps and using the lower numbers for fields near abundant wild carrot populations or fields that traditionally have a problem with aster yellows.

Large populations of tarnished plant bugs are reported in southwestern Michigan. Tarnished plant bug feeds on a variety of vegetable crops, including asparagus, snap beans, lettuce celery and others. The adults are approximately one-third of an inch long, are bronze-brown with black markings and are extremely mobile. Adults may fly in and out of fields quickly (Most flight occurs in early morning and late afternoon/evening.), leaving only plant damage as evidence of their presence. Both adults and nymphs (which cannot fly, so are less mobile) feed by sucking juices out of plants. In asparagus, feeding by tarnished plant bug produces “tip die off” above the feeding site. In snap beans, tarnished plant bug feeding may produce flower abortion or feeding injury (brown spots) on pods. In celery and lettuce, feeding produces small brown areas of necrotic tissue which reduce quality and may promote secondary bacterial infections. Tarnished plant bug may also damage potatoes, tomato fruit, peppers and fruit crops.

Plants are most vulnerable to tarnished plant bug infestation when alternate hosts are less attractive. In most plants (weeds and cultivated) tarnished plant bugs prefer plants flowering and producing seed. Once weeds start to senesce and/or dry down, they become less attractive and large numbers of tarnished plant bug adults may move into nearby vegetable crops irrigated and growing vigorously. In addition, tarnished plant bugs move out of alfalfa fields (one of their preferred food) after it is cut or during prolonged dry periods.

Since tarnished plant bugs are so mobile, growers should scout fields by sweeping for adults and nymphs (preferably early in the morning) or inspecting their crops for signs of feeding damage. It may be beneficial for growers to sweep adjacent hedgerows and ditch banks. If large numbers of tarnished plant bugs are found on the weeds in these areas, you can expect that they may be moving into fields to feed. Consult Bulletin E-312: 2006 Insect, Disease and Nematode Control for Commercial Vegetables, for insecticides registered to control tarnished plant bugs on vegetable crops and for treatment thresholds for some crops. This bulletin can be viewed at http://veginfo.msu.edu.

Squash bug eggs have been found on vine crops in many areas of Michigan. Squash bugs feed on the leaves and, later, the fruit of squash and pumpkin plants. They suck plant sap, causing wilting and fruit collapse. Adults are 0.5 to 0.75 of an inch long and grayish-brown. Nymphs are wingless and pale green to white with brown heads. Eggs are laid in clusters on the underside of leaves.

Large nymphs and adults are extremely difficult to control. (see photo) Therefore, growers must control them when eggs are being laid. Small nymphs are less mobile than larger nymphs and tend to stay in small groups. Adults and larger nymphs are very mobile and move quickly throughout the entire field. This habit, in combination with the foliage associated with an older squash or pumpkin field, means that controlling adults or large nymphs is virtually impossible. Growers should be scouting fields now and applying insecticides, if necessary.

Squash vine borer moths have been caught in pheromone traps in southwest Michigan. This is another pest that must be controlled when eggs are being laid and larvae are hatching. See the June 28Vegetable CAT Alert for more details on squash vine borer control.

Hot and dry weather conditions are favorable for rapid increases of thrips populations. Adult thrips are very small (ca. 1/16 inch), yellowish, slender and have fringed wings. The immatures look like small wingless adults. Thrips reproduce very rapidly at high temperatures, and we may have five to eight generations per year.

Thrips have “rasping sucking” mouthparts and feed by scraping the surface of leaves and sucking plant juices, reducing photosynthetic capacity. Thrips prefer tight spaces and tend to spend most of their time hidden between leaves. This behavior makes it difficult for insecticides to come into contact with the insect. Use adequate gallonage and pressure when spraying insecticides to increase chemical contact with the insect. Extension bulletin E-312 lists registered insecticides for thrips control.

The label for the herbicide Accent has been expanded to include sweet corn grown for processing and fresh market.

Accent may be applied postemergence to sweet corn for control of annual grasses and some broadleaves. It will control most annual grasses up to about 4 inches in height. It also gives some control of dandelion, jimsonweed, morningglory, pigweeds and smartweeds. Accent may be applied as a broadcast treatment until corn has 5 leaf-collars or is 12 inches tall. It may be applied to sweet corn 12 to 18 inches tall with drop nozzles.

Always include a surfactant with Accent. Use crop oil concentrate (COC) at 1%, methylated seed oil (MSO) at 0.5%, or nonionic surfactant (NIS) at 0.25%, by volume. (Eg., 0.25% is 1 qt in 100 gallons, or 8 fl oz in 25 gallons of water.) Also, include an ammonium nitrogen fertilizer, either 2 quarts/acre of 28% UAN, or 2 lb/acre of spray-grade ammonium sulfate.

The normal use rate of Accent is 1/3 to 2/3 oz product (0.015-0.031 lb ai) per acre. Up to 1 1/3 oz/acre (0.062 lb ai) may be applied to kill large weeds. Some sweet corn hybrids may be sensitive to Accent, and growers should use lower rates until they have some experience with it. Pesticide applicators should have a gram scale or balance available for measuring these very small amounts of pesticide. One ounce is 28.35 grams.

Accent is a sulfonylurea herbicide. Chemicals in that chemical family tend to have long residual lives in the soil and carryover is a potential problem. Accent may injure sugar beets or potatoes grown after sweet corn on soils with pH above 6.5. Most other vegetable crops appear to have sufficient tolerance to follow Accent application the next year.

See the label for more specific information on use of Accent on sweet corn. Labels should be available from dealers or DuPont representatives.

Field Day – August 1, East Lansing

Natural enemies and bees need pollen and nectar to survive, yet many farms provide these resources only during bloom. MSU is studying native Michigan flowering plants that can provide these resources for farmers throughout the growing season. We are hosting a field day on August 1 to provide an update of this project. Planting these native Michigan perennials adjacent to vegetable crops could help increase the abundance of these insects over the long term, leading to less need for pesticide sprays and greater fruit set and yield. This field day will help growers see the plants and learn more about which ones are most attractive to bees and natural enemies.

• Learn which natural enemies common at native plants can help control your crop or garden pests.
• Hear about seeding a prairie strip with hand broadcast and seed drill methods.
• Visit a native plant nursery to learn about plant selection, seeding establishment, and maintenance.

To register, send $20 (for lunch, educational materials) check made payable to Michigan State University; your name, address, phone, and email to: Heather Lenartson, MSU Dept of Entomology, 243 Natural Sciences Bldg., East Lansing, MI 48824.

For more information, email Anna Fiedler at fiedlera@msu.edu or view details at http://ipm.msu.edu/plants/pdf/field-day06.pdf .

Can’t attend the field day? Learn more about native plants and beneficial insects at http://ipm.msu.edu/plants/home.htm

Regional reports
1 -- Southwest
Ron Goldy

Weather
Temperatures through the period averaged slightly below normal with highs between 73°F to 86°F and lows from 51°F to 68°F. The area received from 0.5 to 1 or more inches of rain. Heavier amounts were in the eastern parts of the region.

Commodity reports
There was a general increase in diseases and insects over the past week. Tarnished plant bug, leafhopper and Japanese beetle numbers have increased. Squash bug adults and eggs can be found. No reports of squash vine borers at this time. Bacterial spot and speck can be found on tomatoes.

Tassel feeding by European corn borers can be found in sweet corn.

Watermelon and cantaloupe continue to bloom and baseball-sized fruit can be found. Bee activity in these fields is strong. Some wind damage occurred again over the weekend in yellow squash and zucchini fields. Pumpkins are vining well.

Tomatoes, peppers and eggplant continue to grow well in response to temperature and light levels. Peppers are blooming, setting fruit and sizing well.

2 -- Grand Rapids Area
Amy Irish-Brown

Weather
Air temperatures have continued to be normal to slightly above normal for the past week. Up until Tuesday, July 11, there had been little rain across the region for several weeks and water-stressed plants were starting to be seen and irrigation was in full swing. Some much needed rainfall occurred on July 11 with variable totals across the areas surrounding Grand Rapids. All areas received at least an inch and some more than 2 inches. This will help with the slight rainfall deficit we were getting into, especially ahead of the predicted very warm temperatures expected for this weekend.

Commodity reports
Summer squash harvest continues. Squash bug eggs are becoming easier to find and should start hatching at any time. Squash vine borers are flying, so controls will be important over the next few weeks.

Staking and tying continues in tomatoes – plants look healthy with no noticeable foliar diseases yet. A few very small hornworm larvae can be found here and there.

Radish planting and harvest continues.

Lettuce crops are in various stages of growth. Harvest is ongoing.

Cabbage transplants are doing well. Cabbage moths can be seen flying around fields.

Celery is developing nicely. The recent rains will be good for celery. Continue to monitor leafhoppers and control them where needed to prevent the spread of aster yellows.

Onions are beginning to bulb. Be on the lookout for thrips.

Early planted sweet corn will be harvested later this week. Corn borer larvae can still be found in some areas and control measures are needed. Corn earworm will also be a concern on any sweet corn that is in tassel. Be sure to protect the silks.

Seeded vine crops are filling rows nicely. Squash vine borers are flying, so management applications should be made soon. Striped cucumber beetles can still be found in many fields and insecticides may continue to be needed to prevent disease spread.

3 -- Oceana County
Norm Myers

Weather
Rain fell across Oceana County last night with amounts generally higher in the southern parts of the county than the northern part. The MAWN station at Hart received about a third of an inch, but that area has been much wetter than the south. We did have some isolated hail damage in some parts of the county over the last two weeks. Heat units (GDDs) have been running about normal.

Commodity reports
Final processing numbers for the 2006 asparagus season was over 22,500,000 pounds. While much less than historic high production levels, that figure was 5,000,000 pounds higher than 2005. Rust and common asparagus beetle are common problems in emerging fern. Our Tom-Cast sensors are now all placed and the present wet and warm conditions should generate a lot of disease severity values, so purple spot may become a problem.

Scouts are reporting low levels of cercospora blight in carrots. Most growers have covered their fields with fungicide and are using Tom-Cast for further sprays. Aster leafhopper numbers are generally low.

Harvest is now under way on the earliest planted zucchini fields. Late plantings are all doing poorly and most people are blaming this on herbicide damage caused by the heavy rains immediately after planting. Most growers have now put on one spray for striped cucumber beetle.

4 -- Mason-Newaygo counties
Jim Breinling

General rainfall was very welcome in the area late yesterday (July 11). Rainfall amounts reported in Mason County were in the one-third to inch range with 0.34 inches reported at the Ludington MAWN station. It was different in Newaygo County, after 0.44 inches for the past three weeks, 1.79 inches was received at the Fremont MAWN station with unofficial reports of more than 2 inches.

European corn borer trap counts at a snap bean site were 0, 1, 13 this week. Field at site is just beginning to bloom. Planting will finish this week, weather permitting. Harvest will begin in approximately two weeks.

Local sweet corn will be available this week. No corn earworm was found in traps at the Mason County site.

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

Weather
Thunderstorms on July 4 brought 0.25 inch or more of moisture to some areas, and the widespread system we are under now has given the area an inch or more in the past three days. High temperatures since July 1 have ranged from 75 to 90°F and humidity has ranged from very low to very high in the past two days. Weed control problems resulting from dry conditions are resulting in hand weeding on many crops. Soybean aphid numbers are low in this area.

Commodity reports
European corn borer numbers in sweet corn are remaining fairly consistent for the first flight with an average of five per trap. While we are monitoring for corn earworm adults in more effective wire mesh traps (see picture), the moths we are catching do not appear to be earworms. I will get a positive ID and report next week. First harvest of bare-ground corn will begin in about one week. Corn coming from the southern states has been of poor quality, in my experience, so local corn will be welcome.

In squash, melons and cucumbers, s triped cucumber beetles are not active at this time in fields I observed, but bacterial wilt, the disease they vector, may be found occasionally on cucumbers and melons. What appears to be anthracnose has made an appearance in a cucumber field. Muskmelons are beginning to net (see picture), and I observed a good set on the crown blossoms but poor fertilization on subsequent sets. Harvest is predicted to begin in three weeks but warm weather may push the development. Harvest of summer squash continues. Early wholesale cucumbers are nearing harvest.

Carrot harvest is predicted to begin in about 10 days. Cooking onions on the muck are bulbing, and thrips numbers are remaining below threshold. Yellow Granex onions for bunching are now available at farmers markets.

Tomatoes are setting fruit and there is evidence of catfacing on the crown set. Some very early tomatoes are yielding the first fruit as are greenhouse tomatoes. Most peppers are now beginning to set fruit.

Broccoli and cauliflower are now available for retail sales.

Bean harvest has begun.

Most cool season crops are now available at farmers markets including new potatoes, herbs, cole crops, bunching onions, peas and beets. (see picture)

6 -- Monroe County
Paul Marks

Weather
Accumulated GDD50 for our area this week is a total of 1256, which is just a little below the long term normal of 1359 putting us about three calendar days behind normal. Potential evapotranspiration averaged just over 0.25 per day this last week with rainfall only during last night providing less than one half inch in my area. Irrigation started again this week in most crops.

Commodity reports
Sweet corn harvest has begun on many farms with larger volume by this next weekend. Corn borer and earworm traps were all empty this week. Corn borer larvae are still difficult to find, and very little feeding damage is evident in corn. We have now accumulated over 800 degree days since this first generation European corn borer moths appeared in our area indicating the second generation should begin in 7 to 10 days.

Tomatoes for fresh market are being harvested with reasonable quality fruits for the first harvest. Larger volume will be available next week. Alternaria early blight (See photo) has appeared in several fields of market tomatoes this week.

Slicing cucumber harvest as well as hand harvest pickles has begun. Downy mildew has been identified in cucumbers on one additional farm in our area this last week.

Muskmelons planted under tunnels are netting with open fields now showing fruits in the six inch size. Fields that were stressed with excess water earlier are heavy with male flowers and short on female flowers.

Pumpkin and hard squash are showing first female flowers with good vine development.

Cabbage and other cole crops being planted for fall harvest have been watered this week as soils have dried quickly in the surface layer.

Potato harvests for early tablestock have begun to be packed this week. With the weekend heat predicted, keeping quality may be questionable.

Weather news
Jeff Andresen
Agricultural Meteorology
Geography

The weather system that brought much-needed rain to parts of Michigan, Tuesday (July 11) will move out of the state by Wednesday afternoon, setting the stage for several very warm and humid days though the upcoming weekend. A few scattered showers will be possible during the day Wednesday, especially in eastern sections of Lower Michigan. Most areas will remain dry. High pressure will move back into the region Thursday and persist through the weekend, leading to hot and dry weather statewide. Temperatures will surge to much above normal levels for the next five days with means running 5 to 10 degrees F above the climatological normals. High temperatures Thursday through next Sunday will generally range from the mid- or upper 80s north to the low and possibly mid-90s south with lows ranging from the mid- and upper 60s north to the low 70s south. With dew point temperatures approaching 70°F, heat index values could approach 100°F this weekend. A cool front is expected to approach the region by late Sunday or Monday of next week with the next chance for significant precipitation, followed by cooler temperatures by Tuesday and Wednesday.

Medium range forecast guidance has been consistent the past few days suggesting upper air troughing over the western United States with a ridge over most of the central United States. As a result, both 6-10 day and 8-14 day outlooks from the NOAA Climate Prediction Center (covering July 17-21 and 19-25) call for above normal temperatures state- and region-wide. Precipitation totals during the 6-10 day time frame are forecast to range from above normal across southwestern sections of Lower Michigan to below normal across central and western sections of the Upper Peninsula. During the 8-14 day period, a slightly different pattern is forecast with rainfall expected to range from below normal levels across the eastern Lower Peninsula to normal levels elsewhere across the state.