The threat of downy mildew continues to drive the spray recommendations. Last Friday, the North Carolina State University Cucurbit Downy Mildew Forecast issued the following prediction for southeast Michigan:

Serious Threat of downy mildew developing for Thursday (June 22), Moderate Threat for Friday (June 23), and Low Threat for the weekend (June 24, 25).

If this week’s weather forecast holds (cloudy and rainy), it is likely the downy mildew threat will increase again.

What about the threat of downy mildew to Michigan growers outside of the southeast region? According to the Cucurbit Downy Mildew Forecasts that have been generated, the southeastern portion of Michigan has the highest risk. However, that does not mean that the other regions of the state have a zero chance of disease.

Downy mildew also threatens other growing regions outside of Michigan. Last week, the downy mildew risk was high for northern Ohio and southern Ontario and moderate for southwest and south-central New York and northern Pennsylvania.

These forecasts are based on the downy mildew biology, weather predictions and the trajectory of the air currents carrying the spore loads. The mat of velvet that forms underneath the leaves are actually masses of spores that are commonly referred to as sporangia. These spores are formed during the night when the leaves become wet with dew, rain or fog. The spores are produced on spore stalks. The spores mature (or ripen) during the early morning hours of (1:00 to 5:00 AM). As the morning progresses, the leaves begin to dry, the relative humidity falls and a breeze may begin to blow. As the morning dew dries, the spore stalk begins to dry and twist, dislodging the mature (ripened) spore from its stalk and placing it into air currents (See graph). The air currents can then move these spores long distances. Rain showers are thought to scrub these spores from the atmosphere and deposit them onto fields. Once the spores are dropped from the air onto the foliage, wetness is needed for the spore to germinate and cause a new infection.

Fungicides are most effective when they are applied prior to the spores landing on the leaf’s surface. Once the spores have germinated and penetrated the leaf, it becomes much more difficult to limit downy mildew. A preventive approach will always be more effective than trying to stop the disease once it has appeared.

Spore traps have been placed in six Michigan counties and include: St. Joseph, Allegan, Monroe, Bay, Van Buren and Saginaw counties. The spore load has been relatively high from Monroe County during certain days when the weather was favorable for spore production. The downy mildew spores detected in the other spore trapping regions in the state have been negligible. Please remember that the spore traps may not be in the correct site to pick up all influxes of downy mildew spores into a region. At this point, we are using these traps as a research tool. Any information that we learn from these traps will be shared over the course of the growing season.

Growers of pumpkins, squash, or watermelons in the southeast Michigan region should be on a 7-10 day alternation program.

Alternate these sprays:

• Previcur Flex (1.2 pint) + Bravo (or Mancozeb)
• Tanos 50DF (8 oz.) + Mancozeb (or Bravo)

Please note: Mancozeb is not registered for use on pumpkins, but Maneb or Manex could be used.

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 pre-harvest interval (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.

At this point, downy mildew appears to be isolated to Monroe County. No new fields have been reported to have the disease. It is possible that the two fields that are currently diseased will be out of production sometime next week and will be burned down. Growers of cucumber and/or cantaloupes in the rest of the state have a lower risk of downy mildew developing than the growers in southeast Michigan who are in the immediate vicinity of the infected fields. How low is the risk to the Michigan areas outside of Monroe County and what should be done to protect cucumbers and melons in the northern and western parts of the state?

The fungicide program that offers the least risk of downy mildew developing also carries the highest cost: a 7-10 day alternation program with the fungicides Previcur Flex (1.2 pint) + Bravo (or Mancozeb) alternated with Tanos 50DF (8 oz.) + Mancozeb (or Bravo).

A fungicide program that offers a moderate level of risk with a more moderate price tag includes a mancozeb only program applied every 7 to 10 days. Mancozeb is available under the trade names of Dithane, Penncozeb, Manzate and others. Please note: Mancozeb is not registered for use on pumpkins, but Maneb or Manex could be used. The thought behind using this program is that if a downy mildew outbreak develops in the growing region, Previcur Flex and/or Tanos would be added to the mancozeb immediately.

While some growers have not applied any fungicides, the relatively high use of fungicides early on likely prevented the spread of this disease to nearby young cucumber and melon fields. Although the disease was initially detected on June 9, the downy mildew was well established and was likely present in the two fields as early as mid-May. We will continue to handle any suspect samples of downy mildew and will visit any fields with unusual symptoms.

European corn borer moths are still being caught in pheromone traps throughout Michigan; although numbers are lower than in previous weeks (see accompanying charts). The current degree-day accumulations (base 50) indicate that the first corn borer flight is nearing its end, although significant numbers of moths are still laying eggs, especially in central and northern Michigan. Growers should continue to protect vulnerable crops. In addition, sweet corn growers should check for larvae and feeding damage when tassels emerge. The second flight of European corn borers begins approximately 1450 to 1500 degree days, base 50.

The first corn earworm moths of the season were caught in pheromone traps during June 20-27, although numbers were low. Six corn earworm moths were caught on campus (Ingham County), and 1 corn earworm moth was caught in Monroe County. These low numbers indicate that the risk is relatively low, but sweet corn growers should ensure that silks (where earworm moths lay their eggs) are thoroughly covered when corn borer insecticide applications are made. Newly hatched corn earworms do not feed initially, but rather move directly from the silk to the ear. Insecticides must be present on the silk to prevent the earworm from entering the ear where it is protected.

Scouts are reporting low numbers of aster leafhoppers (3-7 per 100 sweeps) in celery and carrot fields in western Michigan. (See table for more areas.)

Currently, few fields will have aster leafhopper populations that are high enough to justify insecticide treatment. However, this situation could change quickly if weather patterns change and bring more aster leafhoppers into the state. In addition, eggs laid by adults early in the season have hatched and nymphs are feeding and developing. Once these nymphs become adults with wings, they have the ability to from field to field. Both these factors may result in higher aster leafhopper populations.

No squash vine borers have been reported yet from Michigan squash fields. But adult moths typically begin flying and laying eggs the end of June to the beginning of July. Squash vine borer adults are reddish brown, day-flying moths with clear hindwings and “hairy” legs (see photo). They have a wingspan of approximately 1.5 inches and are often mistaken for a wasp in flight. Female squash vine borers lay eggs singly at the base of plants. Once the eggs hatch, larvae bore into the plant and feed in stems for 2 to 3 weeks before pupating (see photo). There is only one generation per year in Michigan.

Vines wilt and die from larval feeding. Often the damage is not noticed until it is too late; once larvae have managed to enter the stem they are protected from insecticides. Growers should check vines at the base of squash and pumpkin plants for entry holes and waste material produced by the larvae. An insecticide application should be made at the first signs of larval feeding, directed at the base of the plants. A second application, 5 to 7 days later, will protect the plants for the rest of the season. For insecticides registered to control squash vine borer or other pests, consult Bulletin E-312, 2006 Insect, Disease and Nematode Control for Commercial Vegetables available at http://veginfo.msu.edu.

Cucumber growers anticipate another year of downy mildew infestation in their crops. There have been questions about mixing postemergence herbicides and fungicides for control of broadleaf weeds and diseases in a single pass across the field.

The primary postemergence broadleaf herbicide for cucumbers is Sandea (halosulfuron). It is formulated as a 75DF. Mixing Sandea with fungicides with flowable or dry flowable formulations should not increase crop injury. Emulsifiable concentrate (EC) formulations usually increase the potential for crop injury in tank mixes, so avoid mixing Sandea with any pesticides formulated as EC.

Before mixing any pesticides, check labels for any cautions or restrictions on tank mixes.

• http://ipm.msu.edu/vegetable.htm
  IPM Resources page for vegetables. Includes direct links to seasonal IPM advice, the Enviro-weather web site, MSU Diagnostic Services, the Soil/Plant nutrient lab, cover crops advice and the regional web site, VegEdge.
• http://veginfo.msu.edu/
  VegInfo search helps locate bulletins, Expo presentations, crop protection labels and other resources for vegetable growers and consultants.
• http://ipm.msu.edu/veg-cat.htm
  Vegetable CAT Alert home page. Search previous 5 years of CAT Alerts using a keyword search. Sign up to get an email announcement when new issues are posted at the web site.
• http://www.enviroweather.msu.edu
  Enviro-weather is a new and expanding site offering Michigan weather data for making IPM and other production management decisions. MSU has plans to expand the pest models at this site and add additional weather stations. Visit the home page, click on the station nearest you, to quickly access degree day totals, precipitation totals and wetting events. The site links to the potato late blight monitoring site and offers links to the IPM Resources web for your reference when making pest management decisions.
• http://www.msue.msu.edu
  MSU Extension’s portal with links to local county as well as statewide resources
• http://www.maes.msu.edu
  New web site of the Michigan Agricultural Experiment Station.

Regional reports
1 -- Southwest
Ron Goldy

Tomato tying continues. No problems have been seen in tomatoes.

Peppers are in early bloom and look very nice for this time of year.

Yellow squash, zucchini and cucumber harvest volume is increasing as more fields come into production. Watermelon and cantaloupe transplants are in bloom and growers should be moving bees into those fields. Striped cucumber beetles are active and control measures may be needed in some fields. No squash vine borers have been observed at this time, but they should be in the area soon.

Early sweet corn is in tassel.

2 -- Grand Rapids Area
Amy Irish-Brown

Staking and tying is being done in tomatoes.

Radish planting and harvest continues.

Lettuce crops are in various stages of growth.

Cabbage transplants are doing well.

Celery is developing nicely – water could become a concern soon.

Early planted sweet corn is beginning to tassel.

Seeded vine crops mostly have 6 to 8 leaves present; they should start to run soon and vine borers could be an issue.

In general, cultivation for weeds is being done where possible because of lack of herbicide effectiveness. Potato leafhoppers are present in many fields in various stages.

4 -- Mason-Newaygo counties
Jim Breinling

Weather
Temperatures have been normal during the past seven days. Rainfall reported at the three MAWN stations located at Fremont, Hart and Ludington reported .63, .72 and.85 inches respectively during the 7-day period. On Monday afternoon (June 26) a thunderstorm covered a large portion of eastern Oceana County with rainfall amounts ranging from 1 to 3 inches in a short period of time. Hail was also reported in some of the area.

Commodity reports
 Asparagus harvest is officially over. Processor receiving ended on Tuesday, June 27.

Carrot fields are growing well at this time. Aster leafhopper numbers remain low with 7 to 9 per 100 sweeps found in Oceana County during week of June 26.

The onion crop is progressing well. Some bulb development now.

Vine crop plantings are getting established and starting to grow well. There has been standing water in places in numerous fields in Mason and Oceana counties. The storm on June 26 was a typical phytophthora rainfall event.

Snap bean planting continues. European corn borer trap counts in Mason county on June 27 were 5 and 1 and 51, substantially lower than the previous week.

No corn earworm were found in the trap at the sweet corn site in Mason county.

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

Muskmelons now have fruit several inches in diameter and are filling the rows quickly.

Tomatoes are beginning to set fruit. Some growers are beginning protective fungicide sprays.

Cabbage harvest is underway and some splitting may be found on the earliest and most susceptible varieties.

Leaf lettuce is responding well to the cool conditions with an excellent crop.

6 -- Monroe County
Paul Marks

Weather
Several rain events this last week beginning on Wednesday, June 21, have brought adequate to surplus moisture to our area. Hail was also part of several of these events and damaged many vegetable crops, most significantly tomatoes and peppers. Warm conditions with adequate moisture have created ideal growing conditions for most crops.

Commodity reports
Cabbage harvest continues with most growers reporting a soft market for an excellent quality crop. Late season cole crops are being planted in very good soil conditions.

Tomatoes for market are a week or more away from harvest in earliest fields and appear to contain very good quality early fruits, where not damaged by hail. Processing tomatoes in earliest fields have twin rows completely filled with many blossoms now present. No pest problems found in this crop so far this season with the exception of large numbers of tarnished plant bugs.

Cucumbers for hand-harvest pickles are now tipping over, have been blocked and show first flowers. Slicers under tunnels are being harvested, and in open plantings, are at first female flowers. Downy mildew in our area is still limited to one location and I have not seen it in any other fields. Cucumber beetles are still active,

Pumpkins and squash seeded in early to mid June are developing well and beginning to vine in some fields while others have not yet tipped. No flowers yet.

Sweet corn harvest in most fields is still two weeks away with pollination just now taking place. Corn borer adult activity is now between generations with larvae now present, although in much lower numbers than expected based on the high level of moth activity earlier. One corn earworm adult was in my trap this week.

Potatoes look very good with very few pests. I have not seen any diseases nor any potato beetles. Several fields I have checked this week have leafhoppers above threshold for the second time this season. Early fields have two-inch tubers, while late fields are just fully emerged.

Peppers have begun to grow past the stem damage from late May. Many fields are slower to develop this year than most growers would like.

Weather news
Jeff Andresen
Agricultural Meteorology
Geography

The upper air pattern Wednesday morning (June 28) across North America includes a ridge across western sections of the U.S., a trough over the Great Lakes region and another ridge just off the eastern shore in the western Atlantic. Most of the current forecast guidance suggests that this general pattern will persist for the majority of the next 1 to 2 weeks. Near the surface, a persistent plume of semitropical-origin moisture streaming northward across the eastern U.S. has been in place since the weekend, leading to torrential rains and widespread flooding across portions of the mid-Atlantic region. Further to the west, a weak and diffuse area of low pressure was located over Michigan =s Lower Peninsula. Given the moderated amounts of low-level moisture available, this weather scenario will set the stage for a continuing chance for showers and thunderstorms during the next couple of days, especially over eastern sections of the state and during late afternoon and early evening hours when atmospheric instability tends to be greatest. Thursday and Friday, there will be a chance for isolated afternoon and early evening rainfall, with most areas remaining dry.

A cool front will approach and move through the state Saturday into early Sunday, bringing a chance for more widespread rainfall. That front is expected to stall and linger in the region, possibly leading to more precipitation chances early next week. Overall rainfall totals during the next 5 days are expected to reach the quarter to half inch range over most of the state where rain falls, with some isolated 1 to 2 inch totals possible. Some areas will remain dry, especially in western sections of the state.

Temperatures through Sunday will remain close to the climatological normals, with highs generally ranging from the upper 60's or low 70's far north to the low 80's south. Low temperatures will generally range from the upper 40's north to the low 60's south.

Medium range forecast guidance basically suggests a continuation of the pattern described above. The NWS Climate Prediction Center 6-10 day outlook (covering July 3-7) calls for temperatures to range from below normal levels in extreme southeastern sections of the state to near normal levels elsewhere. Precipitation totals are forecast to range from near normal levels across eastern sections of the state to above normal levels across the west. During the 8-14 day period (covering July 5-11), the outlook calls for mean temperatures to moderate to near normal levels, with precipitation forecast to fall back to below normal levels statewide.