Downy mildew was confirmed on June 9 on slicing cucumbers in Monroe County. Currently, there are two 8- to 10-acre fields with advanced disease. These two fields were planted in late April by direct seeding and plugs grown in an on-site greenhouse. At this time, there is no visible disease on nearby cantaloupe plantings. Other cucumbers in the Southeast area are only recently emerged and are not diseased. At present, cucumbers and cantaloupe are most at risk. It is less likely that pumpkins and squash will become infected by downy mildew. At this time, it is not known whether this is an isolated incident or more widespread problem. Many cucumber fields in other regions of the state have been scouted and no disease has been found.

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. This fuzz may be most evident in the morning. Leaves of all ages can become infected, including cotyledons.

Spray 1: Previcur Flex (1.2 pt.) + Bravo (or Mancozeb)

Spray 2: Tanos 50 DF (8 oz.) + Mancozeb (or Bravo)

Growers of cucumbers and/or cantaloupes outside of the southeast Michigan region should also use the above program but can use a 7-day spray interval.

Many growers have reported that Previcur Flex may not be readily available. In that case, lead off with Tanos 50 DF. 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 five days. Bravo has a zero-day PHI.

If you grow watermelons
An application of mancozeb is adequate at this time while the disease situation in the state is assessed.

If you grow squash and pumpkins
Fungicide sprays are not critical at this time. Stay tuned for a change in this recommendation.

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.

See http://www.ipm.msu.edu/cat06veg/pdf/downymildew.pdf for results of last year's downy mildew fungicide trial.

European corn borer moths continue to be caught in pheromone traps throughout Michigan. During the week of June 6-13, pheromone traps in Ingham County (MSU campus) captured an average of 8 moths per trap. An average of 50 per trap were caught in Monroe County, 2 per trap in Oceana County, 7 per trap in Montcalm County, 10 per trap in Mason County, and 9 per trap in Macomb County.

In most areas of southern and mid-Michigan, degree-day accumulations indicate that the moths are at peak flight and egg laying. Crops and stages at risk for corn borer infestation include sweet corn at tassel and beyond, and snap beans and peppers with fruit. European corn borers may lay eggs on potatoes if corn is small and unattractive. See the previous May 31 and June 7 issues of the Vegetable CAT Alert for more details.

During the past two weeks, aster leafhoppers were collected from celery fields in various locations in Michigan and were tested for aster yellows infection by Diagnostic Services. Leafhoppers from all sites (Newago County, central and southeastern Ottawa County, and eastern Allegan County) tested negative for aster yellows. An appropriate treatment threshold for celery in these areas is 35 aster leafhoppers per 100 sweeps.

Regional reports
1 -- Southwest
Ron Goldy

Weather
Temperatures through the period were generally cooler than normal with highs ranging from 65°F to 76°F and lows from 45°F to 57°F. The area received only a trace of rain on June 11. Soil moisture levels are quite low in many areas since recent rain events have been spotty.

Commodity reports
Harvest is complete on many asparagus fields, and post-harvest weed control and fertilizer is being applied. All fields will be done by next week.

Tomato staking and tying continues, and final transplants are being set.

Stakes are being set in pepper plantings. Side shoots are developing nicely.

Potatoes are in full bloom.

Early planted sweet corn is in the early tassel stage and has greened-up nicely in response to warmer temperatures.

Tunnel-grown, transplanted zucchini and yellow squash are being harvested. Tunnel-grown cucumber harvest should begin next week. Watermelon and cantaloupe transplants are beginning to runner.

3 -- Oceana County
Norm Myers

Weather
We’ve had a very cool week with low temperatures over the last week in the upper 30s. Most soils are getting dry and irrigation has started up in some places. Most growers are not too worried about the dry weather since it allows annual crops to root deeply.

Commodity reports
Most are still harvesting asparagus, but the predicted heat this weekend will probably finish off the older, weaker fields where quality is already a struggle. Scarce labor supplies will be switched to younger, more productive fields, especially by fresh market producers. Fresh market isn’t as hot as it was last week, because Peru and southern Mexico have moved into the market, but it is still probably the most profitable market at the moment. Common asparagus beetle has continued as a severe pest threat right through the cool snap. Most growers report that carbaryl applications control this pest only as long as the treated spears remain in the field. Once the treated spears are harvested, growers must re-treat.

Carrot stands remain about average in most processing fields. Aster leafhopper numbers are generally low. Weeds are a struggle this year, perhaps because of the cool weather.

Winter squash and pumpkins are mostly emerged and forming true leaves. We do have a few replants that will need to go in, probably because of the cool weather. We did worry about herbicide damage, but none has showed up so far.

Most of the first planting of the processing and fresh fields of zucchini have been planted. Some very early processing zucchini is emerged.

4 -- Mason-Newaygo counties
Jim Breinling

Temperatures remained below average during the past week with nighttime lows mostly in the low 40s. The official low reported on June 11 at Fremont was 39.1 degrees. Field conditions are excellent, but most crops could use the warmer temperatures being forecast for this weekend.

Spinach harvest continues on schedule.

Winter squash plantings are now forming their first true leaves. Cucumber beetle problems persist where soil insecticides were not used at planting.

Tomato and pepper plantings exhibit the effects of the cool weather conditions with plant color that is generally light green.

Emergence of snap beans has been good. Counts in European corn borer traps on June 13 were 9, 0 and 21, which were consistent with the previous week’s catch.

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

In sweet corn, the average numbers of European corn borers in my traps were similar to last week with an average of about four moths per trap.One field of corn is showing very noticeable purpling due to phosphorus deficiency.

6 -- Monroe County
Paul Marks

Weather
No rain again this week for nearly all of our area. Irrigation systems are running in all crops that are either recently transplanted or are near full growth and under heavy moisture need for development. Potential evapotranspiration this week has averaged 0.215 inches per day. We are now at 722 GDD50, which is almost exactly at the 30-year normal for this date.

Commodity reports
Cabbage harvest began last week and is ramping up quickly on a number of farms with good quality. Pest pressure is lower than normal. Fields being transplanted for late summer harvest are being watered to get plants established.

Zucchini and summer squash harvest has begun on farms planted early under tunnels.

Cucumbers for pickles are at the second and third true leaf stage. Slicers are nearing harvest in earliest fields and still emerging in others. Downy mildew has been confirmed in cucumbers in Monroe County late last week.

Muskmelons continue to enlarge with vines running off the plastic in earlier fields and fruits up to 3-inch now present. Fields without tunnels are just covering the plastic. No downy mildew seen in this crop so far.

Potatoes still have a wide range in crop development from tuber bulking in early fields to still emerging in late fields. Earliest fields are in full bloom with tubers up to two inches now easily found. Leafhopper numbers are staying down after one insecticide application several weeks ago. No other pests have been seen.

Sweet corn development ranges from fully tasseled and silked, in several fields that were tunneled, to tassels in the whorls in earliest open planted fields. Late fields are still being planted. European corn borer adult numbers in traps this week averaged 50 per trap, down from last week’s 78. Eggs are still very difficult to find in spite of three weeks now with heavy adult activity.

Tomatoes are growing rapidly in most fields with twin rows filled in early processing fields and second string being placed in early market tomatoes with fruit now showing. No problems seen in this crop.

Pepper planting is finally completed with growth showing in most fields. It does not appear that peppers will be early to market this year.

The northwesterly flow aloft that has led to cooler than normal temperatures across the Great Lakes region during the past week will gradually give way to a large ridging feature currently across the Great Plains. This pattern change will result in a significant warming trend across Michigan during the next one to two days.

In the short term, a weak upper air disturbance will move from northwest to southeast across the region Wednesday (June 14), setting off a few isolated showers and a couple rumbles of thunder. High pressure will lead to mostly fair and dry conditions Thursday. A warm front will pass northeastward through the area Friday, bringing much warmer and more humid air back into the region on southwesterly winds. Some showers and thunderstorms will be possible mainly in northern sections of the state with this frontal passage, while fair, dry and warmer conditions are expected across the south. A weak frontal boundary will approach the state late Saturday into Sunday and likely linger in the region. This will result in the chance for showers and thunderstorms on an almost daily basis through the first half of next week. Rainfall totals by next Monday are expected to range from 0.25 to 0.5 inches over most of the state.

Temperatures will remain at below normal levels one more day on Wednesday with high temperatures ranging from the upper 60s far north to the low and mid-70s south. Much warmer temperatures are likely by the weekend with highs increasing to the upper 70s far north to the 80s central and south by Saturday. Some 90°F highs are possible this weekend. Low-level moisture and dew point temperatures will also be on the increase with lows warming to the upper 50s to upper 60s by this weekend. Given the outlook for much warmer temperatures and the drier than normal conditions experienced since late May in many areas of the state, water stress symptoms may appear in some areas.

Jet stream flow across North America is gradually expected to take on a western troughing, broad eastern ridging pattern during the medium range forecast time frame. This would place Michigan in the vicinity of a strong southwesterly jet stream with warm, humid, subtropical air to our south. Given general southerly or southwesterly winds, above normal temperatures are a good bet.

The 6-10 day and 8-14 day outlooks (covering June 19-23 and 21-27) call for above normal temperatures over large portions of the central and eastern United States including all of Michigan. Precipitation forecasts for both time frames are also similar, calling for rainfall to range from near normal levels across central and southern sections of the Lower Peninsula to above normal levels elsewhere across the state.