 Christmas trees
Field crops
Fruit
Home and yard
Nursery and landscape
Turfgrass
Vegetable
Diagnostic Services
Soil/Plant Nutrient Lab
Enviro-weather
Regional IPM Center
Pesticide safety
Organic: New Ag Network
Invasive species
Sustainable ag & food systems
MSU ANR departments
MSU Extension
Site index
Contacts/permissions |
|
 |
Vol. 21, No. 17, August, 2006
|
|
 Downy mildew update
Downy mildew resources on-line
Corn earworm numbers continue to be high
Aster leafhoppers and aster yellows infection numbers
Regional reports
Weather news |
|
|
|
Mary Hausbeck
Plant Pathology
With the return to more moderate temperatures, the downy mildew has picked up across the state.
Homeowners are reporting death of cucumbers and cantaloupes in their gardens. (view map) Commercial growers report that a 5-day spray schedule is needed on cucumbers to keep the disease under control. Cantaloupes appear to be doing well with a 5-day fungicide program depending on location within the state. The program listed below is working for those growers who are keeping with the short spray schedule. See spore trap chart.
Spray every five days with the following:
Spray 1: Previcur Flex (1.2 pt.) + Bravo (or Mancozeb)
Spray 2: Tanos 50 DF (8 oz.) + Mancozeb (or Bravo)
If Previcur Flex or Tanos 50 DF is not available, the 2006 MSU fungicide trial shows that the new product Ranman (2.75 fl oz) is holding up well and can be substituted. If Ranman is used, mix a full rate of Mancozeb with it.
Most growers of watermelon, pumpkin, winter and summer squash are using a preventive fungicide program for downy mildew. Downy mildew on winter squash has been reported in Michigan. Downy mildew on pumpkin has been confirmed in Ohio. The downy mildew appears to be a lot less aggressive on watermelon, pumpkin, winter and summer squash compared with the cucumbers. The program listed below will provide the needed protection.
Spray every 7 days with the following:
Spray 1: Tanos 50 DF (8 oz) + Mancozeb (Use Maneb or Manex on pumpkins)
Spray 2: Mancozeb (Use Maneb or Manex on pumpkins)
Spray 3: Previcur Flex (1.2 pt.) + Mancozeb (Use Maneb or Manex on pumpkins)
Spray 4: Mancozeb (Use Maneb or Manex on pumpkins)
Growers of pumpkins, cantaloupe and winter squash will need additional products added to their downy mildew program for protection against powdery mildew. Consider adding the following products (at full rates) to a downy mildew fungicide program when protection against powdery mildew is also needed: Pristine, Nova or Topsin. |
| back to top |
|
| |
|
For a complete list of articles and information on downy mildew published in the Vegetable CAT Alert newsletters, visit: http://www.ipm.msu.edu/downymildew.htm
Additional information on the disease in Michigan can be found at Dr. Mary Hausbeck’s website at: http://www.plantpathology.msu.edu/labs/hausbeck/hausbeck.htm |
| back to top |
| |
Beth Bishop
Entomology
We continue to catch high numbers of corn earworms in pheromone traps (see accompanying table). Growers should protect vulnerable crops (corn with fresh silk; snap beans and tomatoes with flowers and fruit) now. For more details, see the August 9 issue of the Vegetable CAT Alert.
Location |
Number CEW |
Location |
Number CEW |
Monroe County |
2 |
|
|
Macomb County |
10 (1 day’s trap catch) |
Mason County |
10 |
Oceana County |
79 |
Ingham County |
68 |
Moderate numbers of European corn borer moths are now being captured in pheromone traps throughout Michigan (see charts). Sweet corn in tassel and beyond, peppers and snap beans with fruit should be protected. For insecticides registered to control corn earworm and European corn borer, see Bulletin E-312, 2006 Insect, Disease and Nematode Control for Commercial Vegetables. This bulletin can be viewed at http://veginfo.msu.edu. |
| back to top |
| |
Beth Bishop
Entomology
The latest results from Diagnostic Services are shown in the accompanying table. We are finding a lot of variability between locations, which is typical for this late in the season. Leafhoppers collected from carrot fields in Newaygo, Oceana and Mason counties continue to be more infected with aster yellows than leafhoppers from celery fields in southwest Michigan. Also, the infectivity of aster leafhoppers captured in carrot fields varies from one field to the next. In general, I recommend a treatment threshold of 10-20 leafhoppers per 100 sweeps in these regions, unless more specific information is available.
Date |
Site |
Crop |
% Infectivity |
Treatment Threshold
(ALH per 100 sweeps) |
7-24 |
Newaygo |
Carrots |
0% |
50 |
8-1 |
Mason |
Carrots |
3.9% |
10-15 |
7-31 |
Newaygo |
Carrots |
19% |
3-10 |
|
| back to top |
| |
Ron Goldy
Temperatures for the period were generally near normal with highs ranging from 77°F to 82°F and lows from 54°F to 68°F. There was only a trace of rain during the past week. There has been no significant rainfall since August 3.
Harvest of most crops is progressing as expected. Cooler weather has slowed maturity and given harvesting and packing crews a break.
Diseases are becoming more prevalent in vine crops. Virus symptoms, powdery mildew and downy mildew are the most prominent.
Fruit set on pumpkins appears low and late, probably due to the warm temperatures in July and early August.
|
| back to top |
| |
Amy Irish-Brown
Temperatures have been more at normal levels for the past week. Rainfall has been light or non-existent and fields are becoming dry with irrigation being done.
Summer squash harvest continues. Mildew is becoming more common.
Tomato foliage continues to be healthy in most fields with little foliar diseases. Harvest is now in full swing.
Celery harvest is ongoing. The internal brown streaking/spotting that was seen last year in Duchess is beginning to show up again. With the similar extreme hot temperatures from 2005 and again now in 2006, it’s beginning to look like it is indeed the heat that is responsible, and it’s a physiological problem, not a pathological one.
Onion harvest has begun.
Sweet corn harvest continues with good quality. There continues to be very little corn borer and no earworm damage in well managed fields.
Vine crops continue to grow. Pumpkin plants are growing quickly. Pickle harvest continues around the Grand Rapids area. Downy mildew is moving into the west Michigan area with additional infected fields being tested and found each week.
|
| back to top |
| |
Norm Myers
Weather has continued to be dry this last week with only brief showers. Irrigation is now general in most areas. Some unirrigated crops are showing drought stress.
In asparagus, dry weather and especially cool nights have helped slow foliar diseases. The dry weather may also keep asparagus from flushing any new parasitic growth. Growers will begin spreading rye cover crops as they do their last insect/fungicide cover, but we will need rain to germinate that seed.
Both foliar diseases are active in carrots, but again cool nights are slowing disease growth. Few aster leafhoppers are being caught.
There are still no reports of downy mildew in cucumbers. Yields so far have been good.
More viruses are showing up on yellow processing zucchini, and there will probably be too much to keep picking in the next week or two. Some powdery mildew is also present, but many of the new green varieties have some degree of powdery mildew resistance. Green yields are above normal this year.
Pumpkins and winter squash are ripening rapidly, and since most of these fields are not irrigated, the dry weather is contributing to the rapid ripening. Most pumpkin varieties are now powdery mildew resistant, but there is some powdery mildew on the winter squash as well as some bacterial wilt on processing Hubbards. Fresh market for both squash and pumpkins appears to be strong, so harvest may be early.
In sweet corn and snap beans, corn earworm catch continues to be high, and European corn borer catch is relatively low.
|
| back to top |
| |
Jim Breinling
A seasonal weather pattern with cool nighttime temperatures has been predominating the past week. No appreciable precipitation has been reported in the area at the Ludington and Fremont MAWN stations.
The snap bean harvest is now seeing the effects of the previous extremely hot weather. Yields are reported below average at this time. There are fields that are not doing well at this time due to previous heavy rains that resulted in extreme soil compaction, poor root development and root rot problems.
European corn borer counts at the Mason County trap site were 5, 0 and 13 on August 15.
The corn earworm trap count was eight this week (August 15) at the Mason County sweet corn site.
There are still no reports of downy mildew on vine crops in the area. Strong east winds did occur on Friday (August 11) that could possibly bring spores into the area.
|
| back to top |
| |
Hannah Stevens
Much cooler, even fall-like conditions continued this week with no rainfall recorded in central Macomb.
In sweet corn, European corn borer trap catches are down this week, probably due to the fact that the field was disked a few days ago. The traps were relocated and caught 13 corn earworms overnight. In view of this I expect a large number are flying. Corn quality is excellent, and there is ample supply overall while some growers are short. I have seen young fields that will be yielding well into September or later.
As I mentioned last week there is very little virus pressure on squash, melons and cucumbers this season; a dramatic difference from last season. However, there is pressure from various other diseases including angular leaf spot, powdery mildew and downy mildew. Early planted Prizewinner pumpkins and some jack-o-lanterns are ripening while those planted later are way behind with growers wondering if they will reach maturity by season’s end. In some field, there are abundant male flowers but few female flowers. Plentiful wild bee and honeybee activity the past few weeks has been observed.
Onions are being shipped, while carrot harvest continues.
The fall cole crop harvest looks to be a good one with good growing conditions for cool season crops.
|
| back to top |
| |
Paul Marks
We are now at 2100 GDD50, which puts us still about five calendar days behind a long-term normal. We had no rain in our area during the last week putting irrigation systems back in action. Cool nights have reduced the stress on crops until midday in fields where irrigation is not available.
Cucumbers that have been protected from downy mildew on the recommended five-day schedule are doing well. Any cucumbers not on this schedule are short-term plants, and many don’t make it to first harvest.
Market tomatoes are finally ripening on a more normal schedule and are being packed for market in large volume. Qualities of the packs are very good. Bacterial diseases have increased the number of culls.
Processing tomato harvest has now begun as of this last weekend, but a little too early to estimate yields.
Sweet corn continues to be harvested at full throttle. Cooler nights have helped slow the maturity to a point that some growers have more than caught up with maturing corn. Corn borer and corn earworms are still present, but at lower numbers. Rust has appeared in several fields of sweet corn, none of which had been protected with fungicides.
Muskmelons are in the midst of heavy harvest with some damage from downy mildew, but at a much lower pressure than in cucumbers. Size and flavor is very good.
Pumpkins are now showing significant powdery mildew in many fields. Perhaps growers have put so much effort into protecting from downy (which I have not seen in this crop) that they have slacked off on the powdery mildew materials until it has shown up and are now trying to “catch up.” Set in this crop appears to be about normal.
Peppers are being harvested with yields, including size and wall thickness, that are excellent! Color appears to be showing up in bananas very quickly and is keeping labor busy trying to keep up. This from a crop that was very slow getting started back in May and June.
Potatoes are being harvested more rapidly now that some of the early fields are more mature. Quality of the tablestock packs is now much better. Growers are reporting some very good yields. |
| back to top |
| |
Jeff Andresen
Agricultural Meteorology
Geography
Relatively little has changed with respect to upper air flow across central North America since last week. There was fast zonal flow aloft resulting in the passage of a series of high pressure air masses across the region and an extended period of fair and mostly sunny weather across Michigan since. Similar conditions will continue Thursday (August 17) with dry weather expected statewide. A cool front will approach and move from northwest to southeast across the state beginning late Friday into Saturday, bringing an increase in clouds and the chance for rainfall. Given that low-level moisture is expected to be in short supply ahead of the front, precipitation with the frontal passage is expected to remain scattered at best with many areas remaining dry and in general, only 0.1- to0.25-inch totals where rain occurs. Best chances for rainfall will be over northern sections of the state during the day Friday, shifting southward into the southern Lower Peninsula during the day Saturday.
High pressure will move back into the region Sunday with a return of fair and dry weather, which is expected to continue into early next week. Temperatures during the next few days will generally average out from close to normal to a degree or two above the long term normals with highs ranging from the upper 70s in northern lakeshore areas to the low to mid-80s south with lows falling to the low 50s north to the low 60s south. Warmest temperatures during the upcoming week will occur this Friday ahead of the cool front (when some mid-80s are possible), falling back again several degrees by Sunday after the front passes. Another cool front is expected to move across the region by late Tuesday or Wednesday of next week with the next chance for precipitation.
The forecast of upper air flow during the medium range time frame suggests mostly zonal to weak northwesterly over the Great Lakes region during the 6-10 day period with the gradual formation of a troughing feature over the northeastern United States and northwesterly flow over Michigan during the 8-14 day period.
The official NOAA Climate Prediction Center 6-10 day outlook (covering August 21-25) calls for above normal temperatures and below normal precipitation statewide. The 8-14 day time outlook (covering August 23-29) calls for some changes with mean temperatures forecast to fall back to below normal levels (in association with the upper air troughing feature) and near normal precipitation totals expected. Forecaster confidence in these outlooks ranges from above normal during the 6-10 day time frame (good forecast model agreement) to near normal during the 8-14 day period.
|
|
Back to top
|
