July 9, 2008
In this issue
§ Vegetable insect update
§ Downy mildew confirmed on the west side of the state
§
Downy mildew confirmed in cucumbers located in
§ Warm, wet weather favors early appearance of several vegetable diseases
§ Glyphosate injury on tomato
§ Regional reports
§ Weather news
Next issue: July 16
Beth Bishop
Entomology
The first flight of European corn borer moths is winding down in most areas. The number of moths caught in pheromone traps during the past week (July 1 - 8) has decreased in most locations (see charts). However, any sweet corn with ears or snap beans or peppers with fruit are still at risk for corn borer infestation.
We continue to catch low numbers of corn earworm moths in pheromone traps (less than 1 or two moths per night). Corn earworm, a migratory pest, entered the state much earlier than usual this year and will be here for the rest of the season. Also, we can expect continued earworm migration as the season progresses and any strong weather fronts from the south can bring in large numbers of moths.
We are recommending sweet corn growers continue to treat sweet corn with ears and snap beans and peppers with fruit to prevent infestation by European corn borer and corn earworm. Right now we recommend a spray interval of five to six days. When populations of either pest start to increase or temperatures increase, this spray interval will need to be shorter.
Bt sweet corn is protected from European corn borer and should be safe from corn earworm given the low number of earworm moths present. Later in the season if corn earworm populations are higher and the silk starts to brown, one or two pyrethroid sprays may be necessary to prevent earworms in the tips of the ears.
Aster leafhopper numbers are moderately high in many celery
and carrot fields. The most recent results from tests of leafhopper aster
yellows infectivity show fairly high infectivity rates. Almost six percent of leafhoppers
collected from a carrot field in
These are higher infectivity rates than we have experienced
this time of year, especially for celery fields in southwest
Mary K. Hausbeck
Plant Pathology
As of this morning, July 9, downy mildew has been found in
|
Applied before disease (7-day intervals) |
|
Applied after disease (5-day intervals) |
|
Gavel 75WG (5 day PHI) |
|
Presidio 4FL (2 day PHI) |
|
Presidio 4FL (2 day PHI) |
|
Previcur Flex 6SC (2 day PHI) |
|
Previcur Flex 6SC (2 day PHI) |
|
Ranman 3.6SC (0 day PHI) |
|
Ranman 3.6SC (0 day PHI) |
|
Tanos 50WG (3 day PHI) |
|
Tanos 50WG (3 day PHI) |
|
|
|
Alternate products and mix each with either: Dithane (mancozeb) 3 lb or Bravo (chlorothalonil) 1.5 pt |
|
Alternate products and mix each with either: Dithane (mancozeb) 3 lb or Bravo (chlorothalonil) 2 pt |
|
Applied before disease (7- to 10-day intervals) |
|
Applied after disease (7-day intervals) |
|
Gavel 75WG (5 day PHI) |
|
Presidio 4FL (2 day PHI) |
|
Presidio 4FL (2 day PHI) |
|
Previcur Flex 6SC (2 day PHI) |
|
Previcur Flex 6SC (2 day PHI) |
|
Ranman 3.6SC (0 day PHI) |
|
Ranman 3.6SC (0 day PHI) |
|
Tanos 50WG (3 day PHI) |
|
Tanos 50WG (3 day PHI) |
|
|
|
Alternate products and mix each with either: Dithane (mancozeb) 3 lb or Bravo (chlorothalonil) 1.5 pt |
|
Alternate products and mix each with either: Dithane (mancozeb) 3 lb or Bravo (chlorothalonil) 2 pt |
Please note: Gavel 75WG and Dithane are not registered on some vine crops.
|
Date |
|
||||
|
Allegan |
Bay |
|
|
Cass |
|
|
June 2 |
S‡0 |
– |
– |
– |
– |
|
3 |
0 |
– |
– |
– |
S‡0 |
|
4 |
0 |
– |
– |
– |
0 |
|
5 |
0 |
S‡0 |
S‡0 |
0 |
|
|
6 |
0 |
0 |
S‡0 |
0 |
0 |
|
7 |
0 |
0 |
0 |
0 |
0 |
|
8 |
0 |
0 |
0 |
0 |
0 |
|
9 |
0 |
0 |
0 |
0 |
0 |
|
10 |
0 |
0 |
0 |
0 |
0 |
|
11 |
0 |
0 |
0 |
0 |
0 |
|
12 |
0 |
0 |
0 |
2 |
0 |
|
13 |
0 |
0 |
0 |
2 |
0 |
|
14 |
0 |
2 |
2 |
8 |
0 |
|
15 |
0 |
0 |
2 |
2 |
0 |
|
16 |
58 |
0 |
2 |
– |
0 |
|
17 |
15 |
0 |
0 |
– |
0 |
|
18 |
7 |
0 |
3 |
– |
0 |
|
19 |
2 |
0 |
10 |
3 |
7 |
|
20 |
3 |
38 |
*3 |
10 |
2 |
|
21 |
2 |
28 |
2 |
3 |
2 |
|
22 |
7 |
0 |
15 |
1 |
3 |
|
23 |
0 |
0 |
1 |
5 |
2 |
|
24 |
43 |
0 |
0 |
4 |
‡0 |
|
25 |
2 |
2 |
2 |
2 |
‡5 |
|
26 |
0 |
3 |
15 |
2 |
17 |
|
27 |
0 |
0 |
2 |
0 |
3 |
|
28 |
0 |
5 |
13 |
2 |
2 |
|
29 |
0 |
2 |
3 |
0 |
3 |
|
30 |
2 |
0 |
12 |
0 |
5 |
|
July 1 |
20 |
|
30 |
|
3 |
|
2 |
145 |
|
|
|
0 |
|
3 |
235 |
|
|
|
|
|
4 |
12 |
|
|
|
|
|
5 |
5 |
|
|
|
|
|
6 |
10 |
|
|
|
|
Phytophthora blight should be not forgotten, and will undoubtedly cause problems for processing growers as we reach harvesting. Pickle growers must remember the formula for protecting the fruit: Apply sprays when fruits are one inch, three inches, and five inches. Young fruit are especially susceptible and must be protected early. The fruit must be covered with the fungicide spray to be adequately protected. Covering only the foliage with fungicide is not good enough because the fungicide will not be absorbed by the foliage and moved into the fruit. This means that applying products by airplane is not considered the most effective means of protecting against phytophthora fruit rot.
Some fungicides offer control of both downy mildew and phytophthora. Last year in our phytophthora trials, Gavel and Presidio performed better than other products that were tested and are also products that protect against downy mildew. Since many pickle fields have phytophthora that is resistant to the Ridomil-type products, I hesitate to recommend them for use. Prior to fruit formation, I would recommend the downy mildew-only fungicides and once fruit have formed, move to products that provide protection against downy mildew and phytophthora.
Mary Hausbeck
Plant Pathology
Note: This
article was originally made available Thursday, July 3 in the web edition of
the Vegetable CAT Alert.
On July 2, a technician from my lab detected downy mildew on
cucumbers growing in
Be assured that my program has tested hundreds of fungicide programs. The only fungicides that we can recommend are those listed in the two tables below. However, if the intervals are stretched or the rates lowered, these programs will not protect cucumbers against downy mildew as the disease intensifies in the state. If you are growing other sorts of cucurbits such as pumpkins, zucchinis, gourds, or squash, it is important to note that these crops are not as susceptible to downy mildew as cucumbers. Sprays for these crops can be delayed until downy mildew is noted in that particular county as long as they are being scouted frequently. In past years, melons have become infected with downy mildew and should be treated with a protective fungicide program. For melons, the program can be a bit less intensive than the program recommended for cucumbers.
|
Applied before disease (7-day intervals) |
|
Applied after disease (5-day intervals) |
|
Gavel 75WG (5 day PHI) |
|
Presidio 4FL (2 day PHI) |
|
Presidio 4FL (2 day PHI) |
|
Previcur Flex 6SC (2 day PHI) |
|
Previcur Flex 6SC (2 day PHI) |
|
Ranman 3.6SC (0 day PHI) |
|
Ranman 3.6SC (0 day PHI) |
|
Tanos 50WG (3 day PHI) |
|
Tanos 50WG (3 day PHI) |
|
|
|
Alternate products and mix each with either: Dithane (mancozeb) 3 lb or Bravo (chlorothalonil) 1.5 pt |
|
Alternate products and mix each with either: Dithane (mancozeb) 3 lb or Bravo (chlorothalonil) 2 pt |
|
Applied before disease (7- to 10-day intervals) |
|
Applied after disease (7-day intervals) |
|
Gavel 75WG (5 day PHI) |
|
Presidio 4FL (2 day PHI) |
|
Presidio 4FL (2 day PHI) |
|
Previcur Flex 6SC (2 day PHI) |
|
Previcur Flex 6SC (2 day PHI) |
|
Ranman 3.6SC (0 day PHI) |
|
Ranman 3.6SC (0 day PHI) |
|
Tanos 50WG (3 day PHI) |
|
Tanos 50WG (3 day PHI) |
|
|
|
Alternate products and mix each with either: Dithane (mancozeb) 3 lb or Bravo (chlorothalonil) 1.5 pt |
|
Alternate products and mix each with either: Dithane (mancozeb) 3 lb or Bravo (chlorothalonil) 2 pt |
[Please note: Gavel 75WG and Dithane are not registered on some vine crops.]
|
Date |
|
||||
|
Allegan |
Bay |
|
|
Cass |
|
|
June 2 |
S‡0 |
– |
– |
– |
– |
|
3 |
0 |
– |
– |
– |
S‡0 |
|
4 |
0 |
– |
– |
– |
0 |
|
5 |
0 |
S‡0 |
– |
S‡0 |
0 |
|
6 |
0 |
0 |
S‡0 |
0 |
0 |
|
7 |
0 |
0 |
0 |
0 |
0 |
|
8 |
0 |
0 |
0 |
0 |
0 |
|
9 |
0 |
0 |
0 |
0 |
0 |
|
10 |
0 |
0 |
0 |
0 |
0 |
|
11 |
0 |
0 |
0 |
0 |
0 |
|
12 |
0 |
0 |
0 |
2 |
0 |
|
13 |
0 |
0 |
0 |
2 |
0 |
|
14 |
0 |
2 |
2 |
8 |
0 |
|
15 |
0 |
0 |
2 |
2 |
0 |
|
16 |
58 |
0 |
2 |
– |
0 |
|
17 |
15 |
0 |
0 |
– |
0 |
|
18 |
7 |
0 |
3 |
– |
0 |
|
19 |
2 |
0 |
10 |
3 |
7 |
|
20 |
3 |
0 |
*3 |
10 |
2 |
|
21 |
2 |
38 |
2 |
3 |
2 |
|
22 |
7 |
28 |
15 |
1 |
3 |
|
23 |
0 |
0 |
1 |
5 |
2 |
|
24 |
43 |
0 |
0 |
4 |
‡0 |
|
25 |
2 |
|
2 |
2 |
‡5 |
|
26 |
0 |
|
3 |
2 |
|
|
27 |
0 |
|
0 |
0 |
|
|
28 |
0 |
|
5 |
2 |
|
|
29 |
0 |
|
2 |
0 |
|
|
30 |
|
|
0 |
0 |
|
Mary Hausbeck
Plant Pathology
Based on the disease outbreaks that we are seeing, I could swear that it is the middle of August. The wet weather early on in the growing season coupled with some warm nights has set us up for trouble on several fronts. I fully anticipate that this season will be tough on growers who are trying to rein in spots, blights, mildews and rots. Here’s the scorecard:
Cercospora is a
fungal pathogen that has been found in two areas of the state. This pathogen
causes a blight that affects both old and young foliage. Small, circular
lesions occur at first, but expand to affect large portions of the leaves. Cercospora
can develop quickly and is often more difficult to control than alternaria
blight. When cercospora develops on the petioles of the carrots they become
weakened and yield is negatively impacted. Fields with this disease can be
treated with fungicides including chlorothalonil (ex. Bravo) and the
strobilurins (Quadris, Cabrio, Pristine, or
Bacterial blight has also been confirmed in a processing carrot field. This particular sample was especially disturbing because of the extensive amount of infection and blighting of the young, expanding leaf tissue. In some instances, bacterial blight on carrot can look dark and almost oily. However, this disease can also appear as a light brown blight that can resemble Alternaria. Bacterial blight can infect young foliage much like Cercospora blight whereas Alternaria blight infects older, senescing leaf tissue. Bacterial blight cannot be managed with those products used to limit Alternaria and Cercospora. Only copper-based products limit bacterial blight. Copper sprays must be applied frequently (minimum every seven days) with thorough coverage of the foliage (no skimping on the amount of water in the spray tank). The TOM-CAST program cannot be used to time sprays for bacterial blight. Copper sprays are limited in what they can offer for bacterial blight of carrot. If the spray interval is stretched beyond the seven days, then the copper applications cannot offer help. The coppers can help limit the spread of the disease and protect the newly emerging foliage. Coppers can reduce the severity of the disease, but they will not cure the blight.
Rust and purple spot were problems early on this spring, so I don’t expect them to go away this summer. The TOM-CAST system can be used to time fungicide sprays for purple spot on asparagus fern. The primary fungicide that is recommended for use against purple spot is Bravo. Rust is controlled through applications of Folicur that can be alternated with Bravo (chlorothalonil). The TOM-CAST program cannot be used to time fungicide sprays for rust. In cases where disease is not yet established, Mancozeb can be used in place of Bravo to maintain a level of protection. However, if disease is detected, Bravo will be better able to limit both purple spot and rust and will weather better than Mancozeb during wet periods. Asparagus growers should do everything they can do to protect their fern and maintain its vigor into the fall. Green, healthy fern will produce the carbohydrates needed for yields next year.
Powdery mildew has been found in two locations within the state. Yes, this is a full month earlier than what we would expect. However, it is not the first time that we’ve had powdery mildew occur prior to the Fourth of July. Scouting will be the key in being able to delay powdery mildew fungicide applications. By scouting, I mean walking the field and looking for the white powdery colonies on the lower leaves and the undersides of the leaves. Scouting via a pick-up truck going down the road at 50 mph doesn’t count.
Once the very first powdery mildew colonies are observed, a
spray program should begin immediately. Growers differ in the types of products
that provide a good level of control. While some growers are satisfied with
Nova and the strobilurins (Cabrio,
Phytophthora crown rot is affecting some pepper fields in
the state. We have two field plots testing a commercially resistant cultivar
against a susceptible cultivar. Both the resistant and susceptible cultivars
are being sprayed with several different fungicide programs. This research is
being conducted in my program by Jennifer Foster, a Master’s student from
Steven Gower
MSU Diagnostic Services
Several tomato samples have been submitted to the lab over the past ten days with symptoms consistent with glyphosate injury. In most of these cases, the injury resulted from glyphosate spray drift mostly likely from neighboring corn and soybean fields. Occasionally, the injury resulted from glyphosate contamination in the tank used to apply pesticides to the tomatoes.
Specific symptoms of glyphosate injury will vary depending on several factors including exposure dose, tomato growth stage and growing conditions after exposure. Glyphosate is translocated inside the plant to the newest meristematic regions; therefore the newest growth will be most injured.
Tomatoes injured with glyphosate will have distorted new growth with cupped, fringed and small leaflets. Often, the newest leaves will contain a proliferation of buds and small leaflets. Many of the leaflet bases will contain a yellow to white discoloration –a diagnostic clue of glyphosate injury on tomato.
Hail damages central
On Wednesday, July 2, near
Ron Goldy
Temperatures were near normal for the period with lows from 48°F to 69°F and highs from 71°F to 86°F. There was one to four inches of rain across the immediate area.
Watermelon and cantaloupe have softball-sized or larger fruit.
Cucumber, yellow squash and zucchini harvest continues with volume increasing as direct seeded fields come into production.
Pumpkins and fall squash are blooming and runnering. Growers need to be aware of squash vine borer activity at this time and protect susceptible plants. Powdery mildew has been found on squash and pumpkins.
Pepper, eggplant
and tomatoes are growing well with
increased temperatures. Tomato harvest from tunneled fields will begin soon.
Sweet corn harvest from row covered plantings began over the weekend. Some smut and Stewart’s wilt is present in some fields.
Green bean harvest has begun.
Tarnished plant bug populations have greatly increased and need to be controlled in susceptible crops. An increase in mite populations has also been noticed.
Bill Steenwyk
Crop report
On muck soils, crop progress depends on the degree of
rainfall and how well water is carried away from the field. In much of southern
The second radish crop appears to be doing well.
On upland soils most crops are doing fairly well, although I
will soon investigate reported hail damage in central
Throughout the area, sweet corn growth ranges from the two-leaf to late-silk stage.
Cabbage is being harvested while new transplants begin growth. Vine crops and upland cabbage looks good.
Tomatoes and peppers look good overall and are developing fruit.
Norm Myers
The last producing asparagus fields were shut down around July 3, making 2008 one of the latest harvest seasons in recent memory. While official numbers haven’t been published yet, the total crop produced a few million pounds more than last year, but still fell short of the state’s five-year averages. Wet weather has increased the threat of foliar diseases, especially in young fields where fern is well established.
Mary Hausbeck’s lab identified bacterial blight in
Zucchini, pumpkins and pickles are emerging normally and growers are sending hoeing crews through to control weeds flushed by the heavy rains.
The early July snap bean plantings have mostly emerged and stands look good so far.
In sweet corn, warmer weather has improved growth in July, but the crop is still way behind normal.
Jim Breinling
Temperatures have been seasonal during the past two weeks.
Rainfall amounts in the area have been variable but the end results have been
about the same. At the Fremont
Enviro-weather
station, 1.86 inches has been reported in the past two weeks, with 1.46 of this
total received on July 2. Growers near the
Growth of carrots has progressed nicely the past two weeks. Fields of dicer type processing varieties are now developing rots at 0.50 to 0.75-inch diameter. As reported earlier there are some thin stands in some fields and more notably on the fields where soils are lighter and sandier.
Onions have not started to bulb yet, but fields look good with growth at the six leaf stage and 15 to 18 inches in length.
Spinach harvest was completed on July 3.
Harvest of turnips
and beets is underway in
Fields of winter squash are now growing well and beginning to run with plants 18 to 24 inches in length. Cucurbit crop growers in the area have been alerted regarding control measures for downy mildew.
Snap bean growth at the Mason County European corn borer site is now at the first trifoliate stage. European corn borer trap counts on July 8 were 1 - 0 - 2.
Corn earworm trap catch at the
Sudeep Mathew
We have received plenty of rain in the past two weeks. There
are some wet pockets in most fields with dying plants. According to the Enviro-weather
station in
Sweet corn is making very good growth. Harvest has begun in some early planted under tunnels fields. In general, most of the fields are in silking stage. Many growers expect to begin harvest next week.
Peppers are looking good. Most plants are setting very good fruit. Some farmers have started to harvest. There is some water injury to peppers in the low lying areas of many fields.
Cucumber fields are developing well although cucumber downy mildew was identified last Wednesday in one local field. Since we are in a period of high precipitation, a weather pattern which is very conducive for spore development, growers need to pay a close attention to restrict further spread of the disease. Cucumber beetles are present in many cucumber fields.
Pumpkins, melons and squashes are improving. Pumpkins have flowers in many fields.
Market tomatoes are just starting to be harvested and have very nice fruit quality. There is good fruit load in many early planted market and processing tomato fields. There are not any severe insects or diseases present at this time. I saw two processing tomato fields with herbicide drift appeared to have come from adjacent glyphosate resistant corn fields.
Potatoes are in a variety of growth stages from maturing vines to tuber settings. I have seen some early symptoms of rhizoctonia (Photo 1) on some table stock varieties. Colorado potato beetle (Photo 2) activities have been found in several fields. Most of them are in high numbers and growers are following spray schedules.
Aaron Pollyea
Geography
Clear skies and less humid conditions prevail after the
passing of the cold front on Tuesday, July 8. With higher pressure moving into
the region, clear or partly cloudy skies will be the norm for our state. A warm
front looks as though it will be passing through the region on Friday,
producing rainfall across the central part of the Lower Peninsula to the
Temperatures during the next few days will be lower because of the cold front that passed through our region, with highs Wednesday generally ranging from the mid-60s in the north to the low 80s south and lows Wednesday night and Thursday morning from the mid-40s north to the low 60s south. Temperatures will be variable from day to day across the state until Sunday when they become steady after the passage of the frontal system. On Thursday, highs will be in the low 70s in the north to low 80s in the south. Friday will see highs in the upper 70s to upper 80s with some thunderstorms. For the weekend, temperatures will be in the upper 70s in the north to upper 80s in the south.
The National Weather Service 6‑10 day outlook covering July 14 through July 18 calls for normal temperatures and precipitation across the state. The outlook for the 8-14 day period (July 16 - 22) calls for above normal temperatures and near normal precipitation. The long term outlook shows that conditions for the rest of the month should be near normal, with a gradual shift back to a more seasonable range in conditions.