East Michigan vegetable update – Aug. 15, 2018

An update on corn earworm, potato/tomato late blight, onion leaf blights and cucumber phytophthora fruit rots.

Weather

Weather forecasts through September are calling for above-average temperatures. Strawberries should respond well to this.

Click the links below to view maximum and minimum air temperatures, as well as degree-day and rainfall accumulations from Jan. 1 through the last 14 days.

Crops

All heading brassicas harvest continues. Caterpillars remain below thresholds at all sites. Swede midge trap catches remain at mostly less than five per trap. However, one organic site has seen a 30-fold increase in swede midges in just one week, going from one per trap to 30 per trap. This tells me there has been a hatch and pressure will mount until frost as long as cole crops are present. Cabbages will be more resistant to damage if they have already starting to form a head, but cauliflower and broccoli will be particularly vulnerable.

Pickling cucumber harvests are rolling. Downy mildew reports are still coming in from the Thumb and southeast Michigan. It is a good time to use Ranman or Orondis Opti on new and older crops. Orondis can only be 30 percent of the total spray program.

Phytophthora fruit rots are showing up in some areas. There are many preventative actions that can be taken to combat Phytophthora, including field selection, equipment sanitation and irrigation source selection and timing. In a field with a known problem, preventative fungicides must contact the fruit. Sprayers must provide good canopy penetration when fruit are 1, 3 and 5 inches long.

Phytophthora fruit rot preventative fungicides

Product

Mode of action

Rate

PHI/REI

Elumin
ethaboxam

22

8 ounces per acre. Tank-mix with a protectant. Apply as soil or foliar spray or via drip.

2 days/12 hours

Orondis Gold 200
oxathiapiprolin)

49

Follow label. Apply at-plant in-furrow or via drip after emergence. Must not exceed 33 percent of spray program.

0 day/4 hours

Orondis Ultra
Oxathiapiprolin +
mandipropamid

49 + 40

Follow label. Use soil or foliar spray. Must not exceed 33 percent of spray program.

0 day/4 hours

Presidio 4SC
fluopicolide

43

3-4 ounces per acre. Tank-mix with protectant. Apply as soil or foliar spray.

2 days/12 hours

Revus 2.08SC
mandipropamid

40

8 ounces per acre. Include surfactant.

0 day/4 hours

Apron XL LS
mefenoxam

4

Follow seed treatment instructions.

Not available/48 hours

Ridomil Gold
mefenoxam

4

1–2 pints per ac. Apply as pre-plant incorporated, at-plant soil spray or via drip.

7 days/48 hours

Forum 4.18SC
dimethomorph

40

6 ounces per acre. Tank-mix with a protectant.

0 day/12 hours

Gavel 75DF
mancozeb +
zoxamide

M3 + 22

1.5–2 pounds per acre.

5 days/48 hours

Ranman 400 SC
cyazofamid

21

2.75 ounces per acre. Include surfactant.

0 day/12 hours

Zampro 4.4SC
ametoctradin +
dimethomorph

45 + 40

14 ounces per acre. Apply as foliar spray or drip.

0 day/12 hours

In onions, some field curing and harvest has begun. Some field curing has been premature due to stemphylium leaf blight. Mary Hausbeck’s lab has trialed fungicides for this disease and found the Luna line of products is working exceptionally well. Quadris and Cabrio were not looking better than the untreated control. Bravo has been working better than Manzate.

Stemphylium leaf blight preventative fungicides

Product

Mode of action

Rate

PHI/REI

Luna Experience
fluopyram +
tebuconazole

7 + 3

12.8 ounces per acre.

7 days/12 hours

Luna Tranquility
fluopyram +
pyrimethanil

7 + 9

16–27 ounces per acre.

7 days/12 hours

Bravo
chlorothalonil

M5

Various rates depending on formulation.

0 day/12 hours

Omega 500F
fluazinam

29

1 pint per acre.

7 days/12–24 hours, see label

Tilt
propiconazole

3

4–8 ounces per acre solo.

2–4 ounces per acre with tank-mix protectant.

14 days/12 hours

Tebuzol 3.6F
tebuconazole

3

4–6 ounces per acre.

7 days/12 hours

Aprovia Top
difenoconazole +
benzovindiflupyr

3 + 7

10.5 ounces per acre.

7 days/12 hours

Late blight in potatoes has been detected in Monroe County, Michigan. Disease severity values indicate a medium to high potential for infection if spores move to our area due to favorable weather conditions. Chlorothalonil is a very useful tool for preventing infection in both tomatoes and potatoes.

Sweet corn is now under heavy corn earworm pressure. Field corn silks have dried and sweet corn has the only fresh silks for the moths to lay eggs on. Bt hybrids can handle the caterpillars when their silks are fresh, but as they dry, their efficacy declines and sprays are still required.

There are a few different threshold recommendations, but the Midwest Vegetable Production Guide recommends treatment is justified when green silks are present and moths are being caught. If it’s over 80 degrees, spray more often than every five days. Pyrethroids (mode of action 3A) still work, but consider-tank mixing or rotating to different modes of action, including Lannate (methomyl 1A), Coragen (chlorantraniliprole 28) or Radiant (spinetoram 5). Besiege is a premix of chlorantraniliprole (28) and lambda-cyhalothrin (3A).

Treatments can cease when 90 percent of silks are brown.

Corn earworm preventative insecticides

Product

Mode of action

Rate

PHI/REI

Brigade
bifenthrin

3A

3 ounces per acre, 12.8 ounces per season.

1 day/12 hours

Mustang Maxx
zeta-cypermethrin

3A

3.5 ounces per acre, 24 ounces per season.

3 days/12 hours

Warrior II
lambda-cyhalothrin

3A

1.5 ounces per acre, 30.72 ounces per season.

1 day/24 hours

Baythroid
beta-cypermethrin

3A

2 ounces per acre, 28 ounces per season.

0 day/12 hours

Lannate
methomyl

1A

1.5 pints per a.

0 day/48 hours

Coragen
chlorantraniliprole

28

4 ounces per acre.

1 day/4 hours

Radiant
spinetoram

5

5 ounces per acre, 6 applications per season.

1 day/5 hours

Besiege
chlorantraniliprole +
lambda-cyhalothrin

28 + 3A

8 ounces per acre, 31 ounces per season.

1 day/24 hours

Meetings

Aug. 21, 8 a.m. – 4:15 p.m. Biological Control in Protected Agriculture: Strategy & Planning Short Course at Great Lakes Greenhouse, 6573 East N Avenue, Kalamazoo, MI 49048. This course places emphasis on controlling insect pests in spring floriculture crops, but is highly applicable to other crops grown under protection. Event registration is $125 (lunch included).

Aug. 27. Curious about using drones in agriculture? Attend the Tri-State UAV Field Day in Ohio. Contact Ricardo Costa at costasil@anr.msu.edu or 573-639-8971 for more information and registration.

Sept. 19, 8:30 a.m. – 1:30 p.m. Organic Management Field Day at the MSU Kellogg Biological Station, 9701 N 40th St, Hickory Corners, MI 49060. Lunch is included.

Sept. 26, 9:30 a.m. – 4 p.m. The Midwest Mechanical Weed Control Field Day at PrairiErth Farm, 2073 2000 Ave, Atlanta, IL 61723. See in-row cultivation tools demonstrated on vegetable crops, with a trade show, and grower experiences with mechanical cultivation. Event registration is $20 (lunch included). Check it out on Facebook. 

Dec. 4-6. It is never too early to make accommodations to attend Great Lakes Fruit and Vegetable EXPO in Grand Rapids, Michigan. Hotel blocks are open and tend to go fast. The combination of grower-focused, research-backed presentations and an exhibit hall featuring a diverse set of vendors make it a can’t-miss event.

Need your water tested for the Food Safety Modernization Act (FSMA)? Check out the Michigan Ag Water Lab Map.

Please contact me at phill406@msu.edu or 616-901-7513 with questions, concerns or to schedule a farm visit. You can also send plant materials to MSU Diagnostic Services.


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