East Michigan vegetable update – Aug. 15, 2018

Benjamin Phillips<benp@msu.edu> - August 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 40^th 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.

This article was published by Michigan State University Extension. For more information, visit https://extension.msu.edu. To have a digest of information delivered straight to your email inbox, visit https://extension.msu.edu/newsletters. To contact an expert in your area, visit https://extension.msu.edu/experts, or call 888-MSUE4MI (888-678-3464).