East Michigan vegetable update – Aug. 2, 2017

Harvest of most crops is fully underway, while growers are finishing up last plantings of fall-harvested cole crops.

Western bean cutworm moths lay their eggs on sweet corn leaves in small clusters, about the size of a dime. With low earworm and corn borer populations and sprays, this pest could do some nibbling on pre-tassel sweet corn. Photo by Christina DiFonzo, MSU.

Western bean cutworm moths lay their eggs on sweet corn leaves in small clusters, about the size of a dime. With low earworm and corn borer populations and sprays, this pest could do some nibbling on pre-tassel sweet corn. Photo by Christina DiFonzo, MSU.

Weather

Last week was relatively dry across our region, and the next 1.5 weeks will feel like an early fall, with extended dew periods and lower temperatures. Disease pressure will shift accordingly.

The table below shows growing degree-day (GDD) base 50 degrees Fahrenheit since March 1, rainfall accumulations in inches since April 1 and soil temperature ranges (Fahrenheit over the last week) to date from Michigan State University Enviro-weather stations in the region.

GDD and rainfall accumulations as of Aug. 2, 2017

Location

GDD (+ added from last week)

GDD 5-year average

Rainfall (+ added from last week)

Rainfall 5-year average

Emmett

1,570 (+ 288)

1,608.4

12.44 (+ 0.65)

10.57

Fairgrove

1,571 (+ 277)

1,620.7

9.34 (+ 0.00)

11.55

Flint

1,755 (+ 312)

1,729.6

15.11 (+ 0.33)

13.70

Frankenmuth

1,634 (+ 283)

1,669.3

13.69 (+ 0.73)

11.51

Freeland

1,602 (+ 285)

1,644.8

18.91 (+ 0.87)

11.75

Lapeer

1,592 (+ 274)

1,648.9

11.75 (+ 0.68)

13.42

Linwood

1,506 (+ 276)

1,551.2

21.07 (+ 1.04)

12.10

Munger

1,624 (+ 298)

1,659.9

13.66 (+ 0.80)

10.69

Romeo

1,701 (+ 322)

1,683.3

12.52 (+ 0.23)

11.51

Sandusky

1,488 (+ 275)

1,549.7

13.25 (+ 1.68)

11.84

Crops

Corn earworm catches remain low in sweet corn. However, look out for western bean cutworm eggs. Normally, this pest would be controlled during earworm sprays. Their eggs can be found on the tops of corn leaves in small, tight clusters that turn purple over time. They are about the size of a dime.

Carrots are being harvested, measuring up to 10 inches long and up to 1 inch in diameter.

Head lettuce harvest is continual, and has seen very favorable weather for maximum shelf life.

Machine-harvested pickles started two weeks ago. One tank yard reported having one-third of their contracted acres harvested.

Cantaloupes are being harvested, but watermelons are still sizing. Based on last week’s quick question, many growers are checking for brown tendrils to indicate watermelon ripeness. It is common to check three leaf nodes: the node where the fruit is, and the two leaf nodes just up and down the vine from it. When they are all brown, the fruit is ready.

Other growers use the thumping method to listen for a hollow sound to determine ripeness. An unripe watermelon can have a duller sound, as the pulp is denser. However, an overripe watermelon can also sound hollow.

Fewer growers use the yellowing ground spot as an indicator, probably because of how different varieties have different ground spot tendencies. Even fewer cut open fruits in the field. I found that surprising, as it is the only true way to check your work, like biting into a green bell pepper.

I found gummy stem blight at one field. It is commonly a foliar blight and also scars the stems of plants. It will sometimes also create a black rot on the fruit. MSU Extension advises caution when treating this disease at this point in the season with harvest very close. Most of the effective products (Inspire Super, Luna Experience, Monsoon, Toledo and Vibe) have a seven-day pre-harvest interval and also work well against powdery mildew. However, Switch has a one-day pre-harvest interval and Bravo can still be used as a protectant to prevent gummy stem blight spores from infecting new plants, and has a zero-day pre-harvest interval.

Winter squash and pumpkins are still setting fruit. It is common to see aborted fruit at this time. Sometimes this is pollination-related, but if there are fruit on the vine already, it is likely the plant is just limited by its basic biology. Large-fruited varieties tend to set fewer fruit than small-fruited varieties. Once the plant has set as much as it can handle, it will not allow more fruit to grow.

For powdery mildew, choose a three-product rotation from any of the following effective products, tank-mixed with Bravo and a surfactant. They all work well.

  • Torino (zero-day pre-harvest interval)
  • Quintec (two-day pre-harvest interval)
  • Procure (two-day pre-harvest interval)
  • Rally (zero-day pre-harvest interval)
  • Pristine (zero-day pre-harvest interval)

In addition, there are a number of fungicides that work well on powdery mildew and gummy stem blight, if you are looking for a double-whammy (see the melons section above).

Fresh market field tomato picks are continuing. Yellow-shoulders can be prevalent in some varieties and is mostly caused by environmental conditions. Yellow-shoulders is a disorder caused by nutrient imbalance, organic matter and temperature. The Hartz ratio determines the risk of yellow-shoulders development based on a soil test. If this is something you experience frequently, and across multiple varieties, it may be worth taking a soil test and calculating a Hartz ratio. Ohio State University has a nice, online “Hartz” Ratio calculator that can help guide fertility decisions regarding this issue.

Pepper harvest is just beginning. I received one report of phytophthora leaf blight, which is a common issue in pepper. It was likely brought on from the high volume of rain received in the area back in June. Fungicides applied for phytophthora blight are most effective if applied when disease threatens, but before symptoms become severe.

If foliar and fruit rot phases are already advancing, apply a two- or three-product rotation of products to slow the spread, taking notice of pre-harvest intervals when close to harvest. Orondis Ultra (zero-day pre-harvest interval), Presidio (two-day pre-harvest interval), Ranman (zero-day pre-harvest interval), Revus (one-day pre-harvest interval) and Tanos (three-day pre-harvest interval) can be applied foliar, while Omega 500F, Zampro and Ridomil Gold SL may be applied as a transplant drench in problem fields.

Brussels sprouts should be topped to stop upward growth. The plant will then focus on bulking up the sprouts in the leaf nodes. Some growers have already done this back in July. Sometimes, deer do it for you, but they are notoriously unreliable and thieving workers.

Based on the responses to last weeks’ quick question, cauliflower size diversity is important. So, what does that mean? It could mean a section of cauliflower planted closer together. It could also mean using larger in-row spacing, but tying and harvesting some plants earlier, making room for neighboring plants to grow a little more. Once tied, cauliflower heads tend to slow their growth compared to un-tied. You could effectively create larger and smaller cauliflower based on tying time.

Upcoming events

The Midwest Mechanical Weed Control Field Day is Sept. 26 at the MSU Horticulture Farm. For more information and registration, see “Midwest Mechanical Weed Control Field Day.”

Hotels are filling up for the Great Lakes Fruit and Vegetable EXPO, Dec. 5-7 in Grand Rapids, Michigan. The combination of grower-focused, research-backed presentations and an amazing exhibit hall make it a can’t-miss event.

Please contact me at .(JavaScript must be enabled to view this email address) or 616-901-7513 to pick up any suspected disease samples from your farm, or send the diseased plant parts to MSU Diagnostic Services.

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