The following sweet corn performance trial report was compiled by Mike Gastier (gastier.3@osu.edu), OSU Extension, Huron County; Matthew Hofelich (hofelich.4@osu.edu), OARDC, Fremont; and Allen Gahler (gahler.2@osu.edu), OSU Extension, Sandusky County.

Refer any questions or inquiries about this project directly to these authors.

Sweet corn hybrid trial.

Summary
Sweet corn is an important crop in both the fresh market and shipping market in North Central Ohio, where a significant percentage of Ohio vegetables are grown.  Many different varieties of sweet corn are grown by producers with fresh market roadside stands, and still others are grown for early, mid, and late season shipping and processing markets, meaning growers demand a diverse selection of sweet corn varieties and maturities.  Growers have indicated this diversity should focus on SH₂ varieties with different stages of maturity, and variance in other traits.  Many new varieties are becoming available to meet these grower demands, and this study sought to determine which ones would perform acceptably in Northern Ohio, and which would have the desired traits growers are seeking.  For this trial, 34 SH₂ varieties were grown in 4 replicated plots at the Ohio State University’s North Central Agricultural Research Station near Fremont, Ohio.

For the full report and results as a PDF, click here.

There are literally hundreds of commercially available pumpkin and squash hybrids on the market today. For the past 20 years we have tried show a small sample of what is available for growers to take a look at during our annual pumpkin field day. The primarily purpose of the trial is to evaluate disease resistance to powdery mildew but also for fruit size, shape, color and yield.  Although the field day was held virtually this year, here are some details about the trial including a group photo (Figure 1) plus individual statistics about each squash and pumpkin hybrid.

2020 Pumpkin and Squash Fruit Group Photo.

The trial was direct seeded on June 1 into plots 50’ long with a row spacing of 15’. The final seed spacing in each row was 3’ – 4’ allowing for 12 or 13 plants per plot. Strategy (4.5 pt/A) and Dual Magnum (1.3 pt/A) were applied for weed control pre-emerge on June 2. Later emerging weeds were removed from the plots throughout the season. Soil testing for P and K were sufficient in that field so only nitrogen was applied side-dressed at 65 lb N / A using liquid 28-0-0 on June 26. The plots were managed for powdery mildew upon first detection on July 27, with the first fungicide spray applied on July 29. Future sprays were alternated on a 7-10 day schedule with the last application on September 4. An early harvest occurred on Aug. 12 and 18 to accommodate the filming of the virtual pumpkin field day. It is important to underscore that because the harvest was conducted prior to all immature fruit sizing and maturing, the number of marketable fruit and therefore the estimated yield values are all below their full yield potential. For the fruit that were mature at harvest, the average weight should be fairly accurate under our trial conditions. Realize also that these hybrids planted in your spacing regime may have different results than this trial. Overall, the trial received 6.8 inches of rain from June 1 – September 1.

The hybrids are listed by their seed company, powdery mildew rating (none, PM tolerant, PM resistant) and days to maturity (Table 1). The same list is also shown with the range of fruit weight, average weight, number of marketable fruit, and estimated fruit and tonnage per acre (Table 2).

Table 1. Data related to hybrids in trial.

Table 2. Physical data associated with trial harvest.

* seed received and planted ca. 1 month later than other hybrids leading to immature fruit at harvest.
** calculated using 50ft row length with 15ft row centers.
*** missing plants in plot leading to fewer fruit and reduced yield.

For a more detailed review of the fruit and foliage, view the Virtual Pumpkin Field Day Video from 52:84-68:43.  You can also take a look at the hybrids using the 3D Field Scale Model. Click the play button and then anywhere on the model or use the shortcuts in the left hand pane.

A total of 61 people signed up for the 2020 Virtual Pumpkin Field Day which premiered last week on August 27. If you weren’t able to participate in the field day last week, you can still watch the whole program which is posted here: https://u.osu.edu/jasinski.4/pumpkins/.

Since this is our first time doing a video based field day, take 3 minutes and tell us what you learned, liked or didn’t like. https://www.surveymonkey.com/r/vpumpkin20impact.

Also on the main pumpkin page you will find additional pumpkin related resources including past reports on powdery mildew management, hybrid trial results and other information.

The pumpkin field day video has been viewed 74 times and is hosted on the OSU IPM YouTube channel https://go.osu.edu/osuipm.

OSU pumpkin page with lots of resources.

Dr. Celeste Welty accepts the Golden Pumpkin Award.

Dr. Celeste Welty was awarded the highly treasured Golden Pumpkin Award at the 2020 Virtual Pumpkin Field Day on August 27^th. This is Celeste’s last pumpkin field day in light of her expected retirement at the end of the year. This award recognizes her 33+ years of research and extension contributions not only the pumpkin growers of the state but also the small fruit and tree fruit growers. This award is on par with the Oscar, Emmy and Tony; certainly far above the pedestrian Golden Globe. If you care to wish Celeste well in her retirement, feel free to drop her a line at welty.1@osu.edu.

As expected, Covid-19 has slowed many things in Ohio but one of them is NOT spotted wing Drosophila! Ohio State University Extension, the Department of Entomology, and the IPM Program have again set up a statewide SWD monitoring program for this pest in 11 counties. The Scentry lure baited traps were deployed the week of June 15, and the first trap checks for positive male or female SWD occurred this week.

SWD trap.

As of Friday June 26, three counties reported positive identifications of SWD; Champaign, Greene and Franklin. Other counties are likely positive but have not been reported as of yet. Recall that the threshold for this pest is one fly, which triggers an insecticide spray program if the berries are ripening or ripe through harvest. Details on spray programs can be found here: https://cpb-us-w2.wpmucdn.com/u.osu.edu/dist/1/8311/files/2019/11/SWD_Ohio_handoutV19.pdf

If you have ripe berries and have not been spraying, your chance of infestation is still likely low but you may consider looking for larvae in the fruit using a salt water test. The process is fairly simple and can be found here: https://youtu.be/MtMXHxqcSVs.  While on the OSU IPM YouTube site look around at our other SWD videos if interested in identification, trap set up and deployment or exclusion netting.

Although it’s been wet over most of the state recently, the temperatures are warming up allowing growers to get into their fields to direct seed or transplant pumpkin, squash, melon and cucumbers through May and into June. By now most decisions about how to manage key early season pests may have already been made with the purchase of systemic seed treatment or plans to treat transplant water using neonicotinoid insecticides. Some growers may have decided to forego systemic treatments and rely on scouting and treatment using foliar insecticides when thresholds are exceeded.

Systemic Insecticide Use Considerations
Seed treatments containing thiamethoxam (FarMore FI400, Cruiser) offer maximum protection against cucumber beetles and other pests for about 2 to 3 weeks after seedling emergence. Seed treatments offer little protection to transplanted crops. For transplants and direct-seeded plants over 3 weeks old, the concentration of insecticide from seed treatment is no longer strong enough to kill beetles but can still harm bees due to sublethal doses in the pollen and nectar. Treated seed should never be used in combination with at-plant soil drenches with flupyradifurone (Sivanto), imidacloprid (Admire or generics), or thiamethoxam (Platinum). At-plant soil drenches used alone, with non-treated seed, offer similar protection to treated seed for beetle control. Due to increased residues in nectar and pollen, in-furrow applications should be considered last and applied at the lowest recommended rate that provides control. Non-systemic foliar applications of insecticides can be used to control cucumber beetles if seed or in-furrow treatments were not used, or were ineffective. Once flowers are present, applications should be made in the evening when flowers are closed and bees are not actively foraging, which minimizes the risk to pollinators.

Beetles killed by systemic insecticide.

Thresholds range from 0.5 to 1 beetle per seedling, and 1 to 5 beetles per plant for plants after 4 leaf stage. The threshold for cantaloupe melons and cucumber is lower because these crops are susceptible to bacterial wilt, which is vectored by cucumber beetles. Pumpkin, squash, and watermelon have higher thresholds because these crops are less susceptible to bacterial wilt, but beetle feeding can occur on the fruit rind by both adult and larvae, causing marketable loss. Beetles found in pumpkin or squash flowers do not pose a risk to the plant but as flowering decreases, rind feeding may increase.

Key Pest #1 – Striped cucumber beetle. This small black and yellow striped beetle is a major pest of all cucurbits early season.  In addition to the heavy feeding damage that can be inflicted upon seedlings, this feeding injury can also transmit bacterial wilt to the plant which will stunt or kill the plant.  Growers can control this pest in several ways such as buying Farmore FI400 treated seed, which contains several fungicides paired with thiamethoxam that provides seedling protection for 2-3 weeks after emergence. Using an in-furrow treatment of a systemic insecticide at planting will provide a longer window of control, between 4-6 weeks. Another management option is to scout for beetles on emerged seedlings, and based on seedling stage, use a foliar spray when the threshold is exceeded according to the guide below:

0.5 beetle per plant for cotyledon through 1^st leaf
1 beetle per plant for 2^nd and 3^rd leaf
3-5 beetles per plant for anything after the 4^th leaf stage

Regardless of method of treatment, be sure to scout for these beetles and damage on the underside of the cotyledons and early leaves every few days, because severe damage can occur rapidly in a short period of time.  Pollinators can also be affected by systemic insecticides present in pollen and nectar, so seed treatments to some degree but more so in-furrow products should be considered for risk before use. Foliar applications of insecticides should be made in the evening to minimize pollinator impact.

Striped cucumber beetle.

Cucumber beetle leaf feeding injury, check cotyledons.

Key Pest #2 – Squash Vine Borer (SVB). The damaging stage of this pest is a caterpillar that emerges from an egg laid by a moth that mimics a wasp. SVB adults becomes active in early June and the best management practice for this pest is to put up a pheromone trap next to the cucurbit field and monitor the number of moths caught. A week after adult moths are caught in the trap, usually around mid to late June, apply an insecticide targeted at the base of the plants where the eggs are laid for up to four weeks. If the caterpillar bores into the stem of the plant, treatment will not be effective.  Systemic products such as imidacloprid, used either as a seed treatment or in-furrow application at planting, will not control this pest.

Bag full of SVB adults captured by trap in background.

Squash vine borer larva in vine.

SVB occasionally attack fruit.

Squash vine borer adult.

Key Pest #3 – Squash Bugs. These true bugs overwinter as adults in nearby fields and can attack seedling and smaller plants with sucking mouth parts that can collapse leaves and stems. These pests can also vector yellow vine decline (YVD), caused by a bacterial pathogen that can cause stunting and death in young plants. Plants infected with YVD will turn yellow about one month after being infected, and there is no remedy for infected plants.  If more than one egg mass per plant is found, treatment is warranted once the nymphs hatch.  If nymphs mature to adults, they are harder to control. Plantings treated with imidacloprid drench in furrow usually are well protected from squash bug.

Squash bug eggs.

Squash bug nymphs.

Squash bug adult.

Symptoms of yellow vine decline.

Key Pest #4 – Seedcorn Maggot. The seedcorn maggot feeds on organic matter in the soil, including seeds before or after sprouting. This pest can be a problem in early plantings when germination is slow, as occurs in cool, wet springs, especially if fields are planted soon after a large amount of organic matter has been incorporated into the soil. The adult flies of seedcorn maggot emerge in April or May and search for soils high in organic matter to lay eggs; recently worked soil seems to be favored for egg laying. Injury can be avoided by planting under conditions that promote rapid seed germination and growth. Do not plant for 3 weeks after incorporating organic matter, including cover crops and weeds. Use seed that has been treated with systemic insecticide or use in-furrow drench treatments.

Seed corn maggot injury.

Key Pest #5 – Black Cutworm. This is a sporadic pest across Ohio typically associated with no-till fields or weedy fields containing winter annuals such as chickweed. The weeds attract black cutworm moths as a host to lay their eggs. Once herbicides are applied to control the weeds, the cutworm caterpillars move in search of other plants to feed on. Each caterpillar can cut several seedlings in a row before pupating in the soil. If limp or flagging plants are seen in the field, lightly dig in the area around the wilted plant, especially in the soil cracks nearby to find this pest.

Black cutworm.

Black cutworm.

A list of recommended insecticides for all these pests can be found in the 2020 Midwest Vegetable Production Guide (https://mwveguide.org ).