What’s Chewing on my Sweet Corn?

While walking through a sweet corn plot this morning looking at how many plants were tasseling, I saw a few interesting things to quickly comment on in case growers are seeing these things in their fields.

I saw some rough chewing damage on the leaf and immediately thought, wow, it looks like we have some Fall armyworm in this plot (despite having a FAW pheromone trap nearby that has caught zero moths for weeks). Upon closer inspection, it was a grasshopper inside the rolled up leaf.  As I looked at the grasshopper, I noticed the frass around the leaf damage was not wet and messy typical of the pest but rather thinner, pelletized and fairly cylindrical. So even if the grasshopper had left the leaf, the “frass” would be a good clue it wasn’t a caterpillar.

Leaf damage caused by grasshopper.

As I began inspecting the tassels, I saw a lot of corn leaf aphid on just about each tassel. This sucking pest can be a problem if it exudes too much honey dew (sugary liquid waste excretion) on the tassel and it interferes with pollen shed and possibly pollination. While you can spray insecticides to knock down the aphids, be sure to take a look for natural enemies such as  ladybug adults and larvae, green lacewing larvae, and hover fly larvae.

Corn leaf aphid on tassel and ladybug adult (multi-colored Asian ladybeetle) feeding on aphids.

One of the biggest pests of sweet corn has been a little quiet for the past few months according to our trapping network, but we expect it to pick up in the next few weeks so be sure to have your corn earworm trap out near fresh silking corn with a fresh lure. See the nice summary below by Celeste Welty a few weeks ago with reference to spray frequency of CEW.

The corn earworm moths will be laying their eggs on (fresh) silks of sweet corn. Sweet corn can be protected from corn earworm infestation by insecticide sprays during silking. When the number of CEW moths caught in traps is moderate  (1 to 13 moths per day, or 7 to 90 moths per week), then sprays should be applied every 4 days if the daily maximum temperatures is below 80 degrees F, or every 3 days if the daily maximum temperatures is above 80 degrees F. More information about CEW, traps, and trap-based spray schedules is available using this link: http://u.osu.edu/pestmanagement/crops/swcorn/ .

New Video Resource on Herbicide Drift and Sensitive Crops

Ohio grain farmers are using dicamba and 2,4-D more frequently against herbicide-resistant weeds. These herbicides are stronger and prone to off-target drift. A new video from Ohio State discusses the high cost of drift damage on specialty crops, ranging from lower yields to delayed or lost harvests and even the loss of long-term investments like grape vines or certification status.

2,4-D and dicamba are synthetic auxins, herbicides that affect multiple growth processes by mimicking natural plant hormones. Not all plants are highly sensitive to synthetic auxins, but most will react to exposure in characteristic ways (see photos). Damage is usually characterized by severe distortion of stems and leaves but can also cause delayed or uneven fruit ripening and plant loss.

Good Neighbors: Herbicide Drift Issues and Sensitive Crops
Running time 7:36 minutes
http://go.osu.edu/drift_video

Final Call – Pumpkin Field Day

The 2019 Pumpkin Field Day is designed to help beginning and experienced growers with production and pest management challenges. The field day is scheduled for Aug. 22 from 6-8 PM at the Western Ag Research Station (7721 S. Charleston Pike) in South Charleston. Pre-registration using this link (https://www.surveymonkey.com/r/pumpreg19) is required by Aug. 19th.

Due to our later than normal planting date, not all of the 27 hybrids have fully matured yet. Here is an updated list of what pumpkins/squash in the hybrid trial HAVEmature fruit:

Bayhorse Gold, Hybrid Pam, Carronado Gold, Orange Sunrise, Blanco, Blue Doll, Hermes, Indian Doll, Sanchez, Warty Gnome, Red Warty Thing, Moonshine, 20Kt Gold, Cinnamon Girl, Half Pint, Snowball and Knucklehead.

All of the hybrids have some fruit, and I expect a few more to mature by the field day next week.

Celeste Welty, Jon Branstrator, and myself will be on hand to present information and answer questions as they arise on the two hour tour.

The full details of the field day can be found here:

https://u.osu.edu/vegnetnews/2019/07/25/pumpkin-field-day/

Looking forward to seeing you next week!

Tips for a Successful Zucchini, Squash and Cucumber Harvest

For many backyard growers, community gardeners and urban farmers, growing the cucurbits can be a challenge.  This vegetable (fruit?)  family is affected by a large number of garden insects as well as both bacterial and fungal disease.  There are a few tips and tricks that can be used to make sure some harvest makes it to the table or sales booth in 2019.

First thing to do is mind your pollinators.  Cucurbits are commonly dependent on pollinators as they have separate male and female flowers.  Once the flowers emerge, use of pesticides can damage pollinators and lead to decreased harvest.

 

The male flower is at the bottom right. It is simply a flower at the end of the stem. The female flower of this yellow summer squash is behind the male flower and has an immature fruit at the base.

 

Scouting is a very important part of the Integrated Pest Management strategy.  I had not seen cucumber beetles in large numbers until the July 4th holiday weekend.  Then I started to see them in moderate to large numbers on my summer squash in central Ohio.

 

Adult Striped Cucumber Beetle. This bug will damage leaves, stems, flowers, and fruit while feeding. It also transmits a bacterial wilt that can rapidly cause death in cucurbit plants.

 

 

This is an adult squash vine borer. They lay eggs at the base of the stems and their larvae then tunnel through the stem of the plant disrupting vascular flow and often killing the plant.

These plantings of winter squash, both Waltham Butternut and Buttercup, died over the last weekend in July while the summer squash persisted. Suspects include squash vine borer damage or bacterial wilt from cucumber beetles.

Squash bugs are another common pest of cucurbits that can be present in large numbers in plantings.

Squash bug eggs are laid white, then rapidly change color to bronze. They are commonly found on the underside of cucurbit leaves and should be removed immediately when discovered and discarded away from the plants.

 

This is the juvenile form of squash bugs. They can achieve large numbers fairly rapidly.

 

One great strategy to get a harvest of summer squash is to plant a summer planting now for a fall harvest.  Many of the pests of cucurbits will be transitioning to their over-wintered habitat and become less of a problem in fall.

Responses to Pumpkin/Squash/Melon Grower Stress Survey

On July 5th I posted an article acknowledging the difficult spring and early summer planting conditions most Ohio growers faced, and asked to let us (OSU specialists and Extension educators) know what kind of issues you were experiencing. Once these issues were identified, I began researching possible solutions in order to help growers salvage as much of the season and market as possible. Attached at the end of the article is a PDF with my responses to your questions.

I wanted to thank the 36 growers farming just over 500 acres who took time to respond to the survey. In general, most growers were delayed 2-4 weeks but had a crop in the ground now. The biggest concern besides the ability the control the weather, was that OSU specialists continue to post current information about crop management, pest management, and markets. Several articles along those lines have recently been posted to the VegNet Newletter and we will continue to do so, but if there is a specific topic that has not been addressed, please reach out and contact that specialist directly. Below is a list of OSU specialists and Extension educators with their contact information.

Best of luck to you for better weather this summer and a fair harvest this fall.

Specialist                    Area                            Contact

Doug Doohan              Weeds                        doohan.1@osu.edu

Celeste Welty              Insects                         welty.1@osu.edu

Sally Miller                  Diseases                      miller.769@osu.edu

Jim Jasinski                   IPM/Insects                  jasinski.4@osu.edu

Brad Bergefurd             Horticulture                  bergefurd.1@osu.edu

Matt Kleinhenz             Horticulture                  kleinhenz.1@osu.edu

Steve Culman                Fertility                         culman.2@osu.edu

In case you are not aware, we are having a Pumpkin Field Day on Aug. 22 at the Western Ag Research Station. Read more about it here http://u.osu.edu/vegnetnews/2019/07/25/pumpkin-field-day/

Response to Cucurbit Growers Early to Mid Season

 

July 29, 2019 cdm.ipmpipe.org

Downy mildew was confirmed today in cucumbers in an unsprayed MSU research plot in Benton Harbor, MI. In our experience, when downy mildew is identified in Michigan, it is probably already or soon to be seen in Ohio, and vice versa.  Cucurbit growers should have been applying protectant fungicides such as chlorothalanil or mancozeb , but should now consider transitioning to downy mildew fungicides.  Moderate temperatures, humidity, overcast skies and rain showers expected in much of Ohio in the next few days are conducive to downy mildew spore movement, deposition and infection. MSU’s recommendations for effective fungicides against downy mildew are shown here:

  • Ranman + chlorothalonil or mancozeb
  • Orondis Opti (chlorothalonil is part of the premix)
  • Elumin + chlorothalonil or mancozeb
  • Zampro + chlorothalonil or mancozeb

Alternate products on a 7-10 day schedule.  Follow the label regarding limitations on number and timing of applications.  If you have already applied Orondis Ultra or Orondis Gold for Phytophthora blight management you may have reached the limit on Orondis applications.  Cucurbit crops must be protected from downy mildew in advance – applying fungicides after the disease is well-established is not effective.

Mid-summer insect observations

Corn earworm (CEW) showed a moderate surge of activity during this past week, from 19-22 July when our pheromone trap in Columbus caught 49 moths in a 4-day period. This follows a few weeks of low CEW moth catch, after high CEW moth catch in late June. A pheromone trap near Fremont caught 74 CEW moths this past week. The corn earworm moths will be laying their eggs on silks of sweet corn. Sweet corn can be protected from corn earworm infestation by insecticide sprays during silking. When the number of CEW moths caught in traps is moderate  (1 to 13 moths per day, or 7 to 90 moths per week), then sprays should be applied every 4 days if the daily maximum temperatures is below 80 degrees F, or every 3 days if the daily maximum temperatures is above 80 degrees F. More information about CEW, traps, and trap-based spray schedules is available using this link: http://u.osu.edu/pestmanagement/crops/swcorn/ .

The typical insect pests of mid-summer are currently being found on Ohio farms. Squash bug eggs and young nymphs are being found in squash and pumpkin fields. Cucumber beetles, both striped and spotted, are feeding in flowers of squash and melons. Squash vine borer is past its peak in terms of the number of adult moths caught in pheromone traps, which peaked in early July. The tobacco hornworm is feeding on tomatoes in the field and in high tunnels. Imported cabbageworm is feeding on cabbage and other Brassica crops. Colorado potato beetle adults are on eggplant and potato. Blister beetles are reported on potato. Sap beetles and western corn rootworm beetles are being seen on sweet corn. Japanese beetles are found on sweet corn, asparagus ferns, and various fruit crops, but they seem to be less numerous now than several weeks ago when huge numbers were seen.

The second generation of the European corn borer has not yet been detected, but it should start within the next week or two, and will be important in peppers and sweet corn.

An encouraging note is that many beneficial insects are also active in vegetable crops. Recent sightings include many Orius predatory bugs and the pink lady beetle in sweet corn, lady beetle larvae, lacewing larvae, the spined soldier bug, and damsel bugs in a variety of crops.

-Celeste Welty, Extension Entomologist

Pumpkin Field Day

The 2019 annual Pumpkin Field Day will be held from 6-8 PM on Aug. 22 at the Western Ag Research Station in South Charleston (7721 South Charleston Pike, South Charleston, 45368). This is the 20th anniversary of the field day and no better way to celebrate than to come out and see what kind of research and demonstration trials we have set up this year! We cater to both beginner and experienced growers so prepare to leave with more pumpkin knowledge than when you arrived!
This year we have our standard powdery mildew fungicide trial where we are looking at some new compounds (Trionic, Miravis Prime, Inspire Super). This spring we barely got our mustard cover crop biofumigation research trial planted due to the heavy rains with the goal of reducing Plectosporium infections on the foliage and fruit. We have some strip trials of cover crops and several combinations of plant bio-stimulant products for review. Lastly we have a 27 entry pumpkin and squash hybrid variety trial. Since the rain caused us to plant a few weeks later than normal, it’s likely not all hybrids will have mature fruit by the field day.  A detailed report will be given later as to what hybrids will have mature fruit.
In terms of specialists who be at the meeting, Celeste Welty will be presenting information about insect control. Jon Branstrator is a local grower who will share his experiences (positive and not so positive) with cover crops. Jim Jasinski will host the event and squeeze in a few words about the fungicide trial, mustard biofumigation trial, and bio-stimulants demonstration. As always we hope this field day allows you to mix and meet other growers from around the state.
We ask that you pre-register for the event by Aug. 19th using this link:
https://www.surveymonkey.com/r/pumpreg19
There is a $5 fee per person, and the field day will include some beverages and hand outs. We start registration at 5:30 PM and the tour begins promptly at 6:00 PM. For more information please contact Jim Jasinski, jasinski.4@osu.edu, or 937-462-8016.  Hope to see you out here!

Hardin County Crop Walk

There is a segment of agriculture in southeastern Hardin County that specializes in commercial fruit and vegetable production.  Hardin County is also home to the Scioto Valley Produce Auction near Mt. Victory where much of this produce is sold.  Hardin County OSU Extension has planned a Fruit and Vegetable Crop Walk program on Tuesday, July 23 from 6:00-8:00 pm to help with fruit and vegetable production issues.  The location of the program will be on a produce farm at 17051 Township Road 199, Mt. Victory.  It is open to all fruit and vegetable producers, whether they are commercial or home gardeners.

OSU plant pathologist Dr. Sally Miller will provide information on managing plant diseases with vegetables.  OSU plant pathologist Melanie Ivey will provide information on managing plant diseases with fruits.  Hardin County OSU Extension Educator Mark Badertscher will provide information about Driftwatch.  Driftwatch is a voluntary communication tool that enables crop producers, beekeepers, and pesticide applicators to work together to protect specialty crops and apiaries through use of mapping programs.  It is not a substitute for any state regulatory requirements.

The program will be held outside so bring your lawn chair and umbrella in case of rain.  There will be a diagnostic table so be sure to bring along any weeds, plant nutrition problems, plant diseases, and insect specimens in a sealed plastic bag for questions and answers.  The program will conclude with a walk through a produce patch and high tunnel greenhouse, pointing out fruit and vegetable issues and steps to properly manage them.  There is no cost to attend this event.

Corn earworm arrived early in sweet corn

Corn earworm has showed up unusually early this year and has been infesting early sweet corn that was not adequately protected. The earworm population as detected by moths caught in pheromone traps was very high in early June (161 moths in one trap in one week in Columbus), and again in late June at some sites (125 moths in one trap in one week). However, this past week, the number of moths caught dropped greatly (7 in one trap at Columbus). Similar trends have been reported from other parts of Ohio. As long as corn earworm moths are active, sweet corn fields that are in the early silk stage will become infested by corn earworm unless preventive measures are taken. The infestation will be less intense in sweet corn fields if the local fields of grain corn are in the silking stage, but due to the early summer rains causing delay in planting, grain corn in much of Ohio is not yet at the silking stage, thus sweet corn will be extra vulnerable to earworm attack. Once corn earworm is detected, silking sweet corn should be sprayed with insecticide every 2-6 days. The choice of an appropriate spray interval is as important as the choice of product to use. Details about the most appropriate spray interval based on pheromone traps are shown in the chart below.

Growers who do not yet have a trap can find information about buying a trap with this link: https://cpb-us-w2.wpmucdn.com/u.osu.edu/dist/1/8311/files/2019/07/TrapSpecsAndSources2019.pdf

and information about using the trap with this link:

https://cpb-us-w2.wpmucdn.com/u.osu.edu/dist/1/8311/files/2014/12/CornTrapInstructions2009-u47rp3.pdf

Our testing of insecticides for corn earworm control over the past 13 years has shown that pyrethroids (Warrior, Asana, Pounce, Mustang Maxx, Brigade, Baythroid, Hero) are generally effective for earworm control when the earworm population is low to moderate but generally not effective when the population is high. If pyrethroids are used, they should be used at the maximum labeled rate. Among pyrethroids, Hero is generally the most effective; it is a pre-mix of two different pyrethroids (Mustang Maxx and Brigade). Alternatives to pyrethroids are Coragen, Radiant, and Blackhawk, and the pre-mix Besiege, which was formerly called Voliam Xpress. Organic growers can use Entrust or a B.t. such as Javelin or Dipel.

For plantings of B.t. transgenic hybrids (the Attribute II series and the Seminis Performance series), we have found that the B.t. provides adequate control of corn earworm when populations are low, but not when earworm populations reach high density. These hybrids provide the best control when silks are fresh but less control when silks begin to dry. Thus insecticide sprays during the later part of the silking period are helpful to prevent earworm infestation in transgenic sweet corn.

-Celeste Welty & Jim Jasinski