Month: July 2019

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

Planning and Planting Start Now For Your 2019 Fall Garden Harvest

It is hard to imagine with tomatoes barely starting to ripen that now is the time to start planning and planting for the 2019 fall garden harvest.  The backyard grower, community gardener and urban farmer should plan one season ahead to make sure they maximize harvest in the future.  Right now is the time to think about filling the spots in the garden that will open up after the spring and early summer plants are removed.

The goal is to make sure the garden is planted with no bare soil the entire year,  including winter.  That requires planning. First consider crop rotation.  To do this you need to know your vegetable families.

Take this opportunity to make sure that you keep your ground planted at all times.  There are a number of short term crops that could go into the garden right now that will allow harvest prior to the frost date:

  • Green Beans – can be planted every two weeks for the next month.  Choose rapid bush type varieties.

Beans were planted August 1st. Row cover may be needed overnight for frost protection. Uncover when temperatures warm to facilitate pollination.

  • Peas – Sugar Snaps are 70 days until maturity.  Germination can be tricky with hot, baked clay soils.
  • Summer Squash/Zucchini – plant now or wait until closer to the end of the month in order to miss cucumber beetles for a fall harvest.

Picture taken Mid-October. Notice due to delayed planting their are no cucumber beetles or stink bugs infesting the plants. Planting date was August 1st

  • Swiss Chard – plant now for a fall harvest
  • Green Onions – plant now for a fall harvest
  • Tomato/Pepper – transplants of short season varieties(if you can still find them locally) are possible right now in case the grower has lost plants due to pest damage.  Rotate to another spot in the garden.
  • Lettuce – can be planted from seed or transplant.  May need shade cloth to protect from heat.  Start transplants indoor every two weeks for the next three months for a fall and early winter harvest.
  • Brassicas – start indoor transplants of broccoli, cabbage, cauliflower and Asian greens now to transplant outdoors in late August.

    Start many types of greens indoors now and repeat every two weeks. . Can be transplanted outside later in the season when the weather cools down.

  • Radish – wait until later in the season to direct seed.
  • Beets – can direct seed in the garden now for fall harvest.
  • Carrots – can direct seed in the garden now for fall harvest.
  • Herbs – start more basil now from seed outdoors for a late summer harvest to pair with fresh tomatoes.
  • Cover Crops – keep your garden planted.  Summer cover crops like buckwheat can be planted now, plan on your over wintered space.

Buckwheat is an excellent summer cover crop for developing soil health, suppressing weeds and providing for pollinators.

Think about the spot that you will use for over-wintered spinach production using low tunnels and row cover.

Winter is Coming.

 

Make sure to address fertility.  Did your most recent harvest take out your nutrition?  Address that prior to planting the fall garden.

Making Up Lost Ground (actually, for Lost Plants or Leaves)

Reviewing the condition of various farm fields and research plots prompted me to revisit the process or phenomenon of yield compensation (also mentioned in VegNet June 30). Recently, I saw fields and plots showing missing plants and plants with leaves damaged by insect feeding, mechanical damage, and other causes.

For each crop, there is a plant population shown by research and/or experience to maximize yield potential under specific combinations of variety, planting date, irrigation and fertility program, and other factors. Similarly, yield potential is known to be greatest within target ranges of leaf area index (LAI). LAI is calculated as half the area of all leaves per unit area of ground. It is measured as the leaf area (e.g., square feet) per ground area (square feet) and unit-less. So, a plant, field, farm, or region with a LAI of 3 has enough leaf surface (one-sided) to cover an area three times larger than the area from which the leaves were collected. To calculate LAI, most researchers collect all leaves from above a known area of ground, scan the leaves to calculate their total area, then divide that area by the area from which the leaves were collected. Techniques involving cameras and smartphones are improving the opportunity for obtaining estimates of LAI in the field without removing leaves. Regardless, LAI values have long been used in different ways in agriculture, forestry, climatology, ecology, and other disciplines and industries.

Overall, yield compensation asks if yield will be reduced if plant populations or LAI values are less than the target. The answer is easy for some crops such as fresh market sweet corn; “yes”, since one less plant results in one less ear available for harvest. The answer is more complicated (and encouraging) for other crops able to “compensate” for a reduction in plant population and/or leaf area (LAI) under specific circumstances.

This picture taken at OARDC shows a young butternut squash planting. Based on in-row plant spacing, the image should contain thirty-four plants. However, four plants (12%) are missing outright and four others are noticeably weaker than all remaining ones. So, the absolute percent stand is 88% but, functionally, it may be as low as 76%. Will this planting have a yield equivalent to the yield at 100% of the target population? That is, will the remaining plants compensate for missing ones?

Work completed in 1998 and 1999 by a team of extension specialists in NY and PA gives some clues. Dr. Anu Rangarajan and her collaborators studied defoliation and plant loss effects on butternut squash yield (fruit number, size, and weight) and other variables. Stands ranging from 25 to 100 percent of target populations were created at different stages of growth. Likewise, stands were defoliated to simulate damage due to insect feeding, hail, or other issues. The team summarized its work in the July-September 2003 issue of the journal HortTechnology. Borrowing from that report, the team stated that reducing plant populations or leaf area reduced marketable yield, fruit number, and individual plant productivity (but not fruit carotene content). Damage occurring during fruit enlargement had a greater effect than damage occurring early in the season. Generally, yield was directly proportional to plant population. However, if plant population losses occurred when plants were in the rapid vegetative growth phase, remaining plants responded by increasing fruit number and weight per plant. Still, this compensation did not always provide yields equivalent to the original population. The authors concluded by saying that for growers trying to assess the impact of plant loss or damage, butternut squash compensated for loss of up to 50% of plant population and up to 33% loss of leaves, particularly if loss/damage occurred early in the season.

The take-home message for the planting pictured here and many others? Compensation may save the day. Let’s hope conditions hold steady or improve and that our plantings’ abilities to compensate are not tested further.

Information regarding the article referenced above:
Title: Moderate Defoliation and Plant Population Losses did not Reduce Yield or Quality of Butternut Squash
Authors: Anusuya (Anu) Rangarajan (Cornell Univ.), Betsy A. Ingall (Cornell Univ.), Michael D. Orzolek (Penn State Univ.), and Lewis Otjen (Penn State Univ.).
Source: HortTechnology July-September 2003, 13(3):463-468 (https://journals.ashs.org/horttech/view/journals/horttech/13/3/article-p463.xml)

Look-alikes Spotted but No Cucurbit Downy Mildew in Ohio Yet

Cucurbit downy mildew has been moving up the east coast, with some westward movement in the South, but there have been no reports of downy mildew on cucurbits in Ohio, its surrounding states, or Ontario. Downy mildew pathogen (Pseudoperonospora cubensis) spore trap counts from the Hausbeck Lab at MSU have been very low – and only a few (8) P. cubensis spores were counted from one location on June 28, and none before or since.

We have seen many, many examples of bacterial diseases in vegetable crops this season, a consequence of excessive rainfall this spring and summer. Some bacterial diseases cause leaf spots that can be mistaken for those caused by fungi or oomycete pathogens. Angular leaf spot of cucumber is a prime example: the angular lesions are very similar to those of downy mildew. In downy mildew, the spores of the pathogen may be observed on the lower side of leaves with a good hand lens, but sometimes they are difficult to find. If downy mildew is suspected but can’t be confirmed with a hand lens, it should be confirmed with a lab microscope. Downy mildew spores can be visualized easily with a microscope. If on the other hand the symptoms are caused by bacteria, bacterial streaming from the lesions can be seen using a microscope. This process can be completed in minutes in an experienced lab. Ohio vegetable growers can send or drop off samples for diagnosis to the OSU Vegetable Pathology Lab in Wooster; a fillable PDF sample submission form can be found here.  Samples can also be dropped off at OSU-OARDC Experiment Stations in Celeryville or Fremont, or on the OSU main campus in Columbus (Kottman Hall).

Downy mildew of cucumber

Angular leaf spot of cucumber – a bacterial disease

Applying fungicides is an important tactic in downy mildew management, but spraying them when the disease is caused by a bacterial pathogen is a waste of time and money. Regular scouting, confirmation of symptoms and being alert to reports of outbreaks of downy mildew in the vicinity should be the focus now.

Attention pumpkin, squash, melon, and cucumber growers

We all know this has been one of the most challenging spring and early summer seasons in the past 20-25 years. Ohio State researchers and Extension educators are aware of this and are trying to understand what are your most pressing production needs, so that we can begin to address them as best as possible.
Below is a link with 7 questions that will allow you to report your crop status and any issues you are facing or needing assistance with. We do not ask for your name or farm but we are trying to understand where these issues are occurring, so we do ask for your county; your response is of course optional. All responses are anonymous.
Please take just 2-3 minutes to help us understand your situation, so we can help you in return.  Thank you.