Downy Mildew Reported on Cantaloupe and Acorn Squash in Ohio

As of Monday, most reports of downy mildew in our neighboring states – MI, KY, PA – were in cucumbers, as were our previous reports. However, we found downy mildew on acorn squash in our sentinel plot on the OSU North Central Agricultural Experiment Station in Sandusky County and on cantaloupe in our sentinel plot on the OSU Muck Crops Experiment Station in Huron County. While we have not had reports from most Ohio counties, it is likely that downy mildew is widespread in Ohio. Now we have evidence that the strain that infects most cucurbits, including squash and pumpkins, is present here. The cucurbit growing season is winding down, but if cucurbit crops are expected to be in the field in the next few weeks they should be protected with fungicides.  See my blog post on August 22 below for fungicide recommendations.

The downy mildew pathogen does not infect cucurbit fruits but if plants are defoliated the fruits are at risk of sunburn. Sunburn may not be obvious immediately in the field but may develop in storage. In fields with significant defoliation, pumpkins and winter squash should be removed from the field and into shade for curing.

Finally, the downy mildew pathogen does not survive over the winter in the absence of living cucurbit plants. However once harvesting is completed, plants should be disked as soon as possible to kill remaining green tissues that may otherwise be infected and serve as sources of inoculum. This will reduce downy mildew inoculum that can spread to cucurbit crops near and far.

Good and Bad Birds on the Farm

Do you have a bird problem on your farm?  Do you want to encourage beneficial birds as an IPM tool? If so, consider attending this free webinar.  Registration information below:

Webinar: Supporting Beneficial Birds and Managing Pest Birds

Supporting Beneficial Birds and Managing Pest Birds

Webinar: Tuesday, October 1 at 11AM Pacific, 12PM Mountain, 1PM Central, 2PM Eastern Time

Register in advance at https://oregonstate.zoom.us/webinar/register/WN_Yey2HdAZQ8S3CSKUuR8FIg

Join eOrganic for the first webinar of our fall season! The topic is Supporting Beneficial Birds and Managing Pest Birds, by Jo Ann Baumgartner of the Wild Farm Alliance, Sara Kross of Columbia University, and Sacha Heath of the Living Earth Collaborative.

Beneficial birds can help farmers keep pest insects, rodents, and pest birds at bay. They act the same way that beneficial insects do in helping with pest control. The overwhelming majority of songbirds are beneficial during nesting season because they feed pest insects to their voracious nestlings. Farmers may be able to reduce their pest-control costs by providing habitat for these beneficial birds and by only targeting detrimental birds at the right time and place. Wild Farm Alliance and two avian ecologists will present on: a) How birds’ diets, foraging strategies, and nesting periods affect the farm, b) How best to manage and co-exist with pest birds, c) Why on-farm habitat and the surrounding landscape influences pest control, and, d) What farmers can do to make farms more bird-friendly and resilient. With this webinar and the associated Supporting Beneficial Birds and Managing Pest Birds booklet, we aim to help all farmers and farm consultants make the most of birds on farms.

Pumpkins: Time to Pass the SPF 45

About 10 days ago we harvested a few pumpkin trials at the research station. After weighing and grading the fruit, they were set back in the row but not in the leaf canopy. Last week I drove by some of the plots and noticed some fruit were sunburned. Such is the fate of many pumpkin fruit exposed to direct sun and not covered by leaf canopy. Sunburned fruit have a reddish area facing the sun which will eventually soften and rot.

Reddish area on near fruit, sunburn.

Over the year’s growers have asked me, how long into the season should they treat the foliage with fungicides? I would respond as long as you plan to harvest fruit. Avoiding sunburned fruit is the primary reason to keep the foliage healthy later into the season. Given our increasingly warmer and sunnier fall season, growers should expect to incur significant losses if the foliage is degraded by bacterial or fungal pathogens.

Conditions that favor sunburn include thin leaf canopies, fruit that have been clipped off of the vine but left in the field to cure or be packed at a later date, and clear sunny days with highs above 80-85F.  The weather forecast for the next week in southwest Ohio include max temperatures in the mid 80’s to low 90’s…let’s hope periodic cloud cover spares growers from excessive fruit losses.

Corn earworm remains abundant!

As detailed in VegNet on 24 August, we have seen very high numbers of corn earworm moths caught in pheromone traps since mid-August. Trap catch remained very high last week at most Ohio sites where we have traps. This pest prefers to lay its eggs on fresh-silking sweet corn but also can cause significant damage to tomatoes and bell peppers.

Our Ohio trap reports for corn earworm and several other vegetable pests are posted online, at this link: https://docs.google.com/spreadsheets/d/10gh3rHahdxLKkXQapGyEPxWsjHYRmgsezOoFHnwtyEo/edit?usp=sharing

One of the details shown on our trap report page is the type of trap. At most of our sites, we are using the type of trap called a Scentry Heliothis trap, which is a large cone-shaped trap made of white nylon mesh. At two of our sites, South Charleston and Columbus, we have the type of trap called a Hartstack or Texas Cone trap, which is the same shape but larger and made of metal hardware cloth. The Hartstack trap tends to catch much higher numbers of corn earworm moths, and tends to detect low density populations of corn earworm more effectively than the Scentry Heliothis trap. The Hartstack trap is not readily available from trap supply companies, thus we recommend the Scentry Heliothis trap to our cooperators. However for anyone who is interested in Hartstack traps, here are two tips. The plans for making your own Hartstack trap are shown in a fact sheet from Kentucky: https://entomology.ca.uky.edu/ef010 . We purchased our Hartstacks several years ago from a source in Illinois (see http://www.agrinews-pubs.com/news/building-a-better-bug-trap/article_c69e27e7-fa1e-58b5-b5f7-442112bfb2a0.html )

-Celeste Welty, Extension Entomologist

Increasing activity in corn earworm (tomato fruitworm)

Mid- to late-August is the time of year when we usually see a large increase in the populations of corn earworm, the pest that is also called the tomato fruitworm. As of last week, this trend has been seen in some parts of Ohio but not in others, which is unusual; we usually see an increase at all sites at this time of year. Our pheromone trap in Clark County jumped to 555 moths last week, up from 36 moths the previous week. Our pheromone trap in Franklin County showed an increase to 43 moths last week, up from 12 moths the previous week. The current moth population is likely composed of some recently immigrating moths from the southern USA as well as moths that emerged locally as the later generation of moths that migrated into Ohio back in early June.

Trap reports for corn earworm at several Ohio locations can be viewed using this link:  https://docs.google.com/spreadsheets/d/10gh3rHahdxLKkXQapGyEPxWsjHYRmgsezOoFHnwtyEo/edit?usp=sharing

Fresh-silking corn is the preferred host of the corn earworm, but tomato is another common host. It can also attack a variety of other crops, including bell peppers, lettuce, beans, potatoes, cole crops, cucurbit crops, as well as many weed species.

Infestation of the tomato fruitworm on tomatoes in Ohio is most likely in late August and September, but can sometimes occur much earlier, as has been seen this year. It prefers green tomatoes over ripening red tomatoes. Larvae often feed on one tomato fruit for a short time then move to another fruit. Damage in fruit appears as deep wet cavities. Eggs are usually laid on a leaf below the highest flower cluster.

Each female moth of corn earworm can lay 500 to 3000 eggs. Eggs usually hatch in 3-4 days but can be faster when weather is very hot. As the larvae feed, they progress through six instars or sub-stages, with each instar lasting 2-3 days. The larval stage lasts about 15 days at 86 degrees F. Once larvae are fully grown, they drop to the ground, where they tunnel 2-4 inches deep to pupate. The pupal stage lasts about 13 days. New moths start to lay eggs about 3 days after emerging from the pupal stage. The moths are active mostly at night, and hide in vegetation during the day. The moths feed on nectar in flowers of various trees and shrubs and weeds. The moths usually have a 5-15 day lifespan, but can live up to 30 days.

When corn is in the fresh-silk stage, it is attractive to corn earworm. During the time that Ohio’s large acreage of field corn is silking, our relatively small acreage of sweet corn and tomatoes is usually not attacked much by this pest. Once the field corn in any area begins to mature and dry, it is no longer as attractive to the earworms as late sweet corn and tomatoes. This year, much of Ohio’s field corn was planted later than normal due to frequent rains, so this protective effect of nearby silking corn has been happening later than usual this year but is now likely ending in most locations.

One of the most effective ways to monitor this pest is to use a pheromone trap to catch adult moths. As soon as the target moth is found in traps, fields of sweet corn and tomatoes and bell peppers should be scouted for signs of larval damage so that control measures can be taken in a timely and preventive manner.

In addition to the challenge of knowing when the corn earworm arrives, another challenge is its susceptibility to insecticides and transgenic crops. Observations over the past 12 years in the Midwest have shown that pyrethroid insecticides (Warrior, Brigade, and others) are not as effective at controlling corn earworm on sweet corn as they were previously. In years when the corn earworm population density is low, we have seen that pyrethroids can provide very good control, but in years when their density is high, pyrethroids are not very effective. Alternatives to pyrethroids for sweet corn are Coragen, Radiant, Blackhawk, Lannate, and Sevin. Alternatives to pyrethroids for tomato are Avaunt, Coragen, Exirel, Intrepid, Lannate, Radiant, Rimon, and Sevin. Among the transgenic sweet corn hybrids, we are seeing that the old Attribute hybrids are no longer very effective for caterpillar control, but the Attribute-II hybrids are very effective. Some growers are reporting that some of the Performance Series hybrids are not providing adequate control. We have a field trial in progress to determine how well the transgenic hybrids are currently working under Ohio conditions.

-by Celeste Welty, Extension Entomologist

Harvests of Data Hopefully Increase Harvests of Money

Experiments planned in Fall-Winter 2018-2019 and initiated this spring at the OARDC in Wooster, OH are now yielding crop-based data. Additional experiments initiated this past week or to be initiated within several weeks will provide additional numbers of potential value to growers. Overall, these experiments are supported by: (a) the USDA-NIFA Specialty Crop Research Initiative (https://nifa.usda.gov/program/specialty-crop-research-initiative-scri), (b) the USDA-NIFA Organic Transitions Program (https://nifa.usda.gov/program/organic-agriculture-program), (c) the USDA-NIFA Potato Breeding Research support program (https://nifa.usda.gov/funding-opportunity/potato-breeding-research), (d) North-central SARE (https://www.northcentralsare.org/), and (e) companies. Along with our collaborators, through these experiments, we look to provide growers and other members of the industry with information they can use beginning immediately, especially when making decisions involving the use of grafted plants, microbe-containing crop biostimulants, reduced-tillage approaches, high tunnels, and/or new potato varieties. Ideally, this information will increase the yield of money on Ohio farms.

Two ongoing experiments will help identify the optimal growing practices when grafted watermelon plants are used. Grafted watermelon plants are showing high potential in- and outside Ohio. However, their wider use has been slowed by their higher cost and the fact that yields from them are not always higher than from standard ungrafted plants. Importantly, an increasing amount of evidence provided by researchers and farmers suggests that growing practices may have to be altered in order to get the best return on investment from grafted watermelon plants. Studies and farmer experience point to changes in plant density, and/or nutrient and/or irrigation management as possibly beneficial. This is reasonable given characteristics of some watermelon rootstocks. So, since 2018, like others, we have been asking if yield can be maintained or increased even as grafted plant density or fertilizer inputs are modified. These two experiments total twelve variety-fertility program and eight variety-plant density treatments. On 8/21/19, the VPSL and OARDC Farm Crew harvested 849 “Jade Star” watermelon fruit from the forty plots spanning roughly 0.7 acre (including pollenizer plants). The 849 fruit totaled 6.2 tons (11 over-filled pallet boxes) and averaged 255 lbs/plot (nine plants). “Fascination” fruit will be taken from the same experiments the week of 8/26, fruit quality will be evaluated in the lab, and the harvest-evaluation process will be repeated for the same experiments to capture total crop yield potential. At the same time, we will continue to focus on: (a) tomato experiments testing grafting, strip-tillage, and/or microbial inoculant effects on fruit yield and quality; (b) butternut squash, carrot (fall high tunnel), and spinach (fall high tunnel) experiments testing microbial inoculant effects on yield and quality; and (c) potato experiments completed in cooperation with breeders at USDA, the University of Maine, Cornell University, and North Carolina State University.

Cucumber Downy Mildew Confirmed in Northeast Ohio

cdmipmpipe.org, August 22, 2019

Following reports this week of downy mildew on cucurbits in Michigan, central Pennsylvania, Wisconsin and Indiana, we have our first confirmed report of downy mildew on cucumbers in northern Wayne County. This is very late for this area – we usually see downy mildew on cucumbers in early July in northern OH. Many growers have been spraying preventatively due to the seriousness of downy mildew on cucumbers and other cucurbits. All of the reports this week from MI, WI and PA were from cucumber, although the report from southwestern Indiana was from watermelon.

Cucurbit growers who have not transitioned from applying only protectant fungicides such as chlorothalanil or mancozeb to downy mildew fungicides should now do so.  The environmental conditions – cooler temperatures, high humidity, overcast skies and rain showers- expected in much of Ohio during this part of the season are conducive to downy mildew. Effective fungicides against downy mildew are Ranman, Elumin, Orondis Opti and Zampro.  Tank mix these with chlorothalanil or mancozeb, with the exception of Orondis Opti, which includes chlorothalanil inn the pre-mix.

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 and yield losses are likely.

Spider mite management

With hot and dry weather persisting over much of Ohio, there are reports of spider mite outbreaks on specialty crops. Because mites are tiny, they are often overlooked or misdiagnosed as a disease. Infested leaves have fine webbing on the leaf undersides. Tomato leaves damaged by spider mites usually have yellow blotches, while bean leaves show white stipples or pin-prick markings from mite feeding. Pumpkins can tolerate moderate levels of mites, but watermelons are more sensitive to injury from mite feeding. A simple method of diagnosing spider mites is to shake leaves over a piece of paper and look for moving specks that are visible to the naked eye. A closer look with a magnifier can show the tiny mites that are white, marked with two large dark spots on the middle of the body.

Mites have many natural enemies that kill them, such as specialized predatory mites or generalist lacewings, ladybugs, and pirate bugs, but these helpful predators are often killed by pesticides. Mites can be suppressed by periodic overhead irrigation.

Chemical intervention can be needed to keep the crop alive if spider mites are abundant. In some fields, the mite infestation is worst on a field edge by a dusty road. When a mite infestation is limited to field edges, infested fields should be scouted, and a miticide applied as a spot treatment to isolated infestations. Mite control is better when higher volumes of water are used; 25 to 50 gallons of water per acre is better than 10 gal/A.

Several pesticides are registered for spider mite control; some are restricted use, and some are for general use, as shown for vegetable crops in Table 1, and for hops and fruit crops in Table 2. At some locations, organophosphates are still effective for mite control, with Dimethoate being the best bet and MSR (Metasystox-R) as another choice. Dimethoate is an option for melons but is not allowed on squash or cucumbers; it has been a preferred product for mite control on soybeans. Dimethoate is prohibited from use on ornamental crops in high tunnels and greenhouses but is not prohibited from vegetable crops in high tunnels and greenhouses. Where organophosphates are not effective, Agri-Mek (abamectin) is generally the most effective product for mite control but it is a restricted-use product, while Acramite (bifenazate) and Oberon (spiromesifen) are nearly as good but are not restricted-use products. Other options for some crops are Portal, Envidor, Zeal, Nealta, Onager, Savey, Apollo, and Kanemite. Although Brigade (bifenthrin) and Danitol (fenpropathrin) are labeled for spider mite control when used at the high end of the rate range, they are generally not as effective as the true miticides. Dicofol is an old miticide that is still effective at some sites, but does not perform well at sites where resistant populations have developed. Vydate (oxamyl) is a Restricted Use product that is registered for use on eggplant for mite control. On organic farms, insecticidal soap (such as M-Pede or Des-X) can be used for mite control, but thorough coverage of the undersides of leaves is needed for good control. Soap can cause phytotoxicity if applied under sunny hot conditions. Soap is a good alternative in conventional fields that are too close to harvest to use a true miticide; insecticidal soap has a 12-hour re-entry interval and a 0-day pre-harvest interval.

-Celeste Welty, Extension Entomologist

Lab to Field to Basket: Potato Research and Extension to Strengthen the “Chip Business”

Pounds upon pounds upon pounds of potato chips are consumed each day. Few give the hard work on the farm or science and teamwork required to bring good chips to market one thought. Here, though, is a brief summary of recent activity in Ohio and elsewhere designed to help growers and processors and all others who rely directly and indirectly on local-regional “chip business.”

The Big Picture. USDA (e.g., https://www.nass.usda.gov/Publications/Todays_Reports/reports/pots0918.pdf) and other information makes clear that potato production and processing remain important, enormously valuable industries throughout the U.S., Great Lakes, and, still, Ohio. Nearby on the ground evidence includes Lennard Agriculture (https://www.lennardag.com/) and impressive investments it and its cooperators have made in infrastructure (e.g., center pivot irrigation systems), expertise, research, and other assets in a four-county area of the Scioto River Valley, among other locations. Early, summertime harvests of large, high-quality crops suitable for use in chip-making are important to them. This activity maintains the strong tradition of supplying local-regional chipmakers … page 20 of the USDA report mentioned earlier shows that the U.S. contains approximately 89 chip-making plants with 15 (16% of the total) located within Michigan, Ohio, and West Virginia. Thankfully in this case, it appears that little has changed since 2008 (https://www.potatopro.com/news/2008/ohio-boasts-second-most-potato-chip-manufacturers-us) and before.

Potatoes used to make chips must meet strict specifications. Tuber shape, size, specific gravity, sugar/starch content, flesh color, natural or man-made damage, and other characteristics influence the chip-maker’s desire for the crop. Since these traits hinge on each combination of potato variety, crop management, and growing conditions, the pressure is on growers to optimize each combination. Improved varieties better able to thrive in various conditions are always needed. With important exceptions, potato varieties used in chip-making in the U.S are bred by teams at USDA and a small number of universities, including Michigan State Univ. (http://potatobg.css.msu.edu/). In 2019, led by Chris Long of MSUE (https://www.canr.msu.edu/people/christopher_long), plots of a total of fifteen experimental selections from MSU, USDA, Cornell Univ., and North Carolina State Univ. were planted alongside ones of “check” varieties in fields in Ohio coordinated by Lennard Agriculture. During Aug 13-16, the OSUE team including Chris Bruynis and Ross Meeker (https://ross.osu.edu/about/staff), Brad Bergefurd (https://scioto.osu.edu/about/staff), Mike Estadt (https://pickaway.osu.edu/about/staff), Will Hamman (https://pike.osu.edu/about/staff), and the VPSL (http://u.osu.edu/vegprolab/) harvested the plots and collected key data on the tubers. The VPSL has a long history of cooperating with potato breeders and others in developing improved varieties (e.g., see reports at http://u.osu.edu/vegprolab/technical-reports/).

Yield was measured first and it ranged from 1.3 to 2.6 pounds per foot of row across all selections and varieties (these values equate to 226 and 452 hundred-weight/acre, resp.). Tuber specific gravity (S.G.) using the weight in air, weight in water method and a hygrometer was measured next (see URL above). This method involves placing exactly eight pounds of tubers (air, at left) into a basket attached to an air-filled bulb and calibrated meter. The basket-bulb-meter unit is then placed in water (middle and right). It will sink to a depth roughly consistent with the tubers’ combined moisture and dry matter (especially sugar/starch) levels. Tubers high in S.G. are needed in chip-making; S.G. is influenced by variety, management (especially nutrient and irrigation), and other environmental factors. The S.G. of experimental selections … lines still being tested and not yet named … is always benchmarked against the specific gravity of well-known standard varieties.

Next, tubers were peeled and placed in cold water until chipped. Tuber flesh that has been damaged and exposed to air typically begins to oxidize and brown. Submersion in cold water slows the process. Commercial chip-makers and other potato processors remove potato skin using various methods often involving pressure and/or steam.

In commercial chip-making, peeled tubers are then sliced to product-specific thicknesses. Chip enthusiasts know that products vary in chip thickness, a variable that has multiple significant implications for the chip-maker and for research teams working on their behalf. Slice thickness influences fry time, oil-absorption, chip texture, and many other variables which influence the suitability of a variety for the specific product. As in our other potato research, here, we produced slices measuring 0.051 inches thick using a DeBuyer Kobra mandolin slicer.

Slices were then fried for 3.5 minutes using oil provided by a local chip-maker (Shearer’s Foods, Inc.) and a standard tabletop fryer (left). The target oil temperature was 350 deg F and the actual oil temperature was monitored throughout and allowed to reach the target between batches. Finally, the color of completed batches was scored against the industry-wide standard Color Chart developed by the Snack Food Association of America (sfa.org; below right). A rating of 1 (upper left of chart) is desired by most chip-makers. Many batches completed on 8/16/19 using tubers harvested in the Scioto River Valley area scored 1-3, a very promising result. Remaining tubers have been placed in cold storage and will be chipped again later, as one assessment of the rate at which each genotype converts starch to sugar when exposed to storage-like temperatures.

Land. Equipment. Good varieties and growing methods. Proper inputs. And, crop-friendly weather. These are just some of the resources needed for success on the farm. However, a great team is also essential … just as in research, extension, and other activities. In 2019, for the VPSL, like for other teams, data collection is ongoing. The potato evaluation outlined here will be followed by work with tomato, squash, watermelon, carrot, and other crops, with plots in fields and high tunnels and at OARDC and on commercial farms.

 

 

 

 

 

 

 

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/ .