Wayne County IPM Notes from September 20-26

Vegetable Pests

Aphids feeding on pumpkin leaves. F. Becker photo.

Cucurbit growers need to check their crops for infestations of aphids. Large populations of aphids can be found feeding on the underside of leaves. While the feeding on the foliage is not of major concern at this point in the growing season, the exudate from the aphids is. Aphids secrete a sticky substance known as honeydew and when large amounts of the honeydew are being formed, it can drip down onto the pumpkins and result in black sooty mold growing on the fruit.

Continue to keep watch over late season cole crops as there are still a lot of imported cabbageworm adult butterflies in and around crops such as broccoli, cabbage, brussels sprouts, and cauliflower. Additionally, other fall insect pests such as the cabbage looper and aphids can become problematic. Aphids can have rampant infestations during cooler and dry weather.  Therefore, routine scouting, especially at this time of year, is important to effective pest detection and management.

Imported cabbageworm larva feeding on cole crop leaves. F. Becker photo.

Fruit and Vegetable Diseases

Residue management of fruit and vegetable crops is an important component of integrated disease management. Typically, at the end of the season, plants are commonly being affected by a range of diseases. As management of these diseases dwindles towards the end of the season, there is an increased level of inoculum that may be able to over winter. Many of the pathogens affecting the plants now are able to over winter and result in disease challenges again next year. It is important to know what diseases you have in your fields. This knowledge can help you make crop management decisions such as how long to rotate out of a certain crop. Additionally, the residue that is left at the end of the season should either be composted or tilled into the soil as soon as possible. Composting or incorporating the crop residue allows for the plant to be broken down by soil microorganisms and prevents the spread of the pathogen to other plants that may be alternative hosts that could overwinter the pathogen. Doing this in association with crop rotation will help give time for the pathogens to die off. Typical crop rotations allow for 3-

A field that has been cleared of plant debris, run through with a disc and then planted with cover crops. F. Becker photo.

4 years between planting a crop in the same family.

Fruit Pests

Stink bugs are still active and can be found along wood-lines and field edges. Although, numbers do seem to be dropping as the summer comes to an end. I am still finding the occasional fruit that has been damaged by a stink bug. The damage is typically occurring in trees along the edges of orchard blocks, especially near wooded areas.

Cucurbit Downy Mildew Spreads to Squash, Pumpkins and Watermelons in Ohio

Downy mildew lesions on pumpkin. Photo by Francesca Rotondo.

We are coming to the end of the cucurbit growing season, and until this week had only seen downy mildew on cucumbers and a few cantaloupes in this state.  However, this Sunday my colleague Francesca Rotondo found a “fresh” infection (it had not been visible a few days before) of downy mildew in our pumpkin research plot at the OARDC in Wooster. Today we confirmed downy mildew in acorn squash and watermelons in our sentinel plot nearby.

At this time of year, the choice to apply downy mildew-active fungicides depends on the progress of the crop. If pumpkins or squash are already mature and foliage is not needed to finish fruit ripening, it is possible to forego fungicide application since downy mildew affects only leaves, not stems and fruit. However, keep in mind that defoliation can lead to sunburn of fruits if we get some hot sunny days. Also note that allowing downy mildew to run rampant through a cucurbit field contributes overall to the inoculum density and puts other cucurbits on the farm or on neighboring farms at risk.

Cucurbit downy mildew fungicide recommendations can be found here.  Phytophthora fruit rot can also be a problem so fungicides that help suppress Phytophthora should be used in fields where this pathogen is or has been present in recent years. Downy mildew fungicides that have activity against Phytophthora are Orondis Opti, Orondis Ultra, Ranman, Elumin and Zampro. The fungicide product ratings for cucurbit diseases can be found on page 130 of the Midwest Vegetable Production Guide.

High Tunnel Site Selection Tips

High tunnel production is important to an increasing number of vegetable farms in Ohio and many are installed in the fall. Installing a high tunnel is a major commitment, beginning with the one made to the soil that will be covered by the tunnel for decades to come (regardless of whether the high tunnel is moveable). The video at the link below summarizes factors to take into account when selecting sites for high tunnels. More input is available on the overall topic and each factor — just ask or look for follow-up publications, programs, and more!

high tunnel site selection primer

Wayne County IPM Notes from September 13-September 19

Vegetable Pests

Large masses of cucumber beetles on pumpkin plants late in the season. F. Becker photo.

Cucumber beetles continue to have high populations in pumpkin fields. The spotted cucumber beetle, which is also the southern corn rootworm adult, are migrating in masses out of corn fields as corn silks dry down and finding their way into pumpkin fields. So long as the beetles are not chewing on the skin of the pumpkin, they are not anything to be concerned about, however, if they start damaging the skin of the fall vine crops, an insecticide application may be warranted.

Scouting your latest plantings of cole crops is recommended to make sure that cabbageworms do not get out of hand. It can be easy to let your guard down as the season winds down, but if you want to have a marketable crop, you need to keep an eye out for the imported cabbageworms doing damage.

Vegetable Diseases

Peppers, at this point in the season should be winding down, however, disease pressure can force a premature end

Anthracnose lesions on a bell pepper. F. Becker photo.

to the season quite rapidly. One disease that can cause a rapid decline in peppers is anthracnose. At this point in the season, it is not worth the investment in any fungicide applications. For future planning, practice a three-year crop rotation with crops that are not in the Solanaceae family and consider doing seed disinfestation before planting. This disease can be managed with fungicides; however, it is important to address the issue of the origin of the diseases, rather than trying to fix the issue by applying a rescue fungicide every year.

At this point in the season, it is of your best interest to consider the cost of any fungicide application in respect to how much more you expect to get out of a crop. With pumpkins, for example, as the plants are beginning to die off at this point in the season, it is not likely that any fungicide application will be effective or result in any increase of yield or crop value. For a crop like cole crops that are just a few weeks in the ground, then you may have opportunity to apply fungicides, should the need arise. As always, follow the label and pay close attention to the pre-harvest interval when applying a fungicide.

Fruit Pests

Stink bugs are still active and can be found along wood-lines and field edges. I am still finding the occasional fruit that has been damaged by a stink bug. The damage is typically occurring in trees along the edges of orchard blocks, especially near wooded areas.

Fruit Diseases

Apples are now ripening and being harvested in orchards around Wayne County. F. Becker photo.

As fruit continues to ripen and be harvested, we continue to move forward through the growing season without many disease issues in our area. If you are doing any final treatments for fruit diseases, pay close attention to the PHI on the product label. The pre-harvest interval determines how long after you applied that product that you may harvest the crop. This is especially important to pay attention to as many varieties of orchard crops as well as grapes are maturing and nearing harvest.

Late Season Pumpkin Pest – Aphids

Jim Jasinski, Department of Extension; Celeste Welty, Department of Entomology

Aphids on lower leaf surface.

While most growers have focused on managing cucumber beetles and squash bugs to this point in the season, now it’s time to be vigilant for a common late season pest, aphids. While there can be several species of aphids that invade pumpkin and squash fields in mid to late summer, the melon aphid is likely most common. Regardless of the species in your field, aphid biology and management are similar.

More aphids on a leaf.

Like squash bugs, aphids have sucking mouth parts. Aphids feed on the underside of leaves where tremendously large populations can build up quickly even with natural enemies (ladybugs, green lacewing larvae, parasitoid wasps, syrphid fly larvae, etc.) in the field, especially under hot and dry conditions. A by-product of their feeding is called honeydew, and when high aphid

populations exist, this sticky liquid can drip onto foliage and fruit creating a perfect condition for black sooty mold to grow on the surface of fruit which will need to be washed off prior to sale.

While aphids can create the environment for sooty mold, they can actively vector viruses to pumpkin and squash plants. A survey conducted in the late 1990’s by OSU researchers concluded that Watermelon Mosaic Virus was the most common type of virus found in Ohio pumpkin fields. Viruses in general may not be a serious threat to older plants where the fruit mature, but for younger plants with immature and developing fruit, distorted and strappy leaves, bumpy mosaic colored fruit or no fruit may result. While it is possible to treat pumpkin and squash plants for aphids, if an aphid feeds on a plant for just a second and then picks up a lethal dose of insecticide, the virus may already be vectored to that plant.  As a practical matter, virus transmission cannot be stopped using insecticides alone. Timing of planting is perhaps more effective, with earlier planting leading to potentially less virus incidence because fewer aphids are present as the crop matures.

Pumpkin leaves infected with virus.

Fruit infected with virus.

Sooty mold on pumpkin rind.

Sooty mold on foliage.

If scouting reveals aphid populations building in a field, even in the presence of natural enemies, treatment may be warranted if honeydew and black sooty mold are seen. While pyrethroids are relatively inexpensive to apply, they are devastating against most natural enemies and will likely cause an even more severe outbreak of aphids soon after application. The following products are non-pyrethroid alternatives, and their relative price compared to pyrethroids ($) are listed. Recent systemic materials such as Beleaf ($$$) and Fulfill ($$$) target sucking pests and should be less disruptive to natural enemies.  Other products such as Assail ($$), Sivanto ($$$), Harvanta ($$$$), and Exirel ($$$$$) are also likely to have high efficacy and less disruptive to non-target pests. A full list of recommended insecticides and their PHI’s can be found in the Midwest Vegetable Growers Guide (https://mwveguide.org).  

Wayne County IPM Notes from August 30 – September 5

Vegetable Pests

Various sizes of stink bug nymphs in the leaf litter of fall vine crops. F. Becker photo.

With daytime high temperatures becoming cooler, we are starting to see more and more activity from the squash bugs. If you are actively harvesting your fall vine crops, the squash bugs may not be of concern to you. However, if you are not yet harvesting or choosing to leave your fall vine crops out in the field, the squash bugs can and will do damage to the skin of the pumpkins and gourds. The best time to scout your fields to look for squash bugs is early in the morning or into the evening when they are not in direct sunlight. More on squash bug management.

Cucumber beetles have made a late season come back, much to the dismay of many fall vine crop growers. The cucumber beetles, this late in the season, tend to do very little damage to the foliage of the plants. What they do go for is the fruit instead. Beetles will damage the skins of pumpkins and gourds. This leaves the pumpkins and gourds as less desirable crops and also opens them up to infection and secondary insect pests that would otherwise not affect the fruit.

Late season damage being done by cucumber beetles. F. Becker photo.

Stink bugs are out and doing damage to crops such as tomatoes. The stink bugs activity and feeding starts to increase most noticeably from late July through August and they remain active through the end of the growing season. Their damage on green tomatoes may appear as small, whiteish areas. On ripe tomatoes, the damage shows up as a golden yellow “starburst” pattern. While this damage is typically only cosmetic, higher amounts of feeding can result in infection and result in the fruit being unmarketable.

Vegetable Diseases

Plectosporium blight on pumpkin can cause significant crop losses. The disease typically presents itself as diamond shaped lesions on the stems and can also affect the veins on the leaves, although it can infect all parts of the plant. The lesions start out small but can quickly cover the entire stem. This disease has started to show up within the last few weeks in Ohio due to the favorable conditions of rain, and cooler temperatures.

Plectosporium blight lesions on a pumpkin stem. F. Becker photo.

A common thing to see in pumpkin fields as plants are maturing is yellowing leaves and the leaves starting to die back. Although there may be diseases such as powdery mildew present in the field, this rapid deterioration is not likely solely the result of the disease pressure and rather the natural senescence of the plant. As the plant matures and the pumpkins and gourds begin to cure, the plant has essentially reached the end of its life cycle. The leaves begin to change from dark green to a pale green/yellowish color and will eventually begin to die back. So long as this is happening at the end of the season and the pumpkins and gourds are mature, there should be no concern.

Fruit Pests

Spotted wing drosophila have been active in small fruits for some time, but with peaches now being harvested, the SWD can and will target the peaches as well. I have found peaches that have SWD larva feeding just under the skin. SWD can also do damage to grapes. I have started to find berries in grape clusters that were soft or looked poorly. Just under the skin of these grapes I found SWD larva feeding and moving around. Many grapes are ripening and getting close to harvest so anyone with grapes should consider treating for SWD.

Stink bugs can also do a lot of damage to fruit crops this time of year. I have set out traps and they are already showing very active stink bug populations. I am also finding damage from stink bugs in orchard crops. Most of the damage I am finding has been occurring in apples. This damage appears as a discolored depression in the skin with corking of the flesh all the way up to the skin. This damage can occur anywhere on the apple, although it can be frequently found on the “shoulder” of the fruit.

Fruit Diseases

Overall, disease pressure has been fairly limited this year. Hot and dry conditions have prevented favorable conditions needed for disease development. As fruit continues to ripen and be harvested, we continue to move forward through the growing season without many disease issues in our area. If you are doing any final treatments for fruit diseases, pay close attention to the PHI on the product label. The pre-harvest interval determines how long after you applied that product that you may harvest the crop. This is especially important to pay attention to as many varieties of orchard crops as well as grapes are maturing and nearing harvest.

Apple that has cracked and split after a heavy rain following drought conditions. F. Becker photo.

After this recent round of heavy rain and subsequent heat and high humidity, apple growers should be aware that some apples may crack or split while still on the tree. We are fortunate that we were beginning to have some more frequent rains that were starting to alleviate drought conditions, and this prevented rapid uptake from the trees. Typically, when a heavy rain occurs after prolonged dry spells or during drought conditions, there is large amounts of moisture taken up through the roots as well as absorbed through the skin of the fruit. This results in rapid cell expansion and thus cracking, and splitting occurs.

Cucurbit Downy Mildew Update

Severe damage to cucumbers by downy mildew. Photo by M. Mechling.

Our lab confirmed downy mildew in cucumbers from Jefferson and Perry counties in eastern and central Ohio this week.  Given the confirmed distribution in Ohio counties and outbreaks in neighboring states, it is safe to assume that cucumbers are at risk of downy mildew throughout Ohio (see map). We have also reported downy mildew on cantaloupes in two of our sentinel plots in northern Ohio, but have not had any confirmed reports on pumpkin, squash, watermelons or other cucurbits in this state. Downy mildew has not been observed on any cucurbits in our sentinel plot on the OSU main campus in Columbus. This tracks with reporting from other states; cucumber is the main cucurbit crop affected so far. More information about downy mildew outbreaks and the interactive map can be found here. Management advice can be found in earlier blogs posts this summer.

Map of cucurbit downy mildew outbreaks by county. cdm.ipmpipe.org

Missed the Virtual Pumpkin Field Day?

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.

Golden Pumpkin “Awarded” at Virtual Field Day    

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 27th. 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.