Wayne County IPM Notes (Week of June 1- June 5)

These observations are from Frank Becker, Dept. of Extension Wayne County.

Vegetable Pests

The Colorado Potato Beetle is being seen feeding in both potato and eggplant. When approaching plants to look for them, be cautious. When the beetle is startled, they drop to the ground and may be difficult to see. They do significant damage to the foliage and can cause significant reduction in yield. The Colorado Potato Beetle also has a history of developing resistance to insecticides being used as control measures. This has limited our choices for treatment options. The best way to prevent further resistance is to avoid using the same insecticide repeatedly. At the current plant stage for potato, the threshold is approximately 1 beetle per plant. For eggplant, it is 25 beetles per 50 plants.

Another pesky insect this time of year is the flea beetle. Their damage may seem insignificant at first, however, their populations can rapidly increase and can quickly overwhelm young plants. Flea beetle damage is occurring primarily on potato, eggplant, cole crops and sweet corn. Sweet corn is of particular concern due to Stewart’s Wilt disease which is vectored by the flea beetle. Susceptible sweet corn varieties have a threshold of 6 beetles per 100 plants, while tolerant varieties have a threshold of 2 beetles per plant. On cole crops, the threshold is 5 or more beetles per plant. For potato, you will need to count the “shot holes” in the leaves caused by the beetle. The threshold is 15 shot holes per leaflet. Eggplants have a threshold of 8 beetles per plant.

In sweet corn, there is light slug damage occurring as well as some light damage being done by the European corn borer larva. Young sweet corn is also a target of black cutworm. The cutworm will cut plants at the soil line. If you find a cut plant, dig up some soil around the plant to see if you can find the cutworm.

Vegetable Diseases

In high humidity this time of year, greenhouse tomato crops become especially susceptible to infection from Botrytis. This can initially present itself on the fruit as “ghost spot” which appear as pale or white rings on the fruit. It can then progress into Botrytis gray mold and the fruit will begin to rot. It is important to increase airflow in the tunnel as well as between plants. It would also be beneficial to reduce the humidity within the tunnel.

Blossom end rot is also prevalent this time of year in crops such squash and tomatoes. Although this is not necessarily a pathogen, secondary infections commonly compound the issue. To manage blossom end rot, it is important to limit moisture stress on a plant, from either too much or not enough moisture. Being consistent in watering and monitoring soil moisture conditions will help to prevent exposing the plant to moisture stress. Proper moisture will also provide conducive conditions for adequate nutrient uptake, given that the nutrients are present at appropriate levels in the soil.

Fruit Pests

Strawberry producers typically are facing several insect pests this time of year. One of these pests is the eastern flower thrips. This small insect feeds on and damages the strawberry blossom. As the berry begins to develop, this damage results in cat-facing on the berry or a russeting/bronzed appearance. When you notice these symptoms on the developing berry, the damage has already been done and there are no treatment options. To look for thrips in the blossoms, take a white piece of paper or a plate and shake the blossoms onto the plate and watch for any small, slender yellow thrips to be moving around. Once you have reached 2 or more thrips per blossom, you should move forward with a treatment. Consider the pollinators before applying an insecticide, considering the target of your application is primarily associated with the blossoms. Preventative sprays can also be used in successive plantings.

Another pest of strawberries and small fruits is the spotted wing Drosophila. The SWD is a small fruit fly that can lay its eggs in ripening fruit while it is still on the plant. As you are picking, do not discard unwanted fruit on the ground right next to the plant. The rotting fruit on the ground will attract SWD. Instead bring a bucket to discard unwanted fruit in and either bury it a foot or so deep in soil or seal the fruit in a clear plastic bag exposed to the sun for about a week to kill any larvae. If culls are discarded in the trash or compost pile, they might attract SWD flies and allow for more generations to be produced. This is also the time to put traps out in your bramble and blueberry patch but if you have June bearing strawberries, they likely won’t be affected by this pest. More details about how to set up traps can be in the  OSU IPM YouTube page under the SWD playlist at https://www.youtube.com/channel/UCzcWaLH3mx7HUKh4OF7bYPA and on Celeste Welty’s https://u.osu.edu/pestmanagement/ page.

Orchard traps are now out in Wayne County and we will be monitoring Codling Moth and Oriental Fruit Moth numbers closely.

Fruit Diseases

Now is the time to be managing early season diseases in apples. Scab, rust and powdery mildew are the three main diseases of concern at this point in the season.

Strawberry leaf diseases may appear unsightly right now, however, now is not the time to be managing these leaf diseases. Once harvest is done and during patch renovation it is recommended that you address these concerns, either with a fungicide or with resistant plant varieties. This is also a critical time to be watching for fruit rots such as Botrytis.

Grapes are currently around the pre-bloom stage. This stage is the most critical stage of development for controlling diseases. Fungicide applications for black rot, powdery mildew and downy mildew are highly recommended during this time.

Leave a Reply

Your email address will not be published. Required fields are marked *