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To Be On The Lookout For Downy Mildew

On July 22, 2017

Downy mildew was found on cucumber plants in the sentinel plot at the Penn State SE Research Center in Manheim (Landisville) on Monday July 17. This disease has been reported on cucumber, cantaloupe and butternut squash in other PA counties. The weather conditions have been ideal for the spread of this disease so it is likely present in other fields and counties in the state. Growers of any vine crop should be including protectant fungicides in their spray programs at this time. Once downy mildew is present on a crop it is all but impossible to eliminate and under ideal conditions can even destroy the field. Ranman continues to be an effective product to include in a control program. Presidio is no longer recommended due to resistance issues.

Growers need to rotate FRAC codes when applying fungicides to vine crops and follow all label recommendations and restrictions. Recommended fungicides can be found in the Mid-Atlantic Commercial Vegetable Production Recommendations guide which can be found online here: http://extension.psu.edu/publications/agrs-028; the guide is also available at some local suppliers and through county Extension offices.  Growers should promptly destroy fields which are no longer being harvested or sprayed in order to help control the spread of downy mildew as well as other disease and insects in vine crops.

To Attend The Vegetable Field Day on July 15

There will be a vegetable field day on Tuesday, July 15 from 9 AM until 3 PM at the Penn State SE Research Center in Manheim (Landisville). The field day enables growers to observe firsthand the various vegetable research projects underway at the research farm – much of it sponsored in part by the Pennsylvania Vegetable Growers Association and the Pennsylvania Vegetable Marketing and Research Program.

Registration will begin at 8:30 a.m. and growers will be able to visit the commercial exhibitors until the program begins at 9:00.  After lunch, the vegetable research tour and discussion will continue until 3:00 p.m.  Growers attending the field day will be eligible for pesticide applicator update training credits. Research projects this season include variety trials of tomatoes, pumpkins, celery and leeks as well as colored bell peppers, cucumbers and tomatoes in high tunnels. Other topic for the day are a fertility comparison demonstration and biological control in a high tunnel.

The registration fee for the program is $30 for adults ($15 for children).  which includes lunch. Registration is through the PA Vgetable Growers’ Association and those interested in the field day should call 717-694-3596<tel:717-694-3596> or email pvga@pvga.org<mailto:pvga@pvga.org> to register.  Walk-in registrations are welcome. The Field Day is a joint effort between the Association and Penn State Extension and Penn State researchers.

To Control Brown Rot In Peaches

Peaches and nectarines are ripening, which means this is the season for brown rot explains Extension Horticulturalist Kari Peter. The fungus causing brown rot is quite opportunistic: it can kill blossoms and it can also ruin the fruit you’ve worked hard all season to grow. Brown rot disease is favored by warm, wet weather conditions. Under optimum temperature conditions, fruit infections can occur with only three hours of wetness when inoculum levels are high. Longer wet periods during infection result in shorter incubation times so symptoms develop more rapidly. It’s not uncommon to have brown rot appear “overnight” on fruit.

Spores produced on early maturing cultivars can fuel a continuing outbreak on late maturing cultivars – this is especially important for those who have battled rot infections already this season. To add another headache to the issue, insects can be important vectors of the fungal spores during fruit ripening: they can carry spores to injury sites produced by oriental fruit moth, Japanese beetle, green June beetle, and other insects that can injure fruit. Wounded fruit are much more susceptible to brown rot than unwounded fruit. It’s critical to be on top of insect management. Another concern to worry about is split pit. Unfortunately, these fruit are quite prone to rot problems. Keep in mind: under the right conditions, “healthy” fruit harvested can be contaminated and may decay later during storage.

Research at Rutgers has shown that timing brown rot sprays 18 days, 9 days, and 1 day before harvest provided greater than 95 percent control under heavy disease pressure. When following this regime, be sure to rotate chemistries by FRAC Group Code number for resistance management.

For example, one could spray the following (provided the maximum number of sprays has not been exceeded for that chemistry). At 18 days: Fontelis (FRAC Group 7; 0 day PHI), at 9 days: Indar (FRAC Group 3; 0 day PHI) and finally at 1 day: Merivon (FRAC Group 7 +11; 0 day PHI)..

Keeping in mind products that were used to control blossom blight, be sure to be in compliance by obtaining the current usage regulations and reading the product label. Depending on the number of sprays needed and what you may have used during bloom time, be sure to practice fungicide resistance management and rotate chemistries by FRAC group (“Spray by the Numbers”).

The key for growers who farm organically or prefer using alternative products is to spray as often as possible as disease conditions persist, manage insects, scout often, and prompt removal of infected fruit as soon as you see it. Spraying often ensures you have continuous protection; removing infected fruit from the trees ensures you are decreasing the amount of spores available to cause disease and hopefully minimizing an epidemic. Knocking infected fruit to the ground will be enough to limit spread. Vigilance is important and this may translate spraying every few days, especially if rain washes off products. According to studies at Rutgers, sulfur is not effective for controlling brown rot. Some organic options labeled for brown rot control are Cueva, Double Nickel, Serenade Opti, and Regalia.

To Control Cherry Leaf Spot With Postharvest Fungicides

Cherry leaf spot is similar to apple scab when it comes to infection conditions: warm and wet. The cherry leaf spot fungus prefers moderately wet conditions (hours of leaf wetness), with temperatures above 60°F. Although folks may be at the end of their tart cherry harvest, disease management is still necessary postharvest. This has been an excellent year for cherry leaf spot and Extension Horticulturalist Kari Peter is already observing too many yellowing leaves in tart cherry orchards in the area. Growers are encouraged to apply two postharvest fungicide applications to prevent cherry leaf spot infection. The goal for the remainder of the season is to keep those leaves on the trees and prevent premature defoliation due to CLS infection. As  Peter always says: tart cherry trees should not be bald in August. This will stress trees setting them up for a weakened condition as they enter the winter months. Many control options are available, such as Bravo, Indar, Merivon, and Syllit (to name a few).

To Control Bacterial Spot On Peaches And Nectarines

Conditions have been favorable lately for bacterial spot on peaches and nectarines and symptoms are afoot in the orchard on susceptible cultivars. Shorter application intervals should be used when rainy periods are frequent and temperatures range from 75°F to 85°F. A longer 14-day interval is acceptable during extended periods of dry weather. Management options include oxytetracycline (MycoShield, FireLine; 21 d PHI) and copper. Coppers vary in their PHI, so use products accordingly when you are nearing harvest. When using copper, remember slow drying conditions and pH of the solution will influence copper injury. In addition: be mindful of what you tank mix with your copper (NO foliar fertilizers and beware of any product that will make the solution more acidic).

Quote Of The Week: “All labor that uplifts humanity has dignity and importance and should be undertaken with painstaking excellence.” Dr. Martin Luther King Jr.