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On October 26, 2019

To Practice Orchard Sanitation To Keep Diseases in Check for 2020

Apple scab, Marssonina blotch, fire blight, and fruit rots were problematic for fruit growers during the 2019 season. In light of this Extension Tree Fruit Pathologist Kari Peter advises sanitation will be imperative while preparing for the 2020 season.

For Apple scab and Marssonina blotch leaf removal is key. This was an exceptionally frustrating season for managing apple scab. Rain events were frequent from late April through May, and we recorded very high available ascospore numbers (>10,000 spores) for more than three weeks during this period. If apple scab wasn’t bad enough, some folks were hit with a double whammy later in the season of Marssonina blotch.

If you noticed any scab or Marssonina blotch in your orchard this season, you will want to be proactive in mitigating problems for next year. Orchards are self-infecting when it comes to apple scab and Marssonina. Even if your fruit are clean of apple scab this season, there is still a possibility of leaves being infected. Reducing leaf litter and the spores they contain is an important defense strategy for any good scab and Marssonina management program.

Spores need the leaf tissue to survive the winter. To reduce the available spores for next season, growers are encouraged to employ a two-pronged approach this fall: urea applications and flail mowing the leaf litter. Due to very high inoculum in some orchards this year, urea applications will not be enough; urea applications will be aided by flail mowing to ensure complete breakdown of leaf tissue. 

Time the urea applications as close to leaf drop as possible. Urea works in breaking down the leaves by the extra nitrogen stimulating the growth of beneficial soil microbes after leaves have fallen on the ground. If urea is applied too early in the fall season, it can be washed off before the leaves hit the ground. Using urea will reduce inoculum by 50 to 80% for the next season; flail mowing the leaf litter after the urea application will reduce inoculum by 95%. 

Many growers employ the practice of speeding up the process of defoliating trees in the late fall using copper and nitrogen, or even zinc. Questions about the effect of hardiness have come up. Dr. Jim Schupp (Penn State Pomologist) offers these thoughts:

“The leaves sense shortening daylength and chilling, which triggers the processes that lead to dormancy. Defoliating too soon could remove the organ that senses and triggers dormancy. Also, the tree needs carbohydrate reserves to maintain hardiness throughout the winter. Numerous stories about over-cropped and unharvested trees being winter killed bear this out. It follows that if one defoliates the trees too soon, then reserve carbohydrates and hardiness may be lost. Wait for the first frost before scheduling defoliation. Late harvested cultivars, such as Pink Lady, should be given a couple of weeks after harvest to accumulate carbohydrate before defoliation.”

Dormant pruning will be important for control of Fire blight and fruit rot. when pruning your fruit trees during late fall and winter, be mindful of cankered wood and mummified fruit lurking in the trees. Both serve as an overwintering source for bacteria and fruit rot spores for next season and should be removed as best as possible to limit future infections during the following season. 

When pruning this season, it is best to pay extra attention to those orchard blocks with a known history of fire blight. This may require you to visit orchard blocks more than once, especially during different lighting of the day, to be able to spot cankers that could have been missed during the initial round of pruning. If trees were pruned during the season to remove fire blight strikes, you will most likely see a canker at the site where you pruned. Don’t forget to remove this canker.

When you see a canker, prune 6 – 12 inches from the canker’s visible edge into 2-year-old wood or older since older wood is more resistant to the bacteria. Judgment calls about whether to remove a tree or not will have to be made for smaller trees depending on how severe the infection. Since the bacteria are dormant during the winter, disinfecting pruning tools is not necessary. When it comes to cankered wood, burn the largest limbs that may be too big to be ground up with a mower. Otherwise, leaving the small prunings in the row middles and subsequently brush mowing the debris will be enough.

For cherry leaf spot control, leaf removal is key. Cherry leaf spot and apple scab are very similar when it comes to infection fallen diseased leaves are the culprit for creating spring infections. Like apple scab, sanitation is critical for effective management. Follow the same sanitation method for managing cherry leaf spot as you would for scab.

Peach leaf curl control is needed when the leaves have all fallen. When the leaves have fallen from the trees, the peach leaf curl spores are exposed. This is your only time to manage peach leaf curl. It is important to manage this disease as soon as the leaves have fallen this fall, especially on trees that are early varieties. Spray the trees with a fungicide, such as copper, ziram, lime sulfur, or chlorothalonil. If you are unable to apply your spray this fall, fungicides can be applied during late winter before bud swell and before any drastic warmups during late winter. As a result, you will reduce the chances of getting peach leaf curl in 2020. 

To Learn The Latest On Soybean Production

At several upcoming Soybean Production Workshops, you will have the opportunity to hear about current research on soybean cultural management practices covering the entire growing season, from planting to harvest. Variety selection, planting rates, fertility management, weed, insect and disease scouting as well as harvest management will all be discussed. The events will be held at Fort Littleton December 10, 2019, at Hazleton December 12, 2019, at Port Royale December 17, 2019 and at Montoursville December 19, 2019. All events start at 9 am. To register call 1-877-345-0691 or go to: https://extension.psu.edu/soybean-production .

Quote Of The Week: “Maturity starts with the willingness to give oneself.”  Elisabeth Elliot