MSU Extension Chestnuts

As chestnut harvest wraps up, you will need to prepare orchards for winter. Preventing sunscald and vole damage, winterizing irrigation, planning for any orchard expansions and soil testing can all be taken care of at this time.

Sunscald occurs when large temperature swings take place in the transition between a sunny day and cold night. It occurs on the south or west facing portions of the trunk that receive the most sunlight and occurs when the sun warms the bark of a tree and causes the cells just under the bark to break dormancy. When the sun sets and the temperature rapidly drops, the cells that have broken dormancy are destroyed.

Young trees with thin bark are more susceptible to sunscald but it can occur on mature chestnut trees. Damage from sunscald leaves bark with a sunken appearance where cells have died. The cankers that erupt due to bark death can look similar to chestnut blight and open the tree up to secondary pathogens and long-term issues.

Sunscald can be managed by applying white latex paint from the soil line of the trunk up to the first branches. White paint helps reflect the sun and prevents the tree from overwarming on sunny winter days. Most growers dilute the paint with water to make it easier to apply and cover more trees. Paint should be reapplied regularly as it fades and the tree grows, ideally annually.

Another issue growers face in the winter is vole damage. Voles and rodents in general can be a major problem for chestnut growers. Rodents girdle trees and can directly damage or consume nuts. Burrows and tunnels may also present tripping and falling hazards for agricultural workers. The most common rodent pest species in Michigan include voles, ground squirrels, deer mice and house mice.

Rodent populations expand and contract based on a number of environmental factors and tend to be cyclical. Constantly fluctuating populations can make consistent integrated control programs difficult to maintain, but a regular combination of strategies including monitoring, habitat management and rodenticide application are generally required to achieve reasonable control.

Voles typically only damage small trees (less than 3 years old), so it’s best to apply mouse guards each fall and remove them each spring. Mouse guards provide a physical barrier to prevent damage but must be removed each spring as they can girdle actively growing trees over time. Modifying environmental factors to moderate rodent populations can also be useful. Burning, mowing, using herbicides or planting low growing ground cover to reduce vegetative cover can help make a site less attractive to rodents. Controlling ground cover also exposes rodents to greater risk of raptors, coyotes and other predators. Removing plant cover surrounding an agricultural area may also help in slowing movement of new rodents into a site.

You may also consider encouraging raptor predators through perches or nest boxes. Ideally, adjacent landowners can work together to manage large areas of land to prevent high rodent populations from becoming established.

Using rodenticides is another important component of an integrated rodent control program, but it is not a stand-alone control. Rodents have a relatively short lifespan and a high rate of reproduction, making lethal control strategies effective for a limited amount of time, further enforcing the need for an integrated approach to control. There are a limited number of rodenticides labeled for use in perennial cropping systems in Michigan. Carefully review labels to ensure the site is listed before application. Refer to the Michigan State University Extension article “Rodent control for Michigan fruit, nut and Christmas tree producers” for more information on rodenticides.

Growers with young trees need to consider deer control this winter. Deer can do an enormous amount of damage in a small amount of time. Deer browse dormant chestnut trees, typically stripping the buds and sometimes breaking whole branches off and rubbing tree trunks. This damage can affect the structure of the tree in perpetuity. Deer fencing is the most effective method of eliminating tree damage in the winter and nut feeding in the fall. Unfortunately, fencing may be cost prohibitive and producers might need to consider a multifaceted approach that is more labor intensive but requires less capital. For more information, refer to the MSU Extension bulletin “Deer Barriers, Fencing, Repellents and Dog Restraint Systems.”

As temperature drop, broken pipes from freeze damage and electrical equipment failure can result from poor winter preparation of irrigation equipment. Lyndon Kelley, MSU irrigation educator, recommends spending time now on your irrigation equipment to help avoid irrigation start up repairs and delays next spring. Trickle, drip lines and tape are designed to be self-draining but manifolds and supply systems need attention to make sure no water pockets remain to freeze. Winter rodent damage can turn drip tape and trickle line into junk rapidly. Lines that are to be moved for next year are best stored in the barn. Lines over wintering in the field stand less rodent damage if not covered by plastic, plant material or mulch.

Now is also a good time to inspect each electrical box in the system for damage and holes that may be accessible for rodents. Sealing small holes helps keep rodent damage to a minimum. Snakes and mice have even been known to crawl into electrical boxes and control panels through small hole or underground conduit with unprotected ends resulting in electrical fire and damage. Locking down electrical power supplies helps prevent vandals from turning wells and pivots on midwinter and minimizes potential electrical system damage. Now is an excellent time to inspect grounding, system test resistance and make repairs.

According to George Silva, MSU Extension soils expert, there are several advantages to testing your soil in the fall. First, there is more time available in the fall to collect soil samples and make fertilizer decisions compared to spring. Weather conditions typically are more favorable for collecting soil samples as compared to spring. Michigan’s unpredictable spring weather conditions can force postponement or even abandonment of soil testing for that year. As chestnut sites often require the use of soil acidifying applications of sulfur, fall applications can take advantage of frost heave and snow melt to move sulfur into the soil and affect the pH and nutrient availability before trees begin growing again in the spring.

Based on the soil test results, fertilizer can also be purchased prior to the end of the year. Fertilizer is often cheaper in the fall compared to spring, when demand is high. Purchasing fertilizer prior to the end of this year could also potentially have favorable tax implications. Lastly, soil testing laboratories are busier in the spring compared to fall, as a majority of farmers, gardeners and homeowners wait until spring to soil test. A longer wait for soil testing results may force delays in fertilizer timing.

There are several good quality labs available to Michigan farmers, including the MSU Soil and Plant Nutrient Laboratory. Details on submission, interpretation, fee schedule and more can be found by visiting the website.

Lastly, growers considering an orchard expansion should start planning for and ordering trees at this time. Larger quantities of trees typically require substantial lead time. For more information on orchard design, check out the Orchard Design and Establishment section of the MSU Extension Chestnuts website and the new Chestnut Orchard Design factsheet.

For more information on chestnut production in Michigan, visit the MSU Extension Chestnuts website

This work is supported by the Crop Protection and Pest Management Program 2017-70006-27175 from the USDA National Institute of Food and Agriculture. Any opinions, findings, conclusions or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture.