Planning ahead will increase your trees’ survival from rodent damage

Assessing rodent damage, collecting and preserving scion-wood determines bridge grafting success

Editor’s note: This article is from the archives of the MSU Crop Advisory Team Alerts. Check the label of any pesticide referenced to ensure your use is included.

Cold, long and snowy winters – just like the one we are experiencing – turn our orchards into “all-you-can-eat” hot spots for voles, field mice and rabbits. The trees are a rodent’s next best choice after the deep snow makes grass seeds and fallen fruit inaccessible. It seems that apple orchards become particularly popular, and, as luck would have it, the varieties that bring highest economic return to the growers, like Honeycrisp and Galas, are also favorites on the menu of these little gluttons. If there are no apple or pear orchards around, they will frequent cherry, peach and plum orchards as well. Since stone fruit does not respond successfully to bridge grafting, further discussion in this article refers to apples and pears.

Damage could be very significant and will not only always be confined to the base of the trunk above the soil line. Often, injury extends below the soil surface as well as above the snow line affecting the lower scaffolding. With cambium layer compromised, there is a good chance of losing that tree. The easiest way to kill the tree is to girdle it, but how do you save girdled trees? 

This is where planning ahead can help. It is still a good time to collect scion-wood to be used for bridge grafting. This should be easy now that the crews are still out pruning. One-year-old growth about 3/8 inches in diameter and 15-18 inches long are most desirable. Water sprouts work real well. Naturally, branches should be collected from healthy trees and, preferably, fire blight resistant trees.

The next step is to make sure trees stay dormant and viable until about full pink-early bloom when the actual grafting will take place. The scion-wood must be kept moist and in a cool and dark place. Wood should be wrapped in moist but not soggy paper towels or burlap, placed in a perforated plastic bag (to avoid molding and rotting) and set inside a cooler (temperature above freezing) or refrigerator that is not used for saving food (to avoid any exposure to ethylene). Ethylene will induce bud break, thus compromising graft “take.” Personally, I had best results (98-100 percent took) when using dormant scion-wood.

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