Ask the Steward
By Dan ErnstQUESTION: I have a very large White Oak tree on my farm and heard there is a list of the biggest trees in the state. Where can I get more information?
ANSWER: The Indiana DNR Division of Forestry has been maintaining a Big Tree Register for many years, as do most other states. Champion tree measurement is a fairly simple formula which combines tree height, circumference 4.5 feet above the ground and the average width of the tree’s crown. Add together the tree height in feet, plus the tree circumference in inches. Then measure the average width of the tree’s crown. Divide the width measurement by 4 and add this to the height and circumference measurements for your total score.
The current champion White oak measures 110 feet tall, 313 inches in circumference, and an average crown spread of 138 feet for a total score of 457.5 ([110+313+138]/4 = 457.5).
A few Big Tree facts: the tallest Indiana Big Tree listed is a Bitternut hickory located in Perry County at 154 feet tall. The tree of largest girth is a Bald Cypress in Knox County at 331 inches (that’s a diameter of almost 9 feet). Not all Big Tree champions are huge. For example the largest Paw-paw tree in Indiana is located in St. Joseph County and is just shy of 20” in circumference and 48 feet tall. That’s massive for a Paw-paw, but small compared to the mighty White Oak.
For an application form and detailed listing of Indiana’s Big Trees go to www.in.gov/dnr/forestry/8169.htm
QUESTION: Almost every fall my walnut trees have webs around the ends of some of the branches and leaves, with small worms inside eating the leaves. Is this damaging?
ANSWER: What you have observed is the ‘fall webworm’. This late summer pest is widespread throughout Indiana and their gray silken webs are a sure sign autumn is on the way. The larval (caterpillar) stage of this insect feeds on many species of deciduous trees and shrubs, but Black Walnut is certainly one of the favorites in Indiana. Crabapple and hickory are also commonly affected. Full-grown caterpillars are covered with grayish hairs originating from black and orange warts.
The fall webworm’s tent starts small and by late August is quite conspicuous and fairly large (2-3 feet in length). Unlike Eastern tent caterpillar, the caterpillar stays within the tent eating the leaves and expanding the tent to consume additional leaves as needed.
The damage caused is more cosmetic than injurious to the affected trees. This is especially true for healthy well established trees since relatively few leaves are consumed and the injury occurs primarily after the tree’s main growing season. The affected branches will usually not die and will leaf out again next year.
Controlling the insect in a woodland setting is generally not needed since the damage done is quite small. In an ornamental setting where aesthetics is a concern, the easiest control is to clip off and destroy the affected branches. Or, simply break apart the web and destroy the insect by hand or let natural predators (birds, wasps, etc.) do the work for you. Insect sprays labeled for caterpillars can be used, but should be done while the web is small, typically before mid-August. Since the caterpillar feeds and stays within the web only the web and leaves within the web should be treated. Treating the entire tree is not necessary and should be avoided to protect injury to other beneficial insects and pollinators.
Eventually the mature caterpillars leave the web and overwinter as pupae in the soil or leaf litter. The old gray webs will hang on the trees much of the winter and the cycle begin anew as soils warm and adult moths emerge in mid-June.
Dan Ernst is an Assistant State Forester with the Indiana Division of Forestry. He oversees the state forests in Indiana and has authored the “Ask the Steward” column for years. Have a question for the column? Email Dan at dernst@dnr.in.gov.