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Winter moth caterpillar on apple tree? #868634

Asked May 15, 2024, 8:15 PM EDT

In our yard in 2021 we planted in full sun three cherry trees and two apple trees. In 2021 and 2022 the young apple trees had some flowers and fruit. In 2023 the apple trees had a lot of flowers but then the late hard frost occurred so no fruit. This year, our honeycrisp apple tree seems to be doing fine with abundant flowers, but our slightly more mature golden delicious apple tree has only 5 flowers. On the golden delicious apple tree, most flower buds have dried up and turned brown. We have about 5 flower buds that actually opened. On most flower buds you can see what looks like a brown hole where a caterpillar entered. Then we noticed the new leaves were curled in and browning and the leaves that did open had holes. The new leaf growth just did not look healthy. Upon closer inspection when opening the curled leaf buds, we found "inchworm" type caterpillars inside. See photos taken today, 5/15 (hopefully you can zoom in to see the tiny caterpillars). Are these winter moth? I've been reading that they are a big problem, but that maybe they haven't been found in Vermont yet. We can capture and save specimens if needed. We can also send in more photos with a professional lens camera if needed.

Windsor County Vermont

Expert Response

Hi Karen,

Thank you for contacting the UVM Master Gardener Helpline with your question. Your photo was excellent and was forwarded to an apple specialist who has identified it as a green pug moth caterpillar. They overwinter as eggs on apple trees and hatch at bud break at which time they enter the buds to feed in the spring. When they feed on buds, it causes the blossoms to abort. One larva can damage several flowers and if abundant, they can defoliate trees which will reduce growth and loss of crop especially on young trees and new grafts. Most larvae finish feeding when the blossom’s petals have fallen and then pupate in folded leaves and emerge as adult moths in June/July. In June/July, the females lay eggs singly near the buds on twigs and will remain dormant until the following spring.

To control, you can either handpick or spray Bacillus thuringiensis (Dipel) or Spinosad which are both organic.


Additional information can be found :

https://netreefruit.org/apples/insects/green-pug-moth-gpm

(note: In the photo, the reddish-brown striped caterpillar is the green pug moth)

https://portal.ct.gov/caes/fact-sheets/entomology/green-pug


I hope this helps,



Melanie,  UVM Extension Master Gardener Volunteer Replied May 17, 2024, 8:49 AM EDT

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