What are Willow Galls?

Willow galls (also known as “willow leaf” or “wilted” galls) are small round spots on the surface of the bark of certain trees. They may appear as white dots, black spots, brownish-red spots, yellowish-brown spots or any other coloration. These spots are caused by the larval stage of the Willow Leaf Sawfly (WLSS). WLSS larvae feed on the sapwood of willows and other conifers. When they reach maturity, they pupate inside the wood and emerge from their pupal case every two years or so. During this time, they lay eggs which hatch into tiny larvae called wolfflars. After hatching, these larvae bore holes through the bark of the tree where they attach themselves to the underside of the bark. The wolfflar then feeds on sapwood until it eventually dies.

When you see a large number of wolfflars attached to your tree trunk, chances are there are many larvae feeding on them. These tiny larvae are about a quarter of an inch long and are white or tan in color. You may also notice a black liquid seeping from the bark.

It is important to avoid disturbing these galls and wash your hands after touching them. The WLSS is not harmful to humans or animals but they can be slightly itchy for people with sensitive skin.

What Do Galls Look Like?

Galls, also known as “wilted galls”, are small round spots on the surface of a tree. They may appear white, black, brownish-red or any other color. Galls are caused by the larvae (caterpillar) stage of the WLSS. The WLSS lays eggs on its host plant, in this case willows and other conifers. The eggs hatch, releasing tiny larvae, also known as wolfflars. The wolfflars then feed on the host plant’s sapwood (the inner part of the stem that carries water and nutrients such as xylem and phloem). When they reach maturity, they pupate inside a protective layer or cocoon within the gall. The willow red gall sawfly emerges every two years or so.

The galls are soft and fleshy when the wolfflars are actively feeding. Once they have fully developed, the galls harden and turn red or yellowish-brown in color. A black liquid seeps from the gall.

This is a defensive chemical that deters predators from eating the larvae.

Wolfflars are very small. They are about a quarter of an inch long and white or tan in color. When you see a large number of wolfflars, chances are there are many larvae feeding on them.

Who Or What Is The Williow Red Gall Sawfly?

The willow red gall sawfly belongs to the family of insects known as the Symphyta. There are about 3,000 species of this type of wasp in North America. They have four main parts to their bodies: the head, the abdomen, the thorax and the legs. Like all other insects, they have three main body sections and six main legs. They also have anywhere from 4 to 6 tiny legs that are not readily visible without a magnifying lens.

The larvae are white or tan in color and grow to about a centimeter in length. The adults are yellowish-tan with dark wings and grow to be about 1.5 centimeters in length.

Their lifespan is extremely short, lasting only a few weeks at most.

The larvae feed on the willow trees in your yard. Each female lays about 100 to 400 eggs underneath the bark of the trees. The eggs hatch into tiny larvae called wolfflars.

What Are Willow Galls: Learn About Galls On Willow Trees - igrowplants.net

The wolfflars feed on the inner layer of the tree known as the sapwood. They are considered a pest and can cause extensive damage to an entire stand of trees over time.

What’s The Best Way To Get Rid Of Sawflies?

The best way to get rid of them is to call a pest control company. When it comes time to pay the bill, you can either pay the company with your credit card or ask them take it out in trade. They will usually take out a subscription to your lawn care or pest control products. This is an easy way for you to save money and help the environment at the same time.

You can also do the work yourself, if you really insist on doing everything yourself.

If you want to get rid of the sawflies yourself, you’ll need to know which trees these destructive insects are feeding on. Gather up a few of the galls and take them with you when you go tree shopping. Visit all of your local nurseries and pick out trees that look like they are resistant to gall formation.

A good example of such a tree is the American Holly. Not only are these trees resistant to gall formation, but they also produce berries that are considered to be quite festive around Christmas time! The holly is a shrub and grows to be about 8 to 12 feet in height, so you’ll have to plant this one a little closer to the house for maximum exposure.

You can also plant other types of evergreens such as the Arborvitae. They’re resistant to gall formation as well and make great wind breaks.

If you really want to stick with the traditional look, you can always plant American Elms. These are unfortunately very susceptible to another type of pest, but we won’t go into that right now. If you insist on planting these, plant them well away from your house.

It’s best to keep an eye on these trees and treat them with an insecticide as soon as you notice any type of infestation.

Whatever type of tree you decide to plant, it should be at least 50 feet away from the house to prevent any problems with pests in the future.

Getting rid of sawflies isn’t the most glamorous job in the world, but it’s necessary if you want to keep your trees healthy and happy. The best way to enjoy your trees is to keep them constantly nourished and cared for. If you find that it’s taking a lot of time and energy to keep up on the feeding, contact an arborist in your area.

These tree experts can help you with things like overgrown roots and even pest control. Remember, it’s better to spend a little money now instead of losing valuable trees.

A few sawflies aren’t going to take down a healthy tree, but you have to make sure that your trees stay healthy. Follow the tips above and you shouldn’t have any major problems with pests or overgrown trees. Remember to contact an arborist if you’re not sure about a problem you’re having, that’s what they’re there for!

Do you have any helpful tips for getting rid of sawflies?

If so, please leave your advice in the comment section below. We’d love to hear your tips!

Sawfly diets consist mainly of the fluids in a plant’s vascular system. They do not eat the wood of trees like many other insects do. They will also eat the leaves, petals, and berries on bushes and other plants.

What Are Willow Galls: Learn About Galls On Willow Trees - igrowplants.net

They will also eat fruit crops if given the opportunity.

These insects are very common and can be found in many different locations. They can be a problem for gardeners and farmers but are usually just a minor annoyance.

There are three types of sawflies: the pine needle, the oak egg, and the willow bell. The pine needle sawfly is green in coloring and prefers to feed on pine needles.

Sources & references used in this article:

Preference–performance relationship in the gall midge Rabdophaga rosaria: insights from a common‐garden experiment with nine willow clones by T Nyman, R Paajanen, S Heiska… – Ecological …, 2011 – Wiley Online Library

The insect galls on willow by SE Hartley – Proceedings of the Royal Society of Edinburgh, Section …, 1992 – cambridge.org

Insects and plant galls by W Hovanitz – Scientific American, 1959 – JSTOR


Dodder overwintering as haustorial tissues within Cuscuta-induced galls by HL Dean – Proceedings of the Iowa Academy of Science, 1955 – scholarworks.uni.edu



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