Help! How do I get rid of bugs in my ash tree?

We have several clusters of bugs in our ash tree, and I was wondering if you could identify them and let me know what to do about them. The leaves of our ash tree are curled up tightly, almost into a ball, and we find these little white bugs inside. I appreciate any help you can give me. I love this tree and would hate to lose it!

— Robyn

What you have is an insect called ash leaf curl aphid. This little pest is common on varieties of green and white ash in the spring. They cause a tight curling of the new growth and can form clumps of curled up leaves at the tips of the stems.

It’s not a life-threatening problem, but it does make the tree look bad, stunt its growth and make a mess under the tree since these little devils secrete a sticky liquid called honeydew. Because of this, most people act to control it.

The aphid’s numbers tend to decline by late spring or early summer as ash trees stop producing new growth and natural predators and parasites start to gain the upper hand. If the little monsters are still present and actively feeding, you’ll want to treat the tree.

Since these aphids are pretty well-protected within the wads of leaves at the tips of the branches, we like treating with systemic insecticides.

There are three appropriate products available to the homeowner, as far as I know: Acephate, Dinotefuran and Imidacloprid.

Acephate is a liquid concentrate you spray all over the tree. It’s an older product and has shown great results on aphids such as this.

Dinotefuran is strictly a root-absorbed systemic and Imidacloprid comes either way, a root-applied systemic or a liquid spray to cover the foliage.

The root-absorbed systemics are either liquid or granule that is applied around the base of the tree. It’s absorbed by the roots, taken up and distributed throughout the tree and ingested by the aphids when they suck the tree’s sap.

It’s nice because it’s easy to use. You don’t have to spray way up into a big tree and it doesn’t kill any of the beneficial insects that are present. In addition, it lasts in the tree for several months so you don’t have to be doing it all the time.

The drawback to this product is that it’s slow-acting. It can take some weeks to work its way completely through the tree, so you shouldn’t expect immediate results.

The advantage that a spray product has is that it’s relatively fast-acting. Any of the spray that gets on the insect will kill it almost immediately, plus it absorbs quickly into the leaf where the aphid gets a dose when it sucks the sap.

The drawback is that spraying is usually more time and labor intensive and if the tree is large, it’s impractical unless you hire a professional spray company to do it.

Because of the timing of your situation, you probably should plan on spraying the tree since by the time a root-applied systemic gets completely into the tree, the damage will already be done. The root-applied systemics would be an option next year, but you have to put them on earlier (either later on this fall or mid-April next year) in anticipation of the problem.

When is the best time to transplant aspen trees?

— Mike

For most deciduous plants, I like to transplant in early spring, usually March.

However, for aspen I’ve had slightly better success transplanting in the fall.

I’m assuming that you’re digging up a tree in one spot and moving it to another. If you’re talking about planting a tree from a garden center that’s in a pot or balled and burlapped, then any time will work.

Dennis Hill is the nursery manager at Bookcliff Gardens, Send questions to Bookcliff Gardens, 755 26 Road, Grand Junction 81506; or email .(JavaScript must be enabled to view this email address).


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