HG Homegrown Column May 09, 2009

How can I get rid of goatheads? They’re all over the place.
— Maria

Goatheads are a tough weed to control, but it can be done.

Goathead is an annual weed, germinating in the spring and dying off before winter but not before setting tons of that devil seed for next year.

The best way to go after them is with a two-pronged approach.

Although it’s too late to help this year, I like using a pre-emergent in late March to kill off some of the seed before it germinates. This often doesn’t get all of them, but it will cut down their numbers so it’s easier to get them all later.

The best pr-eemergent to use is a Hi-Yield product called Turf and Ornamental Weed and Grass Stopper containing Dimension (there’s a mouthful for you).

The plants that do come up should be killed off while they’re young and before they have a chance to flower, set seed and perpetuate the problem.

You can kill off those young seedlings by cultivating the area or by spraying with an herbicide. I like using a Fertilome product called Weed Free Zone. It does a great job on broad-leaved weeds and, unlike some other weed killers, it works well when the weather is cool.

You’ll have to be pretty consistent about doing all this for several years because not all of the seed will germinate that first year. Some is dormant for future years, and you’ll want to be there waiting with the hoe or the spray.

I have several bulbs/bulges on my aspen tree branches this spring. I have cut through one and it looks like an insect is imbedded inside. Do you know what they might be? What can be done?
Thank you.
— Travis

You’re asking a question that many people do this time of year.

People are getting out in the yard, cleaning up and just “reacquainting” themselves with the garden, and they notice these strange rounded swellings on the twigs of their aspen.

They’ve actually been there for about a year, but we notice them now because they’re not hidden by the leaves of the tree.

What you have is a little insect called the poplar twiggall fly.

The adult stage of the insect looks like a tiny miniature housefly. The female has a sharp stinger-like structure (don’t worry, they don’t sting) that cuts a slit in the bark where she deposits an egg or two.

She also secretes a chemical that causes that rounded swelling of the twig called a gall.

The egg is safely enclosed inside where it hatches and the larval stage spends the spring and summer munching on the soft pulpy center of the gall. It spends the winter as a pupa and emerges the next spring to start the cycle all over again.

Though these galls may look a little alarming, they very rarely damage the tree. The insect is only inside for the first year, but the gall will usually continue to grow for several years along with the branch.

Eventually, the gall stops and is “swallowed up” and reabsorbed by the branch as it continues to grow.

There really is no spray for you to use on these guys. Trying to kill the very mobile female fly before she lays eggs is almost impossible.

There’s a bit of research about using systemics to kill the larva, but that’s given hit or miss results. Besides, you may kill the larva inside, but the gall is already there and will continue to grow.

The best way to approach it is to consider it an aesthetic problem and just try to ignore it.

Besides, those leaves will soon be out to hide them.

Dennis Hill is the nursery manager at Bookcliff Gardens, online at http://www.bookcliffgardens.com. Send questions to Bookcliff Gardens, 755 26 Road, Grand Junction 81506; or e-mail .(JavaScript must be enabled to view this email address).


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