Get Your Goat(heads)

Control Puncturevine Before It Controls You

September 16, 2017


Question:

How can you get rid of those awful, nasty goatheads?? Last year it seems I was able to control them but this year they are so plentiful that I must seek help. HELP!

- J. Melcher, Tularosa

Answer:

You are not the only one with a goathead problem this season. I have received several pleas this month for extra information about these persistent and painful weeds. Stepping on a goathead can be very distressing and provoke the use of colorful language along with prolonged limping.


Once the environmental conditions are just right they ‘grow like gangbusters’ and are very difficult to control. Before you attack, look closely to see what stage of growth the plants are in. If the flowers are not yet formed or are still developing you can stop the life cycle by hoeing and leaving the green leafy part to die a slow, hot death. I recommend you pop them up out of the soil with a hula hoe (also called a scuffle or stirrup hoe). But be careful because, if the flowers have developed into viable seeds, hacking at the base will just help in seed dispersal. Later in the season, when the seeds are already spiny, dig at the center of each specimen and lift the whole, gangly plant carefully into a trash bucket without shaking the seeds all over the place. #thickgloves

For further information I have elicited the help of our NMSU Extension Entomology Specialist and State Entomologist for New Mexico Department of Agriculture, Dr. Carol Sutherland. Here are her insights:

Most New Mexicans are familiar with the woody spined seeds of puncturevines (aka ‘goatheads’) from experiencing holes in bicycle tires, flip-flops or bare feet. These dark green weeds germinate quickly whenever water is available. They rapidly grow into dark green mats that often hide their tiny yellow flowers and the resultant spined seed capsules that resemble the head of a goat with two prominent woody horns. Unfortunately, the plant blooms profusely throughout its lifetime and sets seed accordingly.

The weed is a hazard not only for people and their possessions, but also for animals. Tangled in their fur, hair or wool, the spines can irritate and wound animals’ skins and result in serious infections. The quality and marketability of wool can be reduced when puncturevine seeds contaminate the product. Animals can be injured also by puncturevine seeds in hay or other feed.

Two tiny tan and gray snout beetles are natural enemies of puncturevine: Microlarinus lareynii, a seed feeding weevil, and Microlarinus lypriformis, a stem boring weevil. Both were introduced into the U.S in the 1960s as another tool for managing puncturevine. By their tunneling, the legless larvae of the stem borer are supposed to slow the growth of the mat-forming weed while the similar appearing larvae of the seed weevils burrow through the spiny, woody seed capsules. Both are host specific to puncturevine. In New Mexico, the seed weevils are widely established while the stem borers may not be. Neither will eradicate pesky puncturevines. Weevil populations can vary widely from one year to the next for a variety of reasons.

The best approach to managing puncturevine on a property is prevention, but, if that is not possible, an ‘integrated approach’ involving a variety of practices can reduce weed populations significantly. Hand-pulling, ‘chopping’ or using appropriately labeled herbicides on these weeds as they first appear will prevent those particular plants from adding numerous seeds to the soil seed bank. The seed weevils can assist with seed reduction for puncturevines that escape early treatment. While the weevils are popular with gardeners and can be ordered from several sources, you still have your work cut out for you to keep puncturevines or ‘goatheads’ from quickly taking over your garden or landscape…..or ‘getting your goat.’

Keep the questions coming!


Marisa Y. Thompson, PhD, is the Extension Horticulture Specialist, in the Department of Extension Plant Sciences at the New Mexico State University Los Lunas Agricultural Science Center, email: desertblooms@nmsu.edu, office: 505-865-7340, ext. 113.

Links:

For more information about Puncturevine (Tribulus terrestris).

For more gardening information, visit the NMSU Extension Horticulture page at Desert Blooms.

Send gardening questions to Southwest Yard and Garden - Attn: Dr. Marisa Thompson at desertblooms@nmsu.edu, or at the Desert Blooms Facebook page.

Please copy your County Extension Agent and indicate your county of residence when you submit your question!