To: Waller County, Goatweed Explosion in Bahiagrass Pasture
Howdy! Goatweed is a serious problem for many landowners as the rains have fallen in the spring correctly to germinate a large number of seeds that are already present in the soil weed seed bank. The goatweed in your pictures is one of 21 different Crotons found in the state of Texas and this particular one is commonly named "woolly croton" and "doveweed". Woolly croton is a native, warm season annual that emerges through seed germination in the spring months. One of the associated problems is that you can spray and kill this plant and have it come back from seed after the next rain. Woolly croton seed germinate beginning in March and going through June. What this means is you could broadcast spray a herbicide in late April, kill all current goatweeds and then find them back in the pasture growing in June. Currently herbicide weed control for this plant is looking at chemicals that have soil activity and can act like a pre-emerge herbicide for several months after the initial spraying earlier in the spring.
With that said, our current broadcast spray recommendations to control goatweed in bahiagrass is to spray when the young goatweed plants are 4-6 inches tall and not flowering or setting fruit. At this early growth stage, it is cheaper and calls on less herbicde per acre to control this unwanted plant. For a broadcast spraying you would be treating the pasture where you find the plants have emerged with 10--25 gallons of spray per acre. Because the goatweed is covered with stellate trichome hairs, making it look whitish, you must get good herbicide coverage of the plant leaves to get enough chemical in the plant to kill the root system. The broadcast spray recommendation calls for throughly wetting the foliage but to get the chemical to stay on the plant and not drip off, you must add a surfactant of 1 quart to 2 quarts per 100 gallons of tank mix. Very high control of young woolly croton plants is achieved with a broadcast spray using several herbicides including 2,4-D, Weedmaster, Grazon P+D, Cimarron Max, Surmount, Escort, Clear Pasture and others. The key to successful broadcast spraying is when you spray and that is when the newly emerged plants are 4 to 6 inches tall. It is also best to spray in the spring when good soil moisture conditions exist and active plant growth is taking place so that the chemical will be taken up by the plant.
From your pictures, the goatweed is large, branched, flowering and setting seed. For this year, your pictures show that the opportunity to control goatweed with a broadcast spray herbicide has passed. The goatweed damage is already done (used up the water, shaded the bahiagrass out and used the fertilizer present in the soil). If the goatweed seed have not matured and become adult seed, you could shred the pasture and reduce the amount of goatweed seed present for next years germination and you might even increase fall grass growth by opening the grass covered areas up to more sunlight. If the seed have matured, then mowing would only spread the seed to new and more locations for next year, thus making the problem worse.
The key to controlling goatweed is to spray in the spring when the goatweed plants are 4 to 6 inches tall and ample spring rains have occurred (timing, you have to look at the pasture to see if the goatweed has come up and is growing). If the spring is dry, you might not even have this plant as a problem next year.
Lastly, one of the best ways to fight annual weeds is to not eat all of your grass and leave 3 to 4 inches of residue or uneaten grass standing in the pasture this fall. So many landowners make all of the annual weeds we have a problem because they eat the competitive grass down to the soil surface, giving every weed species a chance to germinate and grow.
You can find the recommendations for controlling goatweed in Texas A&M AgriLife Extension publication No ERM-1466, Chemical Weed and Brush Control Recommendations:Suggestions fo Rangeland. The Waller County Extension Agent should have this publication or direct you on how to get it at the AgriLifeBookstore.org. The herbicide recommendations are shown on pages 9 and 10 of this publication that is also available on-line at ESSMextension.tamu.edu under publications. Look for ERM-1466.
I hope the information above will help you with planning for reducing goatweed in your pasture and with communicating what you see happening in the pasture with your leasee. There are no quick fixes in this case. Thank you for contacting us through the eXtesnion Ask an Expert System.
Barron S. Rector, Extension Range Specialist, College Station, TX