The tools to control mesquite have improved, but timing of application still plays a key role in success.
Pay attention to five critical factors, advise the Range & Pasture experts with Corteva Agriscience™. Some of these factors also apply to hand-sprayed leaf treatments. These recommendations are based on the work of researchers with the Texas A&M University System and Texas Tech University, plus more than 30 years of commercial experience.
Soil temperature 12 to 18 inches deep should be at least 75 F and, preferably, more than 80° F. Do not spray when soil temperatures are cooler than 75° F. Soil temperature is critical, because it influences the flow of carbohydrates and absorbed herbicides in the plant.
Make your broadcast applications within 60 days after reaching the minimum soil temperature. Clay soils, wet soils and heavily shaded soils will warm up more slowly than others. Rainfall during the season will cause soil temperatures to drop.
Herbicides absorbed by the leaves must move down into the roots and the below-ground bud zone to root-kill mesquite. Absorbed herbicides flow with the carbohydrates. In mesquite, carbohydrates move downward during two periods, the optimum times to spray.
The first optimum period is 42 to 63 days after bud break. In many areas, this will be the last week of May through the first two weeks of June. Spray during this period only if the mesquite flowers are yellow in color, the leaves are dark green and soil temperatures are above 75° F. Low soil temperatures often limit spraying in this period.
The second optimum timing is 72 to 84 days after bud break, when mesquite beans are fully elongated and maturing. In many areas, this second timing will be during the first two weeks of July, but this is dependent on the year and may shift due to rainfall patterns.
Mesquite foliage should be healthy and dark green. Damaged or immature foliage won’t absorb enough herbicide. Avoid spraying if insects, hail or disease have damaged more than 25% of the foliage. Don’t spray if there are new, light green leaves on the twig tips.
While it may seem like a drought to you, mesquite can be healthy, growing and ready to spray even if the soil is dry. Rainfall can actually be bad for mesquite control. Rains after a dry period can cause new leaf growth on twig tips, indicating upward translocation. Don’t spray then.
Too much dry weather can also be bad, if it affects mesquite foliage. Don’t spray if foliage is obviously stressed by drought — i.e., very sparse foliage on the mesquite, leaves turning yellow, leaf margins and tips necrotic, or leaves dropping. Spraying when grasses are dry or “drought dormant” is OK if the mesquite foliage is healthy.
Proper application is key. Recommended herbicides and rates will vary by region, associated species and management goals. In aerial trials, Sendero® herbicide, either alone or in tank mixes at 28 ounces per acre, has proven to be the most effective and consistent herbicide treatment on mesquite.
For aerial applications, wind speed should be 2 to 10 mph, or 5 to 10 mph in heavy mesquite cover. Air temperature should be less than 95° F. Relative humidity should be more than 20%.
In aerial applications, use at least 4 gallons total volume of spray mix per acre. Aircraft should spray swaths perpendicular to the prevailing wind direction.
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