Monday, July 13, 2009

Weekly Word on Weeds

New Weekly Word on Weeds from Dr. Joe Neal

Lontrel Update – Field Nursery Uses Allowed

Lontrel herbicide (active ingredient: clopyralid) has been labeled for controlling legume and aster weeds in turf and landscape settings for several years. Some of the susceptible weeds include clovers, sicklepod, hemp sesbania, vetch, eclipta, groundsel, horseweed, dogfennel, and thistles. It is generally safe when used as a directed spray around most established woody ornamentals but treatments near plants in the legume family, such as red bud, should be avoided.

The Lontrel label was recently amended to allow for use in nurseries; but, only in FIELD nurseries. Lontrel is very active in low concentrations on susceptible species. So, when using Lontrel, read and follow the instructions and precautions on the label. Some important precautions include:
Do not contaminate irrigation ditches or water used for irrigation

Do not use in greenhouses

Do not make broadcast applications to ornamental plantings; however, spot and directed applications are permissible

Do not allow sprays of this product to contact exposed suckers or roots of susceptible trees or shrubs as injury may occur

Do not collect treated grass clippings for mulch or compost

Do not apply to container grown ornamentals.

What does this mean to nursery crop growers?

Lontrel is another “tool” that field producers may use to control legume and aster weeds. It may be particularly useful in fields with a history of sicklepod, hemp sesbania or glyphosate-tolerant horseweed. Use it as a directed spray around woody crops only. But keep it off of actively growing foliage. I’ve seen significant injury on many broadleaf crops from directed sprays that contacted low hanging limbs (picture field grown hollies here). And, do not use Lontrel around red bud trees; plants can be damaged from root uptake of the herbicide.

Of course, read the label before you use Lontrel. This is a very good herbicide but a little bit of spray drift can cause significant damage to susceptible crops.

For more information contact your local Cooperative Extension Center and ask for the Commercial Horticulture Agent.