We have had incredible rainfall the last two months. Totals have surpassed normal year total averages in many areas. This has caused countless issues for farmers. It has however grown lots of grass and weeds. I do not know if I have ever seen thistles like we have this year. The moisture has not only helped the weeds grow but has also prevented most producers from being able to get out and spray weeds.
While it is too late to do anything for thistles other than just shred them, it is time to manage other summer perennials. Three of the most problematic perennial summer weeds that need controlling from now for the next month are: bull nettles, silver leaf nightshade, and Carolina horse nettle. All three of these are very difficult to control but are best controlled now while they are in the flowering stage. Flowering stage will typically start now and run for about the next month.
Both silver leaf nightshade and horsenettle are toxic to livestock, but with all the grass out there now, I would not expect them to eat these weeds, but if you have cattle in pens or run short on grass they can browse on these and the results can potentially result in death for your livestock. Due to these weeds ability to reproduce from both seed and rootstock, they are difficult to control. The best method of control will be through the use of herbicide.
You will not eliminate all the weeds with a single spraying but should expect about 70% control. In heavily infested areas, a ground broadcast spraying will be needed. The most effective herbicides for controlling these three summer perennials are either Grazon P+D at 1 to 1.5 quarts per acre, GrazonNext at 1.5 to 2.1 pints/acre, Weedmaster or Range Star at 1 quart per acre or Chaparral at 2.0 to 3.0 oz./acre. The total spray volume per acre should range between 10 to 30 gallons per acre. Due to the hair-like leaves, it is very important to use a good surfactant at 1 to 2 quarts per 100 gallons of spray mixture. Again, for optimal control, it is best to spray while the plants are flowering.