Roundup WeatherMax Research Articles

Improved bioherbicidal efficacy by Myrothecium verrucaria via spray adjuvants or herbicide mixtures

Herbicides and spray adjuvants were evaluated for compatibility with the bioherbicidal fungus, Myrothecium verrucaria. Several commercial formulations of glyphosate were found to be compatible for tank mixing with M. verrucaria, including Touchdown ® and RoundUp HiTech ®. Others, such as Accord XRT II ® and RoundUp WeatherMAX ® killed all the spores of M. verrucaria immediately after mixing at only 10% the maximum labeled application rate. Many herbicides, which were not suitable for co-application with M. verrucaria, did not inhibit the growth of the fungus when added directly to media at up to 1% concentration, indicating that these products could be compatible with M. verrucaria as sequential applications in an integrated weed management system. Several commercially available spray adjuvants and polyoxyethylene tridecyl ether (TDA) formulations were tested in vitro for their efficiency in dispersing spores and in a plant bioassay for bioherbicidal activity. All of the products improved the activity of M. verrucaria over the water-only treatments and TDA formulations with a hydrophilic–lipophilic balance (HLB) number of 8 or 10 had the highest activity. The mechanism for improved bioherbicidal activity with these adjuvants was investigated in vitro, and TDA HLB 8 and 10 did not significantly improve conidia dispersal or accelerate spore germination relative to other surfactants. It is possible that the role of the surfactant is in the alteration of the plant cuticle or otherwise preparing the infection court. Better adjuvant selection and integration with affordable synthetic herbicides should aid in the development of more cost-effective biological control of weeds.

Toxicity of a glufosinate- and several glyphosate-based herbicides to juvenile amphibians from the Southern High Plains, USA

Pesticide toxicity is often proposed as a contributing factor to the world-wide decline of amphibian populations. We assessed acute toxicity (48 h) of a glufosinate-based herbicide (Ignite ® 280 SL) and several glyphosate-based herbicide formulations (Roundup WeatherMAX ®, Roundup Weed and Grass Killer Super Concentrate ®, Roundup Weed and Grass Killer Ready-To-Use Plus ®) on two species of amphibians housed on soil or moist paper towels. Survival of juvenile Great Plains toads ( Bufo cognatus) and New Mexico spadefoots ( Spea multiplicata) was reduced by exposure to Roundup Weed and Grass Killer Ready-To-Use Plus ® on both substrates. Great Plains toad survival was also reduced by exposure to Roundup Weed and Grass Killer Super Concentrate ® on paper towels. New Mexico spadefoot and Great Plains toad survival was not affected by exposure to the two agricultural herbicides (Roundup WeatherMAX ® and Ignite ® 280 SL) on either substrate, suggesting that these herbicides likely do not pose an immediate risk to these species under field conditions.

Microbial Degradation of Fluometuron Is Influenced by Roundup WeatherMAX

Laboratory experiments were conducted to describe the influence of glyphosate and fluometuron on soil microbial activity and to determine the effect of glyphosate on fluometuron degradation in soil and by Rhizoctonia solani. Soil and liquid medium were amended with formulated fluometuron alone or with two rates of formulated glyphosate. The soil carbon mineralization was measured hourly for 33 days. The fluometuron remaining in the soil was quantified following 3, 6, 10, 15, 20, 30, and 40 days of incubation. The fluometuron remaining in medium and fungal biomass was measured after 1, 3, 6, 10, 15, and 20 days of incubation. The addition of glyphosate with fluometuron increased C-mineralization and increased the rate of fluometuron degradation relative to fluometuron applied alone. However, more fluometuron remained in the media and less fungal biomass was produced when glyphosate was included.

Soil Microbial Activity Is Affected by Roundup WeatherMax and Pesticides Applied to Cotton (Gossypium hirsutum)

Adoption of glyphosate-based weed control systems has led to increased use of the herbicide with continued use of additional pesticides. Combinations of pesticides may affect soil microbial activity differently than pesticides applied alone. Research was conducted to evaluate the influence of glyphosate-based cotton pest management systems on soil microbial activity. Soil was treated with commercial formulations of trifluralin, aldicarb, and mefenoxam + pentachloronitrobenzene (PCNB) with or without glyphosate (applied as Roundup WeatherMax). The soil microbial activity was measured by quantifying C and N mineralization. Soil microbial biomass was determined using the chloroform fumigation-incubation method. Soils treated with glyphosate alone exhibited greater cumulative C mineralization 30 days after treatment than all other treatments, which were similar to the untreated control. The addition of Roundup WeatherMax reduced C mineralization in soils treated with fluometuron, aldicarb, or mefenoxam + PCNB formulations. These results indicate that glyphosate-based herbicides alter the soil microbial response to other pesticides.