A naturally occurring fungus may help control Palmer amaranth, a type of pigweed that in many areas has become resistant to glyphosate and other herbicides.
Research chemist Robert Hoagland and plant pathologist Doug Boyette, both stationed at an Agricultural Research Service facility in Stoneville, Miss., identified Myrothecium verrucaria as a possible biological control, according to a news release.
The fungus previously had been shown in studies to control sicklepod, kudzu, hemp sesbania and other weeds.
In the recent trials, the researchers used a filamentous fungal growth stage known as mycelium.
They sprayed a special formulation onto two batches of 4-week-old Palmer amaranth seedlings—one with glyphosate resistance and one without.
They also conducted the trial with 6-week-old plants.
The researchers than visually evaluated the plants for symptoms for seven days application and then weighed the plants for reductions in shoot growth.
Seedlings were the most susceptible, with all plants showing disease symptoms. Within 72 hours of application, nearly 100 percent had died.
In the 6-week-old plants, symptoms progressed more slowly. Both the herbicide-resistant and susceptible groups showed symptoms, including chlorosis, some necrosis and stunted growth.
There was no difference in injury between the resistant and susceptible plants.