By Ashley Robinson
The phaseout of methyl bromide continues to stimulate research into the use of other soil fumigants for controlling soilborne pathogens, nematodes and weeds to an acceptable level for production.
Researchers at the University of Florida Institute of Food and Agricultural Sciences (UF/IFAS) are looking at ways to modify the current fumigation system to better reflect the distribution growers once saw with methyl bromide.
“The phaseout from the loss of methyl bromide from where we are now, was not a short one. It’s been going on for decades and I think we’re still in that process,” says Gary Vallad, professor of plant pathology at UF/IFAS. “And of course, this has been kind of a costly process, it’s been a hard process for a number of growers throughout the state and throughout the southeast United States.”
Improving Current Fumigation Systems
In the absence of methyl bromide, tomato diseases have been on the rise, specifically fusarium wilt, caused by Fusarium oxysporum. Since then, growers have been looking to find alternatives to control the disease.
According to Vallad, methyl bromide alternatives are limited in the way they move in the soil.
The biggest weakness that researchers have found with the alternative fumigants is that the fumigant doesn’t reach the soil zones along the edge of the bed and under the tuck of the plastic.
Researchers have developed strategies to improve current fumigation systems using Pic-Clor 60. With the additional of supplemental Pic, researchers saw a 77% decrease in fusarium wilt incidence and yield increase of approximately 21%.
In addition to looking at how to control soilborne pathogens, they also wanted to evaluate strategies to control nematodes.
“In a lot of cases where we run into pest problems, it’s not just one pathogen or nematode. Typically, it’s a mixture of the two,” Vallad says. “So really what we wanted to do is investigate what happens when we put both of these systems together.”
After collecting results from research trials, it was discovered that deep shank Telone applications reduced nematode counts and gall ratings. Also, Pic-Clor 60 or 80 with supplemental Pic and deep shank Telone application was the most effective strategy to reduce fusarium wilt, which actually shocked researchers.
Through further research, they found that Telone is fungicidal to fusarium oxysporum, and by combining both strategies researchers saw yield increases of 25% or more.