Friendly Fungus With Dirty Name Takes on Southern Menace

By Jan Suszkiw
May 25, 1999

Wiping out smut is a campaign for some folks. But in Louisiana’s bayou country, Rex Millhollon is actually trying to encourage it--loose kernel smut, that is. The fungus, Sphacelotheca holci, is the respected agronomist’s latest jab at halting Johnsongrass, a loathsome southern weed that keeps popping up in the region’s sugarcane fields every year.

Millhollon is exploring this biological approach to weed control at the Sugarcane Research Unit, operated in Houma, La., by the Agricultural Research Service, chief scientific agency of the U.S. Department of Agriculture.

In the lower Mississippi Delta region of southern Louisiana, where Millhollon’s research takes place, cane growers typically rely on chemical herbicides to rid their fields of the pesky grass. One concern, however, is the potential build-up of chemical residues in the environment. Another is cost: Cane growers can spend up to $50 per acre applying chemical controls. Though a good sugar crop can defray the expense, each new season is met by a fresh contingent of the weed, necessitating another round of herbicide.

To break the cycle, Millhollon has sought to develop the smut fungus into a so-called mycoherbicide. The trick: getting the fungus to infect the whole plant, weakening it and its prolific seed-producing machinery.

In greenhouse experiments, Millhollon injected a smut spore solution directly into the weed’s tissues, causing infection rates of 75 to 85 percent and seedheads resembling a dark, crumbly mass. In a more practical approach, Millhollon formulated the fungus into a mycoherbicide, spraying it onto the weed in field plots. Though 50 to 80 percent became infected, the treatment didn’t protect the plot’s cane crop as well as conventional herbicides. Now, Millhollon is eyeing ways to give the fungus a helping hand, including breeding it with other Sphacelotheca that are more effective at infecting Johnsongrass.

A longer article about smut, the fungus, appears in the May issue of Agricultural Research magazine at:

/is/AR/archive/may99/smut0599.htm

Scientific contact: Rex Millhollon, ARS Sugarcane Research Unit, Houma, La., phone (504) 853-3174, fax (504) 868-8369, Rmillhol@nola.srrc.usda.gov.