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Compost Shows Promise In Chile Disease Experiment

LAS CRUCES -- Phytophthora root rot, or chile wilt, is "Public Enemy Number One" to New Mexico's chile industry, especially in Dona Ana County. But compost from woody waste may be an environmentally friendly solution to getting a grip on the spread of this soilborne disease and "damping off" fungus, said a New Mexico State University horticulturist.


"Composts often act like natural fungicides, thus reducing the amount of fungicides that have to be applied to control soilborne diseases in greenhouse crops," said George Dickerson, horticulture specialist with NMSU's Cooperative Extension Service.

Composts, particularly those made from woody wastes, have long been used in the nursery industry as a partial substitute for peat moss in potting mixes, Dickerson said.

"In theory, fungi and actinomycetes that are involved in the final curing process of a woody-based compost tend to out-compete soilborne pathogens like damping off organisms for water and nutrients in potting soil," he said.

Damping off fungus took a heavy toll on chile stands early in the 1995 season throughout New Mexico, including Dickerson's experimental chile plots at the Dickie Ogaz farm in Garfield.

"We chose a biosolid compost from the City of Albuquerque for our chile wilt experiment on the Ogaz farm this past spring," Dickerson said. "Besides the fact that it was made from woody landscape waste that was diverted from the landfill, it also was a high-quality compost that met Environmental Protection Agency specs for biosolids or sludge."

Heavy rates of compost decreased losses from damping off by as much as 30 percent or more early in the season.

"We were pretty excited early in the season," Dickerson said. "Unfortunately, plants began to die off in plots where 30 tons or more of compost were applied per acre. We attributed losses to salts accumulating in the middle of the beds from the compost."

Compost application rates of 10 and 20 tons per acre were found to give the best results for suppressing damping off and chile wilt. Final chile yields reflected the same pattern at harvest.

"The effects of the compost on chile wilt were significant, but not as impressive as those for damping off," Dickerson said. "The effects of the various fungi in the compost were probably starting to wear off later in the season when chile wilt is a problem."