"Reducing disease pressure starts with a clean facility"

The adage ‘an ounce of prevention is better than a pound of cure’ certainly applies to growers who want to reduce disease pressure on greenhouse produce,” says Vijay Choppakatla, Ph.D., Director of Research at BioSafe Systems.

“Prevention is the best strategy for managing plant disease in indoor production, and it all starts with a clean facility,” Dr. Choppakatla says.

To better understand the concept of disease prevention in the greenhouse, growers need to consider the disease triangle, which illustrates one of the paradigms in plant pathology. When disease is caused by a biotic agent, it requires the interaction of a susceptible host, a virulent pathogen, and an environment that favors disease development, according to the American Phytopathological Society.

“Growers must disrupt one or more of these components to control the disease,” Dr. Choppakatla states.

The environmental component of the disease triangle can be controlled by regulating the humidity and the temperature, which can influence pathogen type and disease severity, Dr. Choppakatla says. In some cases, resistance can be fortified in the host plant so it can fight off disease, he adds.

However, Dr. Choppakatla reiterates that the best way to prevent pathogens from creating disease is to keep the greenhouse clean. Growers need to implement controls to remove pathogen inoculum from plants and disinfect surfaces (growing benches, floors, etc.) and tools (pruning, harvesting, etc.).

It’s also important for growers to monitor irrigation water, which can be a pathogen source, Dr. Choppakatla advises. If the water source is the city or a well, it should be clean. But if the source is open surface water, like an irrigation pond, it could contain pathogens that damage plants, he adds.

“If the water tests positive for pathogens above a certain threshold, then it’s important to consider a water treatment,” Dr. Choppakatla adds, noting that irrigation lines leading into the greenhouse also need to be clean and free of biofilm, which can harbor plant pathogens.

Dr. Choppakatla advises the use of two products by BioSafe Systems.ZeroTol® 2.0, which debuted in 1998 and is BioSafe Systems’ flagship product, kills more than 20 different plant pathogens, including powdery mildew, Botrytis, Xanthomonas, and Rhizoctonia. The OMRI-Listed peroxyacetic acid-based product is not a fungicide in the traditional sense because it is not systemic. It boasts on-contact activity and improves the efficacy of other FRAC code chemistries and helps them maintain their performance longer.

SaniDate® 5.0 works on contact to control plant and human health pathogens on hard, non-porous surfaces, tools, and equipment. It also addresses biofilm, including bacteria, algae, polysaccharides, and plant pathogens such as Pythium and Phytophthora, and will kill foodborne pathogens such as E. coli. SaniDate 5.0 is also a peroxyacetic acid-based product but with a different composition. Like ZeroTol 2.0, the OMRI-Listed product features a clean chemistry with no harmful residues.

Dr. Choppakatla says there’s been confusion regarding straight H2O2 products and peroxyacetic acid chemistries and stresses their notable differences. “Because of the peroxyacetic acid, they (ZeroTol 2.0 and SaniDate 5.0) have a very high oxidizing potential compared to straight hydrogen peroxide,” he explains. “Once they get in contact with the pathogen cell, they interfere with the cell membrane, so the oxidation reaction happens on the surface of the cell, which results in immediate disruption of the cell membrane. With this mode of action, the pathogen doesn’t have a chance to develop resistance,” he adds.

After application, the active ingredients in ZeroTol 2.0 and SaniDate 5.0 break down into water, oxygen, and acetic acid, respectively. “The byproducts from these products don’t stay in the environment,” Dr. Choppakatla says.