Killer Pathogens Can Be Murder on Crops

Courtesy of Growing America

They lurk deep down in the soils in crop fields—little murderers with names like Rhizoctonia, Pectobacterium and Pythium. You can’t see them, but you can see the mayhem they cause to your crops. Rotting roots. Wilted leaves. Lesions. Stunted growth. Money out the window.

“Soil-borne plant pathogens can limit or even ruin an entire vegetable or fruit crop if left uncontrolled,” says Vijay Kumar Choppakatla, Plant Pathologist/Director of Research and Development for BioSafe Systems. “The challenge is that many of them have a very broad host range, making a wide variety of crops susceptible to the destruction they can cause…and often you don’t know the pathogens exist until the worst damage is done.”

Choppakatla says it doesn’t take much to create the perfect pathogen storm. Among plant pathologists, and at BioSafe, a family-owned manufacturer of biodegradable disease-control products, based in East Hartford, Connecticut, that perfect storm is known as the “three corners of the disease triangle.” You start with a virulent pathogen, add a susceptible host (your crop plants), place in a congenial environment, and boom…a successful plant disease is born.

Even worse, soil-borne pathogens tend to be hardy—some of the nastiest fungal-based pathogens such as sclerotia can thrive in some of the harshest conditions and persist in the soil for many years, whether or not a field is planted.

Bottom line? Once pathogens have made themselves comfortable in your soil, they’re difficult to eradicate. Difficult, but not impossible.

Combination of Management Practices

Choppakatla says most growers use a combination of management practices to combat pathogens, including cultural, chemical and biological methods, all to achieve what today is generally known as “biosecurity.” In simple terms, biosecurity is the elimination and prevention of disease pressures in an environment, thereby maintaining a healthy growing area. The challenge is to exercise biosecurity while being kind to the environment

  1.  Cultural Methods

When you think “cultural” management of soil-borne pathogens, think about the things you’re likely doing already such as adding organic matter to your soil, rotating crops, planting cover crops between fields, controlling irrigation, and disposing of culled produce somewhere where it won’t re-infect a field.

Another simple yet powerful eradication method is soil solarization, literally using the heat from the sun to kill the bad organisms. While it may not be viable for large fields, it works well in smaller plots.

According to Rodale’s Organic Life, the process involves laying a clear plastic tarp atop soil cleared of plant debris to concentrate the sun’s energy in the top 12 to 18 inches. The heat trapped below the plastic can reach highs of 140°F in the top 6 inches, killing weed seeds, insects, nematodes, and many fungal and bacterial pathogens. It’s worth noting that the beneficial effects from solarization are greatest near the soil surface and decrease with depth.

2.    Chemical Methods

Chemical methods involve use of soil fumigation prior to crop planting, seed treatment with chemicals and post-plant soil fungicides.

“Using chemicals can be effective, however, the application processes can be cumbersome and intensive,” says Choppakatla. “Some soil fumigants require growers to adhere to special management plans to properly administer the treatment and avoid any non-target exposure to the applied fumigant. Plus, there’s a waiting period between application and planting of about 3 to 4 weeks. It’s also critical to create buffer zones around the treated fields.”

Moreover, Choppakatla points out, for organic growers, conventional fumigants aren’t even an option. Which is why many farmers, traditional and organic alike, turn to the natural option of biological-based control and eradication of soil-borne pathogens—solutions that are not only safer for the environment, but also for people and animals.

3.    Biological Methods

Biological-based methods (Bio-control) involve the use of registered bacterial and/or fungal-based bio-control agents; natural preventiatives which protect plant roots from soil pathogen infection; and use of soil inoculants which use beneficial endophytes (microbes) to promote plant health.

Choppakatla says the primary objective of these all-natural treatments is to address soil-borne pathogens in a way that maintains sustainable soil health without negatively impacting the health and safety of people and the environment.

“An important consideration in the use of biological management options is that they are primarily preventive in nature,” notes Choppakatla. “In other words, they help to prevent the infection but may not help with control once infection is established. So timing of application is key with this method.”

BioSafe’s treatments involve integration of chemical and biological based methods designed to help with controlling soil pathogens while maintaining/improving the soil health, which is critical for plant growth.

“The chemical treatment method we’ve developed involves use of activated hydrogen peroxide-based chemistry and both of the products in the system are non-residual and non-toxic.”

Among the products based under this group of chemicals (H202 + PAA) are TerraStart and TerraClean 5.0 which Choppakatla says are both EPA approved for use as a soil bactericide/fungicide. TerraClean 5.0 is also OMRI approved for use in organic production.

“Upon application to the soil,” explains Choppakatla, “the products basically sanitize the soil by oxidizing the plant pathogenpropagules immediately on contact. Then the chemicals break down into water, oxygen and acetic acid, which are completely safe by-products. As an added benefit, there is a release of oxygen, a bonus benefit because it helps oxygenate the plant root zone.”

We all want effective solutions for maintaining healthy soil that contributes to healthy growth and high yields, and sometimes the idea of “alternative methods” can give us pause. As part of a company that specializes in those alternative methods, Choppakatla knows well the hesitation some growers have to try new technologies.

“Ask the hard questions, read up on reliable efficacy data, and do the math to make sure it fits your budget. But above all, whatever treatment plan you adopt for your operation, consider its effects on the environment.”

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