5-step program keeps viruses out of greenhouses

There is never a good time for a virus infection. Virus infections cause problems and financial losses for everybody. These outbreaks affect all segments of the supply chain. EuroAmerican Propagators in Bonsall, Calif., has always strived to reduce virus infections in its stock and production plants. In July 2004 the company decided to significantly step up its efforts. While the average greenhouse will likely not have the resources for a comparable undertaking, there are plenty of take-home lessons that apply to any size growing operation.

EuroAmerican has had its share of virus infections. As a result, plants had to be destroyed and replaced. Not only did this cause a financial loss to EuroAmerican, but it inconvenienced its customers along with negatively impacting the company in regards to being a reputable young plant supplier. Fred Ceballos, EuroAmerican’s stock production manager since 2004, was given the task of systematically reducing virus infections in the company’s stock plants. He developed a 5-step program to:

1. Improve testing.

2. Improve training.

3. Improve sanitation methods.

4. Improve production planning.

5. Monitor results.

Every step is crucial for the overall success of the program.

1. Improve testing.

To improve testing procedures, EuroAmerican cooperated with Agdia and University of California-Riverside to develop better tests for scrophularia mottle virus (SCRMV). In addition to conducting enzyme-linked immunosorbent assay (ELISA) tests in-house and in Agdia’s lab, EuroAmerican uses polymerase chain reaction (PCR) tests, a DNA-type test performed by Agdia and the university. These broader and more thorough tests enable the company to identify and eliminate a wider range of viruses.

Every production greenhouse should consider ELISA tests. Test kits can be purchased for in-house testing or plant samples can be sent to commercial diagnostic labs.

“If tests are done in-house, it’s imperative that they are done thoroughly and according to protocol, and that dedicated, skilled personnel perform the tests,” Ceballos said.

To keep track of the tested plants, EuroAmerican spray paints them.

2. Improve training.

Ceballos developed a bilingual training manual for the 35-100 employees who work in the stock plant area. Employees acknowledge receipt of the manual by signing a document.

Since most of EuroAmerican’s labor force consists of untrained workers, considerable time and effort is spent every year to train employees in virus-prevention procedures. “We have two employees whose sole responsibility is the training of the workers and the enforcement of the procedures,” Ceballos said.

The training manual details sanitation procedures, including wearing disposable hairnets, coveralls, aprons and gloves. The manual indicates when and how often to wash hands, use of disinfecting footbaths to clean shoes and when to clean pruners, hoses and brooms. It also explains viruses, how they spread and how they can be prevented. It even details which foods can carry certain viruses. Since there is a potential for contamination with tobacco mosaic virus (TMV), workers are not allowed to smoke and are advised to avoid contact with tobacco products and not to smoke even away from work.

3. Improve sanitation methods.

Ceballos said “an impeccably clean greenhouse is the first step toward good sanitation practices and healthy plants.” But he said that sanitation goes much further than maintaining greenhouse floors. EuroAmerican’s elite greenhouse, which is screened against insects and maintained under strict sanitary conditions, is a stock production house that contains plants tested to be free of pathogenic viruses. Plants are tested monthly for up to 18 viruses.

Workers and visitors enter the company’s elite greenhouse through a double-door prep area where they suit up in disposable coveralls and hairnets. This same prep area contains a hands-free wash station with faucets controlled by foot pedals. Workers then enter the greenhouse by stepping onto a footbath mat saturated with a disinfecting solution. Similar footbath stations are set up between greenhouse sections.

Aprons and gloves are required whenever working with plants. Both need to be changed between working on greenhouse tables and between varieties for those who harvest cuttings and every hour for irrigators.

A similarly rigorous cleaning regimen is in place for pruning shears. The shears must be cleaned after every plant with Lysol and heat-sterilized after every five pots. In the elite greenhouse, the shears must be heat-sterilized after every single pot.

Irrigation hoses and spray hoses are disinfected with a Physan solution by dipping the first 15 feet of the hose into the disinfectant after exiting each plant row. Individual brooms are assigned to each greenhouse bench, and all are disinfected regularly with a Physan solution. To diminish the risk of spreading diseases and viruses, Ceballos and his co-workers take great care to make sure that hoses and brooms are never taken from one greenhouse to another.

EuroAmerican operates four “clean stock” houses that contain cuttings propagated from plants in its elite greenhouse. The screening, testing and sanitation conditions are generally the same in the clean stock houses as in the elite house.

4. Improve production planning.

A spotless greenhouse doesn’t do much good if the plants in it are old and in poor health.

“The longer a plant sits in a greenhouse, the more often it’s being harvested and the more likely it is to contract a virus over the course of its life cycle,” Ceballos said.

EuroAmerican maintains a rigid schedule of rotating plants out of the greenhouse, replacing old stock plants with new, tissue-cultured stock on a regular basis.

5. Monitor results.

An elaborate sanitation program is only as good as achieving the desired results so monitoring the success rate is imperative. Since implementing the program, the number of virus infections in EuroAmerican’s stock plants has been reduced dramatically. There have been no cases of calibrachoa mottle virus since November 2006, and only two instances of scrophularia mottle virus and nemesia ring necrosis virus since November 2005.

The most dramatic reduction in virus infections occurred after EuroAmerican began strict enforcement of its sanitation rules, which includes serious consequences for rule violations. If employees violate the rules more than once during four months, they are terminated. Rule violations include not using or changing aprons, gloves and clippers as often as mandated, not disinfecting clippers as required, or cutting from upper and lower lines of plants instead of from just one line as required.

Once these strict consequences were enforced, rule violations dropped from an average of 15-20 per month during peak production to 0-4 per month. When a month passes without a single violation, EuroAmerican treats its stock production team to a free lunch.

“We’ve learned that unless the rules are strictly enforced and consequences are implemented, people get lax about abiding by them,” Ceballos said. “Now we have two people whose sole job is to train the employees and monitor for rule violations. They are not necessarily very popular with their co-workers, but their job is vital, and the obvious success speaks for itself.

For more: EuroAmerican Propagators LLC, (888) 323-0730; www.euroamprop.com.

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- Kerstin P. Ouellet

Kerstin P. Ouellet is president, Pen & Petal Inc., (760) 451-2385; kerstin@penandpetal.com; www.penandpetal.com.