Sanitation is critical to prevent plant diseases Part 2: Field sanitation

Good sanitation in the field will reduce pathogen inoculum in vegetable plants.

Zucchini yellow mosaic virus on leaves. Photo credit: Gerald Holmes, California Polytechnic State University at San Luis Obispo, Bugwood.org

Zucchini yellow mosaic virus on leaves. Photo credit: Gerald Holmes, California Polytechnic State University at San Luis Obispo, Bugwood.org

Sanitation is one of many tactics needed for an effective disease management strategy in the greenhouse and field. Sanitation includes any practice that aims to prevent the spread of pathogens by removing diseased and asymptomatic infected tissue, as well as decontaminating tools, equipment and washing hands.

This article will help you and your employees use good sanitation and reduce pathogen inoculum, also known as “seeds” of the pathogen. Consistent and effective sanitation greatly increases the chances of raising healthy plants.

Sanitation in the field

Sanitation in the field needs to take place before, during and after the growing season. Prior to planting, fine-tune your weed management plan. Many weeds are known reservoirs for plant pathogens and insects. By controlling weed populations in your fields, you can reduce pathogens and their vector populations.

Wash soil off of farm equipment, including brushing off soil particles from shoes. These practices are especially important to prevent movement of soilborne pathogens such Sclerotinia sclerotiorum (causal agent of White mold), Phytophthora capsici, Verticillium dalhiae and different species of Fusarium. A power washer is an important piece of equipment in the battle against these diseases. Plows, discs, cultivators and other pieces of equipment should be power washed between fields.

Avoid working fields when plants are wet. This practice minimizes bacterial spread from diseased plants to healthy ones. For example, this tactic is important for tomato bacterial diseases such as spot, speck and canker that can prove challenging to control once in the field.

Remove infected plants or plant parts. As soon as symptoms appear, collect, bag and destroy or pile diseased material away from fields. Removing infected fruit and plant debris from the field can reduce the amount of pathogen inoculum that could move into healthy plant parts. Cull piles should be placed away from production fields and waterways and, if possible, covered with a plastic tarp to speed up microbial decomposition and minimize pathogen spores from escaping. Burn, chop and spread, or deep plow debris at the end of the season. The choice of practice depends on the specific disease that was present in the field the previous season.

At harvest, carefully pick only healthy produce and avoid any mechanical damage on the fruit or other plant parts harvested. Damage such as small wounds or bruises can be the point of entrance for microorganism that can compromise fruit quality while in transit or storage (short or long term).

Clean tools during use, disinfecting knives, shears and other harvesting tools often. To accomplish this, wash tools with soapy water and dip or wipe in 70 percent ethanol or other products. It is important to refresh sanitizing solutions as specified on the product label. Tool sanitation and hand-washing can help minimize plant-to-plant spread of diseases caused by several bacteria and viruses. Provide hand-washing stations equipped with clean water and soap. During harvest, careful hand-washing is critical to minimize plant pathogen spread. For example, tobacco mosaic virus (TMV) can be transmitted to tomatoes and peppers if hand-washing is poor after smoking cigarettes. This tobacco virus is very stable and can be present on dry tobacco in cigarettes.

Examples where sanitation can help break the disease cycle

Disease name*

Pathogen

Transmission

Crop

Virus

TMV

Tobacco mosaic virus

Hands, tools

Tomato

PVX

Potato virus X

Tools, machinery, aphids

Potato, and related plants (tomato, pepper, night shade weeds etc.)

PVY

Potato virus Y

Tools

SqMV

Squash mosaic virus

Tools, cucumber beetles, seed

Cucurbits

ZYMV

Zucchini yellow mosaic virus

Tools, aphids, seed

Cucurbits

PMNV

Pepper mild mottle virus

Tools, seed

Pepper

CMV

Cucumber mosaic virus

Aphids, weed hosts

Cucurbits, celery, pepper tomato, bean spinach, lettuce

BCTV

Beet curly top

Weeds hosts

Beet, tomato and legume families

TSWV

Tomato spotted wilt

Thrips, weed hosts

Tomato, pepper, lettuce, variety of vegetables

LNSV

Lettuce necrosis stunt virus

Soil, water

Lettuce

Bacteria

Bacterial speck

Pseudomonas syringae pv. tomato

Seed, tools, hands, weeds

Tomato

Bacterial canker

Clavibacter michiganense pv. michiganense

Weed hosts, plant debris, tools, hands

Tomato

Bacterial spot

Xanthomonas campestris pv. vesicatoria

Seed, weeds hosts, tools, hands, soil and plant debris

Tomato, pepper

*Click on the disease name and the link will direct you to additional information and/or pictures of symptoms.

Sanitation requires detail-oriented employees. Always inspect plant material prior to planting in the field. Plant material can carry diseases and insect pest, introducing them to clean and new fields. Instruct employees on how to recognize common disease symptoms and pests. Scouting often and thoroughly is needed to identify problems as early as possible. The more eyes available to look at your vegetables plants in the greenhouse and the field, the more chances issues can be identified earlier.

Plant viruses
Photo credits: TMV, (APSnet.org). SqMV, H. Lecoq, INRA Station de Pathologie (Bugwood.org). Bacterial spot, Clemson University (Bugwood.org). ZYMV, Bacterial canker and bacterial speck, Gerald Holmes (Bugwood.org)

The table in “Disease or disorder: How do I tell the difference? Part 2” can be useful in training your employees. Click on the disease name in the table and the link will direct you to a symptom image to help with scouting.

Field sanitation practices summary

  • Remove plant debris and infected plants as soon as symptoms appear by collecting, bagging and removing.
  • Burn deep plow debris in the fall or chop and spread early in winter.
  • Disinfect knives, shears and other harvesting tools often.
  • Frequent hand-washing with clean water and soap.
  • Wash soil off farm equipment (power wash preferred) between fields.
  • Brush soil particles off from shoes when moving in between fields (brushes or boot covers are handy).

For Part 1 of this two-part series, see “Sanitation is critical to prevent plant diseases Part 1: Greenhouse sanitation.”

Spanish versions of these article series are available for download:
Part 1 – Saneamiento en el invernadero: qué se debe hacer para evitar la transmission de enfermedades en hortalizas
Part 2 – Saneamiento en el campo: qué se debe hacer para evitar la transmission de enfermedades en hortalizas

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