Field sanitation before and after planting is critical in the fight against important vegetable pests.

Field sanitation is one of the most important tactics in vegetable pest and disease management. The best thing growers can do for themselves and their neighbors is to clean up crop residues promptly after harvest. Sanitation is an important integrated pest management (IPM)technique that should not be overlooked as an effective, preventative tool against many vegetable pest and disease problems. Sanitation includes any practice that eradicates or reduces the amount of pathogen inoculum, pests, or weed seeds present and thus helps reduce or eliminate subsequent pest and disease problems.

In crop production, sanitation includes practices such as removing weeds that harbor pest insects or rodents, eliminating weed plants before they produce seed, destroying diseased plant material or crop residues, and keeping field borders or surrounding areas free of pests and pest-breeding sites.

Constructive Destruction

Prompt crop destruction at the end of the season will immediately end the production of disease inoculum and insects and eliminate the spread of diseases and pests to any other host plants in the vicinity. Downy and powdery mildew on melons can spread via wind from older, diseased plants to plants in surrounding fields that are still maturing. These diseases are obligate parasites. This means they can only grow and multiply on living host tissue. Some plant pathogens, like the bacterium that causes bacterial spot of tomato and pepper, are unable to survive for extended periods of time outside of the host tissue. Plowing or discing under infected plant debris helps not only by covering up the inoculum but also speeds up the disintegration of plant tissue and kills the pathogen. Good sanitation will help control a number of important vegetable pathogens.

Destruction of tomato vines will kill off whitefly populations and eliminate transmission of the tomato yellow leaf curl virus (TYLCV) to subsequent crops and also eliminate inoculum from late blight and other fungal diseases. This is particularly important in the case of TYLCV, as sanitation and whitefly control are the only tools currently available for the management of this disease. A crop-free period also is considered a necessity for the control of a number of other important vegetable pests including pepper weevil, tomato pinworm, and Thrips palmi, and is recommended for management of all vegetable pests. Techniques like mowing off pepper and eggplant should not be relied upon as this often results in re-sprouts, which can harbor pests and disease problems over summer.

Weeds and volunteers also should be removed to prevent the survival and over-summering of pathogens that could serve as inoculum reservoirs for the next crop. Don’t forget to destroy weeds on ditch banks, in windbreaks, and field perimeters because they might serve as alternate hosts for insect pests and diseases.

Cover Up

The use of cover crops and summer fallowing of fields are also effective tools in reducing weed populations that can cause problems in the subsequent crop. The role of summer fallow in weed management often is overlooked. Summer fallow keeps new weed seeds from being added to the soil seed-bank. It also reduces the increases in asexual propagated plants like nutsedges. Yellow nutsedge can produce 70 new tubers (nuts) every two months. Keeping the weeds from propagating will reduce the weed problems encountered during the next cropping season and help reduce insects and diseases that may over summer in weedy fields. Old farmers often went by the adage, “one years seed — seven years weed,” as a reminder of the consequences of allowing weeds to go to seed.

Chemical fallowing is a twist on the traditional method of fallowing that depends on discing fields throughout the summer period to reduce weed pressure in subsequent crops. Chemical fallowing uses herbicides, like glyphosate, to kill weeds during the crop-free period.
The key to a successful chemical fallow program is the timing of the applications. Two glyphosate treatments with one tillage trip in between should cover the entire fallow period. Repeated applications at a low rate give better results than one application at a high rate.

Procedure For A Typical Chemical Fallow Program:

• Disc field and laser level after harvest.
• Allow weeds to germinate and grow to a desirable height (about 25 to 30 days).
• Treat with glyphosate (first treatment).
• Allow treated weeds time to translocate product throughout plant (at least one week).
• Lightly disc field (can be one to five weeks after herbicide treatment).
• Allow weeds to germinate and regrow to a desirable height (about 25 to 30 days).
• Treat with glyphosate (second treatment).
• Allow treated weeds time to translocate product throughout plant (at least one week).
• Prepare field for planting (can be one to five weeks after herbicide treatment).
• Allow three days between last application and planting. Hard water, containing cations, such as calcium, magnesium, iron, and manganese, can bind to the glyphosate molecule, reducing efficacy. The addition of ammonium sulfate and use of low-water volumes can help reduce these antagonistic effects.

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