UF/IFAS
Okeechobee County Extension Service
458 Highway 98 North
Okeechobee, FL 34972-2303
Phone: (863) 763-6469
E- mail: dfculbert@ifas.ufl.edu
| Quick Links: What is Solarization Procedures Master Gardener class References |
May 31, 2006
Feature Article - for release the week of June 4, 2006Dan Culbert - Extension Horticulture Agent
Cooking up weeds, bugs, and rots
I’ve noticed that Okeechobee has a lot of enthusiastic vegetable gardeners. Many are now lamenting that it’s time to put the trowel down for the season. And as the spring garden is put to rest for the summer, the time is right to reduce future garden pests by cooking them during the summer.
Today’s column was adapted from Hendry County Extension Director Gene McAvoy, and describes how soil solarization can reduce pests in next year’s garden. Following these steps now will take a small amount of time, and save lots of aggravation next year.
Many gardeners are looking for pest solutions that don’t involve pesticides. How about a method that is non-chemical that will reduce all kinds of pests. Gardeners often ask for a treatment that can reduce soil borne nematodes, but since there are no chemicals labeled for nematode control by homeowners, soil solarization may be the only alternative.
Soil solarization is a non-chemical method of pest management. Clear polyethylene plastic is used to cover moist soil that is ready to be planted. The heat generated by sunlight hitting the soil will be trapped under the plastic. Soil temperature can warm high enough to kill many insects, nematodes, fungi and weed seeds in the upper few inches of the bed.
In Central Florida, 30 days of solarization of soil infested with root-knot nematodes and wilt fungi increased tomato yields 48% over those grown in soil that had been left bare (fallow) for the same 30 days. Wilt affected 80% of plants in the fallow plots but only 8% of plants in the solarized plots.
Soil temperatures are magnified because incoming solar radiation is trapped under the clear plastic. Plastic covering the on the soil increases soil temperatures by keeping in the heat and moisture. In addition, a greenhouse effect is produced under the plastic covered garden.
To be effective, soils must start out moist and maintain a high soil moisture content. Moisture increases the heat sensitivity of soil-borne pests and moist soil conducts heat more easily than dry soil.
The best time for soil solarization would be during our hot summer months. Fortunately these are the off-season in most peninsular Florida vegetable gardens anyway. The bad thing is that our summers are also our wettest period of the year. Frequent rainfall will cool the soil and to allow insulating puddle rainwater to sit on the surface of the plastic mulch.
Soil solarization has been used to reduce damage caused by a wide range of soil-borne fungi, weeds, and nematodes in Israel, Jordan, and California. However, it can not be recommended without reservation for Florida, where it has worked well in some trials but failed in others.
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Wider areas of soils can be solarized using wide rolls of clear plastic. Photo: University of California IPM Program. |
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USDA Researcher Dan Chellemi & organic farmer
Kevin O'Dare inspect a raised vegetable bed that
is being solarized in Vero Beach. Photo
by Randall Smith, 
After preparing the garden bed, home gardeners can
cover a row with plastic to begin the solarization
process. Photo: 
Garden plots covered with plastic can cook out
weeds, bugs and nematodes. Photo: 
Soil Solarization Procedures and Precautions
1. Soil should be covered for at least 4 weeks, and preferably longer, during a hot and sunny time of the year. June and July appear to be most suitable in Florida, since air and soil temperatures are highest, and day length and the angle of the sun provide for maximum solar energy hitting the soil at that time.
2. Soil must be well tilled before covering in order to destroy clods and plant debris. Garden refuse can interfere with uniform movement of heat through the soil and protect some organisms from the full effects of the treatment. Other soil preparations such as fertilizing and placing drip irrigation tubes may be completed before covering the plastic over the bed. This will minimize the need to disturb the solarized soil before planting.
3. Soil moisture must be high when the plastic is applied. Wet soil conducts heat better than dry soil, so moistening the soil before tarping will provide for a deeper treatment. Also, most pest organisms are more susceptible to the deadly effects of heat in moist soil; they may be dormant if the soil is dry.
4. Raise the center of the bed to form a small "crown" or peak to enable the covered bed to shed water. Solarization seems to be less effective in periods of high rainfall, probably because water standing on the plastic absorbs the heat from the soil.
5. Use clear polyethylene, not black plastic mulch. Clear plastic produces higher soil temperatures faster than black plastic. Sunlight passes through clear plastic to heat the soil directly. Black plastic holds the light, and soil is heated only on the very surface, where the plastic actually touches the soil.
6. Leave the plastic in place until planting time. It has no detrimental effect on the soil, so it will only lengthen the treatment period and reduce the chance of recontamination before planting. Plastic should be removed before planting any cool season crops that require lower soil temperatures for best growth. However, it is safe to leave the plastic over the beds as mulch for warm season plants that could benefit from higher soil temperatures in autumn.
While soil solarization is not 100% effective against many garden pests, it may be the only tool in the bucket against nematodes. It is a useful tool in the gardener’s bag of tricks for combating pests. Try it - you may like the results.
Plan now for the Fair and the Future
Next spring Okeechobee County will have a County Fair for the first time. Local leaders have decided the time is ripe for our community to showcase the best that we have to offer. Gardeners should start making plans now to showcase the best from your garden, and reducing pests by solarization is a good first step.
Another way to insure success at the fair is to nominate that outstanding gardener, either down the street or in the mirror, and encourage them to be part of the next class of Florida Master Gardeners. Our office is planning to train a class this summer here in Okeechobee. I will be contacting people in the next few weeks to find out the best times to hold this volunteer training class.
There will be lots of Master Gardener help needed not only during the Fair, but helping is needed by other gardeners who want to grow outstanding vegetables and ornamentals throughout the year. Our schools can also use help making their classrooms green, and there are lots of youth that would like to be part of a 4-H gardening club lead by trained Master Gardeners.
I’ve placed more information on our Okeechobee web page, http://okeechobee.ifas.ufl.edu. If you need additional information on soil solarization or becoming a Master Gardener, please email us at okeechobee@ifas.ufl.edu or call us at 863-763-6469. Local residents can stop by our office at 458 Hwy 98 North in Okeechobee, and visit our Okeechobee County Master Gardeners from 1 to 5 PM on Tuesday afternoons.
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Millie Ferrrar, Interim Dean Last update: 08/04/2009
. This page is maintained
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Krueger,
Romy and McSorley, Robert. Solarization for Pest
Management in Florida (ENY-902). Gainesville:
UF/IFAS Extensi
McAv
McBride,
Judy. Turning
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