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Organic options available for garden pest control
MISSISSIPPI STATE -- The trend toward green or organic production has made its way to many home gardeners, but Mississippi's climate makes it a challenging place to grow plants without harsh chemicals to control pests.
Lelia Kelly, consumer horticulture specialist with the Mississippi State University Extension Service, said a big part of growing organic gardens is being conscientious.
“Call it organic, sustainable landscaping or just being more green, but to me, it all comes under the heading of realizing that what you do in the garden has an impact beyond us,” Kelly said. “A good, observant gardener will know if something is getting out of hand and needs to be treated.”
Whether gardening organically or not, Kelly said the best defense against diseases and insects is keeping plants healthy.
“A healthy plant is the result of good cultural practices, and the basis of that is building and maintaining good soil,” she said.
Gardeners can't garden from the kitchen window, Kelly said. They must be out with the plants, checking for soil moisture, making sure plants are not holding moisture on the leaves, watching for insect damage and fighting back weeds.
“We need to be a bit more tolerant of a little damage,” Kelly said. “It's nice to strive for the perfect garden, but you may not need to react immediately by putting out chemicals that may not be needed for minor damage.”
Blake Layton, Extension entomologist, offered another suggestion for a successful Southern organic garden: grow relatively pest-free plant species and varieties.
“Organic insecticides tend to be less effective than conventional insecticides, but there are exceptions,” Layton said. “There are quite a few effective organic products that work well against caterpillars and soft-bodied insects, but there aren't many that work well against beetles and insects like stink bugs, lace bugs and plant bugs.”
He gave some specific suggestions on what organic chemicals can be used to fight off insects.
Spinosad is very effective against most caterpillar pests, thrips and leaf miners. Although spinosad is organic, many formulations contain inorganic inert ingredients that don't qualify as organic insecticides, but some products are formulated to comply with organic guidelines.
Bts, short for Bacillus thuringienisis, are naturally occurring soil bacteria that produce toxins that provide some caterpillar control. They are generally slow-acting, and the caterpillars must eat them before they work.
Azadirachtin is a natural insect-growth regulator derived from seeds of the neem tree. It is slow-acting but effective against sucking insects, such as whiteflies and aphids. Neem oil, also obtained from the seeds of this tree, controls these same insects.
Pyrethrin, or pyrethrum, is a natural extract from the flowers of the pyrethrum daisy. It is a broad-spectrum insecticide that affects most insect pests by contact. If another chemical is added to increase its effectiveness, it no longer can be considered organic.
Iron phosphate is used as a slug bait and to control snails. Rotenone is a botanical insecticide derived from several plants that is moderately effective against beetles and true bugs, such as stink bugs and plant bugs.
Sulfur has long been used to control spider mites and certain plant diseases and is approved for organic production as long as no inorganic ingredients are added. It can be used as a dust for spider mite control, but sprayable options are available. Lime-sulfur is used primarily as a dormant spray on woody ornamentals to control scale insects, mites and certain diseases.
Petroleum-based horticultural oils are useful for controlling scale insects and soft-bodied pests, such as aphids, spider mites and whiteflies. Although the oils are classified as organic, many of the secondary ingredients are inorganic. A number of organic oils made from plants and fish are effective against soft-bodied insects, such as aphids, mites and whiteflies.
“With organic insecticides, you may have to spray more often, you may sustain more damage on certain plants, and there may be some insect problems you just can't control,” Layton said. “But organic insecticides also have one important advantage -- they are usually less detrimental to nontarget beneficial insects than conventional insecticides are. Beneficial insects provide much more free insect control than most gardeners realize.