Archive for natural pest control

Alternatives to Toxic Insecticides

Alternatives to Toxic Insecticides

By George Giltner, Adv. Master Gardener, MS Biology

A third study now validates results of earlier research of associations between autism and prenatal exposure to agriculture chemicals (www.ehp.niehs.nih.gov/1307044/).  “Women who are pregnant should take care to avoid contact with agricultural chemicals whenever possible” says author, Janie F. Shelton who is now a consultant with the U.N.

Three groups of common pesticides were studied that included organophosphates (chlorpyrifos, acephate, diazinon, and others), pyrethroids (esfenvalerate, lambda-cypermethrin, taufluvalinate, and others), and carbamates (methomyl, carbaryl, and others). The organophosphates were associated with an elevated risk of autism spectrum disorder, especially chlorpyrifos applications in the second trimester. Pyrethroids had a moderate association with autism spectrum disorder immediately prior to conception and in the third trimester. Carbamates were associated with developmental delays.

The present rate of autism is now at 1:68 births according to estimates from the CDC.  Also about 1 in 6 children in the United States had a developmental disability in 2006-2008. In the birth year of 1992, the prevalence of Autism Spectrum Disorder was 1 in 150, which has steadily increased to 1 in 68 in the 2002 birth year.

Therefore as gardeners, we should always use the least toxic chemicals, read labels, follow all safety precautions, and keep up with the latest research concerning pest control.

The good news is that more and more information is available on less toxic pesticides.  Clemson Cooperative Extension has an outstanding article on “Less Toxic Insecticides” which conscientious gardeners should print out (www.clemson.edu/extension/hgic).  “Most essential oils used as pesticides work by disrupting an insect neurotransmitter that is not present in people, pets, or other vertebrates.” The EPA no longer requires approval for use as pesticides due to minimum risk to uses of these essential oils (cedar, cinnamon, citronella, citrus, clove, garlic, mints, rosemary and others).

Microbial insecticides include Bt (Bacillus thuringiensis) for caterpillar control.  Milky Spore (Bacillus papillae and lentimorbus) is used against June bug larvae – grub worms. Spinosad, Saccharopolyspora spinosa is a treatment for fire ants, caterpillars, thrips, whiteflies, aphids, and even borers of fruit trees. Beneficial nematodes are the good nematodes that control clearwing borers, cutworms, sod webworms, mole crickets, and grub worms.  However nematodes are difficult to get started due to humidity, moisture, shipping, and temperature issues.

Bacillus subtilis and pumilus combat downy and powdery mildews, rust, bacterial spot, blight, botrytis and multiple other mildews on veggies, fruits, ornamentals, trees, and shrubs.

Minerals like boric acid acts as a stomach poison which causes the insects to die from starvation.  Diatomaceous Earth controls slugs, millipedes, ants, cockroaches, and soft-bodied insects like aphids. However use the “natural grade”, not the swimming pool filtering-agent that poses an inhalation hazard.  Sodium Fluoaluminate has sharp edges which punctures insect (caterpillars, sawflies, beetles, etc.) gut cells from consuming leafy material, however beneficial insects are not affected since they are not leaf eaters.  Iron phosphate is used as an organic slug and snail bate.  It is not poisonous to cats and dogs.

“Organic Farm and Garden” 2013, Vol.1, 2nd Ed., lists Biological Control Options which incorporates predator and prey functions in every ecosystem.  Plant nectar sources attract beneficial insects, and allow them to lay eggs near this food source.  Plant small flower favorites like dill, parsley, fennel oregano, cilantro, and thyme.  Also include annuals like sunflowers, cosmos, amaranth, alyssum and statice.  Perennials like yarrow, tansy, daises and angelica can be inter-planted within your garden.  Your beautiful garden will buzz with beneficial insects, and will have an ecological balance of predator and prey bugs.

“Louisiana Gardener”, Feb. 2015, has a super article, “What’s Bugging You?” by Cindy Shapton.  She puts emphasis on learning good bugs and bad bugs. Numerous recipes for repellants to easy to make sticky-traps are highlighted.

“The Naturally Bug-free Garden”, 2012, by Anna Hess is now available at Amazon.  It focuses on the worst garden pests that we have here and in Texas, and gives organic control measures.  Good bugs and good animals are reviewed and used to make your garden a living balance of natural defenses.  Resistant varieties, row covers, companion planting, and plant nutrition are tools for helping plants resist insects.  This is a good book to assist the beginner and young gardeners in learning about organic gardening.  It is a treasure!

So this year, learn, read, and experiment with organic chemical-free gardening to avoid potentially dangerous chemicals that are used in commercial agriculture.

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Battle of the Bugs: Citrus Leafminer & Natural Control

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Battle of the Bugs: Citrus Leafminer & Natural Control

By George Giltner, Adv. Master Gardener, MS Biology

If you have planted Satsuma’s or other citrus within the past 3 years, chances are that the leaves have been mined by the citrus leaf miner, Phyllocnistis citrella.  Close observation of the distorted wrinkled leaves will show the twisting larval tunnels, larval frass trail, and possibly the live larvae itself.

When the larvae are near the leaf marginal edge, use a fingernail to extract one.  Then you have successfully controlled one leaf miner, needless to mention that several hundred that may be ready to hatch from recently laid eggs by the 2 mm long adult female moths.  The singly laid eggs hatch after 4 to 5 days, then begin their mining operations for over a month, usually from midsummer to early winter.  The leaf distortions and curls are caused by the destruction of upper and lower cellular tissue.

juvenile leafminer

The larva of a leafminer feeding between the top & bottom surfaces of a citrus leaf. Photo by UFL Extension.

As you review the entire citrus plant, notice the pattern of infestation.  New fast growing and tender leaves are infected, but the hardened thicker leaves are resistant to leaf miners.  Therefore activities that stimulate rapid plant growth like pruning, vertical water sprout growth, and heavy fertilization actually make your citrus more favorable to citrus leaf miners.  Also notice that older (4+ years) trees are not impacted like younger trees.  The aged and hardened older leaves cannot be penetrated and mined like fresh leaves.

Commercial products containing imidacloprid, a systemic insecticide, have been used during periods of flushing (rapid growth) of young citrus.  These soil or irrigation treatments can protect the plants for up to 3 months.  However, there is concern over the use of this insecticide and its effect on bees.  The systemic insecticide will be inside plant tissues, pollen, and nectar.  Experts report that use of this chemical is one of the many possible causes of bee decline and colony collapse disorder (CCD).  The European Food Safety Authority (Jan. 2013) stated that neonicotinoids (imidachoprid) pose an unacceptably high risk to bees.

If you are an internet user, some suggestions for leaf miner control are absolutely hilarious.  One suggests using moth balls.  The response was to take good aim at the moths to be effective.  Another was to use Sevin, but the larvae is tunneled and protected by the waxy leaf cuticle.

Biological control can be the most effective means of control.  Worldwide, 39 parasites of CLM have been identified.  14+ natural enemies (many wasps) have been identified within the U.S.  Since the initial identification of CLM in Homestead, Florida (1993), it has spread throughout the South into Louisiana and Texas.  It is now a common pest.  However recent research has shown up to 90% mortality due to endemic beneficial insects.  The message from researchers is to not use wide range killing insecticides (malathion, carbaryl, and pyrethroids) that destroy beneficial predators of citrus leaf miner.  Better control with less environmental impact can be obtained by using spinosad formulated products like Conserve, Green Light Spinosad, Success, Leafminer & Tent Caterpillar Spray, etc.

adult leafminer UF pic

Adult Leafminer. Photo by Florida Extension

Gardeners and homeowners of citrus may choose to not treat citrus for citrus leaf miners.  That is correct – do nothing and let nature take its course (Dr. Malcolm Manner, UFC) .  Young citrus will be infected and look ugly for several years.  Nature will begin to supply CLM predators without the use of harmful insecticides.  The mature hardy thick green leaves develop.  Then the citrus tree matures into its round dark green form.

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