Spinosad. . . A New Organically Acceptable Insecticide

 

Until Spinosad (pronounced spin-OH-sid) was discovered, the only organically acceptable insecticide was Bt (Bacillus thuringensis). Bt is a bacterium which when sprayed on or eaten by an insect host will infect the host making it sick and then causing it to die. Bt is very host specific and works only on the caterpillar stages of moths and butterflies. In the past few years a specific variety (Bt, israelensis) was found to infect mosquito larvae and has been used successfully to control mosquitoes developing in stagnant water. With this latter exception, Bt has only been effective by infecting the caterpillars of moths and butterflies.

 

Spinosad, on the other hand, is a bacterial waste product produced by fermentation on a nutrient food source used by the one particular bacterium (Saccharopolyspora spinosa). Although this sounds somewhat disgusting, the product, Spinosad, is a white crystalline solid with an identifiable chemical formula. It is soluble in water but breaks down on a leaf surface or in the soil after a few days so that it does not pose a threat to ground water.

 

In general, Spinosad provides effective control of pests belonging to the following groups: moths and butterflies (caterpillars); flies; mosquitoes, ants, leaf miners and thrips. It is also effective for some beetles and members of the grass hopper family. Unfortunately Spinosad is generally not effective for control of most sucking insects (aphids, mealy bugs, scale) or mites.

 

Spinosad is listed by the Organic Materials Review Institute (OMRI) as acceptable for use during organic farming and gardening and any use where toxic chemicals are to be avoided. The first large scale use of Spinosad was in the Olive orchards of Lindsey, California where olive fruit flies were infesting the orchards and potentially destroying a one-half billion dollar industry. The fly would lay her eggs on the olives and within a few days, the eggs hatched and the maggots bored into the fruit. Within a few weeks, the olives were mushy, filled with excrement and totally useless. Before Spinosad, olive growers had to use toxic chemicals to control the olive fruit fly. The chemicals they used were not available to homeowners and so the flies gradually migrated north and became established in Santa Clara and San Mateo counties. Harvesting olives for home use became out of the question and the mess left by falling, rotting olives was a particular nuisance.

 

Ten years after Spinosad was discovered it became available for use by homeowners. To ensure that spraying takes place at the proper time, pheromone traps have been made available to catch the first olive fruit flies. The homeowner now hangs several pheromone traps in his olive trees and as soon as a few olive fruit flies are caught it’s time to spray with Spinosad.

Spinosad can also be used to control codling moths (cause wormy apples).  The homeowner should place codling moth pheromone traps in apple and pear trees to gauge when to spray for this pest.

 

Many additional benefits followed Spinosad. It is an organic product, listed by the OMRI so that it can safely and legally be used for insect control by any and all homeowners as well as by organic farmers. It is listed for use on such diverse pests as coddling moth, tomato hornworms, cabbage worms, corn borers, thrips and even leaf miners. Up until now there has not been any control for the leaf miners which infest (among other things) Swiss chard. Now you can spray Swiss chard with Spinosad and harvest a day later.

 

Spinosad loses its toxicity after 8 to 24 hours and so it will be necessary to reapply at 7 day intervals for 5 or 6 weeks after the first olive flies or codling moths are caught on the pheromone traps.  It is toxic to bees when wet, but relatively safe for them once it dries.  Because bees do not fly late in the day or after dark, Spinosad should be sprayed on the olive, apple or pear trees in late afternoon, whenever possible.

 

Wegman’s Nursery received its first shipment of Spinosad during the summer of 2007. Spinosad has been formulated for use by the Monterey Chemical Company under the name  Monterey Garden Insect Spray. It is available in pint and one quart sized concentrates as well as in a ready-to-use Hose End Sprayer. We believe that Spinosad represents a new class of insect control products which will meet the needs of a previously unserved gardening group.

 

Spinosad is easy to use. The concentrate is diluted at the rate of 4 Tablespoons per gallon of water and applied to the tops and bottoms of the plant’s leaf surfaces with a tank sprayer. Using the Hose End Sprayer product is even simpler. The container is attached to the garden hose, the water tuned on and Spinosad sprayed on the leaves of the target plant.