Gardening : New Weapon Against Pests in War of Roses : Soaps combined with insecticides seen as way to kill bugs without harm to environment.

Roses are thought to be easy prey to all sorts of bugs and beasties and diseases, and while modern pesticides offer a convenient way to curb such problems in the garden, there is a regeneration of products that are reported to have no toxicity to humans, soil and ground water.

The main ingredients are soaps that have insecticidal and fungicidal properties, marketed by Safer Inc.

Over a century ago, soaps derived from fish and shale oils were used to combat the rose aphid and other insects, but just as they were becoming commercially available in the late 1920s, modern pesticides appeared.

Almost 60 years later, in the 1980s, the tables seem about to be reversed. The public’s growing perception of pesticides as dangerous and toxic to the environment has stimulated a re-investigation of certain soaps as nontoxic pesticides.

The secret of producing the right soap for the right job, be it against insects, fungus, weeds or spider mites, has been pioneered by Safer Inc. Their research chemists have quickly identified which soaps among the potential 100 or so members of this chemical class are actively pesticidal.

Concept All Wrong

The concept by home gardeners that hand soaps or Woolite are effective agents is just all wrong. Household soaps, for instance, contain a mixture of about 10 different soaps all found to be ineffective as insecticides.

Application of such household products can actually harm your rose plants. The soaps studied by Safer Inc. have been carefully selected to target particular insects and diseases. For example, Safer soaps destroy the ability of the insect to breathe by interacting with the semipermeability of their cell membranes.

These new soaps have strengths and weaknesses. Their general acceptance is based on the simple fact that they are nontoxic to humans and do not threaten the environment (soil and ground water). Their weakness or flaw is that they are contact killers--there is no residual or long-lasting protection much beyond the day after they are applied to the roses.

Conventional pesticides and fungicides such as Orthene and Funginex, on the other hand, do have good residual effects lasting as long as seven to 14 days to ensure a full measure of control over future invasions.

Soap sprays may also harm the foliage of roses. Most roses in their first bloom cycle have lush new growth that is extremely tender. Frequent applications of soap-based products have been observed to cause such tender foliage to be disfigured and often destroyed, particularly if used more often than weekly.

Mixed With Pesticides

The dilemma lies in the inability of soap-based products to have long-lasting control, thereby encouraging multiple applications per week. Since roses always have new tender growth, whatever the month, care should be exercised.

Since these soaps are natural spreader-stickers they can enhance the effect of pesticides when the two are mixed together. Most pesticide formulations for home use already have a spreader-sticker incorporated into them to make sure the pesticide remains on the foliage after spraying.

What the new soap-based products offer is an additional spreader-sticker that is not merely an inactive ingredient but an active agent against the pests. Should you want to try this, proceed cautiously, using minimum amounts of pesticide and soap until you are sure they will not harm the plant.

Fighting Spider Mite

What might be considered the most beneficial aspect of soap-based products is the development of a miticide to fight the spider mite problem. In the heat of summer, spider mites can greatly expand their populations into the millions on the underside of the foliage.

If unchecked, they literally suck the life out of the foliage, causing complete defoliation of the rose bush though not the death of the plant.

The conventional pesticides like Vendex and Plictran recommended to kill spider mites can be harmful to the young developing foliage.

Rose growers have elected to spray the undersides of the foliage with plain water to wash off the mites rather than use toxic chemicals. The option of using a soap-based product is a therefore welcome relief since washing with water was not a totally effective procedure.