Decisions for Rose Pest Control

Lois Brandt

ARS Consulting Rosarian, Accredited Horticulture Judge, Accredited Arrangement Judge

If you grow roses, you will make decisions on pest control, even if the decision is not to do anything special to control the pests that infect your roses. In Albuquerque the most bothersome pests are powdery mildew, thrips, spider mites and aphids.

The selection of the rose to grow is the first decision. Roses vary in their susceptibility to some of these pests. Flower Girl, a modern shrub, is an example of a rose that does not seem to get powdery mildew while other roses such as Fragrant Cloud, a hybrid tea, and Nancy Jean, seem to be highly susceptible. Thrips seem to prefer light colored roses over dark red roses (or maybe they just show more on the light colored ones) .

A healthy rose plant is less susceptible to damage from pests than one that is already stressed from poor growing conditions. Therefore all the decisions that we make concerning culture will make some difference in the incidence of pests. It is important that roses are grown with at least 6 hours of sun daily in soil with good drainage and lots of organic material added. Ideal soil pH for roses is between 6.0 and 6.5. Variations from this pH number will affect the availability of the nutrients required by roses. In Albuquerque the soil and the water are usually much more alkaline than this and should be altered to make more acid.

Adequate water and nutrients are essential for healthy rose plants. The higher the concentration of roses growing in an area, the greater the likelihood of increasing the abundance of pests. For this reason rose spacing is important.

Pesticides are any chemical used by man to control pests. This includes insecticides, fungicides and miticides for use on roses. All of the pests listed here are living organisms with some of the same chemical pathways that are present in humans and other chemical pathways that are unique to their species. The ideal chemical control is one that will only affect the pest and not humans and other species that you want to conserve. Some pesticides are not very toxic while others are highly toxic and very dangerous. For this reason, decisions have to be made on the effectiveness of a particular chemical to be used against a pest. Is it harmful to humans and other animals and will it have long-term environmental effects?

The product label gives information on the toxicity of the chemical, for what it should be used, how it should be applied, health concerns and numbers to contact in case of a product accident. The label should be carefully read and understood before using any pesticide and all precautions followed exactly. Left-over chemicals should be properly stored for later use or properly disposed of according to environmental protection rules.

More detailed information regarding a product can be found on the internet under household products database. This site will give you the Material Safety Data Sheet information that is prepared by the manufacturer and collected by The National Library of Medicine. Here you can find health warnings associated with a particular chemical. Some of the health problems caused by these chemical are irreversible, some are acute effects, and some are chronic effects from continued exposures. It also gives health ratings for the product, and handling and disposal information. This is the type of information that is especially helpful to you for making an informed decision concerning a particular product. It also can be an incentive to be more careful in handling some of these dangerous chemicals.

Two chemicals that are often used by rose growers are: Bayer Advanced Garden 2 in 1 Systemic Rose and Flower Care granules and Rose Pride Orthinex Insect and Disease Control. According to the Material Data Safety Sheets, their chemical actions are similar and they both have potential for serious and similar health effects. They both list a number of health problems including skin irritation and irreversible eye damage if these chemicals are mishandled. Probably the most serious effect is cholinesterase inhibition. This enzyme is essential for the release of energy that is required in living cells. Ingestion, skin contact or inhalation of either of these products can result in over exposure and serious health risks that could lead to respiratory failure or cardiac arrest. This is an example of the type of information that can be gained from this site and will enable you to make more informed decisions.

Always take the proper precautions to avoid skin contamination or inhalation. Wear the proper clothing (including rubber gloves) to avoid direct contact with all chemicals. Shower immediately after spraying and wash clothing separately that you have worn when applying chemicals.

The rose hybridizers are working to try to grow roses that have more resistance to pests. Until now no pest-resistance gene has been found. One hybridizer grows the new plants in fields without using any chemical sprays. Those that show pest resistance are the only ones that are selected for commercial development.

So until pest resistant roses are produced, use the most available knowledge for choosing the least harmful methods that will give you the best pest control .

[Ed. note: This article first appeared in the Blue Ribbon, the Newsletter of the Albuquerque Rose Society. Published here by permission of the author, who was given an ARS Award of Merit for this article.]