Keep your greenhouses clean After listening to presentations by numerous ornamental plant pathologists and entomologists at this year's Society of American Florists' 21st Annual Pest Management Conference, I began to wonder why any grower wouldn't have in place a comprehensive sanitation and scouting program. Sure, there are different means of preventing disease and insect outbreaks including physical barriers such as screening, potting substrate pasteurization and chemical controls. Fortunately for ornamental growers, there is an increasing arsenal of chemical and biological controls to combat whatever new pest broaches our borders, regardless of how it gets here. Even though USDA's Animal and Plant Health Inspection Service is revising Quarantine-37 regulations that govern plant imports, I don't expect the changes to affect the way most growers deal with indigenous pests. From December through April 10, APHIS is accepting public comments regarding whether Q-37 regulations needed to be amended and specifically how they should be changed. While these changes should have the biggest impact on companies that ship cuttings and seed into the United States, the greatest impact on domestic growers could be product availability, or lack thereof. Regardless of whether Q-37 changes open or tighten the pipeline to offshore product, growers need to be more diligent in their efforts to prevent domestic and foreign pests from becoming established. Based on the conference presentations, numerous tools are available. And growers are going to need all of them to battle new and existing pest challenges. Tougher to control Ohio State University entomologist Luis Canas reported that a new silverleaf whitefly, Bemesia tabaci biotype Q, is winging its away toward the United States. Canas said this whitefly, first identified in Spain, has made its way to the Caribbean and Central America already. Unlike biotype B, biotype Q has shown a resistance to imidacloprid, one of the most effective whitefly chemical controls used by U.S. growers. Israeli researchers have found that biotype Q has also developed resistance to the insect growth regulator pyriproxyfen. One of the major differences between these two whiteflies is that Q does not cause a silvering of the leaves. Canas recommends that growers do diligent monitoring in all production stages to accurately determine which whitefly is present. Insects aren't the only pests becoming more difficult to control. North Carolina State University plant pathologist Colleen Warfield told conference attendees that Thielaviopsis basicola, which causes black root rot, is becoming a year-round disease. This soil-borne fungus attacks a variety of bedding plant crops including pansy, vinca, petunia, heuchera and verbena. Warfield points out that although fungicides can suppress the pathogen, it is hard to control. Warfield said it has been very difficult to identify what is the source(s) of the disease in the greenhouse. She has done tests on numerous samples of Canadian sphagnum peat moss and pansy seed and has not detected the disease. But she has found the pathogen on planting line and soil mixing equipment as well as growing media taken from the floors of potting areas. She advised growers not to reuse plug trays, which can harbor Thielaviopsis spores and can cause upwards of 80 percent disease infection on susceptible plants. Warfield told growers to be more aware of where and how their growing media are being stored and how often and how planting line equipment is being cleaned. Growers who start a crop with clean plant material, containers, media, equipment and production facilities will have an easier time producing a quality crop. But a conscientious effort has to be made to scout and treat for insects and diseases, whether chemicals or biological controls are used, to keep the crop pest free. Send this article to a friend Enter your e-mail address: Enter your friend's e-mail address: Click the image below to send: © 2004 Branch-Smith Publishing