Greenhouse Grower Notes: It’s a small world for flower growers

May 04, 2009
Written by Graeme Murphy
Each year, the Society of American Florists, organizes its annual Pest Management Conference, usually held in the middle of February and alternating between the west and east coasts of the U.S. The meeting is a mix of growers, industry representatives and researchers/educators/extension specialists. The 2009 meeting was held in San Jose, California, from Feb. 19-21, and focused on a number of issues of relevance to Ontario growers.

With the widespread movement of plant material around the world, new and invasive pests are a major problem for greenhouse growers everywhere. The U.S. industry is as concerned and affected by this issue as the Canadian industry.

A number of presentations dealt with invasive and/or quarantine pest problems for the U.S. General presentations were given by Lin Schmale from SAF, and by Helene Wright from USDA-APHIS in California who provided background to the problem and described the difficulties involved in protecting U.S. agriculture from new pests.

This photo illustrates the size difference between chilli thrips (left) and western flower thrips (right). (PHOTO COURTESY UNIVERSITY OF FLORIDA)

They also outlined the process that is set in place when a new pest is discovered, and the growers’ roles and responsibilities (which are the same as for Canadian growers). Finally, Schmale described a couple of case studies of invasive pests in the greenhouse ornamental industry in the U.S. (Ralstonia and the geranium industry, and Q-biotype whitefly) and how they were handled at both grower and government levels.

Steve Tjosvold from the University of California reviewed the history of Sudden Oak Death (Phytophthora ramorum), its implications on the nursery industry in that state, and how the lack of knowledge of the organism required a massive injection of research effort to better understand and make management decisions.

Finally, Dr. Lance Osborne (U of Florida) discussed the management of invasive pests from a grower’s perspective. He set the tone for the presentation by observing that, in Florida, it has been estimated there is one new invasive pest species established per month, and in California, one every two months. Recent pest/disease problems that have either affected the ornamentals industry (or have the potential to) include:
Q-biotype whitefly.

Chilli thrips.

Red palm mite.

Pink hibiscus mealybug.

Thrips palmi.

Light brown apple moth.

Sudden oak death.


Chrysanthemum white rust.
In Canada, we can add pests such as Duponchelia, banana moth and Swede midge (although the last of these has recently been deregulated by Canada and the U.S.). Dr. Osborne also spoke of the approach taken with two of these pests, Q-biotype and chilli thrips. Task forces were formed that brought together all components of the industry: propagators, growers, pesticide companies, government agencies, researchers and trade media, to develop a co-ordinated and co-operative approach to dealing with the problem and developing a consistent management approach.

The other major focus of the meeting was the management of pesticide resistance. The primary discussion centred around the neonicotinoids family of pesticides, of which there are three:

Cloronicotinyls, which include Intercept and Tristar.

Thianicotinyls, which include the products thiamethoxam and clothianidin, neither of which is registered in Canadian greenhouses, although there is interest in registering both of these products in the future.

Furanicotinyls, which includes dinotefuran (Safari in the U.S.) and which is unlikely to be registered in Canada, at least in the foreseeable future.
This group of pesticides is prone to development of resistance, which has been observed in imidacloprid (Intercept). Growers of poinsettia can attest to the fact that this product has lost much of its effectiveness against whitefly. Differences in level of control with these products (for example, dinotefuran works well against Q-biotype, but imidacloprid doesn’t), can be attributed to differences in water solubility of the products. Dinotefuran is much more soluble in water, resulting in faster and more efficient systemic uptake of this product, and therefore a greater concentration of pesticide in the leaves. However, there is concern that the development of resistance will eventually limit the usefulness of the group, so considerable effort is being put into resistance management programs.

Although a number of presentations focused on the above topics, there was plenty of other information for those who attended. Ann Chase (Chase Research Gardens), Mary Hausbeck (Michigan S.U.), David Norman (U of Florida) and Colleen Warfield (U of California) discussed various aspects of plant disease management, ranging from specific issues such as downy mildew, root rots and foliar diseases, to more general information on fungicide resistance and disease diagnosis.

This annual meeting is unusual in that for two days, its focus is firmly on pest management in greenhouse ornamentals. It brings together a wide range of players in the industry and allows growers who attend the opportunity to meet with researchers and many industry representatives. Although most growers who attended were from the U.S., there were also some Canadians who were also able to take away much useful information (although pesticide discussions need to be treated with some care since many U.S. registered products are not available in Canada). However, this is a meeting that is valuable, provides useful information, and if growers have the opportunity, they should try to get to at least once.

Graeme Murphy is the greenhouse floriculture IPM specialist with the Ontario Ministry of Agriculture, Food and Rural Affairs at Vineland.
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