Battle Of The Bugs

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Interest in alternative pest control strategies seems to come and go based on the efficacy of the products currently available to growers. But when their tried and true formulations stop working, there’s a collective scramble to find out what else can be used to manage pest populations. The Pest & Production Management Conference hosted by the Society of American Florists and Greenhouse Grower in Orlando, Feb. 25-27, was the place to be to get the most current information.

Growers also are pursuing alternative methods to help with their sustainable and organic certification initiatives. They want to gain experience with what really works before they abandon or supplement traditional control products. Margins are not forgiving enough for crop failures.

Experimenting With Essential Oils

Raymond Cloyd and his students at Kansas State University have been testing the efficacy of essential oils derived from plants for pest control. The oils are harvested through steam distillation. They are looking at their properties and modes of action to battle pest populations as antifeedants, molting and respiration inhibitors, growth and fecundity reducers and cuticle disrupters.

“These oils may delay or mitigate resistance,” Cloyd says. Other advantages the oils have are being viewed as reduced-risk products by EPA and the potential to be certified for organic production by Organic Materials Review Institute.

Oils being tested include cinnamon, rosemary, clove, garlic, lavender, peppermint and sage. The ones that are most effective also tend to damage plants by causing phytotoxicity. Manufacturers will need to develop the right formulations and assure the oils are harvested from plants consistently. Plant nutrition affects the oils.

Cloyd and his students have also been testing sugar-based compounds to see if insects really have a sweet tooth. SucraShield derived from wild nicotiana really performs more as a desiccant, drying bugs up. He also tested Mountain Dew to attract thrips and it had no impact.

Banking On Beneficials

Lance Osborne of the University of Florida has been working with growers to establish populations of beneficial mites and insects. There are regional considerations when using beneficial predatory mites and insects. Many pests and beneficials are host specific and natural predators can vary. “What works up North doesn’t work here in Florida,” Osborne says. For instance Encarsia sophia is a beneficial wasp that is a natural predator in Florida but has not been commercially available.

Much of Osborne’s work has been developing banker plant systems to establish beneficial populations. Banker plants that are different from the rest of the crop are placed strategically in greenhouses and populated with pests that will not bother the rest of the crop. The pests on banker plants provide food to sustain beneficial predators, which can take care of the rest of the crop. “If you can grow natural enemies, they are very efficient in finding pest populations,” he says.

Examples of banker plants that are being used in greenhouses are ornamental pepper ‘Black Pearl’ for thrips, corn for mites and papaya for whiteflies. This same system is even being used in landscapes to alleviate the need for sprays. In regions like Florida, where there is no true winter, keeping infestations at bay is a must. Another advantage to using living organisms is no resistance issues occur, as they can with chemical sprays. Over time, pests become resistant as they are naturally selected to survive the sprays.

University of Florida students recently produced a poinsettia crop using biocontrols. Growers could potentially use beneficials for most of the production cycle and then use a chemical product at the very end to get rid of all bugs (good and bad) before plants are ready for retail.

Managing Resistance

Major pests, like whiteflies and thrips, become a target for pesticide resistance, because they are so pervasive. Cindy McKenzie of USDA’s Agricultural Research Service in Fort Pierce, Fla., has been collecting whitefly samples to identify resistant biotypes. There are 26 whitefly biotypes with type A being native to North and South America, B to Asia Minor and Q to the Mediterranean. Whiteflies were first noted as a pest on tobacco crops in 1889. The B type became a problem in the 1980s on hibiscus.

When the resistant Q type was found in Arizona several years ago, our industry came together to contain it. Growers in California, Florida, Arizona and elsewhere sent in anonymous samples to have them biotyped. Although there have been resistance issues with B and it has a wider host range, B will revert back to being susceptible to pest control products, but Q will not. From 2005-2009 researchers tested 44 different products and formulations on Q and it was resistant to all chemistry classes. Since then Safari, Judo and Kontos have proven to be the most effective.

While Q had been detected in 25 states, there were no new findings in 2009, which means USDA and the industry succeeded in containing it. This cooperative effort has served as a model to tackle more pest problems, like chilli thrips.

One of the biggest issues growers have with thrips is there aren’t enough products on the market to rotate to minimize resistance. One effective product that is being overused is Conserve, says Scott Ludwig from Texas A&M University. He explained chemicals don’t mutate bugs but provide the environment for natural selection. Those that survive create the new populations. Another reason thrips are especially tricky to control is they feed on pollen and burrow inside the centers of the flowers, shielding them from chemical contact.

Just like with the Q-biotype whitefly crisis, leading entomologists have come together to develop a thrips management program with recommendations based on the level of infestation. An aggressive treatment program is recommended when plants are virus hosts and thrips are present. There are also maintenance treatment programs with and without biological controls.

For the most current information and updated mode of action classification charts, visit the Insecticide Resistance Action Committee website. 

Delilah Onofrey directs Flower Power Marketing for the Suntory Collection. She can be reached at donofrey@gmail.com

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