Biological Control Systems Cut Flower Growers Should Consider

Several insects and mites will attack young cut flower seedlings as they’re started in greenhouses. If you start your season early, biological control is a very viable option. This involves starting plants that will serve as insect-infested crops on which predators and/or parasites are released, and ideally, increase in number. The benefiial organisms migrate off the banker plants and kill the insects feeding on your cut flower seedling plants. This involves a little foresight but is very practical and cost effective for most growers.

Papaya Banker Plants  for Whitefly Control

Ashton Dickey, Lance Osborne, and Cindy McKenzie published a paper in 2011 on  infesting papaya plants with papaya whitefly, Trialeurodes payaya (syn. Carica papaya). This whitefly limits its feeding activity to papaya and plants in its family, which are not generally grown in a greenhouse environment. You can purchase papaya fruit from the grocery store, remove the seeds, and start the plants in pots. The papaya plant is then infested with the whitefly. The parasitic wasp Encarsia sophia (transvena) is released on the plants; the females sting the sessile stage of the whitefly and lay eggs inside. The banker plant is then moved into the greenhouse where the parasitic wasp adults migrate search and sting sessile stages of Bemisia tabaci, silverleaf whiteflies, which infest many greenhouse-grown cut flowers.

Biological supply houses are now investigating what is required to ship out papaya whitefly to states other than Florida where it already exists.  Once this hurdle is crossed we will have a potentially very good banker plant system to deal with whitefly in greenhouses. Check with biological suppliers to see if they can ship these in 2016.

Grass Mites for  Two–spotted Spider Mite Control

One pest doing major damage to cut flowerand other greenhouse crops is the two-spotted spider mite. Growers raise fieldcorn plants in pots and infest the foliage with Banks grass mites (Oligonychus pratensis), which feed only on monocots such as corn and other grasses. Once the mite population is established they release two predatory mites, Amblyseius californicus and Phytoseilus persimilis, onto the corn plants. These two predatory mites feed on the grass mites, reproduce, and when the banker plant is moved into the greenhouse, they migrate off the corn and search for spider mites on plants in the greenhouse. Grass mites are found in many states so shipping them from biological supply houses should be a smaller obstacle to hurdle.

For More Information

In February of 2016 the University of Maryland Extension published a new issue of the 440-page manual entitled “Total Plant Management for Greenhouse Production with Emphasis on IPM”. This manual is loaded with information on biological and chemical control (latest label updated) for plants grown in greenhouses. It not only has insect and mite control but also disease management, weed control, and fertility management information. The manual is $30 plus shipping. To obtain a copy send an email to me at [email protected]

Stanton Gill

Extension Specialist

Stanton Gill is an extension specialist (professor-ranked principal agent) in IPM and entomology with the University of Maryland Extension, based at the Central Maryland Research and Education Center in Ellicott City. He is also a professor in the Landscape Technology Program at the Germantown Campus of Montgomery College. Contact him at [email protected]