Why are whiteflies so difficult to control?
In warmer climates, whiteflies can breed year around, moving from one host to another as plants go through the production cycle. Whiteflies can quickly build up to high numbers on susceptible plants, such as poinsettias. Colonies occur on the underside of leaves, making them more difficult to target – especially when using contact insecticides. Over the years, whiteflies have also developed resistant populations that can withstand triple the amount of insect control products that was successful a decade ago. This makes it very important to rotate insecticides with different modes of action. It’s good stewardship not to apply more than two sequential applications of any insecticide within the same Insecticide Resistance Action Committee (IRAC) group.
What cultural practices can growers implement to protect their plants from whiteflies and other sucking pests?
Identify and closely monitor plants known to host high whitefly populations, then isolate affected plants and break off leaves supporting high infestations. Ornamental plants that are highly attractive to whiteflies include poinsettia, hibiscus, ivy, gerbera daisy, lantana, verbena, garden chrysanthemum, salvia and mandevilla. Weeds can also be favorable hosts for whiteflies and should be removed or controlled with herbicides. Yellow sticky traps can aid in monitoring and may help to reduce high populations.
Are there any new developments in whitefly control?
insecticide was recently introduced to the ornamental market as a solution to control sucking pests. It is an entirely new class of chemistry, butenolide, placed in IRAC group 4D. It is upwardly systemic and has translaminar capabilities, allowing it to move readily through leaf tissue. Thus, foliar applications over the plant canopy will target insect pests found on the underside of leaves. Altus is labeled for use before, during and after bloom, making it an excellent addition to integrated pest management (IPM) programs.