Plant Phenology to Help Horticultural Pros Nip Insect Problems in the Bud

AUBURN, Ala.—Auburn University researchers are using an ancient science to develop a practical tool that will help Alabama nursery and landscape professionals monitor and control damaging insect pests more efficiently and effectively. The valuable new resource: Alabama’s first-ever phenology calendar of landscape plants and pests.

By referring to the online calendar, pest managers in commercial horticulture operations will find that keeping a close eye on the flowering stages of several specific plants is a sure-fire way to nip insect problems in the bud.

"Detecting pests early gives the nursery or landscape managers time to control them before they can do major damage, and that can significantly reduce the need for pesticides then and later on," says David Held, Auburn assistant professor of entomology and leader of the phenology project. "The phenology calendar will correlate the bloom phases of several specific sentinel plants with the developmental stages of key ornamental-plant pests, and horticulturists throughout the state can use that information to guide their pest management decisions and use insecticides more judiciously."

Phenology is the study of naturally recurring events in plants’ and animals’ life cycles and how seasonal variations in weather, especially in terms of temperatures, affect the timing of those events. Over the next two years, Held and graduate research assistant Ray Young will be amassing mammoth amounts of data they expect will show that using plant phenology is a reliable way to predict insect activity in ornamental plants.

They are conducting their Alabama Agricultural Research Station-funded research in what Held calls “living laboratories”—five almost-half-acre phenology gardens they have established across the state. One garden is located on the Auburn campus; the others at the Huntsville and Mobile botanical gardens, the Wiregrass Research and Extension Center in Headland and Oak Mountain Middle School in Birmingham.

The same 13 species of familiar flowering plants are planted in every garden, including crape myrtle, hydrangea, camellia, forsythia, sunflower, cherry, loropetalum, liriope, daylily, daffodil, clethra, Indian hawthorn and goldenrod. Held says these “indicator” plants were selected because they provide a continuum of highly visible blooms from January through November.

And it’s those blooms that Young, in Auburn, and several Master Gardeners who live near the off-campus sites are monitoring three times a week, every week, till the last blooms fade. They are recording the bloom stages—first, 50-percent and 100-percent bloom—of each species. They learned how to identify and record each stage early on, during “spring training” sessions that Held and Young presented to the Master Gardeners at each site. 

On the insect side of things, the study is targeting two specific ornamental-plant pests— the dogwood borer and the crapemyrtle aphid—that are problematic from one end of the state to the other. To monitor the former, the researchers have placed pheromone traps in every garden, and Young and the Master Gardener volunteers, who learned the ins and outs of insect trapping during their spring training, are inspecting them weekly. In the case of the latter, the observers will randomly select 10 leaves from every crape myrtle twice weekly and ship them to Held’s lab in Auburn for analysis.

Meanwhile, at the Auburn phenology garden only, Young also is monitoring the developmental stages of six other significant landscape pests: eastern tent caterpillars, azalea lace bugs, lantana lace bugs, Florida wax scale, Japanese beetles and canna leafrollers.

"The dogwood borer and crapemyrtle aphid are our sentinel pest species, so we’ll use the data we collect on them and the bloom data on our phenological indicator plants to determine the reliability of local plant and pest correlates statewide," Held says. "If that’s verified, we then can apply plant phenological indicators for these additional pests to other areas of the state."

Pest management is challenging in nurseries and urban landscapes largely because of the diversity of shrubs, flowers and trees they contain and, subsequently, the diversity of pests they attract. Traditionally, many have applied pesticides based on either calendar dates—not advisable—or degree days, which, to be most accurate, must be calculated based on local data.

Regular and frequent scouting is an effective way to detect insects in their most susceptible stages, but in sizable operations or landscapes, the time and labor involved in such close inspections is prohibitive.

"We know that temperatures determine when plants and insects develop from one stage to the next, and we also know that, regardless of what kind of weather occurs in any given season, plants bloom and insects emerge in virtually the same order every year," Held says. "Phenology of landscape plants and pests is a consistently dependable and easily observable way to predict insect activity. Knowing when insects are emerging and when pesticides will offer maximum benefits will save the horticulture industry time and money and greatly reduce the use of pesticides in the environment."

The online plant phenology calendar will have the potential to improve pest management programs not only for the nursery and landscape industries but for homeowners as well, Held says. The five research gardens will also be used as outdoor classrooms to train and educate the pros and the amateurs on the principles of applying phenology to pest management.


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Contact: Jamie Creamer, jcreamer@auburn.edu, 334-844-2783

Auburn University College of Agriculture
Alabama Agricultural Experiment Station
AUBURN, AL 36849
334-844-4877 (PHONE)  334-844-5892 (FAX)

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