The Art and Science of the Pest Predictive Calendar
Horticulture & Turfgrass
Ginny Rosenkranz
Extension Educator, Commercial Horticulture
University of Maryland Extension
SALISBURY
Abstract
Insect pests damage ornamental horticulture crops with their chewing, sucking or rasping mouthparts. Depending on the pest, damage can destroy or disfigure the foliage, flowers, fruit, trunk or stem, devastating the appearance of the ornamental trees, shrubs, perennials or annuals. While it is not difficult to learn which insect pests prefer Quercus alba and which other pests prefer Rhododendron minus, it has not always been easy to predict when the Oak lecanium scale first hatches out or the first hatch of the Azalea lace bug emerges. This prediction is most helpful at such a time, when they are at their most susceptible stage for controls. Now, after years of observation and calculating, we can predict that the Oak lecanium scale needs 789 growing degree-days (GDD), while the Azalea lace bug needs only 214 GDD. Growing degree-days are a measure of the ‘heat unit’ that accumulate over time. By keeping track of the temperatures starting at 50? F, it is possible to predict the degree-day when insect pest reaches that susceptible stage. Software and technology can be used to calculate growing degree-days of insect pests or a horticulturist can look around the landscape to see what is blooming about the same time the pests are at their most susceptible stage for control according to a Pest Predicative Calendar. Most horticulturists tend to notice when trees, shrubs and perennials are in bloom, and knowing that when the dainty white urn shaped flowers of Enkianthus perulatus ‘JL Pennock’ begin to bloom (GDD 204), the Azalea lace bug will be out soon. When the fragrant white panicles of Cladrastis kentukea (GDD 627) perfume the air and 3-petaled purple Tradescantia virginiana brighten the landscape (GDD 692), it is time to check the Oak lecanium scale for crawlers. Using the knowledge of landscape plants when they bloom and insect pests that consistently damage them, it is now possible with the Pest Predictive Calendar to plan ahead and apply controls at the optimum time.
Authors: Ginny Rosenkranz
-
Ginny Rosenkranz Extension Educator, Commercial Horticulture, University of Maryland Extension, Maryland, 21802