Daniel A. Herms, Department of Entomology, The Ohio State University, Ohio Agricultural Research and Development Center, Wooster, Ohio.
Effective monitoring is the backbone of any Integrated Pest Management (IPM) program. However, planning and implementing a monitoring program in nurseries and landscapes is challenging because of the tremendous diversity of plants, each with its own complement of insect pests. Furthermore, many insects are difficult to detect and observe. Consequently, pesticide applications often are scheduled on a calendar-day basis, which is frequently inaccurate because of annual and geographic variation in weather patterns.
The use of plant phenology provides an alternative approach for predicting insect activity. Phenology is the study of recurring biological events and their relationship to weather. Examples of phenological events include bird migration, flowering of plants, and the seasonal appearance of insects.
The development of both plants and insects is temperature dependent; thus plants may accurately track degree-day accumulation and insect development. If so, then it may be possible to use the flowering sequence of ornamental plants as a Biological Calendar for predicting pest emergence and scheduling pest management activities, such as monitoring programs and pesticide applications.
To test this hypothesis, I monitored the emergence of 43 key insect and mite pests and the flowering phenology of 91 ornamental plants in Secrest Arboretum in Wooster, Ohio, from 1997 to 2002. The critical assumption in the use of plant phenology to predict pest activity is that the phenological sequence — the order in which phenological events occur — remains constant from year to year even when weather patterns differ greatly.
The unusual weather experienced in Ohio over the last year provided an ideal opportunity for testing this assumption. Ohio experienced an especially mild fall and winter last year, which led many people to speculate that phenological patterns of plants and insects would be disrupted substantially in 2002. However, phenological patterns in Secrest Arboretum in 2002 remained highly consistent with previous years, providing strong validation of the Biological Calendar for predicting pest activity.