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Plant Phenology and Insect Development

May 10, 2000

The proper time to control insects can vary depending on the weather. This is most obvious when an “early spring,” with unusually mild, warm weather, causes insects to be in an advanced stage of development, compared with a “late spring,” when winter weather persists.

The development of plants can be used to predict insect activity. Like insects, the emergence of leaves, flowering, and other phenological events are influ-enced by the weather. Both plants and insects are likely to be affected by cloud cover, rainfall, and the number of hours at various temperatures. The observation of plant phenology, such as bloom time, can let you know when insect pests are susceptible to control methods.

The following is a prediction of the stage of development of several species of insects based on the blooming of bridal wreath spirea or Vanhoutte spirea (Spiraea x vanhouttei). This information is taken from the book Coincide by Donald A. Orton. This 190-page book was published in 1989 and is available from the publisher, Labor of Love Conservatory, 468 S. President, Suite 103, Carol Stream, IL 80188-2894; (630)668-8597.

This plant phenology information is listed to provide a basis for scouting and identifying potential problems. It helps you know when to look for certain pests. It should not be used as a biological calendar spray schedule.

Bridal wreath spirea or Vanhoutte spirea (Spiraea x vanhouttei)

Full bloom:

Birch leafminer young larvae

Elm leaf beetle young larvae

European pine sawfly feeding larvae

Gypsy moth feeding larvae

Pine needle scale crawlers (first generation)

Full to late bloom:

Lilac (ash) borer newly hatched larvae

Oystershell scale (brown) crawlers

Finishing bloom:

Bronze birch borer newly hatched larvae

Most blossoms brown, still a few white:

Flat-headed appletree borer larval hatch

Peach tree borer newly hatched larvae

Viburnum borer newly hatched larvae

Bloom finished:

Oystershell scale (gray) crawlers

Author: Phil Nixon Phil Nixon


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