Using Phenology To Predict Pest Emergence
Terrie Greco, B.A.; HLT Dip.
Phenology? What on earth does that mean? Well, and very simply put, it is the science of making associations with certain stages of plant development with the timing of pest emergence. Climatic variables such as temperature, moisture and day length all play a part in when a plant will break bud and bloom – we can co-relate the hatching of insect eggs, for example – with the bud break or blooming of an ‘indicator’ plant. Good indicator plants are ones in which they are common to a large geographical area (a province or state), are easy to grow and have a short but well defined period of bloom. Gardeners can use indicator plants to predict pest emergence and plan effective treatment at the correct stage. A monthly calendar is not an accurate predictor for plant bloom times. For example, unseasonably warm or cool temperatures in the spring can advance or delay plant flowering. As it says on the USA National Phenology Network (USA-NPN) website: ‘Phenology, put another way, is simply nature’s calendar’. Well said! Here is the link for this website where you can find all sorts of fascinating information and opportunities to become an observer in your area.
Interestingly enough, the plant indicator in bloom may not even be a host for the pest we are watching for– but it has the same climatic requirements to emerge from a life cycle stage as the plant does to bloom.
Example – in Ontario and Quebec – when Saucer Magnolias (Magnolia soulangiana) are in the pink bud stage …. Cooley and Eastern Spruce Gall Adelgids should be treated with natural insecticides. Note that these aphid like-insects do not harm Magnolia, only certain Spruce species and Douglas Fir.
Example – in Ontario and Quebec – when Serviceberry (Amelanchier spp.) is in bloom – Gypsy Moth eggs will begin to hatch
Get the picture? Regardless of where you live in North America, you can find a phenology calendar or publication from your local horticultural or agricultural extension office that can help you accurately predict pest emergence. It’s really the coolest thing to know.
Here are a couple of pictures and links to explain further.
Image 1 – Magnolia soulangiana – Saucer Magnolia in bloom
Image 1 – Magnolia soulangiana – When the Saucer Magnolia is in bloom, gardeners should be checking conifers for Cooley and Eastern Spruce Gall Adelgids.
Magnolia image provided by www.permed.com/…/Magnolia_soulangiana_tree.jpg
For more information and images the Cooley and Eastern Spruce Gall Adelgids, check out the following two links:
http://www.for.gov.bc.ca/hfp/publications/00198/Cooley_spruce_gall_adelgid.htm
http://www.forestry.ubc.ca/fetch21/FRST308/lab4/adelges_abietis/spruce.html
Image 2 - Amelanchier canadensis, Serviceberry in spring bloom
Image 2 – Amelanchier canadensis When the Serviceberry is in spring bloom, gardeners should be watching for the emergence of Gypsy Moth Caterpillars on various tree species. Serviceberry image from the University of Delaware Cooperative Extension, Kent Co.
For information on the Gypsy Moth, check out the following link: