It's all in the phenology......

Below is an article I wrote for my friends at Limbwalker Tree Service in Louisville, KY. Enjoy:

Though it may seem hard to believe, the first flowers of spring will soon be upon us.  It doesn't take a horticultural aficionado to appreciate these brightly colored petaled reproductive organs of angiosperms. The yellows, whites, blues, reds, and purples are a welcomed site after a gray cold winter.  But, the emergence of certain plant species floral displays can be the warning signs for  the appearance of diabolical plant damaging pests.  The study of periodic plant and animal life cycle events and how these are influenced by seasonal and interannual variations in climate, as well as habitat factors (such as elevation) is called phenology.

Smoke bush flowers coincide with Japanese maple scale crawlers.

Monitoring the life cycle of plants (leaf expansion, flowering, color change, etc.) has been used for centuries in agriculture to determine the appropriate timing of when certain crops should be sown.  In fact, the first record of phenology dates back to 974 BC *.  Complementing phenology are growing degree days (GDD).  GDD are calculated by taking the average of the daily maximum and minimum temperatures compared to a base temperature (usually 50°F). GDD are a measure of heat accumulation used to predict plant and arthropod development rates, such as, when flowers of a particular species may bloom, or when a particular insect will become active.

                             GDD      =        (daily high + daily low)     -   50

             2

Growing degree day charts highlighting common tree/shrub pests have been developed by the Ohio State University and Cornell University to name a few.

The use of phenology and GDD is an important monitoring tool for integrated pest management practices in the landscape.  The activity of many plant damaging pests coordinates to either the flowering or leaf expansion of common shrubs and trees, some of which may be in your backyard.  When the hanging white racemes of black locust flowers appear (500 GDD +/-), the invasive emerald ash borer adults are beginning to emerge.  The first flight of the adult dogwood borer corresponds to about 2 weeks after peak dogwood bloom (850 GDD +/-). Eight weeks after the full leaf expansion of red maple (1000 GDD +/-) the most vulnerable stage of gloomy scale appears.  These are just a few examples of using phenological indicators to predict the emergence of tree damaging arthropod pests.

Being in tune with phenology and growing degree days can be invaluable when developing a plant health care plan for our landscapes.  Knowing when insect pests are active allows arborists to make precise treatments, which limit the amount of products applied in landscapes.  This also reduces the chances of harming beneficial, or benign, critters that make our plants their home.  Happy hunting!

*University of Wisconsin

http://hort.uwex.edu/articles/phenology

'Tis the season

The approach of spring means the beginning of 'spray season' for many tree companies.  Any time we introduce a product into the environment, pesticide or fertilizer, we are altering the ecosystem.  It's important to consider some things when choosing pesticides.  How the active ingredient controls the pest and it's residual in the landscape are important concepts in an integrated pest management program.  Care should be taken to choose products that do the least amount of harm to beneficial/benign arthropods.

Pyrethrin and spinoside are two chemicals that control many of the same insect pests.  Both mimic substances found in nature.  The difference? Pyrethrin is an indiscriminate killer of most insects and arachnids, including beneficial insects like lady bugs and mantises.  Meanwhile, spinoside has a low toxicity to many beneficial insects plants rely on for protection from herbivorous pests.  Part of integrated pest management practices are preserving, or restoring, the natural balance between pest & prey in the landscape.

Lady bug feeding on a canker work.

Another thing to keep in mind; organic is not a synonym for safe!  There are Organic Materials Review Institute-approved pyrethins that will kill most all arthropods that are exposed to the product.  Meanwhile, there are completely man-made synthetic products that will effectively control the target pest, while preserving beneficial insects.  When developing a pest management strategy, it is imperative to research active ingredients, modes of action, and persistence in the environment.  Read the labels.  Ask questions of the product developers and your local extension.  Those people are great resources, and are there to help.

The Scourge of Imidicloprid

If you're like me, then while your wife is looking at power tools at Home Depot, Lowes, or wherever, you are looking at the active ingredients on pesticides in the garden aisle.  Which means you have probably noticed that many general purpose over the counter insecticides are now imidacloporid based.

As an industry, we have relied on imidacloprid, Merit in its most popular form, for more than a decade.  Applied properly it is a great product.  It is in the neonicotinoid family of chemicals, and its mode of action is kind of neat.  The chemical interferes with an insects nervous system which results in death. Imidacloprid can be applied as a foliar spray, soil application, or directly injected into the trunk.  It is nontoxic to mammals, has a long residual, and can be quite effective.

However there are some things we need to consider when using this pesticide.  Studies have shown that with repeated use the molecule can make its way into the flowers of plants.  For trees and shrubs that are not wind pollinated this exposes pollinators to the product, and may lead to civilian casualties in the war against plant pests.

The other issue is pest resistance to imidacloprid.  In some areas imidacloprid has been so heavily used that it is no longer effective against targeted pests.  With imidaclolprid now being readily available to the public at large, and continued reliance on the chemical in many professional PHC programs, we may only assume that this pest tolerance will grow.

There are few 'silver bullets' in pest management.  Product/chemical diversity is an important part of an IPM program.  Imidacloprid may still be part of your chemical arsenal  but pest monitoring and investigating different products for use on target pests should be on the forefront.

The molecule