Expert: Long Island Gardener - 7/2/2010

Question
What is the best solution to get rid of aphids and whiteflies (and prevent them from returning)on my potted petunias?

Answer
One-stop shopping is becoming easier thanks to the Green Wave sweeping across the planet.

For infestations solutions from A to W, try Colorado-based Golden Harvest Organics:

www.ghorganics.com

For Aphid control, they sell 1600 X-Clude, Diatomaceous Earth, and Garden Dust Insecticide/Fungicide.  Among their solutions to Aphid attacks: 'A soap spray can be used to strip them of their protective wax coating, dehydrating them. Mix 1 tablespoon of Castile soap to 1 gallon of water, spray.'

Gardener's Supply Company website provides a menu of plant and pest problems and their organic solutions.  Here's their Aphids control pitch:

http://www.gardeners.com/on/demandware.store/Sites-Gardeners-Site/default/Page-S...

and here's their Whitefly pitch:

www.gardeners.com/Whitefly/5321,default,pg.html

There are many others listed.

Greenhouse Whiteflies (Trialeurodes vaporariorum) and Silverleaf Whiteflies (Bemisia argentifolii), they note, 'are not true flies as they are relatives of Mealybugs, Scales and Aphids.'  Your choice of weapon depends on where you live.

One of their more exotic Whitefly predators is Encarsia formosa, which they describe as 'a tiny golden wasp which is a parasitoid, meaning it actually kills its host.'  This is the perfect time to use E. formosa against any Whitefly, but it works best on the Greenhouse Whitefly.  And you can buy it from them.

Green Methods is another purveyor of friendly insects:

greenmethods.com/site/biocontrols/encarsia

For controlling 'other Whitefly speciest' that are only modestly affected by E. formosa, Green Methods can sell you Eretmocerus eremicus, touted as 'our newer E. formosa Nile Delta strain.'

For IPM to work to your satisfaction, you may have to pay attention to needs of the beneficial insects.

Organic insect sprays are another option, and they come without that inconvenience.  But sprays don't spend their entire life cycle HUNTING DOWN bugs that bug you.   Green Methods describes the conditions those helpful insects need to thrive.  To wit: 'In order for E. formosa to be effective, the release site must be brightly lit, with a minimum of 650 footcandles.  Photoperiod or day-length doesn’t seem to be of importance, just intensity.'

Temperature also matters, as do other factors. Dealing with the demands of insect allies will achieve your best case scenario.

There are other environmentally responsible ways to repel these pests. Garlic sprays, for example, which you can make in the kitchen.

Still, having used IPM so successfully against some truly wicked bugs, I hope you will give this technique the old college try.  It could not be easier than this, nor more effective.  Just don't combine them with organic insecticides -- Insecticidal Soap, for instance, which will wipe out your Whitefly/Aphids predators.  Plantings of host plants to make your outdoor spaces friendly to these insect allies will keep them coming back year after year.

THE LONG ISLAND GARDENER