In The Garden This Week: Organic Pest Control

While we are waiting for the heat to disperse (Is this Part of the Global Warming "myth?"), for those of you who missed our lecture last Saturday, here is a short summary of information on organic pest control.

Working on the URI Master Gardener Hotline (Mon-Thu 9-2, 1-800-448-1011) we often get a question like: "I have holes in the leaves of my vegetable/flower/tree leaves. What should I spray?" Our inquiries often start out like that. The first thing we ask, after identifying the plant is: "Do you know what is causing the holes?" The usual response to this is dead silence for a time and then we hear "Some bug!" 

The important thing in any situation like this is to fully try to identify the problem. Sometimes that is not easy on the telephone. It is sometimes difficult for the caller to explain the cause of the problem. Often the place to look for insects or their damage is on the UNDERSIDE of the leaves. There you will often find the culprit like the bright orange lily leaf beetle, an insect that does serious damage to your asiatic and oriental lilies. Sometimes you may also see thrips, whiteflies or flea beetles as well.

So what do we do? The nurseries and the "big box stores" have shelves and shelves of pesticides, some organic and some chemical (and toxic to you and to good insects). You need to read the microscopic print on the label to see what the contents of the product are. Always keep in mind there are chemicals in some pesticides that kill ALL insects, good and bad and some of them are not so good for you to inhale either.

So let's look at some of the organic (nontoxic to humans) ways to treat garden pests:

1. In the first place you can pick off the insects if they are large enough. A dish of soapy (dish detergent) water will take care of most of them.

2. Insecticidal soap-comes in a pump spray and it is good for aphids, thrips, whiteflies,and spidermites among others. It biodegrades rapidly so you need to apply it at weekly intervals until the pest disappears.

3. Bacillus Thuringiensis (Bt) is a bacterium which is a stomach poison for plant- eating caterpillars, cabbage worms and squash vine borers and others.

4. Neem oil is a fungicide that helps control fungi. Caution: It is toxic to bees so it should be applied in the late afternoon or evening when the bees are asleep.

5. Pyrethrin is good for soft-bodies insects and it is made from chrysanthemums. It is sometimes sold in combination with rotenone (which kills hard-bodied insects). This combination is especially good for disposing of lily leaf beetles and their larvae.

6. Diatomaceous Earth (DE) is mined from fossil shells which are ground into a powder. A circle of DE around your hostas will kill slugs.

7. Spinosad is also a bacterium. It controls fruit flies, caterpillars, thrips, leafminers and leaf beetles. It is also toxic to bees so use it cautiously. It is sometimes sold as "Conserve" or "Bulls-Eye"

8. Hot pepper spray (Capsaicin) is made from pepper plants and is formulated with a paraffin wax to make it stick. It is useful for soft-bodied insects.

These are a few of the major organic pesticides. There are others, and you can also do any of the following to control pests:

1. As mentioned, you can pick off the insects.

2. Sanitation-Clean up the plant debris under your plants. Insects love to hide there.

3. Rotate your crops from year to year if possible. Move them around so that plant-specific insects don't get too comfortable.

4. Trapping-You can plant trap crops to lure insects away from your favorite crops. For example, flea beetles love radishes so put the radishes near, but not right against your potatoes and they will attract the flea beetles.

So there you have a few suggestions on how to treat your flowers and vegetables organically. Most important: Read the labels on anything you spray on your plants, especially those vegetables that you are going to eat.

Enjoy your gardening and, in spite of the recent heat, make it fun, not work!

Don't forget our soil testing and gardening information kiosk every Sunday (rain or shine from noon till 2 at Paradise Valley Park next to the windmill (Paradise and Prospect Avenues) in Middletown. Bring samples of plant problems, photographs or bottled insects to us so we can enable you to solve all of your gardening problems.