The Garden Sampler

A Newsletter for Hardy Northern Gardeners
PO Box 7, Peru, VT 05152

Organic Techniques:

Pest Control Arsenal


In our pest control arsenals, we should have a number of tricks up our sleeves. Always start with the method that is the least harmful to people, beneficial insects, birds, and fish, and other critters. This is often hand picking, and if you only have a small infestation, this is usually quite effective. If hand picking doesn't work, perhaps one of the following home and commercial remedies may help. Always use any spray judiciously, and if you haven't tried it on a particular plant before, do a test area first and wait a day to see if there is an adverse reaction. Rugosa roses, for example, do not like anything sprayed on their leaves! Also, remember that organic does not mean it is harmless. Read the directions and cautions carefully and follow them to the letter!

Insecticidal soap

One of the most useful sprays in the garden. The commercial varieties work slightly better than the homemade version of a tablespoon of dish washing liquid in a quart of water. It must be reapplied at least once a week, more if there is a hard rain or a heavy infestation. This is a great control on all types of aphids and whitefly. (Before trying the soap on aphids, however, try using a forceful spray of plain water from your hose. Often this controls the problem without anything else!).

Combination spray

A homemade, all-purpose remedy that works on aphids and many leaf-eating pests. Combine 10 cloves of garlic and a small onion in your food processor or blender. Add a teaspoon of cayenne pepper and a quart of warm water. Mix well and set aside overnight. Strain through muslin or a very fine mesh strainer. Add a teaspoon of dish washing liquid and you are all set to go. Put in a spray bottle, and use it when you have an infestation every five days or so, more often if it rains. Use in two to three weeks, stored in the refrigerator.

Baking Soda Spray

A simple solution of one teaspoon baking soda to a quart of water should always be mixed and ready for action in an organic garden. Many scientific studies have demonstrated its effectiveness in preventing many fungal diseases, such as black spot on roses and powdery mildew on phlox. It works best as a preventative, so if you've had trouble in the past start spraying at weekly intervals to prevent the problem. To make the spray cling to the plants longer, add a teaspoon of dish washing liquid.

Horticultural oil

The new horticultural oil sprays are highly refined to remove any compounds that could damage plant leaves. They are effective in controlling many types of insects such as aphids, leaf miners, caterpillars, beetles, and mealy bugs. New research also suggests that when combined with baking soda, it makes an even more effective treatment for black spot on roses and powdery mildew. Try adding a teaspoon of the oil to your baking soda spray if you have a severe problem.

Some gardeners report success using cooking oil in place of the petroleum-based products.

Alcohol spray

If you have had problems with mealy bugs or scales, a spray of one cup of alcohol to a quart of water may help. Be careful, however, and do your test first. Wait two days to see if there is a reaction. Better yet, dip a cotton swab in the alcohol full strength and apply directly to the scales or mealy bugs.

Bug Juice

It sounds really disgusting, but an old-time remedy for pests such as the Colorado potato beetle and cabbage loopers is to make a spray from the dead bugs themselves.

No one is quite sure how it works, but the gardener may be helping to spread pest-specific diseases throughout the garden. Or, the odor may attract beneficial insects. One word of caution, don't use your family's kitchen equipment to mix up the concoction unless you sterilize it after in the dishwasher; the U.S. Environmental Protection Agency apparently believes the juice might contain pathogens that are harmful to humans as well.

Compost Tea

A compost tea is made by steeping a gallon of compost for three days in a cheesecloth bag in five gallons of water. Strain well, and use as a spray to prevent fungal diseases. It may be effective on the fungal diseases that attack tomatoes, so it's worth a try.


This product is an extract from a tropical tree, and it seems to work in several ways against a variety of insects. It is a stomach poison, a contact poison, growth retardant, and a repellent all in one. Although it has not been used in this area of the world for very long, it is a standard in India and some African countries. It seems to be effective on just about everything from aphids to Colorado potato beetles and Mexican bean beetles and mites. It appears that the substance is safe for mammals and beneficial insects such as parasitic wasps, but read label carefully and use according to directions.


Some popular insect-specific controls are the various strains of Bacillus thuringiensis, or Bt. This bacteria attacks caterpillars, and nothing else. Although it has proven to be quite effective, some research suggests that some insects can develop a resistance to the bacteria so it should be used only as a last resort.

Bt comes in many forms from a wide variety of companies.

Diatomaceous Earth

Although it feels soft to our touch, the granules of this abrasive powder can quickly destroy soft-bodied insects such as aphids and slugs. Dust on leaves (please wear a mask when applying any type of dust), or form a barrier around your hostas with this material.

It is not insect specific, however, and can kill ladybugs as well. Also, you will have to replenish it after a rain.

Additional comments

Throughout New England, gardens centers carry milky spore as a biological control for the Japanese beetle grubs. In most of our region, your results will be disappointing as the soil temperatures simply do not stay warm enough, long enough for this bacteria to take hold. Also, our acidic soils may interfere with its growth. The entomopathogenic nematodes currently under study may be more promising in Northern gardens.

We also continue to see the old "organic" standards rotenone, sabadilla, and pyrethrins fill the shelves of garden shops in the spring. These grandfathered products would most likely have great difficulty in getting any type of federal approval today, as they are toxic to fish, mammals, and birds. They have serious side effects, including nervous system damage and possible carcinogenic properties. Because they carry the label "organic" they are often used with less care than some of the materials that are perceived to be stronger.

Avoid these products, even as last resort.

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Copyright 1997 by The Garden Sampler, PO Box 7, Peru, VT 05152 . All rights reserved.

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Last updated Feburary 1997