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Master Gardener Column: Organic pest management

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Master Gardener Column: Organic pest management

Arlene Hamilton
Organic Pest Management

More than forty years ago, Rachel Carson in her book “Silent Spring opened our eyes to the fact that we have endangered the earth and ourselves with the use of chemicals. 

Today the hot phrase is “Going Green” where many of us try to follow organic practices such as composting, mulching, soil and water conservation. But when it comes to pests the task can seem overwhelming. 

Pesticides, even organic ones are not always the best answer to pest control. The use of herbicides and pesticides, even organic ones make no distinction between good bugs and bad bugs. 

Long term use can have many negative impacts, including suppression of the bacteria and organisms that break down the food that feed our plants. Long term use can also lead to pollution of our waterways.

Certain plants can encourage biodiversity and a healthy population of beneficial insects in your garden. Integrated Pest Management (IPM) relies on the use of plants known to attract beneficial insects that prey on pests that damage plants and crops. 

The three ‘Ps’ of beneficial insects are pollinators, predators and parasites. Pollinators, such as honeybees, fertilize flowers which increases food production. Predators, such as lady bugs, consume pests as food. 

Parasites use pests as nurseries for their young. All three of these ‘Ps’ will be actively working in a healthy, biodiverse garden.

Here are a few plants that will help manage the pests that invade your garden.

Chives, garlic, leek, onion, and shallot are excellent protective companions for roses and will help protect from mildew black spot, aphids and many other pests. Onion repels cabbage butterflies. 

Chives and garlic are good for fruit trees and tomatoes. To make an insect repellent tea grind three hot peppers, four large onions, and one whole bulb of garlic together. 

Cover with water and allow to stand overnight. The following day strain the mixture through a fine sieve.

Add enough water to make a gallon, add 2 teaspoons of canola oil. 

Spray on infected plants thoroughly covering all sides. Do not use during the heat of the day as the oil may burn the plants; and don’t get any in your eyes as the peppers will irritate.

Chamomile tea can be made by soaking the dried flowers for a day or two in water then spraying over young plants in the greenhouse to prevent damping-off.

Chrysanthemums are beneficial to strawberry plants and are the source of pyrethrum, a direct contact insecticidal effective against soft bodied insects.

Dandelions are beneficial because of their long taproots which transport minerals, especially calcium, upwards from deeper soil layers and deposit them nearer the surface. They therefore return to the soil minerals that have been lost through seeping downward.

Asters, cosmos, coreopsis, marigolds and larkspur are good to plant throughout the garden.

Nasturtium planted with squash will keep away squash bugs, will repel the whitefly in the greenhouse, and when planted near broccoli will keep down aphids. 

They are beneficial to potatoes, radishes, cucurbits, and members of the cabbage family.

Peppers (capsicum) are effective in protecting plants from viruses. Sprays were found effective against tobacco mosaic virus, potato virus and several others.

Petunias protect beans against beetles.

Sunflowers are a soil improver and a companion for corn and cucumbers. They are also a trap plant, luring insects away from more valuable plants.

Sage, mint, thyme, rosemary, tansy, wormwood and rue make excellent insect repelling teas. 

Use 2 cups of fresh leaves in 3 cups boiling water. Steep for 2 -3 hours, strain, add 1 teaspoon liquid non- detergent soap. Dilute with 2 cups water and spray infected plant thoroughly.

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