11. Organic Pest Control in Vegetable Gardens.

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Organic pest control comes in many forms. Many people assume that you need to buy something toxic in order to kill all the bugs and have better vegetables. There are so many other good choices that are better for the garden and healthier for you.

 

Photo of chewed off bean seedlings.Photo of long-legged fly on bean seedling.

As you can see in the above photos, something has eaten my beans plants. The angle of the cut off stems suggests rabbits may be the culprits, but I’m still investigating. There is still the issue of the insect bites in the leaves still remaining. If you click on the second picture to enlarge it, you can see an insect at the top of the leaf on the right. This is not the culprit. This is a Long-legged Fly, one of the good bugs. They eat aphids, thrips and spider mites. He (or she) is one of many for your first defense in organic pest control.

Please, protect the bees.

Most pesticides, whether organic or not, will kill almost any insect it comes in contact with. That includes beneficial insects like bees. Pollination by bees accounts for two thirds of the fruits and vegetables grown and we need to help protect them from overuse of pesticides. Only use what is necessary, use organic products, only spray on the intended victims and never spray on open flowers.

Common garden insect pests

Tomato hornworm

In the home garden, some bugs are easy to just pick off and crush, such as the tomato hornworm during any of its stages; the five-spotted hawk moth, the larva or caterpillar, large greenish-white eggs on the underside of leaves and the pupae which is found in the soil. If you see a tomato hornworm covered in white eggs leave it alone, as the Braconid wasp has laid its eggs on it and is using it as a host. (They also lay their eggs on cabbage worms and other soft-bodied insect pests.) When these eggs hatch you will have a small army of pest eaters. Below, life stages of the hornworm, Braconid wasp and wasp eggs attached to a tomato hornworm.

Life stages of the tomato hornworm.

Braconid wasp       Braconid wasp and eggs.

Mexican bean beetle and Striped cucumber beetle

The Mexican bean beetle is another bad one that can seriously damage or kill bean plants. The Striped cucumber beetle attacks Cucurbits: cucumbers, squash, zucchini, pumpkins and gourds. For both, check undersides of leaves for yellow-orange egg clusters, if you see clusters, remove the leaf and crush them. Hand pick adults and pupae, then crush or drown in soapy water. Below are the life cycle of the Mexican bean beetle, damage from bean beetles and Striped cucumber beetle.

Mexican bean beetle life cycle.       Leaves with beetle damage       Striped cucumber beetle

Aphids

Aphids are tiny insects that suck juices out of leaves and stems, and excrete part of the sugars they consume. They can be white, black, brown, gray, yellow, light green, or pink depending on the species. They can, if left unchecked, severely damage plants. If you see a lot of ants on a plant, check for aphids, usually on new growth, and undersides of leaves. Spray with a hose to remove them, crush them, or spray the plant with Insecticidal Soap or Neem oil. Using yellow sticky traps will also help. Lady bugs and their larvae love to eat aphids and can consume 50 to 60 aphids per day. Attract them by planting pollen plants such as cosmos, dill, fennel, marigold, yarrow and chives. Local ladybugs will also eat whitefly, thrips and other tiny insects. Below, green and black aphids, ladybug and ladybug larva eating aphids.

Light green aphids on a stem. Black aphids on stem. Lady bug eating aphids/ Lady bug larva eating aphids.

Squash Vine Borers

Squash Vine Borers attack squash, zucchini, gourds and pumpkins. When the adult clearwing moths emerge in early to midsummer, they lay eggs singly or in small groups at the base of stems. The eggs will hatch within 1 to 2 weeks after being laid and the larvae will then bore into stems to feed for about 2 to 4 weeks. They bore just above the soil level. This causes the plant to wilt and eventually die do to lack of water uptake.

Sprinkle diatomaceous earth and black pepper around the stalks when the squash vines are small, and reapply frequently, specially after rain or watering. Wrap the lower stem with aluminum foil or strips of nylon stockings to prevent entry. If you see small holes in the stem near the soil line with what looks like sawdust (called frass) they are already inside. Using a very sharp and clean knife, cut a small vertical slit starting at the hole and remove any larvae. Bury the slit area in damp soil to promote root growth. Below, adult squash vine borer, eggs on underside of leaf (can also be along stems), slitting stem to remove larvae and larva in a stem.

Adult squash vine borer. Squash vine borer eggs under leaf. Cutting quash stem to remove borer. Open stem with borer inside.

Good Bugs

Ladybug:

preys on aphids, whitefly, mites, fleas and the Colorado potato beetle. Attract with cosmos, dill, fennel, marigold, yarrow and chives. Below, ladybug and larva.

ladybug.  Lady bug larva eating aphids.

Praying Mantis:

eats caterpillars, moths, beetles, crickets and more. Attract with cosmos, marigold, dill and tall grasses. Below, mantis and egg case.

Praying mantis.  mantis egg case on branch.

Spiders:

most anything that gets caught in their web, including aphids, caterpillars, grasshoppers, and fruit flies. Below, the common garden spider.

Common garden spider.

Ground Beetles:

slugs, caterpillars, Colorado potato beetles, cutworms. Attract with clover, amaranthus and evening primrose. They are usually only active at night.

 Ground beetle
Braconid Wasps:

prey on hornworms, caterpillars and aphids. They are attracted by yarrow, parsley, dill and lemon balm.

Braconid wasp

Damsel Bugs:

caterpillars, mites, aphids, potato beetles, cabbage worms. Attract with caraway, spearmint, goldenrod, fennel and alfalfa.

Damsel bug.

Green Lacewings:

prey on aphids, whitefly, leafhopper, mealybugs and caterpillars of pest moths. Attract with dill, coriander, golden marguerite, dandelion and angelica. The larva actually kills most pests. Below, larva, adult and eggs.

Green lacewing larva.  Adult green lacewing.  Green lacewing eggs.

Minute Pirate Bugs:

preys on spider mites, insect eggs, caterpillars, aphids and thrips. Attract with fennel, spearmint, goldenrod, caraway and alfalfa. The adult and larvae both feed on insects.

Minute pirate bug.  Minute pirate bug with penny for comparison. It is the size of Lincoln's nose!

Soldier Beetles:

preys on aphids, small soft bodied insects and grasshopper eggs. Attract with goldenrod, marigold and zinnia.

Soldier beetle.

Tachinid Flies:

prey on gypsy moths, Japanese beetles, cutworms and squash bugs. Attract with carrots, dill, cilantro and coriander. They lay their eggs onto the host insect or nearby foliage.

Tachinid fly.

Hoverflies:

prey on aphids, scale insects and caterpillars. Attract with yarrow, dill and statice. The larvae eat the pests, the adults eat pollen. Below, hoverfly and hoverfly larva eating an aphid.

hoverfly.  hoverfly larva.

 

Mealybug Ladybug or Mealybug Destroyer:

preys on mealybugs. Attract with fennel, dill, sunflowers, angelica and goldenrod.

mealybug destroyer.

Barriers

Sometimes, something as simple as a floating row cover (a lightweight woven cloth material) will help immensely. Bend chicken wire into a hoop shape over plants (tall enough to allow for growth) and cover it with row cover. Make sure to anchor it down and cover the plants completely, don’t forget the sides. This works well for cabbage moths.

Plant collars can help with slugs and cutworms. My favorite is to cut both ends off a soup can, slip it over a seedling and push it an inch or two into the ground when you transplant it. You can also make these out of cardboard.

Commercial Organic Pest Control

Neem oil

A naturally occurring pesticide found in seeds from the neem tree. It reduces insect feeding and acts as a repellent. It also interferes with insect hormone systems, making it harder for insects to grow and lay eggs. Other components of neem oil kill insects by hindering their ability to feed. Reapply as recommended on the label.  (National Pesticide Information Center)

Diatomaceous Earth 

DE is made from the fossilized remains of tiny, aquatic organisms called diatoms. Their skeletons are made of a natural substance called silica. Silica is very common in nature and makes up 26% of the earth’s crust by weight. It is not poisonous; it does not have to be eaten in order to be effective. Diatomaceous earth causes insects to dry out and die by absorbing the oils and fats from the cuticle of the insect’s exoskeleton. Its sharp edges are abrasive, speeding up the process. It remains effective as long as it is kept dry and undisturbed. You need to reapply after rain or watering. (National Pesticide Information Center)

Organic insecticidal soap

can help control populations of a variety of insects, including: Aphids, Earwigs, Mites, Mealybugs, Grasshoppers, Adelgids, Harlequin bugs, Leafhoppers, Scale insects, Jumping plant lice, Spider mites, Squash bugs, Thrips, Whiteflies, Plant bugs, Psyllids, and Sawfly larvae. Insecticide soaps work by breaking down the outer shell of the insect. It is a contact solution, meaning if an insect lands on the plant after the soap solution has dried, the insect will not be affected. (National Pesticide Information Center)

Pyrethrin: 

This natural insecticide is derived from the pyrethrum plant (Chrysanthemum cinerariaefolium). Along with pyrethroid, its synthetic substitute, it is highly effective against a wide range of insects. Each should be used according to manufacturer’s directions. (Mother Earth News)

Bt:

Bacillus thuringiensis, often abbreviated as Bt, is a naturally-occurring bacteria that makes pests sick when they eat it. There are two strains commonly used as natural pesticides. Bacillus thuringiensis kurstaki (Btk) gives excellent control of leaf-eating caterpillars such as cabbage worms and tomato hornworms, but has no activity against insects that do not eat treated leaves. After the insects eat the bacteria, their guts rupture and they die. Bt is therefore one of the safest natural pesticides you can use in terms of controlling caterpillar pests of vegetables or fruits without harming beneficial insects. Bacillus thuringiensis israelensis (Bti) can be useful in controlling fungus gnats in greenhouses or houseplants, or for preventing mosquito problems in standing water that cannot be drained or controlled with fish. (Mother Earth News)

Always follow label directions on all products.

 

 Home made Organic Pest Control

Garlic and Red-Pepper Spray:

Grind up a large bulb of garlic (or a large onion). Add one tablespoon of ground cayenne pepper and one quart of water. Steep for one hour. Strain liquid into a sprayer or watering can and refrigerate remainder in a tightly covered jar. It will be potent for several weeks, and is effective on all kinds of chewing and sucking insects. (from Mother Earth News)

Hot Pepper: 

To discourage cats, dogs, many insect pests, and snails from munching, dust powdered hot pepper or a spray of hot pepper sauce on plants.

Beer:
Set a clean tuna can into the soil so the top edge is just above soil level. Fill half full with beer. In the morning, dump out the beer and slugs you just caught. Refill as needed. If you are feeling creative, put a small roof (think canopy or umbrella) over your slug trap. It will prevent it from getting diluted with rain water and losing effectiveness.

Always try home made sprays, specially those with soap added, on a few leaves first. You don’t want to kill your plants while trying to kill the bugs.

 

 

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