PREDATORY AND PARASITIC INSECTS (The good guys!)

Predatory insects, mites, and molluscs destroy garden pests.  Some of these insects have large mouthparts that allow them to tear up and devour their prey.  Others have piercing mouth parts to suck the bodily fluids from other insects.  Predators include antlions, dragonflies, a few true bugs, and a number of beetles:  blister beetles, carrion beetles, checkered beetles,fireflies, ground beetles, ground beetles, ladybugs, net-winged beetles, soft-winged beetles, soldier beetles, and tiger beetles.  You can often identify predacious beetles by looking at them.  If a beetle's jaws are short and chunky, it is a plant-eater.  If the jaws are long and pointed with sharp cutting edges, it eats other insects.

Parasitic insects deposit their eggs on or in other insects.  Many have an egglaying device called an ovipositor that allows them to pierce the bodies of other insects to lay eggs.  When the eggs hatch, the larvae feed inside the victim's body.  Some of these parasitic insects lay their eggs in a number of host species, but others attack only one.

The most popular commercially availabe parasite is the trichogramma wasp.  It lays eggs in more than 200 harmful species. There are other wasps (some are called flies) that are useful in controlling garden pests--aphid wasps, braconid wasps, ichneumon flies, and pelecinid wasps, to name a few.

Here are other important benefical insects you can obtain commercially.

The larvae of the green lacewing eats aphids, mealybugs, and scale.  Once introduced into the garden as eggs, they hatch in a few days and feed for about three weeks, then pupate  and emerge as adults.  Adults feed on the honeydew that aphids excrete. 

Ladybugs eat 2 1/2 times their weight each day in aphids, mealybugs, moth eggs and spider mites.  The larvae also consume a number of insects.  Ladybugs are probably the most popular of all benefical insects. 

The mealybug destroyer is a member of the ladybug family that prefers mealybugs.  The larvae consume aphids as well.

Parasitic nematodes attack borers and soilborne grubs. 

Of the parasitic wasps, Encarsia formosa attacks whitefly larvae, Aphytis melinus attacks red scale, and trichogramma spp. parasitize the eggs of cabbage worm, corn earworm, and other larval pests.

The praying mantis, consumes huge quantities of quantities of beetles, caterpillars, and grasshoppers.  The young eat aphids, flies, and other small insects.

Predatory mites feed ion plant-damaging spider mites.  They are most effective when a mixture of species is released. 

To encourage beneficial insects in your yard, grow pollen-rich flowers around the garden for them to feed on when pests aren't plentiful.  Strawflowers attract ladybugs, Goldenrod hosts more than 75 benefical species. 

You can also buy a yeast-sugar insect food sold as artifical nectar.  Spray it over the garden and yard.  Beneficial insects such as ladybugs and adult lacewings will feed on it, just as they do on honeydew secreted by pests or on flower nectar.  To make your own solution, combine equal parts of brewer's yeast and sugar with enough water to dissolve them completely.  Apply either solution with a hand-pump sprayer.

BACTERIAL CONTROLS

Some bacterial agents are extremely effective against insect pests.  Bacillus thurintgiensis, sold under the names Thuricide, Biotrol, Agritrol, and Dipel, produces a toxin that paralyzes the digestive systems of caterpillars, including cabbage loopers and tomato hornworms.  It does not harm birds, bees, pets, or humans.

Bacillus popillae, sold under the names Doom, Lapidemic, and Milky Spore Disease, controls Japanese beetle grubs.

Grasshopper spore (Nosema lowstae) contains a natural parasite that attacks grasshoppers.  This parasite takes some time to show results, but can be effective if used over several seasons.


BOTANICAL SPRAYS

Plants themselves are the source of some of the strongest insecticides around.

Pyrethrum is made from the dried and powdered flowers of Chrysanthemum cinerarifolium, a close relative of the garden chrysanthemum.  Pyrethrum is extremely effective against aphids, leafhoppers, leaf miners, and thrips.

Rotenone is an insecticide derived from the roots and stems of tropical shrubs and vines in the genera Derris and Lonchocarpus.  Rotenone acts on contact and is also a stomach poison.  It controls many sucking and chewing insects, including aphids, beetles, caterpillars, leafhoppers, and thrips.

Ryania is derived from the ground stems of Ryania speciosa, a tropical South American shrub.  It is especially effective against the European corn borer, as well as a variety of other insects.

Sabadilla, made from the seeds of a lilylike Mexican plant (Schoencaulon) is sold as a wettable powder.  It works as both a contact and a stomach poison against squash bugs.

PLANT DISEASES

Even with your best preventive efforts, you may encounter some diseases in your garden. 
Bacterial diseases:  Bacteria are one-celled microorganisms.  Most are benefical in your garden, but a few are harmful to vegetables.

Bacterial spots, soft rots, and wilts cause most of the problems.  Bacterial spot (or blight) may start as dark green spots or streaks on leaves and stems, later turning gray to red-brown.  The spots may drop out and leave ragged holes.

Bacterial soft rot may infect leaves, branches, and fruit.  The infected area is usually bordered by pale yellow or tan.  When the infection is advanced, it oozes a gelatinous fluid.

Bacterial wilt invades the water-conducting tubes of the plant.  If you slice the stem of an infected plant, it will ooze a gelatinous fluid.  Often, vigorous-looking plants infected with bacterial wilt simply dry up and wilt.  Bacterial wilt is often spread by insects.

Fungal diseases:  Eight types of fungus are found in the garden:  mildews, rusts, rots, cankers, scab, spots, wilts, and smuts.

There are two types of mildews, powdery and downy. Powdery mildew appears as white to light gray patches on the upper surface of leaves.  Downy mildew shows up as pale green or yellow areas on the upper surface, and as light gray or purple patches below. 

Rust appears as bright yellow, orange red, reddish-brown, or black blisters (pustules) on the underside of leaves.  Only occasionally will it kill vegetables.

Rot is not one disease but several.  Root decay may cause the roots to be mushy and spongy.  this is caused by either fungi or bacteria.  When seedlings rot, collapse, and die before or just afer emergence, it is called damping-off.  Rots can attack practially all vegetables.

Cankers are simply irregularly oval dead areas on stems. They are often sunken or swollen and are usually discolored.  Blackleg of cabbage is the most serious canker found in the garden.

Scab appears as roughened, crustlike raised or sunken areas on leaves, stems, fruit, roots, and tubers.  It is caused by a wide range of fungi and a few bacteria.

Fungal leaf spots vary in size, shape, and color.  The centers of the spots may fall out.  Anthracnose, black spot, and tar spot are a few of the named types of this disease.

Fungal wilt plugs up the vessels inside the plants.  Fusarium and verticillum wilts are caused by fungi.  Both start at the base of the stem and proceed upward.

Smuts and soot molds show up as a mass of sooty black spores.  Both look bad, but they cause little damage to most plants.  In Mexico corn smut is considered a delicacy.

Viral diseases:  Viral diseases appear as distortions of leaves, flowers, or fruits; as yellowing or streaking of leaves; and as stunted plants.  A few viruses that affect vegetables are aster yellows (yellow and stunted plants), curlytop (dwarfed plants with curled, bunched leaves), mosaic (leaves with mottled yellow or light green areas), ringspot (yellow or brown concentric rings), and yellows (uniformly yellow plants, may wilt and die).  Many viruses are spread by sucking insects such as aphids and leafhoppers.

Damage from all diseases can be minimized by rotating your vegetables, pulling and destroying infected plants, planting resistant varieties, and avoiding overhead watering when possible.  Rust damage can be minimized by destroying nearby weeds that show rust.

PROTECTION FROM ANIMALS

Dogs, cats, gophers, birds, and other animals can be a nuisance in the garden. 

Physical barriers are useful for preventing bird damge.  You can protect individual seedlins with paper caps.  Groups of plants can be surrounded by window screen cages.  Commerical netting will fit over the entire garden.  Fences can prevent most larger animals from entering the garden. 

Aromatic materials and plants can be used to repel many animals.  A number of manufacturers offer dog and cat repellents in both stick and aerosol form.  Strips of aluminum foil may scare off birds and small animals; scarecrows, rubber snakes and owl decoys are traditional gardener's allies.

The bain of our gardening experience are gophers.  There is nothing like going out to work in the garden and notice the tops of the vegetables are jiggling around, then disappear down the hole.  One after the other.  To solve that problem we used bird wire cut to fit to form a circle, 12-14" deep, 12" inches across.  Tie the ends together with wire.   Fill the hole with organic material mixed with soil and poof, the little nusiances can't get into the root area of any plant.  The following year, simply scoop out the previous year's dirt, mix up a new batch and fill the hole.  This solved our problem forever.