Early detection and treatment

of pests means a healthier

growing environment.

In your garden

Pest management can be one of the greatest challenges to

the home gardener. Yard pests include weeds, insects,

diseases, and some species of wildlife. Weeds are plants

that are growing out of place. Insect pests include an enormous

number of species from tiny thrips, that are nearly invisible to

the naked eye, to the large larvae of the tomato hornworm.

Diseases are caused by fungi, bacteria, viruses, and other

organisms, some of which are only now being classified. Poor

plant nutrition and misuse of pesticides also can cause injury to

plants. Slugs, mites, and many species of wildlife such as rabbits,

deer, and crows can be extremely destructive.

Identify the problem

Careful identification of the problem is essential before control

practices can be used. Some insect damage may appear to be

a disease, especially if no visible insects are present. Nutrient

problems may also mimic diseases. Herbicide damage resulting

from misapplication of chemicals also can be mistaken for other

problems.

What to look for

Insects and mites All insects have six legs, but other than that

they are extremely variable. They include such organisms as

beetles, flies, bees, ants, moths, and butterflies. Mites and spiders

have eight legs– they are not insects. But for the purposes of this

article, they will be considered as insects.

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Pest Management BARD

Insects damage plants in several ways. The most visible damage is

chewed plant leaves and flowers. Many pests are visible and can be

readily identified, including the Japanese beetle, Colorado potato

beetle, and numerous species of caterpillars such as tent caterpillars

and tomato hornworms. Other chewing insects, however, such as

cutworms (which are caterpillars) come out at night to eat, and burrow

into the soil during the day. These are much harder to identify but

should be considered if young plants seem to disappear overnight

or are found cut off at ground level. Sucking insects are extremely

common and can be very damaging. These insects insert their mouth

parts into the plant tissues and suck out the plant juices. They also

may carry diseases that they spread from plant to plant as they move

about the yard. You may suspect that these insects are present if you

notice misshapen plant leaves or flower petals. Often the younger leaves

will appear curled or puckered. Flowers developing from the buds may

only partially develop. Look on the underside of the leaves as that is

where many species tend to gather. Common sucking insects include l

eafhoppers, aphids, mealy bugs, thrips and mites. Other insects cause

damage by boring into stems, fruits, and leaves. They may disrupt the

plant’s ability to transport water. They also create opportunities for

disease organisms to attack the plants. You may suspect the presence

of boring insects if you see small accumulations of sawdust like material

on plant stems or fruits. Common examples of boring insects include

squash vine borers and corn borers.

Diseases

Plant disease identification is extremely difficult. In some cases,

only laboratory analysis can conclusively identify diseases. Disease

organisms injure plants in several ways. Some attack leaf surfaces

and limit the plant’s ability to carry on photosynthesis. Other organisms

produce substances that clog plant tissues that transport water and

nutrients. Other disease organisms produce toxins that kill the plant or

replace plant tissue with their own. Symptoms associated with plant

diseases may include the presence of mushroom-like growths on trunks

of trees; leaves with a grayish mildewy appearance; spots on leaves,

flowers, and fruits; sudden wilting or death of a plant or branch; sap

exuding from branches or trunks of trees; and stunted growth.

Misapplication of pesticides and nutrients, air pollutants, and other

environmental conditions such as flooding and freezing can also mimic

some disease problems. Yellowing or reddening of leaves and stunted

growth may indicate a nutritional problem.At first glance, blossom end

rot of tomato, in which the bottom of the tomato turns black, might

appear to be a disease caused by some pathogen. It is actually caused

by the plant’s inability to take up calcium quickly enough during periods

of rapid growth. Prevent this problem with adequate moisture–adding

more calcium is of no benefit! Leaf curling or misshapen growth may be

a result of herbicide application.

Pest management practices

Preventing pests should be your first goal. But it’s unlikely you will be

able to avoid all pest problems, since some plant seeds and disease

organisms lay dormant in the soil for years. Diseases need three elements

to become established: the disease organism, a susceptible species,

and the proper environmental conditions. Some disease organisms can

live in the soil for years; other organisms are carried in infected plant

material that falls to the ground. Some disease organisms are carried

by insects. Good sanitation will help limit some problems. Planting

resistant varieties of plants prevents many diseases. Rotating annual

crops in a garden also prevents some diseases. You will likely have the

most opportunity to alter the environment in favor of the plant and not

the disease. Healthy, vigorous garden plants have a higher resistance

to pests. Plants that have adequate, but not excessive, nutrients are

better able to resist attacks from both diseases and insects. Excessive

rates of nitrogen often result in extremely succulent vegetative growth

and can make plants more susceptible to insect and disease problems,

as well as decrease their winter hardiness. Proper watering and spacing

of plants limits the spread of some diseases. Some disease species

require free standing water in which to spread, while other species just

need high humidity. Proper spacing provides good aeration around plants.

Trickle irrigation where water is applied to the soil and not the plant

leaves may be helpful. Barriers may be effective to exclude some pests.

Mulching is effective against weeds. Fences can limit damage from

rabbits. Row covers may prevent insect damage on young vegetable

plants. Netting can be applied to small fruit trees and berries to limit

damage from birds.

Integrated Pest Management (IPM)

It is difficult, if not impossible, to prevent all pest problems every year.

If your best prevention efforts have not been entirely successful, you

may need to use some control methods. Integrated Pest Management

(IPM) relies on several techniques to keep pests at acceptable population

levels without excessive use of chemical controls. The basic principles

of IPM include monitoring (scouting), determining tolerable injury levels

(thresholds), and applying appropriate strategies and tactics. Unlike

other methods of pest control where pesticides are applied on a rigid

schedule, IPM applies only those controls that are needed, when

they are needed, to control pests that will cause more than a tolerable

level of damage to the plant. Monitoring is essential for a successful

IPM program. Check your plants regularly. Look for signs of damage

from insects and diseases as well as indications of adequate fertility

and moisture. Early identification of potential problems is essential.

There are thousands of insects in the garden, many of which are

harmless or even beneficial. Proper identification is needed before

control strategies can be adopted. It is important to recognize the

different stages of insect development for several reasons.

The caterpillar eating your plants may be the larvae of the butterfly

you were trying to attract. The small larvae with six spots on its

back is probably the young of the ladybug, a very beneficial insect.

Some control practices are most effective on young insects. Different

stages may also be more damaging than others. This is where the

concept of thresholds comes in. The economic threshold is the point

where the damage caused by the pest exceeds the cost of control.

In a home garden, this can be difficult to determine. What you are

growing and how you intend to use it will determine how much damage

you are willing to tolerate. Remember that larger plants, especially those

close to harvest, can tolerate more damage than a tiny seedling. A few

flea beetles on a radish seedling may warrant control whereas numerous

Japanese beetles eating the leaves of beans close to harvest may not.

If the threshold level for control has been exceeded, you may need to

employ control strategies. Strategies can be discussed with the

Cooperative Extension Service, garden centers, or nurseries.

Control strategies

Mechanical/physical controls

Insects–

Many insects can be removed by hand. This method is preferable if a

few, large insects are causing the problem. Simply remove the insect

from the plant and drop it into a container of soapy water or vegetable

oil. Caution: some insects have spines or excrete oily substances

that can cause injury to humans. Use caution when handling unfamiliar

insects. Wear gloves or remove insects with tweezers. Many insects can

be removed from plants by spraying water from a hose or sprayer. Small

vacuums can be used to suck up insects. Traps can be used effectively

for some insects. These come in a variety of styles depending on the

insect to be caught. Many traps rely on the use of pheromones–naturally

occurring chemicals produced by the insects and used to attract the

opposite sex during mating. They are extremely specific for each species

and, therefore, will not harm beneficial species. One caution with traps is

that they may actually draw more insects into your yard. You should

not place them directly in the garden. Other traps are more generic

and will attract numerous species. These include such things as yellow

and blue sticky cards. Different insects are attracted to different colors.

Sticky cards can also be used effectively to monitor insect pests.

Weeds–

Hoeing, pulling, and mulching are the most effective physical control

methods for weeds. Weeding is most important while plants are small.

Well established plants can often tolerate competition from weeds.

Diseases–

Removal of diseased material limits the spread of some diseases. Clean

up litter dropped from diseased plants. Prune diseased branches on

trees and shrubs. When pruning diseased trees and shrubs, disinfect

your pruners between cuts with a solution of chlorine bleach to avoid

spreading the disease from plant to plant. Control insects known to

spread plant diseases.

Other pests–

Fences, netting, and tree trunk guards can be extremely successful

in limiting damage from small mammals and birds. Numerous traps

are also available to catch or kill some animals. (Caution: In many states

it is illegal to move wildlife, including squirrels. Traps may also catch

animals other than the ones targeted. Check local regulations before

trapping.)

Diatomaceous earth, a powder-like dust made of tiny marine

organisms called diatoms, can be used to reduce damage from

soft-bodied insects and slugs. Spread this material on the soil–

it is sharp and cuts or irritates these soft organisms. It is harmless

to other organisms. Shallow dishes of beer can be used to trap slugs.

Biological controls

Biological controls are nature’s way of regulating populations. Biological

controls rely on predators and parasites to keep organisms under control.

Many of our present pest problems result from the loss of predator

species. Other biological controls include birds and bats that eat insects.

A single bat can eat up to 600 mosquitoes an hour. Many bird species eat

insect pests on trees and in the garden. Bacillus thuringiensis (Bt) is a

bacteria that specifically attacks larvae of some insect pests including

white grubs in the lawn and Japanese beetles. This bacteria is harmless

to desirable species.

Chemical controls

When using chemical controls, be very careful with pesticides. Most

common pesticides are broad spectrum in that they kill a wide variety

of organisms. Spray applications of insecticides are likely to kill

numerous beneficial insects as well as the pests. Herbicides applied

to weed species may drift in the wind or vaporize in the heat of the day

and injure non-targeted plants. Runoff of pesticides can pollute water.

Many pesticides are toxic to humans as well as pets and small animals

that may enter your yard. Some common, non-toxic household

substances are as effective as many more toxic compounds. A few

drops of dishwashing detergent mixed with water and sprayed on plants

is extremely effective in controlling many soft-bodied insects such as

aphids and whiteflies. Crushed garlic mixed with water may control

certain insects. A baking soda solution has been shown to help control

some fungal diseases on roses.

When using pesticides, follow label directions carefully. Altering the

rate of application or increasing the frequency of application can injure

desirable plant and animal species. Spot applications of the pesticide to

the targeted pest can reduce the amount used and help reduce the

risk of injury to non-targeted species. Do not apply on windy days.

Read the label for information on other environmental conditions such

as temperature and rain that may influence the pesticide’s effectiveness.

Be aware that many so-called “organic” pesticides may be just astoxic as

the synthetic or chemical products.