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A plague of pests can make your garden no Eden

SHARE A plague of pests can make your garden no Eden

Ever since Adam and Eve left the Garden of Eden, pests have plagued us. The Book of Genesis explains, "Cursed is the ground for thy sake; in sorrow shalt thou eat of it all the days of thy life; Thorns also and thistles shall it bring forth to thee."

Add to the thorns and thistles myriad other weeds.

Then count the insects, the pathogenic diseases caused by different organisms, and those mishaps from the weather and other environmental problems.

Include rodents, birds and other animals, and it seems like we are lucky to get anything to grow in our gardens.

The biblical curse gets somewhat personal when you're fighting pests. I admit I have a hard time feeling "blessed" when pests are destroying my plants.

Pests destroy about one-third of the world's food supply annually. They attack our homes, pets and domestic animals, clothing, forests and almost anything else around us. They spread serious diseases to people, other animals and our desirable plants.

Pests discourage gardeners. No one wants to spend all the time and money to grow a garden and then have pests destroy it. Since pests are so widespread, numerous and diverse, controlling them is never easy. Successful control requires understanding the problems and how and when to intervene.

Because of space limitations, this column will cover strategy, not pest controls for specific pests. The advice is to control common, destructive pests that attack edible crops (meaning vegetables), tree fruits and berries. Controlling these successfully adds food to your table and makes gardening more enjoyable.

Getting started

Determining the best way to control pests is often difficult.

Start by diagnosing the problem correctly. It is confusing and difficult to tell what causes specific problems. If you do not know what the problem is, you cannot solve it.

There are great differences among garden pests. Controls for insects are very different from controls for diseases or nutritional problems. If you make the wrong diagnosis, you will spend considerable time and money treating the problem and, even worse, the plants might die because of an incorrect diagnosis.

Any diagnosis starts with identifying the plant. People call any tall evergreen a pine tree, but it could be a spruce, fir or juniper. These need different growing conditions and develop different problems.

If you took your pet into a veterinarian and were asked if it were a dog or cat, you would never let that person touch your pet. Yet plants are just as different as animals. If you cannot identify the plant, find out. You can never determine the way to solve the problem if you are treating the wrong type of plant.

Determine what is normal for that plant. Often gardeners think there is a problem but the plant is normal. Remember, most creatures in your garden are not causing problems, so determine if a problem exists before attempting control measures.

Finally, consider the economics of pest control. If pest problems are serious enough, rotate out of that plant until the pest subsides, change to a different crop or figure out a less expensive way of control. Chemicals are not the only answer. There are many biological, cultural, mechanical and other controls that will help reduce pest problems.


A weed is defined as a plant out of place. Whenever a plant interferes with the desirable plant for that area, it is a weed. Kentucky bluegrass is great in your lawn but will destroy your asparagus bed. Roses might be beautiful, but you certainly never want them in the berry patch.

Weeds are the most destructive pests of home gardens. Insects or disease might affect specific plants, but weeds interfere with all plants in your garden. They are often called the silent pests because they do not eat or kill the desirable plants.

For convenience, weeds are categorized as annuals that grow for one season, biennials that grow for two years, or perennials that grow for more than two seasons. Annual weeds can be prevented using pre-emergent herbicides.

Weeds are also divided botanically into grass or broad-leaved plants. This is important for some herbicide options.

Weeds propagate by seeds or by vegetative methods. They can produce tremendous numbers of seeds. For example, a single pigweed plant can produce more than 175,000 seeds in a single season.

Keep weeds from going to seed.

Cultivation is still one of the best methods of weed control in the home garden. Digging, pulling, tilling and hoeing are all ways to remove weeds from your garden and prevent them from going to seed.

Start when annual weeds are very young. Cut off their roots, and they die. If you wait until they get too large, they are much more difficult to remove.

Mowing also controls some weeds, but for others, it changes them from upright plants to lower growing forms. Mowing and tilling are not effective against weeds that propagate vegetatively, as that spreads the weeds as they are cut into smaller sections.

Weeds that reproduce by above- or below-ground horizontal stems are very troublesome. Some creep across the top of the soil and send down roots; others send shoots under the soil surface, and the weed shoots sprout up among the desirable plants. Field bindweed can spread many feet in all directions in one season.

Prevention is a very important way to discourage weeds.

Whenever you bring soil, soil amendments or mulches into your garden, make certain you are not introducing weeds. Always buy materials that have been composted to kill weed seeds and other pests.

Mulches also help discourage annual weeds. Weed seeds need light to germinate, and covering the soil with 2 inches of mulch prevents many seeds from germinating. Put this mulch on after the soil warms, or it will slow down the growth of your warm season plants.

Black plastic is an effective control for annual and perennial weeds. Used correctly, it prevents seeds from germinating and helps control infestations of spreading perennials. It is very useful in vegetable gardens, but never use it around fruit trees, as it will promote root rot.

I discourage using herbicides around vegetables. Pay special attention to the label directions. Many herbicides are not registered for edible crops. Others are registered for some crops but not for other. Using them will adversely affect plants or seeds planted in adjoining rows.

Home garden herbicide use is best limited to controlling difficult, spreading perennials before crops are planted or after they are harvested in the fall.


When most gardeners think pests, they think insects. There are likely more than 2 million species of insects on Earth and some 50,000 kinds in Utah. Fortunately, most of these insects stay alive by eating other insects. If this were not the case, insects would destroy every crop on Earth.

Because of this, it is important to work with nature, not against it. Gardeners sometimes create problems when they kill the desirable insects and other creatures that feed on garden pests.

Good pest-control strategies are not just about killing pests. Pest management preserves the insects that feed on the pests. Never apply insecticides that are going to make problems worse, not better.

Insects survive because they are so adaptable. They grow from the deepest caves to mountain tops, from deserts to lush forests and everywhere in between. They also reproduce prolifically. Aphids can reproduce in as little as five days and could produce billions of offspring in a single season if they all lived.

When considering the numbers of insects, there are relatively few that cause problems for home gardeners. When they do, they can destroy an entire crop very quickly, as many can eat several times their body weight daily.

Most insects move readily from plant to plant. Some fly long distances, and others move on wind currents or by other methods.

Insects feed by two methods. Chewing insects, including grasshoppers, consume portions of the leaves or other tissues. Sucking insects insert their sucking mouthparts into the plant and suck out the juices. It is easier to see the damage from chewing insects, as they remove part of the plant.

Sucking insects, including aphids, usually cause discoloration of the stems or foliage. Older plant parts usually stay the same size and shape, but the newer growth is curled, twisted and distorted.

Insecticides have two modes of action. Contact insecticides kill the insects they contact or touch. Stomach poisons kill the pests when they eat the foliage. Knowing the feeding mode of the insect helps you make the best control decisions.

If spraying is needed, use the least toxic but most effective products available. Be specific. Apply products that kill the pests but do not harm beneficial insects. Spray early in the morning or later in the evening to avoid killing bees. Spraying entire yards or gardens is wasteful and unwise, because most insects are host-specific.

Mechanical barriers, including row covers and screens, are very effective in controlling cabbage worms, aphids and leaf miners. Use them over cabbage, cauliflower, broccoli and similar crops and beets and spinach.

Put the covers over the plants before the pests emerge, and leave the covers on for the growing season. This saves numerous sprays and keeps the plants pest-free. Row covers cannot be used on crops that produce a fruit and need to be pollinated.


Diseases are divided into two categories.

Pathogenic diseases are caused by fungi, bacteria, viruses or other organisms. These spread from plant to plant when conditions are right. To control these diseases, you must control the organism or change the environmental conditions so they cannot reproduce.

The best control for any disease is to grow a plant that is not susceptible to a disease. For some plants, good controls are available, but for others, they are not.

Celebrity tomato is designated by the initials VFTN. This means that the tomato is resistant to verticillium, fusarium, tobacco mosaic virus and nematodes. If these are a problem in your garden, select this or another disease-resistant cultivar.

Keep in mind that resistance is not immunity. Almost any plant can get a disease if the conditions are right. It is important that these plants are grown to help resist diseases.

Nonpathogenic diseases are not caused by an organism. Temperature, water, sunlight and nutrient extremes, poor soil, wind, hail or other problems greatly interfere with growing high-quality produce.

Most diseases fall into this category. While we may not be able to totally control the environment, it is possible to alter planting dates, to water and fertilize correctly, improve the soil and to otherwise provide the best growing conditions for the plants.

In Utah, the most important way to control both pathogenic and nonpathogenic diseases is to learn how to water correctly. Overwatering keeps plant leaves and roots too wet and encourages fungal and bacterial growth.

Poorly drained soils and overwatering are another disaster. The roots cannot get oxygen, so they cannot grow. The wet soil allows diseases to grow in the soil, which kills the roots. Many vegetables, fruit trees and berries die from this fatal combination.

Chemical control of plant diseases is difficult at best. Fungal diseases must be controlled with fungicides and bacterial diseases with bactericides. There are no chemical controls for virus diseases, so the affected plant is best discarded.

Slugs and snails

These are some of the most widespread and destructive pests that home gardeners face. They will eat most garden vegetables, berries and even climb into fruit trees. They are large and plentiful and, unfortunately, improving the soil and growing conditions for your plants often improves the habitat for these creatures.

Start by hunting them down. Make a patrol in the morning or evening and pick them up when you see them. Put them in a plastic bag and throw them away.

Never crush them in the garden, as the eggs that are in their bodies can continue to grow and hatch even though the pest is dead.

If you try bait for the pests, there are choices. The most common is metaldehyde, which is an irritant that causes the pest to lose water and eventually die as it dries out. The second type is iron phosphate, which is less likely to be toxic to pets.

Baits are more effective and last longer when covered. Traps keep the bait dry and more attractive. Traps are easily made from recycled food or soda pop bottles.

While there are natural enemies for these pests, they usually do not keep them under control. In addition to controlling them in your garden, try to get neighbors to do the same.

Other pest problems

Depending on where you live and what creatures inhabit your neighborhood, there are many other potential pests. Fence out larger animals like deer and elk to keep them away from your crops.

Almost all birds are protected, so consider covering berries and fruit with netting. Birds quickly get used to most repellents or devices that are supposed to frighten them, so those controls are not always satisfactory.

Skunks, raccoons, rabbits and squirrels can also be fenced out in some cases. In urban areas, check with your local animal control. Some have traps available to help capture the pests. There are also commercial pest-control companies that help with these problems.

When it comes to neighborhood pets, be careful. Although you do not want them to destroy your garden, you want to keep on good terms with the neighbors.

The best solution to discourage cats from using your vegetable garden as a litter box is to sprinkle ground pepper in the area. As cats sniff, it gets in their noses and makes them sneeze. That encourages them to find a different spot.

Another solution is to get a sprinkler operated by an electronic eye. When the animal walks into the light beam, it turns on the sprinkler and sprays the offending creature. Just remember where it is aimed, or you might be showered as you wander your garden.


While there are many methods for pest control, it is important to distinguish between those that work and those that are anecdotal or testimonial.

Fruit pests are particularly difficult to deal with. The Utah State University Extension Service has a great website to help backyard gardeners at www.utahpest.usu.edu. It has links to fact sheets on all common insects and diseases that attack Utah gardens. This website never sells anything and never shares your e-mail address.

Another service available on the website is pest alerts from the USU Extension Service. Request these, and get weekly pest alerts on what to do to control fruit pests. You can also sign up for regular updates on vegetable, berry, ornamental and turf pests.

Take problems to the diagnostic clinics at USU Extension Service offices in most northern Utah counties. They are conducted by USU master gardeners. Addresses and phone numbers are available at extension.usu.edu/. The site also has information on weed control.

I use handbooks from extension services in Oregon, Washington and Idaho. These excellent resources are updated annually. The Pacific Northwest weed management, insect and plant disease handbooks are available at weeds.ippc.orst.edu/pnw/weeds, weeds.ippc.orst.edu/pnw/insects and plant-disease.ippc.orst.edu/.

The Ortho Problem Solver is an excellent pest identification publication that is available at most nurseries. It is also available at www.ortho.com.

For information on controlling wildlife, try these resources. USU helps maintain a clearinghouse for wildlife control at icwdm.org/Publications/WildlifePublications.asp. Specific removal help is available at www.wildlife-removal.com/index.htm.

Don't overlook previous columns published in this newspaper. They are available in the archives on the Deseret News website. The pests have not changed, but many pesticide recommendations have. Always check pesticide recommendations in archived articles with the current labels on packages for any changes.

You can talk to me about specific pest control problems each Saturday by calling the KSL Radio "Greenhouse Show" from 8 to 11 a.m. Call 801-575-8255.

These are the most common and difficult-to-control pests affecting edible crops in Utah, based on my experience and questions from gardeners.

If there are specific pests that are troublesome to you, add a comment to this article on deseretnews.com, and I will address the most troublesome in future columns.

If you have any legal treatments or practices that have worked well for you, add those to the comments. We will share some selected ideas with readers in the future.

Problem vegetable pests

1. Verticillium and fusarium wilt

2. Squash bugs

3. Grasshoppers

4. Aphids

5. Tomato hornworm

6. Curly top

7. Powdery mildew

8. Weeds of all kinds

9. Cabbage moths

10. Root rot

Fruit tree pests

1. Codling moth

2. Cherry fruit fly

3. Peach tree borer

4. Aphids

5. Powdery mildew

6. Coryneum blight

7. Fire blight

8. Root rot

9. Spider mites

10. Iron chlorosis

Berry pests

1. Slugs and snails

2. Strawberry root weevil

3. Root rot

4. Aphids

5. Spider mites

6. Grasshoppers

7. Borers

8. Birds

9. Weeds of all kinds

10. Iron chlorosis

Weed problems

1. Field bindweed (wild morning glory)

2. Quack grass

3. Bermuda grass

4. White top (hoary cress)

5. Mallow

6. Purslane

7. Nutsedge and other bulbous plants

8. Redroot pigweed

9. Annual grasses

10. Puncture vine (goat heads)

Deseret News garden expert Larry A. Sagers, a horticulture specialist for the Utah State University Extension Service at Thanksgiving Point, can be heard every Saturday on the KSL Radio "Greenhouse Show" from 8 a.m.-11 a.m. Call 801-575-8255 with your questions. E MAIL: features@desnews.com