9 Homemade Pesticides for Your Flower Garden

A Guide to 9 Homemade Pesticides You Can Use in Your Flower Garden

Brew Natural Pest Control Products for Flowering Plants

Cade Martin / CDC

Since organic gardening has changed from a novelty to a commonplace way to grow ornamental plants, manufacturers have responded to gardeners’ demands for effective but natural pest-control products. These natural garden remedies are no longer exclusive to specialty nurseries and mail-order catalogs; instead, one can purchase a range of nontoxic garden supplies even at neighborhood discount or home improvement stores.

However, these organic flower garden treatments sometimes come with a premium price tag. This may discourage flower gardeners from using natural pest deterrents—after all, we usually don’t eat our flowers, so why does it matter?

There are many reasons to grow flowers organically, including the need to foil recalcitrant pests that seem immune to the expensive ready-to-use products sold on store shelves. Even the dyed-in-the-wool organic flower gardener who generally avoids pesticides can appreciate the ability to formulate homemade garden remedies to control stubborn perennial insect pests. Gardeners can turn to their pantries, gardens, and even the pests themselves to create potent plant remedies and cures that cost just pennies. Here are some easy homemade organic pest-control solutions you can try.

Homemade Insect Soap

Insect soaps are available in any organic gardening aisle, but gardeners can make a homemade garden spray that’s just as effective for aphids, caterpillars, and mites. Combine three drops of mild dishwashing liquid in one quart of water. An added tablespoon of cooking oil helps the mixture cling to leaves. Spray plants to the point of drenching, but don’t use on blossoms or when temperatures are over 80 degrees Fahrenheit to prevent scorching the plants.

Garlic Spray

Garlic has natural antibacterial, antiviral, and anti-fungal properties, and it is also a potent pesticide. Peel and crush five garlic bulbs and mix with 16 oz. of water. Let the garlic infuse in the water overnight. Add a dash of dish soap to the mixture, then strain it through a fine strainer. Dilute this liquid in a gallon of water, then place in a spray bottle. Spray this solution on your plants once or twice a week to control most insect pests.

Homemade Tobacco Spray

Everyone is familiar with the negative health effects of cigarettes, but the nicotine in tobacco is poisonous to all kinds of insects, as well. Gather enough cigarette butts to harvest a ¼ cup of tobacco leaves. Place these in a sock, and soak them in a quart of water overnight. Avoid using this homemade insect spray on members of the nightshade family, like petunias, datura, and nicotiana flowers, as tobacco can harbor the mosaic virus, which affects this family of plants.

Epsom Salt Pesticide

Epsom salts can be either be sprinkled around plants or dissolved in water to make a spray. To make a spray, dissolve one cup of salts in five gallons of water, then pour into a spray bottom and apply to any pest-afflicted plants. The salt mixture is especially effective on slugs and beetles. Another option is to sprinkle the salts around the base of the plants every week or so. It will deter pests, and also add magnesium to the soil, which increases the absorption of nutrients by the plants.

Oil Spray

An effective insecticidal spray can be made with two very simple ingredients: soap and oil. Oil spray works by coating enclosing and smothering soft-body insects, such as aphids and mites. Mix a cup of vegetable oil with a quarter cup of liquid soap and shake it well. This concentrate can be stored until you need it. When treating plants, mix one tablespoon of this concentrated liquid with four cups of water. Best results require reapplication once a week.

Hot Pepper Bug Repellent

Even for gardeners without a penchant for spicy foods, it’s worth adding a row of hot chili pepper plants to the garden for their bug-repelling effects. Place a handful of dried hot peppers in the food processor, seeds and all, and grind to dust. Take care not to get the dust on your skin or eyes. Sprinkle around garden plants to repel ants and whiteflies. For more sticking power, add 1/2 cup of ground chili peppers to a quart of fine horticultural oil, and mist the tops and undersides of flower foliage.

Citrus Spray

A simple citrus spray is effective at killing aphids and some other soft-bodied insects. Grate the rind from one lemon, and add it to a pint of boiling water just removed from the heat. Allow the mixture to steep overnight, then strain through cheesecloth or a fine sieve. Pour the mixture into a spray bottom and apply to both the tops and bottoms of the leaves on afflicted plants. This mixture must contact the insects in order to be effective.

Rubbing Alcohol Bug Spray

Rubbing alcohol quickly desiccates the bodies of soft sucking pests such as aphids, mealy bugs, and thrips.


Rubbing alcohol can also damage plant tissues, so gardeners should use alcohol sparingly in the garden.

The best way to apply is by dabbing a cotton swab soaked with rubbing alcohol directly on the pests, taking care to avoid the plant itself. Plants with waxy leaves may tolerate a dilute alcohol spray of one-cup alcohol mixed with a quart of water. This is a favorite way of quickly dispensing of orchid pests.

Bug Juice Spray

Gardeners may be repulsed yet fascinated to learn that one can make a natural bug spray out of the pests themselves. No one is exactly sure why pests are their own worst enemies when applied to plants, but researchers speculate an anti-cannibalism mechanism or the presence of a chemical that inhibits insect feeding. Gather enough of the offending pests to fill at least a teaspoon, and pulverize them with the back of a spoon. Place the mashed bugs in cheesecloth, and soak in two cups of water overnight. For best results, use the bug juice within three days.


Ornamental Production

Common Pests:

The most common pests of foliage and flowering plants are spider mites, mealy bugs, fungus gnats, whitefly and aphids. The use of plant material for outdoor as well as indoor decoration exposes them to all manner of garden pests, such as caterpillars, slugs, snails and thrips, many of which thrive once the plants are moved back indoors. For this reason, plants which are being moved from decks, patios, etc. to the home or office should be washed thoroughly with a spray of clear water.

Pest Control:

Despite the best control programs employed by growers and retailers, it sometimes happens that a new plant harbors pests whose eggs have survived to hatch in you home conditions. A period of isolation (10-14 days) may be the answer. Yet some pests may not show up for a longer time, being present in small numbers until the indoor climate becomes more favorable; for example, spider mites thrive in dry air, so they may not become evident until the humid season is past.

Regular and frequent checking for abnormal growth and insects can be combined with your checks for watering needs. Most pests lurk under leaves and close to the growing tip where tissue is softest. Most of these pests can be washed off with a spray of water. Several washes over a period of two or three weeks, plus isolation for the infested plant to prevent the pest from moving to other plants, generally eliminates the problem. Chemical sprays are not pleasant to use, and are generally recommended for outdoor application.. Some pesticides are hazardous, not only to the general environment, but to the plant tissue. Ferns are extremely sensitive to all forms of chemical spray, and infested fronds are best removed and destroyed.


Diseases are rare on foliage and flowering plants. The only ones likely to be encountered are Botrytis, the gray mold fungus that invades dead and dying tissues, and soft leaf spot or crown rot fungi which thrive in moist atmospheres. The best cure is to remove affected parts, and avoid splashing the plant when watering; give more space for air circulation, or move infected plants to a drier place.

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Pests of Foliage & Flowering Plants


23 Plants that Repel Garden Insect Pests

What plants keep insects away? An endless struggle within the realm of gardening is keeping away bugs and insects that want to harm your precious crop.

An easy way to naturally get rid of these pests is by planting the right herbs, flowers, and other plants that will repel them.

Many of those that will be discussed below are also great additions around your patio and outdoor furniture.

These plants help to naturally repel pests such as ants, mosquitoes, and other pests when you’re outside enjoying the weather.

1. Basil

Basil is among the plants that repel mosquitoes or gnats and your standard house-fly.

Another perk is that it grows easily in a pot in a windowsill, so you can have some for in your kitchen as well as in your garden to keep you protected both inside and out.

Basil is easily incorporated in many recipes, so you’ll never run out of ways to use your basil once you start growing it.

2. Lavender

Not only is it a gorgeous flower, but using lavender is also an excellent natural way of keeping away pests, particularly flies, fleas, mosquitoes, caterpillars, and moths.

Not only does it add some color to your garden or windowsill, but lavender also adds a sweet and relaxing fragrance to the home or garden.

In addition to growing it in your garden or in a pot, you can also tie small bundles of the herb over doorways and near windows to keep insects out of the house.

3. Lemongrass

Lemongrass is a key ingredient in many mosquito-repelling candles and oils. It also ranks high among the plants that repel garden insects.

This ornamental grass grows as an annual in most locations, but it will be nice and tall and potent during peak mosquito season.

4. Mint

This herb is another successful mosquito repellant plant as well as a tasty addition to many dishes.

Mint, however, does have a tendency to grow aggressively, taking over any garden bed it may be planted in or near.

The best bet is to plant it in a container. Not only will this contain the herb where you want it, but it will also make it easier to move it to a different location (such as atop your patio table) as needed.

5. Rosemary

If your veggies are being endlessly harassed by bugs, you may want to plant some rosemary nearby to help repel some of those garden pests.

Rosemary grows well in-ground or in a container, and is also a good choice for most ornamental landscaping.

As it grows it will repel most bugs, but you can also use the herb to make a natural repellant spray.

To make a repellant, simply add some dried rosemary to boiling water for half an hour, then straining into a container that contains just as much cool water.

Store the mixture in the fridge in a spray bottle and use when needed.

6. Bay Leaves

Bay leaves are great for repelling flies that might otherwise lay their eggs in your garden. Another bonus is that bay leaves are a great addition to many soups, stews, and pasta.

7. Dill

Dill is another double-duty herb that falls on the list of pest repellent plants .

It’s very successful at getting rid of garden insects such as aphids, spider mites, cabbage loopers, tomato hornworms, and squash bugs.

To protect these specific plants, add some dill to your garden in the vicinity of the vulnerable items.

8. Petunias

Another common garden flower, petunias are just as productive as they are pretty.

These easy-growers are great at protecting your garden from aphids, and getting rid of other garden pests such as tomato hornworms, asparagus beetles, leafhoppers, and squash bugs.

You can find them in almost any color you prefer, and they tend to grow very easily, whether in-ground or in a container.

9. Fennel

If you have a problem with slugs and snails attacking your garden, fennel should definitely be planted in or around your garden.

It’s also among the insect repellent plants for aphids, slugs, and other garden pests.

10. Thyme

This herb is great for keeping out whiteflies, ants, maggots, corn earworms, cabbage loopers, and tomato hornworms.

It isn’t extremely aggressive (like mint) so can easily be incorporated throughout your garden to protect your cabbages, tomatoes, and other plants.

11. Alliums

Plants belonging to the Allium family are regarded as one of the best all-purpose plants that repel insects and bugs to have in the garden.

They’re great for keeping out slugs, flies, aphids, and cabbage worms. Some examples of Allium plants include chives, leeks, and shallots.

Find the one that’s right for you and your garden, and plant it close to anything from peppers to broccoli to carrots to keep them safe from pests.

12. Chrysanthemums

These are excellent flowers to plant in your vegetable garden to deter pests such as nematodes, spider mites, harlequin bugs, Japanese beetles, and even lice and fleas.

Chrysanthemums are also listed among the plants that repel ants. They have a natural ingredient called pyrethrum which is a strong alll-round insect-repellant.

These flowers add a nice pop of color anywhere you want to plant them in your yard to protect your garden from unwanted pests.

13. Marigolds

Another beautiful flower that falls among the plants that repel insects is marigold.

These flowers give off a scent that repels mosquitoes and aphids, and sometimes even rabbits!

They make for a beautiful border around your garden and will help protect the health of your other plants as well.

14. Nasturtiums

If your garden seems to be loved by squash bugs, beetles, or whiteflies, you’ll definitely want to companion-plant some nasturtiums.

Nasturtiums release a scent in the air that naturally repels many insects without harming any other plants or even deterring the beloved bee.

15. Onions

Although they’re mostly known for repelling your date, onions are also great for getting rid of certain harmful insects.

Now, they’re not a total-bug repellant like some of the other plants that repel bugs, but they are great for keeping out cucumber beetles and even carrot maggot flies.

Some farmers also plant onions near their tomatoes to help repel aphids.

16. Calamint

Yet another mint family member, calamint is great for deterring cabbage worms and cabbage loopers, as well as moth larvae.

This mint cousin, however, spreads very easily like mint itself, so be careful where you plant it.

17. Garlic

Garlic is great for protecting your blueberries, roses, and raspberries from Japanese beetles, as well as keeping the aphids off your lettuce.

They may also repel spider mites, ants, and caterpillars, so they’re a great companion to any plants that might be susceptible to those pests.

18. Catnip

A perennial member of the mint family, catnip doesn’t proliferate quite as much as mint does, so you’re safe to plant it directly in your garden among your plants.

It’s great for protecting eggplants, radishes, and other plants that are susceptible to flea beetles.

19. Tansy

Many gardeners will plant tansy near their roses to keep away pesky Japanese beetles.

It’s believed that tansy gives off a scent that confuses the pests, making it difficult for them to find the rosebushes and make their homes there.

20. Borage

This herb is great for getting rid of garden pests naturally. It works best at keeping out hornworms and cabbage worms.

It also makes a nice-looking addition to your garden and will support your local honey bee population.

21. Castor Oil Plant

This should first be prefaced by the warning that castor should be grown with caution — it is poisonous to humans and animals if ingested.

That being said, if you plant it with care and only where appropriate, this plant is excellent at repelling moles and voles.

22. Tomatoes

That’s right, planting tomatoes can actually help protect other plants in your garden.

However, be sure to plant at least one companion plant nearby that will, in turn, protect your tomatoes from pests.

In particular, tomatoes will keep your asparagus free from pests as the scent of tomato plants repels the asparagus beetle.

Since many gardeners plan to have tomatoes anyway, it’s helpful to know that they can perform double-duty if you plant them near your asparagus as well.

23. Citronella Plant

The scent citronella comes from the plant called Cymbopogon nardus. It is a member of the geranium family and resembles spiky ferns.

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Mosquitoes hate the smell of the citronella plant.

Simply planting it in your garden is not enough to repel mosquitoes; however, crushing or touching the leaves will release its oils.

That’s the scent that m osquitoes hate — it will prevent them from coming near.

The Bottom Line

If you were wondering how to get rid of garden insects naturally, this is an extensive list of plants that repel insects to consider including in and around your garden.

If you take the time and plan it correctly, you can have the best companions near each of your plants, repelling the most harmful insects and protecting the health of your garden.


Insect and Related Pests of Flowers and Foliage Plants

Table of Contents


This is the first real revision of a manual first published in 1978, bravely called Insects and Related Pests of Flowers and Foliage Plants. In those innocent days, the Western flower thrips and sweetpotato whitefly were not yet found as floricultural pests in the Eastern United States. The leafminer, Liriomyza trifolii, was then a scourge of greenhouse flowering crops, and aphids were not particularly difficult to control with traditional pesticides. Nine additional entomologists have contributed to the expansion of the first edition, making this a truly regional publication.

A note about the illustrations in this manual. Special effort was made to assure all of the illustrations are all in the public domain. Consequently, no permission is required to use them. Whenever possible, the pests face up or to the left in each illustration. An exception to this rule is found in the Slugs and Snails chapter because the respiratory pore (an important diagnostic character) of slugs is on the right side of the body. Illustrations by: Ponglerd Kooaroon, Suan Van Gieson, Ramona Beshear, Tong-Xian Liu, Mei-Jung Lin, L. L. Deitz, J. J. Davis, H. A. Denmark, J. B. Burch, F. H. Crittenden, Nellie M. Quaintance, O. C. Mohr, James Wilcox, J. R. Baker, California Experiment Station, Connecticut Agricultural Experiment Station and USDA.

Special thanks are extended to Drs. Maurice H. Farrier, NC State; Paul R. Heller, Pennsylvania State University; and Richard L. Miller, Ohio State University, for reviewing the manuscript of the first edition. Their time spent on the manuscript is well appreciated. Thanks also are extended to Katherine Curle who helped with translating much of the early draft into English. The patience of Vicki Grantham, Carmen Sasser, Teresa Snell, Sara Watson, and Stella Nwosu as they prepared the typewritten copies of the manuscript is heartily appreciated. The enthusiastic proofing, guidance on page layout and other editorial duties by Deborah Dunsford is also greatly appreciated.


Horticulturists estimate that 1,500 varieties of herbaceous ornamental plants are grown commercially in North Carolina. Ornamentals are grown in commercial greenhouses, commercial fields, professionally maintained landscapes, interior plantscapes, and home grounds, as well as inside homes or in hobby greenhouses.

An amazing variety of insects feed on flowering and foliage plants. Many field, fruit, and vegetable crop pests such as the cabbage looper, corn earworm, diamondback moth, and oblique banded leafroller also feed on ornamentals. Lush growth and sheltered growing conditions make ornamental herbs especially attractive to plant pests.

The routine use of insecticides usually eliminates predaceous insects and mites. However, pests remaining after treatment sometimes tolerate commonly used insecticides. To stay in business, most commercial flower and foliage plant growers must become fairly sophisticated in using various types of pest management practices, insecticide formulations, application equipment, and in rotating insecticides from one chemical group to another.

Commercial growers use a battery of general and restricted-use pesticides. Although amateur gardeners battle the same pests, the most effective chemicals for control are often very expensive or are restricted so that homeowners are not allowed to use them. This puts a moral burden on the commercial grower to try earnestly to eliminate all plant pests from bedding, potted, and cut plants before selling them.

Keys to adults and immatures of the pests referred to above are included in this publication. These keys, plus the color plates and the illustrations in the insect notes, will help you identify the pests of herbaceous ornamental plants. Identification is important to assure proper control measures.

Management of Insect and Related Pests

This manual is designed to augment state Cooperative Extension publications on pest management, not to duplicate them. In no way are the suggestions for safe use and calibrations for proper application in the state Cooperative Extension recommendations to be belittled or ignored. This section on management should be viewed as an expansion of explanations begun in those publications.


Chemical Control

Total reliance on pesticides for pest management is labor intensive and sometimes very hard on the plants. Although there are numerous practical and philosophical problems with the chemical control of insect and mite pests in the greenhouse, pesticides will remain important in greenhouse pest management at least for the next few years. Control of pests in the greenhouse is often difficult because of lush, sheltered growing conditions. In general, insects, mites, and slugs reproduce more rapidly in warmer temperatures. Also, periodic use of pesticides in greenhouses often reduces parasites and predators of greenhouse pests because the pests tend to be more resistant to pesticides than their predators and parasites.

Application of pesticides is almost essential if one is to stay in the greenhouse profession. Eliminating weeds inside and outside the greenhouse reduces alternate hosts for ornamental plant pests. Screen doors and vents make it harder for moths and beetles to fly in and lay eggs or feed. But, careful as the grower may be, sooner or later an insect or mite will come in on the clothes of workers, on cuttings, in pots, or in soil. Many growers apply pesticides periodically as «insurance» against accidental infestations. Despite these precautions, however, insects or other pests may become established. Some growers treat whenever they discover pests. Growers should survey the plants on a daily or every-other-day basis to guard against extensive damage by insects, mites, or slugs.

Pesticides are applied in greenhouses in almost every conceivable manner. Legal methods are usually the safest! Growers use aerosols, mists, smokes, fogs, dusts, sprays, drenches, and granules – everything but aerial application and backrubs. Aerosols, smokes, mists, and fogs must be applied when the greenhouse is closed (at night or in the winter). Since most pesticides are sensitive to ultraviolet rays, treatments made later in the evening will be more effective. After the waiting period specified on the label has passed, the structure must be well ventilated before workers can safely enter.

Fogs, smokes, and aerosols are generally applied on a cubic-foot basis. Compute cubic feet by multiplying the area of the floor times the average height of the roof: that is, the length times the width times the average height (Figure 1A). For houses with flat, sloping roofs, add the height at the eave to the height at the highest part, divide by 2, and multiply by the area of the floor (Figure 1B). For houses with rounded roofs, measure the lowest point and the highest point in the middle, then measure the heights at 1 ⁄4 and 3 ⁄4 of the distance to the low point. Add these 4 measurements, divide by 4, multiply by the area of the floor, and you have a pretty close estimate of the volume of the house (Figure 1C and Figure 1D). (Although this estimate is a little low, rounded roof houses are usually covered with polyethylene film and are consequently very tight. Thus, applications in these houses do not dissipate as rapidly as applications in fiberglass or glass houses.) Fogs, smokes, and aerosols generally need to be diluted by the air in the greenhouse to avoid damage to the plants.

Place smoke fumigators so that the smoke does not vent directly onto the plant foliage. Growers customarily wear self-contained breathing systems or gas masks when applying fogs, smokes, or aerosols. Some growers who use smoke fumigators determine the number of fumigators needed, based on cubic feet, and light those furthest from the door first. This allows the grower to vacate the house before it becomes dangerously filled with fumes. Two people should always be present when applying toxic substances in the greenhouse. If one person gets accidentally poisoned, the other can drag the victim to safety and call for help. Dusts and sprays are applied with conventional dusting or spraying equipment. Necessary safety clothing must be worn.

Apply granular insecticides with a handheld shaker or some other device that does not grind up the granules. Wear boots, long pants, a long sleeved shirt, rubber gloves, and a respirator. The plants and potting mix should not be handled until the granular pesticide has been washed from the foliage and watered in thoroughly.

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Figure 1A. Compute cubic feet by multiplying the area of the floor times the average height of the roof: that is, the length times the width times the average height.

Figure 1A. Compute cubic feet by multiplying the area of the floor times the average height of the roof: that is, the length times the width times the average height.

Figure 1B. For houses with flat, sloping roofs, add the height at the eave to the height at the highest part, divide by 2, and multiply by the area of the floor.

Figure 1B. For houses with flat, sloping roofs, add the height at the eave to the height at the highest part, divide by 2, and multiply by the area of the floor.

Figure 1C. For rounded roofs, measure the lowest point and the highest point in the middle, then measure the heights at 1/4 and 3/4 of the distance to the low point. Add these 4 measurements, divide by 4, multiply by the area of the floor.

Figure 1C. For rounded roofs, measure the lowest point and the highest point in the middle, then measure the heights at 1/4 and 3/4 of the distance to the low point. Add these 4 measurements, divide by 4, multiply by the area of the floor.

Figure 1D. For rounded roofs, measure the lowest point and the highest point in the middle, then measure the heights at 1/4 and 3/4 of the distance to the low point. Add these 4 measurements, divide by 4, multiply by the area of the floor.

Figure 1D. For rounded roofs, measure the lowest point and the highest point in the middle, then measure the heights at 1/4 and 3/4 of the distance to the low point. Add these 4 measurements, divide by 4, multiply by the area of the floor.

Integrated Pest Management

IPM uses all suitable methods to reduce insect and mite populations to the lowest acceptable level. IPM is a complex program as each crop must be considered individually. However, there are a number of basic practices that apply to most greenhouse crops.


An effort should be made to avoid carrying insects into the greenhouse by wearing clothes that are brown, red, or black. Do not wear white, yellow, or green, as these colors are attractive to aphids, thrips, whiteflies, leafminers, and darkwinged fungus gnats. Light to dark blues also are attractive to aphids and thrips.


Before any plant material is brought into the greenhouse, it should be thoroughly inspected for insects, mites, and diseases. Furthermore, new plant material should be kept in a separate section for a week or more before such material is incorporated into the production area. Such highly resistant pests as the green peach aphid, western flower thrips, and silverleaf whitefly move readily on plant material. The swapping of insects, mites, and diseases on infested plant material is without doubt the major way resistant thrips, aphids, and whiteflies are transported throughout the greenhouse industry.


In an experiment with greenhouse screening in California, a crop of chrysanthemums was grown successfully without a single application of pesticides. Exclusion demonstrations at North Carolina State University with the western flower thrips and the silverleaf whitefly have shown that both pests can be significantly excluded by spunbonded and perforated polyethylene screening. With screening, the finer the mesh, the greater is the tendency to restrict air flow into the greenhouse. Polyspun materials cut air flow by a factor of two. The perforated polyethylene screening cut air volume by a factor of five (Figure AA).

Although the pore sizes of some screening materials are large enough that the thrips are capable of wedging through, the screening still excludes many thrips. Evidently, these materials are not recognized by thrips as a suitable substrate to feed on. When the thrips probe the screening they may instinctively resume flight searching for a suitable plant.

Pest Recognition

For proper management, it is important to be able to recognize the various kinds of pests in their various stages of development. Probably the most frequently misidentified pests are shore flies and darkwinged fungus gnats. Shore flies are of little economic consequence in the greenhouse but are very resistant to pesticides. Thus a grower can waste effort and pesticides trying to chemically control shore flies rather than trying to control algae the shore flies are breeding in. Another example of misidentification is the assumption that parasitized green peach aphids are some sort of new ‘tan’ aphid. Parasitized aphids adhere to the plant fairly tightly, so in spite of repeated applications, these ‘tan’ aphids seem to be impossible to kill.


Constant vigilance for insects, mites, and diseases is required for effective pest management. An employee or certain employees should be assigned the responsibility of scouting for insects and other pests on a regular basis (perhaps weekly during the winter and twice weekly during the summer). Written records of where various pests are found should be kept. Pests can be monitored by using yellow and blue sticky cards (Figure BB, Figure CC, Figure DD, Figure EE, Figure FF, Figure GG, Figure HH, Figure II, Figure JJ), by using yellow pan traps, and by examining the foliage, flowers, and occasionally the roots. Light traps outside can be used to monitor for European corn borer, corn earworm, and beet armyworm adults.

Record Keeping

A written log should be kept of pest type, locality, abundance, and all pesticides applied. Such records can be of long-term benefit as many pests tend to appear at about the same time each year. However, the short-term benefits of written records may be greater. Knowing what pests survive a pesticide application alerts the grower to the possibility of poor timing, poor application, or pesticide resistance in the pest population. A change in strategy, application technology, or type of pesticide can be made before the crops are significantly damaged.

Biological Control

Some growers use beneficial organisms for biological control where appropriate. Unfortunately, there are no really effective organisms available for managing the silverleaf whitefly or the western flower thrips. Encarsia formosa parasitic wasps infest silverleaf whiteflies to some degree and Amblyseius predatory mites, used for spider mite suppression, can feed on thrips. Bacterial and nematode organisms can be readily integrated into a traditional pest management scheme, whereas others require a fairly high level of management. Aphytis wasps, Aphidoletes maggots, and green lacewings are available for aphid suppression. Bacillus thuringiensis kurstaki pesticides are available for caterpillars. Bacillus thuringiensis israelensis and Steinernema carpocapsae nematodes suppress darkwinged fungus gnats. Cryptolaemus and Delphastus lady beetles (when available) can be used for mealybugs and whiteflies. Parasitic wasps are available for soft scale management and predaceous mites are available for spider mite suppression. Encarsia formosa parasitic wasps can be used especially for greenhouse whitefly suppression. Except for Bacillus thuringiensis pesticides, the use of biological organisms is usually not compatible with the use of chemical sprays. It is possible to integrate sprays of soaps and oils with Encarsia formosa by timing pesticide applications to coincide with the «black scale stage» of the parasite’s development. Also the «brown mummy» stage of aphids infected with Aphytis wasps are resistant to soaps and oils.

Organic Control

Organic growers tend to be wary of relying on pesticides for routine pest management. Most organic growers are highly receptive to the basic integrated pest management practices (screening, biological control, and monitoring). The range of chemicals organic growers can use is limited to those that are certified to be «organic» by various organizations such as the California Certified Organic Farmers. Some of these chemicals work well and others are marginally effective. Finding formulations that are certified as organic and that are actually labeled for greenhouse use is sometimes a problem. Some organic growers in North Carolina use screening to exclude pests and methods such as irrigation to dislodge and destroy mites and aphids or washing the produce by hand at harvest to remove pests.

Organic Chemicals: Soaps, oils, and nicotine sulfate can be used for aphid suppression. Soaps, oils, neem extracts, and pyrethrum sprays and aerosols are moderately toxic to 3 whiteflies. The Bacillus thuringienses kurstaki pesticides and pyrethrum sprays, and aerosols are effective for caterpillar control. Soaps and pyrethrum pesticides suppress mealybugs. Spider mites are susceptible to soaps and oils. Pyrethrum sprays and aerosols help suppress thrips.

Figure AA. Screening structure retrofitted to a commercial greenhouse.


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