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Pest and disease problems are an unavoidable fact of life for the mini-farmer . Sometimes, they are barely noticeable and cause no significant problems. But at other times they can cause major crop losses.
There are, unfortunately, hundreds of pests and diseases that affect vegetable crops. Going into the detail of identifying these is beyond the scope of this guide, so instead I'll refer you to The Organic Gardener's Handbook of Natural Insect and Disease Control, published by Rodale and edited by Barbara Ellis and Fern Bradley. This 500-page book is loaded with color pictures and extensive explanation for every disease or pest you are likely to encounter, including specific details of organic methods for dealing with problems. What follows in this section is an overview that concentrates more on principles than details, along with my own unique passive-active-reactive pest management strategy developed specifically for the needs of mini-farms.
Since the old adage that "an ounce of prevention is worth a pound of cure" is true, mini-farming focuses automatically on passive prevention by giving plants what they need. Active prevention is used when experience or reliable data indicate that a particular pest or disease is likely to be a problem. Active reaction is employed when the value of likely crop damage will exceed the costs of active reaction methods.
Passive prevention is the application of good farming practices:
well-composted and appropriately amended healthy soil, adequate sunshine, proper watering, crop rotation, and sufficient airflow. In essence, this simply means to give plants growing conditions that are as close to optimal as possible. This will make them healthier and thus less susceptible to diseases and less attractive to pests.
Active prevention uses active measures to prevent diseases or repel insect pests. Examples include applying repellent garlic or hot pepper sprays on plants to deter pests, installing physical barriers, putting out traps, or spraying the plants periodically with a fungus preventative. Sometimes, for certain types of pests, poisons that are usually used as a reactive measure may be required as active prevention.
Active reaction occurs when preventative measures fail and a problem already exists. Active reaction will often employ the same methods as active prevention, only with greater intensity, but it will also include, in most cases, the application of natural botanical or synthetic poisons or fungicides.
Pest management needs to be viewed holistically, as part of a bigger picture, to minimize crop damage while simultaneously protecting the long-range viability of the mini-farm. As part of this view, it is good to establish a threshold for what constitutes an acceptable level of damage before reactive, as opposed to preventative, measures need to be taken. This threshold is established economically, considering that the time, costs, and risks associated with active pest control measures will diminish the net grocery savings. So the threshold of acceptable damage for a given crop, in terms of percentage crop loss, is the level at which the value of the lost crop portion exceeds the cost of active control measures.
Passive prevention gives the biggest bang for both your time and money because the focus lies mainly in performing ordinary farming chores. Soil, water , sunshine, and crop rotations are the foundation of pest and disease control; all of these create an environment inhospitable to the persistence of pests and disease.
A healthy, living soil with plenty of nutrients allows for vigorous growth so that crops can outgrow problems. In addition, healthier plants are less attractive to pests and less susceptible to disease in most cases. Healthy soil plays host to various portions of the life cycles of many beneficial insect populations, along with beneficial microbes that compete with nasty pathogens for nutrients and generate antibiotics to eliminate them. It is no mistake that forests thrive independent of human intervention, and the more closely a farmer's garden approximates naturally optimal conditions for a crop, the less susceptible it will be to pest and disease problems.
An important aspect of healthy soil, particularly with intensive agriculture, is compost. As discussed in section 5, merely using compost in your soil can significantly reduce pest and disease problems.
Proper watering is another important aspect of disease control.
Plant diseases spread most easily when plant tissues are wet; both excessive watering and overhead watering can increase the likelihood of disease problems. However , adequate moisture is also important because drought-stressed plants become more attractive to pests.
Crop rotation is impossible to over emphasize. Just like there are viruses and bacteria that affect some mammals but not others-such as feline leukemia-there are numerous plant diseases that affect one family of vegetables but not others. Since these microbes need a host hospitable to their reproduction to complete their life cycles, depriving them of the host they need through crop rotation is extremely effective at controlling many diseases. The same applies to insect pests, so the same crop should not be grown in the same bed two years in a row. Ideally, crop rotation will prevent crops of the same family from growing in the same bed any more often than once every three years.
Specific plant variety selection is another important preventative.
Notwithstanding the economic benefits of using open-pollinated seeds (described in the next section), some hybrids carry disease and pest-resistance genes that can make them a better choice if certain diseases or pests become a repetitive problem. On my farm, for example, I now grow hybrid cucumbers that are resistant to bacterial wilt disease.
Finally, never discount the power of the sun. The same UV rays that make excessive sunshine a risk factor for skin cancer also scramble the genetic code in bacteria and viruses, rendering them incapable of infection. Sunshine sanitizes.
Attracting beneficial insects is also useful. Most beneficial insects feed on or invade pest species at some point in their life cycle, but they also require certain plants for their well-being. Providing these plants in the garden will give beneficial insects a base of operations they can use to keep pest species controlled.
A small planting of early, intermediate season, and late-blooming beneficial insect attractors in each garden bed will help stack the deck in the farmer's favor . Ladybugs love to eat aphids; dandelion, marigold, and hairy vetch will attract them. Tachanid flies help keep cabbage worms and stink bugs in check; a planting of parsley or pennyroyal will give them a home. Beneficial insect attractors that bloom early include sweet alyssum, columbine, and creeping thyme.
Intermediate bloomers include common yarrow, cilantro, edging lobelia, and mints. Late bloomers include dill, wild bergamot, and European goldenrod. An easy plan is to plant a few marigolds throughout the bed, a columbine plant, a bit of cilantro, and some dill.
You should familiarize yourself with the properties of beneficial plant attractors before planting them in your beds. Don't just run out and plant mint in the garden bed directly, for example, because it will take over the entire bed. Instead, plant mint in a pot and then bury the pot in the garden soil so that the upper edge sticks out of the soil 1/2 inch or so.
Plants to Provide
Parasitic wasps Moth, beetle, and fly larvae and eggs, including caterpillars Dill, yarrow, tansy, Queen Anne's lace, parsley Hoverflies (syrphid flies) Mealybugs, aphids As above, plus marigold Lacewings Aphids, mealybugs, other small insects Dandelion, angelica, dill, yarrow Ladybugs Aphids Dandelion, hairy vetch, buckwheat, marigold
Tachanid flies Caterpillars, cabbage loopers, stink bugs, cabbage bugs, beetles Parsley, tansy, pennyroyal, buckwheat
You may also want to choose some plants that you will already use in some other way-such as mint for tea, dill for pickling, and cilantro for salsa. That way you are making maximum use of limited space. There is nothing wrong with growing goldenrods just because they are pretty! Another valuable addition to the garden and yard, once the seeds have sprouted and the plants are growing well, would be chickens or guineas. Both types of birds, but guineas particularly, wreak havoc on bugs, especially bugs like ticks that nobody wants around anyway. Such livestock can effectively keep many sorts of garden pests from reaching the critical mass of population necessary to be threatening to crops.
Active prevention is often necessary when a particular pest or disease problem is a practical certainty. In such cases, the active prevention is tailored to the expected problem and can often encompass methods used for both passive prevention and intervention. For example, you may notice your garden is regularly infested with earwigs. Once the bugs are noticed inside a cauliflower plant, they've already done a lot of damage. A weekly spraying with pyrethrin (a natural insecticide) or hot pepper wax (a repellent) will increase the usable harvest significantly.
The materials and techniques most often used for active prevention include traps, immune boosters, compost extracts, imported beneficial insects, and application of repellents, fungicides, and pesticides. (The latter is particularly important with certain fruit trees.) Lures and Traps Many insect pests can be caught in traps. In commercial operations, traps are usually used to monitor pest populations to determine the optimal timing for the application of pesticides. In a mini-farm, because of the smaller land area involved, it is often practical to employ enough traps to completely eradicate a particular pest (or one of the sexes of that pest) in the garden without resorting to poisons. Examples of pests easily trapped are codling moths, Japanese beetles, and apple maggots. Traps can also be employed for cucumber beetles, white flies, and a number of other pests, but they tend to be less effective. The time when various insects emerge varies from area to area. Because the lures used in traps often have limited lifespan, the timing of their deployment can be important. This is something you'll learn from keeping notes, and within a couple of years you'll have no trouble with the timing of traps.
Immunity Boosters and Growth Enhancers
One immune booster for plants on the market at the moment is marketed by Eden Bioscience in the form of harpin protein. Harpin protein, which is produced naturally by the bacterium that causes fire blight in apples and pears, elicits a broad immune response from vegetables that makes them more resistant to a wide array of pests and diseases while enhancing their growth. Eden Bioscience uses this discovery in a product called Messenger that is nontoxic and relatively inexpensive at my local agricultural supply store.
A company called Vitamin Institute sells a product called Superthrive that is advertised to improve the growth rate of plants and whose primary ingredient is thiamine. We have done some side by-side testing, and the results have been ambiguous.
On the other hand, we have found a growth enhancer called Root Boost to live up to its advertising. It is not a fertilizer but rather an enhancer that is primarily based on kelp extract with the addition of humic acids. This product, when used as directed, really does enhance the soil and the plants that depend on it.
Compost Extract and Compost Tea Compost extract is the most well-known and most widely studied homemade disease preventative. It is exactly what it sounds like: a shovel of properly aged compost in a water-permeable sack immersed in a bucket of water and steeped for 7 to 14 days.
As the section on composting pointed out, compost extract contains a cocktail of microbes and the chemicals that they produce.
Compost extract contains a mix of beneficial bacteria and fungi that, when sprayed onto plants, eats the food substances that would otherwise be eaten by disease-causing organisms. As a result, the disease-causing organisms get starved out. A biweekly spray of compost extract is a good idea, and numerous studies attribute properties to the substance that are nothing short of miraculous. It can help prevent diseases such as black spot and powdery mildew.
Best of all, it's free.
The next step up from compost extract is compost tea. Compost tea differs from an extract in that it is the result of an active attempt to increase the amount of fungi and bacteria in the solution through aeration. Still water (as used in compost extract) doesn't have much dissolved oxygen in it, and the beneficial microbes in compost require oxygen. So, actively aerating the water in which the compost is steeped will serve to boost populations of beneficial microbes from the compost. This can be done inexpensively by putting a fish tank aerator and air pump in the bottom of a container containing the water and compost. Some reasonably priced and favorably reviewed commercial options are also available through Keep It Simple, Inc. (simplici-tea.com) or Alaska Giant (alaskagiant.com).
Importing Beneficial Insects and Nematodes Imported beneficial insects have their greatest applicability in greenhouses because, being quite mobile, when applied outdoors they are prone to fly away. Even outside they can be useful though, particularly when applied to crops infested with their favorite pest species and also provided with their favorite plants. Table 12 (earlier in this section) lists which beneficial insects to use for what problem and what sorts of plants should be established in advance of their arrival so they will stay in the garden.
Beneficial nematodes are extremely small worms that wait underground for a chance to work their way into pest insects and kill them. Beneficial nematodes are harmless to plants and pollinators and shouldn't be confused with pest nematodes such as root knot nematodes. Once inside the host, the nematodes release their gut bacteria, Xenorhabdus luminescens, into the insect's interior , where the bacteria multiply and the nematodes feed on them. The pest species eventually dies from infection. There are two commonly used species of nematodes, listed in Table 13 . Beneficial nematode products often contain both species to be as broadly useful as possible.
Beneficial nematodes require extreme care in their handling and are usually shipped by overnight courier in a refrigerated package.
They are stored in the refrigerator until they are used. It is best to wait until ground temperatures are above 50 degrees, the ground is damp, and a light rain is falling. Then put the nematodes in a pump-style sprayer and apply them to the ground where you want them. The reason for this is that beneficial nematodes are very prone to dehydration, and the falling rain helps them get into the soil. If you live north of Maryland, you'll need to apply them yearly because they can't survive the winter . If you live in a more southerly clime, the nematodes will probably survive, so a second application may not be needed.
Table 13: Beneficial Nematodes
Species Pests Controlled Notes
Webworms, cutworms, vine borers
Not effective against grubs
White grubs, vine weevils, root weevils
Organic repellent mixtures are not 100% effective, but they serve as a valuable part of an integrated strategy for pest management.
One repellent mixture is simple hot pepper . Capsaicin, the active ingredient in hot peppers, repels onion, carrot, and cabbage maggots. Simply finely chop up a cup of hot peppers, and steep it for a day in a gallon of water to which a single drop of dish soap has been added. Another repellent mixture is garlic, manufactured the same way. One thing that I do, with great success, is make hot pepper and garlic mixtures in a coffee maker that has been set aside for agricultural use only. There are some commercial repellent preparations worth noting as well, including CropGuard and Hot Pepper Wax.
There is some evidence that certain plants can repel pest insects. According to numerous sources, for example, nasturtiums and radishes repel cucumber beetles. I have experimented extensively with this practice and found no difference in cucumber beetle populations between cucumber plants surrounded by radishes and intertwined with nasturtiums and cucumber plants grown on their own. On the other hand, I have found that onion family crops repel wireworms, so I interplant leeks with my parsnips. A number of sites on the Internet list repellent plants, so I encourage you to experiment with the reputed properties of repellent plants and keep notes to see what works best for your garden.
Even the most conscientious farming practices and most vigilant preventive measures will often fail to prevent pest and disease problems. Once these problems become apparent, reactive measures are in order.
Reactive measures will often include some of the same materials and methods as passive and active prevention. For example, many fungal infections can be eradicated by the timely application of compost tea, neem oil, or garlic oil. (Neem oil is an oil extracted from a tree in India.) Most often, though, reactive measures will involve the use of fungicides and/or natural or synthetic pesticides.
Because these reactive measures use substances with greater potential to harm people or the environment, I don't recommend their application unless the farmer is certain that a likelihood exists that failure to apply them will result in an unacceptable level of crop loss.
Another tip to make active measures most effective is to take a cue from doctors treating HIV and tuberculosis: Never treat an insect or disease problem with only one active agent at a time.
Using only one active agent increases the odds of survivors living to convey immunity to that agent in the next generation. When you mix two or more active agents, you increase the odds of success while decreasing the odds of creating resistant organisms. So, for example, I routinely apply pyrethrin and rotenone in tandem, neem oil mixed with a microbial insecticide, or garlic and hot pepper repellents mixed together.
When Disease Prevention Fails
Plant diseases fall into four broad categories: bacterial, viral, protozoan, and fungal. Usually, these are impossible to distinguish by the naked eye except through experience with their symptoms.
(See also the Rodale book recommended earlier in this section .) All such diseases present the problem that once a plant is infected, it becomes a storehouse of infective particles that can be spread to other plants via insects, wind, or handling. The longer an affected plant remains in the garden, the greater the odds that it will infect other plants. Diseases caused by viruses, bacteria, and protozoans are seldom treatable, but sometimes you can save a plant by pruning out the affected portions. Many fungal diseases, though, are treatable through a combination of pruning and spraying.
When a plant infection of any sort is first noticed, you may be able to save the plant by applying compost tea and/or Messenger .
These products can stimulate an immune response that helps the plant overcome the infection. Their usefulness in that regard varies depending on the plants and diseases involved, so try it and keep notes of the results. A number of spray fungicides can also be used.
Common fungicides include copper sulfate, Bordeaux mix (a mixture of copper sulfate and lime), baking soda, garlic oil, and neem oil.
Baking soda is mixed two tablespoons per gallon of water with one ounce of light horticultural oil added, and the others are mixed according to label directions.
Some less well-known antifungal agents can have surprising results. I had a problem with powdery mildew on my lawn last spring (we had an especially wet spring), and I eliminated the infection by spraying with a mix of neem oil and fixed copper.
If saving the plant is either unsuccessful or inadvisable, then the plant should be removed from the garden immediately. Removing an infectious plant can be problematic since it can be covered with microscopic spores that will spread all over the place if the plant is disturbed. The solution is to spray the plant with something that will hold any spores in place and inactivate as many as possible before attempting removal. A good spray for this is made of two tablespoons of castile soap, one tablespoon of copper sulfate, one tablespoon of lime, and one tablespoon of light horticultural oil all mixed together in a gallon of water . The soap and oil will make the plant sticky so that spores can't escape, while the copper sulfate and lime serve to actually kill many infectious organisms. Spray the plant thoroughly with this (though not until it is dripping), and then cut it out and remove it, being as careful as possible to avoid letting it touch any other plants.
When dealing with plant diseases, you should consider your hands and tools to be a mode of disease transmission. When handling known diseased plants, it makes sense to handle only the diseased plants before hand washing and also to immediately sterilize any tools used on the diseased plants with bleach. A suitable sanitizing solution is one tablespoon of bleach per quart of water.
Diseased plant materials can be thermophilically composted with minimal or no risk as long as proper retention times are observed.
If the farmer uses mesophilic composting instead, then diseased plant debris should be burned or placed in the curbside trash. It is also very important not to grow the same family of plant in the same area the next year . If a variety of the plant that resists that disease can be found, it would be a good idea to switch to that variety for at least a year or two, if not permanently.
When Pest Prevention Fails
The best soil management and prevention mechanisms will not be 100% effective against insect pests. For example, naturally attracted beneficial insects exist in balance with pest insects. If the beneficial insects were to eat all of the pest species, then the beneficial insects would starve or move somewhere else, and the pest species would experience a resurgence in the absence of its natural enemies.
Reactive control measures include anything used in the preventive stages, along with importing beneficial insect populations, applying microbial insecticides, and using substances that actually kill insects directly, such as soaps, oils, and natural or synthetic insecticides.
Synthetic insecticides should be reserved as a last resort since they would reduce the healthfulness of the crop (as described later in this section) and would make it impossible for you to sell your produce as organic for several years if you wish to do so.
Both natural and artificial insecticides can also harm beneficial helpers, such as necessary pollinators and earthworms, and disrupt the life of the soil and thus harm fertility in the long run, so they are best employed only when absolutely necessary. Because natural insecticides don't last as long in the garden, they have less potential to do unintended damage.
Microbial insecticides are microbes (or toxins produced by microbes) that are deadly to pest insects but harmless to beneficial insects and humans. They have the advantage of being relatively benign but the disadvantage of being fairly species specific. For example, Bacillus popilliae is deadly to Japanese beetle larvae but harmless to other white grubs that infest lawns. They aren't contact poisons, and they must be eaten by the insect to be effective.
Microbial insecticides have become increasingly popular , even among conventional farmers, and are readily available at agricultural stores.
Soaps and Oils
Table 14: Common Microbial Insecticides
Microbe Pests | Controlled | Notes
Bacillus thuringiensis var. kurstaki
The caterpillar stage of a wide variety of moths Will not control codling moths Bacillus thuringiensis var. israelensis Mosquito, black fly, fungus gnat
Bacillus thuringiensis var. san diego
Colorado potato beetle
Grasshoppers Because of grasshopper mobility, may not work for small yards
Plain old soap (not detergent, but soap) kills a number of insects by dissolving a waxy coating that they need to breathe and preserve moisture. Specialized insecticidal soaps can be used, or else a pure castile soap (such as Dr . Bronner's), mixed two tablespoons per gallon of water . Insecticidal soap will effectively control aphids, white flies, scale, spider mites, and thrips. It needs to be reapplied fairly frequently-about weekly-to interrupt the life cycle of the target pest.
Light horticultural oils are highly refined mineral oils that control the same insects as insecticidal soap by covering and smothering the pest and its eggs. Mix and apply according to label directions.
Both oils and soaps should be tested on a single plant first, then wait a day, because they can be toxic to certain plants. (Their degree of toxicity to plants varies with heat, sunshine, humidity, general plant health, and other factors. Most often, they won't cause a problem, but it never hurts to test first.) Natural Insecticides The fact that something is natural doesn't mean that it is harmless. Ebola, smallpox, and strychnine are all 100% natural, for example. Natural insecticides fall under the same category and thus require care in their use. Natural insecticides can be purchased, or they can be grown and made at home. From a cost standpoint, the latter approach is preferable, though certain natural insecticides aren't practical for home manufacture.
Pyrethrin is a contact insecticide that controls most aphids, cabbage loopers, stinkbugs, codling moths, and white flies among other pests. It does not affect flea beetles, imported cabbage worms, or tarnished plant bugs.
To make your own pyrethrin, grow pyrethrum daisies (Tanacetum cinerarifolium) somewhere in the garden. Cut the flowers when they are in full bloom for the highest concentration of poison, and hang them upside down in a cool, dry, dark place to dry. Once they are dried, take a quart jar of the dried flowers and grind them up using an old food processor or blender that you pick up at a yard sale and that you will never use for food again. Mix it with one gallon of water and two drops of dish liquid, and allow it to steep for three days, stirring every once in a while. When done, filter it through cheese cloth that you will throw away afterward, store in a tightly capped bottle in a cool dark place, and label it appropriately as a poison so nobody drinks it accidentally. You dilute this for use by mixing one quart of the poison with three quarts of water , shaking, and applying via a sprayer . (I cannot stress strongly enough that all bottles containing poisons of any sort be labeled appropriately. Not far from where I live, a child died tragically a couple of years ago because of an unlabeled container of insecticide.) Other natural insecticides are widely available, including neem and rotenone. These can be purchased at most garden centers or via mail order and should be used with as much care and caution as synthetics, because they can be toxic to humans.
While this book focuses on organic methods, synthetic pesticides available to home gardeners bear mentioning. Ideally, because of a combination of growing conditions, attraction of natural predators, and other factors, pests won't be a problem so no pesticides will be needed-synthetic or otherwise. But that's the ideal. Reality can be far different, especially when first beginning a mini-farm. Even the most careful planning won't completely eliminate pest problems.
As a mini-farmer , you are trying to put a lot of food on the table, and you are trying to put safe food on the table. Perhaps, like me, you are an organic purist. But what happens when the theory of being an organic purist runs into the reality of a pest problem that threatens an entire crop? In my case, since I sell my produce as organic at 200% higher rates than conventional produce, it is actually better for me to lose a crop entirely than use synthetic pesticides. But what if my operation were strictly oriented toward putting food on the table? In that case, maybe I would use them, albeit cautiously and as a last resort, because some research shows that the synthetic pesticides available at the hardware store can be just as safe as botanical insecticides-and more effective-when used properly.
Please note that I said "maybe, " "cautiously, " and "as a last resort" for a reason. First off, in a mini-farm established using the methods in this guide, economically threatening insect problems should be rare, and insect problems that won't respond to natural remedies even more rare. In fact, I have had only one pest problem where synthetics would have possibly been the better short-term solution.
Second, the government agencies charged with ensuring the safety of foodstuffs, drugs, and insecticides have a poor track record. For example, an article in USA Today disclosed that in 55% of FDA meetings regarding drug approvals, over half of the participants had financial conflicts of interest serious enough to note.
According to the same article, committees approving such things are actually required by law to include officials representing the industry in question. This is not exactly a recipe that would inspire confidence in most objective observers and perhaps explains the dozens of chemicals (including various insecticides and drugs) approved by government agencies and subsequently recalled after people have been harmed or killed.
Finally, studies indicate that synthetic pesticides make food less healthful by reducing the ability of plants to create antioxidants.
This explains my caution regarding synthetic pesticides. If you are nice enough to buy my book, should I repay your kindness by giving you advice that could hurt you without totally disclosing the facts as I know them? Government agencies have a poor track record, and research in universities is often funded by self-interested parties. The extent to which this affects the results and conclusions of research is impossible to tell. So I am going to give you information on two synthetic insecticides, understanding that the research I have available says they are safe but that it could be discovered later that you shouldn't touch them with the proverbial 10-foot pole.
The use of natural insecticides like pyrethrin and rotenone is perfectly acceptable under the National Organic Program, but in practical terms these substances are every bit as toxic as commonly available synthetics while being less effective in many instances. The main difference is that the natural insecticides break down into nontoxic compounds very quickly under the influence of heat, sunshine, wind, and rain so they won't make it into your food supply if used properly, whereas the synthetics are specifically formulated to be more persistent.
Let's take pyrethrin as an example. Pyrethrin is a natural neurotoxin that insects quickly absorb through the skin. Once it is absorbed, the race is on between the insect's enzymes that detoxify the pyrethrin and the pyrethrin's toxic effects. Many insects, if they receive a sub-lethal dose, will pick themselves up and dust themselves off less than an hour after apparently being killed! Synthetic pyrethrins approach this problem by mixing the product with a substance like piperonyl butoxide that delays the insect's ability to make the enzymes to detoxify the pyrethrin, thus lowering the threshold considerably for what would constitute a lethal dose.
Moreover, semisynthetic pyrethrins, such as allethrin, are often more toxic to insects while being less toxic to mammals (such as humans) than their natural counterparts.
So a semisynthetic pyrethrin spray combined with piperonyl butoxide would require less poison to be used and be more effective, and the type of pyrethrin being used would be less toxic to humans.
According to a metabolic study, neither natural nor synthetic pyrethrins accumulate in the body or show up in breast milk because they are quickly detoxified in the human body.
Any allethrin consumed by a human is rapidly transformed into something less toxic and eliminated.
In addition, allethrin is broken down into nontoxic compounds through the action of air and sunlight within a few days, 32 though not as quickly as natural pyrethrin.
The piperonyl butoxide used to increase the effectiveness of pyrethrins is a semisynthetic derivative of safrole--an oil found in the bark of sassafras trees. It works by inhibiting enzymes that detoxify the pyrethrins in the insect's body. Safrole is a known carcinogen, but the status of piperonyl butoxide as a carcinogen is disputed. Unlike allethrin, piperonyl butoxide is stable in the environment and doesn't break down easily.
Given current information, the allethrin doesn't worry me much, but I am sufficiently uneasy about the persistence of piperonyl butoxide in the environment that I wouldn't personally use it. Either way, synthetic pyrethrins and those containing piperonyl butoxide should be used according to label directions and never be used on crops within a week of harvest; even then harvested crops should be well washed.
Carbaryl (also known as "Sevin") is another common synthetic insecticide used in home gardens. There is no clear evidence that carbaryl is carcinogenic or causes birth defects, and 85% of carbaryl is excreted by humans within 24 hours.
Carbaryl has a half-life of 7 to 14 days in sandy loam soil, and the manufacturer (GardenTech) states that it is not absorbed by the plant.
Therefore, if used according to label directions, and produce is carefully washed, it should be safe. According to numerous studies, "Carbaryl breaks down readily and experience shows it readily decomposes on plants, in soil and water to less toxic byproducts. Accumulation in animal tissues and biomagnification of residues in food chains with carbaryl and its metabolites does not occur."36 Certainly, the preponderance of science says that carbaryl is perfectly safe when used according to label directions. It definitely takes care of cucumber beetles much more effectively than my organic approaches. Nevertheless, common sense and the fact that it is a neurotoxin that takes a lot longer than most botanical insecticides to break down would dictate that it be used only as a last resort. All in all, if I were to use a synthetic insecticide, I would use carbaryl in preference to the others available. And, in fact, that is what I used before switching to organic gardening.
So far, in this section , when discussing pests we've largely been talking about insects. But one ignores larger pests, such as raccoons, rabbits, and deer , at his or her farm's peril. For many years, my farm ran along just fine with only minor damage from moles who ate strawberries and ripe tomatoes, and raccoons who occasionally stole an ear of corn. But one year , my entire crop of beans, sweet potatoes, and Brussels sprouts was wiped out in just one night by a herd of hungry deer . And they kept coming back to nibble at the sad remains. Clearly, action was needed.
Moles can be a bit of a nuisance in my garden. They are there, primarily, to eat grubs. If you get rid of the grubs by applying Milky Spore or beneficial nematodes, you will dramatically reduce the mole population. For faster relief, there are a number of castor oil products on the market that put castor oil into the dirt. When the moles dig, they get the castor oil on their fur , and they lick it off.
This gives them diarrhea, and they move on within a couple of weeks. I've found this quite effective. A number of companies sell a battery-powered spike that generates noise that is supposed to deter moles. These may work for you, but I've found them ineffective.
Rabbits are only an occasional problem and don't usually do much damage on the farm. What I do is mix a hot pepper product with anything else I happen to be spraying and use it to wet the leaves.
This serves as sufficient deterrent.
Deer are another matter entirely. I tried all the standard tricks.
Bars of soap, hair clippings, urinating around the property line, and similar homespun remedies did nothing. Spraying the plants with hot pepper wax was inadequate and only marginally effective. I have found only three things that really work. The first is quite expensive: an impenetrable physical barrier in the form of a fence eight-feet tall. The second is a product called Deer Scram, which is a deterrent scent that is sprinkled around the area to be protected.
The third is the use of a baited electric fence.
A baited electric fence is a regular electric fence that has been baited with peanut butter wrapped in aluminum foil. Deer adore peanut butter , so they put their mouth right on the aluminum foil and get zapped. This works incredibly well and requires only a single strand of fencing about four feet off the ground where pets are safe. This same trick works for raccoons if you add another strand about 18 inches off the ground.