Hawaiian farmer Jon Biloon recently wrote an article published on farmingsolutions about rebuilding health and fertility of soil in the Pacific. Here he presents his experience of controlling problem pests in the region without the use of toxic chemicals.

Summary
The Pacific Island region supports unusually high pest loads - both native and introduced - due to its diverse environments and year round growing season.

Years of monoculture, coupled with the use of chemical pesticides, have resulted in the loss of soil fertility, making it difficult to grow clean and healthy crops. This has created a problem given that the market now demands an ever-greater focus on the value of a clean environment and safe food. To meet this demand it is clear that farmers must use sustainable strategies to control pests, thus reducing the application of toxic and often dangerous chemicals.

Sustainable farming is a total system that seeks to re-establish a more natural mechanism for growing healthy crops. This system recognises that all living things are connected, and that by working within natural cycles less effort is expended and yields are increased - less costs and more profit.

Sustainable agriculture embraces Integrated Pest Management (IPM) practices. IPM is a strategy that seeks to minimize damage to plants by careful observation and monitoring, predicting trouble before it happens, and then choosing the least toxic controls. IPM requires the farmer to study and understand the plant’s environment, and monitor closely the life in the orchard, field or garden. IPM also requires that a farmer understand the wide range of options that are at his disposal.


Problems

1) Weeds
Weeds are plants out of place, competing with cash crops and reducing yields. Sometimes weeds can make it almost impossible to grow crops. In pastures weeds are the inedible plants animals cannot eat and so they reduce the amount of forage available for consumption. Weeds can also make it more difficult to harvest a crop. Vines and tall weeds in coffee fields and thick weeds under mac-nut trees increase picking times and some weeds use up valuable nutrients from crops and reduce available sunlight.

2) Insect Pests
Insects can cause severe damage to crops. They are most likely to attack plants that are stressed by poor fertility, drought, over-watering and other, often solvable problems. The Pacific Island Region also suffers from introduced insects that have no natural predators. Monoculture, still encouraged by some, has been found to encourage considerable damage by insects.

a) Above ground insect pests

Sucking insects
Sucking insects are insects that cause damage by sucking fluids from plants. They usually do not move around very much and can cause damage in a number of ways. Sucking insects dramatically slow down the growth of plants, damage new and old leaves, spread viral diseases and cause fungus and bacterial diseases. These pests include aphids, scale, meally bug, white fly larva, leafhoppers, spidermites, spittlebug, stink bug and thrips.

Chewing insets
Chewing insects actually take bites out of our plants, and can very quickly cause serious damage to crops. These include larvae of caterpillars and moths, cut worms, rose beetles (at night), larvae of other beetles and cutworms. These insects can move around and evidence of their damage can be very clear.

Borer and miners
These insects cause damage inside leaves (leaf miner), stems (stem and vine borers) and inside fruit (larvae of fruit flies). Farmers must be observant with regard to these pests – as economic loss can be considerable.

b) Below ground insect pests

Grubs
These larvae of beetles can do considerable damage to roots of host plants but it is the chewing damage by adults that is most obvious, grubs can also cause damage to grasses and turf.

Nematodes
These are tiny soil worms that can cause a great deal of frustration for the tropical farmer as most plants can be effected by one or more species. Symptoms of nematode damage include malformed leaves, stems and roots; dwarfed plants and wilting. Some endoparasitic (living within the root) nematodes cause the classic gall or root knot that blocks nutrient uptake and allows for infection of other disease organisms.

C) Microbial Pests
Virus disease
Viruses can be extremely damaging to crops such as papayas, bananas, tobacco, peppers and other fruits and vegetables grown in the Pacific region. While sucking insects spreads most viruses, some are spread by air. Viruses cause the loss of green in the leaves, reduce the sugar content of fruit and can kill off whole crops. They must therefore be taken very seriously.

Fungal Disease
Fungi can cause different diseases such as sooty mould, powdery mildew, fungal blight, root rot, damping off, anthracnose, rusts, leaf spot, fusarium wilt, Phytophthora, pythium and watery soft rot to name a few. Problem fungus’s can spread rapidly and cause considerable damage to a crop.

Bacterial disease
Bacterial diseases are usually foul smelling and can spread easily. Damage and wounds caused by insects and animals are the most common reasons for infection. High moisture also makes it easier for bacterial infections.

D) Animal Pests
Pigs, feral sheep, horses, deer, dogs, cats, mice, rats, birds, mongoose and many others can quickly cause considerable damage to a crop.

E) Toxic herbicides, insecticides and fungicides
The conventional approach of killing weeds with expensive toxic chemicals can also create problems. Herbicides can kill or injure other plants and animals besides the targeted weed. Certain herbicides can also kill beneficial soil organisms and reduce organic matter in the soil. This creates extra problems in the long term, such as loss of topsoil, increased fertilizer rates, increases in insect damage and fungal problems. The problems and costs to our society, associated with chemical herbicide use, far outweigh the financial gains made by conventional farmers and amount to a subsidy for their use.

Pesticide chemicals used by conventional agriculture are as much a part of the problem as the pests they seek to control. Use of insecticides kills both bad and the good (beneficial) insects. Beneficial insects are extremely important in controlling other insects in nature, so the spraying of a toxic chemical to eradicate a specific insect will therefore often lead to an increase in insect problems in the long-term. Similarly, fungicides kill both good and bad fungus. Beneficial funguses have been proven to be an important link in maintaining healthy fertile soil and in providing nutrition to crops.

Pesticides – counting the costs
Herbicides, insecticides, and fungicides can have a very dangerous effect on human health. Insecticides are the same class of chemicals that are used as nerve agents in chemical warfare. They are nerve toxins that can cause irreparable harm to the public, especially the young. Use of chemical pesticides also pollute the near shore environment and contaminate public drinking water. Insecticides, herbicides and fungicides can also leave toxic residues on our food and their combined effects can be extremely dangerous, leading to a plethora of acute and chronic diseases. When the costs of the above are taken into account there is no economic benefit in the use of these chemicals; they cause more economic and social harm than any possible benefit.

The mistakes that have been learnt from the inappropriate use of pesticides are today becoming tools that can be used to generate farming solutions based on safety and sustainability. By working with nature farmers are recognising that they can both increase their returns and protect public health and the environment at the same time.


Solutions

1) Weeds
It must be understood that plants in an orchard only become weeds when they impact negatively on the growing of primary crops. Just because a plant is in an orchard shouldn’t make it the target of expensive and toxic herbicides.

Desmodium is a weed to many in Hawaii, yet to others it is excellent ground cover, fodder for grazing animals and a source of free nitrogen. It is also a good place for beneficial insects to live that will in turn protect the primary crop from disease. Many also consider blue Vervain a weed, yet it is a valued medicinal herb sold in health food stores. It is therefore quite possible that what is considered a pest may have economic value as a crop.

Weeds are an indicator of soil health - proper pH adjustment and mineral balancing can reduce the impact of weeds on a farm.

Even when weeds need to be controlled, toxic chemicals can still be avoided. There is an herbicide on the market that is made from synthesizing a chemical found in a certain soil bacteria. ‘finale’ kills most weeds like conventional herbicides yet is said to break down to water and carbon dioxide, leaving no residues, yet there is evidence that exposure to the active ingredient in ‘finale’ can cause major health problems. Another problem with using this product is that the bare ground it leaves is the perfect place for more weeds and soil erosion and it can create a dependency if a ground cover is not established.

Ground covers
Planting ground covers is the best way to reduce dependency on herbicides. Ground covers are any plant or plants that do not interfere or help with the growing of a crop. Ground covers are controlled by grazing animals, mowing, cutting and weed-eating. The extra time spent establishing proper ground cover will eventually be much more beneficial and cost effective than the perpetual use of herbicides. Help in deciding what the best ground covers are in a specific area can come from soil conservation representatives or agricultural extension agents.

Other ground covers include cinders and ground rock. These types of material are excellent around the base of trees in an orchard or between the rows of a raised-bed garden.

Solarization and weed mats
In sunny locations, solarization is an efficient way to kill weeds and weed seeds before planting. Simply lay 2 sheets of clear plastic sheeting over the ground. The area needs to be watered thoroughly before covering in order to reach high enough temperatures to kill the weeds. It may take 1 to 2 weeks but this method is very effective. In areas without hot sun, covering with one sheet of black plastic, or even cardboard will effectively kill off the ground cover in about a month, but not all seeds. There are also weed mats that can be placed semi-permanently in an orchard or garden, but care must be taken so that weeds don’t get established on top of them (a little attention once a month is all it takes). Burning can also be a very effective method of eliminating weeds.

Corn Gluten
Sometimes, in certain plantings, weeds from wind blown seeds can cause a lot of damage. The easiest way to control this problem is using Corn Gluten which, besides being an excellent fertilizer source (9-0-0) will prevent seed germination for up to 3 months when applied at a rate of 800lb/acre. This is a great product for established lawns and orchards where you do not want any seeds to germinate, also in vegetable/herb operations where there is no direct seeding into the garden.

The best way to control weeds though is just not to let them get in control. This can be done with proper cultivation techniques, for example waiting to plant seeds or starts in the garden until weeds start to grow and then turning them into the soil when they are about an inch high. If this is done 2 or 3 times before planting, plants will not have as many weeds to compete with. It seems weed problems increase in the tropics as soil acidity increases. Acidity in soil increases with lack of air (compaction), standing water in the surface layer, cultivating too wet a soil, insufficient cultivation, insufficient drainage, using the wrong kinds of fertilizers (acid-chemical) that cause erosion and loss of humus.

2) Insects

Integrated Pest Management
Integrated Pest Management (IPM) is the principle that guides sustainable farmers as they attempt to solve the problem of insect pests. It is time to spray when evidence or damage of pests is visible, so one must be observant and recognize problems in their earliest stages. Most above ground pests can be controlled with the use of botanical sprays containing pyrethrum, rotenone or neem oil, individually or in combination. These types of sprays control insects pretty much on contact but these sprays will also kill beneficial insects, so care should be taken.

Sustainable agriculture recognizes that most insects are good, and in fact, beneficial insects can keep pest insects under control. The ability of parasitic wasps to control fruit flies is a good example of how beneficial insects can solve a pest problem. Other beneficial insects include Lady beetles, green lacewings, seraphid fly, praying mantis, and larger wasps.

Soaps and oils
Use of insecticidal soap can also control most above ground insects, especially sucking insects, yet do little damage to beneficial insects because they can move out of the way quickly.

Light oils, like paraffinic oil are also very effective at controlling insect pests. In the case of borers and leaf miners increasing growth rates and sap flows with fertilization and watering will be more beneficial than using toxic controls.

Bt
One of the more interesting controls is the use of Bt, a bacteria specific to caterpillars, making them stop eating the crop and then die without impacting on any other insects. This product is effective for almost all larvae (worms) of moths and butterflies.

Collecting the offending bugs by hand, blending them in water and spraying the mixture (bug juice) on crops can also be an effective means of control, it is especially efficient if you use scale killed by fungus. This juice will infect all the scale with disease without harming beneficial insects.

Ants
Certain sucking insects are tended to by ants that collect their “honey-due” as food. To effectively control these insects, which can be scale or aphids on citrus or coffee and meally bugs on palms, it may be appropriate to put a sticky barrier around the bottom of the tree to discourage re-infestation by the ants. Using baited traps (with borate baits) can be an effective way to reduce ant populations.

Lights
The use of light floating row covers is also an excellent way to protect your crops from insect damage. Below ground pests like Japanese and rose beetle grubs (evidence of night beetle damage on leaves and brown patches in turf) can be effectively controlled with a milky spore virus applied to the ground or turf where you think the grubs are living. Also, light applications of diatomaceous earth to leaves can discourage all chewing insects.

Controlling nematodes
Nematodes are a major problem in the tropics and are a major reason farmers should never bring soil or plants possibly infected by nematodes onto their farm. If nematodes are suspected high levels of organic matter will control them. Nematode control centres on chitinase fungi and soil bacteria, which are organisms that digest chitin (shells of insects). One form of control is the direct application of chitin (shrimp and lobster-meal are excellent forms of chitin). As the bacteria that digest chitin proliferate they kill of the nematodes. A product developed and sold specifically for that purpose is sold as ‘Chitosan’. High phosphate bat guano (composted digested insect parts) used as an inoculant can also help control these pests.

The sesame plant is also very effective at controlling nematodes. ‘Neotrol’ is the name of a product made entirely from sesame that is sold for this purpose. Neem cake added to the soil can also effectively control nematodes (Neotrol and neem cake are also good sources for plant nutrition) and solarization also controls nematodes and sterilize the soil..

Companion plating
Planting in a polyculture is also a good strategy to confuse insects because insects love a monoculture. It is therefore helpful to use companion planting; farmers can plant companion plants that act as a repellent like marigolds repelling the cabbage moth from laying her eggs. Plants can act as a trap allowing the grower to both witness and remedy insect problems before they get to the primary crop For example fruit flies will spend their nights on corn plants, where they can be controlled before they damage your fruit. Nasturtiums are an indicator of aphid problems and Amaranth for spider mites. It is basic common sense that by planting a cover crop that is liked more by insects a farmer will avoid major damage to the primary crop (e.g. aphids on desmodium in a citrus orchard). Nematodes can be controlled by planting nematicidal marigold, which becomes a most beneficial weed in the carrot or beet patch.

3) Microbials
Root fungus and bacterial soil disease is best controlled by proper cultivation and by not allowing free water to develop in the garden. Diseased plants must be removed immediately as problems can be spread quickly and a different type of crop should be planted until the problem is solved.

That is why good fertile soil is the goal of sustainable agriculture. A good healthy soil, full of beneficial organisms and properly balanced can absorb four times as much water as conventional soil before it becomes water soaked. Healthy soil also drains more efficiently, reducing the threat of fungal or bacteria problems. If a problem is suspected, well-made compost full of friendly microbials will usually help correct future problems. There are also specific microbial anti-fungal preparations on the market such as “soil guard” by Trilogy corp. that are quite effective.

Healthy well-balanced soil with good drainage is really the key to controlling soil born fungus and bacteria. It has been proven that the use of soluble high nitrogen chemical fertilizer can cause fungal problems and its use must be avoided.

Sooty mould caused by the honeydew of sucking insects can only be controlled once you solve the insect problem. Powdered sulphur, micronised copper, and copper sulphates are very effective products on most above ground fungal problems like anthracnose. To be really effective regular spraying following product label advice should start before a problem is seen.

Powdery mildew can be controlled quite effectively using a spray made from two tablespoons of Parafinnic oil and two tablespoons of baking soda per gallon of water. Two applications over ten days should work quite well.

A virus is impossible to cure once a plant is infected. If a virus is suspected all diseased plants must be removed and buried and it is also wise to remove and bury surrounding plants. If the threat of a virus is real, the best way to keep it away is to grow healthy plants and discourage transmission using plant protectants such as polymer coatings or parafinnic oil mixed with repellents and applied regularly. These sprays should contain a high quality potassium salt of humic acid as this substance has been proven to stop the transmission of tobacco mosaic virus.

4) Animals
Fences, netting and traps should be used as much as possible. Poisons should be used as a last resort and applied in such a way they do not injure untargeted animals. The use of light floating row covers over just planted corn seed or other vegetables is an easy way to discourage bird and rat damage to tender seedlings.

Conclusion
Pesticides and herbicides kill all living things. They do not distinguish between pest organisms and beneficial organisms. By killing beneficial insects and organisms their use cripples the natural system hampering efforts to grow healthy crops. It is therefore essential to understand the importance of the polyculture and the use of short crop rotations to reduce weed, disease and pest problems.

Sustainable farmers understand that diversity builds stability and that all living creatures large and small are interconnected. Certain elements prepare the way for a healthy crop and encouraging natural cycles will lead to higher yields and less work. Sustainable farmers have learnt from the mistakes of decades of chemical farming. When it comes to developing the least toxic strategy for controlling pests, farmers must take into account the importance of thoughtful observation as opposed to thoughtless application of toxic inputs as the key to their success.

Source: Jon Biloon, ‘organic agriculture for the pacific’ - presentation to agricultural conference, Thailand, July 2003