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close this bookThe Biogas/Biofertilizer Business Handbook (Peace Corps, 1982, 186 p.)
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View the documentBioinsecticides
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Bioinsecticides do not come out of biogas digesters, but there is a strong connection between the products of biogas digesters and bioinsecticides.

Bioinsecticides, like biogas and biofertilizers, can be made and used by the people who need them, at a low cost, using local resources. Two of the most important products that farmers use to increase crop production are fertilizers to help plants grow and insecticides to protect the plants from insects.

Bioinsecticides are one weapon in a battle plan of pest control called integrated pest management (IPM). The IPM battle plan has fewer risks and lower costs than total dependency on chemical poison pest control. Groups such as the Peace Corps, Volunteers in Asia, and VITA can provide information on integrated pest management battle strategies and tactics.

A low-cost, safe, and easy-to-use insecticide is what this section is all about, just as low-cost, high-quality fertilizers are one of the main subjects of this book. This bioinsecticide information is adapted from four articles written by Jeff Cox (October, 1976; May, 1977; April, 1978; July, 1979) and one article written by Michael Lafavore (August, 1978) for the "Organic Gardening and Farming" magazine.

From the October, 1976, Article

Frank Batey grows peanuts and soy beans in bug-ridden Archer, Florida. For years he and his father used the chemical insecticides guthion, toxaphene, sevin, methyl parathion, and other insecticides to kill the fierce semitropical insects that would otherwise have destroyed their crops. Today, Batey's fields are crawling with insects, but his crops suffer only minor, unimportant damage. So far he has saved US$ 5,000 in insecticide costs. Best of all, he says, "I do not have to breathe that peanut poison anymore."

Mike Sipe, a pest-control specialist, suggested a simple method of controlling insects to Mr. Batey.

· Go into the fields and collect a cup or two of the insects that are damaging the crops.

· Grind up the insects in a blender with some rain water, strain out the solids, and add more water.

· Put the solution in an ordinary sprayer, and spray the crops that the insects were found on.

So effective has this method been for over two years that in 1976, the third year, Mr. Batey did not even have to spray the bug juice insecticide on his fields.

"We had cabbage looper, stink bug, army worm, velvet bean caterpillar, granular cutworm, southern corn borer, and other pests on our crops," Batey says. "I collected samples of all of them, except for the southern corn borer, which makes a webbed tunnel underground and attacks the pegs of peanuts. It is Just too difficult to find enough of them to make a spray. But on the other pests, the method did a great Job. I am not against using chemicals to help grow food crops, but I hate insecticides and always have. We should not be eating food with these poisons on them. It is important to have good, clean food."

Batey told of a farmer who lives near him. "Last year he used so much insecticide that his peanuts almost died. He came over and looked at our crop. There were ants, earwigs, and beetles crawling around on the ground and on the plants, but none of the major pests. He did not understand what was happening." Batey says his neighbors do not like to experiment with new methods, and so he has not told them about the bug juice method yet. "They would think it is crazy. But I can prove it works. I know it works."

It seems most likely that the bioinsecticides kill insects by spreading diseases that can kill insects. Batey farms 74 acres (29 hectares) of his own land and he sharecrops neighbor Bill Matthew's 39 acres (16 hectares) allotment. "I told Bill that we were going to use the bug Juice to combat insects on his land, and he thought I was crazy. When I sprayed the bug juice on the crops, he thought it was very funny. But in three or four days most of the worms were hanging dead from the leaves or lay dead in the rows. Bill had the worst insect problem I had ever seen, but the bug Juice method took care of it." Batey also farms 100 acres (40 hectares) of soy beans and uses the bioinsecticide spray effectively on that crop, too.

A handful of insects should be enough to spray a large garden. But Mike Sipe has a few important warnings: "In most cases where insects are only doing a little damage, it is best to do nothing. There must be pests for pest-eating insects, lizards, frogs, and birds to eat. When there are too many pests and a crop is threatened, use the bug juice method. It should reduce the pest populations to a safe level but allow enough pests to survive to support a population of the enemies of the pests. Also, make sure that you are collecting only those pests that are threatening to destroy the crops. If you gather harmless insects or insects that eat other insects, you will be upsetting the natural insect controls."

To make sure you have found the real pests, study the plants very closely and watch for the insects that feed on leaves or fruit. If any insect is parasitized (has tiny cottony cocoons of insect-eating insects on its back), do not take it; or you will be making a spray that could kill insects that eat insects.

The results from Alachua County in Florida, a hot weather area where crops are grown all year, are encouraging. Batey's peanut production was 5,251 to 5,351 pounds per acre (6,000 kilograms per hectare) in 1974--a very large harvest that won him the local County Peanut Production Award. Minor insect pest damage had a part in making that record. The average production in Alachua County is between 2,000 and 3,000 pounds per acre (2,200 to 3,300 kilograms per hectare). Batey's chemical insecticide costs were about US$ 2,000 per year, so over the three years that he has been using the bug juice bioinsecticides, he has saved more than US$ 5,000.

From the May, 1977, Article

Safe insect control has always been a goal of farmers, but what is safe for people, is often safe for bugs; and what is dangerous for insects, is often dangerous for people. Is there then, any danger to people from the bug juice bioinsecticide method?

The following comments are from quotes by several plant scientists:

· "The method is definitely safe, but I would still use caution in applying the bug juice. I would rather see people use as little as possible to control insect problems. If all of a pest insect population is killed in an area, the insect's natural enemies might die out too..."

· "I have been working in this area for eight years, and I do not think there is any danger. The only danger I can see is that if the bug juice method does not work, the farmer may never try biological control methods again..."

· "Most people who have worked with insect pathogens (organisms that cause disease) feel that they are safe..."

· "Californians have been using a modified bug juice method for 25 years, collecting sick insects and grinding them up to make a bug juice spray...these insect pathogens are very effective, but this is the first time that using healthy insects has been recommended..."

· "He applied it to his okra (a vegetable), which was infested with five different kinds of caterpillars and army worms. It killed all the caterpillars and worms. I did not believe it at the time and told him I thought he had forgotten to clean the chemical insecticide out of the spray equipment he has used. But he insisted he had cleaned the sprayer..."

· "The use of insect disease successfully and completely controlled the bug problem in a Malaysian rubber plantation."

It seems that the use of bug juice bioinsecticide is safe, according to the scientists we talked to. One said, "If these insect diseases were transmissible, farm animals and farmers everywhere would have been made sick by them many, many years ago." U.S. Department of Agriculture studies have shown that insect viruses (diseases) of common pest insects reproduce themselves only in specific insects.

(According to World Health Organization figures, chemical pesticides poison 500,000 people annually, killing 5,000 people; and most of the victims are in the Third World. Companies regularly sell pesticides in the Third World that are banned in North America and Western Europe because the chemical poisons are too dangerous.)

The following are adapted excerpts from some of the hundreds of letters "Organic Gardening and Farming" magazine received after the October, 1976, report on the bug juice method.

"I had scale infection on my plants, so I scraped, with difficulty, about a teaspoon of scale into my blender, added water; and after blending, I diluted the mixture with more water and sprayed the solution on the plants. For three days I did not mention my experiment to anyone. When I told my husband and we went to inspect, I was very happy. A shake of a branch or a push on a pile of scale caused the scale to fall off. Scale, I have read, does not fall off. I guess the remains on the plants are as dead as the scale I shook off. The insect-eating praying mantis bug that lived on one plant was not harmed by the bug juice spray, which would have been true with a chemical poison..."

"I noticed my Chinese celery cabbage beginning to wilt. I pulled one up and found most of the roots badly eaten by some kind of white maggot (wormlike larva of a fly) and by wireworms. There were also slugs on the leaves. I collected some of the slugs, maggots, and worms, blended them with a cup of water and poured (not sprayed) a diluted mixture on the plants very slowly, so that the bug juice ran off the leaves and down around the roots. There was no more wilting, but after heavy rains a week later, the maggots started to come back. Maybe the rains reduced the effectiveness of the bug juice over time. But I believe the method worked very well."

Do not use the bug juice method against ticks, fleas, mosquitoes, or other insects that attack people, because these insects can carry human disease. The diseases of plant-eating insects are everywhere in the world. They are all over the leafy vegetables that we eat, and we have been constantly exposed to them for millions of years on the foods we eat and in the gardens and fields we work in. If plant insect diseases could make us sick, we would have them by now.

The most important part of making bug juice is the collection of enough pest insects to increase the chances in favor of spreading an inactive insect disease. The amount collected in weight is not as important as the number collected. For example: if 300 insects are collected and only one tenth of the blender concentrate is used to make a dilute solution, success will be ten times more likely than if only 30 insects are collected and all of the concentrate is used to make the dilute solution.

The reason for this is: even if there is only one sick insect in a batch, its disease will be spread throughout the dilute solution. That one sick insect can be the source of 1,000,000,000 (one billion) virus spores (a "disease seed"). This means that when those virus spores are spread evenly over the leaves of a plant, almost all of the insects will eat some spores. Many of these insects will be killed by the virus. Each pest killed in this way will provide many more virus spores in the weeks to come.

If any pest insects look weak or are moving slowly, they may be sick and should definitely be used to make a bug spray. Three or four days after a solution has been sprayed on the plants, look for dying pests. These insects should be collected and stored in a jar in a freezer or dried slowly at about 38 degrees centigrade (100 F) for four to five hours and then stored in an airtight container until needed. These stored insect pests can be saved until the next crop or shared with a friend who is having trouble with the same pest.

Do not expect to control one kind of insect by grinding up and using another kind of insect in a spray. Each insect carries diseases that harm no other kind of insect. Only a few kinds of insects can be killed by diseases that affect other, even closely related, insects. Do not expect to control aphids with ground up corn earworms.

If ground up bugs are saved for use at another time, keep some record of what insects went into the bug juice solution. A simple way to do this is to place two or three of each kind of insect in a jar of 70 percent isopropyl alcohol (rubbing alcohol). Label the jar as to when the insects were collected, off of what kind of plants they were collected, and how many of each kind of insect was used in making the bug juice concentrate.

If the pest shows up again, the insects on the crops can be compared with the ones in the bottle of rubbing alcohol. The insects in the alcohol cannot be used in a bug juice spray; they are for identification purposes only. Only the dried or frozen concentrate can be used to make a dilute solution for spraying. Pest insects in jars of rubbing alcohol would be a good way for stores that sell bug juice bioinsecticides to advertise which insects they have frozen bug juice concentrate for.

The following precautions are based on the idea that too much safety is better than too little safety. Wash your hands after handling the insects. Use drinking quality water to dilute the concentrate. Sterilize a blender after using it to grind insects by placing the non-electric blender parts in boiling water for 15 minutes after they have been cleaned. Do not breathe the spray. Wash fruits and vegetables before eating them if the spray has been used recently. These precautions should be followed much more carefully when chemical insecticides are used.

From the April, 1978, Article

The bug juice method of insect control proved its worth last summer, according to reports from "Organic Gardening and Farming" readers and newspaper accounts from around the country. The bioinsecticide method was successfully used on an 80 hectare (200 acre) peanut and soy bean farm in Florida, when first reported in this magazine's October, 1976, issue. Now there are reports from many areas of the country saying that it works.

Two letters were received saying that it did not work. One man tried it on grasshoppers, and a woman tried it on Japanese beetles, both without success. The bug juice also failed to kill Japanese beetles on grapevines when "Organic Gardening and Farming" staff tried it, but the bioinsecticide did clear up infestations of aphids on corn. (Other scientifically controlled experiments have been very successful in killing Japanese beetle grubs with a bug juice insecticide. The scientists made sure that the grubs they used were sick with milky spore disease.)

Warning: There are some plant diseases, such as the rice plant virus called tungro in the Philippines, which are carried from plant to plant by insects, in the case of tungro by leafhoppers. Do not use the bug juice method if the crop is sick with a plant disease. Using the bug juice could spread the plant disease. Use the following plant juice method when plants are being eaten by insects and may also have a plant disease.

Sprays that spread insect diseases may not be the only effective biological blender spray. The magazine "Soil News" from September, 1977, reports that blending weeds that insects will not eat and then spraying a diluted solution on crops that insects love to eat is an effective way of protecting crops. Plants that insects refuse to eat contain distasteful substances that when sprayed on tasty crops, makes the tasty crops just as impossible for the bugs to eat as are the never-eaten weeds.

One letter writer said he collected the leaves from plants that insects never seem to eat, ground them up, made a tea with water from the solution, and sprayed it on his garden. "When I checked the garden a few days later, I swear I could not find a moth, bug, or worm of any kind under the leaves, on top of the leaves, or on the ground. The bugs had said ugh and silently crawled away."

Find weeds and tree leaves that insects never eat, as indicated by a lack of holes in the leaves.

· Grind them up in a blender with a little water, add some more room temperature water, not hot water, and let the solution sit for 24 hours.

· Then strain, dilute, and use as a spray on vegetables and other crops.

· Do not cook the solution, let the ground-up leaves just soak in water like a tea for a day before straining, diluting, and spraying.

· Do not dilute the solution more than five times the original volume.

· Smooth leaves are more likely to have chemicals that taste bad to insects than "hairy" leaves because hairy leaves repel insects mechanically.

· Choose plants like pines, poplars, and herbs that are not poisonous, yet contain volatile oils.

It is very possible that whatever insects do not like about one plant might make them hate another, different type of plant, if by using a spray made from the first plant, the second plant can be made to taste like the first plant.

There have also been reports that using a plant juice solution made from weeds might stop the growth of more weeds of the same type. There is very little information on this idea of killing a weed by spraying it with a "tea" made from its own kind. It may not work, but it is worth experimenting with.

One plant spray that has met with success is the hot pepper spray made from grinding up hot peppers and diluting the concentrate with water. There are reports of hot pepper spray stopping rats, mice, and some kinds of insects from eating plants. From Papua, New Guinea, comes the suggestion to add a little liquid or powdered soap to the solution (make sure it dissolves). The soap will help the pepper spray stick to the leaves.

From the July, 1979, Article

The bug juice method works successfully on over 20 pest insects, including: cabbage loopers, grape skeletonizers, stink bugs, armyworms, velvet bean caterpillars, granular cutworms, ants, slugs, fungus gnats, sawfly worms, aphids, wireworms, striped potato beetles, and several types of caterpillars.

The Center for Tropical Agronomy in Turrialba, Costa Rica, reported that insect populations in bean plots sprayed with bug juice were very low (one or two insects per 12 foot row), while the untreated plots had normal insect populations (four or five insects per plant). There was a need for once a week reapplication until pest levels decreased permanently.

The bug juice method is not totally understood yet. Sometimes it does not work as well as was hoped. Sometimes it does not work at all. One scientifically controlled study showed that cutworm bug juice, which has worked successfully many times, actually attracted cutworms. (Maybe the insects were collected during their mating season and were releasing chemicals meant to attract others of their kind. When the bug juice spray was made, these chemicals naturally enough ended up in the solution.)

The usual difference between success and failure with bug juice is whether or not any sick insects are used in making the solution, It is not always easy to see if an insect is sick, so all pest insects of the kinds wanted should be collected, in hopes that some of them will be sick.

More information on the "plant" juice spray: Certain chemicals in plants may serve as barriers to plant-eating insects. If those chemicals are put into a solution and sprayed on crops, the bugs will look elsewhere for food.

The neem tree of India is reported to have a taste that insects hate to eat, and some pine tree needles contain chemicals that can kill houseflies, codling moths, and apple moths.

Healthy plants in a healthy soil will attract few insect pests. More insecticides are needed to control insects when a crop has been given too little or too much fertilizer. A balance of plant nutrients in the soil grows plants that are resistant to insects, just as people who eat well do not get sick as often as people who do not eat well. Rotate crops, use biofertilizers and chemical fertilizers wisely, and less insecticide of any kind will be needed (August, 1980).

From the August, 1981, Article

The history of organic pest control is one of trial and error, success and failure. Gardeners and farmers have planted aromatic herbs and flowers to ward off bugs. They have planted several different vegetables in the same plot to confuse insects. They have tried to disguise their vegetables with sprays made from plants which bugs seem to avoid. They try to kill insects with sprays made from grinding up the insects themselves. Sometimes these measure work, and sometimes they do not work.

Do not let the fact that all attempts have not met with success stop you from trying. Try several small-scale experiments of the methods described here. Ideas that do not work can be easily dropped; ideas that do not work as well as one would hope can be improved on; and in the end large-scale safe, low-cost biological control of insect pests can be done successfully with confidence.

One man who successfully uses bug juice bioinsecticides does not separate the bugs from the leaves. He collects several leaves that are covered with aphids; then he grinds up the leaves and the bugs together in a blender and sprays a diluted solution back onto the vegetables. In one day he reports many of the aphids are gone; in three days they are all gone.

Pill bugs and slugs are not insects, but the bug juice method has been used successfully against them. However, more than one spraying is often necessary.

Bug juice has been used to treat soil planted to squash and beans.

· An ounce of ground up pill bugs (root-eating soil pests) was mixed with two ounces of water to make a paste and then diluted, one ounce to a gallon of water (three milliliters to 3.78 liters of water).

· One section of land was soaked with the solution; the other section was soaked with plain water,

· Two days after sowing, the seedlings came up. The roots of the plants in the untreated section were eaten by pill bugs on the first night, but the roots of the plants in the section watered with bug juice were not eaten.

A few warnings:

1) Bug juice bioinsecticides can quickly lose their effectiveness by becoming spoiled with bacteria; in other words, bug juice can rot. Use all of it right away or freeze the remainder. The only possible danger with the bug juice method is to let it sit out and become contaminated with salmonella bacteria as it decays.

There is no danger to people if the bug juice is used within an hour or two of being made or if the unused portion is frozen. Since the concentrate can be diluted up to 25,000 times, it is a good idea to freeze some for reuse after a rain.

2) Some people develop allergies when working with insect parts. If this starts to happen, wear a mask, long-sleeved shirt, pants, and gloves when spraying with bug juice.

3) Do not use the bug juice method against fleas, ticks, mosquitoes, and other insects that attack people and may carry human disease.

4) If a grinder is used to grind up the bugs, use that grinder only for making bug juice. If a blender has to be used to prepare food for people, use a mortar and pestle to grind up the insects.

Directions for making and using bug juice bioinsecticides:

1) Check for damage. Do not use the method if the crop is not being seriously attacked. If there are only a few pest insects, then there is a balance between insects that eat plants and insects that eat insects. Do not upset this balance.

2) Identify the pest insect. If the crop is being attacked by a pest, identify which insects are doing the damage. It is important not to kill insects that are not major pests. They provide food for insect-eating insects, birds, and animals.

3) Collect the pest insects. Collect as many insects as can be found in 15 minutes or at least 100 insects of each type for every five hectares (12½ acres). Protect the insects from the sun; they will not make a good bug spray if they die before being ground up.

4) Put the insects in a blender. Cover the insects with a cup of two of rain water or boiled water that has been allowed to cool. The volume ratio should be about one third insects to two thirds water. Run the blender at high speed until the solution is all liquid. This should take about one minute.

5) Strain the solution through cheese cloth, a paper filter, a clean rag, or towel. This will prevent the sprayer from becoming clogged with small insect parts.

6) Dilute the concentrate solution. For gardens, use a small hand sprayer, the degree of dilution is not critical. Dilute one quarter cup of concentrate with one or more cups of rain water or boiled water that has been cooled. Freeze, do not just refrigerate, the rest of the concentrate in small batches in case repeat sprayings are necessary.

For farms, a dilution as weak as one ounce (30 milliliters) of concentrate in about 100 gallons (378 liters) of rain water has worked. (Liquid soap, corn syrup, or other sugars that dissolve easily in water can be added to the solution to help the spray stick to plants.)

7) Spray the crops with the diluted concentrate. Use a standard insecticide sprayer to spray bioinsecticides. Spray both sides of the leaves and spray the stems, too. If a rain occurs soon after spraying, repeat with the solution that was frozen or make a new batch. Even if it does not rain, it is not unusual for repeat sprayings to be necessary.

8) Check the plants before spraying, in a few hours after spraying, one day, three days, and one week later to see what is happening to the pest insects. Some effects may not show up until a few days or weeks after spraying, depending on the type or types of insect disease or parasite that is in the bug juice; so keep watching.