Biological Pest Control
What is Biological Pest Control?
Biological control is, generally, man’s use of a specially chosen living organism to control a particular pest. This chosen organism might be a predator, parasite, or disease that will attack the harmful insect. It is a form of manipulating nature to increase a desired effect. A complete Biological Control program may range from choosing a pesticide, which will be least harmful to beneficial insects, to raising and releasing one insect to have it attack another, almost like a “living insecticide”.
What are the advantages of biological pest control?
- Biological control methods can be used as part of an overall integrated pest management (IPM) program to reduce the legal, environmental, and public safety hazards of chemicals.
- It may be a more economical alternative to some insecticides.
- Some biological controls are often very specific for a particular pest. Other helpful insects, animals, or people can go completely unaffected or disturbed by their use.
- There is less danger of impact on the environment and water quality.
What are the disadvantages of biological pest control?
- It takes more intensive management and planning.
- It can take more time;
- It requires more record keeping, more patience, and sometimes more education or training.
- Successful use of biological control requires a greater understanding of the biology of both the pest and its enemies. Many natural enemies are very susceptible to pesticides, and using them successfully in an IPM program takes great care.
- In some cases, biological control may be more costly than pesticides.
- Often, the results of using biological control are not as dramatic or quick as the results of pesticides use. Most natural enemies attack only specific types of insects-unlike broad-spectrum insecticides, which may kill a wide range of insects. Though often an advantage, this can also be a disadvantage.
Three main approaches to biological control: Biological control uses naturally occurring predators, parasites and diseases to control pests. There are three main ways to use these natural enemies against unwanted insect pest populations.
Classical biological Control (Importation): It involves traveling to the country or area from which a newly introduced pest originated and returning with some of the natural enemies that attacked it and kept it from being a pest there. New pests are constantly arriving accidentally or intentionally. Sometimes they survive. When they come, their enemies are left behind. If they become a pest, introducing some of their natural enemies can be an important way to reduce the amount of harm they can do.
Augmentation: It is a method of increasing the population of a natural enemy that attacks a pest. This can be done by mass producing a pest in laboratory and releasing it into the field at the proper time. Another method of augmentation is breeding a better natural enemy, which can attack or find its prey more effectively. Mass rearing can be released at special times when the pest is most susceptible and natural enemies are not yet present, or they can be released in such large numbers that few pests go untouched by their enemies. The augmentation method relies upon continual human management and does not provide a permanent solution unlike the importation or conservation approaches may.
Conservation: Conservation of natural enemies in an important part in any biological control effort. This involves identifying any factors that limit the effectiveness of a particular natural enemy and changing them to help the beneficial species. Conservation of natural enemies involves either reducing factors that interfere with the natural enemies or providing needed resources that help natural enemies.
Biological control: application of natural enemies
Increasingly, natural enemies of pests are being produced and sold as least toxic pest management tools. As the use of these products becomes more widespread, the need for an understanding of how to best use these products is becoming more acute.
If a decision has been made to use natural enemies to control pests, several considerations need to be made before proceeding. First, find a source of high quality natural enemies.
Biological Control: Second, consideration should be made of how best to apply or release the natural enemies. A number of challenges and limitations are posed when biological control is incorporated into a pest management program. This publication gives tips in increasing the effectiveness of natural enemy applications. The failure of control is not unique to natural enemies.
The use of pesticides also involves challenges and limitations that can lead to product failure or poor performance. For example, it is important to match pesticides with target pests that they will kill, and that the target pest is not resistant to. Pesticides need to be applied at the correct rate. Compounds should be avoided that may affect growth/survival of plants and other non-target organisms (e.g. birds, fish, pets, people). Safety practices should also be carefully thought through since pesticides are poisons. Environmental conditions such as temperature, rainfall, and wind can all affect the quality and undesired effects of pesticides applications. Finally, it is important to make sure the pesticide actually gets to the targets pest.
Biological control can be an effective, environmentally sound method of managing pests. However, when using natural enemies in your garden, farm, home, or interior-scape, identify the pest and natural enemies, estimate the population of pests and natural enemies, purchase the correct natural enemies, release them correctly, and monitor the effectiveness of the natural enemies.
Identify pests and natural enemies: Accurate identification of pest problem is even more important with biological control than with insecticides, because natural enemies often will attack only specific types of pests. There are resources available to help you do this.
Are natural enemy releases appropriate for your situation?
As with other pest management methods the success or failure of biological control can be determined by the population levels of pests at the time natural enemies are applied. For example, if a pest population is too high, the natural enemies you release may not be able to act quickly enough to protect your crop. In this case, a pesticide with a short residual life may need to be applied prior to the introduction of natural enemies. If, on the other hand you have a very small infestation in your plants, you may not have to do anything of naturally occurring natural enemies are already present. Another approach to take in this case might be spot treat (with pesticide) only infested, areas, rather than spending the time and money to treat your entire crop/garden.
Usually, natural enemies work best as a preventative pest management method. That is, if they are introduced into your crop/garden before a pest infestation, they can prevent that population from developing to damaging levels. If you wait until pests have become a problem before releasing natural enemies, they usually will not work. Therefore pest problems must be anticipated and planned for by carefully monitoring for pest population development. There are well-established monitoring or sampling and record keeping methods developed for a wide variety of pest and crop situations that Information on these methods can be obtained from your supplier of Country Extension agent.
Selection and purchase of natural enemies: Once you have determined the specific pest problem you are faced with, and the appropriateness of using natural enemies the next step should be selection of specific natural enemies and a supplier. Like purchasing any product, you as the consumer are responsible for determining the appropriate ones for your specific needs. Names, addresses, and telephone numbers of suppliers can be obtained from the sources listed at the end of this publication. When selecting a supplier. You should ask a number of questions to help you find the best supplier for your needs. A competent supplier can provide you with information on which natural enemies you should use.
Handling of natural enemies after arrival: Specific handling instructions should be provided prior to or at the time of arrival of your natural enemy shipment, and should be followed carefully. In general, it should be kept in mind that many natural enemies are tiny living insects and mites. They should be kept under relatively cool conditions (room temperature) and out of direct sunlight. If the material arrived in an insulated container, it should probably be kept there until you are ready to apply/release it. Usually, the sooner material can be applied after arrival, the better. For example, some predatory mites are shipped with a small food supply. Once that food supply is exhausted, they feed on one another or starve.
How many natural enemies to release?
Here again, your supplier should provide detailed instructions regarding the “rate” that natural enemies should be applied at. Usually this is expressed as a number of natural enemies per a given “unit” such as: infested leaf; plant; square ft; or acre. As with traditional pesticides, the recommended rate should be followed very closely. Any questions that may arise regarding application numbers can be directed to your supplier or County Extension Service agent.
Timing of releases/applications:
Timing of natural enemy release is critical to the success of biological control. Since natural enemies work better as a preventive rather than curative pest management method, it is important to release them when pest infestations are just beginning. Sampling methods and materials for specific pests are often readily available from suppliers, but if they are not your County Extension agent can assist with the design of a sampling program.
Some natural enemies are affected by the time of year, and can be less effective as a result. The time of day can also be important, especially if the release is to be made outdoors or in a green house. When the temperature is high during the middle of the day, natural enemies tend to be more active and may disperse or leave the area they were released in. Higher temperatures during the release can cause increased mortality of the enemies, reducing the number available to attack your pest problem. Other weather conditions, especially rain, may also have an impact on natural enemy survival during release. As a general rule, releases should be made in a cool part of the day (early or late), under favorable weather conditions, and at a time of year that the specific natural enemy finds. If you have selected a reliable and knowledgeable suppler of natural enemies, then the quality of material you receive should be consistently high. However, there are some factors, such as shipping conditions that are out of the suppliers’ control. Therefore, it may be helpful to work with your supplier to develop a quality assurance protocol since the condition of natural enemies you receive can have a dramatic effect on the results you obtain.
Environmental conditions in area of release: Like all living organisms, natural enemies have specific requirements and limits for life. The conditions present in the area you plan to release natural enemies in should be taken into consideration prior to making releases. For example, some consideration prior to making releases. For example, some species of predatory mites will do better under hot, dry conditions while still others will perform better under cooler high humidity conditions.
Lighting can also have a dramatic impact on natural enemies. For example, the mealy bug destroyer beetle will slow or stop its reproduction, feeding and growth if supplemental lighting is not sufficient in winter months.
If releasing a mobile stage of a natural enemy (e.g. adults that can fly), it may sometimes be advisable to cage the natural enemies on infested plants for a day or two to allow them to become accustomed to their new surroundings. The presence of pest insects will also encourage reproduction, and reduce the likelihood that they will leave the area.
In some cases, the presence of nectar-bearing plants or other food sources (e.g. aphid honeydew) may also encourage natural enemy populations.
Pesticide use may be the most important consideration when including natural enemies in a pest management program. Spraying for pests other than those being targeted by natural enemy releases may interfere with or eliminate the natural enemies. Care should be taken to avoid spraying materials harmful to natural enemies directly before, during and after release. If spraying must be conducted, it is important to find out which pesticides have the least effect on natural enemies.
What should be done after the release?
It is extremely important with natural enemies to make sure that sufficient numbers have been established following release in your crop to control a pest problem. The sampling program you establish for monitoring for your pest population(s) can be modified to help you monitor natural enemy populations as well.
Bio-control in Greenhouses: Biological control is a tool to be considered in constructing as integrated pest management scheme for protected crop production. In a complete integrated pest management program, diseases, weeds, and plant growth must be considered as well as insects and mites. But because we are entomologists, this discussion covers insect and mite pests of greenhouse crops only. With IPM, each crop must be considered individually. Some greenhouse crops such as tomato and poinsettia are especially suitable for bio-control for several reasons. Tomatoes and poinsettias have relatively few insect and mite pests. They are not grown year round so there is a break in the production cycle. Biological control organisms can be used especially effectively for caterpillars, spider mites and whiteflies. The following tables are recommended management practices that simplify the task of setting up a bio-control program for a greenhouse crop and then there are some sources of natural enemies (Orr and Baker, 1997a).
Recommended Natural Enemies for Insect Pests:
| Pest | Natural Enemy | Rate | Unique Characters |
| Aphids | Aphid Lions Chrysoperla spp. | Preventative: 1-3/yd, Monthly, as needed Control (low infest): 2 to 5/yd, Bi-Weekly, 2 to 3 times Control (mod. Infest.): 4 to 8/yd, Bi-Weekly, 2 to 4 times Control (high infest): 7 to 12/d, Bi-Weekly, 3 to 5 times Maintenance: 1 to 2/yd, Tri-Weekly, Indefinitely COMMENTS: Rates shown above for larvae. For eggs, multiply rate times 5; for adults, divide by 4 | Purchase fed larvae that Are packaged individually. Lacewings are cannibalistic and should be well dispersed |
| Aphid Midge Aphidoletes aphidomyza | Preventative:1 to 3/yd, Monthly, as needed Control (low infestation): 2 to 5/yd, Biwkly- 2 to 3 times control (mod. Infest.): 4 to 7/yd, Weekly, 2 to 4 times Control (high infestation): 6 to 9/yd, weekly, 3 to 5 times Maintenance: 2 to 3/yd, Monthly. In definitely COMMENTS: Preventive releases should be made in sites open to the outside | Drop from plants into soil to pupate. If soil is pupate. If soil is not directly beneath foliage (i.e. if roots are bagged, etc.), they will die and not reproduce in the greenhouse. Can be kept active by using long-day lights. | |
| Aphid Parasitoids Aphidius matricarae | Preventative: 1 to 2/yd, bi-weekly, as needed Control (low infestation): 2 to 4/yd, weekly, 2 to 3 times Control (mod, infestation); 4 to 8/yd, weekly, 2to 4 times Control (high infestation); N/A Maintenance: 2 to 3/yd monthly | Shipped as live adults, ready to parasitize aphids | |
| Lady beetle Hippodamia convergens | “ Bug Pro” and other synthetic food sources are available to help keep lady in the garden | ||
| Syrphid maggots | May occur naturally where screening is not employed | ||
| Borad mite | Predaceous mite Neoseiulus barkeri | 10 to 30 per plant | |
| Caterpillars | Aphid lions Chrysoperla spp. | Purchase fed larvae that Are packaged individually. Lacewings are cannibalistic and should well dispersed. | |
| Bacterium Bacillus thruingiensis kurstaki (various formulations) | 1 to 5 teaspoons per gallon of water | Can be use with regular chemical pesticides | |
| Fungus | Yellow stocky cards and potato | ||
| gnats | slices useful for monitoring | ||
| Bacterium Bacillus thuringiensis israelinsis (Gnatrol TM) | 2 to 8 pints per 100 gallons of water | Compatible with most pesticides | |
| Nematodes Steinernema carpocapsae (Scanmask Tm) Steinernema carpocapsae (Ecomask TM) | 19,000 per sq ft. 70,000 per sq ft. | This strain is adapted to cooler soil temperatures This strain is adapted to warmer soil temperatures | |
| Soil-Dwelling Mite Hypoaspis miles | Preventative: 35 to 70/yd, Monthly, as needed Control 9low infest): 45 to 10/yd, Tri-weekly, 2 to 3 times control (mod. Infest): 100 to 140/yd, Bi-weekly, 2 to 4 times control (high infest): 100 to 200/yd. Bi-weekly, 3 to 5 times Maintenance: 4 to 75/yd, Monthly, Indefinitely COMMENTS: Interval depends upon site size | Will also feed on thrips pupae in the soil. | |
| Leafminers | Warm Weather Leaf Miner Parasitoid Dacnusa siberica | Preventative: 1 to 3/yd, Bi-weekly, as needed Control (low infestation); 2 to 5/yd Bi-Weekly, 2 to 3 times Control (moderate infestation): N/A Control (high infestation ):N/A Maintenance: 2 to 4/yd, Monthly, Indefinitely COMMENTS: Early season introduction will work the best. Use with parasitic nematodes | |
| Warm weather Leaf Miner parasitoid Diglyophus isaea | Preventative: 1 to 2/yd, Tri-weekly, as needed Control (low infest): 2 to 4/yd, bi-weekly, 2 to 3 times Control (mod. Infestation): N/A control (high infestation): N/A Maintenance: 2 to 3/yd, Monthly, Indefinitely Comments: late spring introductions will work the best. Use with parasitic nematodes | ||
| Mealy bugs | Australian lady beetle Cryptolaemus montrouzieri | Preventive: N/A Control (low infest): 2 to 4/yd, Tri- Weekly, 2 to 3 times Control (mod. Infest.): 4 to 6/yd, Tri-weekly, 2to 3 times Control (high infest): 6to 8/yd, Bi-weekly, 2 to 4 times Maintenance: 2 to 3/yd, Monthly, Indefinitely COMMENTS: Large scale use is normally in the southern states. | Lady beetles are somewhat sensitive to pesticides including soap. Lady beetles work best at high mealy bug population and not so well with low infestations. |
| Parasitic wasp Leptomastix dactylopii | 2 per sq yd or 5 per infested plant. Repeat 1 or 2 times per year. | Use in conjunction with the Australian lady beetle. Good control in 2 to 3 months. | |
| Mealy bug, Longtailed | Aphid Lions Chrysoperla carnea | Preventative: 1 to 3/yd. Monthly, as needed Control (low infest.): 2to 5/yd, Bi-weekly, 2 to 3 times Control (mod. Infest.); 4 to 8/yd, Bi-weekly, 2 to 4 times Control (high infest): 7to 12/yd, bi-weekly, 3 to 5 times Maintenance: 1 to 2/yd Tri-weekly, Indefinitely COMMENTS: Rates shown above for larvae. For eggs, multiply rate times 5; for adults, divide by 4 | Larvae are recommended |
| Scale insects | Lady beetles Harmonia axyridis: or Hippodamia) | Preventative: N/A Control (low infest): 1 to 2/yd, Tri-weekly, 2to 3 times control (mod. Infest.): 2 to 3/yd, tri-weekly, 2 to times Control (high infest.0: 3 to 4/yd, bi-weekly, 3 to 4 times Maintenance: 1-3/yd, Qtrly-Indefinitely Comments: The release rate shown above are suggested until further data is available | |
| Soft Scales | Parasitic wasp Metaphycus helvous | 5 to 10 per plant | For hemispherical scale, brown soft scale, nigra scale black scale |
| Spider mites | Predaceous mites Amblyseius (=Neoseiulus) fallacies | Preventative: 5 to 9/yd, Monthly, as needed Control (low infest.): 10 to 18/yd, Tri Weekly. 2 to 3 times Control (low infest.): 18 to 26/yd, bi-weekly, 2 to 4 times Control (high infest); 26 to 32/yd, bi-Weekly, 2 to 4 times Maintenance: 3 to 6/yd, Monthly, Indefinitely Comments: Fall preventative releases should be made into groundcover only one time | Will also feed on thrips pupae in the soil. |
| Predaceous mites Phytoseiulus persimilis Neoseiulus cucumeris | Release all predaceous mites at a rate of 1 per sq ft of crop plus 10 per mite-infested leaf. | ||
| Thrips | No really effective biological control organism is available. | ||
| Insidious flower bug Orius insidious | Preventative: N/A Control (low infest): 2 to 3/yd, Tri-weekly, 2 to 3 times Control (mod. Infest.): 3 to 4/yd, bi-weekly, 2 to 4 times Control (high infest.): 4 to 6/yd, Weekly, 2 to 4 times Maintenance: 1 to 2/yd, Monthly, Indefinitely COMMENTS: Use with Hypoaspis miles for mid-to long-term kill | Goes dormant with short days. Won’t stay on plants not bearing pollen use in conjunction with Neoseiulus cucumeris. | |
| Predatory Mite Amblyseius (= Neoseiulus) cucumeris | Preventative: 30 to 90/yd, Tri-weekly, as needed Control (low infest); 90 to 150/yd, weekly, 3 to 5 times Control (mod. Infest.): 150 to 210/yd, weekly, 4 to 6 times Maintenance: 60 to 120/ysd, Monthly, Indefinitely COMMENTS: the Preventative and Maintenance releases may be made with packets, repeated every 8 weeks. | ||
| Soil-Dwelling Mite Hypoaspis miles | Preventative: 70 to 90/yd, Monthly, as needed Control (low infestation); 90 to 130/yd, tri-weekly, 2 to 3 times Control (mod. Infestation): 130 to 190/yd, Bi-weekly, 3 to 5 times Maintenance: 8 to 100/yd, Monthly, Indefinitely | ||
| Predaceous mite Neoseiulus cucumeris | 10 to 200 per plant, then 10 to 50 per plant every 1 to 2 weeks | ||
| Predaceous wasp Thripoctenus americensis | Has been found to utilize the western flower thrips in Canada | ||
| Whiteflies: | Fungus Beauveria bassiana (Naturalis-LTM) | 2 tsp to 2 tbs, per gallon of water | Apply 3 to 5 sprays for complete control |
| The Greenhouse Whitefly parasitoid Encarsia formosa | Preventative: 4 to 6/yd, bi-Weekly, as needed Control (low infestation); 7 to 9/yd, Weekly, 3 to 4 times control (mod. Infest.): 10 to 14/yd, weekly, 3 to 5 times Control (high infestation ): N/A Maintenance: 5 to 7/yd, Monthly , Indefinitely Comments: for whitefly sensitive crops, try 125-150% of raters above plus Preventative: Weekly | Insecticidal soap can be used in conjunction with if applied in the “black scale” or “ brown scale” stage. | |
| The Mixed Species Whitefly Parasitoid (Eretmocerus californicus) | Preventative: 4 to 6/yd Bi-weekly, as needed Control (low infestation): 7 to 9/yd, Weekly, 3 to 4 times control 9mod. Infest.): 10 to 14/yd, weekly, 3 to 5 times Control (high infestation): N/A maintenance: 5 to 7/yd, Monthly,. Indefinitely Comments: For whitefly sensitive crops, try 125 to 150% of rates above plus Preventative: weekly | Use twice as many as Encarsia formosa because this parasite has males. | |
| Whitefly: Silver leaf | The Mixed Species whitefly parasitoid Eretmocerus californicus | Preventative: 6 to 8/yd, Bi-weekly, as needed control (low infestation): 9 to 13/yd, weekly, 3 to 4 times Control 9mod. Infest.); 14 to 18/yd, Weekly, 3 to 5 times Control (high infestation): N/A Maintenance: 7 to 9/yd, Tri-Weekly, Indefinitely COMMENTS: Should you wish to experiment with outdoor releases, try 50 to 75% of rates above | |
| Whitefly Destroyer Delphastus pusillus | Preventative: N/A Control (low infest.): 1 to 2/yd, Tri-Weekly, 2 to 3 times Control (mod. Infest.): 2 to 3/yd, bi-Weekly, 2 to 4 times Control (high infestation): 3 to 4/yd, Weekly, 3 to 5 times Maintenance: 1 to 2/yd, Monthly, Indefinitely COMMENTS: for releases in tomatoes, use 150-200% of rates determined above |
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Other management practices: Screening: Screening can significantly reduce numbers of insects flying into greenhouses. Several screening materials now on the market can exclude even thrips. A word of caution: the finer the screen, the greater its resistance to air flow into the greenhouse.
Quarantine: Growers should inquire of their supplier is having whitefly or mealy bug problems. At least then growers will know what to expect on the cuttings or plugs. In addition, all plant material should be inspected before it is brought into the greenhouse. Monitoring: Constant vigilance for insects, motes and diseases is required for effective pest management. Certain employees should be assigned the responsibility of scouting for insects and other pests on a regular basis (weekly the winter and twice weekly in summer). Written records should be kept of where various pests are found. Pests should be monitored by using yellow sticky cards, yellow pan traps, and by examining the foliage and occasionally the roots.
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