Note. This is the
first of 3 parts of an article that contains important
information on advances in the uses of green lacewings in
biological control. This is my condensed version of a more
detailed review paper, entitled "Commercialization of
predators: recent lessons from green lacewings (Neuroptera:
Chrysopidae: Chrysoperla)". printed in American
Entomologist, 2000, vol. 46 (1): 26-38. For additional
information, the reader is urged to go to the original paper,
which cites over 120 references to other review papers and the
original scientific literature. For general information on
lacewing biology and their use in biological control, see green lacewings. Many other articles containing information about
green lacewings are in our archives; see our green lacewing index. Our sincere thanks go to the authors for allowing
us to condense their original paper to produce this version;
special thanks to the Taubers for reviewing and correcting the
condensed manuscript. Dan Mahr, BCN Project Director
The commercialization of natural enemies and increasing their use in pest management present applied entomologists and ecologists with formidable challenges. A response to these challenges requires: reducing the cost of mass-rearing and manipulating natural enemies, improving the success rate and predictability of biological control procedures, and demonstrating the effectiveness, ecological benefits, and safety of biological control under commercial conditions.
Chrysoperla spp. long have been considered important naturally occurring predators in many horticultural and agricultural cropping systems, including vegetables, fruits, nuts, fiber and forage crops, ornamentals, greenhouse crops, and forests. Worldwide they also rank as some of the most commonly used and commercially available natural enemies. For many years, two Chrysoperla species (C. carnea and C. rufilabris) have been mass-reared and marketed commercially in North America and Europe. Two additional species, C. externa and C. nipponensis, are used in Latin America and Asia. In response to a questionnaire in 1992, members of American Association of Applied Ecologists ranked Chrysoperla spp. as unrivaled on the list of commonly applied, commercially available predators.
Chrysoperla spp. are used in integrated pest management (IPM) systems in two principal ways: (a) periodic release of mass-reared individuals and (b) manipulating the habitat, e.g., to attract or conserve naturally occurring field populations. Recent work has focused on improving both approaches. As discussed below, significant new developments in artificial larval diets, mechanized production methods, long-term storage, and quality control can reduce the cost and increase the availability and reliability of mass-reared Chrysoperla spp. Similarly, a re-examination of existing information on the chemical ecology and movement of lacewings reveals ways for improving the ability to attract and retain their populations in agricultural situations. Furthermore, the efficacy of procedures for both releasing and attracting Chrysoperla is being evaluated rigorously with quantitative methods under field conditions.
There has been recent progress in the following
crucial areas of research with this important group of predators:
(a) systematics, (b) mass-production, (c) field applications, and
Systematics is the study of classifying organisms according to their biological characteristics. Virtually every aspect of integrated pest management (IPM) depends on having a sound systematics base. Systematics provides stable names that enable communication and access to the scientific literature; also, it provides comparative information that is essential for understanding the biological traits of both pests and their natural enemies. Consequently, systematics forms the framework for virtually all biological control procedures. Although systematics is seemingly most important to the biological control researcher, it has underlying importance to the pest management practitioner. Correct identification of both the pest and its natural enemies is often crucial to successful biological control.
In the case of green lacewings in the genus Chrysoperla,
much sound systematic research has been accomplished, but the
final chapter has yet to be written, especially relating to Chrysoperla
carnea. This species (or complex) is highly important in both
natural control as well as augmentation biological control.
However, there is substantial variability in the biological
traits of this species. In the eastern and midwestern United
States there are two distinct and reproductively isolated
entities: C. carnea, which is the most common in
agriculture, and C. downesi, which is associated with
evergreen trees. However, in the western United States, there is
greater variability between populations and at this time we
prefer to consider the various entities as biotypes of unknown
species status. The systematics of this group must be resolved in
order to achieve maximum success in biological control programs.
The commercialization of biological control depends upon the ability of insectaries to produce and market efficiently a highly reliable and relatively inexpensive supply of natural enemies. Achieving these objectives first requires efficient, standardized mass-rearing procedures: (a) the use of inexpensive, nutritious diets; (b) mechanized and space-efficient production systems; (c) reliable storage methods; and (d) periodic evaluation of natural enemy quality. In each of these areas research has made practical and economically beneficial advances in mass-rearing of Chrysoperla. However, the effective marketing of natural enemies and the education of targeted customers continue to be serious issues in need of attention.
Currently, rearing of larvae constitutes the most costly aspect in Chrysoperla mass-production largely because all three instars are predaceous. Most insectaries depend on mass-produced insect prey as food, which is relatively expensive compared with artificial diets.
The development of an artificial diet should continue to receive a high priority. Lacewing larvae will feed and develop on either liquid or solid diets. Although some automation is available for producing and encapsulating liquid diets, the cost has remained relatively high. Recent research has resulted in a fully artificial, solid or semisolid diet that apparently offers significant advantages over other diets. The new diet is relatively inexpensive, does not require encapsulation, and does not spoil quickly. When this diet becomes generally available, it is projected to reduce the cost of rearing from $0.3587 to $0.00025 per adult lacewing.
Adult dietary requirements often present major practical problems for mass-rearing and marketing predators. Early research on C. carnea nutrition yielded relatively inexpensive and effective artificial diets that sustain high rates of egg production. With these diets, females of all species of Chrysoperla tested thus far can produce 500 to 1,000 eggs in ~30 days. This successful diet provides a fine example of the practical benefits derived from fundamental research in insect nutrition.
Mass-rearing of insects (especially cannibalistic predators) requires considerable space and manual labor; currently, space-efficient, automated mass-rearing systems for Chrysoperla are under development. These systems include compact holding units for adults, mechanical devices for feeding adults and harvesting eggs, mechanized methods for presenting the larval diet, and automated systems for packaging larval-rearing units. When fully developed, such mechanized systems would enhance production greatly and reduce costs drastically. Progress thus far illustrates the advantages (biological and economic) that can accrue when engineers and biologists combine their expertise in solving practical problems.
Medium and long-term storage of entomophagous species is a key, often-missing element in the cost-effective production and distribution of natural enemies. Recent studies indicate that long-term storage of adult Chrysoperla species can be accomplished simply, economically, and without loss of quality. Equally important, post-storage adults can be brought into a reproductive state quickly, predictably, and synchronously.
Short-term storage of eggs, which is essential for efficient, cost-effective distribution, is more problematic for Chrysoperla. Several studies demonstrated that C. carnea eggs remain viable for up to 3 weeks when they are held at 46°F (8°C). Unfortunately, the studies offer contradictory results regarding the best age to store the eggs. We conclude that it is reasonable to store young eggs because this practice would reduce hatching and cannibalism during distribution. Additional, carefully controlled studies are necessary.
The standardized production of high quality natural enemies is crucial for both the practice of biological control and users perception of biological control as a dependable pest management tactic. However, the quality of commercially marketed natural enemies can be variable because there are no strict quality control standards in the United States. For example, in a recent evaluation of shipments from insectaries, growers orders for C. carnea were not filled consistently with the correct species, and cannibalism significantly reduced the survivorship of lacewings in transit. Such problems can be overcome through greater care in maintaining correctly identified, pure colonies and improved procedures during mass-production and packaging.
In viewing the overall issue of quality
control, we believe that it is essential for the insectary
industry to develop standards that promote the reliability and
standardization of commercially produced natural enemies. In this
regard, there appears to be greater coordinated efforts and more
cooperation between the insectary industry and scientists in
Europe than in the United States.
In the next issue, Part
II: Field Application
Maurice J. Tauber, Catherine A. Tauber, (both Department of Entomology, Cornell University, Ithaca, NY), Kent M. Daane, and Kenneth S. Hagen (both Center for Biological Control, University of California, Berkeley
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