Ecological Knowledge and Environmental Problem-Solving Concepts and Case Studies (1986) / Chapter Skim
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14. Biological Study of California Red Scale
14. Biological Study of California Red Scale
Pages 165-189
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From page 165... ...
Most biological control efforts fail, either because the control agent does not survive or because, if it survives, it does not result in satisfactory control. The California red scale study illustrates features common to many instances of biological control, but it also shows how imaginative use of some new elements of ecological theory, such as those related to foraging and sex allocation, led to changes in project organization that illuminated the processes underlying effective biological control.
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From page 166... ...
When A Iingnanensis was introduced, biological control was achieved in 166
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From page 167... ...
melinus in 19561957 was biological control achieved in inland valleys (Rosen and DeBach, 1979~. In contrast with the situation in southern California, economical biological control of California red scale does not exist in the San Joaquin Valley or the desert, even though both Comperiella bifasciata (Encyrtidae: Hymenoptera)
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From page 168... ...
The specific objective motivates a continuing biological control project, whose key components are the obtaining and manipulation of natural enemies of the scale, the importation of exotic predator and parasitoid species reared from California red scale or related species around the world, and the mass rearing and release of endemic and exotic natural enemies. We seek by these means to develop practical and economical ways of augmenting endemic natural enemy populations by releasing insectary-reared individuals.
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From page 169... ...
The ecosystem components named earlier were identified because they were economically important or because previous research with citrus, with other agricultural ecosystems, or with natural ecosystems suggested that these components were biologically important. Significance of impact If biological control of California red scale is achieved, chemical control will be required only infrequently when weather patterns, dust, insecticides (drifting from adjacent crops from treatments of an associated pest)
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From page 170... ...
Iingnanensis failed to achieve economic scale control in the more interior citrus districts, so additional natural enemies were sought. One of these, A
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From page 171... ...
However, because we wanted to know the effects of natural enemies on the red scale population of a tree, it seemed reasonable, at least initially, to consider the natural enemies on a within-tree basis also. For our studies of economic effects, we again used the tree as a universe, but we were also concerned with the economic effects of biological control.
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From page 172... ...
. The age structure of California red scale varies seasonally with location in California.
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From page 173... ...
. ISt PUMPIN( , MOVE BENT 173 REMAINS | LEAVES ON SCALE BRIEF REST SCALE COVER COVE R 2nd PUMPIN G MOVENIE'JT AND EGG DEPOSITION WIT HDRAWALFIGURE 2 Behavioral sequence exhibited by Aphytis melinus and A
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From page 174... ...
.7 8 9 10 ~ HOST SIZES AVAILABLE n- 301 1 1 12 13 ~ ~ or\ 11~81~ ~ .9 1.0 1.1 1 2 1.3 .4 5 .6 7 .8 SCALE SIZE (mm 2) FIGURE 3 a-d, size distribution of third-stage California red scale on which Aphytis melinus laid indicated numbers and sexes of eggs.
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From page 175... ...
. ~ 1 1.2 175 1 ~ FIGURE 4 a-d, size distribution of third-stage California red scale on which Aphytis lingnanensis laid indicated numbers and sexes of eggs.
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From page 176... ...
Iingnanensis by A melinus also suggested a testable explanation for the absence of economic biological control in the San Joaquin Valley.
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From page 177... ...
Similarly, Comperiella bifasciata, a parasitoid introduced into southern California in 1939, is rare in the interior coastal valleys and coastal citrus zones, but is common in the San Joaquin Valley. Second, what causes size variations in California red scale?
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From page 178... ...
SOURCES OF KNOWLEDGE Generally Accepted Ecological Facts Much is known about the natural history of California red scale, its predators, and its parasitoids, especially the parasitoid genus Aphytis (Bodenheimer, 1951; Ebeling, 1959; Rosen and DeBach, 1978, 19791. Less is known about processes that govern the scale's biological control.
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From page 179... ...
However, DeBach and colleagues (DeBach, 1966; DeBach and Sundby, 1963; Rosen and DeBach, 1979) concluded, on the basis of laboratory and field experiments, that the two principal parasitoids responsible for biological control of California red scale were not limited by host density.
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From page 180... ...
and Whitham (1978, 1979, 19801. Project as Experiment The California red scale research project was designed to improve the biological control of California red scale and to test conventional wisdom as to the attributes that characterize an effective biological control agent, in this case a parasitoid.
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From page 181... ...
Thus, we have used a flexible research strategy of hypothesis formation and testing that incorporates laboratory and field experiments mixed with computer simulation models of aspects of California red scale and parasitoid biology. Expert Judgment Clearly, a research project of this sort is not undertaken by a single researcher.
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From page 182... ...
Theory played a role both in formulating the hypotheses and in specifying the type of project to look at. The California red scale biological control project was chosen for several reasons: the natural histories of the organisms involved were well known, the history of the project was well documented, the scale is controlled biologically in only a part of its California range, the scale and its natural enemies are easily reared in the laboratory, and the parasitoids responsible for the biological control of the scale are known.
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From page 183... ...
1974. Biological Control by Natural Enemies.
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From page 184... ...
1980. Foraging strategies, population models and biological control: A case study.
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From page 185... ...
1982. Parasitoids as biological control agents A fundamental approach.
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From page 186... ...
Luck's description is of the effort to extend control to the desert and the San Joaquin Valley, and his thrust is an interesting mixture of classical biological control (much like the introduction of the Aphytis species that are already present) and academic evolutionary ecology.
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From page 187... ...
For the most part, these proved inspirational or didactic, rather than directly applicable. The key to the entire biological control rationale is that the host (red scale)
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From page 188... ...
He calls for a more narrowly focused release effort, rather than the hit-andmiss release of many potentially beneficial species that typifies some biological control efforts. The direction that the red scale study has taken certainly qualifies as a desirable narrowing of focus.
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From page 189... ...
1974. Biological Control by Natural Enemies.
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