Secondlevel

Second level IPM is intermediate between basic and advanced. It is receiving increased research attention, but inherent complexities have greatly limited its effectiveness.

Emphasis is on management of key pests of all classes and their associated natural enemies comprising a community (e.g., a village of dwellings, an entire farm, a wooded area surrounding a village). Emphasis also is on substituting a variety of comparatively environmentally benign management tactics (e.g., cultural management, host resistance, biological control, behavioral control), to the greatest extent possible, for the therapeutic practice of pesticide application. Decision makers must determine how best to integrate these tactics to achieve long-term suppression of pests within a cost—benefit framework.

Cultural management is purposeful manipulation of the environment to reduce pest abundance. It is most effective when directed at the most vulnerable life stage of a pest. Four forms of habitat or environmental manipulation aimed at controlling pests have been practiced for centuries in agriculture: crop rotation, timing of planting or harvest to minimize pest damage, sanitation or elimination of noneconomic resources available for pest reproduction, and polyculture, or the interplanting of different crops to diffuse resource concentration. More recent practices include the planting or encouragement of selected types of noneconomic vegetation in the vicinity of crops or as cover crops to serve as harborage for natural enemies of pest insects. Analogues of these practices have been developed for managing insect pests in nonagricultural situations.

Host resistance is any inherited characteristic of a host that lessens effects of an attacking pest. For centuries, humans may have unknowingly or intentionally selected for cultivars of plants or breeds of animals that are best able to withstand pests. Modern breeding programs, however, often have placed more emphasis on increasing yields than on protection against pests. Entomologically, resistant traits are preadaptive characteristics of a host that reduce its detectability, acceptance, or nutritional value, or enhance its toxicity to a pest insect. Molecular genetics techniques that facilitate introduction of specific pest resistance genes into cultivars or breeds possessing desirable commercial or aesthetic traits are beginning to replace traditional resistance breeding approaches.

In biological control, parasitoids, predators, or pathogens are deployed as natural enemies in the reduction of pest populations. Of the myriad insect species that could become pests, most do not because they are suppressed effectively by naturally occurring populations of biological control agents. Natural levels of biocontrol, however, often are insufficient for IPM purposes. Biological control then takes the form of importing absent natural enemies from other locales (termed importation or classical biocontrol), augmenting existing natural enemies by rearing and then releasing substantial numbers into the target community (termed augmentation), or tailoring management tactics to reduce negative effects on existing natural enemy populations (termed conservation). The latter is the most widely practiced form of biocontrol.

Behavioral control is manipulation of the behavior of pest individuals to prevent them from causing harm or unpleas antness. Because of the expense and technological challenges associated with its use, behavioral control usually is directed only at key pests. Behavioral control may involve use of natural or synthetic chemical or physical stimuli to lure pests to sites where they are killed, or use of such stimuli to disrupt the ability of pests to find or use a potential resource. An ideal form of behavioral control might involve joint use of disruptive and attractive stimuli to achieve maximum effect, but this form is not yet widespread in practice.

Vineyards in parts of Europe and North America represent one of the few areas in which pest management is practiced effectively under the second-level IPM concept. Besides using essential elements of first-level IPM for insect pests, certain practitioners of vineyard IPM in these locations blend host plant resistance with cultural, biological, and behavioral controls for suppression of key pest insects and also use a suite of cultural controls for managing key disease and weed pests. This approach has resulted in marked reduction in pesticide use and greater stability of relationships among organisms comprising vineyard communities.

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