Resistance natural enemies

Whenever applied, IPM practices have consistendy resulted in decreases in insecticide applications of 50 to 90% over conventional spray programs. By encouraging natural enemies, IPM practices markedly decrease the rigor of natural selection by pesticides that is responsible for resistance. Natural enemy preservation also prevents the great fluctuations and suiges in insect pest populations observed after the injudicious use of broad-spectrum insecticides. Under the IPM concept, insecticides are generally used when other practices are inadequate and the pest population reaches the economic threshold. In order to make the IPM concept effective, insecticides must be used as selectively as possible, with minimal disturbance to all other elements of the ecosystem. Thus IPM practices are essentially blueprints for the proper use of insecticides in insect pest control. 

Despite the use of 2.5 million tons of pesticide worldwide, approximately 35% of potential crop production is lost to pests. An additional 20% is lost to pests that attack the food post-harvest. Thus, nearly one-half of all potential world food supply is lost to pests despite human efforts to prevent this loss. Pesticides, in addition to saving about 10% of world food supply, cause serious environmental and public health problems. These problems include human pesticide poisonings fish and bird kills destruction of beneficial natural enemies pesticide resistance contamination of food and water with pesticide residues and inadvertent destruction of some crops. 

Consequences of epibiotism to the host alga depend on the community composition and, vice versa, epibiotism may modify the susceptibility of the host to herbivory. The community context hence largely determines the influences of both herbivory and epibiotism on the host algae, and should be taken into account more explicitly in studies of chemical resistance to natural enemies. 

Insect resistance and environmental pollution due to the repeated application of persistent synthetic chemical insecticides have led to an Increased interest in the discovery of new chemicals with which to control Insect pests. Synthetic insecticides, including chlorinated hydrocarbons, organophosphorus esters, carbamates, and synthetic pyrethroids, will continue to contribute greatly to the increases in the world food production realized over the past few decades. The dollar benefit of these chemicals has been estimated at about 4 per 1 cost (JJ. Nevertheless, the repeated and continuous annual use in the United States of almost 400 million pounds of these chemicals, predominantly in the mass agricultural insecticide market (2), has become problematic. Many key species of insect pests have become resistant to these chemicals, while a number of secondary species now thrive due to the decimation of their natural enemies by these nonspecific neurotoxic insecticides. Additionally, these compounds sometimes persist in the environment as toxic residues, well beyond the time of their Intended use. New chemicals are therefore needed which are not only effective pest... 

The ethylene-insensitive plants also showed reduced defense protein synthesis and were susceptible to soil pathogens to which they were normally fully resistant. In connection with the third trophic level, Kahl et al. (2000) found that attack by Manduca caterpillars on wild tobacco plants causes an ethylene burst that suppressed induced nicotine production but stimulated volatile emissions. They argued that the plant chooses to employ an indirect defense (the attraction of natural enemies) rather than a direct defense to which the attacker could adapt (Kahl et al, 2000 Winz and Baldwin, 2001). This implies that the plant is capable of identifying its attacker. We discuss this possibility in more detail in the discussion of specificity. 

Schiiler, T. H., Poppy, G. M., Kerry, B. R. and Denholm, I. (1999a). Potential side effects of insect-resistant transgenic plants on arthropod natural enemies. Trends in Biotechnology 17 210-216. 

Croft, B.A. and Strickler, K., Natural enemy resistance to pesticides Documentation, characterization, theory and application, in Pest resistance to pesticides, Georghiou, G.P. and Saito, T., Eds., New York Plenum Press, 1983, p. 669. 

Hoy, M.A., Pesticide resistance in arthropod natural enemies Variability and selection responses, in Pesticide resistance in arthropods., Roush, R.T. and Tabashnik, B. E., Eds., New York Chapman and Hall, 1990, p. 203. 

The aforementioned parasites and predators are all somewhat tolerant of the pyrethroids, an attribute that gives some hope for at least a modicum of natural-enemy conservation when these compounds are used in mid-season. It seems reasonable that careful evaluations of comparative toxicity data for Heliothis and some key major natural enemies could lead to identification of nonpyrethroid insecticides that if needed could be used with at least some degree of selectivity against the first two generations of the pest. However, such data are scarce, and more work is needed to provide an adequate data base that would allow more flexibility in choosing an appropriate chemical. Given the history of resistance in the tobacco budworm to various classes of insecticides, it would be advisable to alternate classes of insecticides early in the season to avoid selecting populations of the pest for multiple resistance. 

Pest/Natural Enemy Complex/ apple USA Monitoring, Lack of Croft 1982, Resistance in Key Pests, Croft et al. 1984, Resistant N.E., Selective Croft et al. 1987 Pesticides, Biological Control/Grower Compliance, Improved Monitoring Methods ... 

To summarize the resistance situation in broad terms, no key pest such as the codling moth, apple maggot, plum curculio has developed resistance to the OP azinphosmethyl, whereas a variety of secondary pests such as mites, aphid, leafhoppers, leafminers and their natural enemies have developed resistant strains thus azinphosmethyl has become more selective. The example cited later of management of cyhexatin resistance management in the spider mite... 

The success of the resistance management program for the complex of pests and natural enemies of apple in the United States, while generally good, has been mixed. In some areas of the eastern United States where OP resistance has developed in key leafroller species, increased use of nonselective pesticides such as the pyrethroids has occurred. However, in the western United States,... 

They point out that biodiversity is necessary for the sustainability of agricultural, forest, and natural ecosystems on which humans depend. Roughly 99% of pests are controlled by natural enemies and by plant resistance. Loss of key pollinators may mean loss of a crop. Honeybees can pollinate some crops, but not all of them. There are already species for which no pollinators are left.12 Current extinction rates are 1000-10,000 times the natural rate. The concern is that keystone species (i.e., species without which the ecosystem cannot function) may be lost. These are more likely to be soil microbes or insects than pandas or tigers, despite the popular appeal of the latter. 

Genetic manipulation of arthropod natural enemies Is an old concept (9-10), although field Implementation of genetically-improved natural enemies was not achieved until recently (8,11). Various biological and behavioral attributes have been discussed as amenable to genetic selection. Including sex ratio, temperature tolerance, developmental rate, fecundity, diapause, and host preference, as well as pesticide resistances (12). 

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