Biological pest control predators

Breeding field crops for disease resistance has had similar successes. While the examples in which parasites and predators have been used to achieve pest control are numerous, it is evident that not enough support has been given here in the past and it is virtually certain that this will receive far more exploration in the future. Other biological... 

Of the other clavicipitalean genera, no records can be found concerning the use of the teleomorph per se as an infective unit for the biological control of arthropod pests. However, the literature on the exploitation of their anamorphs is vast and predates that on chemical pest control. Thus, it is not feasible to encompass all of this information in a single chapter. Instead, selected examples are presented for each anamorph genus to reflect both the past history and the current situation. 

Biological and Natural Controls. Parasites and predators are effective in limiting the numbers of pest Insects and plant pathogens both in nature and for crops (35). This basic fact led to the development of biological controls. For example, the vedalia beetle, which was Introduced for control of cottony cushion scale on citrus in California, has provided continuous effective control of this pest for many decades. Worldwide only approximately 1% of the pests have been effectively controlled by Introduced biological control agents (43). 

However, not all natural enemies are fully effective. For example, the gypsy moth has approximately 100 parasites and predators attacking it but the pest reaches outbreak levels periodically (35). Nearly 40 biological control agents were introduced from Europe and Asia to control the moth and 11 of these became established (44). Yet not one of the 11 blocontrol agents is providing fully effective control, although each contributes to some limitation of this pest. 

The presence of aphids, Toxoptera graminum (Rondani) and Macrosiphum granarium (Kirby), on wheat during March and April has caused considerable alarm to wheat farmers in central Mexico. It has been found, however, that in the majority of cases the aphids do not represent a serious economic problem. Naturally occurring predators are able to reduce the aphid populations rapidly. For cases in which this natural biological control is not effective it has been found that benzene hexachloride (BHC) applied as a dust gives good control of these pests. 

Biological control involves the introduction of predators and parasitoids to attack pests. The extent of control using this technique varies and can be quite good in some cases, but unforeseen ecological impacts occur when imported species attack nontarget organisms. 

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