Dokumentum


Címe:Novel-type insecticides: specificity and effects on non-target organisms
Szerző(k):Béla Darvas and László A. Polgár

 


In. Isaac Ishaaya and Danny Degheele (Editors) Insecticides with Novel Modes of Action: Mechanisms and Application. (1998) ISBN 3-540-63058-9 Springer-Verlag, Berlin Heidelberg New York

Béla Darvas and László A. Polgár

 

Novel-Type Insecticides: Specificity and Effects on Non-target Organisms



The novel-type insecticides are required to have low acute mammalian toxicity, because of their human applicators and consumers of agricultural products. On the basis of their high acute toxicity on mammalians, abamectin (although ivermectin is used as a drug) and imidacloprid do not really fit this picture. The values of bird toxicity are usually similar to the mammalian’s values. This is very important if we consider the high expenses of bird losses following pesticide treatments. Abamectin, AC-303630, imidacloprid and triflumuron unfortunately are harmful to birds. Toxicity of a compound to poikilotherm vertebrates (i.e. fish, amphibians, reptiles) is also considerable, especially because its values usually are quite different from the values of homoiotherm vertebrates (i.e., birds, mammals). Abamectin, diafenthiuron, buprofezin, fenoxycarb, flucycloxuron, methoprene and tebufenozide are harmful to fish. It is not very easy to qualify the neemderived insecticides. Botanical insecticides based on natural origin are highly welcomed by environmentally concerned organizations in plant protection. We should note that several very toxic and dangerous compounds [e.g. ricin from Ricinus communis (Euphorbiaceae), colhicin from Colhicum autumnale (Liliaceae)] are also known to have a natural origin. Nevertheless, the mode of action of numerous allelochemicals of Azadirachta indica is not intensively and strictly researched (azadirachtin A is one of the exceptions) and they may have chronic effects on vertebrates. An additional problem is the changeable chemical profile of a single neem-derived product. Using a single score system, as in Table 4, we can conclude that Bacillus thuringiensis delta-endotoxin, chlorfluazuron, hexaflumuron, lufenuron, pymetrozine and teflubenzuron are acutely safe to vertebrates. Surprisingly, some of the important data on bird and fish toxicity are not included in The Pesticide Manual by the manufacturer, and lack of model bird and fish species makes it difficult to compare these values. Nevertheless, it is very difficult to find a world-wide accepted representative test animal.
An “ideal insecticide” would be broadly active on insect pests but paradoxically inactive on non-target insect species. Specificity of an insecticide includes many different aspects and has insecticide and insect impacts. We need to emphasize, however independently of the beneficial saving properties of a compound, that insecticides that reduce the number of the host(s) through the food chain always decrease the numbers of their predator(s) and parasitoid(s). Especially obligate endoparasitoids suffer from this dependency (e.g. B. thuringiensis). The rate of natural enemies and hosts before and after an insecticide treatment would probably be a suitable criterion for the selectivity of a compound.