The ecological basis of boll weevil (Anthonomus grandis Boheman) management

The boll weevil (Anthonomus grandis Boheman), generally considered to be native to Mexico or Central America, spread into the southern United States of America in the late 1800s and seriously threatened the cotton industry. As there were no effective alternatives, pest control specialists studied the insect's ecology and advocated cultural practices that would disrupt its environment and maximize the benefits of natural biological and environmental controls. An ecologically orientated pest management scheme founded on cultural practices emerged well before suitable chemical control technology became available and allowed farmers to live with the weevil problem.Despite the ingenuity of the early management scheme, it frequently did not provide satisfactory boll weevil control gauged by present standards. Control of the pest thus shifted largely from an ecological to a chemical approach as effective synthetic organic insecticides became available after World War II. The chemical approach was successful for a number of years, but problems of insecticide-resistant strains of pests, secondary pest outbreaks, environmental quality, and increased costs of the insecticides have forced pest control specialists to re-emphasize the nonchemical techniques used widely against the boll weevil before World War II and to revive the ecological approach to weevil management.This article examines boll weevil ecology as related to management of the insect and reviews the status and prospects of ecologically-based weevil management techniques in the United States.     

Insektenpheromone

Pheromones — semiochemicals used by insects for intraspecific chemical communication — can be isolated and with special analytical techniques their chemical structure elucidated. With stereoselective synthesis methods, presented by the preparation of sex attractants and aggregating pheromones of moths and beetles, respectively, a synthetic access to compounds is given which can be used for behavior manipulation of insects. Aside the importance of these compounds for investigations of the sensoric process the possibility of their application in an integrated and biological pest control is discussed.     

Die Anwendung von molekulargenetischen Techniken in der Neurochemie

Research in molecular neurobiology has recently entered a new phase of rapid development as a result of the application of the techniques of molecular genetics. This is illustrated by recent work on the electric ray (Torpedo marmorata and T. californica), whose electric organ is a rich source of cholinergic synapses. Other examples from recent literature of the application of the recombinant DNA technique to the mammalian central nervous system are given and possible future developments are discussed.     

A new pheromone of the silkworm moth Bombyx mori

The female silkmoth Bombyx mori L. emits a second pheromone component bombykal (E-10, Z-12-hexade-cadien-1-al) in addition to the well-known sexual attractant bombykol (E-10, Z-12-hexadecadien-1-ol). Bombykal stimulates its own specialized and highly sensitive olfactory cells of the male moth. Surprisingly, the aldehyde inhibits the release of the male's wing-fluttering response to bombykol.     

Salinity discrimination in harbour seals: a sensory basis for spatial orientation in the marine environment?

 Salinity variations can be considered as a potential source of information for orientation in the marine environment. To use this kind of environmental information marine animals must be able to detect these salinity differences. Therefore we determined salinity-difference thresholds of two harbour seals for the discrimination of seawater solutions as a function of the salinity level (15–35‰) and compared them with the thresholds of human subjects. Whereas in humans thresholds increased with increasing salinity level, thresholds of seals decreased with increasing salinity level. Both seals achieved best sensitivity at 30‰ salinity, where they detected a salinity difference ≤4%. These data indicate that the ability of seals to detect salinity differences of seawater is well tuned to the natural occurrence of this environmental information. Their high gustatory resolving power for differences in seawater salinity is suggested to meet the basic requirements for chemosensory orientation of seals in the marine habitat. Received: 10 February 2000 / Accepted in revised form: 19 September 2000