In Antarctic summer 1983/1984 samples of planktonie and attached diatoms were collected in the Admiralty Bay (King George Island, South Shetland Islands) as well as samples of planktonie diatoms in the region of South Orkneys, Drake Passage and Bransfield Strait (BIOMASS-SIBEX Project). Using gas chromatography residues of chloroorganic pesticides, namely the compounds of the DDT group and HCH isomers were determined. It was found that the highest values of the content of these compounds occurred in attached diatoms coming from areas continuously washed with water from the melting glacier, in planktonie diatoms from the samples of the Admiralty Bay and from strongly glaciated regions. A hypothesis was put forward that along with the direct atmospheric transport the release of the deposits of these compounds from ice and glaciers during their melting is an additional source of input of chloroorganic biocides into Antarctic waters. Diatoms are good indicators of this process.
The insecticidal efficacy of Gmelina arborea L. product extracts was assayed for suitability in controlling the legume pod borer Maruca vitrata Fab. (Lepidoptera: Pyralidae) and the pod sucking bug Clavigralla tomentosicollis Stäl (Hemiptera: Coreidae) on cowpea. Field studies conducted in 1999 and 2000 cropping seasons at the research farm of the Institute for Agricultural Research, Samaru showed that extract of Gmelina arborea fruit at 10% (w/v) caused impressive reduction ofboth pests and protected the pods from serious damage. Grain yield was higher in the fruit extract treated plants compared to the leaf, bark treatments and the untreated control. However, all the Gmelina products’ extracts were superior (p < 0.05) to the untreated control but was not better than the synthetic insecticide (Sherpa Plus) used in all the assessments made. This study is the first reported case ofthe potential of Gmelina arborea products’ extracts for control of Maruca pod borer larvae and pod sucking bug on field cowpea. This plant could add to the pool of herbal landraces already found to be insecticidal to insect pests of tropical crops if explored and exploited for use by limited resource farmers in tropical countries.
Chemical plant protection is still an indispensable method in effective potato protection against Colorado potato beetle – CPB – (Leptinotarsa decemlineata Say) in Poland. This species is able to develop strong resistance against all active substances used in chemical and biological insecticides. The phenomenon of resistance is variable in time and in space. Therefore the objective of the study was to determine the present susceptibility level of Polish populations of CPB to main groups of insecticides recommended in Poland for CPB control.
In this short communication describing experiments carried out on the larvae of two insects, Unaspis euonymi Comstock (feeding on Euonymus japonicus Thunb.) and Dynaspidiotus britannicus Newstead (feeding on Laurus nobilis L.), we evaluate for the first time the efficiency of using DNA insecticides in the control of sap-sucking insects, including armored scale insects. Over a period of 10 days, high insect mortality was detected in both U. euonymi and D. britannicus, accompanied by a significant decrease in the concentration of target RNAs. At the same time, no visible changes were observed when the leaves of the host plants were subjected to treatment with DNA insecticides for one month. The results show the high efficiency of DNA insecticides used against hemipteran insect pests. It is noteworthy that the high efficiency of DNA insecticides and their low cost in comparison with RNA preparations provides a safe and extremely promising potential vehicle for the control of sap-sucking insects.
5.8S ribosomal RNA plays an important role in protein synthesis and eukaryotic ribosome translocation. Contact DNA insecticides based on antisense fragments of 5.8S ribosomal RNA gene of gypsy moth Lymantria dispar L. showed prospective insecticidal activity on its larvae. The most pronounced insecticidal effect was found for antisense fragments 10 and 11 nucleotides long (oligoRIBO-10 and oligoRIBO-11), whereas 12 nucleotides long fragment (oligoRIBO-12) caused the lowest level of insect mortality. This data corresponds to results obtained earlier using rabbit reticulocyte and wheat germ extracts, where maximum inhibition of protein synthesis was observed when a relevant oligomer 10-11 nucleotides long was used, whilst longer chain lengths resulted in reduced inhibition. Using oligoRIBO-11 fragment we have shown penetration of antisense oligonucleotides to insect cells through insects’ exoskeletons. MALDI technique registered the penetration of the oligoRIBO-11 fragment into insect cells after 30 min and a significant response of insect cells to the applied oligonucleotide after 60 min, which indicates not only that the oligonucleotide enters the insect cells, but also the synthesis of new substances in response to the applied DNA fragment. Contact DNA insecticides developed from the L. dispar 5.8S ribosomal RNA gene provide a novel biotechnology for plant protection using unmodified antisense oligonucleotides.
Obviously, the moment has come in agriculture and forestry when we must decide to gradually abandon (where possible) non-selectively acting chemical insecticides, taking into consideration the overall decrease in the total biomass of insects, especially pollinators, and the increased number of diseases and human deaths directly or indirectly associated with chemical insecticides. Yet with the world facing the rapid growth of human populations, the annual reduction of cultivated areas, and substantial losses from insect pests, most experts believe that no serious alternative to chemical insecticides exists. However, there is definitely room to create more well-tailored chemical insecticides. And there is hope, in the form of effective DNA insecticides able to provide an adequate level of safety for non-target organisms. In this short communication describing experiments carried out on the larvae of Ceroplastes japonicus Green (feeding on Ilex aquifolium Linnaeus), we show for the first time the enormous potential for the use of DNA insecticides in the control of soft scale insects and how they could replace non-selective organophosphate insecticides.