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[Bt toxin distribution in transgenic Bt cotton and soil system].

This study showed that the amounts of Bt toxin expressed in transgenic Bt cotton leaves and stems (103.5 - 134.1 ng x g(-1)) were rather higher than those expressed in transgenic Bt cotton roots (44.7 - 21.2 ng x g(-1)), indicating that total amount of soil Bt toxin introduced by transgenic Bt cotton could be decreased through treating its above-ground biomass. In comparing with the amount of Bt toxin expressed in transgenic Bt cotton plant, that expressed in its root exudates was rather lower, showing that the effects of plant Bt toxin on soil ecosystem would be limited if other sources of Bt toxin introduced into soil were controlled.

Bacterial Proteins↗

[Cleaning and molluscicide treatment for schistosomiasis control].

We evaluated the effect of niclosamide treatment and the additional cleaning of basins and pools on the density and infection rate of Bulinus truncatus within the irrigation network of Oudaya. The period prior to molluscicide treatment (January-May) revealed a mean density of 151 snails/m2 in 1995-96 and 127 snails/m2 in 1997-98. After cleaning had started, the mean density prior to molluscicide treatment fell to 84 snails/m2 in 1999-2000. After molluscicide treatment, densities dropped to very low levels only rising again from October. In November 1999-96 mean density reached 150 snails/m2 but after cleaning started in 1997-98 this only reached 80 snails/m2; in 1999-2000, when cleaning was undertaken 3 months before and after molluscicide treatment, it reached only 18 snails/m2. From 1995 to 1996, the infection rate rose slightly (4.54% to 5.44%), but, from 1997, there was a significant drop (3.13% to 2.16%).

Agriculture↗

[Varroatosis and methods for its control].

Since 1977 varroatosis has spread over the whole Federal Republic of Germany. This mite infection of bees, which is very new in Europe, has already killed many swarms and could not be stopped by veterinary regulatory measures (notifiability, restricted movements, obligatory treatment). At present bee-keepers are trying to avoid losses by a number of biologic measures and medications. Such measures should be based on exact knowledge of the parasite and its behaviour in the bee population. The present knowledge of the parasite and of the methods of control is given.

Animals↗

Biological and behavioural studies of rodents as a basis for control.

Domestic rodents, particularly those living in urban populations, represent a serious public health problem, and effective control measures are required to deal with this threat to human health. Because of the characteristic interactions between individual animals, certain behaviour patterns occur in rodent populations that are of particular concern to control biologists. The genus Rattus is an extremely diverse group whose ecological requirements are variable and flexible, while the genus Mus, on account of its small size, limited range, and modest requirements in terms of food and water, is also very difficult to control. For any control operation a knowledge of the growth dynamics of domestic rodent populations is needed; after a period of logarithmic growth, population increases cease when the habitat is fully exploited. Consequently, control operations that merely remove some animals lead only to renewed population growth. Trapping, poisoning, and predation are traditional control measures of this kind. Environmental modification is a more certain, but more difficult, approach. The use of chemosterilants offers some hope of radical control in the future, but at present, although some field trials have been made, these substances are not available for general use, one reason being their lack of specificity. Another problem connected with the use of chemosterilants is that, on account of the sexual behaviour and physiology of domestic rodents, it would be necessary to reach nearly 100% of the population to obtain effective control.

Animals↗

[Effects of ultra low volume Beauveria bassiana oil formulation on biological diversity].

In 2001-2003, an ultra low volume (ULV) Beauveria bassiana (Bb) oil formulation was used to prevent against Dendrolimus punctatus, and its effect on biological diversity (species richness, individual number, species diversity index and evenness index, and dominant index) was investigated. The results showed that there were 473, 392 and 266 species in non-control, Bb control and chemical control areas, respectively. The individual number ratio of natural enemies to pest in Bb control area (0.1049:1) was close to that in non-control area (0.1051:1), but much higher than that in chemical control area (0.0558:1). In Bb- and chemical control areas, the species richness and diversity decreased, but dominant index increased. There existed significant difference between chemical control and non-control areas, but no significant difference was found between Bb control and non-control areas. ULV Bb had no obvious effect on the natural enemies and non-target insects.

Biodiversity↗

Selection of a nucleopolyhedrovirus for control of Spodoptera frugiperda (Lepidoptera: Noctuidae): structural, genetic, and biological comparison of four isolates from the Americas.

Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae) is the principal pest of maize in tropical and subtropical regions of the Americas. Larvae of this species are susceptible to a nucleopolyhedrovirus (NPV) which has attracted interest as a potential biocontrol agent. Four strains of NPV isolated from infected S. frugiperda larvae in the United States, Nicaragua, and Argentina were subjected to a structural, genetic, and biological comparison to select a candidate isolate for use in biocontrol experiments in Mexico and Honduras. All isolates had an occlusion body polyhedrin protein of 32 kDa, but the virions of each isolate differed subtly in the pattern and abundance of certain structural polypeptides revealed by SDS-PAGE analysis. Restriction endonuclease analysis of viral DNA confirmed that these isolates were strains of a single virus species but showed that they were not genetically homogeneous; each isolate could be differentiated from the others using common restriction enzymes. Droplet feeding bioassays indicated that an isolate from Nicaragua (Sf-NIC) and an isolate from the United States (Sf-US) had the highest infectivity when tested against 2nd instars originating from a Honduran S. frugiperda colony. No significant differences were detected in the speed of kill of Sf-NIC (102.7 h), Sf-US (102.3 h) and Sf-AR (103.4 h), whereas that of Sf-2 (97.3 h) was significantly shorter. Additional bioassays of the Sf-NIC isolate against 2nd to 6th instars demonstrated that LC50 values increased with larval stage from 2.03 x 10(5) OBs/ml for 2nd instars to 1.84 x 10(8) OBs/ml for 5th instars. The concentration required to elicit a lethal infection of 6th instars was so high that a reliable estimate of LC50 could not be obtained. The mean time to death for each stage challenged with the Sf-NIC isolate increased with instar from an average of 102.7 h in 2nd instars to 136.9 h in 5th instars.

Analysis of Variance↗

Biological control of Bactocera oleae (Diptera: Tephritidae) using a Greek Bacillus thuringiensis isolate.

Bacillus thuringiensis, isolate 114A, was used in toxicity experiments against the wild population ofthe olive pest Bactroceria oleae (Gmelin). In laboratory experiments, spores and crystals of the B.t. were delivered to the insects with the food. Longevity, oviposition period, number of eggs produced, and percent hatch were recorded. Olive fruits from the oviposition test were dipped into a suspension containing spores and crystals of B. thuringiensis 114A after the eggs were deposited. In field experiments, four to six sprayings per year of B.t. 114A isolate were applied for three successive years. It was found that, in addition to the longevity of B. oleae, the oviposition period, number of eggs and percent egg hatch decreased. Also, the percentage of pupation and emergence was reduced when olive fruits with eggs in their mesocarp were dipped in the solution of spores and crystals. Field applications with the toxins of 114A isolate of B. thuringiensis have resulted in significant protection of the olive production.

Animals↗

Control of horn fly (Diptera: Muscidae) in Florida with an Australian trap.

A newly developed Haematobia spp. trap is described, and results are presented from field trials to reduce populations of adult horn fly, Haematobia irritans L., on 5 dairy farms in western Florida and Alabama during the summer of 1992. We compared fly infestations on milkers subjected to trapping, versus either dry cattle on the same farm or milkers on a nearby farm, without the trap but where traditional horn fly control practices were used. Results gave 96.9% (95% CI, 93.8-98.4) reduction compared with dry cattle with a mean count of 228 per animal, and 90.2% (84.5-94.5%) compared with milkers on the control farms with a mean count of 113. Trapping removed the need to use insecticides to control this pest on milking dairy cattle and so offers a practical, environmentally acceptable, safe, and sustainable means of horn fly control on cattle which pass through the trap regularly.

Animals↗