Biological control of mosquitoes, especially malaria vectors, Anopheles species.
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During the summer of 2002, symptoms of rust disease were observed for the first time on Phragmites australis in Saudi Arabia. Light brown lesions of regular shape indicating uredinia of Puccinia isiacae appeared on the leaves. The morphology and characteristics of the fungus were described in detail with both light and scanning electron microscopy. The possibility of using this fungus as a biological control agent was also discussed.
Fusarium head blight (FHB) of small grain cereals and ear rot in maize are significant diseases across the world. Infection can not only result in reduced yield as a result of shrunken grains but also result in reduced milling and malting quality and the contamination of grains with mycotoxins. Mycotoxins are hazardous to animal and human health. Therefore, guidelines and legislation are in place, or under consideration, in most countries to protect consumers and animal welfare. As fusarium mycotoxins are produced within the growing crop, it is important to understand how agricultural practices affect mycotoxin contamination of grain. Such information could then be used to determine guidelines on "Good Agricultural Practice" (GAP) to minimise the mycotoxin contamination of cereal products. Evidence is provided to show the importance of choice of cultivar, crop rotation, soil cultivation, fertiliser and the chemical and biological control of insects, weeds and fungi.
Urban populations of Canada geese, Branta canadensis, pose a nuisance problem throughout most of the eastern United States and in other parts of the United States and Canada. Puccinellia arctica is a species of arctic grass that is unpalatable to Canada geese on the North Slope of Alaska and may prove to be an effective long-term and nonlethal means of controlling the growing populations of urban Canada geese. A comparative study of the secondary metabolites of both P. arctica and Puccinellia langeana and Poa pratensis, two palatable grass species that Canada geese generally consume, revealed no significant differences. However, ellagitannin levels were higher in P. arctica than in the palatable grass species and may be contributing to its unpalatability to Canada geese. These results support the potential to use P. arctica in public areas to control geese intrusions.
The astigmatid mite, Psoroptes ovis (Hering) (Acari: Psoroptidae), is an obligatory ectoparasite that causes psoroptic mange in a range of domesticated animals, particularly sheep, where the clinical disease is known as sheep scab. A series of laboratory assays were used to assess the use of the fungus, Metarhizium anisopliae (Metchnikoff) (Deuteromycotina: Hyphomycetes) as a biocontrol agent for P. ovis derived from rabbits (syn. P. cuniculi). The immersion of mites in a suspension of conidia of M. anisopliae resulted in the acquisition of fatal infections. The number of mites which developed infections increased significantly with the increasing concentration of the conidial suspension to which they were exposed; 77% of mites developed infections when exposed to the highest concentration used (1 x 10(8) conidia ml(-1)). Controls developed no fungal infections. Mites allowed simply to walk across a surface which had been treated with a suspension of conidia also acquired fungal infections; the number infected was again related to the concentration of conidia present. After contact for 24 h with a surface treated with 1 x 10(8) conidia ml(-1), 73% of the mites became infected. To determine whether dead infected mites could act as sources of infection, infected cadavers were placed in chambers with live uninfected mites. The uninfected mites acquired fatal infections from the cadavers; a higher ratio of infected cadavers to uninfected mites resulted in greater transmission of infection. The time after death of the infected cadaver was also an important factor influencing the number infected, 5-day-old cadavers were the most infective and 18-day-old cadavers the least infective. The results indicate that M. anisopliae is a good candidate control agent for Psoroptes mites.
It is now well established that pathogens such as viruses, fungi bacteria and protozoans can have profound effects on the dynamics of their invertebrate host populations. Theoretical models of invertebrate host-pathogen interactions which assume uniform structure of the pathogen population may reasonably explain the oscillatory behaviour observed in some systems, but do not adequately describe the existence of more constant populations found in other host-pathogen interactions. An examination of the literature relating to these relatively stable systems suggests that the common thread is the eventual transmission of some of the more protected, longer-lived stages of the pathogen occurring in reservoirs, such as the soil, host cadavers on trees, or the live host itself. In this letter, I propose a new theoretical model which incorporates this population structure and accounts for the range of dynamics observed in natural systems. In particular, I show that host populations may be regulated to low and relatively constant densities if sufficient numbers of pathogens are trans-located from pathogen reservoirs to habitats where transmission can occur. An understanding of pathogen reservoirs may be of value in the design of biological control programmes and may greatly increase the effectiveness of pathogens as biological control agents.
In laboratory trials, Muscovy ducks, Cairina moschata L., removed adult house flies, Musca domestica L., at least 30 times faster than commercial bait cards, coiled fly paper rolls, fly sheets, or fly traps. The LT90 for ducks in 0.24-m3 cages with 100 flies was 0.6 h compared to 15.3 h for the most effective commercial device. Ducks survived for at least 12 wk in pens with calves, without injury or feed supplement. Ducks ingested a mean of 25 house flies per 15-min observation period when populations were low to moderate. The economics and advantages of Muscovy ducks as part of a management program for house fly control are discussed.
Chemical insecticides and entomopathogenic nematodes have been independently used to suppress corn rootworm damage in maize. We report on the mortality response of larvae of the western corn rootworm, Diabrotica virgifera virgifera LeConte, to the combined treatment with 1 of 3 insecticides (terbufos, fonofos, and tefluthrin) and the entomopathogenic nematode Steinernema carpocapsae Weiser (Mexican strain). Corn rootworm mortality with combinations of the insecticides terbufos or fonofos and S. carpocapsae was typically additive for the 2 agents. Evidence of antagonism between these agents was sometimes observed. The combination of tefluthrin with S. carpocapsae frequently resulted in a synergistic response and a 24% average increase in expected mortality. The influence of the tefluthrin appears to be isolated to an effect on the rootworm larvae. Synergism also was observed when tefluthrin was combined with the nematode Heterorhabditis bacteriophora Poinar (Lewiston strain). The combined use of tefluthrin with an entomopathogenic nematode may offer an integrated approach to increase the efficacy of entomopathogenic nematodes for insect control.
The autosomal recessive allele v wing (v) in the Mediterranean fruit fly, Ceratitis capitata (Wiedemann), produces flies that when reared at 30 degrees C have stubby wings. The mutant was used to construct a translocation-based genetic sexing system in an attempt to improve the efficiency and effectiveness of the sterile insect release method for field control.
Helical replicative forms, but not the persistent non-replicative forms, of Spiroplasma taiwanense Abalain-Colloc et al. (isolated from the mosquito Anopheles sinensis Wiedemann in Taiwan) were shown to reduce significantly the survival of Aedes aegypti (L.) mosquito larvae reared in 10 ml of water with 0.3 ml of S.taiwanense suspensions added on days 0 and 3. The suspensions contained, respectively, helical forms at a concentration of 10(9) Colour Change Units (CCU)/ml and persistent forms at 10(6) CCU/ml. It is suggested that S.taiwanense, or toxins produced from it, are potentially useful for use in integrated mosquito control programmes.
Although the number of biocontrol products is increasing, these products still represent only about 1% of agricultural chemical sales. Yet these are important contributions because biocontrol agents offer disease management alternatives with different mechanisms of action than chemical pesticides. Trends in research include the increased use of biorational screening processes to identify microorganisms with potential for biocontrol, increased testing under semicommercial and commercial production conditions, increased emphasis on combining biocontrol strains with each other and with other control methods, integrating biocontrol into an overall system.
In this paper, the pathogen, pathogentic regularity of disease of introducing medicinal plants in South China Botanical Garden were reported. And it is suggested that some measures should be taken to control them.
Concentration of glycogen, maltose, and trehalose as well as the activity of hydrolases catabolising them: alpha-amylases, glucoamylase, maltase, and trehalase were studied during a 48 h infection of Galleria mellonella (Lepidoptera) instar larvae infected with infective Heterorhabditis zealandica (20 nematodes/insect). The content of trehalose in the infected insects during the first day of infection was higher (p < 0.05) than in the controls. The concentration of maltose and glycogen were similar in both groups despite the fact that the activity of all examined alpha-glycosidases was generally much higher in the infected insects than in the controls.
Recently, because of concern about the effects of insecticide on the environment, increased attention is being given to the use of biological agents for controlling the vectors of human disease. Biological control may encompass the use of predators, pathogens, parasites, pheromones, insect growth regulators, and other factors. Of these agents only fish and bacteria have so far been used operationally in mosquito control. Since 1988 fish have been employed for controlling Aedes larvae in water containers in Liuchiu, Pingtung. A review of larvivorous fish (mainly Gambusia affinis) and the present status of the use of fish in mosquito control in Mainland China are thus made for ready reference for the workers in mosquito control in Taiwan.