But human influences can upset these balances, and this is most evident when an exotic organism is introduced on purpose or by accident. Many of the most serious pests, crop diseases or invasive weeds are the result of "introductions" from foreign lands. The newly introduced organisms find a favourable environment, free from their previous constraints, and they proliferate to achieve "pest" status. Entomologists has a useful term for this - they refer to the constraining organisms in the region of origin as "the natural enemy complex". We can define Biological control biocontrol as: the practice or process by which an undesirable organism is controlled by means of another beneficial organism. In other words, biocontrol is both a naturally occurring process which we can exploit and the purposeful use of one organism to control another.
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Although it is not a problem in its area of origin, the beetle causes serious damage in the USA. It spread rapidly from the initial sightings in New Jersey and today it is found over roughly half of the country in almost every state east of the Mississippi.
It is a problem as an adult beetle because it feeds on a wide range of ornamental and crop plants, eating the tissues between the veins, and it accumulates on ripening fruit, causing substantial damage. It is also a problem in the larval stage because the adult beetles lay their eggs in turf and the grubs destroy the grass roots. By the s, the infestation had become so extensive that a search for a control measure was undertaken which led to the discovery in nature of some diseased larvae.
Milky spore bacteria were isolated. Appearance P. Habitat A fastidious organism, P. Several amino acids are known to be required for growth, as well as the vitamins thiamine and barbituric acid.
Trehalose, the sugar found in insect hemolymph, is a favored carbon source, although glucose can also be used. Pests attacked Japanese beetle is the exclusive host of the strain of P.
However, other P. By this time, some of the cells have penetrated the gut wall and have begun to grow in the hemolymph, where large numbers of cells develop by day 5 to A few spores also are formed at this stage, but the main phase of sporulation occurs later and is completed by 14 to 21 days when the larva develops the typical milky appearance.
In laboratory conditions, the larva remains alive until this stage and usually contains about 5 x spores. In field conditions, however, there are reports that larvae sometimes die earlier, before the main phase of sporulation is completed.
This is of concern because sporulation stops when the host dies and the larva ultimately releases fewer spores to maintain the level of infestation of a site. Relative effectiveness The advantages of using commercial preparations of P. The disadvantages include the high cost of production in vivo, the slow rate of action, the lack of effect on adult Japanese beetles, which also cause obvious and distressing damage, and the need for large areas to be treated for effect see below.
The narrow host range, which is environmentally very desirable, is also a disadvantage: managers must accurately identify the infesting grub species to determine if it is Japanese beetle. If there are other grubs present, they will not be attacked. The treatment is most effective when applied on a region- or state-wide basis or at least to relatively large areas to reduce overall the levels of beetle infestation. Also, because P.
The success of the control program must be judged not on this basis but by the fact that over a number of years the mean level of pest damage is lower than it would be in the absence of P. Between and , over tons of spore powder was applied to turf in over , sites in the U.
Larval numbers in the turf decreased to fold and the population stabilized at this new low level with corresponding reductions in the levels of adult beetle damage. Recent research indicates that in some regions of the U. Only 0. Also, a recent field study in Kentucky showed that commercial formulations of P. Researchers concluded that earlier reports of success were limited to very high infestations of grubs where other stresses may have increased their susceptibility to diseases.
The cause of death in insects infected with P. Physiological starvation caused by the growth of bacterial cells in the hemolymph seems the most likely explanation, and fat reserves of diseased larvae have been shown to be much reduced compared with those of healthy larvae. However, toxins also may be involved because they have been detected in culture filtrates of the bacteria and shown to be lethal on injection.
Recently, a crystal protein from sporulating cells of P. This protein might contribute to pathogenic invasion through the gut wall.
Conservation For general information about conservation of natural enemies, see Conservation in the Tutorial section on this site Commercial Availability.
Synonyms Bacillus popilliae Paenibacillus popilliae formerly Bacillus popilliae is a soil-dwelling, Gram-positive , rod-shaped bacterium. It is responsible for a disease commonly called milky spore of the white grubs of Japanese beetles. The adult Japanese beetles pupate in July in the Northeast United States and feed on flowers and leaves of shrubs and garden plants. During this adult stage, the beetles also mate and the females lay eggs in the soil in late July to early August. The eggs hatch soon afterwards and in this larval or grub stage, they feed on the roots of grass and other plants. As the weather gets cooler and winter approaches, the grubs go deeper into the soil, and feeding declines as they over-winter. In August, when the grubs are close to the surface and feeding, they are vulnerable to infestation by milky spore.