Biological control

Abstract

The invention relates to a non-human multicellular organism carrying a dominant lethal genetic system, the lethal effect of which is conditional, wherein the lethal effect of the lethal system occurs in the natural environment of the organism.

Description

[0001] The present invention relates to a method for controlling the population of an organism.[0002] Methods of biological control are known for insects and plants. One method currently employed for the control of insect populations is termed the "sterile insect technique" (SIT), also known as the "sterile insect release method" (SIRM). In this method, sterile males are released into the environment, wherein they compete with the wild-type (fertile) males for mates. Females which mate with sterile males produce no offspring, and the release of large numbers of sterile males, therefore, leads to a decrease in the size of the next generation. In this way the size of the wild population is controlled.[0003] SIT requires some mechanism for insect sterilisation. In addition, SIT commonly also employs separation of males from females, with the release of only one sex. This is desirable in the case of an agricultural pest, such as the medfly, where the female damages fruit, even if the fe...

AI Technical Summary

Benefits of technology

[0092] In one aspect the invention relates to a non sex-specific system, in which both males and females are killed by the lethal genetic system. Such an approach is preferred in certain organisms. In such a case, one advantage of the invention lies in the avoidance of sterilisation by irradiation. By way of example, mixed sex releases are preferred in pink bollworm (a lepidopteran pest of cotton), but irradiated moths are estimated to suffer at least a 10 fold reduction in effectiveness as a consequence of the irradiation due to loss of vigour and reduced life span. Similar advantages are predicted in other organisms. In medfly, irradiated males are about 50% less effective than the non-irradiated equivalent in competitive mating tests and they live 3-5 days instead of the non-irradiated 10-15. This gives a composite 410 fold potential performance improvement by avoiding irradiation.

Problems solved by technology

Females which mate with sterile males produce no offspring, and the release of large numbers of sterile males, therefore, leads to a decrease in the size of the next generation.

In some cases it is possible to separate males and females by criteria such as pupal mass or time of eclosion, but these methods are unlikely reliably to yield a truly single-sex population.

Separation of males and females often involves the use of mutant strains, which have been mutagenised to induce a visible or otherwise selectable difference between the sexes, but such mutagenesis can reduce the fitness of the resultant stock with respect to the wild type, which is undesirable.

Frequently, the doses of chemicals or the dose of radiation required to induce sterilisation are very similar to that which is lethal for the organisms As such, sterile organisms are frequently impaired in their ability to mate.

Furthermore, both chemical and irradiation methods utilise technologies which are not specific to the target organism, with consequent potential danger to workers.

Both methods produce an environmental hazard, as the irradiation source or chemicals will need to be disposed of In addition, there are inherent dangers and additional labour costs in the use of an irradiation source such as a strontium source.

However, this method can be ineffective due to varying field conditions, where the environment does not provide suitably cold conditions.

Moreover, organisms that live in a range of temperature habitats may not be controlled under all conditions.

However, this method suffers from the drawback referred to above, in that released flies have reduced fitness due to the sterilisation treatment.

As a result, for a female specific lethal genetic system, all females which result from the mating are then killed or rendered non viable due to the action of the genetic system, while the males survive to pass on the system to the next generation in a proportion of cases.

Moreover, the released larvae will compete with the larvae of the wild population, increasing mortality through density-dependent mechanisms.

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