Environmental Impact of Baculoviruses

Introduction This review examines the environmental impact of baculovirus use but does not take a predictive approach to risk assessment. It is primarily intended as a compilation of information to aid decision-makers in developing countries that are considering use of baculoviruses for insect pest control. Emphasis is placed on the impact on non-target organisms of wild-type viruses, currently the only form of baculovirus used in practice for pest control. Wild-type baculoviruses are those which have been taken directly from the field without undergoing selection or improvement prior to mass production and application. However, consideration is also given to the environmental implications of cloned or genetically engineered baculoviruses, now being developed for increased uniformity and speed of action, although they are unlikely to be used in the near future in developing country situations. Many insect pathogenic viruses show similarities to viruses found in vertebrates or plants: Entomopoxviruses, cytoplasmic polyhedrosis viruses (CPV resemble the reoviruses such as the bluetongue virus and rice dwarf virus), densonucleus virus, small RNA viruses, and iridoviruses (similar to the icosahedral cytoplasmic deoxyriboviruses of fish, frog and green algae). Kurstack and Tijssen (1982) believe that only viruses that differ from those of non-target organisms should be considered for field-use pesticides. And even then only after very stringent investigations of possible deleterious effects on non-target organisms, although some viruses from this group (the CPV for example) have been used in biological control. A factor that will most favour the potential success of viruses is their relative lack of adverse effects on the environment compared to chemical insecticides. Overall, the environmental effects after releases of insect viruses have not been comprehensively studied, but the observed effects have been minimal. Their major environmental effects are simply the ones for which release is intended, namely, reduction in insect populations and subsequent reduction of damage to crop plants. They can also indirectly reduce populations of beneficial, entomophagous or entomogenous organisms by reducing the population of the common host insect, though this effect is seldom as severe as with chemical insecticides (Fuxa, 1990). Some thirty years ago Tinsley and Melnick (1973) reminded us that while insect viruses could be useful, the release of living organisms into the environment should not be taken lightly and that at the time the direct evidence of safety came from absence of obvious disastrous effects. They highlighted three potential hazards from the deliberate release of baculoviruses: (1) the infection …