1. What is classical biological control?

Biological control is a management strategy for controlling pests (including diseases and weeds) that uses natural enemies of those pests. In the case of an invading or introduced exotic pest, the 'classical' biological control approach is to return to the area of origin of the pest and search for enemies, such as parasitic wasps or specific predatory beetles, which can then be imported and will control the pest without any further intervention. This is the preferred method of control where applicable.

2. Why is microbial control different?

Large-scale field trials using Green Muscle against grasshoppers and locusts have consistently demonstrated efficacy similar to chemical pesticides albeit with slower action. Generally, when applied at 50 g/ha, Green Muscle causes density reductions of 80-90% in unconfined populations in 2-3 weeks. Lower doses give similar reductions though may take longer to achieve them. The slower action of mycopesticides as compared to chemical pesticides restricts their use in ecologically sensitive areas and in preventive control operations where locusts are far from crops. Most locust-affected countries favour preventive control. Grasshoppers can however be controlled closer to or even inside crops because their densities are generally lower and they are less mobile. Moreover, sick grasshoppers consume less than healthy ones.

4. Are mycopesticides in use in Europe or the U.S.?

Mycopesticides are registered and in use in Europe and the U.S. for control of a variety of pests, including aphids, whiteflies, thrips, and corn borers. One product has been registered in the U.S. for grasshopper control, but its efficacy under field conditions was not satisfactory. Another product, based on the same fungus as Green Muscle though a different strain, has been in use in Australia against various locust species and will soon be registered. Its name is Green Guard^®. Widespread use of Green Muscle in Africa and Asia and Green Guard in Australia and the Far East is likely to generate more interest in the Americas and in Europe. In fact, there are now plans to test Green Muscle in the US and Canada.

Fungal spores for aerial application are typically formulated in oil and applied with conventional spray applicators. Spray droplets land on the insect and adhere to the cuticle (the insect's "skin"). Some spores may also come in contact with the insect indirectly from sprayed vegetation, other infected insects, etc. After contact, the spores germinate and penetrate the cuticle within one day with the help of special enzymes. The infection spreads in the body cavity diminishing appetite and causing listlessness. Typically, the insect attempts to raise its body temperature to shake off the infection, usually to no avail. At the time of death, the insect may turn a reddish colour and, if it is not eaten, the fungus will grow on the outside of its body and sporulate. This makes it easy to know that the cause of death was a fungal infection.

The group of fungi to which Metarhizium belongs, are highly specific and affect mainly insects and other arthropods. Different fungus species have different hosts and even different strains or subspecies have different host ranges. There are competing interests to develop fungal strains with the narrowest host range for environmental safety and with the broadest host range for commercial potential. Intensive screening for host range allows researchers to select strains having the least effect on non-target organisms. Routinely, leading strains are tested for mammalian toxicity, avian toxicity, and other impacts. The particular strain of fungus proposed for locust and grasshopper control is highly specific to these insects. This strain and related ones have recently been placed in the variety of Metarhizium anisopliae called 'acridum'.

7. Could fungi get out of control in the environment or mutate?

Fungi come from the same environment in which they are released and quickly break down in heat and sunlight, returning to background levels within a few weeks. Although researchers would like to maximize the field life of these applications, there is little evidence of high levels of natural persistence beyond three weeks, even in humid environments. Mutation of the fungus is no more likely in a mycopesticide than in the natural environment. Moreover, genetic consistency is monitored by the manufacturer to ensure quality and reliability of the product.

8. Could exotic strains of fungus disrupt local ecology?

This depends on the definition of exotic. It is common to find the same strain of fungus in more than one region. And where there are differences, the genetic difference may be small. For example, strains isolated from grasshoppers or locusts in Australia, Madagascar, Africa and South America are remarkably uniform. The ecological zone of migratory pests like locusts, for example, is quite vast, and their natural pathogens are as widely distributed. Overly restrictive phytosanitary and regulatory procedures at the national level could encumber transnational use of strains that are effectively from the same region. In the case of Metarhizium, even truly exotic strains are not likely to have much impact where they are introduced because of their rather inefficient way of spreading between hosts. Epizootics only occur under exceptional conditions, when host density is high and the sun is covered for much of the time.

9. What are the relevant phytosanitary regulations?

In 1998, the FAO produced guidelines for transboundary transport and use of microbial pesticides. Many countries have their own guidelines and there are other regional guidelines being developed in Africa by the CILSS countries. The US has recently published its EPA regulations, which provide a very comprehensive framework.

In the short term, mycopesticides are estimated to cost in the range of $10 to $20 per ha, which is somewhat higher than most chemicals. Developments in production technology, such as the use of waste biomass substrates, combined with larger orders and competition will hopefully lead to lower prices of mycopesticides in the medium term.

11. What is the difference between grasshoppers and locusts?

From a systematic point of view, there is no difference between grasshoppers and locusts. They both belong to the order Orthoptera, suborder Caelifera, infra-order Acridodea and superfamilies Pyrgomogphoidea and Acridoidea. The two terms are mainly used to describe the remarkable differences in behaviour. Locusts just behave like grasshoppers, when they are at low population densities. They do not aggregate and form swarms. However, at higher densities, locust species become gregarious and can form large swarms. They change their behaviour completely due to changes in their hormonal system. They also change certain morphological characteristics and their colour. The capacity to build up large swarms is what makes locusts such dangerous pests. There is a whole range of species with different tendencies to become gregarious. Desert locusts become gregarious at fairly low population densities.  At the other end of the scale, Senegalese grasshoppers need much higher densities.

12. What about the future?