Prospects for microbial control in West Africa

The prospects for development of microbial control in West Africa are bright, with many stakeholders in plant protection both within and beyond the region becoming increasingly interested. To date however, on the West African market, there are only two microbial products available, and many opportunities remain to be fully explored. Apart from commercially oriented pathways, alternative methods of pathogen propagation and implementation are being studied, to serve the needs of those agricultural sectors which do not provide sufficient profit margins, such as the mainly traditional subsistence systems. Several groups are developing common regional registration frameworks for pesticides, and the need for adapted regulations and guidelines for microbial products is being addressed. This is a strong opportunity for creating a framework which does not only promote commercial products, but also alternative implementation pathways

Development and commercialization of the green muscle biopesticide

Locusts are the most feared pests of farmers living around the world’s major deserts. Millions of liters of environmentally damaging pesticides are sprayed over vast areas of land to control them and their grasshopper cousins. This paper tells the life history of the LUBILOSA (Lutte Biologique contre les Locustes et Sauteriaux) project, set up in 1989, and the development of a biological pesticide which kills locusts and grasshoppers without harming the environment. Commercial manufacture and real adoption has begun, although the benefits have yet to pay for the US$15 million spent on the project. The project has had some major spin-offs including the development of a similar biopesticide in Australia, and the development of biopesticides to control termites. Good science alone has by no means been the only ingredient of the success so far. One crucial factor has been the willingness of donors to provide funding for the 10 years of research and development often required to turn basic research into a useful product. A second factor is the early forging of partnerships between donors, several research institutes, national agricultural research and extension systems (NARES), nongovernmental organizations (NGOs), the Food and Agriculture Organization of the United Nations (FAO), private sector companies, and farmers that has ensured that sufficient expertise was available when needed. A by- product of this collaboration is the creation of a “constituency of support” around Green Muscle® and it is this constituency which, more than anything, will determine the eventual impact and return on investment of the LUBILOSA project. This is because the eventual level of sales of Green Muscle depends on the correction of the market failure whereby the human and environmental health costs of spraying chemical pesticides are not charged to the purchaser. Policy change is required to correct this and it is in the constituency’s power to bring about this policy change. LUBILOSA project management and donors have shown themselves very aware of this reality by proposing and funding a “stewardship” phase for the project to both lobby the constituency and keep it together during the early adoption 4 phase, as well as to ensure a seamless transfer of researcher knowledge about Green Muscle to the private sector manufacturers. The need for product “stewardship” or “championing” has long been recognized in the private sector but has been absent from a research world which has attempted, until recently, to separate “upstream” basic research from “downstream” adaptive research and extension. Product championing may well be essential for creating and cementing synergies between the public and private sectors and between scientific “knowledge” and practical “know-how”

Effects of rehydration on the conidial viability of Metarhizium flavoviride mycopesticide formulations

The rehydration of dried conidia of Metarhizium flavoviride was investigated in an attempt to increase speed of kill of locusts and grasshoppers by formulations of this fungus. Conidia were dried to 4-5% moisture content with no apparent adverse effects on viability, but rapid rehydration (by putting dried conidia directly in free water) reduced viability. Rehydration in an atmosphere of high humidity allowed dry conidia to absorb sufficient moisture to avoid imbibition damage. Rehydrating and pre-germinating conidia prior to spraying (in an oil-based formulation) on to the desert locust, Schistocerca gregaria, did not decrease the time to death, suggesting that moisture uptake by dry conidia on the desert locust cuticle is easily achieved

Behavioural fever in the Senegalese grasshopper, Oedaleus senegalensis, and its implications for biological control using pathogens

1. Thermoregulatory behaviour of the Senegalese grasshopper, Oedaleus senegalensis (Krauss), was investigated in the field following a spray application of an oil-based formulation of Metarhizium flavoviride Gams and Rozsypal in Niger, West Africa. 2. Measurements of environmental temperature, wind speed and solar radiation were made in conjunction with measurements of internal body temperatures of grasshoppers from a control (unsprayed) and treated plot using microthermocouples and hand-held thermometers. Grasshoppers were monitored for 4 days from the third day after application. 3. Oedaleus senegalensis utilized a range of thermoregulatory behaviours to maximize body temperatures during periods of low insolation and ambient temperature, and to minimize excessive heat loading during the hottest periods. Preferred body temperature of uninfected grasshoppers was 39 °C, with a range from 24 °C in the early morning to a high of 46 °C during periods of high insolation and ambient temperature. 4. Infected grasshoppers altered their thermoregulatory behaviour and showed a behavioural fever response to the pathogen. Preferred body temperatures of infected individuals were raised to a new set point of ≈ 42 °C. This is believed to be the first evidence for a behavioural fever in response to a microbial infection for any natural population. In the present study, its effects appeared to provide little therapeutic advantage to hosts infected following application. Preliminary evidence from other studies, however, indicates that modifications to host thermoregulation could be a significant constraint to the pathogen and may limit its impact under certain conditions

Evaluating the effects of a biopesticide on populations of the variegated grasshopper, Zonocerus variegatus

A field trial was conducted to investigate the efficacy of an oil formulation of the fungal entomopathogen, Metarhizium flavoviride, for control of the variegated grasshopper, Zonocerus variegatus. The results of the trial showed a significant reduction in grasshopper populations following spray application compared with non-treated controls. 2. Further studies revealed that there was significant movement of insects into and out of the treated plots during the course of the experiment, and that the pathogen spray residue remained infective for several days after application. 3. To help interpret these data and link them more closely to the basic population counts, insect-pathogen models were developed which accounted for the effects of secondary pick up of spores, insect movement and mortality on disease levels observed in the field. These revealed that contact with spores from the spray residue was an important route of infection for insects moving into the treated areas after spraying. They also revealed that there was an increase in disease incubation periods in the field compared with the laboratory; this slowed mortality rates. 4. Overall, the combination of laboratory, field and theoretical studies suggested that the total impact of the M. fiavoviride-based biopesticide was very high. This combination of techniques revealed considerably more information than the indi- vidual indicators of efficacy commonly used to assess biopesticide applications. As such, this study demonstrates how basic ecological approaches can be of value in an applied context, helping to provide a link between laboratory and field studies, and aiding the interpretation of complex field trial result

Thermal ecology of Zonocerus variegatus and its effect on biocontrol using pathogens

1 Thermal behaviour of the variegated grasshopper, Zonocerus variegatus, was investigated in the humid tropical zone of southern Benin, west Africa, in the dry seasons of 1996 and 1998. In 1998, investigations included studies of a population of grasshoppers sprayed with an oil‐based formulation of the entomopathogenic fungus Metarhizium anisopliae var acridum. 2 Body temperature measurements and observations of thermal behaviour both in the field and on thermal gradients in the laboratory, suggest that Z. variegatus was not an active behavioural thermoregulator. Although it did show shade‐seeking behaviour at high temperatures, no overt behavioural postures or microhabitat selection associated with heat gain and elevation of body temperatures was observed. Moreover, no alterations to thermal behaviour were found in response to infection by Metarhizium. 3 Body temperatures exhibited by Z. variegatus in the field will lengthen disease incubation of M. anisopliae var acridum compared with laboratory maintained, constant temperature conditions and may have a significant impact on pathogens with a lower thermal tolerance. 4 Habitat structure appeared to be an important factor determining the extent of body temperature elevation. The effect of habitat differences on infection and growth of M. anisopliae var acridum and other entomopathogenic fungi is discussed

An assessment of the impact of biological and chemical grasshopper control agents on grounddwelling arthropods in Niger, based on presence/absence sampling

Medium-scale experimental field applications of two grasshopper and locust control agents, the mycoinsecticide Metarhizium anisopliae (flavoviride) var. acridum (Deuteromycotina: Hyphomycetes) and the organophosphate fenitrothion, were carried out in August 1996 in Maı̈ne Soroa, Niger. The objective was to evaluate effects and side-effects on target grasshoppers and epigeal non-target arthropods, using simple binary (presence/absence) sampling techniques. Plots (≈50 ha, 3 replicates) were treated at standard recommended dose rates of 5 × 1012 spores/ha (Metarhizium) and 250 g a.i./ha (fenitrothion). The frequency of occurrence – or total presence – was used as a measure of relative population density. The fauna was monitored at 5 day intervals for 36 days (5 d before and 31 d after treatment) and again in August 1997, using 40 miniature pitfall traps per plot and sampling date. Presence/absence sampling proved appropriate to detect and quantify pesticide effects, and the use of similar techniques in rapid risk assessment programs (RAPs) for locust and grasshopper control is recommended. Both control agents were effective against grasshoppers, reflecting their inherent mode of action and speed of kill. The efficacy of fenitrothion ranged from 75 to 86% over the 31 d post-treatment period. Metarhizium had an efficacy of 76% during the last sampling period (days 21–31). Differences between treatments were not significant during this phase. The non-target arthropods monitored on species or species group level represented four insect families which together made up about 75% of the total catch: Carabidae, Tenebrionidae, Formicidae and Ephydridae. 75% of these taxa were significantly reduced by fenitrothion. The median effect was 69% (first week), 33% (second week) and 51% (third to fourth week), respectively, and fenitrothion was classified as `medium risk'. Most of the non-target fauna had fully recovered after 31 days, but one ant species was still significantly reduced in 1997. None of the taxa monitored proved susceptible to the mycopesticide. The median effect was <25% and the product was classified as `low risk'. The field trials provided further evidence that M. anisopliae var. acridum can be as effective as organophosphates without threatening non-target arthropods other than orthopterans