Ibrahim, Yusof

Universiti Putra Malaysia Institutional Repository

R&D at UPM: Research SnapshotsEntomopathogenic Fungal Formulations ofMycoinsecticidesYusof Bin IbrahimSynthetic chemical insecticides have been the mainstay of insect pest control for more than 50 years.However, the increasing cost of development, pest resistance and resurgence and increased awareness ofthe environmental effects of excessive dependence on these chemicals have ensured a continuing interest inalternative forms of pest control. Biological control agents such as entomopathogenic fungi have playedimportant roles in the history of microbial control of insects. The first practical attempt was conducted byMetschnikoff in 1879, and then repeated by Krassilstichik in 1888, when Metarhizium anisopliae was usedagainst the cockchafer larvae, Anisoplia austriaca, and the weevil, Cleonus punctiventris (Robert & Hum-ber,1981).In Malaysia, the first use of a fungus against insects was reported by Ooi (1979) when Entomophthorasphaerosperma was applied against Plutella xylostella. The second publication was only available 14 yearslater when Ibrahim and Low (1993) reported the successful use of Beauveria bassiana and Paecilomycesfumosoroseus against P. xylostella. Entomopathogenic fungi are gaining increasing attention worldwide asagents for biological control and some have been developed for large-scale commercial production as my-coinsecticides. Uniquely, unlike bacteria or virus, fungi do not have to be ingested; hosts are invaded di-rectly through the integument or natural openings such as spiracles. Therefore, they can infect non-feedingstages such as the eggs and pupae. This manuscript presents a summary of my works on selected isolatesof entomopathogenic fungi against various insect pests and mites.Insects, Mites and Fungal Culture: Cultures of insects and mites were maintained in the laboratory un-der an ambient environment of 28 ± 2 C, 85 ± 15% RH and 12 h photoperiod. When required distilled wa-ter and 5% (w/v) honey were also provided separately as food for the adult insects. All the fungal isolateswere maintained on PDA or SDA in the Entomology Laboratory of the Department of Plant Protection,Faculty of Agriculture, Universiti Putra Malaysia. Fungal inocula were prepared from 3-4 week old sporu-lating cultures suspended in 0.05% aqueous Tween 80. A Neubauer haemocytometer was used to estimatethe respective initial conidial concentrations and subsequent appropriate dilutions were prepared thereof.Dosage-Mortality Bioassay: As a general approach, the test insects were placed either on a "leaf prepa-ration" or on a leaf disc as in the case of spider mites. The dosage-response assays included at least seveninoculum dosages plus a sterile cont rol of 0.05% aqueous Tween 80. Inoculation was done by spraying aminimal amount, 0.05 ml or less of the conidial suspension with a Sigma" hand atomiser that delivered aneven droplet spray of 79 11m(VMD). Mortality, including moribund individuals, was recorded daily for 4-12 days depending on the test subjects. The ECsos and LTsos are obtained through a probit programme(S 103, Statistical Research Service, Canada DOA, unpublished) based on probit analysis by Finney (1971).100ResearchCluster-.I4'~. 7-' euut 7~Formulations and Field Trials: Four formulations of microbial control agents have been developed.Dust, wettable powder and oil formulations use conidia as the infective agent, while granular formulationused mycelia as the source of inoculum. Tests for their favourable physical traits and shelf life are still inprogress. Field trials have been carried out against P. xylostella, Crocidolomia binotalis, Phyllotretastriolata and Aleurodicus dispersus. Similar experiments are currently being conducted against Polyphago-tarsonemus latus and Tetranychus urticae Koch complex, followed by Epilachna indica and the aphids inthe future. Please refer to Ibrahim & Low (1993), Ibrahim & Yew (1994), Ibrahim & Hashim (1998), Ibra-him & Tan (1999), Ibrahim & Liu (2001), Hashim & Ibrahim (2002), Priyatno & Ibrahim (2002, 2003),Ibrahim & Yeong (2002), Ibrahim (2002) and Ibrahim & Nugroho (2002) for further details.Dosage-Mortality Bioassay: In general, all the three species of fungi inflicted significant mortality onthe insects and mites tested. A concentration of 2 x 107 conidia mL-1 was adequate to provide good kill, andsignificant relationships at P = 0.05 were obtained between log concentration and probit mortality valuesfor all the three fungal species. This indicates that infections increased significantly with increasing con-centration. The median effective concentrations, EC50 values, were very encouraging; generally reached 3days after treatment (refer to LTsos). This enhances the potential and the desire to minimise the use or re-place chemical application by microbial control.Formulations and Field Trials: Field tests using formulated conidia has been limited to cabbage caterpil-lars, flea beetles, whiteflies, termites, stored products insects and mites. Conidia of P. fumosoroseus inVesawit'" palm oil (rf. no. 2) worked very well against C. binotalis but not as encouraging against P.striolata and A. dispersus. The granular formulations were more successful against the termites (rf. no. 12).Current field tests with the wettable powder formulation have shown encouraging recovery of broad miteinfested chilli shoots sprayed with B. bassiana and P. fumosoroseus, while the rice worm Corcyra cepha-lonica was very susceptible to the dust formulations of B. bassiana and P. fumosoroseus.Reader EnquiryDepartment of Plant ProtectionFaculty of AgricultureUniversiti Putra Malaysia43400 UPM, Serdang, SelangorMalaysiaTel: +603 89467249E-mail: yusofib@agri.upm.edu.my101

Entomopathogenic fungal formulations of mycoinsecticides

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Entomopathogenic fungal formulations of mycoinsecticides

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