Effect of soil temperature and moisture on survival and infectivity of Metarhizium anisopliae to four tephritid fruit fly puparia S. Ekesi, * N.K. Maniania, and S.A. Lux International Centre of Insect Physiology and Ecology (ICIPE), P.O. Box 30772, Nairobi, Kenya Received 31 December 2002; accepted 17 March 2003 Abstract The infectivity of 4 isolates of Metarhizium anisopliae to puparia of Ceratitis capitata treated as late third-instar larvae in un- sterilized soil was investigated in the laboratory under controlled temperature and moisture. At 20–30 °C, mortality in puparia was highest at water potential of )0.1 and )0.01 mega Pascal (MPa) and lowest at water potential of )0.0055 and )0.0035 MPa in all the isolates. In wetter soil however, isolates ICIPE 20 and 60 caused significantly higher mortality than ICIPE 18 and 69. The survival of conidia in drier soil ()0.1 MPa) was not adversely affected at all temperatures. However, in wet soil ()0.0035 MPa) there was drastic reduction in colony counts in ICIPE 18 and 69 at 25 and 30 °C but conidial density in ICIPE 20 and 60 remained at the initial level at 14 days after inoculation at all temperatures. When ICIPE 20 was evaluated against three other fruit fly species (Ceratitis cosyra, Ceratitis rosa, and Ceratitis fasciventris), significant reduction in adult emergence and higher pupal mortality occurred in C. cosyra and C. fasciventris than in C. rosa at a combination of 15 and 20 °C and )0.1 and )0.0035 MPa. However, at higher temperature and the same moisture level, the isolates were equally pathogenic across the 3 species. It is probable that in addition to pathogen cycling and multiplication from dead infected insects in the soil, a balance between microbial degradation and replenishment of inoculum of virulent isolates occur through fluctuations in, and intricate interactions between temperature and moisture levels. This study is indicative of the potential of using isolate ICIPE 20 for soil inoculation against pupariating third-instar larva of fruit flies, thus providing a novel alternative to chemical soil application. Ó 2003 Elsevier Science (USA). All rights reserved. Keywords: Metarhizium anisopliae; Ceratitis; Fruit flies; Puparia; Mortality; Temperature; Moisture; Soil 1. Introduction In Africa, fruit production and export is an impor- tant source of income generation with export mainly targeted at large markets in Europe and the Middle East. Several species of fruit flies (Diptera: Tephritidae) including Ceratitis capitata (Weidemann), Ceratitis co- syra (Walker), Ceratitis rosa Karsh, Ceratitis fasciventris (Bezzi), and Ceratitis anonae Graham traverse most of the national boundaries in Africa and pose serious threat to fruit production. For example, in Kenya, about 90,000 tons of mangoes are produced annually but an estimated 20–40% is lost to fruit fly infestation, and in some locales, as much as 80% yield loss has been recorded (Lux et al., 1998). The damage is caused by gravid females that oviposit under the skin of healthy and damaged fruits where the eggs hatch and the larvae feed on the decaying flesh of the fruits. The fruits be- come rotten and inedible or drop to the ground pre- maturely causing the large economic losses. Other losses result from quarantine restrictions imposed by import- ing countries to prevent entry and establishment of the fly. During development, third instar fruit fly species drop from fruits to the ground, burrow into the soil and form a puparium (White and Elson-Harris, 1992). An important part of fruit fly suppression and eradication programme, therefore, include soil treatment with in- secticides beneath host trees to kill fruit fly larvae and puparia (CDFA, 1993; Mohamad et al., 1979; Roessler, 1989; Saul et al., 1983). Currently, the organophosphate Journal of Invertebrate Pathology 83 (2003) 157–167 Journal of INVERTEBRATE PATHOLOGY www.elsevier.com/locate/yjipa * Corresponding author. Present address: Plant and Invertebrate Ecology Division, Institute for Arable Crop Research (IACR), Rothamsted, Harpenden, Hertfordshire AL5 2JQ, UK. Fax: +44- 1582-467490. E-mail address: sunday.ekesi@bbsrc.ac.uk (S. Ekesi). 0022-2011/03/$ - see front matter Ó 2003 Elsevier Science (USA). All rights reserved. doi:10.1016/S0022-2011(03)00069-7