Pakistan Journal of Nematology, 2015, Vol. 33(2): 205-211 205 Effect of time on the degradation of Pasteuria penetrans-infected females of Meloidogyne javanica and the proportion of parasitized nematodes in the roots of tomato planted subsequently D.A. Darban † , S.R. Gowen, B. Pembroke, F. Hussain 1 and R.A. Memon 2 Department of Agriculture, School of Agriculture Policy and Development, The University of Reading, Earley Gate P.O. Box 237, Reading Rg6 6AR, UK. 1 Department of Agriculture & Agribusiness Management, University of Karachi-75270, Pakistan 2 Institute of Plant Sciences, University of Sindh, Jamshoro, Pakistan † Corresponding author email: d_darban@hotmail.com Abstract Different parameters were evaluated to confirm that how long Pasteuria penetrans infected Meloidogyne javanica females took to degrade and for spores to be released from the cadavers into the soil. Regression analysis was carried out to compare the degradation of P. penetrans infected females cadavers in different time intervals over two crop cycles. There were highly significant decreases in the total number of egg-masses per plant between the 3 weeks and other treatments. Infected females (%) over both crop cycles were compared by the estimated coefficients of the fitted lines and increased significantly with degradation period and significantly higher in the second crop. The 3 week duration apparently allowed more spores to disperse which was reflected in the observations of more infected female nematodes and reduced numbers of egg-masses and total females per plant compared with the first crop. The results of this experiment suggest that dispersal of spores from the degrading females occurs after 2 weeks and this is reflected in a significant reduction in egg-masses, galling and the female population between the 1 week and 3 weeks treatments. The greatest percentage of infected females and numbers of endospores were recorded in that treatment where P. penetrans infected females were left to degrade for 3 weeks. Key words: Root-knot nematodes, Pasteuria penetrans, degradation, infected females, biological control. Much more effort has been taken since a long to understand the biology of P. penetrans isolates which parasitize the economically important root-knot nematode species. P. penetrans is a potentially good bio-agent to control root-knot nematodes (Darban et al., 2005, Gowen & Ahmed, 1990). It has many attributes required by a successful biological control agent. The spores adhere to with the cuticle of second stage juveniles of Meloidogyne spp., (Stirling, 1984; Davies et al., 1988) in soil when they search for host roots. These juveniles when invade roots and begin to develop, the parasite is also developing. At maturity they destroy reproductive system of females and infected females were unable to produce eggs and so the build-up of nematode populations prevented (Mankau, 1980; Sayre, 1980). Invasion of roots may be reduced by the spore burden. The number of infected females increases with increasing spore attachment on the juveniles (Stirling, 1984; Davies et al., 1988). However, the germination of a single spore was enough to create infection in a Meloidogyne sp., female (Stirling, 1984). Pasteuria penetrans completed its life cycle inside the female and mature spores are released when the females degrade (Sayre, 1980). Oostendorp et al., (1990) reported that spores of P. penetrans have survived for several weeks in dry, moist and wet soils and in soils with fluctuating moisture levels without loss of their ability to attach to their nematode hosts, which is a particularly useful attribute for a biological control agent (Stirling, 1991). In this experiment