Volume 36, Issue 1
July 1952, pages 1-42
pp 1-11 July 1952
pp 12-18 July 1952
Stenobracon deesæ (Cam.) is a potentially effective larval parasite of sugarcane and maize borers.
The equipment and methods used in the mass propagation of the parasite,S. deesæ, are described in some detail. A suitable laboratory host for the propagation of the parasite in the laboratory has been discovered in the larva of the Rice moth,Corcyra cephalonica Stn. The method of exposing the factitious host (Corcyra) in artificial tunnels prepared in sugarcane stem is described. Fersh frass of the natural hosts (Chilo orArgyria) is used to stimulate the female parasite to oviposit on the factitious host, in the laboratory. Laboratory-bred alternate host material is supplemented by field collected natural hosts.
It was found that a single parasite grub requires more than oneCorcyra larva to complete its development.Corcyra larva previously paralysed by another braconid parasite (Bracon gelechiæ), is given to the parasite grub, one by one until it becomes full fed.
The percentage of females bred onCorcyra is very low and one of the main factors responsible for this, appears to be the nutritionally incomplete quality of the host-supporting medium. The normal percentage of females is restored by putting theCorcyra- bred adults to oviposit and breed on the natural hosts.
pp 19-33 July 1952
A study on the effects of certain micro-elements—Al, B, Co, Li, Mn, Mo, Ni and Zn—on soil bacteria, actinomycetes and fungi in the soil has been made.
The occurrences of these groups of micro-organisms were found to be significantly influenced by the amendments.
The bacterial numbers increased enormously in the Mn amended soils. This was closely followed by B, and by Zn, Mo and Li to a lesser extent. Ni, Al and Co exerted an adverse influence on the bacterial population of the soil.
The statistical interpretation of the results clearly indicated the marked significance of all the three factors,viz., Micro-elements, concentrations, incubation periods and also the following interactions: Micro-elements × Concentrations Micro-elements × Incubation periods
The numbers of actinomycete colonies were observed in greater numbers in soil samples amended with Li and to a lesser extent with Mn, B and Co.
The micro-elements with the exception of Zn and Ni increased considerably fungal numbers in the soil. Li showed fivefold increase in fungal numbers and as much as threefold increase in Mn, Mo, Co, B and Al as compared with the unamended control.
pp 34-42 July 1952