Category Archives: Volume 9 No. 3 (1987)

Note: Use of Paraaminobenzoic Acid to Improve Yield of Silkworm (Bombyx mori L.)


Author(s): I.K. Pai, S.N Hegde and N.B Krishnamurthy

Abstract

Paraaminobenzoic acid (PABA) at 50, 100, 200 and 400 ppm concentration were administered to third instar larvae of silkworm (Bombyx mori L.) by leaf dip method. Results showed marked improvement of the silk percentage at low concentrations of 50-100 ppm. The use of appropriate PABA concentrations in commercial silkworm rearing is thus recommended.

Keywords : Bombyx mori L. Paraaminobenzoic acid (PABA). Leaf dip method. Silk yield.

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Breeding Season, Sexual Maturity and Fecundity of the Blue Crab, Portunus pelagicus (L.) in Selected Coastal Waters in Leyte and Vicinity, Philippines


Author(s): Corazon B. Batoy, Josephine F. Sarmago and Bernadita C. Pilapil

Abstract

Breeding activity of the blue crab Portunus pelagicus (L.) was found to be continuous all throughout the year with peak periods during the first and last quarters of the year. Fluctuations in gonad indices of males and females do not necessarily follow the same pattern because the female can store and keep viable mature spermatozoa in their spermatheca for a period of several months. This may facilitate the production of successive broofd without necessitating copulation for fertilization. The reproductive cycle of males peaks slightly earlier in the breeding season than that of females. Start of sexual maturity is indicated at a carapace length slightly below 40 mm and males seem to mature earlier than females. Fecundity ranges from 420, 976 to 1,312,238 with a mean of 894,284 for crabs 41-70 mm in length.
No significant correlations were observed between monthly gonad index and monthly means of temperature, dissolved oxygen and water transparency. However, salinity seemed to be one of the most important ecological factors affecting the species’ reproductive cycle with higher salinities being favorable for breeding.

Keywords : Blue crab (Portunus pelagicus L.) .Breeding. Sexual maturity. Gonad index. Fecundity.

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Incidence of Aflatoxin Contamination in Cassava (Manihot esculenta Crantz)


Author(s): Crisanta E. Sajise and Lina L. Ilag

Abstract

The incidence of aflatoxin contamination in cassava roots at different stages of maturity and during processing and storage was determined. No aflatoxin was obtained from 7- to 14- month old cassava roots. During storage, however, trace amounts of aflatoxin B1 were observed in stored cubes but not in stored chips and unprocessed roots. Blanching generally inhibited the growth of other fungi but not A. flavus. In the absence of competing fungi, fresh cassava roots may be a good substrate for the growth of A. flavus and A. parasiticus but not for aflatoxin production. A fluorescent compound behaving like aflatoxin B1 was observed in samples which were not dried after 48 hours as well as in unprocessed stored cassava roots showing vascular discoloration. Confirmatory test showed that it was not aflatoxin.

Keywords : Cassava (Manihot esculenta Crantz). Aflatoxin. Contamination. Aspergillus flavus. Blanching. Storage

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Contact Toxicity of Decamethrin and Permethrin on Black Bean Aphid and Two of Its Coccinellid Predators


Author(s): Erlinda A. Vasquez, Emiliana N. Bernardo and Ma. Flerida A. Carino

Abstract

The contact toxicity of decamethrin and permenthrin was evaluated on adult black bean aphids. (Aphis craccivora Koch) and third instar larvae and aults of its coccinellid predators. Chilomenes sexmaculata Fabr. and Coleophora inaequalis Fabr.
Based on LC50 , decamethrin is more toxic to the black bean aphid than permethrin particularly after 48 hours exposure. The third instar larvae of C. inaequalis exhibited than C. sexmaculata at 24 hours but not after 48 hours of exposure to decamethrin. However, the latter species was more tolerant to permethrin than the former as indicated by the lower LC50 obtained in C. inaequalis. The LC50 values of the two insecticides were consistently lower for adults of C. sexmaculata than C. inaequalis at both exposure periods.
The two insecticides used were more toxic to the aphids than to the coccinellid predators. Hence, they could be used to control aphids without adversely affecting the coccinellids which could also be utilized as biocontrol agents.

Keywords : Black bean aphid (Aphis craccivora Koch). Coccinellid predators. Chilomenes sexmaculata Fabr. Coleophora inaequalis Fabr. Fermethrin LC50

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