Purnima Das

In vitro compatibility of entomopathogenic fungi, Beauveria bassiana (Bals.-Criv.) Vuill. with leaf extracts of Chromolaena odorata (Asteraceae)

The compatibility of Beauveria bassiana (Bals.-Criv.) Vuill. with Chromolaena odorata (L.) King & H. Rob. (Asteraceae) was evaluated in vitro. Aqueous and solvent extracts of leaves of C. odorata at concentrations of 0.1, 0.5 and 1% were evaluated on the growth, conidial density and germination of B. bassiana by using the poisoned food technique. The extracts exhibited varying effects on growth of the fungus ranging from toxicity to inhibitory action, which increased with increase in the concentrations. The reduction percentage of radial growth of B. bassiana over control was found to be significantly less with the aqueous extracts of C. odorata. Inhibitory action was found to be highest (96.93%) with the chloroform extracts at 1% concentration. Similarly, as the concentrations increased from 0.1 to 1%, there was a significant reduction in the conidial density and germination in all the test concentrations. Based on the findings, the order of compatibility based on percentage reduction of radial growth is as follows: water > petroleum ether > methanol > acetone > chloroform. Hence, the aqueous extracts of C. odorata at 0.1% concentration can be integrated along with B. bassiana in any biointensive pest management programme.

Study on duration of instars and morphomatrics of Corcyra cephalonica (Stainton)

Developmental durations as well as morphometrics of Corcyra cephalonica larvae were carried out in the Physiology Laboratory, Department of Entomology, Assam Agricultural University, Jorhat during 2014–15. There were six larval instars of C. cephalonica, the mean body length and breadth of 1st, 2nd, 3rd, 4th, 5th and 6th instars larvae were found to be 0.63, 2.26, 3.23, 5.03, 13.0, 15.6 and 0.26, 0.53, 1.00, 1.46, 2.73, 3.1 mm, respectively, while the mean larval duration was 1.66, 2.66, 4.26, 5.33, 6.00 and 7.66 days computing entire larval development in 27.57 days.

Occurrence of Aphis craccivora on Clerodendrum indicum-A new record from north-east India

Clerodendrum indicum (L.) Kuntze, a medicinal shrub, is gaining worldwide recognition and importance because of its outstanding property as anti HIV-I agent. Studies on seasonal incidence of A. craccivora Koch, an important polyphagous pest, were carried out on C. indicum under field conditions during 2012–14 at Jorhat, Assam. The peak population was recorded during the month of November 2012 followed by December 2012. Similar trend of occurrence was also observed during 2013–14. Multiple regression modelwas developed for A. craccivora Koch to predict their seasonal incidences under the agro-climatic conditions of Jorhat.