V.M. Bhan’s scientific contributions

Study was done on spread and establishment of Mexican beetle Zygogramma bicolorata in Vindhya Nagar locality of District Sidhi of state Madhya Pradesh, India where the bioagent was released in 1991. It was found that beetle did not show visible impact during initial three year after release, however by 4th year, there was wide establishment and spread of the bioagent. Spread of beetle was recorded up to 28 km from the release point within a period of 5 years. Mexican beetle establishment and spread was discussed in the light of weather parameters in the area. Excellent establishment of bioagent was found even in fluctuation of low and high temperature.

Effect of defoliation by Mexican beetle Zygogramma bicolorata was studied on sugars and phenols of Parthenium and different varieties of sunflower. Parthenium emerged most preferred host of beetle. In case of whole plant damage total phenols decreased steadily.

Survey revealed the dominance of Cassia tore in the places earlier dominated by Parthenium. Lab studies confirmed the effect of leachates of seed of Cassia tora on grmination of Parthenium.

The spread of alligator weed Alternanthera philoxeroides has been observed at the alarming rate in and around the city of Jabalpur (Madhya Pradesh) especially in the ponds earlier badly infested with water hyacinth. This weed was also observed to be rapidly spread in the terrestrial area of the low land where water was inundated during rains. Fast spread of this weed is especially important in India where its current distribution and spread is only a fraction of its potential distribution. This alarming spread at Jabalpur has necessitated the prompt control of this weed.

Phalaris minor has assumed the status of a major weed in wheat crop in northern India. The problem was further aggravated due to occurrance of resistance in the weed to the herbicide "isoproturon" used to control it effectively. In order to know the reasons of high incidence of P. minor in rice-wheat cropping system, the study of the the basic mechanisms of the success of this weed was undertaken. Efflux of phenols and phenolics from seeds were presumed to play important roles in the germination of the weed. Analysis of total phenol (TP) content of seeds kept under various moisture regimes showed that maximum leaching out of TP was 7.39% when kept under field capacity whereas maximum leaching out in saturated moisture condition was 11.82% with respect to field capacity in 40 days. Mobilization of TP from seeds increased steadily with corresponding increase in depth of submergence and time (57.95% under 5 cm submergence and 63.57 % under 10 cm submergence). This paper discusses the effect of efflux of phenols and phenolics on self germination of P. minor seeds and through the light on the role of phenolics in the rice-wheat cropping system.

Host preference of mexican beetle Zygogramma bicolorete, a biocontrol agent of parthcnium W<lS studied using biochemical pararnctcrs. The amount of protein, DNA, RNA, free amino acids and body weight were recorded higher in parthenium fed grubs than xanthium.

Paper deals with the controversy over feeding of sunflower by the host specific bioagent Zygogramma bicolorata in India. A Fact Finding Committee (FFC) was constituted by Indian Council of Agricultural Research under the chairmanship of Dr. V.M. Bhan to find the facts. FFC first , Second and third meetings were held on 21 November 1992, 19-20 October 1993 and 5-6 September 1994, respectively. FFC found a few instances of grubs feeding on sunflower in Karnataka. FFC was of the view that bioagnt species in Z. bicolorata instead of A. conjuncta as proposed by some of the scientists and published in journal 'Current Science' volume 65, No. 12 in 1984. FFC recommended to continue the ban on intentional release of Z. bicolorata in India till further findings.