MSc

A survey conducted in Kottayam and Idukki Districts (ginger tracts) of Kerala, adopting multistage random sampling technique, revealed that D. punctiferalis is the major pest infesting the crop in both the Districts. The first instar larvae bored in at the fourth or fifth leaf axil of the psuedostem and caused the drying up of the distal part. Then the larvae emerged out and tunneled in at the base of the psuedostem. The lower part of the stem did not dry up. The pest had a uniform distribution in the two Districts. The extent of shoot damage ranged between 23.59 and 24.92 per cent. The incidence of the pest was not significantly associated with the soil type in which the crop was grown or with the age of the crop. The damage observed was higher during August, September and October and started declining from November. The possible yield loss for the mean damage of 23 to 24 per cent of the psuedostem could be estimated as 25 per cent based on the observations of CPCRI (1981 a).
A field experiment conducted in the two Districts showed that the avoidable yield loss caused by D. punctiferalis was around 40 per cent. Application of granules (carbofuran and phorate) caused initial reduction in the damage done by D. punctiferalis but it did not persist to reduce the final yield loss caused by the pest. Need based spraying of dimethoate or quinalphos 0.05 per cent emulsion controlled the pest effectively. Spraying of quinalphos was more economical.
Studies on the nature of damage done by the rhizome maggot M. coeruleifrons revealed that the entry of the maggot in to the rhizome occurred only when there were mechanical injury at the collar region or the tissues at the point was softened by prior infection of bacteria or fungi. A pot culture study showed that the fly maggots invaded the rhizome infected by fungus and not vice versa. The fly was seen distributed in both the Districts, but the distribution was discontinuous. The incidence in the high ranges was very low. The incidence of the pest was positively correlated with the rhizome rot disease incidence. The biology of the pest was studied in detail and the life stages of the pest have been described in detail.
The leaf roller U. folus was observed as a minor pest of ginger and it was distributed in a few locations covered in the survey.
The leaf spot disease was prevalent in Idukki and Kottayam Districts the mean indices of the disease being 1.627 and 1.043 respectively. The disease commenced in July, reached the peak in September and continued up to November.
Soft rot disease was prevalent in Idukki and Kottayam Districts; but the distribution was discontinuous. It was less in higher elevations of Idukki District. The peak incidence of the disease was in September. It was less common in forest lands. the relative humidity was positively correlated with disease incidence while the age of the crop had a negative influence.
Meloidogyne sp and Radopholus sp were obtained from the root and soil samples collected from the different locations covered in the survey. But population was too low to cause significant crop loss. Low population of Helicotylenchus sp. in root and soil samples and Criconema sp, Xiphinema sp and Mononchus sp in soil samples were also recorded.