Population dynamics, biology and management of Amrasca splendens Ghauri

Abstract

The present investigations were made during 2003-04 on the different aspect of Amrasca splendens Ghauri at IIHR namely, seasonal incidence, biology, extent of damage, management of A .splendens and response of leaf hopper to Alphonso, Banganapalli and Totapuri varieties, All the aspects were summarized below. Seasonal incidence of A. splendens indicated that three population peaks were observed, with the second peak was observed during third week of April (23.20 mean leafhoppers per shoot). The first peak during third week of June (11.05 mean leafhoppers per shoot) and third peak was during last week of November (0.29 mean leafhoppers per shoot). Incidence of A. splendens was found on all the commercial varieties studied namely, Alphonso, Banganapalli and Totapuri from May 2005. On these varieties the incidence gradually increased from February to March and reached its peak during April, from then the population started declining and reached a minimum during July to October, July to March and May to January, in Banganapalli, Totapuri and Alphonso, respectively. The Incidence of A. splendens had showed positive significant correlation with maximum temperature(r=0.38) minimum temp. (r=0.36) and flushing(r= 0.67). Tender leaves were found to have positive effect. Further, the studied showed that co-occurrence of factors like maximum temperature at third week prior to leafhopper incidence and flushing at one week prior to leafhopper incidence explained the leafhopper density up to 65 per cent. Relative humidity and wind speed were not found to have any effect. Studies on the biology of A.splendens on mango were conducted under laboratory conditions, during April 2004. Previposition, oviposition, and post oviposition periods lasted for 8 to 10, 10 to 12 and 4 to 6 days, respectively. The total fecundity based a nymphal emergence ranged from 15 to 26 eggs per female. Eggs were slightly oval and transparent and were laid in the midrib, vienlets and occasionally in leaf lamina. Oviposition per days varied from 1 to 4 during peak season for per female. It took 4 to 5 days for hatching. The nymphs passed through five instars and they lasted for 0.69, 1.25, 1.94 and 2.63 days, respectively. During the course of the study three predators namely Isyndus heros Fab. And Mantis religiosa Lab., were found attacking the different stages of the leafhopper. However these were of no major consequence. The female adults caused the major damage by ovipositing in midrib towards anterior region of tender leaf, which resulted in blockage of phloem tube due to which, drying of leaf apex backward was observed. However in majority of damaged leaves the dried tip just break off leaving a typical “tip cut” symptom. After emergence nymphs cluster on the lower side of the tender leaves and suck sap from midrib and vienlets. Under server infestations, the leaves of sprouting shoots withered and ultimately fell down. The oviposition in the midrib caused anatomical changes in the leaf midrib and as well as in lateral veins of the leaves. The healthy midrib stained in toluidine blue mercuric bromophenol blue and periodic acid Schiff’s reagent has indicated the presence of vascular bundles and other related structures, where as in infested tissue the staining was either blank or very lightly indicated the degeneration of tissue or the presence of chitinaceous materials in the midrib (left out material of chorion). Further, it could be clearly seen that there was an opening in the midrib to indicate the escape of nuymphs by rupturing midrib. Studies were conducted on the management of A.splendens during April 2005. The botanicals namely viz., Pongamia soap 10 g/l, Neem soap 10 g/l, Neemazal 1.5ml/l, Neemark+ 1.5ml/l, Neem oil 10ml/l, NSKE 4% were used for the study. Endosulfan 2ml/l was used to compare the efficacy of botanicals. The results showed that neem oil 10ml/l and NSKE 4% giving 100 per cent control of the leafhoppers.