Field Screening of Promising Castor Cultures against Capsule Borer, Conogethes punctiferali s and Leafhopper, Empoasca flavescens

Studies were carried out on castor at Tapioca and Castor Research Station, Yethapur, Salem District, Tamil Nadu to find out the resistant sources against capsule borer and leafhoppers Among the eight entries screened, capsule damage ranged from 0 to 11.5 % in the primary spikes as against 35.7 % in the check TMVCH 1. The damage ranged from 0 to 10.8 % in the secondary spikes as against 26.7 % in the check. Maximum capsule damage was observed in RG 3089 (11.5 and 10.8 % in the primary and secondary spikes, respectively), followed by RG 2813, which recorded 5.4 and 6.2 % capsule damage in the primary and secondary spikes, respectively. RG 2770, RG 2776, RG 2778 and RG 2849 were completely free from capsule borer damage.

The castor shoot and capsule borer Conogethes punctiferalis G. is a serious pest of all India importance attacking castor from flowering stage onwards.The freshly hatched larvae feed on greenish coat of the capsule and enter the capsule by boring at the pedicellar or stigmatic end.Castor beans are bored through caruncle.At the site of entry, a silken gallery is made in which excreta and frass are accumulated.As the damage advances, a characteristic webbing of capsules along with excreta and frass is seen.When inflorescence is attacked at the time of emergence, it withers and dries away and the terminal shoot also gets killed.Though the borer can bore in to the tender shoots, it has preference for capsules.
Plant morphological characters are involved in imparting resistance against leafhoppers and capsule borer (Jayaraj, 1968).Hence, the present study was undertaken to screen the resistant sources in castor against capsule borer and leafhopper.

Materials and Methods
Germplasm accessions of castor were screened against leafhoppers and capsule borer with TMVCH 1 as check during kharif 2006 with eight promising entries viz., RG 2770, RG 2776, RG 2778, RG 2786, RG 2813, RG 2820, RG 2849 and RG 3089.Each accession was sown in a single row of 5 m length with the spacing of 90 x 60 cm and replicated thrice.Single row of susceptible / local check TMVCH 1 was grown on both the sides of test entries in sandwich method.
Leaf hopper numbers were recorded from three leaves per plant on ten randomly selected plants in each entry where each plant was considered as a replicate.The leaves were selected as one from top (excluding two top most leaves), middle (medium matured leaves) and bottom (leaving two bottom most leaves) on the main shoot.The percentage leaf area burnt (hopper burn injury) was also recorded in 0-5 scale.
Capsule borer damage, was recorded both in the primary and secondary spikes and expressed as damage per plant.Data were subjected to statistical analysis (Panse and Sukhatme, 1978).

Results and Discussion
Capsule damage was in the range of 0 to 11.5 per cent in the primary spikes as against 35.7 per cent in the check TMVCH 1(Table 1).While, the damage was in the range of 0 to 10.8 per cent in the secondary spikes, as against 26.7 per cent in the check TMVCH 1. Maximum capsule damage was observed in RG 3089 (11.5 and 10.8 % in the primary and secondary spikes, respectively), followed by RG 2820, which recorded 8.9 and 9.4% capsule damage in the primary and secondary spikes, respectively.These two entries (RG 3089 and RG 2820) were with double and zero bloom, respectively and the capsules in the spike were compact and spiny, that favoured infestation by capsule borer.RG 2770, RG 2776, RG 2778 and RG 2849 were completely free from capsule borer damage (0 per cent in both the primary and secondary spikes) RG 2786 and RG 2813 recorded less than 5 per cent capsule damage.
RG3089 recorded the maximum number of leafhoppers (89 per plant) and maximum hopper burn injury grade of 2.0, followed by RG 2849 (31.7 per plant), RG 3089 (29 per plant) and RG 2778 (23.7 per plant).Entries with triple bloom viz., RG 2770, RG 2776, RG 2786 recorded minimum number of leafhoppers per plant (9, 10.3 and 9 per plant, respectively) with the lowest hopper burn injury grade of 0.3 (Table 1).
The results obtained by Dorairaj et al. (1963) indicated triple bloom varieties of castor to be more resistant to jassid, compared to no bloom and single bloom varieties.The preferred varieties in general had broader leaves, since they afford more protection and shelter to jassid from hot conditions.Jayaraj (1967) also proved that the antibiosis component of resistance in certain castor varieties affected significantly the biology of the insect.
Castor varieties with double and triple blooms were more susceptible to whiteflies (David and Radha, 1964) and mites (Chandrasekharan et al., 1964).and the castor varieties which were resistant to jassids are susceptible to whiteflies and vice versa.

Table 1 . Screening of germplasm entries of castor against capsule borer and leafhoppers (Kharif '06)
*Mean of observations from 10 randomly selected plants.