Management of the Mediterranean fruit fly (Ceratitis Capitata Wied.) Using Pheromone Traps and Neem Seed Extract

Abstract

Laboratory and field experiments were conducted to evaluate the effectiveness of neem seed water extracts (NSWE) and pheromone traps to control the Mediterranean fruit fly, C capitata infesting citrus at the University of Ghana Agricultural Research Station (ARS), Kade. Neem seed extract of concentration 15%, 20%, 25% and 30% wt/vol were prepared and left overnight after which the suspensions were seived and used for spraying. Ripened fruits of Citrus sinensis cultivar Late Valencia and Citrus unshiu cultivar Satsuma were harvested into insect cages containing adult C. capitata after which they were sprayed with the neem seed water extract (NSWE) suspensions Second and third instar larvae and pupae were removed from untreated rotten fruits into petri dishes. These were exposed to the various suspensions as indicated above. Field experiments were conducted concurrently with the laboratory experiment to determine the seasonal abundance and activity pattern of C. capitata using pheromone traps baited with med-call, a Japanese formulated pheromone. To monitor the seasonal abundance of C. capitata two rectangular traps each baited with trimedlure (TML) were installed in Satsuma and Late Valencia citrus orchards. Data were collected every other day between 8:00 - 10:00 am. from September, 1997 to July, 1998. A similar method was used to investigate the diurnal activity and behaviour of C. capitata from 6:00 am. - 6:00 pm. To test the effectiveness of the NSWE under field conditions, field experiment were conducted in two selected citrus orchards i.e. Late Valencia and Satsuma. The two fields were each laid under the Randomised Complete Block Design (RCBD). NSWE of 25kg/ha suspension was sprayed on the trees. Two controls of picking of dropped infested fruits and no picking of dropped infested fruits were included. Dimethoate 40EC was also used as the basis for comparing the performance of the NSWE suspension. Results from laboratory work showed that oviposition of the adult female was significantly reduced when 20%, 25%, and 30% wt/vol NSWE were sprayed on each citrus variety. The anti-ovipositional effect of NSWE was dosage-dependent. The number of oviposition punctures on Late Valencia were significantly fewer than on Satsuma. The development period from eggs to adult in fruits sprayed with the NSWE suspensions was found to be between 38 - 40 days which was not significantly different among the citrus species examined. 25% and 30% wt/vol. of NSWE were more effective against the larvae removed from fruits. About 79% of 2nd instar larvae died when exposed to 25% and 30% NSWE suspensions. The percent mortalities were 73% and 84% for 25% and 30%wt/vol NSWE respectively when 3rd instar larvae were exposed. Furthermore, the development of pupae into adult was delayed by 6 — 9 days. There was significant difference among the treatments when pupae were sprayed together with soil. However there was no significant difference on the mortality of the pupae when only the soil was sprayed with the NSWE before introducing the untreated pupae. The results from the seasonal abundance and diurnal activity pattern using the pheromone traps indicated that, the population of C capitata was high during the period of fruit maturation (colour break) and continued till harvesting. The peak periods in Satsuma occurred in September 1997(38.5) and March 1998 (68.5) whereas that of Late Valencia occurred in December 1997 (36.5) and March 1998 (29.5) which are the harvesting periods for Satsuma and Late Valencia respectively. The diurnal activity of C. capitata was higher during 8:00- 10:00 am. than 3:00-5:00 pm . The mean number of 9.1 and 10.0 per trap were recorded between 8:00-10:00 am. for Late Valencia and Satsuma orchards respectively. The value for 3:00-5:00 pm. were 4.4 and S.l for Late Valencia and Satsuma respectively. The management practices adopted in the field to determine the effectiveness of NSWE under field conditions showed that C. capitata caused as high as 46% and 32% damage to Satsuma and Late Valencia citrus fruits respectively if not controlled. Damage was high in Trimedlure + picking of dropped infested fruits (TML+P) (46%) treated plots. The neem seed water extract and picking of dropped infested fruits (NSWE+P) treated plants performed significantly better than Control + no picking of infested dropped fruits (CNP), control + picking of infested dropped fruits (CP) and TML+P. Percentage damage recorded in the NSWE+P treated plots was however, significantly higher than the Dimethoate 40 EC and picking of dropped infested fruits (Dim+P) treated plots. Dim+P reduced fruits damage by more than half compared with the trimedlure and the control plots Dim+P and NSWE+P reduced the population of C. capitata by 27% and 10% the Satsuma orchards respectively. Similarly the C. capitata population was reduced by 24% and 14% by Dim+P in the Late Valencia orchard respectively. The NSWE sprayed at 25 kg/ha was comparatively better than the control treated plants. The cost-benefit analysis showed that the cost of spraying the NSWE could be beneficial particularly in the Satsuma orchard. This was however, not the case in the Late Valencia orchard. The relationship between adult C. capitata captured in TML baited traps, the number of damaged fruits, the number of larvae and pupae from damage fruits and the number of oviposition holes on fruits showed significant correlation.