DEMOGRAPHY, BIO-ECOLOGY AND INTEGRATED MANAGEMENT OF RED PALM WEEVIL, RHYNCHOPHORUS FERRUGINEUS (OLIVIER) (COLEOPTERA: CURCULIONIDAE) IN PAKISTAN

Abstract

The date palm (Phoenix dactylifera L.) is known for its multifacid properties sustaining human life in most of the Asian countries. The date palms in Arabian and Asian countries have been severely infested by a serious pest known as Red Palm Weevil (RPW) (Rhynchophorus ferrugeneus) Olivier (Coleoptera: Curculionidae: Rhynchophorinae) for the last three decades. In the present study, a survey was conducted in heavily infested areas of Pakistan. Our results show that RPW population increased in the months of March, April, May and June. There was a positive correlation between the RPW and temperature during 2014. However, relative humidity (RH) had an adverse impact on the RPW population. Maximum percent infestation was observed in Sindh (24.22%) and minimum in Baluchistan (8.16%). In an olfactometer based behavioral response study of the RPW, least antixenotic effect was displayed by a cultivar named as “Hillawi” with maximum attraction of R. ferrugineus adults (23.65±5%) while “Aseel” showed high antixenotic effect with maximum weevil’s attraction (13±3%). A perceptible general reduction in the different biochemical features and development has been observed under biotic pressure in all plants. In order to investigate the defense response in R. ferrugineus infested date palms, some common physiological indexes were determined. Level of antioxidants such as proline, MDA, ascorbic acid, catalase, peroxidase and soluble sugars increased in Hillawi & Aseel (12.03 & 9.4 μmole/g, 17.66 & 13.83 μmole/g, 7.06 & 6.06 μmole/liter, 0.756 & 0.663 μmole/mint/mg protein, 0.25 & 0.18 μmole/mint/gf wt and 60.33 & 50.01 μmole/mint/gf wt) upon infestation by R. ferrugineus. We also conducted DNA barcoding of R. ferrugineus and our sequencing results indictate no significant difference in the RPW weevils collected and phylogeny trees constructed by CO1 and ITS revealed that all the weevils tested showed not significant genetic variations with a similarity index of 99-100% with already reported from KSA (Mecca & Najran) and UAE. About 92% and 97% similarity with R. bilineatus and R. vulneratus respectively was observed. For the control of R. ferrugineus, we used different two nematode strains (S. carpocapsae and H. bacteriophora) and one fungus (B. bassiana), resulted a tremendous increase in the larval, prepupal and pupal duration of RPW. However, adult life span and weight were deceased. Diet consumption and frass production were also reduced with the combined applications of EPN and EPF. We have studied the level of insecticide resistance against cypermethrin caused by P450 genes in population of RPW collected from various regions of Pakistan. Results indicate that resistance level in the R. ferrugineus population was significantly different in the different laboratory populations (7.32, 4.30, 15.51 and 1.98 in FP, FK, FS and FB respectively) upon the knockdown of P450 gene with resistance level up to 178.5 folds in the LR (G6) by using dsRNA applications. The gene expression was further verified by checking the protein expression through western blotting. RNAi based silencing of CYP450 proved as a successful management tool against RPW.