Date Published: July 19, 2018
Publisher: Public Library of Science
Author(s): Waqas Wakil, Muhammad Yasin, Mirza Abdul Qayyum, Muhammad Usman Ghazanfar, Abdullah M. Al-Sadi, Geoffrey O. Bedford, Yong Jung Kwon, Maohua Chen.
The red palm weevil Rhynchophorus ferrugineus (Olivier) is an important pest of date palms in many regions of the world. This paper reports the first survey of insecticide resistance in field populations of R. ferrugineus in Pakistan which were collected from seven date palm growing areas across Punjab and Khyber Pakhtunkhwa (KPK) provinces, Pakistan. The resistance was assessed by the diet incorporation method against the formulated commonly used chemical insecticides profenophos, imidacloprid, chlorpyrifos, cypermethrin, deltamethrin, spinosad, lambda-cyhalothrin and a fumigant phosphine. Elevated levels of resistance were recorded for cypermethrin, deltamethrin and phosphine after a long history of insecticide use in Pakistan. Resistance Ratios (RRs) were 63- to 79-fold for phosphine, 16- to 74-fold for cypermethrin, 13- to 58-fold for deltamethrin, 2.6- to 44-fold for profenophos, 3- to 24-fold for chlorpyrifos, 2- to 12-fold for lambda-cyhalothrin and 1- to 10-fold for spinosad compared to a susceptible control line. Resistant R. ferrugineus populations were mainly found in southern Punjab and to some extent in KPK. The populations from Bahawalpur, Vehari, Layyah and Dera Ghazi Khan were most resistant to chemical insecticides, while all populations exhibited high levels of resistance to phosphine. Of the eight agents tested, lower LC50 and LC90 values were recorded for spinosad and lambda-cyhalothrin. These results suggest that spinosad and lambda-cyhalothrin exhibit unique modes of action and given their better environmental profile, these two insecticides could be used in insecticide rotation or assist in phasing out the use of older insecticides. A changed pattern of both insecticides can be used sensibly be recommended without evidence of dose rates and frequencies used.
Red Palm Weevil Rhynchophorus ferrugineus (Olivier) (Coleoptera: Curculionidae) is one of the most damaging insect pests of almost all kind of palms worldwide [1, 2, 3]. The larval stages damage host plants, usually remain in the lower 1 m of the tree trunk and can complete several generations within the same host [4, 5, 6]. So far it is established in 50% of date growing and 15% of coconut producing countries . Early infestation cannot be detected and goes unnoticed. By the time the farmer recognizes the problem, the growing point (or cabbage) of the palm could have already been damaged with significant numbers of larvae developing inside the trunk generally resulting in the death of the palm [1, 7, 8,].
Knowledge of the resistance status of pests is important for researchers to guide the farming community in combating pest problems. It could become helpful for growers to reduce or suspend the use of particular chemicals in their plantings. These seven areas we worked on are the major date producing areas of Pakistan and contribute the major share of the country’s date production and have a history of R. ferrugineus infestation stretching back almost 100 years . To combat this pest, farmers have mainly used conventional insecticides and fumigants, particularly phosphine.