IPM OF RED PALM WEEVIL اإلدارة المتكاملة لسوسة النخيل الحمراء Editors P.S.P.V. Vidyasagar Saleh A. Aldosari February 2011
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Acknowledgements We express our sincere thanks to Prof. Dr. Abdullah A. Al- Othman, President and Prof. Dr. Ali AlGhamdi, Vice President of KSU for their encouragement and support. Also we express our thanks to the Dean of our College Prof. Dr. Hassan AlQahtani and the Head of Plant Protection Department Dr. Mohammed AlSaleh for their active support in chair s activities. The cooperation and help received from Head Quarters and various branches of the Ministry of Agriculture are gratefully acknowledged. Finally we thank Mr. Samy Mostafa Ibrahim and Dr. Paraj Shukla of our research chair for their help in this publication. 3
1. Introduction IPM OF RED PALM WEEVIL Rhynchophorus ferrugineus Red Palm Weevil Rhynchophorus ferrugineus Olivier (RPW) is a serious pest of date palm and causes severe losses to farmers. It belongs to Curculionidae family under the order Coleoptera (beetles & weevils). It is a hidden pest and remains inside the palm during the larval development and makes tunnels and pupates. The adults either emerge outside the stem or remain inside the hollow, damaged stem and continue to breed and thus create multiple broods or overlapping generations. Though external symptoms of attack by RPW are sometimes manifest early, but more often by the time the damage symptoms are identified, the palm is damaged beyond recovery and has to be eliminated or destroyed. The female weevil after mating deposits eggs into soft tissues of the palm or any fresh wounds caused mechanically. In its life-cycle a female may lay about 200 to 260 eggs. The eggs hatch in 3 to 5 days into larvae which tunnel into stem and remain hidden inside the trunk. The larvae will grow up to 5 cm and reach pre-pupal stage after several instars in about 60 to 90 days. Pupation occurs in a cocoon spun with chewed fibers and lasts for about 20 days. The adult on emergence may remain inside the stem or may disperse and spread the infestations to other palms. The life stages of RPW are given in Figs. 1a - 1e. Fig. 1a: Adult weevil Fig. 1b: Eggs 4
Fig. 1c: Larva Fig. 1d: Pupa (without cocoon) Fig. 1e: Cocoon showing the pupa The male and female weevils can be distinguished based on a smooth hairless rostrum in female (Fig. 2) while in males the dorsal surface of rostrum has a tuft of hairs (Fig. 3). Fig. 2: Adult female weevil Fig. 3: Adult male weevil 2. Judicious Integration of Methods Generally for the successful control of an economically important pest like RPW it is mandatory to judiciously mix various methods of control such as cultural control, chemical control, mass pheromone trapping, biological 5
control, mechanical control, quarantine control etc. Before launching any pest control program the quantitative relationship between yield losses and pest population levels are estimated to compute the economic injury level for the pest. Sometimes it is not possible to directly assess the crop losses and one depends on other factors like the percentage of infestation and population levels to implement the control methods. Hence, combined use of all the available control methods in a rational way is the basis for formulation of Integrated Pest Management control strategies. 3. Survey & Surveillance (Scouting) An important item in the plant protection is regular survey and surveillance of all palms in a garden at regular intervals. Visual observations should be made on mother palms as well as offshoots. It is necessary to check or inspect each palm once in a month from base to the crown. Also skewer or a thin metal rod of about a meter length may be used as a probe to insert into the soft tissues of the palms and check for any bore holes made by the pest (Figs. 4 and 5). Fig. 4: Metal probe / screw driver (50 to 60 cm) used for inspection Fig. 5: Inspecting a palm with a metal probe for any infestations 4. Identification of Early Symptoms of Damage Generally when a palm is in early stages of infestation a brown viscous liquid oozes out of the site of damage. This liquid solidifies upon exposure to air and some brown flakes can be seen (Fig.6). Another symptom is the 6
presence of bore holes with chewed up fibres and when these lumps of fibers are examined they give out a very foul smell characteristic of RPW damage alone (Fig. 7). This is a real confirmation of the presence of fresh damage inside the palm. Some times when the small external holes are cleaned further cavities are observed with several insect stages. This kind of infestation may be extending up to 12 deep inside the stem. In date palm infestations occur mostly at the basal part of the stem or within three feet from the ground. However, a few infestations may occur in the crown region as well due to some mechanical injury and such damage could be devastating and cause the toppling of the crown and immediate death of the palm. From such palms a large number of insects emerge and disperse to other vulnerable palms and cause fresh infestations especially in the nearby palms. In extreme cases when a wound in a palm stem is cleaned, there may be a large cavity harboring several hundreds of eggs, larvae, pupae and adults. Some reports claim the removal of more than 300 different stages of RPW form a single palm alone suggesting the severity of infestation. Such palms are beyond recovery and have to be removed and disposed properly to avoid dispersal of insect stages. Fig. 6: Oozing of brown viscous fluid from the stem indicating RPW infestation Fig. 7: Chewed up fibers with an adult weevil near the bore hole on the stem 5. Decision Making about Treatment After identifying an infested palm it is time for making a decision about its treatment. As described above under symptom and damage, it may be 7
classified in to three categories for treatment. If the infestation is in the early stages the chances of recovery are fairly high and most likely the palm will become normal. Various methods of treating such palms are given below. Most critical decision to make is about the palms with a cavity caused by the feeding of RPW larvae. This is where extension workers have to be careful and use their experience to categorize the palm as recoverable or not. If the infestation is severe, there is no cure and such palms should be removed carefully and treated to kill all the living stages of the pest residing inside. More details about this are given under mechanical methods. For convenience the early, medium and severe infestations may be classified as category I, II and III infestation respectively (Figs. 8 13). Fig. 8: Palm showing early to medium infestation Fig. 9: Palm showing medium infestation at the bole region 8 Fig. 10a: Young palm showing infestation at the base Fig. 10b: Young palm shown in Fig. 10a when removed showing deep hollow cavity full of RPW stages
Fig. 11: Badly infested palm due for removal Fig. 12: Young palm after scooping out the damaged tissues Fig. 13: Toppled crown caused due to severe damage by RPW 6. Chemical control The most effective method of controlling RPW is the use of insecticides at the recommended dose. The list of effective and recommended pesticides should be obtained from Agriculture Ministry officials. There are two methods of chemical control. 1. Preventive methods and 2. Curative methods. 6.1 Preventive methods As a preventive method the palm trees are sprayed regularly with a recommended pesticide. Under this method the palms are treated with insecticide to prevent the entry of RPW in to the plant tissues. For covering more area in a day, motorized high pressure sprayers are employed to spray 9
all parts of palms. Though the method of spraying with high performance prayers may give good coverage superficially, it does not penetrate the fibers of the crown and crevices of stem uniformly leaving the hidden weevils unaffected (Fig. 14). However, a new method of soaking or drenching the palm crowns was developed to facilitate the insecticide to reach deeper. Hence, it was recommended to use a long lance of about 2.5-3.0m with low pressure to soak the crowns as well as the bole region of palm. When pesticide is applied slowly to the central leaf whorl, it soaks all the fibers in the crown and percolates down to stem (Fig. 15). This method was found to be quite effective in killing the hidden insects and also reduces the chances of pollution, spillage of pesticide, and air contamination. The preventive soaking or spraying has to be given with the recommended pesticide once in every 3-4 months. While choosing the insecticide, it is advisable to avoid the repetition of the same chemical to prevent the development of insect resistance in long run. Fig. 14: High-pressure spraying of insecticide as a preventive method Fig. 15: Low-pressure soaking of crown and stem with a insecticide using a long lance 6.2 Curative methods When an infestation is identified, the first thing to do is to examine the site carefully and decide about treatment. It is recommended to give a stem injection in a very systematic manner to completely eliminate all stages of the pest hidden inside the stem. 10
6.2.1 Stem Injection Chair of Date Palm Research - IPM of Red Palm Weevil The damaged site is cleaned slightly to trace the spread and intensity of infestation. After this 6-8 deep holes of 1 diameter are drilled by an electric driller a few inches all around the place of damage. About 6-10 holes are made depending on the intensity and depth of attack. Working solution of recommended pesticide is poured in to these holes and the plant absorbs it in about 24 h. All trees administered with stem injection are monitored at weekly intervals to see the effectiveness and complete cure. Generally the symptoms of cure are dried up wounds, stopping of brown liquid ooze, stopping of fresh chewed fibers, and other characters. The stem injection plays a very significant role in the management of RPW in Saudi Arabia (Figs. 16 19). Fig. 16: Making holes in the palm stem with electric drill for injecting pesticide Fig. 17: Using battery-operated drill to make holes for administering pesticide 11
Fig. 18: Pouring pesticide into the drilled holes with a hand sprayer Fig. 19: Application of pesticide into the drilled holes through an injector 6.2.2 Surface Application of insecticide Some times the infestation is detected in the early stages and it is very superficial on the surface. This type of infestation is first cleaned till the fresh stem tissue is exposed (Fig. 20). 12
Fig. 20: Palm showing the scar after removal of offshoot Then insecticide solution or paste is applied to the surface to prevent entry of RPW. This method is very useful if the damage is noticed in the early stage (Fig. 21). 7. Pheromone Trapping Fig. 21: Scar on the palm (Fig. 20) dusted with pesticide One of the most important components of IPM is the mass trapping of RPW with pheromone (ferrolure) lure + food baited traps. The Saudi trap consists of a 5L bucket with jute covering or date palm fiber and four windows of approximate 2.5 x 5 cm on 4 sides just below the rim. Pheromone lure (Ferrolure +) sachet containing 700 ml of 4-methyl-5-nonanol + 4-methyl -5-nonanone (ratio 9:1) is tied to the bucket cover from inside along with ethyl acetate dispenser. About 100 g of date fruits serve as food bait with 1 or 2 L of water to which a suitable pesticide is added. Adding yeast to the food solution will enhance the fermentation process and improve the trap 13
catches. This Saudi trap is strapped to the clean dry stem at a height of 1.2m from ground (Fig. 22). The number of traps depends on the size of a farm. Weekly or biweekly servicing of traps is undertaken during summer and winter respectively to replace food and water and pesticide. Pheromone lure may last for about 10 weeks in winter and 4 weeks only in summer due to high temperatures prevailing in the Kingdom. There is another trap design which is proving to be quite encouraging with good catch of weevils. In this a date palm stem from eradicated palms is cut in to a stump of 50 cm height with a hole of approximately 15 cm deep and 22 cm in diameter in the middle to nestle the Saudi bucket trap (Fig. 23). It has to be ensured that the four windows on the bucket trap are just above the stump. Also the space between the bucket and stump hole should be covered with mud to prevent the entry of insects in to these crevices. Perhaps the architecture and rough surface may provide better grip for the alighting weevils and result in better catches (Fig. 24). While using pheromone traps it is necessary to take certain precautions like regular servicing, timely replacement of exhausted lures and placement of trap. Palms around the pheromone stations should be checked regularly for any potential infestations and whenever any infestation is noticed it must be treated immediately. By mass trapping fairly large number of adult weevils of females and males are attracted and killed thus reducing the population in the vicinity of the farms. The ratio of males to females captured in traps is reported to be about 1:1.3. 14 Fig. 22: Saudi Pheromone trap on a clean dry date palm stem
Fig. 23: Saudi trap embedded in a palm stump Fig. 24: Saudi trap in Fig. 23 opened to show pheromone lure sachet, ethyl acetate in a vial attached to the cover and date fruits in water with pesticide. A few trapped weevils are also seen. 8. Light Traps : Although RPW adults are not attracted to light traps, other date palm pests viz., fruit stalk borer Oryctes spp. and stem borer Jebusaea hammerschmidti are attracted. The mechanical damage caused by these pests provides entry points for the RPW to attack the date palm. Hence, many farmers install several light traps in their gardens to reduce the population of these insects (Fig. 25). Fig. 25: Light trap 15
9. Cultivation Practices The farming practices adopted by the grower play an important role in the health of the palms and also the infestation levels. A few points of good agricultural practices are described that will have a bearing on the overall impact of RPW. Most of the farms are irrigated either by flood or drip system. A basin around the stem has to be made with earth up at the bole region to prevent the direct contact of water when irrigated (Fig.26). This measure will avoid soaking and softening of stem tissues in water which otherwise will be ideal for egg-laying by RPW as in flood irrigation (Fig. 27). Fig. 26: Date palm basin with drip irrigation Fig. 27: A farm with flood irrigation system 16
Another important step is the cleaning and pruning of palms and their offshoots. By this operation any potential sources of infestation are removed and destroyed making the farm clean. It is necessary to do this task as and when needed or on a scheduled basis (Figs. 28 30). Fig. 28: Pruning of leaves in progress Fig. 29: Climbers cutting the bases of leaves Fig. 30: Garden shown in Figs. 28 and 29 after cleaning 17
10. Mechanical Methods When severely damaged and dead palms are noticed it is necessary to remove them and dispose of properly. For this purpose, palms should be cut in to smaller bits and treated with pesticide and then burned (Figs. 31 and 32). Sometimes farms are neglected or abandoned by the growers for several years. Such farms harbor many infested palms and the best way is to completely eradicate the palms by mechanical removal and destruction of palm stems. Heavy machinery like bulldozers, loader, etc are used for quick removal of palms in those gardens (Fig. 33). Palms removed in large scale are transported to a dumping area and burnt completely to kill any residual populations of the weevil. In recent years a heavy duty shredder of palm stems is available which smithereens the stems in quick time and turns them in to a kind of date peat (Fig. 34). Fig. 31: Cutting a severely damaged palm for burning Fig. 32: Burning of palm refuge after cleaning Fig. 33: Removal and disposal of damaged palms from a neglected garden Fig. 34: Heavy-duty palm shredder in operation 18
11. Management of Offshoots In date palm cultivation offshoots are highly valued as planting material and fetch high returns for farmers. This is true with the most popular and sought after cultivars in each region. Hence, special attention is needed to manage the offshoots. Some legislation is in position regarding the movement and transport of offshoots from one region to another and all should follow them. When an offshoot is removed from the mother palm, the fresh and exposed tissue on the stem should be treated with a pesticide so as to prevent egg-laying by RPW. After removal the offshoots should be dipped in a pesticide solution for about 10-15 min to kill any adults hidden in the fibers. For transportation of offshoots from one region to another region or within a region, it is mandatory to follow the quarantine laws and legislation announced from time to time by the Ministry of Agriculture (Figs. 35 and 36). Fig. 35: Pesticide bucket and freshly removed offshoot Fig. 36: Offshoot dipped in a pesticide solution 19
12. Biological Control An important ingredient of IPM is biological control and for RPW several potential natural enemies have been identified. Among the biological control agents are Entomo-Pathogenic nematodes (EPNs) Steinernema spp. and Heterorhabditis spp. Under laboratory conditions these nematodes caused very high mortality of RPW larvae and adults. There are some isolates of the pathogenic fungus Beauveria bassiana that provided very good results in the laboratory. Another potential biocontrol agent tested was green mascardine fungus, Metarhizium spp. When the EPNs and B. bassiana were tested individually or in combination produced mortality of the pest in the field. However, the method, time, dose factor etc of using these pathogens in the field needs further research before they become a part of the IPM technology in Saudi Arabia (Figs. 37 38). Fig. 37: Weevils affected by fungus Beauveria bassiana (photo: Omar AlMuhanna) Fig. 38: Weevil affected by green muscardine fungus M. anisopliae (photo: Omar Al Muhanna) 13. Conclusions For the success of IPM, all methods listed above should be combined in a judicious manner and implemented as per the time schedules. Just following a few methods and neglecting other proven methods will not give the desired results. Moreover, the growers of date palm should also actively involve themselves and follow the recommendations for the management of RPW. 20