Equipping a multi-engined aircraft with a fuselage-mounted spray system for the ultra-low-volume application of malathion.

J'/otes Equipping a Multi-engined Aircraft with a Fuselage-mounted Spray System for the Ultra-Low-Volume Application of Malathion * by CLIFFORD S. LOFGREN 1 HUGH R. FORD,2 ROBERT J. TONN 3 & SUJARTI JATANASEN 4 Early in 1968, a field trial was conducted with the ultra-low-volume (ULV) method of aerial applica- tion of insecticides in Bangkok, Thailand, for Aedes aegypti L. control (Kilpatrick et al., 1970). Two dosages of malathion ULV concentrate of 3 US fl oz/acre and 6 US fl oz/acre (approx. 219 ml/ha and 438 ml/ha) 5 were applied to 3 small villages on the outskirts of Bangkok using a Cessna-180 single- engined aircraft. The results of the tests with the higher dosage were very encouraging. Following 1 application the biting rate of A. aegypti fell from an average pretreatment count of about 15 per man per hour to 6 per man per hour. The biting rate dropped to less than 1 per man per hour following a second application 4 days after the first, then rose slightly after 2 days but fell again to a minimum of 0.37 bite per man per hour after a third application. The percentage of positive oviposition traps decreased from 50% to 0 during the same period. In the same area the Culexpipiensfatigans biting rate was reduced by about 90 %. A high kill of caged adult mosquitos placed within houses was achieved and 100% mortality of caged mosquitos placed outdoors occurred. The success of this field trial indicates that the judicious use of ULV malathion spraying may be useful in the interruption of an epidemic of haemor- rhagic fever; however, if this is done over large urban areas, safety requirements would necessitate * From the WHO Aedes Research Unit, Bangkok, Thailand. This study was supported jointly by the Public Health Service Research Grant No. CC 00174 from the National Communicable Disease Center, Atlanta, Ga., USA, and by the World Health Organization. 1 Entomologist, Entomology Research Division, US De- partment of Agriculture, Gainsville, Fla., USA. "Agricultural research technician, Entomology Research Division, US Department of Agriculture, Gainsville, Fla., USA. 'Project Leader, WHO Aedes Research Unit, Bangkok, Thailand. ' Communicable Diseases (Control) Division, Ministry of Health, Bangkok, Thailand. ' Conversion factors: I US fl oz = 0.961 Imp. fl oz = 29.57 ml. the use of multi-engined aircraft. The swaths 500 ft (152 m) or more wide that are attainable with larger aircraft would greatly increase the efficiency and rapidity with which the affected area could be treated. It is very difficult in developing countries, however, to obtain suitable aircraft equipped with conventional insecticide spraying equipment. As a means of overcoming this problem, the World Health Organization decided to evaluate an existing insecticide spraying system 6 that can be mounted in the fuselage of C-47 aircraft and does not require wing-booms. This system and the rationale behind its development are described in a separate paper (Glancey et al., 1969). Essentially, it consists of a gear-pump, driven by a 12- or 24-volt motor, that pumps insecticide through a small boom mounted below the fuselage. Distribution of the insecticide is dependent on the production of small droplets that can be carried by cross-winds across the treat- ment area. The system can be installed or removed very quickly (<4 hours); thus an airplane can be converted for spraying and subsequently reconverted to its original usage very rapidly. On the basis of the preceding information a study was undertaken by the WHO Aedes Research Unit, Bangkok, to determine (1) the feasibility of controlling A. aegypti in a large city with ULV malathion applied at 6 US fl oz/acre (438 ml/ha) and (2) the suitability of the fuselage-mounted spray boom for ULV application of insecticides. This paper presents a description of the spraying equip- ment and the method of mounting it on the aircraft. The effectiveness of the system in spraying malathion for control of A. aegypti is described in a companion paper (Lofgren et al., 1970). Preparation and installation of spray rig The apparatus, as assembled for these tests, was mounted in a C-47 transport aircraft belonging to ' Designed by the Insects Infecting Man Laboratory, Entomology Research Division, Agricultural Research Ser- vice, US Department of Agriculture, Gainesville, Fla. 2462A - 157 - 11 NOTES the Royal Thai Air Force. Arrangements were made with the Royal Thai Air Force to install the spray rig and to make available the aircraft and a flight crew on test-dates specified in advance. Most of the parts for the spraying equipment were purchased in the USA; a few items, such as steel plates and plastic tubing, as well as materials for the barrel- rack and welding services, were obtained in Bangkok. Installation of the system was carried out at the Royal Thai Air Force Base at Don Muang. Boom-assembly. The boom-assembly consisted of 3 sections of galvanized pipe fitted together in an inverted " T " formation with a bend in the middle (see Fig. 1). The lower section, which formed the actual spray boom, was 36 in (91.4 cm) long. It was formed by screwing 2 sections of pipe, 16 in (40.6 cm) long, into either side of a T-fitting and capping the open ends (Fig. 3). Positions for 10 nozzles were made by drilling and tapping holes, 3 in (7.6 cm) apart, along the boom. Nipples were placed in the holes and Tee-Jet nozzles were inserted. The upper vertical section of the boom-assembly was 48 in (1.22 m) long and this was joined, by a 450 elbow, to the middle section, which was 18 in (45.7 cm) long. The middle section was cut into 2 pieces and a union was inserted so that the lower boom section could be put on or taken off quickly. A flange of steel 1/4 in (6.4 mm) thick and 1 in (25.4 mm) wide was welded along the entire length of the upright section. Half-inch holes, 6 in (15 cm) apart, were drilled along the length of the flange, so that it could be fixed at different levels. The boom-assembly was installed in the following manner. A section of the floor over the inspection plates in the fuselage, near the cargo doors, was removed. The centre inspection plate in the fuselage was then removed. The upper section of the boom- assembly, with the 450 elbow, was lowered through the hole with the flange towards the front and the section below the elbow pointing towards the rear of the plane. Two steel plates, 8 in by 18 in (20.3 cmx45.7 cm), with holes cut in the centre to fit the shape of the pipe and flange were placed on the pipe and positioned, one above and one below, the 2 airframe girders just above the inspec- tion hole (see Fig. 1 and 2). The plates were bolted firmly in place with 6 bolts so that they formed a solid support for the boom. The upper plate had 2 small brackets welded to it, one on either side of the flange on the pipe. Holes in these brackets matched holes in the pipe-flange so that the entire boom assembly could be attached firmly to the plate with a short bolt. When the upper part of the boom assembly was firmly in place, the lower section was joined to it at the union with the nozzle section horizontal. The hole formed by removal of the floor section was covered with l/2-inch plywood cut to fit around the plate holding the boom assembly. Nozzles were affixed to the boom and tips of the required size inserted. With the boom mounted in this manner, and the nozzles properly aligned, the nozzles all pointed forward at a 450 angle (see Fig. 1 and 3). This position is required for the production of small droplets. A 90° elbow was affixed to the top of the upright section of the boom and a line strainer was attached to it. Flexible pressure hose (800 lbf/in2, i.e., 56.25 kgf/ cm2) was used to connect the strainer to the gauge side of the pump. The position of the boom underneath the aircraft was controlled by removing the bolt from the brackets, raising or lowering the boom assembly to a new position, and replacing the bolt. Just before, or during a flight the boom was lowered to its operating position, 30 in (75 cm) below the fuselage; in this position the boom was about 8 in (20 cm) from the ground and did not interfere with take-off or landing of the aircraft. Pump system. The insecticide pump system con- sisted of an Oberdorfer gear-pump (7000 R) driven by a 12-volt, 1-horsepower DC motor. The motor and pump were connected with a direct-drive coupl- ing and mounted on a plywood base; this in turn was placed in a sheet-metal tray of the same size to catch any insecticide spillage. The tray was attached to the plywood board used to replace the section of floor removed for the boom installation (see Fig. 2 and 4). A pressure gauge (0-100 lbf/in2) was installed on the boom side of the pump. The gear-pump con- tained an internal by-pass system and a relief valve for controlling pressures. The electric motor was operated with six 12-volt storage batteries wired in parallel. A 50-A breaker- switch was wired into the system as shown in Fig. 2. An operator riding in the aircraft used this switch to start the motor during spraying operations. It was necessary to use batteries because it was im- possible to take a 12-volt circuit off the 24-volt electrical system of the aircraft. The actual current used by the system was not determined, but it was 158 EQUIPPING AN AIRCRAFT FOR ULTRA-LOW-VOLUME MALATHION SPRAYING estimated to be 30 A. At this rate six 12-volt, 70-Ah batteries could certainly operate the system for at least 4 hours. This was sufficient for a normal insec- ticide-spraying operation since weather conditions were usually optimum for only 2-3 hours each morn- ing, and because the motor operates only during the actual spraying runs. Thus it should be feasible to operate the equipment on batteries, if suitable recharging facilities were available between spraying missions. Insecticide tank. Since it was not possible to obtain a large tank for holding the insecticide it was necessary to substitute the 55-US gal (approx. 208-litre) malathion drums for this purpose. This was accomplished by constructing a wooden rack as shown in Fig. 5 in which the drums could be cradled. A maximum of 5 drums was used at one time. The drums were securely fastened in the plane by looping chains over the drums and securing them to load rings in the floor of the aircraft (Fig. 6). Before the drums were placed in the racks, ½/2-in (12.7-mm) gate-valves were installed in the small opening on the top of the drums. A 6-in vent pipe was put in the large opening using a bushing, a 900 elbow and a 6-in (15-cm) section of pipe with a cap (see Fig. I and 6). The vent pipe was turned FIG. 1 SIDE VIEW OF BOOM-ASSEMBLY MOUNTING AND INSECTICIDE DRUMS IN RACK Strainer, S9' elbow Wm eame FIG. 2 TOP VIEW OF PUMP SYSTEM AND PLATE MOUNTING FOR THE BOOM-ASSEMBLY 11No 90162 159 NOTES FIG. 3 SPRAY BOOM IN POSITION UNDER THE AIRCRAFT C y.' ....4.>.. FIG. 4 ELECTRIC MOTOR, SPRAY PUMP AND UPRIGHT SECTION OF THE BOOM-ASSEMBLY INSTALLED INSIDE THE AIRCRAFT 160 EQUIPPING AN AIRCRAFT FOR ULTRA-LOW-VOLUME MALATHION SPRAYING FIG. 5 RACK FOR HOLDING MALATHION DRUMS 3/in, 8 11 _17,in - 55/0 _ ~~~~~~~~~~~125in FIG. 6 DRUMS IN POSITION INSIDE THE AIRCRAFT inside the rim during loading and turned up when the drum was in position in the rack. The drums were loaded on the plane with a fork-lift, pushed to a position opposite one of the slots in the rack and lowered into the rack. The drum was turned so the gate valve was at the bottom; the vent pipe was then turned up. A ½/2-in (12.7-mm) 900 elbow was attached to the gate valve on the drum furthest from the pump and ½/2-in (12.7-mm) tees in the other valves. Short nipples were screwed in the elbow and tees and the nipples on each drum connected to those on the drum in front or behind it with clear plastic tubing. The tubing was fastened to the nipples with hose clamps. Plastic tubing was also used to connect the rear drum to the insecticide pump. This system operated satisfactorily for our tests, however a large insecticide tank would have been much more convenient. The 55-US gal drums are heavy (598 lb, i.e., 271 kg) and difficult to move. If a glass-fibre tank of about 250 US gal (946 litres) capacity were used, it could be installed in a similar manner and it could be filled from the drums, by means of the pump on the spray system or a separate 161 NOTES transfer pump. This system would make it un- necessary to disconnect the insecticide lines and would avoid the resulting spillage and contamination of the aircraft. Calibration Two application rates were used during the course of our studies, 3 US fl oz and 6 US fl oz per acre (219 ml/ha and 438 ml/ha). Since the airplane was operated at a speed of 150 mi/h (241 km/h) and with a 500-ft (152-m) swath width, the output necessary to obtain the application rates was 31/2 US gal and 7 US gal per min (13.2 litres and 26.5 litres per min) respectively. With a 10-nozzle boom. flat fan tips no. 8004 and 8008 were required to obtain the desired output. At 40 lbf/in2 (2.81 kgf/cm2) the 10 tips of these sizes will deliver 4 US gal and 8 US gal (15.1 litres and 30.3 litres) per min of water, respectively. Malathion, however, is more viscous and flows at 0.86 times the rate of water. Thus the actual flow rates at 40 lbf/in" should be 3.44 US gal and 6.88 US gal (13.02 litres and 26.04 litres) per min. These rates are theoretical, however, and depend on complete accuracy of tip size and other factors. The system was calibrated several times by placing short pieces of plastic tubing over the tips and directing 5 into one plastic bucket and the other 5 into another bucket (see Fig. 7). The pump system was then operated and malathion was pumped through the system for 30 seconds. The quantity ofmalathion was measured and minor adjustments of the flow rate were made by adjusting the line pressure with the pressure- relief valve. For the dosages required a line pressure of 46 lbf/in2 (3.23 kgf/cm2) was necessary. Discussion and conclusions Once all the spray system parts were assembled and the aircraft was ready, the equipment could be installed in 2-4 hours. At the end of the tests it was completely removed and the aircraft was returned to the Air Force in half-an-hour. During spraying operations the equipment was operated by one man in the aircraft. Ordinarily this would have been done by the pilot or co-pilot, but since this equipment was experimental, the operator was required to check that it functioned properly. The equipment operated satisfactorily throughout the tests and all treatments were completed on schedule. FIG. 7 CALIBRATION OF THE NOZZLE TIPS 162 EQUIPPING AN AIRCRAFT FOR ULTRA-LOW-VOLUME MALATHION SPRAYING 163 ACKNOWLEDGEMENTS We wish to thank the Royal Thai Air Force for the use of the aircraft during these experiments. Special thanks go to Colonel Vere Thaikla, Major Somsawart Sudsatya, and Captain Ampol Javusombat for their as- sistance during preparation of the aircraft and in securing a flight schedule. We are grateful for the help of Colonel Marshall and Major Reynolds of JUSMAC-MACTHAI for their assistance in the spraying operation. Finally we wish to thank the many members of the Royal Thai Air Force who helped us in so many ways during the experiment. REFERENCES Glancey, B. M., Ford, H. R. & Lofgren, C. S. (1969) Mosquito News (in press) Kilpatrick, J. W., Tonn, R. J. & Jatanasen, S. (1970) Bull. Wid Hlth Org., 42, 1-14 Lofgren, C. S., Ford, H. R., Tonn, R. J. & Jatanasen, S. (1970) Bull. Wld Hlth Org., 42, 15-25 Effet de la vaccination par Plasmodium berghei irradie sur I'activite phagocytaire du systeme reticulo-endothelial au cours de l'infection du rat par ce plasmodium* par G. Biozzi,' C. STIFFEL,2 D. MOUTON,3 C. DECREUSEFOND,4 A. CORRADETTI,5 F. VEROLINI,6 A. Bucci 7 & A. VENTURA 8 Le role preponderant des macrophages du systeme rdticulo-endothelial (SRE) dans les m6canismes de defense contre les maladies infectieuses est connu depuis longtemps et a e't r6cemment confirme par l'emploi des m6thodes quantitatives d'exploration de l'activit6 du SRE (Biozzi et al., 1953, 1957, 1963). Deux constatations essentielles se degagent de ces etudes: 1) L'activit6 fonctionnelle du SRE subit des modifications importantes au cours de l'infection. * Cette recherche a b6nefici6 d'une aide financiere de l'Organisation mondiale de la Sante. I Directeur de Recherches, Centre national de la Recherche scientifique, Paris, France. ' Maitre de Recherches, Centre national de la Recherche scientifique, Paris. 'Charg6e de Recherches, Association Claude Bernard, Paris. ' Biologiste adjointe, Centre national de la Recherche scientifique, Paris. ' Directeur, Laboratoire de Parasitologie, Istituto Supe- riore di Sanita, Rome, Italie. ' Charg6 de Recherches, Laboratoire de Parasitologie, Istituto Superiore di Sanita, Rome. I Assistant, Laboratoire de Parasitologie, Istituto Supe- riore di Sanita, Rome. ' Boursier, Laboratoire de Parasitologie, Istituto Supe- riore di Sanita, Rome. 2) La stimulation prealable du SRE augmente la resistance des animaux envers des infections produites par des micro-organismes capables de survivre dans le cytoplasme des macrophages (Howard, 1961; Howard et al., 1959). Comme dans le cas des infections bacteriennes, la defense de l'organisme envers les infections provo- quees par des plasmodiums s'effectue selon deux mecanismes fondamentaux: a) un mecanisme specifique constitue par la reponse immunologique; b) un mecanisme non specifique dont la manifes- tation principale est la phagocytose (Zuckerman, 1968). Ces deux mecanismes peuvent etre associes, comme lors de l'intervention des anticorps opsoni- sants qui facilitent la phagocytose. Dans le cas de l'infection paludeenne, la presence d'opsonines a ete demontree par Zuckerman (1945) et l'importance de I'immunite sp6cifique ressort clairement des expe- riences de Corradetti et al. (1966) qui obtiennent une protection contre la maladie par la vaccination avec le parasite irradie. 2462B