AIR-BLAST SPRAYER IN THE APPLICATION OF A CITRUS

Transcription

1 BROOKS: HELICOPTER VS. AIR BLAST SPRAYERS Suit, R. F., and A. W. Feldman. 96. Treatment of citrus trees with Cynem for control of Radopholus similis. Plant Dis. Reptr. 45: Tarjan, A. G. 96. Longevity of Radopholus similis (Cobb) in host-free soil. Nematologica 6: Tarjan, A. C, W. A. Simanton, and E. E. Russell A labor-saving device for the collection of nematodes. Phytopathology 46: Van Gundy, S. D., F. J. Foote, R. L. Rackham, and A. Rinkov Studies on methods of application of emplsifiable DBCP around living citrus trees. Plant Dis. Reptr. 44: COMPARISON OF A HELICOPTER WITH A CONVENTIONAL AIR-BLAST SPRAYER IN THE APPLICATION OF A CITRUS SPRAY PROGRAM R. F. Brooks Abstract A heliocopter was compared with a conven tional air-blast sprayer in applying a citrus spray program during the growing seasons of 963 and 964. Each sprayer applied the same amount of pesticide per acre in each application, varying only in the amount of water required. With but exception, there was no significant difference in citrus rust mite control over the 2-year period. The only exception occurred in August 963 when 3 pints of Guthion per acre applied by heliocopter failed to control citrus rust mite. However, the corresponding applica tion by the air-blast sprayer controlled rust mite until November. There was significantly better control of armored scale, whitefly, black scale, and mealy bugs over the 2 years with the air-blast sprayer. There also was significantly better control of greasy spot disease and melanose with the airblast sprayer. Introduction In recent years, much interest has been given to the possibility of spraying Florida citrus groves by helicopter because of reduced applica tion costs. Sutton (3) reported savings of $2.00 to $24.00 per acre in application costs and a slight increase in pack-out where a helicopter spray program was used. Brooks et al. () found helicopters provided poor coverage and unsatis factory control of Glover's scale but satisfactory control of citrus rust mite. Florida Agricultural Experiment Stations Journal Series No lassistant Entomologist, University of Florida Citrus Experiment Station, Lake Alfred. The experiment reported here was designed to compare the effectiveness of a helicopter and a conventional air-blast sprayer in application of a citrus pest control program. The experi ment was initiated in the spring of 963 and conducted through the citrus growing seasons of 963 and 964. Experimental Methods Four widely separated 0-acre groves of ma ture grapefruit trees were each divided into 2 plots. Each plot was sprayed with a helicopter or a conventional air-blast sprayer throughout the citrus growing seasons of 963 and 964. Thus, a randomized blocks design was used with each location serving as a replicate. The 4 groves were located near Auburndale, Dundee, Daven port, and Howey-in-the-Hills, Florida. Ten sam ple trees were selected from the center of each plot in such a manner that each was buffered by at least 2 rows of trees on all sides. The helicopter was a Bell Model G-2A equip ped with a standard Simplex spray pump and boom. The air-blast or air-carrier sprayer was a Speed er Model 705 CP equipped with a double oscillating volute. Only materials listed in the 963 and 964 editions of the "Better Fruit Program" were used in this experiment.2 The post-bloom spray was applied at 2/3 petal fall and the summer oil spray between June 5 and July 5. Other applications were applied as needed for citrus mite or spider mite control. Each sprayer applied the same amount of spray material per acre, but the volume of water varied. The helicopter applied the spray mate rial at the rate of 0 gallons per acre, whereas 2Better Fruit Program and Dust Schedule for Citrus. Florida Citrus Commission. Lakeland, Florida.

2 70 FLORIDA STATE HORTICULTURAL SOCIETY, 965 the air-blast sprayer applied 250 gallons per tions were estimated by counting the number of acre. The spray materials, rates, and schedule citrus red mites and Texas citrus mites per 00 are presented in Table. leaves at 4- to 2-day intervals. Scale insect and Citrus rust mite populations were measured whiten y populations were determined by count at 4- to 2-day intervals by determining the ing the number of third stage female scale and infested percentage of 25 randomly selected whitefly larvae on 50 leaves picked at random leaves and fruit per tree. Spider mite popula- from around the skirt of each tree at 6- to 8-week Table. Application dates, materials and rates per acre of heli copter versus air-blast sprayer experiment. Application Date: Materials in amounts per acre March 26-April 2, 963^ Parathion 2 s Chlorobenzilate 2E, Copper (Cu-We-Red) Zinc (Zn4fe-X) Manganese (Mn-We-X) 3 June 2-8, 963 Miscible Oil, 99.3% Chlorobenzilate 2E 0 3 Gallons August 4-9, 963 Guthion 2E September, 963 Chlorobenzilate 2E, (Helicopter only) November 2-5, 963 April 6-4, 964* Ethion Guthion 2E, Copper (Cu-We-Red) Zinc (Zn-We-X) Manganese (Mn-We-X) 8 July 6-4, 964 Miscible Oil, 99.3% Chlorobenzilate, 0 Gallons.5 September 2-25, 964 Chlorobenzilate.5 December 7-4, 964 Ethion, f Six pounds lead arsenate, 5 pounds of borax per acre applied to all plots with air-blast sprayer.

3 BROOKS: HELICOPTER VS. AIR BLAST SPRAYERS 7 cn o <r a Pottbloom Summtr A i\ l\ k \ l\ \ S Rust Sproy I i /, Mitt Helicopter - leaves Airblast - leaves Fall Mite \ 0 is&- M M 0 N D ^s* <c Figure. Comparison of citrus rust mite populations in a pest control program applied by a helicopter and an air-blast sprayer in Helicopter - leaves Airblast - leaves " O 20 en 5 Fall Mitt Pottbloom Summtr z o l0 Sproy a! 5 0 M M 0 N D Figure 2. Comparison of citrus rust mite populations in a pest control program applied by a helicopter and an airblast sprayer in

4 72 FLORIDA STATE HORTICULTURAL SOCIETY, 965 intervals. Black scale populations were determined by counting the number of crawlers and adults on 25 fruit stems at random around each tree in late June or early July. The number of these fruit found infested with mealybug was also recorded. The incidence of greasy spot disease was recorded at monthly intervals from November through February, using a severity method described by Cohen (2). Melanose was evaluated on the basis of the number of 25 preharvest fruit reduced in grade by having 25 percent or more of the fruit surface affected by melanose lesions. Results and Discussion The results of the citrus rust mite portion of this experiment are presented in Figures and 2. These data show that with exception no significant difference in citrus rust mite control was obtained with either method of application. This exception occurred in August of 963, when a helicopter application of 3 pints of Guthion per acre failed to control citrus rust mite, while the air-blast sprayer application provided control until November. There also was no significant difference in the population of spider mites over the 2-year period. However, the spider mite population was at such low levels that control could not be measured, and the timing of the fall mite spray had to be based on citrus rust mite populations. A comparison of the 2 methods of application for the control of some citrus insects are shown in Table 2. These data reveal that the spray program applied by the air-blast sprayer af forded significantly better control of armored scale insects, whiteflies, black scales, and mealy bugs. The armored scale population increased considerably in the helicopter sprayed plots over the 2-year period while remaining at a very low level in those sprayed with the air-blast sprayer. The population of whitefly was greatly reduced in plots treated with the air-blast sprayer but remained at a very high level where the helicopter was used. Table 2. Comparison of blast sprayer and diseases a helicopter with a conventional airin the control of certain citrus insects Date Method of application* Helicopter Air-blast sprayer Armored scale per leaf (No. 3rd stage? scale) Mar. 963 Feb a b 0.02 a a Whitefly (larvae per leaf) Mar. 963 Oct. 963 Feb a 4.6 b 3.97 b.34 a 0.0 a 0.02 a Black scale (No. per fruit stem) July 963 June Mealybug (Percent fruit infested) July Greasy spot (Disiease severity rat- "**) Jan. 964 Jan b.6 b 0.69 a 0.59 a Melanose (Percent fruit with grade lowering lesions) Dec b 0.7 a f Includes total of Glover, purple, chaff, and yellow scales. for greasy spot ratings: 0, No greasy spot;, 0-25% leaf affected; 2, 26-50% leaf affected; 3, 5% + leaf affected. * Results of Duncan's test: Treatment means followed by different letters are considered significantly different at the 5% level.

5 CALVERT AND REITZ: IRRIGATION WATER SALINITY 73 The 2 methods of application were also com pared in the control of greasy spot and melanose. The results of this portion of the experiment are presented in Table 2. These data reveal that the air-blast sprayer was also more effective than the helicopter in controlling both greasy spot and melanose. Summary A citrus pest control program applied by helicopter was compared with an identical pro gram applied by a conventional air-blast sprayer over a 2-year period. With exception, there was no significant difference in the control of citrus rust mite over the 2-year period. How ever, there was significantly better control of armored scale, whitefly, black scale, mealybug, greasy spot disease, and melanose with the spray program applied by the air-blast sprayer. REFERENCES. Brooks, R. F., W. L. Thompson, and P. J. Jutras Evaluating spray equipment for Florida citrus. Proc. Fla. State Hort. Soc. 76: m. 2. Cohen, Mortimer Greasy spot in Florida-its control and apparent cause. Proc. Fla. State Hort. Soc. 72: Sutton, H. J Commercial citrus pest control by helicopter. Citrus Industry 43(6): 5-6. SALINITY OF WATER FOR SPRINKLE IRRIGATION OF CITRUS David V. Calvert and Herman J. Abstract Reitz2 Foliage injury closely resembling salt burn was observed in several Indian River citrus groves during the severe spring drought of 965. Symptoms included yellowing of leaves, develop ment of necrotic areas on leaves, and defolia tion, with or without visible leaf symptoms. All groves so affected were irrigated during the drought by new, permanently installed, over head sprinkler systems, delivering water at rates of 0.2 inch per hour or less for several hours. Investigations were undertaken to determine whether increase in salt concentration had re cently occurred in water used for such irriga tion, and whether the observed symptoms could be related to salt concentration of water used at low application rates through overhead sprinkler systems. Resampling and analysis of water from 04 artesian wells in the Indian River area were car ried out. Average total dissolved solids of 884 ppm indicated an annual increase of only 2 ppm over the level of 5 years ago when the same Florida Agricultural Experiment Stations Journal Series No luniversity of Florida Indian River Field Laboratory, Fort Pierce. 2University of Florida Citrus Experiment Station, Lake Alfred. wells were sampled. Analysis of the water in seven canals and streams was carried out inter mittently during spring and summer of 965. There was an increase in salt concentration in the water during the spring drought, and a decrease when summer rains were received. Great diversity exists in salinity of these water sources, making highly advisable the continuing analysis by growers of such water supplies be fore and during use. The leaf burn symptoms observed were re produced on 'Ruby Red' grapefruit when artesian water containing 000 ppm total dissolved solids or more was applied at 0.07 inch per hour for nine hours. Burn was more severe with higher concentrations produced by adding sodium chlor ide to the artesian water. The severity of damage increased with increase of salt concentration in the water, with decrease in application rate, and with increase in rate of evaporation of water from leaf surfaces. Extra caution should be exercised in using water containing over 000 ppm total dissolved solids in sprinkler irrigation on citrus. Introduction Considerable leaf burn resembling salt injury (7) was found on trees in several citrus groves in the Indian River area during the spring and early summer of 965. Irregular brown dead areas developed usually near the leaf tips, but sometimes on other parts of leaves. A pro nounced yellowing of the leaf tissue in marginal