Notes on the Palmetto Weevil, Rhynchophoru5 Cruentatus (Coleoptera: Curculionidae)1
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The cyclical nature of the color response was probably needed under Florida conditions to identify the level of due to the leaching and uptake of nitrogen, denitrification nitrogen in the soil solution which corresponds to moder or volatilization of ammonia (NH3) which is associated with ate plant growth, acceptable color and little or no leaching soil urea application (3). The magnitude of the color de into the ground water. Relate work being conducted at a cline 4 weeks after treatment was reduced at the higher number of institutions for nursery crops grown in contain nitrogen rates; however, fertilizer cost increases, excessive ers needs to be expanded to include the affects of fertiliza shoot growth may result and turf may be injured when tion on plant growth, leaching and runoff on landscape applying more than 1 lb N/1000 ft2 in one application in sites. hot weather (2). This could become important if the fer tilized plant was growing in a turf area and the material Literature Cited was surface broadcast applied over the turf. If more than 1 lb N/1000 ft2 were to be applied to a turf area, consider 1. Dasberg, S. 1987. Nitrogen fertilization in citrus orchards. Plant and ation should be given to placing the material below the soil Soil 100:1-9. surface. 2. Hamilton, D. F., M. E. C. Graca, and S. D. Verkade. 1981. Critical effects of fertility on root and shoot growth of selected landscape Hibiscus leaf color was found to be sensitive to nitrogen plants. J. of Arboricul. 7:281-290. rate. Moderate growth and acceptable leaf color was main 3. Katyal, J. C, B. Singh, P. L. G. Vlek, and R. J. Buresh. 1987. Efficient tained by applying 1 lb N/1000 ft2/application (5 lbs N/1000 nitrogen use as affected by urea application and irrigation sequence ft2/year). Wright and Hale (2) stated that 3.5 lbs N/1000 Soil Sci. 51:366-370. 4. Morton, T. G., a. J. Gold, and W. M. Sullivan. 1988. Influence of ft2/yr was adequate for shade tree growth with no growth overwatering and fertilization on nitrogen losses from home lawns. increase at the 7 lb rate. Ponder et al. (6) reported nitrogen J. Environ. Qual. 17:124-130. rate from 0-8 lbs N/1000 ft2/yr had no effect on tree 5. Neely, D. 1984. Grass competition for nitrogen around landscape growth. Citrus, world-wide, is considered not to respond trees. J. Environ. Hort. 2:86-88. to applications of nitrogen in excess of 4 lbs N/1000 ft2/yr 6. Ponder, H. G., C. H. Gilliam, E. Wilkenson, J. Eason, and C. e. Evans. 1984. Influence of trickle irrigation and nitrogen rates to Acer rubrum (1). Yearly applications of nitrogen in excess of 4 to 5 lbs L. J. Environ. Hort. 2:40-43. N/1000 ft2 may not be warranted and could cause ground 7. Still, S. M., C. W. Gilliam, and M. E. Watson. 1980. Effects of nitrogen water contamination due to leaching. Leaching losses of fertilization on Acer rubrum 'Red Sunset' grown in containers. Hort inorganic N from turf subjected to fertilization (5 lb N/ Sci. 15(5):641-642. 8. Terman, G. L. 1979. Volatilizastion losses of nitrogen ammonia from 1000 ft2/yr) and irrigation (1.5 in/wk) practices associated surface applied fertilizers, organic amendments, and crop residues with home lawn care in New England did not appear to Adv. Agron. 31:189-223. pose a threat to drinking water (4). Higher application 9. van de Werken, H. 1984. Fertilization practices as they influence the rates have not been tested for ground water contamina growth rate of young shade trees. J. Environ. Hort. 2:64-69. tion, but most research shows little or no growth response 10. Wright, R. H. and E. B. Hale. 1983. Growth of three shade tree genera as influenced by irrigation and nitrogen rates. I. environ. to yearly rates above 5 lbs N/1000 ft2. Further study is Hort. 1:5-6. Proc. Fla. State Hort. Soc. 101:101-107. 1988. NOTES ON THE PALMETTO WEEVIL, RHYNCHOPHORU5 CRUENTATUS (COLEOPTERA: CURCULIONIDAE)1 Robin M. Giblin-Davis and F. W. Howard transplanted mature cabbage palmetto, Sabal palmetto University of Florida, IFAS (Walter), at one survey site in Broward County, FL. Experi Fort Lauderdale Research and Education Center ments demonstrated that this weevil is not a primary invader 3205 College Avenue of healthy palm trees but is attracted to and infests stressed, Fort Lauderdale, FL 33314 dying, and aged palms. Because palms may suffer stress as sociated with the transplanting process, and roots of cabbage Additional index words. Sabal palmetto, cabbage palmetto, palmettos regenerate slowly, recently transplanted palms are Phoenix canariensis, Canary Island Date palm, chemical con at extended risk of invasion by the palmetto weevil. trol. Prophylactic measures for reducing this risk during and fol lowing transplanting of cabbage palmettos and Canary Is Abstract. Research is reported concerning the biology, ecology, land Date palms, Phoenix canariensis Hortorum ex Chabaud, and control of the palmetto weevil, Rhynchophorus cruen- are discussed. tatus (Fabricius). This weevil caused losses of about 8% in The largest weevil in the continental U.S. is the pal metto weevil, Rhynchophorus cruentatus (Fabricius) (18) (Fig. Florida Agricultural Experiment Station Journal Series No. 9447. This research was supported by a U.S. Department of Agriculture Special 1). Unfortunately, size, 1.9-3.0 cm (3/4 to 1 3/16 inches Grant in Tropical and Subtropical Agriculture, 86-CRSR-2-2841 to long), is not its only claim to fame (18). This weevil has R.M.G-D. This paper contains research results of experimental pesticide been shown to be an important pest of stressed cabbage applications, but it does not offer recommendations for pesticide use. All palmettos, Sabal palmetto (Walter), and Canary Island Date uses of pesticides must be registered by federal or state authorities, or both, before their uses could be recommended. Consult the Cooperative palms, Phoenix canariensis Hortorum ex Chabaud (9). Rhyn Extension Service for current pesticide registration information and re chophorus cruentatus belongs to the family Curculionidae, commendations. subfamily Rhynchophorinae (= Calendrinae) and tribe Proc. Fla. State Hort. Soc. 101: 1988. 101 Fig. 1. Adult female palmetto weevils, Rhynchophorus cruentatus, showing natural size and color pattern variability (bar = 2 cm). Photo by Jim DeFilippis Rhynchophorini (15). The family Curculionidae (snout consumers. We have harvested larvae from the field as weevils) is estimated to include over 60,000 species of bee heavy as 6 grams, although the average last instar larva tles that feed upon a very diverse variety of plant species weighs between 3.5 to 5 grams (8). We are aware of no one (5). Part of their overall success as a group is attributed to who eats the larvae of the palmetto weevil in the U.S. How the elongation of the stomal region into a snout which ever, the larvae of the palm weevil, R. palmarum (Linneaus), bears tiny mandibles at its apex used for preparing ovipos- have been consumed and are considered a delicacy by ition holes and for feeding (5). In addition, the larvae of some South American natives (18). The last instar larva weevils are endophytic, feeding inside the plant host where migrates into an area of the host that is fibrous, such as they are protected from predators, the environment, and the periphery of the stem or the petiolar bases of the insecticides. leaves, to prepare a cocoon from the palm fiber. The larva enters the prepupal stage (Fig. 3A) within the cocoon and then molts to the pupa (Fig. 3B). Within several days to 2 Palmetto Weevil Life Cycle weeks, depending upon the temperature, the adult (Fig. Rhynchophorus cruentatus has a complete life cycle 3C) ecloses from the pupa. The adults will often sit several (holometabolous) with an egg, several larval instars (Fig. days in the cocoon before emergence. 2), prepupal (Fig. 3A), pupal (Fig. 3B), and adult stages The average number of live palmetto weevils of all (Fig. 1). In nature, the life cycle of the palmetto weevil can stages recovered per lethally infested cabbage palmetto was take less than 84 days to complete (9) and there can be 48 ± 68 (range = 1-214) (n = 9 palms) (9). Adjustments more than one generation per year in southern Florida for larval and pupal mortality suggest that 23-32 new (multivoltine). The eggs are laid deep in the petiolar bases adults will be produced from an average lethal infestation of host leaves or in wounds or cuts in the host palm. In the in a cabbage palmetto in southern Florida (9). The adults laboratory, an average palmetto weevil female can lay 26 are long-lived; males survived 87 ± 41 days (range = 6- ±15 eggs (range = 0-48) with a 42 ± 19 day oviposition 150) and females survived 74 ± 16 days (range = 40-113) period (range = 0-70) (8). The eggs hatch in 69 ± 17 when confined on pineapple slices (8). The average weight hours (8). The weevil larvae grow and molt several times of newly-emerged adult males was 1.14 ± 0.22 g (range while consuming increasingly larger volumes of plant tis = 0.83-1.65) (n = 20) compared with 1.14 ± 0.27 (range sue. The larvae have large mandibles and are voracious = 0.61-1.50) (n = 20) for females (8). The adult male 102 Proc. Fla. State Hort. Soc. 101: 1988. ture and Consumer Services, Division of Plant Industry, Gainesville were surveyed by Giblin-Davis and Howard (9) to better understand the host range of the palmetto weevil.