404 FLORIDA STATE HORTICULTURAL SOCIETY, 1972

attractancy of bacteria cultures to Anoetus was populations of Anoetus were the most migratory consistent with previous tests. and best stage by which to test attractancy of cultures. The hypopus is a non-feeding migratory Discussion form resistant to, and apparently formed as a re sult of environmental stress. They are transported, The soil-inhabiting, saprophytic mites Anoetus or will migrate, to areas of higher nutritional feroniarum and Rhizoglyphus robini can survive levels and lower environmental stress before com and reproduce on several fungi and bacteria com pletion of life cycle (6, 8). Since both Rhizogly monly associated with Gladiolus hortulansus. Anoe phus and Anoetus have a hypopal state in their tus is strongly attracted to bacterial cultures of life cycle, the importance of this stage relative Pseudomonas marginata and Pseudomonas mar- to their suggested vector roles demands further ginalis. Rhizoglyphus prefers Fusarium oxy- study. sporum. The fact that mites are attracted to selected Literature Cited phytopathogens may be important in elucidating 1. Bald, J. G. and R. N. Jefferson. 1952. Injury to possible disease-vector relationships of gladiolus gladioli associated with the root mite, Rhizoglyphus rhizo- in Florida. The demonstrated affinity by Anoetus phagus. Dis. Reptr. 36: 435-437. 2. Englehard, A. W. 1969. mites associated with for bacterial cultures, in particular the pathogenic diseases of gladioli and other crops in Florida. Phytopath ology 59: 1025 (Abstr.). isolate P. marginata Br-1, suggest that thevector 3. Forsberg, J. L. 1959. Relationship of the bulb mite capabilities ofthis mite should be investigated. Rhizoglyphus echinopus to bacterial scab of gladiolus. Phy topathology 49: 539 (Abstr.). Conversely, the demonstrated affinity by Rhizo 4. . 1965. The relationship of Pseu domonas marginata, Stromatinia gladioli, bulb mites, and glyphus for Fusarium cultures, and not bacterial chemical soil treatments to the occurrence and control of cultures, does not readily relate to published re scab and Stromatinia rot of gladiolus. Phytopathology 55: 1058 (Abstr.). ports implicating Rhizoglyphus mites as vectors of 5. Lelliott, R. A., Eve Billing, and A. C. Hayward. 1966. A determinative scheme for the flouorescent plant patho the causal organism of bacterial scab, P. margin genic pseudomonads. J. Appl. Bacteriol. 29: 470-489. ata. It shouldbe pointed out that the of 6. Poe, S. L. 1966. A study of certain factors influencing hypopial transformation in Caloglyphus boharti (Acarina: Rhizoglyphus used in these experiments is not Tyroglyphidae) M. Sc. Thesis, Northwestern State College, Natchitoches, Louisiana. the same as reported by Forsberg (3, 4) to be a 7. 1971. Microfaunal populations on vector of P. marginata. Species, or even clonal, gladiolus . The Florida Entomologist 54: 127-133. 8. Woodring, J. P. 1963. The nutrition and biology of variation in preferences for certain disease-causing saprophytic sarcoptiforms. In Advances in Acarology. J. A. Naegele (ed). 1: 89-111. organisms should be investigated. 9. Yoshizawa, T., I. Yamamoto, and R. Yamamoto. 1971. As noted in Experiments 3, 4, 5, hypopal Synergistic attractancy of cheese components for cheese mites, Tyrophagus putrescentiae. Botyu-Kagaku. 36: 1-7.

SEED PROPAGATION OF AND

R. D. Hartman and F. W. Zettler taining pathogen-free as well as new hy brids. Through cross pollination, viable seed of I FAS Plant Pathology Department caladium (Caladium hortulanum Birdsey) and Gainesville dieffenbachia (Dieffenbachia picta Schott) were and obtained. Each fertilized caladium ovary con J. F. Knauss and Eleanor M. Hawkins tained < 14 seeds whereas dieffenbachia ovaries were single-seeded. Caladium fruits ripened 5-6 IF AS Agricultural Research Center, weeks after pollination and abscissed from the Apopka spadix. Dieffenbachia fruits became red upon ripening 10-12 weeks after pollination, but re Abstract. Aroids do not ordinarily set seed mained loosely attached to the spadix. Seed of under natural conditions in Florida and hence are both species germinated readily when removed commercially propagated by vegetative means. from the fruit and planted in moist peat. However, producing seedprovides a means of ob- Plants of the family comprise a sub Florida Agricultural Experiment Stations Journal Series stantial proportion of the ornamentals produced No. 4615. HARTMAN ET AL.: CALADIUM AND DIFFENBACHIA FROM SEED 405

commercially in Florida. Approximately 96% of Materials and Methods the world's commercially produced are grown in Florida (7), and aroids such as aglao- The crosses were made between plants of nema, dieffenbachia, philodendron, pothos and syn- Dieffenbachia picta (Schott) 'Exotica' or Calad gonium account for nearly half of the State's ium hortulanum (Birdsey) 'Candidum.' The pa foliage industry (9). In addition, Ci*yptocoryne rental stock used in these crosses was provided spp. are aroids of considerable significance to Flor by Mr. Lamont Marchman of Evergreen Gardens ida's unique aquarium plant industry. Aroids are of Apopka, Inc. and Mr. Norman Hickerson of propagated commercially almost exclusively by Hickerson Flowers, Inc., of Apopka, Florida. Dief vegetative means rather than by seed. fenbachia plants were grown in a stock bed in a fiberglass house at Apopka and pollinated May- Various nematodes, bacteria and fungi infest June, 1971, whereas caladiums were grown in avoid nursery plantings in Florida and cause Gainesville either in a greenhouse or outdoors and serious economic losses. In addition, a virus of pollinated May-June, 1972. The pollination pro aroids called dasheen mosaic virus has been cedures were similar to those described by McCol shown to be widespread in Florida and elsewhere ley and Miller (8) for philodendron. All crosses (1, 3, 11). Hartman and Zettler (5) surveyed were made between 6-10 a.m. or 5-8 p.m. Caladium foliage nurseries and caladium plantings in Florida and dieffenbachia like philodendron are dicho- and provided evidence that certain mainstay dief gamous. Pollen was collected daily with a camel- fenbachia and caladium are uniformly in hair brush and transferred within 48 hours after fected with dasheen mosaic virus and hence virus- shedding to neighboring receptive blooms of differ free plants are no longer available. Such wide ent plants. Bloom receptivity was indicated 1) spread incidence of disease among aroids is abetted when the spathe began to unfurl revealing the dis by propagating these plants vegetatively. As tal portion of the spadix and 2) by the increased pointed out by Baker (2), relatively few plant stickiness of the stigmatic surfaces of the spadix. pathogens are seed-bome, and thus, seed propa Prior to pollination, the spathe was cut away from gation provides a useful means of eliminating phy- the spadix, discarded, and the pollen was gently topathogens that have proliferated in vegetative applied to the proximal ovulate portion of the material. lily, for example, is an aroid that spadix with a brush. can be grown free of soft-rot bacteria, water molds and Rhizoctonia infections by planting seed rather than corms (2). Results

Despite the considerable potential of seed propa Dieffenbachia fruits, although cream colored gation as a method to rid aroids of phytopathogens during most of their development, became red when and to create new horticultural varieties, most ripe approximately 10-12 weeks after pollination. Florida growers are not aware of the techniques Dieffenbachia fruits did not abscise but remained involved in producing aroid seed. A notable excep loosely attached to the spadix (Fig. 1). A spadix tion is the hybridization of philodendrons as de bore 15-30 ovaries, each containing a single round scribed by McColley and Miller (8) and by West seed 5-6 mm in diameter which was green when and Miller (10). Caladium growers once were mature. Seeds germinated within 20 days after supplied with new caladium hybrids by Mr. Frank they were removed from the fruit and planted in M. Joyner, a caladium hobbyist from Tampa, but moist peat. he has become inactive in recent years and this Unlike dieffenbachia, caladium fruits ripened work has since received no attention. Dieffenbachia 5-6 weeks after pollination and abscissed from the species were once hybridized at the turn of the spadix (Fig. 2). The exposed fruit surfaces re century, but are no longer grown from seed; thus mained green throughout their development with growers must rely upon chance somatic mutations out apparent color change at the time of abscission. for new cultivars. As indicated by McColley and The unexposed surfaces of the ovary walls were Miller (8), special techniques must be employed cream-colored at maturity. Ovulate portions of the to obtain seed of many aroids. Unfortunately the spadix contained approximately 200 seed-bearing paucity of published reports on the specific hy ovaries, each containing 1-14 oval seeds which bridization techniques for aroids deters growers were 1-1.5 mm in length and light tan in color. from using seed propagation as a useful and im As many as 1500 seeds were obtained from a portant tool. Accordingly, this study with dief single spadix. Seeds germinated readily 8-10 fenbachia and caladium was conducted. days after removal from the fruit and planting 406 FLORIDA STATE HORTICULTURAL SOCIETY, 1972

Fig. 1. Dieffenbachia spadix. A) during pollen shed. B) developing fruit 5-6 weeks after pollination. C) mature fruit 10-12 weeks after pollination.

Fig. 2 Caladium spadix. A) at time of pollination. B) distal portion during pollen shed. C) proximal portion just prior to fruit abscission. D) shed fruit at abscission 5-6 weeks after pollination. HARTMAN ET AL.: CALADIUM AND DIFFENBACHIA FROM SEED 407

B

Fig. 3. Dieffenbachia seedlings 12 months after germination. Note differences in foliar variegation patterns (A) and in degree of shoot proliferation (B). 408 FLORIDA STATE HORTICULTURAL SOCIETY, 1972

them in moist peat. Seed germination rate de genetic potential for deriving improved horticul creased markedly, however, when seeds were tural varieties. A need exists for "color" among dried and stored 2 weeks at 23 C and 53% rela foliage plants such as that provided by the golden- tive humidity. green variegated pothos. A concerted breeding pro- Seedlings were maintained in a greenhouse at grad with species of Dieffenbachia could enrich the about 60% shade in isolation from commercial industry by infusing it with such color, as this aroid stock. Plants were transferred from peat to study suggests. a steam-sterilized soil/perlite mix contained in The genetic potential of caladiums has been clay pots and treated routinely with a liquid formu amply demonstrated in the 2000 or more named lation of 20-20-20 fertilizer. varieties developed by earlier workers such as Although parental 'Exotica' dieffenbachia and Nehrling, Mead, Leitze and others (6). Neverthe 'Candidum' caladium plants used in this study were less, most of these evaluations have been based virus infected as evidenced by symptoms observed upon foliage characters. Incorporation of other at the time of pollination, none of the more than factors such as bulb size and cold-hardiness could 500 resulting dieffenbachia and 1000 caladium be considered in a selective breeding program as progeny displayed virus symptoms, indicating that well. the seedlings were virus free. In a competitive market the value of develop A small percentage of the dieffenbachia seed ing new hybrids is self-evident. What may be more lings exhibited albinistic tendencies and died significant, but less obvious, is the means that shortly after germination. The juvenile foliage of seed propagation provides to rid planting stock the surviving dieffenbachia progeny was nonvarie- of serious plant pathogens. However, when a patho gated and variegated did not develop until gen-free plant is placed in a nursery environment, 4-8 months after germination. Similarly, juvenile it will eventually become infected with the phyto leaves of caladium were homogeneously green and pathogens which plague the parental plants. There variegated leaves did not develop until about 3 fore, once a desirable hybrid is obtained, a certifi months after germination. cation program should be enacted to maintain and A year after germination a marked variation propagate pathogen-free plants. These plants could was noted among the 207 randomly selected dief act as a mother block from which propagating ma fenbachia seedlings which had grown to 30-34 cm terial would be obtained for nursery production. in height. Fifty-three of the progeny exhibited The technique of meristem-tip culture provides a none of the white variegation typical of the 'Exoti means of rapid propagation and maintainence ca' parents. The foliar patterns of the remaining of plants in a sterile environment and would be an progeny varied from those having relatively local important facet of a certification program. Meri ized areas of white to those having white patterns stem-tip culturing procedures have been estab exceeding in area that of the original parents lished for caladiums and have proved useful as a (Fig. 3a). A few plants exhibited a degree of means of rapid propagation and maintenance of yellow foliar coloration unlike the 'Exotica' parents. disease-free plants as well as a means of obtaining Marked differences in shape and apical dom pathogen-free plants of established cultivars (4). inance were also noted among the progeny. Where as some of the leaves had dimensions similar to those of the parents, others were somewhat more Literature Cited

lanceolate. Apical dominance was expressed when 1. Alconero, R. and F. W. Zettler. 1971. Virus infections axillary buds of some progeny grew only after the of and in Puerto Rico. Plant Dis. Reptr. 55:506-508. apical meristem was removed, whereas the axillary 2. Baker K. F. 1957. The U. C. system for producing healthy container grown plants. California Agrr. Exp. Sta. buds of other progeny proliferated regardless of & Ext. Service Manual 23. 332 pp. the presence or absence of the apical shoot (Fig. 3. Gollifer, D. E. and J. F. Brown. 1972. Virus diseases of Colocasia esculenta in the British Solomon Islands. Plant 3b). Dis. Reptr. 56:597-599. 4. Hartman, R. D. and F. W. Zettler. 1972. Mericloning as a potential means of obtaining virus free plants from Discussion aroids commercially produced in Florida. Proc. Fourth Org. Soil Vegetable Crops Workshop 60-62. 5. and F. W. Zettler. 1972. Dasheen Our results indicate that seed of dieffenbachia mosaic virus infections in commercial plantings of aroids and caladium can be readily obtained and that the in Florida. Phytopathology 62:804. (Abstr.). 6. Hayward, W. 1950. Fancy-leaved caladiums. Plant progeny, unlike the parents, appeared free of virus Life 6:131-142. 7. Holms, L. L., J. Hendry, L. Tubbs. A. L. Hall, and and other phytopathogens. Our results with dief D. Dittmar. 1965-75. Caladium , Highlands County fenbachia further suggest a rich but ignored DARE Rep. 11 pp. 8. McColley, R. H. and H. N. Miller. 1965. Philodendron NEEL: WEED CONTROL IN CONTAINERS 409 improvement through hybridization. Florida State Hort. 10. West, E. and H. N. Miller. 1956. Some notes on philo- Soc. Proc. 78:409-415. dendron hybrids. Florida State Hort. Soc. Proc. 69:343-347. 9. Waters, W. E. 1969. The ornamental horticulture in 11. Zettler, F. W., M. J. Foxe, R. D. Hartman, J. R. dustry of Florida and its implication to production in Edwardson, and R. G. Christie. 1970. Filamentous viruses tropical Americas. Trop. Regional Proc. Amer. Soc. Hort. infecting dasheen and other araceous plants. Phytopathology Sci. 13:1-8. 60:983-987.

WEED CONTROL IN CONTAINERS WITH HERBICIDE- IMPREGNATED MULCH MATERIALS

P. L. Neel containers. Tolerances of plants in containers and methods and rates of application should be in IF AS, Agricultural Research Center vestigated to determine the best approach to the Fort Laudardale problem (1, 3). Herbicide activity and movement in the soil Abstract. Four herbicides (Dacthal, simazine, is greatly influenced by organic matter in the Treflan, Lasso) incorporated into two types of mix, with high organic matter soils usually re mulch materials (potting soil or pine bark chips) quiring more chemical for a given amount of at rates of 0, 1, 2, 4, and 8 times (x) those recom activity than a mix low in organic matter. Thus mended on soils high in organic matter were ap work done with one soil mix may not be applicable plied in a % inch deep surface layer to "gallon" on another, although it may serve as an indicator (6*4") containers of newly rooted cuttings of of what to expect. (3). Gold Dust Croton (Codiaeum variegatum L.). Perhaps the simplest way to apply herbicide Tests were conducted from October 2, 1971 to is through a sprinkler system. Because the herbi May 2, 1972, at the ARC, Ft. Lauderdale, Florida. cide must cover surface of the soil for full effect, Visual evaluations were made at 2, 4, 8 and its application through a Chapin system is not 28 weeks. No phytotoxicity was observed from feasible since the rate of water application through any treatment. Weed control initially (2-4 weeks) such a system is insufficient to cover the soil sur was good with each herbicide except Dacthal when face. Uniformity and irrigation rate of sprink soil incorporated. After 8 weeks weeds were lers are quite variable. Also, the plant itself may noted in the 1 and 2x rates of both simazine and shield a portion of the soil from direct contact Treflan soil incorporation treatments. After 28 with the herbicide in the water. These factors weeks excessive weed growth was found in every either reduce the margin of safety or reduce soil-incorporation treatment except the 2, 4, and (the potential for) weed control. A variation of 8x rates of Lasso and the 8x rate of Treflan. sprinkler irrigation application would be applying Pine bark chips alone reduced weed growth herbicide by spraying, or watering with a hose, up to 8 weeks, with higher rates of bark-incorpo but again rate of application would be subject to rated Lasso and Treflan providing control at 28 considerable variation depending on methods used weeks. and the technique of the applicator. Herbicides may be applied as granular formu Controlling weed growth in container grown lations, which gives more control of rate, but com nursery stock is a major expense, with up to 30% plete coverage of the soil surface is still a limiting of the cost of production attributable to weed con factor. Of added concern is the possibility that trol with hand labor. There are a number of good granules might be washed down the sides of the herbicides on the market for use in field crops, container if soil shrinkage occurs between but they have been used to a limited extent in waterings. container operations. Many are not even labeled Use of an herbicide-impregnated mulch should for use on container grown ornamental plants. eliminate these problems. Good coverage of the soil This is due to several factors including difficulties surface at a fairly uniform rate of application in controlling rates of application, plant sensi could be obtained. In addition, the mulch material tivity and the limited root volume of plants in can materially reduce weed growth and loss of water, and keep the soil cooler than exposed soil. Fiber disks placed on top of the soil employ the Florida Agricultural Experiment Station.