Fall webworms are the larvae of the moth, Hyphantia

cunea (Drury). The larvae feed gregariously on foliage of

many different host species from inside an unsightly web.

The larvae are hairy and tan to brown in color. Pecan and

other hardwoods are preferred host plants. Two to five

generations occur each year. Two generations occur on

pecan, one in May-June and another in July-August. Nur

sery trees are usually attacked in September-October. The

larvae are heavily parasitized, but may completely defoliate

small trees in a short time. Removal of the larvae in the

web or by pruning is an alternative to control with insec

ticides.

The forest tent caterpillar is the larvae of the moth,

Malacosoma disstria Hubner, and is closely related to the

eastern tent caterpillar. However, the forest tent caterpillar

does not feed in a webbed tent. The larvae are black and

somewhat hairy with a row of yellow and blue keyhole-

shaped spots down the center of the back. Single larva are

often found in early spring feeding on the buds or new

leaves of a variety of deciduous plant species which they

may severely damage. Application of an insecticide at bud-

break may be necessary to suppress the damage from this

pest.

There are many gaps in our knowledge of these pests

of ornamentals. Table 2 is an outline of the biological and

operational information that are important from an en

tomologist's point of view and lists the types of information

that should be considered in making the best IPM decision.

Many factors are related to characteristics of the pests and

must be considered along with those operational factors

that are controlled by the nurseryman. The relative impor

tance allocated to each of the factors is for the judgment

of the nurseryman. The table should help the decision

maker to gather information in a systematic way and then

to analyze the information within the constraints of his or

her management objectives and the law. Many factors such

as plant protection and quarantine laws, pesticide labels,

etc., are beyond the control of the manager, e.g. fireant

certification, and may override any other choices in the

management plan. However, in 1991 these types of deci

sions by nurserymen from day to day are probably the

exception rather than the rule. In the future it is probable

that fewer tools and more outside regulations will affect

IPM decisions. For this reason it is important that nursery

men constantly update their strategies and tactics. The en

vironmentally-sound IPM approach will require much

more intensive management of resources and information.

Table 2 is a first step towards the organization of a variety

of information into a quantitative, objective outline in

which data can be collected, synthesized and applied for

successful decisionmaking.

Literature Cited

Baker, J. R. (ed.) 1980. Insect and related pests of shrubs. North Carolina

Dept. Agr. AG-189. 199 pp.

Butler, T. M., A. G. Hornsby, D. E. Short, R. A. Dunn, and G. W. Simone.

Pesticide management for ornamental crops. Fla. Nurseryman. 38:37-

47.

Dixon, W. N. 1987. Nantucket pine tip moth, Rhyacionia frustrana (Corn-

stock) (Lepidoptera: Tortricidae). Fla. Dept. Agric. & Cons. Serv. En-

tomol. Circ. No. 298.

Mead, F. W. 1972. The hawthorn lace bug, Corythuca cydoniae (Fitch), in

Florida (Hemiptera: Tingidae). Fla. Dept. Agric. & Cons. Serv. En-

tomol. Circ. No. 127.

Mead, F. W. 1975. The fringetree lace bug, Leptoypha mutica (Say)

(Hemiptera: Tingidae). Fla. Dept. Agric. & Cons. Serv. Entomol. Circ.

No. 161.

Mead, F. W. 1983. Yaupon psyllid, Gyropsylla ilicis (Ashmead) (Homopt-

era: Psyllidae). Fla. Dept. Agric. & Cons. Serv. Entomol. Circ. No. 247.

Mizell, R. F., Ill and D. E. Schiffhauer. 1987. Evaluation of insecticides

for control of Glyphidocera juniperella Adamski (Lepidoptera: Blas-

tobasidae: Symmocinae) in container-grown juniper. Fla. Entomol.

70:316-319.

Mizell, R. F. and D. E. Schiffhauer. 1988. Seasonal abundance of the

crapemyrtle aphid, Sarucallis kahawaluokalani (Kirkaldy) in relation to

the pecan aphids Monellia caryella (Fitch) and Monelliopsis pecanis (Bis-

sell) and their common predators. Entomophaga 32:511-20.

Mizell, R. F. and D. E. Schiffhauer. 1991. Biology and impact of the

azalea leafminer, Caloptilia azaleella (Brants), (Lepidoptera: Gracil-

lariidae) on nursery stock. Environ. Entomol. 20:597-602.

Schiffhauer, D. E. and R. F. Mizell, III. 1987. Bionomics of Glyphidocera

juniperella Adamski (Lepidoptera: Blastobasidae: Symmocinae), a

newly discovered pest of container-grown juniper. Fla. Entomol.

70:310-315.

Snow, J. W., T. Eichlin, and J. Tumlinson. 1985. Seasonal captures of

clearwing moths (Sesiidae) in traps baited with various formulations

of 3,13-octadecadienyl acetate and alcohol. J. Agr. Entomol. 2:73-84.

Sharpe, J. L., J. McLaughlin, J. James, T. Eichlin, and J. Tumlinson.

1978. Seasonal abundance of male Sesiidae in north central Florida

determined with pheromone trapping methods. Fla. Entomol. 61:245-

250.

Sharpe, J. and T. Eichlin. 1979. Distribution and seasonal occurrence of

Sesiidae (Lepidoptera) attracted to E,Z and Z,Z, acetate and alcohol.

In Neal, J. (ed.) Pheromones of the Sesiidae. U.S.D.A. SEA, ARS

ARR-NE-6. 83 pp.

Proc. Fla. State Hort. Soc. 105:210-212. 1992.

ABNORMAL STOMATA IN VITRIFIED PLANTS FORMED IN VITRO

Y. Mohamed-Yasseen, T. L. Davenport,

W. E. Splittstoesser1, and R. E. Litz

University of Florida, TREC,

18905 SW 280 St. Homestead, FL 33031

1 University of Illinois, Dept. of Horticulture,

1103 W. DornerDr., Urbana, IL 61801

Additional index words, leaf surface, stomata, Scanning elec

tron microscopy, micropropagation.

Florida Agricultural Experiment Station Journal Series No. N-00694.

210

Abstract. Vitrification is a physiological disorder which can be

a serious problem in plant micropropagation. Vitrified micro-

plants lose their ability to propagate and/or present difficul

ties of ex vitro acclimatization. Scanning electron microscopic

observations of leaf surfaces of vitrified and non-vitrified

shoots of soybean, chicory witloof, and carnation were con

ducted. Vitrified leaves had fewer stomata per unit area than

non-vitrified leaves. Distorted, occluded and closed stomata

were observed in vitrified leaves. Surface epidermal cells in

vitrified leaves were elongated and twisted. It is suggested

that modifications in stomata and leaf surfaces observed in

vitrified microplants reduce water loss through transpiration

leading to water accumulation in the lacunae and ultimately

to vitrification disorders.

Proc. Fla. State Hort. Soc. 105: 1992.

Vitrification is a serious problem in tissue culture (De-

bergh et al.} 1981; Ziv, 1991). Vitrified plants can not sur

vive transplanting to soil which seriously restricts the use

of long term propagation for industrial production

(Navatel, 1982). Vitrification is also termed translucency,

hyperhydration, hyperhydric transformation, glauciness,

waterlogging, glassiness (Paques and Boxus, 1987). Several

hypothesis were offered such as an increase in ammonium

concentration, (Riffaud and Cornu, 1981; Vieitez et al.,

1985), high concentrations of cytokinins (Debergh, 1983),

calcium deficiency (Kreutmeier et al., 1984), and a

superoptimal concentration of potassium (Quoirin and

Lepoivre, 1977) have been suggested as causes of vitrifica

tion. We have observed that soybean shoots cultured in

half strength Murashige and Skoog (1962) medium (MS)

supplemented with additional potassium salt (KNO3)

formed translucent leaves while those cultured in the same

medium without additional supplement were normal

(Mohamed-Yasseen, unpublished). Addition of activated

charcoal provokes vitrification in some plants (Densco,

1987; Mohamed-Yasseen, unpublished).

Debergh et al. (1981) and Debergh and Maene (1985)

demonstrated that vitrification rate was always higher in

liquid than in solid media, and it decreased as the relative

humidity in tissue culture container was reduced. Increas

ing the water potential by reducing the concentration of

gelling agent induced vitrification (Debergh, 1983; Zim

merman and Cobb, 1990). Leaves and chiefly stomata, are

responsible for water regulation in plants through evap

oration and transpiration. Observation of stomata in vit

rified plants was needed to investigate for possible correla

tions between stomatal structure and vitrification. In this

report, leaf surface of normal and vitrified plants were

examined under scanning electron microscopy.

Materials and Methods

Leaves of normal and vitrified microplants were ex

cised from cultures of carnation (Dianthus chinensis L.), soy

bean (Glycine max L. Merr), and chicory witloof (Cichorium

-• * *.- T.

Figure 1. Stomata of normal soybean leaf.

Proc. Fla. State Hort. Soc. 105: 1992.

Figure 2. Abnormal stomata observed in vitrified leaves. (A) Closed

stomata in soybean leaf. (B) distorted stomata in chicory widoof. (C)

occluded stomata in carnation leaf.

211

intybus L.). Shoot tips of carnation were surface sterilized

with 70% ethanol for one minute, 0.3% (v/v) NaCIO for

ten minutes, rinsed three times in sterile distilled water.

Carnation shoot tips were then cultured in Murashige and

Skoog (1962) medium (MS) supplemented with 30 g/1 suc

rose, 8 g/1 (Bacto-agar, Difco), 30 g/1 sucrose, 0.15 uM

thidiazuron, and 0.05 uM a-naphthaleneacetic acid. The

pH of all media were adjusted to 5.7 after adding growth

regulators with IN KOH. Growth regulators were added

before autodaving. Soybean and chicory witloof micro-

plants were regenerated from cotyledonary nodes and leaf

discs respectively. Methodology of regeneration and cul

ture conditions for soybean and chicory witloof were al

ready described (Mohamed-Yasseen and Splittstoesser,

1990, 1991a). All cultures were incubated in a growth

room providing 18 h photoperiod (cool white fluorescent

light, 40 tunohm-Z'S-1) and 28°C. Leaves from vitrified and

normal shoots from carnation, soybean and witloof chicory

were fixed in 4% glutaraldhyde, and prepared for scan

ning electron microscopy (SEM) observation by conven

tional methods and examined using a JEOL U3 SEM,

(Mohamed-Yasseen and Splittstoesser, 1990b). In some in

stances, samples were cryofixed in propane pre-cooled by

liquid nitrogen, and observed using an AMRAY 1000A

SEM (Mohamed-Yasseen and Splittstoesser, 1990c).

Results and Discussion

Leaf surfaces of vitrified shoots were anatomically dif

ferent from normal leaves. Normal leaves have open

stomata (Fig. 1). Closed (Fig. 2A), distorted (Fig. 2B), and

occluded stomata (Fig. 2C), were observed in vitrified

leaves. Vitrified leaves had fewer stomata per unit area

than non-vitrified leaves. Epidermal cells in vitrified leaves

were elongated and leaves were wrinkled. Stomata of vit

rified leaves were recessed or elevated which may be

caused by wrinkled leaf surface. Vitrified soybean leaves

had more epicuticular waxes than normal leaves (Fig. 2A).

However, no difference in epicuticular waxes were noted

between normal and vitrified leaves of carnation or witloof

chicory. Closed and abnormal stomata in vitrified micro-

plants were noted in carnation (Diathus caryophllus) and

melon (Werker and Lesham, 1987; Lesham et al., 1988).

However, there is no available information on the relation

ship between abnormal leave surface, notably stomata, and

vitrification and processes which cause a decrease in water

loss or increased water uptake, induce vitrification (Ziv,

1991). Removal of leaves from microplants was reported

to cause vitrification, and was not related to ethylene pro

duction (De Profit et al., 1987). Similar results were ob

served in some Allium spp. when injuring stem base of

seedlings to increase water uptake together with decreas

ing water loss by removal of a portion of their leaves.

Moreover, excessive injury of explants during surface

sterilization by NaCIO with detergent also induce vitrifica

tion (Mohamed-Yasseen, unpublished). Leaves of normal

microplants have open stomata which were shown to be

functioning (Shackel et al., 1990). In this report, closed,

and distorted stomata, fewer number of stomata, and

wrinkled leaves were observed in vitrified leaves of carna

tion, soybean and witloof chicory. Vitrified leaves of Zinnia

elegans, and Solanum nigrum showed similar results

(Mohamed-Yasseen and Splittstoesser, 1992). It is possible

that vitrification is associated with abnormal structure of

stomata and leaf surface, such modification are supposed

to cause leaves to be inefficient in water regulation, mainly

through transpiration, which lead to water accumulation

in leaves lacunae, causing vitrification disorder.

Literature Cited

De Proft, M. G., G. Van Broeik, and J. A. De Greef. 1985. Involvement

of ethylene on senescence and vitrification of in vitro cultured mini

roses. Acta Hort. 212:217-222.

Debergh, P. C. 1983. Effects of agar brand and concentration on the

tissue culture medium. Physiol. Plant. 59:270-276.

Debergh, P. C. and L. J. Maene. 1985. Preparation of tissue cultured

plants for rooting and establishment in vitro, p. 487-495. In F. J.

Novak, T. Havel, and K. Dolzel (eds.). Proc. Intl. Symp. Plant tissue

and cell culture application to crop improvement. Olomouc, Czechos

lovakia.

Debergh, P. C., Y., Harbaoui, and R. Lemeur. 1981. Mass propagation

of globe artichoke (Cynara scolymus): evaluation of different hypothesis

to overcome vitrification with special reference to water potential.

Physiol. Plant. 53:181-187.

Dencso, I. 1987. Factors influencing vitrification of carnation and conif

ers. Acta Hort. 212:167-176.

Kreutmeier, C., K. Gebhardt, L. Paul, and W. Feucht. 1984. The effect

of MgSO4 and CaCl2 on regeneration of shoot tip cultures of Prunus

cerasus in vitro. Garterbouwissenschaft. 49:205-212.

Lesham, B., E. Werker, and D. P. Shalev. 1988. The effect of cytokinins

on vitrification in melon and carnation. Ann. Bot. 62:271-276.

Mohamed-Yasseen, Y. and W. E. Splittstoesser. 1990. Regeneration of

soybean (Glycine max (L.) Merr.) from the seedling apex, stem node,

cotyledonary node and cotyledons. Plant Growth Regul. Soc. Amer.

18:203-210.

Mohamed-Yasseen, Y. and W. E. Splittstoesser. 1991a. Plant regeneration

from stored witloof chicory (Cichorium intybus L.). Plant Growth Regul.

Soc. Amer. 19:41-45.

Mohamed-Yasseen, Y. and W. E. Splittstoesser. 1991b. Scanning electron

microscope for the study of onion seed quality. Proc. Illinois State

Hort. Soc. 124:103-104.

Mohamed-Yasseen, Y., B. Jakstys, and W. E. Splittstoesser. 1991c.

Methods of onion (Allium cepa L.) seed preparation for scanning elec

tron microscope studies of seed coat. J. Electron Microscopy Tech

nique 18:207-208.

Mohamed-Yasseen, Y. and W. E. Splittstoesser. 1992. Scanning electron

microscopic observation of vitrified and normal leaves of microplants.

HortScience (in press).

Murashige, T. and F. Skoog. 1962. A revised medium for rapid growth

and bioassay with tobacco tissue cultures. Physiol. Plant. 15:473-497.

Navatel, J. C. 1982. Problems lies a la production de porte-greffe d'arbres

fruitiers par multiplication in vitro. Fruits 37:331-336.

Paqucs, M. and Ph. Boxus. 1987. "Vitrification": Review of literature.

Acta Hort. 212:155-166.

Quoirin, M. and P. Lepoivre. 1977. Etude de milieux adaptes aux cultures

in vitro de Prunus. Acta Hort. 78:437-442.

Riffaud, I. L. and D. Cornu. 1981. Utilization de la culture in vitro pour

le multiplication de merisiers adultes (Prunus avium L.) selectionnes en

foret. Agronomic 1:633-640.

Shackel, K. A., V. Novello, and G. Sutter. 1990. Stomatal function and

cuticular conductance in whole tissue-cultured apple shoots. J. Amer.

Hort. Soc. 115:468-472.

Vieitez, A. M., A. Ballester, M. C. San-Jose, and E. Vieitez. 1985. Anatom

ical and chemical studies of vitrified shoots of chestnut regenerated

in vitro. Physiol. Plant. 61:483-489.

Werker, E. and B. Leshem. 1987. Structural changes during vitrification

of carnation plan tie ts. Ann. Bot. 59:377-385.

Zimmerman, T. W. and B. G. Cobb. 1990. Vitrification and soluble

carhohydrate levels in Petunia leaves as influenced by media Gerlite

and sucrose concentrations. Plant Cell Rpt. 8:358-360.

Ziv, M. 1991. Vitrification: morphological and physiological disorders of

in vitro plants, p. 71-93. In: P. C. Debergh and R. H. Zimmerman

(eds.) Micropropagation technology and application. Klauwer

Academic publishers. Dordrecht. The Netherlands.

212 Proc. Fla. State Hort. Soc. 105: 1992.