Group Title: ARC-A research report - Agricultural Research Center-Apopka ; RH-81-2
Title: Some diseases of Pittosporum tobira (Thunb.) Ait.
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Permanent Link: http://ufdc.ufl.edu/UF00065943/00001
 Material Information
Title: Some diseases of Pittosporum tobira (Thunb.) Ait.
Series Title: ARC-A research report
Physical Description: 4 leaves : ; 28 cm.
Language: English
Creator: Chase, A. R ( Ann Renee )
Agricultural Research Center (Apopka, Fla.)
Publisher: IFAS, University of Florida, Agricultural Research Center-Apopka
Place of Publication: Apopka Fla
Publication Date: 1981
 Subjects
Subject: Pittosporum -- Diseases and pests -- Florida   ( lcsh )
Leaf spots -- Florida   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
bibliography   ( marcgt )
non-fiction   ( marcgt )
 Notes
Bibliography: Includes bibliographical references.
Statement of Responsibility: A.R. Chase.
General Note: Caption title.
 Record Information
Bibliographic ID: UF00065943
Volume ID: VID00001
Source Institution: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: oclc - 70912921

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SOME DISEASES OF PITTOSPORUM TOBIRA (THUNB;)-A1-T,

A. R. Chase '
IFAS University of Florida
Agricultural Research Center-Apopka .
ARC-A Research Report RH-81-2
.S. Univ. of Flor~;-
Pittosporum tobira (Thunb.) Ait. (Japanese Pittosporum) and P. __FTra-

Ait. cv. Variegata are grown in Florida as outdoor landscape plants as well as

for production in the cut foliage market. Pittosporum tolerate full sun and
freezing temperatures. Plantingsof pittosporum are relatively carefree, although
in some locations they may be subject to pests and diseases attacking roots, stems
and leaves. The following discussion is concerned with three groups of diseases

of pittosporum based on symptomatology: A) leafspots, B) stem galls and diebacks,
and C) root rots.

A. Leafspots
There are several fungal organisms causing leafspots of pittosporum.
Angular leafspot caused by Cercospora pittospori Plak. was first described in

1940 by Plakidas (4), and is common in field plantings of pittosporum not

routinely sprayed for its control and in the landscape (6). Symptoms of angular
leafspot are light yellow to pale green and tan angular spots developing on

upper leaf surfaces. Leafspots are angular due to expansion between leaf veins

and commonly have an indistinct margin. The spot pattern is similar on leaf
undersides. Severe infections of immature leaves may result in leaf distortion.
The key to recognition of this leafspot is the characteristic angular shape.

Another leafspot of pittosporum is caused by Alternaria tenuissima (Fr.)
Wiltsh. This disease was first noted by Sobers in early 1960's (7,8)'who
established the pathogenic role of A. tenuissima in that leafspot. Early
stages of Alternaria leafspot resemble angular leafspots. However, as lesions











develop, they become distinctly different. Irregular chlorotic spots are

scattered over the leaf surface, later developing necrotic centers absent

in angular leafspot. Spots are typically rounded, have tan to dark brown

centers, and generally are smaller than those caused by Cercospora sp.

Many of the lesions are surrounded by a yellow halo and their centers are

slightly depressed. Symptoms on immature leaves may result again in

distortion giving leaves a crinkled appearance. This disease is not as

commonly found as angular leafspot in the field (although it is common in

nurseries) and is generally less damaging to a planting. Control measures

can be the same for both diseases. Basic copper can be used to control both

leafspots when sprayed two or three times at 7-10 day intervals (2). BenlateD

benomyll) can be used also for control of angular leafspot but not for control'

of Alternaria leafspot since it has no activity against the fungus.

The most severe leafspot of pittosporum is caused by Rhizoctonia ramicola

Weber & Roberts reported in 1951 (10). In many cases this disease may more

accurately be referred to as a blight and has been commonly named silky

threadblight. Silky threadblight is characterized by small, tan, irregularly

shaped spots, generally surrounded by purplish margins, Spots frequently reach

1 cm in diameter and can encompass the entire leaf. R. ramicola inhabits the

soil and thus creates spots on lower leaves initially and extends into upper

portions of plants when conditions are favorable, In severe cases leaves curl

into a cylinder and become matted by the threadlike growth of the fungus, thus

the common name silky threadblight. Recommended control methods include

sanitation and one or more summer applications of Terraclor-(PCNB) at the

rate of 2 g/liter (3).

A new leafspot disease of P. tenuifolium has been described by Archer in

Europe (1) but has not been noted in Florida as yet. Symptoms of this leafspot,











cutting instruments or by passive spore movements. Galls often girdle stems

resulting in twig death. Pruning infected areas carefully can eliminate

spread to adjacent tissues and is a recommended control (2).

C. Root rots

Root rot of pittosporum is caused by Pythium spp. and Rhizoctonia spp.

(2). Although no papers supporting the role of these organisms as pathogens

of pittosporum are available, they are readily isolated from rotting roots.

Root rot is most severe when plants are grown in wet, poorly drained soil.

Declining plants may lose their leaves suddenly or over a long period of time

beginning at the base of the plants. Leaves may also appear chlorotic as the

roots are unable to extract nutrients from the soil. Root examination often

reveals black and/or soggy roots. Pythium root rot generally is typified by

a sloughing off of outer root layers leaving the central core intact. In both

root rots small feeder roots are usually absent from severely infected areas

of the roots. Careful water management in planting sites is a valuable aid in

controlling these rots. Drenches with Benlate@ or LesanO (fenaminosulf)

have been recommended for treatment of young plants as a preventative treatment

(2).










Literature Cited

1. Archer, S. A. 1973. Phomopsis pittospori sp. nov., associated with

leafspotting of Pittosporum tenuifolium. Trans. Brit. Mycol. Soc.

61(2):221-225.

2. Kucharek, T., G. W. Simone, and R. S. Mullin. 1978. Florida Plant

Disease Control Guide. IFAS, Fla. Coop. Ext. Serv., Univ. of Fla.

3. Martinez, A. P. 1967. Silky threadblight of Pittosporum. Fla. Dept.

of Agric., Div. of P1. Ind., P1. Path. Circ. No. 60.

4. Plakidas, A. B. 1940. Angular leafspot of Pittosporum. Mycologia

32:601-608.

5. Rana, G. L., and A. Di Franco. 1980. Isolation of two rhabdoviruses

from Pittosproum and Pelargonium. Acta Horticulturae 110:191-193.

6. Sobers, E. K. 1962. Angular leafspot of Pittosporum Cercospora

pittospori Plak. Fla. Dept. of Agr., Div. of P1. Ind., P1. Path Circ.

No. 4.

7. Sobers, E. K. 1962. Alternaria leafspot of Pittosporum tobira Ait. -

.(Alternaria sp.). Fla. Dept. of Agr., Div. of P1. Ind., P1. Path.

Circ. No. 5.

8. Sobers, E. K. 1964. Alternaria leafspot of Pittosproum. Phytopathology

54:478-480.

9. Thomas, H. Earl, and Kenneth F. Baker. 1947. A rough-bark disease of

Pittosporum tobira. Phytopathology 37:192-194.

10. Weber, G. F., and D. A. Roberts. 1951. Silky threadblight of Elaeagnus

pungens caused by Rhizoctonia ramicola n. sp. Phytopathology 41:615-621.




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