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Diseases of Holiday Cacti: Schlumbergera and Hatiora

  • Robert L. Wick
Living reference work entry
Part of the Handbook of Plant Disease Management book series (HPDM)

Abstract

The most important diseases of Schlumbergera truncata, the Thanksgiving cactus, are Fusarium basal stem rot, Phytophthora root and stem rot, Bipolaris blight, and bacterial soft rot. Impatiens necrotic spot virus (INSV) and tomato spotted wilt virus (TSWV) are a problem because infected plants cannot be sold. Hatiora gaertneri (Regel) Barthlott, the Easter cactus is relatively free of important diseases except for Fusarium stem rot which is very destructive to Hatiora.

Keywords

Fusarium oxysporum Bipolaris cactivora Phytophthora nicotianae Pectobacterium carotovora Pythium INSV TSWV 

1 Introduction

Schlumbergera truncata (Haworth) Moran, Thanksgiving cactus (also called Christmas cactus ), is the most common Schlumbergera species under cultivation (Boyle 2007). The interspecific hybrid S. x buckleyi (Buckley) Tjaden (= S. russelliana x S. truncata) blooms a month later and is commonly called the Christmas cactus (Boyle 2007; Daughtrey et al. 1995). Schlumbergera truncata was formerly Zygocactus truncatus (Haw.) K. Schum. Members of the Cactaceae are native to Brazil; they are widely cultivated as a flowering potted plant along with Hatiora gaertneri (Regel) Barthlott, the Easter cactus. Hatiora gaertneri was previously known as Rhipsalidopsis gaertneri (Regel) Moran.

2 Fungal and Fungus-Like Diseases

2.1 Basal Stem and Root Rot [(Fusarium oxysporum Schlecht); (Fusarium oxysporum f. sp. opuntiarum)]

Geographic Occurrence and Impact

Fusarium basal stem and root rot of S. truncata was first reported in a proceedings in 1975 (Miller 1975) and formally published in 1980 (Moorman and Klemmer 1980). It has been reported in the USA, Argentina (Petrone et al. 2007), Italy (Lops et al. 2013), the Netherlands (Baayen et al. 2000), and Germany (Baayen et al. 2000; Gerlach 1972). Inoculation trials with F. oxysporum isolated from S. truncata failed to cause disease on H. gaertneri (Chase 1982). However subsequent research showed that an F. oxysporum isolated from S. truncata caused stem and root rot on several cultivars of H. gaertneri similar in extent to several cultivars of S. truncata (Mitchell 1987). Nevertheless there is a paucity of information regarding the occurrence of F. oxysporum root and stem rot on H. gaertneri. Fusarium oxysporum f. sp. opuntiarum was described from Schlumbergera in Germany in 1972. Subsequent reports of F. oxysporum on cactus did not include the f. sp. opuntiarum epithet; however, it is not known if F. oxysporum cited in the USA and Argentina is different or the same as F. oxysporum f. sp. opuntiarum reported in Europe. Fusarium basal stem and root rot is one of the most destructive diseases of Schlumbergera.

Symptoms/Signs

The disease can manifest itself as a root rot, basal stem rot, and cladophyll lesion. Basal rot can occur on wounded or unwounded stems and is at first water soaked in appearance with reddish-brown margins. As the lesion ages, the tissue may dry to a papery tan (Moorman and Klemmer 1980). Lesions on wounded inoculated cladophylls of S. truncata can become up to 50 mm in diameter in 10 days (Chase and Yuen 1993). Lesions on inoculated H. gaertneri cladophylls ranged from about 5 to 20 mm in diameter.

Biology and Epidemiology

F. oxysporum is the most widely dispersed of Fusarium spp. and occurs throughout the world in many types of soils, mostly as a soil saprophyte (Domsch et al. 1980; Leslie and Summerell 2006). A true soil-borne fungus survives in the soil by producing resting structures, chlamydospores, and active growth. Since Hatiora and Schlumbergera a re vegetatively propagated, the widespread occurrence of F. oxysporum on cactus is probably due to movement of infected plant material and infested soil. Fusarium oxysporum i s best known for the destructive nature of the vascular wilt diseases it causes on a wide variety of crops (Agrios 2005); more than 100 forma speciales and races have been described, most of which have a very narrow host range, often restricted to a single plant species or cultivar. While the descriptions of F. oxysporum disease of cactus often include wilt, wilt is apparently due to root rot and basal stem canker as opposed to vascular wilt. No one has demonstrated that F. oxysporum is a vascular pathogen of Schlumbergera.

Management

  • Cultural Practices – New plants coming into the greenhouse should be carefully inspected for root rot, basal canker, and lesions on cladophylls. Diseased plants and plant debris should be removed from the presence of healthy plants. When growing plants in soil-less media, take care not to introduce field soil by hands, tools, and hose ends dropped on the floor. If the growing medium contains field soil, it must be pasteurized. Air drying of excised cladophylls up to 72 h before propagation did not prevent Fusarium from infecting (Mitchell 1987). With other Fusarium diseases, the application of nitrate as opposed to ammonium forms of nitrogen can suppress Fusarium. In addition, acid soils <6.0 can increase Fusarium disease severity so properly limed potting mixes may reduce disease severity.

  • Resistance – Schlumbergera truncata cvs. Gold Charm, Christmas Flame, and Cambridge were found to be very susceptible to Fusarium (Chase and Yuen 1993). In a separate trial, cvs. Gold Charm and Norris were found to be the most susceptible (Mitchell 1987). Significant resistance to Fusarium was not found in either of the abovementioned trials.

  • Chemical Control – Chlorothalonil dips and drenches provided good control of Fusarium basal rot but inhibited root growth. High rates of a combination of mancozeb and thiophanate-methyl were phytotoxic, but benomyl provided complete control (Mitchell 1987).

2.2 Bipolaris Blight Bipolaris cactivora (Petr.) Alcorn.; Previously Drechslera cactivora (Petr.) M. B. Ellis and Helminthosporium cactivorum Petr.

Bipolaris blight is also known as top rot, stem rot, and shattering

Geographic Occurrence and Impact

It has been reported in the USA and Europe (Daughtrey et al. 1995), probably more widely distributed. Schlumbergera is only moderately susceptible to this disease; younger plants are more susceptible than older ones. Most cultivars of Hatiora gaertneri are very susceptible to Bipolaris cactivora.

Symptoms/Signs

Bipolaris cactivora causes roughly circular dark sunken lesions on cladophylls (Figs. 1 and 2). Cladophylls become soft rotted and abscise from the plant. A dark-brown, felty growth of spores may develop on the surface of the infected tissue.
Fig. 1

Bipolaris blight (R. L. Wick)

Fig. 2

Bipolaris blight (R. L. Wick)

Biology and Epidemiology

In 1955, approximately 60 species of cacti were known to be susceptible to “top rot” by Bipolaris cactivora (Durbin et al. 1955). Natural infection of Schlumbergera truncata by B. cactivora was first reported in California, USA (Raabe 1989). Prior to that, inoculations of Schlumbergera with B. cactivora isolates from Hatiora were largely unsuccessful (Chase 1982). Abundant conidia are produced on the surface of the lesions where they may be dislodged by wind or water. Wounding is not necessary for infection, and infection can take place on any of the cladophylls including those below the ground.

Management

  • Cultural Practices – Infected plants should be discarded. Keep relative humidity low and reduce plant wetness duration. A novel approach to controlling this disease on other cacti utilized heat-inactivated conidial suspension of B. cactivora. Conidial suspensions were autoclaved, and when applied 2 days prior to inoculation with the pathogen, plants had no or minimal disease development (Choi et al. 2010). The treatment greatly increased wound periderm formation at the site of inoculation.

  • Resistance – At the University of Massachusetts, a diverse array of 19 Hatiora genotypes were challenged by B. cactivora in growth chambers and in the greenhouse. In all three experiments, Hatiora x graeseri ‘Hatherton Star’ exhibited excellent resistance. H. salicornioides ‘Logee’ was also resistant. Resistance was displayed as small lesions with little or no sporulation; susceptible plants had large lesions with abundant spores (Boyle 2007 and Table 1).

  • Chemical Control Chlorothalonil has been used to control this disease (Daughtrey et al. 1995).

Table 1

Disease reactions of Hatiora species and cultivars to an isolate of Bipolaris cactivora (T. H. Boyle and R. L. Wick, unpublished data)

Disease reaction

Entry

Highly susceptible

Annika, Cassiopeia, Crimson Giant, Crystal Lakes 32, Evita, Flash, Leo’s Pink, Pink Perfection, Rainbow, Rood, Shocking Pink, Sutter’s Gold, Thor-Anne, H. rosea MD861

Moderately susceptible

Andre

Resistant

Hatherton Star, H. salicornioides Logee

2.3 Pythium Root and Stem Rot [Pythium aphanidermatum (Edson) Fitzp. Pythium irregulare Buisman, and Pythium cryptoirregulare Garzon, Yanez, and Moorman]

Geographic Occurrence and Impact

The three Pythium species listed above have been reported on Schlumbergera (Knauss 1975; Garzon et al. 2007; Lee et al. 2010), and Pythium root and stem rot has been reported in Denmark and Florida, USA; however, it is presumed that many Pythium spp. are capable of causing root and stem rot, and the diseases occur worldwide. Pythium is one of the most common causes of root rot in greenhouses (Daughtrey et al. 1995).

Symptoms/Signs

Pythium spp. cause feeder roots to become brown and soft rotted. Usually the cortex easily separates from the vascular system. Root rot causes wilting of the plant. Occasionally a crown rot occurs and Pythium spp. can move up the stem for some distance.

Biology and Epidemiology

Pythium is a widespread and common genus of the Oomycota (water molds) (Daughtrey et al. 1995); nearly every handful of soil contains one or several species. Pythium spp. are not usually an aggressive plant pathogen unless plants are growing in a soil-less medium, soluble salts are high and moisture abundant. There are more than 200 species of Pythium; they generally have a wide host range and vary in their pathogenicity and distribution. Pythium species are not strong soil competitors but can survive in soil for long periods of time via oospores. When soil moisture is abundant, root exudates cause oospores to germinate and produce a sporangium where 10–30 zoospores develop. The zoospores find roots by chemotaxis and they have flagella that propel them through the water. Once on the root surface, they infect, colonize, and kill the root cells and produce oospores and sporangia. Young roots and seedlings are particularly susceptible to infection. Fungus gnats can also spread the pathogen.

Management

  • Cultural Practices Remove diseased plants from the greenhouse being careful not to spill the soil from the pots. When growing plants in soil-less media, take care not to introduce field soil by hands, tools, and hose ends dropped on the floor. Use a well-drained growing medium and avoid overwatering and overfertilization.

  • Chemical Control Many modern fungicides have single-site mode of action and readily select for resistance. To avoid resistance development, rotate between different Fungicide Resistance Action Committee groups (FRAC Code List 2015); do not use one fungicide repeatedly. Note that some isolates of Pythium and Phytophthora may already be resistant to some of these fungicides. Many greenhouse isolates of Pythium in the USA have developed resistance to mefenoxam. The fungicides listed here are followed by the FRAC code in parentheses followed by the risk of selecting for resistance. Mefenoxam (4) high, etridiazole (14) low to medium, azoxystrobin (11) high, fluopicolide (43) unknown, fosetyl-Al (33) low, fenamidone (11) high, and Cyazofamid (21) medium to high.

2.4 Phytophthora Root and Stem Rot Phytophthora nicotianae Breda de Haan; Formerly Phytophthora parasitica Dastur.

Geographic Occurrence and Impact

Phytophthora nicotianae causes many important plant diseases worldwide. Phytophthora nicotianae is very destructive to Schlumbergera truncata (Alfieri and Miller 1971). It is likely that other species of Phytophthora can cause root and stem rot of Schlumbergera .

Symptoms/Signs

Plants collapse and may show brown lesions at the base of the plant (Fig. 3).
Fig. 3

Phytophthora root and stem rot (R. L. Wick)

Biology and Epidemiology

Phytophthora nicotianae was considered more or less synonymous with Phytophthora parasitica following the combining of the two taxa by Waterhouse in 1963, although the use of P. parasitica rather than P. nicotianae became preferred over time. Indeed from 1970 to 1994, citations listed P. parasitica much more commonly than those listing P. nicotianae (Erin and Ribeiro 1996). Currently P. nicotianae is the accepted name. Phytophthora nicotianae has the widest host range of any Phytophthora species and is found all over the world. Phytophthora is not as common in greenhouses as Pythium, but it is much more aggressive than Pythium. There are more than 80 species of Phytophthora and most have wide host ranges. Like Pythium, Phytophthora is an Oomycete and is most active when water is plentiful in the growing medium. Dispersal of inoculum is dependent on movement of contaminated water, soil, or plant material. Nearly all species produce oospores but some need opposite mating types to do so, and some produce resting structures called chlamydospores. Phytophthora is a soil-borne organism and can survive for many years in the absence of a host. Oospores are stimulated to germinate when root exudates are present, and germination often results in the formation of sporangia with swimming zoospores. Temperatures of 28° C/82° F C and above favor disease development (Daughtrey et al. 1995).

Management

  • Cultural Practices Remove diseased plants from the greenhouse being careful not to spill the soil from the pots. When growing plants in soil-less media, take care not to introduce field soil by hands, tools, and hose ends dropped on the floor. Use a well-drained growing medium and avoid overwatering and overfertilization.

  • Chemical Control Many modern fungicides have single-site mode of action and readily select for resistance. To avoid resistance development, rotate between different FRAC groups (FRAC Code List 2015); do not use one fungicide repeatedly. Note that some isolates of Pythium and Phytophthora may already be resistant to some of these fungicides. Many greenhouse isolates of Pythium in the USA have developed resistance to mefenoxam. The fungicides listed here are followed by the FRAC code in parentheses followed by the risk of selecting for resistance. Cyazofamid (21) medium to high, fenamidone (11) high, mefenoxam (4) high, phosphorous acid salt (no FRAC Code) low, and pyraclostrobin (11) high.

2.5 Other Minor Diseases Caused by Fungi

Note, these diseases may be minor in importance or, they are rare in their occurrence.

Geographic Occurrence and Impact

The following fungi are listed in various indices and reports as occurring on Schlumbergera truncata: Alternaria sp., anthracnoses (Colletotrichum spp.), Armillaria root rot, Cercospora leaf spot, Dichotomophthora sp. tip blight, Fusarium spp. basal stem rot, leaf spot, Myrothecium leaf spot and crown rot, and Phomopsis sp. leaf spot (Daughtrey et al. 1995; Wick and Dicklow 1999).

3 Bacterial Diseases

3.1 Bacterial Soft Rot [Pectobacterium carotovorum subsp. carotovorum (Jones) Hauben et al. emend. Gardan et al.)]. Formerly Erwinia carotovora subsp. carotovora

Geographic Occurrence and Impact

Pectobacterium has a worldwide distribution and a wide host range. Bacterial soft rot is not a major problem, but it can be destructive and persistent if not controlled completely.

Symptoms/Signs

Soft rot generally starts at the soil line where it causes a soft mushy rot.

Biology and Epidemiology

Pectobacterium produces pectic enzymes which are responsible for soft rot. The bacterium can survive in soil and may contact plants from dirty hands and tools, splashing water, insects, or hose ends that have contacted the ground. Pectobacterium may also come in on cuttings from infected mother plants. Bacteria need wounds or natural openings to gain entry into the host; cut cladophylls that are rooting would be particularly susceptible. In general, plants propagated vegetatively are very vulnerable to infection by soft rot bacteria, especially at high temperatures which are often provided by heating mats to encourage rooting. Pectobacterium carotovorum subsp. carotovorum has an optimum temperature for growth of 28–30 ° C/82–86° F but can grow up to 37–42 ° C/98–108° F (Daughtrey et al. 1995).

Management

  • Cultural Practices – Before propagation, the cutting bench area should be clean and disinfested. Plants or rooting cladophylls with evidence of soft rot should be discarded. If soft rotting occurs in the propagation area, discard all plant material, and thoroughly disinfest all surfaces with a quaternary ammonium compound or similar product (Daughtrey et al. 1995).

  • Chemical Control – Various formulations of copper can afford some protection against bacteria but are not likely to prevent basal rots that initiate below the surface of the growing medium.

4 Virus Diseases

4.1 Tomato Spotted Wilt Virus (TSWV) and Impatiens Necrotic Spot Virus (INSV)

Geographic Occurrence and Impact

TSWV and INSV have become distributed worldwide and are known to occur in the USA, South America, Canada, Europe, India, China, and Japan. Reports on Schlumbergera include the USA, Canada, Finland, and Europe, but these viruses are probably more widespread. While not destructive on Schlumbergera, TSWV and INSV are of economic importance as infected plants would be discarded.

Symptoms/Signs

TSWV/INSV cause a variety of symptoms on Schlumbergera including sunken chlorotic lesions, dark-green spots, chlorosis, ring spots, and necrosis (Figs. 4 and 5). Infected plants can be non-symptomatic as well (Hausbeck and Fildow 1991).
Fig. 4

INSV (R. L. Wick)

Fig. 5

INSV (R. L. Wick)

Biology and Epidemiology

TSWV/INSV are Tospoviruses in the family Bunyaviridae. Prior to 1990, TSWV was considered to have two strains, TSWV I (impatiens strain) and TSWV L (lettuce strain). In 1990, INSV was described as distinct from TSWV; however, prior to this time, plants showing symptoms of TSWV may in fact have been infected by INSV. At least in the USA, ornamental plants are far more likely to be infected by INSV than TSWV, and the symptoms can be similar (Daughtrey et al. 1995). Antisera are available to distinguish the two viruses. Tospoviruses are vectored exclusively by at least seven species of thrips (Thysanoptera: Thripidae). Only the first and early second instar larvae can acquire the virus, and both the larvae and adults can transmit the virus. The virus/thrip relationship is persistent and INSW and TSWV can replicate in the vector.

Management

  • Cultural Practices Inspect plants for viruses before introducing them into the greenhouse. Schlumbergera can be asymptomatic carriers of the virus so it would be wise to have random testing carried out on newly acquired plants. Control weeds on the greenhouse floor and around the greenhouse. Monitor for thrips with yellow sticky cards. Screening can be used to cover greenhouse vents, but the material should have apertures of 135 microns or less; this will exclude thrips but can greatly reduce airflow into the greenhouse. Avoid carrying over crop material from season to season.

  • Chemical Control Insecticides should be used to control thrips; however, many thrips have developed resistance to one or more insecticides.

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Copyright information

© Springer International Publishing AG (outside the USA) 2017

Authors and Affiliations

  1. 1.Stockbridge School of AgricultureUniversity of MassachusettsAmherstUSA

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