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Plantwise Technical Factsheet

bacterial blight of endive (Pseudomonas cichorii)

Host plants / species affected
Abelmoschus esculentus (okra)
Allium sativum (garlic)
Apium graveolens (celery)
Arracacia xanthorrhiza (arracacha)
Barleria cristata (Philippine violet)
Borago officinalis (Borage)
Brassica napus var. napus (rape)
Brassica oleracea var. botrytis (cauliflower)
Brassica oleracea var. capitata (cabbage)
Brassica rapa subsp. chinensis (Chinese cabbage)
Brassica rapa subsp. oleifera (turnip rape)
Brassica rapa subsp. pekinensis
Calendula officinalis (Pot marigold)
Capsicum (peppers)
Capsicum annuum (bell pepper)
Carthamus tinctorius (safflower)
Centaurea cyanus (cornflower)
Chrysanthemum (daisy)
Chrysanthemum coronarium (garland chrysanthemum)
Chrysanthemum morifolium (chrysanthemum (florists'))
Chrysanthemum vestitum
Cichorium endivia (endives)
Cichorium endivia subsp. endivia (endives)
Cichorium endivia var. crispum (Winter endive)
Cichorium intybus (chicory)
Citrullus lanatus (watermelon)
Coffea arabica (arabica coffee)
Coreopsis lanceolata
Cucumis sativus (cucumber)
Cucurbita pepo (marrow)
Daucus carota (carrot)
Duranta erecta (golden dewdrop)
Ficus lyrata (fiddle-leaf fig)
Gerbera (Barbeton daisy)
Gerbera jamesonii (African daisy)
Glycine max (soyabean)
Hedera helix (ivy)
Helianthus (sunflower)
Hibiscus rosa-sinensis (China-rose)
Hydrangea (hydrangeas)
Lactuca sativa (lettuce)
Luffa aegyptiaca (loofah)
Magnolia grandiflora (Southern magnolia)
Malus domestica (apple)
Mentha arvensis (Corn mint)
Monstera deliciosa (ceriman)
Musa (banana)
Nicotiana tabacum (tobacco)
Ocimum basilicum (basil)
Panax ginseng (Asiatic ginseng)
Papaver nudicaule (Iceland poppy)
Papaver orientale (Oriental poppy)
Pelargonium (pelargoniums)
Pernettya mucronata (prickly heath (UK))
Phaseolus vulgaris (common bean)
Phlox paniculata (summer perennial phlox)
Plumeria pudica
Potentilla (Cinquefoil)
Primula polyantha
Prunus persica (peach)
Pyracantha (Firethorn)
Pyrus communis (European pear)
Ranunculus acris (Meadow buttercup)
Rhododendron catawbiense
Solanum lycopersicum (tomato)
Solanum melongena (aubergine)
Stevia rebaudiana
Triticum aestivum (wheat)
Vigna angularis (adzuki bean)
Xanthosoma brasiliense (Tahitian spinach)
List of symptoms/signs
Inflorescence  -  blight; necrosis
Leaves  -  abnormal colours
Leaves  -  abnormal leaf fall
Leaves  -  necrotic areas
Stems  -  discoloration of bark
Stems  -  internal discoloration
Whole plant  -  plant dead; dieback
P. cichorii is the causal agent of leaf spot and blight diseases of ornamentals and vegetables. Symptoms may vary depending on the host and the infected part of the plant. First appearance is of water-soaked lesions that develop either at the leaf margin, near the midvein and/or are randomly distributed as leaf spots. Developing lesions are roughly circular and are rarely confined to the inter-veinal areas. These enlarge and turn dark brown or black. Lesions are sometimes surrounded by bright yellow halos. Lesions may coalesce to form very large necrotic areas and may affect the whole leaf. In some hosts symptoms may also be present on petioles, pedicels and/or stems (celery, chrysanthemum, coffee, aubergine, geranium and tomato) and flower buds (chrysanthemum, aubergine and geranium). The size of the lesions varies depending on the environmental conditions; in high humidity conditions larger lesions and rotting of infected tissues are observed, whereas in low humidity conditions lesions may only be a few millimetres diameter and the disease may eventually cease development. Abscission of severely infected leaves (dwarf schefflera (Schefflera arboricola), mint, Ficus lyrata and geranium) and, rarely, the death of the plant (ginseng, chrysantemum, celery seedlings and Ficus lyrata) have also been reported.

Specific syndromes have been described on some hosts. 'Varnish spot of lettuce' affects the blades and petioles of the inner leaves of head lettuce varieties, and is characterized by shiny, dark-brown, necrotic lesions. Lesions range in size from a few millimetres to very large and are not delimited by veins (Grogan et al., 1977). Vein blackening of the outer leaves is possible on lettuce grown in severely infested soils. Disease on lettuce is frequently reported as 'lettuce rot'.

In celery, P. cichorii causes 'bacterial blight' (leaf and petiole lesions) and 'brown stem of celery'. Symptoms on celery are confined to the stem, on which a brown discoloration appears throughout the petiole, is more evident at the base of the stalk, becoming more pronounced as the celery approaches maturity (Pernezny et al., 1994).

'Leaf rot of pepper' causes watery spots on the leaves, stem and apical regions resulting in complete decay (Rivera et al., 1981). 'Stem melanosis of spring wheat' is characterized by bleached, empty heads and blackening of the rachis, peduncle and stem immediately beneath the nodes (Piening and McPherson, 1985). Chrysanthemum leaf spot and bud blight (McFadden, 1961) produces symptoms on the leaves, buds or stem. Irregular, dark brown to black necrotic lesions develop on the leaves. The bacterium moves from the leaf through the petiole and causes a dark-brown stem necrosis. Flower buds turn dark brown and die prematurely. On chrysanthemum, P. cichorii causes 'stem necrosis', characterized by dark blue to black, water-soaked lesions along the stem, without lesions on the leaves; severely affected plants may die (Jones et al., 1983). 'Leaf spot of geranium' (Engelhard et al., 1983) causes irregularly-shaped, water-soaked spots that become dark brown to black. Yellowing of adjacent tissues invariably occurs a few days after the lesion appears and infected leaves die. Flower buds turn black and fail to open and the necrosis extends down the peduncle. A basal rot of geranium cuttings has been reported as a softening and blackening of stems. The leaf margins of affected cuttings develop chlorosis and wilt (Semer and Raju, 1984).

Detailed symptoms have also been described on other species. On gerbera (Miller and Knauss, 1973), circular to irregular, brownish-black spots, with or without a concentric ring, the lesions extending from the margins, narrowing as they reached the midvein. On Hibiscus rosa-sinensis, tan spots with purple or black margins (Chase, 1986). On tomato, dark green to dark brown, irregular blotches on the leaf blades and elongated streaks along the stem (Wilkie and Dye, 1974). On Mentha arvensis, small, water-soaked, yellow spots on the leaf edges, which cause leaf abscission at the advanced stages of disease. On ginseng, small, dark-brown spots on the central vein of the leaf that spread across the surface, leaves lose turgor and wilt. On Ficus lyrata (Chase, 1987b), angular, black lesions with purplish margins on leaves, frequently initiated at the junction of the blade and petiole, expanding along the veins into the leaf blade. The leaves may abscise and, in severe cases, the stem rots and the plant dies. On nectarines, gummy and corky spots on fruits (Pinto de Torres and Carreno Ibanez, 1983). A disease of mushrooms called oozing gills and brown blotch, which is similar to drippy gill caused by Pseudomonas agarici, is caused by strains with biochemical characteristics similar to P. cichorii (Bateson et al., 1972). P. cichorii has been also isolated from rots of bananas, carrot, cauliflower, lettuce, in mixed infections with other pseudomonads and/or Erwinia carotovora. P. cichorii is implicated in the postharvest bacterial rot of lettuce together with other fluorescent pseudomonads.
Prevention and control
Control of disease caused by P. cichorii is difficult to achieve when conditions favour the pathogen. For glasshouse operations, the ability to regulate free water on plant surfaces offers some chance of success. Soil irrigation, rather than overhead watering, will reduce the likelihood of infection and disease development. Greenhouse ventilation is beneficial. Planting material should be from sources free of the pathogen. Plants with symptoms should be isolated if of high value, or discarded. The spread of the bacterium may be reduced by decontaminating tools and hands after handling diseased plants. High plant densities and over-fertilization, especially with nitrogen fertilizers, should be avoided. Inoculum in the field may be reduced by ploughing, removing and burning infected plant debris, removing weeds near growing areas. Different cultivar susceptibility has been observed in chrysanthemum (Strider and Jones, 1986), basil (Holcomb and Cox, 1998), endive, lettuce and chicory (Matta and Garibaldi, 1970). Chemical control using copper compounds or antibiotics has been demonstrated in trials, but success in commercial practice, especially in the field, is problematic. Spray costs and the variability of efficacy may mean that applications are often not cost effective.
Under environmental conditions favourable to the pathogen, diseases incited by P. cichorii cause severe damage to the host and can result in outbreaks. Outbreaks in the nursery or in the field during warm winters in Florida, USA, can lead to widespread disease affecting thousand of plants (Jones et al., 1983; Chase and Brunk, 1984; Uddin and McCarter, 1996). Diseases caused by P. cichorii can appear sporadically over a number of years then cause severe outbreaks such as the outbreak of 'varnish spot of lettuce' in California (Grogan et al. 1977) and 'brown stem of celery' in Florida, USA (Pernezny et al., 1994). Severe disease outbreaks on lettuce leading to losses of up to 100% have been reported in California (Grogan et al., 1977), Italy (Bazzi and Mazzucchi, 1979) and Portugal (Ferreira Pinto and Oliveira, 1993). In Italy and France, P. cichorii is a recurring problem on endive and lettuce (Allex and Rat 1990; D'Ascenzo et al., 1997). In Florida, brown stem of chrysanthemum only occurs about every 5 to 6 years whereas leaf spot occurs annually (Pernezny et al., 1994).
Related treatment support
External factsheets
UF/IFAS Factsheets, University of Florida, 2000, English language
UF/IFAS Factsheets, University of Florida, 1999, English language
University of California IPM Pest Management Guidelines, University of California, 2007, English language
University of Illinois Extension Factsheets, University of Illinois, 2001, English language
University of Illinois Extension Factsheets, University of Illinois, 1990, English language
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