Peronospora arborescens. [Descriptions of Fungi and Bacteria].

1981 ◽  
Author(s):  
S. M. Francis
Keyword(s):  
Geographical Distribution ◽  
Disease Transmission ◽  
Field Experiments ◽  
Indirect Evidence ◽  
Lower Surface ◽  
Diseased Plant ◽  
Infected Seed ◽  
Aerial Parts ◽  
Secondary Infections ◽  
One Year

Abstract A description is provided for Peronospora arborescens. Information is included on the disease caused by the organism, its transmission, geographical distribution, and hosts. HOSTS: Papaver alpinum, P. dubium, P. caucasicum, P. nudicaule, P. rhoeas, P. somniferum, P. setigerum, Meconopsis spp. DISEASE: Downy mildew of the opium poppy, Papaver somniferum. Seedlings if attacked usually succumb. In older plants the infection may be systemic with all parts of the plant, including the growing point, affected. In Berkeley's original diagnosis of the pathogen on P. rhoeas he described infected plants as 'having a peculiar aspect by which they may be known at a distance'. The leaves appear greenish-yellow, thickened and deformed. Conidiophores develop as a greyish violet felt on the lower surface of the leaves and in severe attacks appear on the stems, buds and capsules. Local secondary infections also occur usually on the lower leaves and here the pathogen forms rather angular chlorotic blotches on the upper leaf surface. These are often associated with the larger veins. GEOGRAPHICAL DISTRIBUTION: Africa (Algeria, Egypt); Asia (Afghanistan, Azerbaijan (USSR), India, Iran, Japan, Turkey, Pakistan); Australasia (Australia); Europe (widespread); S. America (Argentina). TRANSMISSION: Authors agree that diseased plant debris remaining in the fields can infect a subsequent crop and that the practice of using this debris to manure the ground is to be deprecated. Opinions differ on the part that the oospores, which are formed in profusion in all aerial parts, play in this primary infection. Neither Behr (1956) nor Kothari & Prasad (1970) were able to germinate resting spores. Behr considered that they had no part in disease transmission. Kothari & Prasad (1970), however, in a series of field experiments obtained indirect evidence that oospores present in the soil could become infective one year after their formation. The role of infected seed in transmitting the disease is also disputed. Yossifovitch (1929) and Kothari & Prasad (1970) suggested that infected seed is not important while Behr (1956) showed that perennating mycelium was present in the seed from diseased crops. Alavi (1975), in experiments made over several years on farms in Iran, reported a high probability that the disease was transmitted by seeds.

Peronospora sparsa. [Descriptions of Fungi and Bacteria].

1981 ◽  
Author(s):  
S. M. Francis
Keyword(s):  
Downy Mildew ◽  
Geographical Distribution ◽  
Disease Transmission ◽  
Unknown Origin ◽  
Northern Europe ◽  
Flower Buds ◽  
Rosa Canina ◽  
Necrotic Spots ◽  
One Year

Abstract A description is provided for Peronospora sparsa. Information is included on the disease caused by the organism, its transmission, geographical distribution, and hosts. HOSTS: Cultivated roses and the following species, Rosa californica, R. centifolia, R. canina, R. chinensis, R. rubiginosa. DISEASE: Downy mildew of rose. Bright red to purple or, less frequently, brown spots develop on the leaves which fall very readily especially if the bushes are shaken gently. A non-parasitic defoliation of unknown origin termed a 'false mildew' has been reported from France (Tramier, 1962). The necrotic spots formed on the leaves are similar at a certain stage to those caused by P. sparsa. Conidiophores and conidia develop on the under surface of the downy mildew spots in high relative humidity. In Europe their production is sparse but in California it is reported as copious (Baker, 1953). In heavy infections stems and flowers (both calyx and petals) become diseased and badly infected and young stems often die back. Flowers and flower buds can be retarded and malformed by the pathogen without visible damage to the leaves (53, 3523). GEOGRAPHICAL DISTRIBUTION: Africa (Egypt, Morocco, S. Africa, Zimbabwe); Asia (Brunei, Iran, Israel, Japan, Mauritius, Philippines); Australasia (Australia, New Zealand); Europe (Austria, Britain (incl. Jersey), Bulgaria, Czechoslovakia, Estonia, France, Germany, Greece, Iceland, Italy, Latvia, Netherlands, Portugal, Poland, Romania, Sweden, Switzerland, Yugoslavia, USSR); N. America (Canada, USA); S. America (Argentina, Brazil). TRANSMISSION: As dormant mycelium in cuttings and plants. It is reported that mycelium can overwinter within infected stems both from warmer countries such as Australia (57, 2154) and Brazil (19, 98) and also from Northern Europe (53, 3523). The role of oospores in disease transmission is less certain. They have been found in leaves and stems (Baker, 1953; Fraymouth, 1956) and flowers (Cuboni, 1888) but their occurrence seems to be sporadic and they do not appear to be of great importance in carrying over the pathogen. The possibility that the disease may be seed borne was suggested by a worker in Poland (7, 325). In 1926 downy mildew was discovered in a commercial nursery near Lublin on one-year-old seedlings of Rosa canina. The seedlings had been raised from seed imported from Vienna and the inference was that the disease came with the seed especially as all seedlings of local origin were healthy. Peronospora sparsa is not listed as a seed pathogen by Neergaard (1977).

Bremia lactucae. [Descriptions of Fungi and Bacteria].

1981 ◽  
Author(s):  
W. M. Morgan
Keyword(s):  
Geographical Distribution ◽  
Systemic Infection ◽  
Lower Surface ◽  
Globe Artichoke ◽  
Bremia Lactucae ◽  
Lettuce Plant ◽  
Mature Leaves ◽  
Secondary Infections ◽  
Important Means ◽  
Means Of Transmission

Abstract A description is provided for Bremia lactucae. Information is included on the disease caused by the organism, its transmission, geographical distribution, and hosts. HOSTS: At least 230 species in the following genera of Compositae: Agoseris, Arctium, Carduus, Carthamus, Centaurea, Cichorium, Cineraria, Cirsium, Crepis, Cynara, Dendroseris, Dimorphotheca, Erechtites, Gaillardia, Gnaphalium, Helichrysum, Hemistepta, Hieracium, Hypochoeris, Jacobaea, Knightia, Lactuca, Lagoseris, Lapsana, Lappa, Leontodon, Mulgedium, Nabalus, Picris, Prenanthes, Rhodanthe, Saussurea, Senecio, Solidago, Sonchus, Taraxacum and Tragopogon. DISEASE: 'Downy mildew' of lettuce, globe artichoke, endive, chicory and many ornamental and wild species of Compositae. Infection can occur on any part of the lettuce plant (Lactuca sativa) except the capitulum (40: 197) and the fungus may colonize the plant systemically even as far as the roots (42: 429). In infected seedlings, the cotyledons stop growing, leading to stunting or death of the plant. Sporulation occurs on both sides of the cotyledon, which becomes chlorotic. As seedlings age, they become less susceptible, systemic infection becomes progressively less and fewer sporangiophores are produced (53, 3262). Newly formed true leaves are less susceptible than cotyledons (53, 3262). On mature leaves, profuse sporulation on the lower surface is sometimes preceded by a slight chlorosis; in widespread infections of wrapper leaves conidiophores are often the first sign of infection. On the upper surface chlorosis becomes severe and the lesion, bounded by the main veins, is frequently angular in appearance. Browning may occur later, probably due to secondary infections. On globe artichoke (Cynara scolymus) infection of the peduncle and basal bracts allows access to secondary infections (43, 3104). GEOGRAPHICAL DISTRIBUTION: World-wide except Antarctica and Arctic (CMI Map 86, ed. 3, 1969). TRANSMISSION: Sporulation is usually profuse and conidia are air-borne. Conidia from cultivated lettuce are viable for at least 60 days at low temperatures and high humidity (40: 197) and, where lettuce is grown throughout the year, conidia are the most important means of transmission of the disease. The fungus is probably also carried over from season to season by means of oospores in soil debris (51, 3663).

Peronospora antirrhini. [Descriptions of Fungi and Bacteria].

1981 ◽  
Author(s):  
S. M. Francis
Keyword(s):  
Downy Mildew ◽  
Geographical Distribution ◽  
Seed Transmission ◽  
Lower Surface ◽  
Flowering Plants ◽  
Antirrhinum Majus ◽  
High Humidity ◽  
Secondary Infections ◽  
Leaf Surfaces ◽  
Definite Proof

Abstract A description is provided for Peronospora antirrhini. Information is included on the disease caused by the organism, its transmission, geographical distribution, and hosts. HOSTS: Antirrhinum majus, A. nuttallianum, Misopates orontium. DISEASE: Downy mildew of antirrhinum. This is mainly a disease of seedlings and young plants. The infection is systemic and affected plants appear stunted and pale yellowish-green. The leaves are curled inwards and droop down. Conidiophores develop on the lower surface forming a fine white to purple down. In heavy infections the down is found on both leaf surfaces and also on the stems. The growing point may be killed and then plants often break from the base and produce several new shoots. Conidia can cause secondary infections on the leaves of older plants especially in conditions of high humidity. These appear as pale yellowish spots. GEOGRAPHICAL DISTRIBUTION: Worldwide, see CMI Map No. 222 ed. 2, 1971. TRANSMISSION: Seed transmission by oospores was tentatively suggested by Yarwood (1947). Moore & Moore (1952) refer to circumstantial evidence but say there is no definite proof. Peronospora antirrhini is not recorded as a seed pathogen by Richardson (1979) but Neergaard (1977) points out that for seed-borne infection of a downy mildew to be effective all that is needed is a mere trace of the fungus on the seed. As Yarwood (1947) indicates, terminal infections of flowering plants could easily contaminate seed.

Herbicide Effects on Weed Control and Shoot Growth of Young Apple (Malus sylvestris) and Peach (Prunus persica) Trees

1994 ◽  
Vol 8 (4) ◽  
pp. 840-848 ◽  
Author(s):  
Chester L. Foy ◽  
Susan B. Harrison ◽  
Harold L. Witt
Keyword(s):  
Shoot Growth ◽  
Field Experiments ◽  
Prunus Persica ◽  
Weed Species ◽  
Apple Trees ◽  
Herbicide Treatments ◽  
One Year ◽  
Broadleaf Species ◽  
Old Trees ◽  
Peach Trees

Field experiments were conducted at two locations in Virginia to evaluate the following herbicides: alachlor, diphenamid, diuron, metolachlor, napropamide, norflurazon, oryzalin, oxyfluorfen, paraquat, pendimethalin, and simazine. One experiment involved newly-transplanted apple trees; the others, three in apple and one in peach trees, involved one-year-old trees. Treatments were applied in the spring (mid-April to early-May). Control of annual weed species was excellent with several treatments. A broader spectrum of weeds was controlled in several instances when the preemergence herbicides were used in combinations. Perennial species, particularly broadleaf species and johnsongrass, were released when annual species were suppressed by the herbicides. A rye cover crop in nontreated plots suppressed the growth of weeds. New shoot growth of newly-transplanted apple trees was increased with 3 of 20 herbicide treatments and scion circumference was increased with 11 of 20 herbicide treatments compared to the nontreated control. Growth of one-year-old apple trees was not affected. Scion circumference of one-year-old peach trees was increased with 25 of 33 herbicide treatments.

Arthrocladiella mougeotii. [Descriptions of Fungi and Bacteria].

1998 ◽  
Author(s):  
V. P. Heluta
Keyword(s):  
Czech Republic ◽  
Geographical Distribution ◽  
Disease Transmission ◽  
Russian Far East ◽  
Far East ◽  
Republic Of Georgia ◽  
Lycium Barbarum ◽  
Initial Stage ◽  
High Infection

Abstract A description is provided for Arthrocladiella mougeotii. Information is included on the disease caused by the organism, its transmission, geographical distribution, and hosts. DISEASE: Powdery mildew of Lycium species only. The mycelium, conidiophores, conidia and ascomata form first white, then dirty-grey patches on damaged green parts of the host. Infected parts are deformed slightly and, in cases of high infection, plants can lose their ornamental qualities. Damaged leaves can fall prematurely. HOSTS: Lycium barbarum (= L. europaeum), L. chinense, L. dasystemum, L. halimifolium, L. ovatum, L. potaninii, L. rhombifolium, L. ruthenicum. [Type host - Lycium barbarum] GEOGRAPHICAL DISTRIBUTION: Africa: Canary Islands. Asia (temperate areas only): Armenia, Azerbaijan, China, Republic of Georgia, Israel, Japan, Kazakhstan, Kirghizistan, Korea, Russia (Russian far east), Tadzhikistan, Taiwan, Turkey, Turkmenistan, Uzbekistan. Australasia: New Zealand (introduced). Europe: Austria, Belgium, Bulgaria, Czech Republic, Estonia, France, Germany, Hungary, Italy, Netherlands, Norway, Poland, Rumania, Slovakia, Sweden, Switzerland, UK, Ukraine (southern), former Yugoslavia. North America: USA (introduced). TRANSMISSION: By wind-dispersed conidia. The rôle of ascospores in disease transmission is unknown, although it has been supposed that they can cause the initial stage of the disease.

Daldinia eschscholzii. [Descriptions of Fungi and Bacteria].

2006 ◽  
Author(s):  
D. W. Minter
Keyword(s):  
Geographical Distribution ◽  
Disease Transmission ◽  
Host Plants

Abstract This paper describes Daldinia eschscholzii and includes information on its taxonomy, the diseases caused, host plants, geographical distribution, and disease transmission.

Septoria apiicola. [Descriptions of Fungi and Bacteria].

1966 ◽  
Author(s):  
B. C. Sutton
Keyword(s):  
Late Blight ◽  
Geographical Distribution ◽  
Irrigation Water ◽  
Leaf Spot ◽  
World Wide ◽  
Host Tissue ◽  
Variable Size ◽  
Infected Seed ◽  
Seedling Roots ◽  
Rain Splash

Abstract A description is provided for Septoria apiicola. Information is included on the disease caused by the organism, its transmission, geographical distribution, and hosts. HOSTS: On Apium spp. DISEASE: Leaf spot (or late blight) of cultivated and wild celery and celeriac. On leaves, seeds and seedling roots, reducing yield and causing wastage through blemishes on the edible petioles. Leaf lesions of variable size, 1-6 mm diam., abundant, amphigenous, circular or sometimes vein-limited, confluent when severe, becoming depressed pale brown, margin diffuse. GEOGRAPHICAL DISTRIBUTION: World-wide on Apium spp. TRANSMISSION: Seed-borne (Noble et al., 1958; Sheridan, 1966). Also disseminated by rain-splash, in irrigation water, by contact as well as by animals and workman's tools (Chupp & Sherf, 1960). The pathogen may remain viable in the soil for 18 months in buried celery crop refuse, but for less than 6 weeks in the absence of intact host tissue (42: 82). Viability in infected seed may drop to 2% within 8 months from harvest and both mycelium and conidia can stay alive in seed stored up to 14 months (42: 508; 44, 1332) but not beyond 2 yr.

scholarly journals Ants defend aphids against lethal disease

2009 ◽  
Vol 6 (2) ◽  
pp. 205-208 ◽  
Author(s):  
Charlotte Nielsen ◽  
Anurag A. Agrawal ◽  
Ann E. Hajek
Keyword(s):  
Social Insects ◽  
Natural Enemies ◽  
Disease Transmission ◽  
Field Experiments ◽  
Fungal Infections ◽  
Pandora Neoaphidis ◽  
Aphid Pathogen ◽  
Formica Podzolica

Social insects defend their own colonies and some species also protect their mutualist partners. In mutualisms with aphids, ants typically feed on honeydew produced by aphids and, in turn guard and shelter aphid colonies from insect natural enemies. Here we report that Formica podzolica ants tending milkweed aphids, Aphis asclepiadis , protect aphid colonies from lethal fungal infections caused by an obligate aphid pathogen, Pandora neoaphidis . In field experiments, bodies of fungal-killed aphids were quickly removed from ant-tended aphid colonies. Ant workers were also able to detect infective conidia on the cuticle of living aphids and responded by either removing or grooming these aphids. Our results extend the long-standing view of ants as mutualists and protectors of aphids by demonstrating focused sanitizing and quarantining behaviour that may lead to reduced disease transmission in aphid colonies.

Alternaria sesami. [Descriptions of Fungi and Bacteria].

1970 ◽  
Author(s):  
M. B. Ellis
Keyword(s):  
Geographical Distribution ◽  
Sesamum Indicum ◽  
Leaf Fall ◽  
Damping Off ◽  
Infected Seed

Abstract A description is provided for Alternaria sesami. Information is included on the disease caused by the organism, its transmission, geographical distribution, and hosts. HOSTS: Sesamum indicum. DISEASE: Pre-emergence and post-emergence damping off and leaf, stem and pod spot. On the leaves the brown, round or irregular spots are up to 2 crn diam. with concentric zonations on the upper surface, coalescent; leaf fall can be severe. Stem and capsule lesions may be less conspicuous but those on the former can present a water-soaked appearance, spreading almost the whole length of the stem. Infected seed leads to reduced emergence. GEOGRAPHICAL DISTRIBUTION: Fairly widespread in Asia, E. & W. Africa, S. America and S.E. U.S.A. Details are given in CMI Map 410, ed. 1; Ethiopia is an additional recent record. TRANSMISSION: Seedborne; spread may have occurred mainly through seed.

Pseudomonas sesami. [Descriptions of Fungi and Bacteria].

1964 ◽  
Author(s):  
A. C. Hayward
Keyword(s):  
United States ◽  
Phaseolus Vulgaris ◽  
East Africa ◽  
Geographical Distribution ◽  
Leaf Spot ◽  
Aerial Parts ◽  
Annotated List

Abstract A description is provided for Pseudomonas sesami. Information is included on the disease caused by the organism, its transmission, geographical distribution, and hosts. HOSTS: On Sesamum orientale (Pedaliaceae). Infects stems, pods, but not the leaves of Phaseolus vulgaris on inoculation. DISEASE: A leaf spot affecting aerial parts of plant. Blackish-brown spots which coalesce may extend along whole length of stem. Angular spots on leaves delimited by veins. Infected capsules blacken. GEOGRAPHICAL DISTRIBUTION: Parts of East Africa; China, Japan, Korea, Bulgaria, Greece, Turkey, Yugoslavia, United States, Brazil (CMI Map 398). TRANSMISSION: Presumably by wind driven rain; on seed, see Noble et al., An Annotated List Of Seed-Borne Diseases, CMI, Kew, 1958, p. 117.

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