Plant Pathology Commons^™

The Effect Of Redlegged Earthmite (Halotydeus Destructor) On Legume Productivity, D J. Gillspie, D A. Nicholas

IGC Proceedings (1977-2023)

Redlegged earthmite (Halotydeus destructor) (RLEM) is a

serious pest of legume-based annual pastures in southern Australia. Observations throughout Australia show that every year they cause both mortality and growth retardation in emerging pastures in autumn, and are also responsible for reduced seed set in annual legumes in spring (Allen 1986, Norris, 1948). The most common legumes in areas where RLEM occur, are annual Trifolium species, especially T. subterraneum (subclover). However, the recent development of M edicago polymorpha and M. murex for use on acid soils together with the wider use of Ornithopus compressus, has resulted in alternative hosts for these …

Resistance In Cynodon Dactlyon To Spodoptera Frugiperda: Influence Of Strain And Dietary Conditioning, S S. Quisenberry

IGC Proceedings (1977-2023)

The most important warm-season perennial grass in the southern United States is bermudagrass (Cynodon dactylon [L.]). Fall armyworms (Spodopterafrugiperda [J.E. Smith]) are the most damaging insect pests of bermudagrass. Conse­quently, researchers have evaluated improved bermudagrass varieties for resistance to fall armyworm (Leuck et al., 1968; Lynch et al., 1983; Quisenberry and Wilson, 1985; Jamjanya and Quisenberry, 1988). Comparison of results from these studies have been contraditory, whereas Leuck et al., (1968) and Lynch et al., (1983) reported Tifton 292 to be extremely resistant (100 % larval mortality) to fall armyworm, Jamjanya and Quisenberry (1988) found it to have …

A Methodology For Evaluation Of Host Plant Resistance In Brachiaria To Spittlebug Species (Homoptera: Cercipidae), L Lapointe, G Arango, G Sotelo

IGC Proceedings (1977-2023)

Previously underutilized lowlands in tropical America are increasingly being used to produce meat and milk largely due to Brachiaria Griseb., an introducea genus of East African grass. Brachiaria is well adapted to infertile, acidic soils with high aluminium saturation. It is estimated than 16 million hectares have been planted to B. decumbens Stapf and B. humidicola (Rendle) Schweick in Latin America (Toledo and Nores, 1986). The various genera and species of spittlebugs native to the neotropics are the principal biotic factor limiting utilization of Brachiaria as forage in Latin America. Spittlebugs are capable of causing severe damage to susceptible …

Some Effects Of Diseases And Pests On Seed Production In White Clover, And Their Control, M J. Foulkes, B C. Clifford

IGC Proceedings (1977-2023)

The UK market for seed of white clover (Trifolium repens L.) cultivars is in the order of 1,000 t within an EEC total of some 3,500 t. Although high yields of around 500 kg ha-1 can be achieved, yields are extremely variable (Hides, Lewis and Mar­shall, 1984) and this may be due in part to pathogenic attack. The results reported here are of a field experiment where dis­eases and pests were controlled by pesticide applications in plots grown under two simulated seed production man­agements.

Feeding Sites Of Sitona Hispidulus Larvaw As Infection Foci For Fusarium Oxysporum F. Sp. Medicaginis In Alfalfa Roots, K T. Leath, A A. Hower

IGC Proceedings (1977-2023)

Fusarium wilt of alfalfa (Medicago sativa L.) was first described in 1927 (Weimer, 1928) in the United States and has since been reported from many other areas of the world. The causal agent is Fusarium oxysporum Sehl. f. sp. medicaginis (Weimer) Snyd. & Hans. Shoots of infected plants become yellow and wilt ; often only one side of the plant is affected. The outer root xylem tissue turns reddish brown, and infected plants usually die within one season (Leath et al., 1988). The fungus is soil-borne, survives in organic debris, and can persist up to 10 years as chla­mydospores …

Non-Chemical Control Of Some Disease And Pests In Red Fescue And Kentucky Bluegrass Seed Production, B Cagas

IGC Proceedings (1977-2023)

Diseases and pests are one of the main problems in grass seed production in Czechoslovakia. The silver top (white head) caused by the bug Leptopterna dolobrata L. and the ergot [Cla­viceps purpurea (Fr.) Tu!.] have an effect upon seed quantity and quality. In some years the leaf diseases (rusts, powdery mil­dew, spots) can play an important role in the seed ripening. The chemical control may leads to some problems. The effect of burning in two different periods (summer, spring) and the close cutting were compared in red fescue (Festuca rubra L.) and Kentucky bluegrass (Poa pratensi …

White Clover Yield, Quality, And Persistence : Insecticide, Fungicide, Nematode, And Virus Effects, G A. Pederson, G L. Windham, M M. Ellsbury, M R. Mclaughlin, R G. Pratt, G E. Brink

IGC Proceedings (1977-2023)

White clover (Trifolium repens L.) is the most important for­age legume for perennial pastures in the southeastern United States. Commonly, white clover stands decline within 2 to 3 years after seeding. This decline has been reported to be due to many factors including fungal diseases (Graham et al., 1961 ; James et al., 1980) insects (Graham et al., 1961 ; James et al., 1980), viruses (Kreitlow et al., 1957; Barnett and Gibson, 1977), and root-knot nematodes (Baxter and Gibson, 1959). No studies have evaluated effects of combinations or interac­tions of these factors on white clover growth in the field. …

La Lutte Contre Les Rouilles Du Ray-Grass Anglais Porte-Graine, H Clinkspoor, G Sicard

IGC Proceedings (1977-2023)

Les cultures de ray-grass anglais porte-graine couvrent envi­ron chaque annee en France 2800 hectares, soit un peu mains de 20 % des surfaces nationales toutes graminees confondues. Une enquete realisee sur l'etat sanitaire de ces cultures avait revele qu'elles sont souvent attaquees par des rouilles au debut de l'ete. Quatre rouilles peuvent ainsi etre rencontrees : la rouille cou­ronnee provoquee par Puccinia coronata est la plus frequente ; la rouille noire (P. graminis), la rouille brune (P. loliina) et la rouille jaune (P. striiformis) peuvent egalement se rencontrer. En conditions climatiques favorables, Jes cycles d'infection …

A Multi-Disciplinary Approach To Anthracnose Diseases Of Stylosanthes In Australia, D F. Cameron, S Chakraborty, R D. Davis, L A. Edye, J.A G. Irwin, J M. Manners, I B. Staples

IGC Proceedings (1977-2023)

Breeding Stylosanthes for resistance to anthracnose diseases in northern Australian pastures is complicated by extensive pathogenic variation in the fungal pathogen, Colletotrichum gloeosporiodes. We have put considerable emphasis on epidemiological studies in an attempt to devise optimal strategies for the use of resistance genes in our selection and breeding programs. In addition, techniques of molecular biology are being used to investigate prospects for the use of genes from novel sources and to study the genetics of virulence in the pathogen.

Breeding For Resistance To Bacterial Wilt Of Grasses (Xanthomonas Campestris Pv. Graminis), D Schmidt

IGC Proceedings (1977-2023)

Bacterial wilt of fodder grasses caused by Xanthomonas campestris pv. graminis was first described by Egli et al. (1975), and since then observed all over Europe and in New Zealand. The regular mowing of the crop offers ideal conditions for spreading of the pathogen. Several grass species are affected. The most severe yield losses occur in Lolium multiflorum, particularly in var. westerwoldicum. In extreme cases, all the plants can be killed during hot, dry summers. Gondran and Betin (1988) found up to 47 % of yield loss in the three cuts following inoculation of Italian rye-grass cultivars. Losses are less …

L’Anthracnose De La Luzerne Dans Le Maroc Oriental Resistance De Quelques Cultivars Et Lignees, Huguette Gosset, B M. Troeung, G Raynal

IGC Proceedings (1977-2023)

Dans le Maroc oriental (regions d'Oujda, Berkane, Ai:n Beni Mathar), la luzerne (Medicago sativa L.) ne peut etre cultivee que dans les zones irriguees, en raison de l'aridite du climat. Dans ces conditions, elle est exploitee pour le fourrage tous les 20 jours au printemps et en ete et tous les 30-40 jours en automne et en hiver. La variete largement utilisee actuellement est Moapa dont les cultures, lorsqu'elles sont saines, durent 5 ans. Des prospections nous ont montre que de nombreux pro­blemes sanitaires existent. C'est ainsi que l'anthracnose (Colle­totrichum trifolii Bain et Essary) apparait comme !'affection fongique predominante …

Diachorella Leaf Spot Of Prairie Milkvetch In Loess Plateau, China, Hou Tianjue, Wang Jiangfeng

IGC Proceedings (1977-2023)

Prairie Milkvetch (Astragalus adsurgens), an acclimatized good sand binder, soil and water conservation legume forage plant, cultivated widely in the arid and semi-arid districts of North China, is especially suitable for the Loess Plateau, China. Unfortunately in the mid Inner Mongolia, North Shaanxi Province and the eastern part of Gansu Province, it is often infected seriously with Diachorella leaf spot (Diachorella lathyri Fckl.). The disease primarily affects leaves, but some­times attacks petioles and stems. On infected leaflets first appear small black spots. As the spots increase, whole leaflet is blackened. Heavy infections kill leaflets and cause severe …

La Certicilliose De La Luzerne En France Mise Au Point Apres 15 Annees D’Observations, J Gondran

IGC Proceedings (1977-2023)

La verticilliose de la luzerne (Verticillium albo-atrum R.B.) fut determinee pour la premiere fois en France il y a une tren­taine d'annees. Depuis, nous avons etudie la repartition geo­graphique de la maladie (Gondran, 1976) et la biologie du parasite· (Gondran, 1977). Nous avons mis au point un test de selection permettant de creer des varietes resistantes (Gondran in Massenot et al., 1978). Nous avons commence une etude sur la variabilite du pouvoir pathogene du champignon (Gondran, 1985). Nous nous proposons de faire le point sur !es etudes sui­vantes : degats de la maladie, variabilite du pouvoir pathogene du …

Observations Sur La Dissemination D’Epichloe Typhina, L’Agent De La Quenouille Des Graminees Et Reflexions Sur Les Diverses Especes D’Acremonium, G Raynal

IGC Proceedings (1977-2023)

La quenouille des graminees est due a l'Ascomycete Epichloe typhina (Pers. ex Fr.) Tulasne. Des l'epiaison, Jes inflorescences malades sont emprisonnees clans un manchon blanc (stade ase­xue Sphacelia typhina = Acremonium typhinum), qui prend progressivement une couleur orangee, pour donner le symp­t6me typique de quenouille. Le stroma des quenouilles ren­ferme Jes loges peritheciales caracterisant le stade sexue Epichloe et produisant Jes ascospores responsables des conta­minations. De nombreuses graminees sont attaquees, dont le dactyle ( Dactylis glomerata L.), qui peut subir de serieux dom­mages en France clans Jes regions de production de semence. En effet, Jes fleurs ne peuvent pas, …

Mycoflora Response To Burning On Sand Prairie, S S. Dhillon, C Anderson

IGC Proceedings (1977-2023)

The rhizoplane and root interior support different popula­tions of microorganisms. A large number of these organisms are microfungi. Studies have shown that fire induced changes are favourable for some groups of microorganisms following grasslands fires. However, most studies have dealt with the effect of burning on surface and subsurface soil organisms but none have examined rhizoplane fungi. This study was conducted to examine little bluestem (Schiz­achyrium scoparium), a native prairie grass species, biomass production and associated vesicular-arbuscular mycorrhizae (V AM) and rhizoplane mycoflora and their response to burning.

Recent Effects Of Acremonium Coenophialum On The Performance Of Beef Cattle Grazing Festuca Arundinacea, H A. Fribourg, J B. Mclaren, A B. Chestnut, J C. Waller

IGC Proceedings (1977-2023)

Infection of tall fescue (F. arundinacea Schreb.) plants by the endophytic fungus A. coenophialum Morgan-Jones & Garns is associated with substantial economic reduction in grazing ani­mal performance (Bacon and Siegel, 1988 ; Bush and Burrus, 1988 ; Stuedemann and Hoveland, 1988). This problem is serious in the transition zone of the eastern U.S.A., affecting over 12 million ha of pasture land.

Mutualistic Symbiosis Of Tall Fescue And Fungal Endophyte, C S. Hoveland, C W. Bacon, N S. Hill

IGC Proceedings (1977-2023)

The greatly improved performance of livestock consuming low-endophyte tall fescue (Festuca arundinacea) forage has stimulated production of endophyte-free seed and replanting Acremonium coenophialum infected pastures (Stuedemann and Hoveland, 1988). Since endophytic fungi co-evolved with their host and are non-pathogenic, the endophyte-plant relationship is likely a mutualistic symbiosis (Bacon and Siegel, 1988). An important question arises as to whether tall fescue free of the endophyte will have the same productivity and persistence as infected grass in stressful environments. If the fungus benefits from the association by receiving nutrients, protection, repro­duction, and dissemination, then the plant may be aided by …

Effect Of Differing Levels Of Acremonium Coenophialum Infection Of Tall Fescue (Festuca Arundinacea) On Bovine Serum Prolactin, A B. Chestnut, B H. Erickson, P P. Mckenzie, H A. Fribourg, J B. Mclaren, J C. Waller

IGC Proceedings (1977-2023)

Depressed concentrations of serum prolactin (PRL) have been observed in cattle grazing tall fescue (F. arundinacea Schreb.) infected with the endophytic fungus A. coenophialum Morgan-Jones and Garns (Thompson et al, 1987). Lower PRL concentrations may be partially responsible for poor perform­ance of cattle consuming endophyte infected (E+ ) vs .. non­infected (E-) fescue since PRL is involved in mammary gland development, thermoregulation, and immune response. To determine the relationship between PRL concentration in cattle and percent E + plants in pastures they graze, studies were con­ducted at two locations in Tennessee.

Reaction Of Macroptilium Atropurpureum (Dc) Urb. Accessions To Angular Leaf Spot Caused By Isariopsis Griseola Sacc., R M. Sonoda, A E. Kretschmer Jr

IGC Proceedings (1977-2023)

Macroptilium atropurpureum (D.C.) Urb. is a viny tropical legume, native to central America and tropical South America (Tothill 1966), with potential for pasture use in south Florida and other parts of the tropics and subtropics (Kretschmer, 1972). Isariopsis griseola Sacc. causes leaf spotting and defoli­ation of M. atropurpureum cultivar 'Siratro' in Florida (Lenne and Sonoda, 1985), in early spring and late fall, when forage availability is minimal. The disease is also present in native populations of M. atropurpureum in South and Central America (Lenne and Sonoda, 1985). I. griseola is generally considered to cause only minor damage (Lenne and …

Importance Of Rhizoctonia Foliar Blight Of The Promising Tropical Pasture Legume Genus Centrosema, J M. Lenne, G Olaya, J W. Miles

IGC Proceedings (1977-2023)

Centrosema is a well-known American legume genus adapted to a wide range of tropical and subtropical environments. Sev­eral species have considerable potential as pasture legumes (Clements et al., 1983). Of 38 genera of fungal pathogens recorded on Centrosema, Rhizoctonia species, the causal agents of foliar blight, are regarded as the most damaging (Lenne et al., 1988).