Chemical Control

Ramulosis in cotton

Glomerella gossypii (Colletotrichum gossypii var. cephalosporioides)

By Vinicius Garnica

• Shrub plant native from tropical and subtropical regions around the world, including the Americas, Africa, and India

• Most widely used natural fiber cloth in clothing today

• China is the biggest importer with approximately 14,1 million 480 lb. in 2013/2014

• $5.20 billion in crop value in U.S.

National Cotton Council of America. Retrieved from http://www.cotton.org/econ/world/detail.cfm

Cotton

Source: USDA

Million 480 BalesMillion 480 Bales

Anthracnose in cotton

• Caused by Glomerella gossypii (Colletotrichum gossypii)

• Host specificity, only affects cotton• Cultivars vary in level of severity

• G. gossypii probably indigenous to America, now occurs in most cotton-growing areas throughout the world but tends to be localized in the higher rainfall areas.

• Scald-like lesions in stems and leaves. Also causes damping off on seedling

• Infected bolls develop small, round, water-soaked spots which rapidly enlarge, become sunken and finally develop reddish borders with pink centres

OEPP/EPPO (1982) Data sheets on quarantine organisms No. 71, Glomerella gossypii. Bulletin OEPP/EPPO Bulletin 12 (1).

Guo Shupu, II-AAAS

Anthracnose in cotton

http://www.plantwise.org/KnowledgeBank/Datasheet.aspx?dsid=25358

• Colletotrichum gossypii var. cephalosporioides differs from C. gossypii var. gossypii in invirulence, aggressiveness, morphology, growth on various media and ability to develop at less than 30°C.

• C. gossypii var. cephalosporioides causes ramulosis or witches' broom disease and it only was reported in Brazil and Paraguay, so far, whereas C. gossypii var. gossypii occurs world-wide.

Follin, J.C. (1970) Spécialisation physiologique chez Colletotrichum gossypii South. Coton et Fibres Tropicales 25, 387-388.

Photo: FMC. Manual of Cotton Diseases

Two different etiological agents

Ramulosis• Yield losses averaging 20-38%

• Most economic limiting disease in Brazilian cottony industry

• C. gossypii var. cephalosporioides survives saprophytically as micellium in decaying plant material

• Main source of inoculum contaminated seeds

• Conidia embedded in water-soluble mucilage are rain splashed onto leaves

• Infection favored by temperatures between 25-30C , high humidity and wounding caused

Kimati, H., Amorim, A., Bergamim, F. A. 1997. Manual de Fitopatologia, Vol.2: Doenças de Plantas Cultivadas. Editora Agronomia Ceres.

Cassetari Neto, D.; Santos, E.N.; Zambenedetti, E.B.; Leite, J.J.; Valcanaia, E.; Araujo, D.V.; Andrade, J.R.; Avila, W.P.; Caye, S.;Aenhold, D. Controle de fungos na parte aérea do algodão no Mato Grosso in: Anais do III Congresso Brasileiro de Algodão. Campo Grande. EMBRAPA/CNPA-CPAO, UFMS. Campo Grande-MS. 2001 p.543-545

• Fungus can attack plant at any growth stage. Young tissue of plant meristem, leaves, bolls are affected

• Unequal growth of infected foliar blade

causes the leave to crack, forming necrotic stellate spots

• Infect the apical meristem leading to its death, which promotes lateral branching, shortening of internodes and reduction in plant size

Chitarra, L. G. 2014. Doenças do Algodoeiro. SOCIEDADE BRASILEIRA DE FITOPATOLOGIA (SBF). Retrieved from http://www.sbfito.com.br/divulgacao/doencasdoalgodoeiro.pdf

Photo: FMC. Manual of Cotton Diseases

Photo: Oliveira, L.

Photo: FMC. Manual of Cotton Diseases

Photo: IAC, SP.

Photo: Oliveira, L.

Conidia

Symptoms of pink rot roll caused by (Gg). Incubation period is approximately 15 days at 15°C, 11 days at 20°C, 10 days at 25°C, and 9 days at 30°C.

Plant architecture, leaf size and shape, plant stand influence microclimate into the canopy

Asexual phase

Ascospores

Perithecia

Sexual phase

G. gossypii C. gossypii var. cephalosporioides (only asexual)

2nd Inoculum

1st Inoculum

Plant debri, source of overwintered inoculum. Early plowing of fields increases the degradation of plant tissues and reduce the pathogen survival.

Author: Vinicius Garnica

Acervuli

Infested seed, rainfall, wind, overhead irrigation are important in dissemination of propagules.

Damping off at seedling-stage(Gg) and reduced growth associated with excessive branching (Cgc)

At 25°C, weekly rainfall of 60 mm leads to greater periods of leaf wetness (6h up to 32h), which promotes optimum condition for infection

Chemical control of ramulosis in cotton

Photo by APP

• Strobilurins (QoI fungicides) – Act preventing electron transfer at cytochrome bc1 complex • azoxystrobin • pyraclostrobin• trifloxystrobin

• Triazoles (demethylation inhibitors, DMI) – Inhibit C14-demethylase, component of sterol production• Flutriafole• Epoxiconazole• Tebuconaloze

• Benzimidazoles – Inhibition of ß-tubulin assembly in mitosis• carbendazim• thiophanate methyl

• Carboxanilide (SDHI) – Inhibitor of complex II: Succinate dehydrogenase • Carboxin

• Dithiocarbamate – Multi site Action • Thiram

Products registered in Brazil for ramulosis

Vincelli, P. (2002) QoI (Strobilurin) Fungicides: Benefits and Risks. The Plant Health Instructor. DOI: 10.1094/PHI-I-2002-0809-02. Updated, 2012.FRAC. Fungicide Resistance Action Committee. 2015AGROFIT. MAPA

Effect of fungicide treatment on severity of ramulosis

Untreated co

ntrol

Azoxystrobin

Tebuconazole +

thiophanate methyl

trifloxystr

obin +

propiconazole

tebuconazole +

HEC 5725trifl

oxystrobin

tebuconazole +

trifloxystr

obin

Seve

rity

ratin

g

Iamamoto, M.M.; Goes, A.; Cia, E.; Belot, J.L. Controle químico de ramulose no algodoeiro In: Anais do III Congresso Brasileiro de Algodão. Campo Grande. EMBRAPA/CNPA-CPAO, UFMS. Campo Grande-MS. 2001 p. 625-626.

• 3 fungicide applications resulted in 26.8% increase in yield, and 65.8% less incidence of disease

Ampasul, Brazil 2014

Thank you