Efficacy of azoxystrobin-fludioxonil for stem-end rot control in lemon.

FOGLIATA, G.M.; ACOSTA, M.E.; MARTINEZ, C.V.; PLOPER, L.D.

Foz do Iguacu

Congreso; International Citrus Congress 2016; 2016

IAC - IAPAR

Stem-end rot (Lasiodiplodia theobromae) incidence increased in recent seasons on lemon in Tucuman, Argentina. Intense frosts alternated with droughts caused death of branches and thus increased its inoculum source. Thiabendazole application is inefficient with high disease pressure. Carbendazim is more efficient but with residues in fruit close to its maximum permissible limit; and its use in European territory was banned. Therefore, Graduate-A was evaluated as a new alternative control. Lemon fruit was inoculated with a mycelial suspension on the stem-end and treated eighteen hours later with 0.20%; 0.40%, and 1.00% of Graduate-A (azoxystrobin-fludioxonil/20.6%-20.6%), 0.80% Tecto (thiabendazole 50%) and 0.25% Chemcarb (carbendazim 50%), in laboratory test. Additionally, Graduate-A and Chemcarb were evaluated at commercial packinghouse, on fruit with natural and artificial infection. Efficacy was: 98% (Graduate-A, 1.0%), 89% (Chemcarb), 77% (Graduate-A, 0.2% and 0.4%), and 40% (Tecto) in laboratory test; 81% (Chemcarb) and 79% to 80% (Graduate-A, 0.2% to 0.4%) in packinghouse with artificially inoculated fruit; 60% to 84% (Graduate-A, 0.2% to 0.4%) and 72% (Chemcarb) with naturally infected fruit. Graduate-A showed high efficacy for stem-end rot control: from 60% to 84% when residues in fruit were between 0.50 mg/kg to 1.00 mg/kg of each active; and 98% with residues close to 2.0 mg/kg of each active. Graduate-A also controls green and blue molds (Penicillium digitatum, P. italicum) and has the advantage of being a "Reduced Risk Pesticide".