Citrus black spot control on lemon in Tucumán, Argentina.

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

Foz do Iguacu

Congreso; International Citrus Congress 2016; 2016

Argentina contributes with 11% to the world lemon export market. Citrus black spot (CBS) restricts exports because it is quarantine in the European Union, main Argentine lemon destination. Therefore, fungicide efficacy was evaluated during ten seasons in the field and two in packinghouse, in a CBS high incidence field. Five copper fungicides applications were made, every thirty days from petal fall, alone and with one or two strobilurin applications. Highest efficacy was obtained with strobilurin: 90% to 99% with one application (sixty or ninety days after petal fall) or double application (sixty and ninety days after petal fall). Copper fungicides efficiency ranged from 89% to 97% with cuprous oxide, 79% to 90% with copper oxychloride, and 77% to 91% with cupric hydroxide. Field treatments also reduced postharvest symptoms, from 40% (untreated control) to less than 3% with strobilurin. In 2015, CBS incidence increased due to adverse weather conditions which caused high levels of secondary inoculum and its dispersion. Consequently, efficacy decreased to 89% (double strobilurin application), 80% (single application), 76% (cuprous oxide), 71% (copper oxychloride), and 50% (cupric hydroxide). As postharvest treatment, Graduate-A (azoxystrobin-fludioxonil) significantly reduced development of symptoms, compared to fungicides commonly used in packinghouse, in symptomless fruit from untreated field plots. Effective CBS control is achieved with field applications, and could be enhanced by postharvest treatments, such as azoxystrobin-fludioxonil.