From 2011 to 2020, Chile kept the Pseudomonas syringae pv. actinidiae (PSA) bacterium, responsible for kiwi bacteriosis, under control. At present, however, this pest is considered "present" in the country, especially affecting the Metropolitan and Biobío regions. Due to its spread through propagation material, PSA will continue to be a regulated pest for kiwi (Actinidia spp.).
This bacterium affects both green and yellow kiwi, but the latter is more susceptible, which has hindered the development of this variety in Chile. This year's weather conditions, especially the polar frosts during the winter, catalyzed the spread of PSA, leading to a high incidence of the disease in areas that were previously unaffected.
According to Raimundo Cuevas, Technical Manager of Abud & Cia, there is a direct correlation between the intensity of the frosts and the manifestation of the disease. Areas with less frost experienced minimal damage. In contrast, areas with severe frost were more impacted by the disease. The plants' vulnerability to low temperatures has favored the virulence of PSA, especially in July, when temperatures fell below freezing for more than 100 cumulative hours.
PSA symptoms manifest between August and September, coinciding with the pruning of plants and red sap exudation. This significantly affects production because, although many plants can recover, the damage caused to the number of shoots is irreparable. Young plantations, 1 to 4 years old, have been particularly susceptible, with damage ranging from 10-15% to 50% of plants affected.
Mr. Cuevas also warned about the high bacterial load in the environment and highlighted the importance of aggressive and periodic management using bactericides, such as copper sulfate pentahydrate or antibiotics, to protect future production. The PSA threat to the floral button and flower underscores the need to meticulously apply the phytosanitary program to minimize production losses.
Source: redagricola.com