Development of black spot symptoms in fruits of Nova tangerine

• Published in: Phytopathology 2008-06, Vol.98 (6), p.S137-S137
• Main Authors: Rybak, MA, Canteros, B I, Cabrera, M G
• Format: Article
• Language: English
• Subjects: Citrus reticulata; Guignardia
• ISSN: 0031-949X

Development of symptoms of citrus black spot, caused by Guignardia citri-carpa (Kiely), were observed in a plot of Nova tangerine (Citrus reticulata Blanco) of ten-years-old-trees starring in March 2007 and until harvest. The grove is located at INTA Bella Vista, Corrientes, Argentina, and did not receive any spray for disease control. The fast and early development of symptoms was never observed before in this growing region, especially in young trees. All fruits were rated for disease severity at three dates: March 14, April 13, and May 15. A commonly used three degree scale was used: healthy (1), low infection (2), and high(2) severity. All fruits of each plant were observed. At the earliest date 11% of all plants showed symptoms. Diseased fruits were 36% in degreel and 64% degree 2. In April, 88% of plants were affected, and the diseased fruits were 76.5% degree 1, and 23.5% degree 2. When all fruits were harvested at fruit maturity 100% of trees have diseased fruits: 25% without symptoms (degree 0), 40% degree1, and 35% degree 2. Nova tangerine was widely planted in the last years and most groves are very young and no-symptoms of black spots were observed previously in trees this age. The fast development of symptoms in an early maturing variety suggest that programs of sprays should be determined to control black spot in Nova tangerine.