002 Epidemiology of Postbloom Fuit Drop in Sweet Orange cv. Valencia in Mexico

• Published in: HortScience Vol. 35; no. 3; p. 388
• Main Authors: Reyes-Gonzalez, B, Mora-Aguilera, G, Osada, S, Teliz, D, Diaz, U
• Format: Journal Article
• Language: English
• Published: 01-06-2000
• ISSN: 0018-5345; 2327-9834
• DOI: 10.21273/HORTSCI.35.3.388A

The temporal progress of postbloom fruit drop was characterized in North Veracruz, Mexico, in two commercial orchards with low and high management technology. A total of 200 flowers per orchard were assessed for disease incidence every 2 days during the flowering season. Colletotrichum isolates, putatively similar to C. acutatum , were obtained from diseased flowers and inoculated to Citrus sinensis and Citrus latifolia completing the Koch's postulates. The average Area Under Disease Progress Curve (AUDPC) (625 vs. 688 days, %) and final disease incidence (Yf) (68% vs. 67%) were statistically similar ( P = 0.05) to both orchards. Epidemic rates were in the range of 0.05 to 0.16 units, with the highest variability in the high technology orchard. The total epidemic duration was 15 and 18 days for the high and low technology orchards, respectively. The highest absolute increase of disease occurred at 13 days after the beginning of flowering during the full bloom stage. The absolute increase of disease was not correlated ( P = 0.05) with nonlagged values of relative humidity (%), maximum temperature (°C) and the number of Colletotrichum spores captured on a Burkard like trap. However, 5-day lagged values of spore numbers were apparently correlated with the highest absolute increase of disease. Similarly, 3- to 5-day lagged values of number of days with at least 85% relative humidity was needed to explain the main spore peaks.