Environmental factors influencing the development of black leaf streak (Mycosphaerella fijiensis Morelet) on bananas in Puerto Rico.

Authors: CHAVARRIA-CARVAJAL, JOSE - University Of Puerto Rico; MACCHIAVELLI, RAUL - University Of Puerto Rico; MARENGO, JOSE - University Of Puerto Rico; Irish, Brian; HERNANDEZ, EVELIO - University Of Puerto Rico

Submitted to: Journal of Agriculture of the University of Puerto Rico
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/8/2015
Publication Date: N/A
Citation: N/A

Interpretive Summary: Environmental factors play important roles in the development of disease epidemics in agricultural productions systems. In commercial banana production, factors such as temperature, precipitation, humidity and solar radiation all influence the development of foliar fungal diseases. However, it is not clear how these environmental factors affect bananas (positively/negatively) and to what extent the factors influence disease in Puerto Rican production fields. Research was carried to determine which factors had the most influence on disease epidemics and how each affected crop yields. Data was collected on susceptible industry standard ‘Cavendish’ cultivar banana plants in a field experiment over a single cropping cycle. Results indicated that increased precipitation, humidity, temperature and solar radiation all positively correlated with disease progression. Temperature was the single most important factor in disease development. This is the first epidemiological experiment conducted on bananas in Puerto Rico and, coupled with future research, can lead to the development of local plant disease prediction models. The developed models then can aid farmers in the timing and rate of fungicide applications and in disease management strategies.

Technical Abstract: The effects of environmental factors on the development of black leaf streak (BLS) were studied in Puerto Rico under field conditions. Environmental factors evaluated included temperature, relative humidity, rainfall and solar radiation. Their effect on BLS was determined by recording the youngest diseased leaf, the youngest spotted leaf as well as a by calculation of the disease severity index. Results from the field evaluation showed that BLS epidemic fits a logistic model with a sigmoidal curve. Among the environmental factors measured, temperature was the most important factor associated with disease progress. Maximum, minimum and average temperatures were strongly correlated with severity index and showed Spearman's coefficients of 0.67, 0.66, and 0.68, respectively. The results showed that solar radiation contributed positively to increased disease severity index, indicating that at high luminous intensity severity index increases. Rainfall and relative humidity played an important role in the development of the disease, both variables showed positive correlations with the disease severity index. Severity index reached values near 100% after flowering. Disease severely affected the crop yield of ‘Grand Naine’ (Musa acuminata, AAA), harvesting bunches with 137.25 fruits, 8 hands and 18.67 Kg for an average of 136.03 g per fruit. If only the bunch weight were taken into consideration, a yield reduction of 61% was observed. However if the effect of the disease on fruit quality was considered, the reduction on yield reached 100%.