Alternative approaches for the management of sigatoka disease of lakatan banana: small plot evaluation of oriental herbal nutrient (OHN), virgin coconut oil (VCO) and OHN-VCO combination for the control of sigatoka disease of lakatan banana

Banana remains to be the most important fruit crop in the Philippines and ranks among the country's top exports. Diseases, however, markedly reduce production. Among the banana diseases, black sigatoka, also known as black leaf streak (BLS), causes significant reduction in leaf area resulting in premature ripening and yield losses of 50% or more. The demand for a toxic-free chemical to control sigatoka led Dionio (University of Southeastern Philippines) to validate the efficacy of OHN, VCO, and their combination for sigatoka control in lakatan using small plot test. Two ratings were used in the study, the youngest leaf infected (YLI) and youngest leaf spotted (YLS). YLI is the leaf position within the sample banana plant where the earliest visible streak symptom (stage 2) was detected. This was recorded every five days. YLS, on the other hand, is the youngest leaf position within the sample banana plant where early spot (stage 4) was detected. Traditionally prepared VCO applied at 5L/ha had significantly lowest youngest leaf infected value of 3.93 comparable to Tridemorph, a systematic fungicide, VCO-OHN combination (50 mLI: 40 mL per liter solution), Banole, OHN alone, and multipurpose detergent (MPD). Mancozeb, a contact fungicide had the significantly highest YLI with mean of 4.33. Untreated plants have lowest YLI value of 3.50. A spray interval of more than 10 days for systematic chemical like Tridemorph and oils like Banole may be recommended to reduce possible phytotoxic effect on plants. On the other hand, shorter interval may be recommended for OHN to provide significant protection to emerging leaves. VCO-sprayed a mean YLS of 5.7 comparable to Banole, Mancozeb, and VCO-OHN combination. Highest YLS of 6.73 was observed in Tridemorph-sprayed plants. OHN- and MPD-sprayed plants have comparable YLS with untreated plants. VCO and VCO-OHN combination can effectively slow down BLS development as shown by significantly higher YLS values compared with untreated plants. OHN alone, on the other hand, did not have a significant effect on YLS. VCO and VCO-OHN combination can delay onset of BLS until 32.97 and 32.7 days, respectively, and comparable with the incubation period using Tridemorph (33.40 days), Banole (33.2 days) and MPD (32.07 days). The use of Mancozeb resulted in the longest incubation period of BLS at 36.63 days. The transition period, or the number of days visible streaks turned into spots was longest using Tridemorph at 26.8 days, followed by Banole (20.37 days) and VCO (19.07 days). The lowest transition period, which contributed to the lowest YLS value, was obtained using OHN at 15.1 days. VCO (50 mL-L-1), VCO-OHN (50 mL:40 mL-L-1) combination and Tridemorph exhibited phytotoxic effects on sprayed lakatan banana plants, which were manifested as rusty brown coloration on lower leaves. Results of the study showed that traditionally prepared VCO and VCO-OHN combination delayed black leaf streak development as shown by high YLI and YLS values and longer incubation and transition periods. VCO at the rate of 5L/ha was phytotoxic in Lakatan banana plants, while OHN was inferior in the trial conducted.