Field evaluation of Bacillus subtilis (QST 713 strain) for the control of mango anthracnose

The study was conducted in a mango orchard at Brgy. [village] Tanauan, Tanza, Cavite [Philippines] from October 2003 to March 2004. The experiment was set-up in RCBD [randomized complete block design] with 4 replications. The test chemicals were applied five times after flower induction was done and when about 50% flowering intensity was observed on sprayed mango trees. The first spray application was done at 12 days after flower induction (DAFI). The second, third and fourth were applied at 22, 38 and 55 DAFI. The last spray application was done at 101 DAFI. The volume of spray was 40-50 liters/tree. The product was tank-mixed with insecticide and was sprayed on the tree using a power sprayer. The trees were managed according to the cultural practiced by the owner, except, for fungicide application. Untreated control was sprayed with insecticides only. The study was conducted to evaluate the efficacy of Virtuoso 10 AS (Bacillus subtilis QST 713 strain) for the control of mango anthracnose in comparison with conventional systematic fungicides. The results obtained from the trial showed that based from the untreated control, Virtuoso 10 AS treated trees did not show any phytotoxic effect on leaves, flowers and fruits of mango. Except for the presence of anthracnose caused by Colletotrichum gloeisporiodes and scab caused by Elsinoe mangifera on mango inflorescence and fruits, there was no other damaged or symptoms observed on the sprayed mango trees and fruits than can be attributed to the spray application of Virtuoso 10 As (Bacillus subtilis QST 713 strain). Plant vigor before and after the spray application was normal and the trees were healthy and vigorous. The study also showed that Virtuoso 10 AS (Bacillus subtilis QST 713 strain) exhibited excellent activity in suppressing or reducing the severity of anthracnose caused by Colletotrichum gloeisporiodes. With the same number of spray applications with selected conventional systemic fungicides, the performance of Virtuoso 10 AS (Bacillus subtilis QST 713 strain) at all rates were comparable to the given standards in reducing blossom blight. Virtuoso 10 AS (Bacillus subtilis QST 713 strain) also exhibited excellent performance in reducing anthracnose infection on harvested fruits. On the other hand, with Elsinoe mangifera, the performance of Virtuoso 10 AS (Bacillus subtilis QST 713 strain) at all rates were not as effective as the given conventional systematic fungicides. Fruit set at 45 DAFI was significantly higher on Virtuoso 10 AS (Bacillus subtilis QST 713 strain) treated trees as compared to the untreated control. Fruit retention count at 60 and 75 DAFI on Virtuoso 10 AS (Bacillus subtilis QST 713 strain) treated trees were also significantly higher than the untreated control and comparable to the given standards.