No abstract

Studies were separately conducted to determine the effects of cultivar, planting date, and fungicide usage on rice blast disease, caused by Pyricularia grisea (Cooke) Sacc. [= Magnaporthe grisea (Hebert) Barr] in Kecamatan Manggala, South Sulawesi Indonesia. The four rice varieties were IR-66, Cisantana, Cigeulis, and Filipin. The results showed that IR-66 was moderately resistant to leaf and neck blast, with the lowest percentage unfilled grains per panicle. Cisantana reacted moderately resistant to leaf blast, but moderately susceptible to neck blast. Cigeulis was moderately susceptible to leaf and neck blast, while Filipin showed a highly susceptible reaction to both leaf and neck blast, and a 31% plant population death due to the blast disease. With respect to planting dates (February 4, March 22, and May 16), plants transplanted in March had the highest leaf blast severity, neck blast incidence, and the lowest yield. Seven fungicides (four are recommended for use in rice in Indonesia: flusilazol, difenoconazole, difenokonazole+propikonazole, and carbendazim (6.2%)+mancozeb (73.8%)) and three generally used ones (menefoxam (4%)+mancozeb (64%), chlorothalonyl, and metalaxyl) which were evaluated against the rice blast disease, showed the recommended fungicides for use in rice to be more effective in suppressing blast and protecting yield, compared to the other fungicides.

Integrated management of Rice Tungro Disease (RTD) by combining the appropriate planting time and cultivar rotation has successfully controlled the disease in South Sulawesi, Indonesia. By the early 1990's, about 10 years after the management was implemented, tungro disease incidence was so low that the integrated management was no longer strictly implemented and eventually abandoned. Surprisingly however, the tungro incidence steadily decreases in the area ever since. Therefore, the purpose of the study was to elucidate why the rice tungro disease incidence decreases even when the integrated management is no longer in place. A series of studies was conducted to determine the adaptability of rice Green Leafhopper (GLH), Nephotettix virescens, colonies on different cultivars with different resistance genes against the leafhopper, tungro transmission efficiency in laboratory and in field and tungro viruses (RTBV and RTSV) detection in weeds. The results indicated that all GLH colonies had adapted to all cultivars carrying different GLH resistance genes. For each colony, there were no significant differences between the resistant cultivars and TN-1 (no GLH resistance gene) in: (1) Percent of first instars developing to the second instar nymphs, (2) nymphal development indices, (3) tungro virus transmission efficiency and (4) GLH populations. The PCR results showed that none of the weeds tested contained the rice tungro viruses. Therefore, the study results suggested that the lack of rice tungro inoculums in the weeds was the main reason why tungro incidence decreases from time to time. However, if the rice tungro viruses are reintroduced to the region, the RTD can become devastating because the GLH colonies have already adapted to all available resistance genes. Further studies should be conducted to find and incorporate new resistance genes into commercial cultivars.

One of the most devastating pests of chili pepper is the sweet potato whitefly (SPW), Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae). It sucks plant sap, emits honeydew on which sooty mold fungi grow, and transmits the pepper yellow leaf curl Indonesia virus (PepYLCIV), the most damaging viral disease of chili in Indonesia. Farmers rely mainly on insecticide to control the insect with two to three sprays in a week. To reduce the insecticide use, an integrated approach needs to be developed. Therefore, the current study evaluated the effectiveness of the integration of reflective mulch, host plant resistance, and insecticide use for managing the sweet potato whitefly on the chili pepper. In 2018, a complete randomized block design was used in three separate trials to assess the effects of mulch, cultivar, or insecticide application frequency on the numbers of whitefly eggs, nymphs, and adults. In 2019, a split-split plot design was used to evaluate the effects of the integration of mulch, cultivar, and insecticide application frequency on the numbers of whitefly eggs, nymphs, and adults. The results showed that the reflective silver mulch had significantly lower numbers of whitefly eggs, nymphs, and adults, in comparison to the rice straw mulch and bare ground treatments. Chili plants cv. Bara was more resistant than Bhaskara against B. tabaci in the field; however, in the no-choice trial, no significant difference was detected between both cultivars. Insecticide applications twice per week and once per week were equally effective in controlling the whitefly on the susceptible cultivar (Bhaskara). Overall, the integration of reflective mulch, resistant cultivar, and insecticide application every two weeks effectively suppressed B. tabaci populations on the chili pepper. This approach could substantially reduce the number of insecticide applications from twice per week (commonly practiced by chili farmers in the area) to one application only in two weeks.

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