Evaluation of Aliado Fungicide in Control of Citrus Gummosis Disease

 Effect of Aliado fungicide (Masio, Spain) with active ingredient of Mancoezbe 40%, chlorothalonil 20% and simoxanil 5% as a 65% WP formulation for control of citrus gummosis disease in laboratory, greenhouse and orchard conditions was compared with common fungicides (copper oxychloride and Bordeaux mixture in ratios of 100 and 50 g/l respectively). The growth of Phytophthora parasitica and P. citrophthora was controlled in the culture media containing the recommended doses of 15, 20, 25, 30 and 35 g/l. Results of greenhouse experiment with one-year-old sweet orange seedlings of Siavaraze (a local variety) indicated that Aliado is effective on prevention of the wound development at the doses of 25 and 35 g/l for P. parasitica and 20 and 35 g/l for P. citrophthora. The best result was obtained with painting of 15 grams per liter of the fungicide twice a year (spring and autumn) in the field assessment.

 In this study, P. parasitica and P. citrophthora were isolated from the infected soil. The fungi were stored after purification and cultivation in the test tube for the next steps. To evaluate the effect of Aliado in laboratory conditions, different doses of the fungicide containing 0, 15, 20, 25, 30 and 35 grams per liter were added to the CMA medium and distributed in petri dishes. Then, 5 mm discs were prepared from the 7-day-old pragmatic margin of the fungus-like and placed in the center of Petri dishes. After maintaining them at 24 °C for 4 days, the radial growth of mycelium was measured. In order to investigate the effect of the fungicide in greenhouse condition, seeds of Siavaraze local sweet orange as a sensitive variety was prepared and treated with 0.5 percent sodium hypochlorite solution and cultivated in a soil composition disinfected with water vapor in a controlled greenhouse of Citrus and subtropical Fruit Research center. Evaluation of the effect of fungicides was carried out after seedlings reached about 20 centimeters. For staining treatments, 24 one year old seedlings of Siavaraze were used. First, at 15 cm above the surface of the soil, a part of the bark was removed from the trunk and discs of the same size from the fungi-like colonies were placed instead. In the control plants, the culture medium without mycelium was placed on the surface of the wood. To evaluate the treated seedlings, about 40 days after application of the fungicides, the size of the new wound was calculated. To study the effect of Aliado in orchard condition, 24 trees of 12 years old with Bakraee and Lime rootstocks infected with trunk gummosis in Kerman (Jiroft) and Fars (Jahrom) provinces were used in a randomized complete block design with 8 treatments in 3 replications. The wound of the trunk marked and bark of the infected area was gently scratched and painted by a brush with the same treatments and doses of the laboratory test. Six months after application, the size of the new wound was recorded. The analysis of variance and the mean comparison were performed based on MSTATC statistical program and the Tukey's test.

 Laboratory studies showed that Aliado fungicide completely prevented the growth of fungi-like in the recomended doses of the company. Under greenhouse conditions, painting of Aliado with 25 and 35 grams per liter for P. parasitica and 20 and 35 grams per liter for P. citrophthora have been effective in stopping the development of stem wounds. This research was also conducted in field conditions in the orchards with gummosis symptoms in Kerman and Fars provinces. In the orchard condition, two times application of all treatments containing Aliado fungicide (even a dose of at least 15 g/l) was effective. The results of the experiment are in agreement with those of the world's researchers, which have reported the use of fungicide as an effective method for controlling phytophthora fungus-like of gummosis. Therefore, in citrus cultivation areas of the country, especially the southern provinces, where the climatic conditions are favorable for the activity of the fungi-like, treatment of the crowns of citrus trees with Aliado in the spring and the autumn with the minimum proposed dose of the fungicide is recommended. Observations showed that all treatments of Aliado are effective by drying the gum in controlling disease progression through disinfection. In some treatments, the emergence of gum in the new places was observed with a little distance from the previous wounds. It can be because the effect of fungicide has decreased after a few months. In climatic conditions of the southern regions of the country the fungi-like are active throughout the year. So the use of fungicide in spring and autumn is recommended. The use of Aliet fungicide in two doses of 160 and 200 g in 100 liters of water had a protective effect less than one year.