Document Type : Research Article
Authors
1
Assistant Professor, Iranian Research Institute of Plant Protection, Agricultural Research, Education and Extension Organization (AREEO), Tehran, Iran
2
Associate Professor of Plant Protection Department, Agricultural and Natural Resources Research and Education Center of Golestan, AREEO, Gorgan, Iran
3
Assistant Professor of Plant Protection Department, Agricultural and Natural Resources Research and Education Center of Kokyluye and Boyer Ahmad, Kokyluye and Boyer Ahmad, Iran
Abstract
Introduction
Scab disease of apple caused by Venturia inaequalis is one of the most important diseases of apple in the world and Iran. Especially in areas with wet and cold weather its damage reach more than 70%. Apple scab results in symptoms on most upper plant parts, notably leaves and fruit. Petioles, flowers, sepals, pedicels, young shoots, and bud scales can also become infected. Apple scab infections are initiated in early spring on emerging and young leaves. The Mills table relates leaf wetness duration and temperature to determine the likelihood that conidial infection will occur. For example, at an average temperature of 18°C (65°F), light infection will result if leaves remain wet for 9 h. Lesions can produce conidia after 9 days if the temperature averages 18°C (65°F), but not until 17 days if the temperatures are lower, averaging only 8°C (49°F).
Materials and Methods
The experiment was conducted in apple orchards located in Yasuj, Bojnourd and Karaj which had a history of apple scab. The experimental design was a randomized complete block design (RCBD) with 8 treatments and 4 replications. The control treatments included plots without any spraying and plots sprayed with water. The remaining treatments involved the application of specific treatments at three different stages. The first spraying was done at swelling of leaf buds time, the second spraying after fall leaves, and the third spraying 14 days after the second spray. 30 days after observing the first symptoms of the disease in the controls, samples were taken from the leaves and fruits to evaluate the percentage of the disease density and severity of the disease. The data obtained for disease incidence and severity were analyzed using statistical software, such as SAS, and the means of these traits were compared using Duncan's multiple range test at a significance level of one percent. This test helps determine significant differences between the treatment means.
Results and Discution
The analysis of variance conducted on the data obtained from the evaluation of treated trees revealed a statistically significant effect of the treatments on reducing the percentage of disease severity and disease incidence. Result showed that, there are significant differences between treatments and controls in all three provinces (P = 5%). Mean comparisons of the treatments showed that, all fungicides caused a significant decrease in the severity and incidence of disease infection percent compared to controls. The results of three provinces showed that new fungicide Luna Sensation 500® SC 0.4 and 0.6 ml L-1 and Flint® 50% WG 0.2 ml L-1 during three times spraying is very effective on controlling of apple scab. In Kohghiloyeh and Boyerahmad, 0.4 and 0.6 ml L-1 of Luna Sensation had the best efficiency compared to other treatments. The severity of disease was lower than control about 96 percent in leaves and 98 percent in fruits. Also, incidence of disease in fruit and leaf of these treatments were lower than the other treatments. In North Khorasan province Flint 0.2 ml L-1 and Luna Sensation 0.4 compared to other treatments was more effective in controlling the disease severity and approximately 75 percent compared to controls reduced disease severity on fruits. Also on leaves Luna Sensation 0.4 were effective approximately 80 percent. In terms of disease control on fruit, there were no significant differences between all fungicide treatments except benomyl. Disease incidence on the leaves treated with all three concentrations of Luna Sensation and 0.2 ml L-1 Flint was lower than other treatments. In Alborze province, Luna Sensation 0.4 and 0.6 ml L-1 and Flint 0.2 ml L-1 had the best efficacy and nearly 100 percent decrease severity and incidence of disease in leaves in compared with controls. The results of three provinces showed that new fungicide Luna Sensation 500® SC 0.4 and 0.6 ml L-1 and Flint® 50% WG 0.2 ml L-1 during three times spraying is very effective on controlling of apple scab. Also, the results showed that Luna Sensation fungicide can control apple scab disease on Golden Delicious and Red Delicious and The type of cultivar has no effect on the efficacy of the fungicide. Results show that Luna Sensation 500® SC 0.4 is an effective fungicide to control apple scab and can be used in apple orchards as a part of integrated pest management program. The management of apple scab disease in the world usually requires multiple sprayings, from the greening stage of the branches to harvest. Since V. inaequalis has a high risk of developing resistance to fungicides, the alternating use of effective fungicides from different groups and with different mechanisms of action or the use of fungicides with multiple mechanisms of action in disease management programs are necessary to prevent resistance. The new fungicide Lunasenish® SC 500, which is composed of 21.4% trifloxystrobin, 21.4% flupiram and 57.2% related substances, is a systemic fungicide with a wide range of effects.
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