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| Author: | E. Gheorghiu |
Abstract:
The wide distribution of apple proliferation and its high rate of appearance at the age at which the trees bear fruits associated to a decrease of the biological potential, resulting in serious economic implications, prompted the present studies.
- Physical control 1.1. Hot air treatments at 38°C applied for 2 days to 3 year-old-diseased trees had a radical therapeutic effect, the mycoplasma present in the buds fit for grafting being inactivated.
The heat probably induced a hormonal disorder, since the proportion of set grafted buds was lower than in the untreated check; 1.2. Hot air treatments at 50°C applied for 2 hours to cuttings had a total therapeutic effect since 55% or the buds were set; 1.3. Immersion of the branches in hot water at 50°C for 2 hours was totally harmful; 1.4. X- and UV-rays determined intermediate effects.
- Chemical treatments 2.1. The most effective low-toxicity chemotherapeutants were in decreasing order : Pyoctamin 1%0, Chloramphenicol 1%0, Penicillin and Tetracyclin with a therapeutic effect of 100% and rate of successful grafting of 55%, 44%, 35% and 20%, respectively.
Streptomycin proved totally phytotoxic; 2.2. Four out of the 9 chemicals tested for 2 years in fruit bearing orchards on the same trees showed a wide range of activity, systemic and curative effects, and high translocation ability, e.g.
Benlate 0.1%, Derosal (Hoe 17 411 OF) 0.075%, Topsin M 0.1% and Kasumin 0.2%.The differences between the rate of disease differentiation of the variants receiving chemical treatments and the untreated check were highly significant negatively; 2.3. Mineral fertilization with NPK applied in 16 quantitative variants did not attenuate the disease but, on the contrary, enhanced the activity and concentration of the pathogen in the host plant.
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