![]() ![]() However, the level of control might have been more effective in ON if treatment applications were initiated earlier in the season. Four applications of PC failed to significantly reduce shoot growth more than two applications in either location. Results indicate that PC applications are most effective at the beginning of the season, when relative growth rates were greatest in eastern Canada. Seasonal patterns of extension shoot growth among cultivars in both locations were also compared. Orchard experiments were conducted on mature non-bearing apple (Malus x domestica Borkh.) trees to determine the efficacy of prohexadione-calcium (PC), formulated as Apogee® for shoot growth control on six cultivars grown in Ontario (ON) and one grown in New Brunswick (NB), Canada. amylovora on floral parts by antibiotics, chemical compounds, natural substances or biological control agents, are also discussed. Management programs, aiming at the suppression of E. Flower age, stigma morphology and longevity, the size of epiphytic bacterial population, morphology of the hypanthium, anatomy of the nectary, dynamics of nectar secretion, as well as the volume, concentration and composition of the nectar are discussed in detail, comparing traits of susceptible versus tolerant apple and pear cultivars. The paper reviews various floral traits that may play a role in the onset and progression of the infection. Under favorable conditions, nectar provides a rich medium for growth, which allows bacterial invasion of tissues through the stomata of the nectary. Epiphytic bacterial populations develop on the stigma, from where the pathogen colonizes the hypanthium, aided by moisture. Commercially important fruit tree species such as apple (Malus domestica) and pear (Pyrus communis) are also affected by the disease. All in all, prohexadione-Ca will be of great value as a component for a new control strategy against fire blight, which, in many countries, has to be independent of the disputed use of antibiotics.Įrwinia amylovora, the causative agent of fire blight, colonizes primarily the flowers of the sub-family Maloideae. Combinations with other non-antibiotic preparations could lead to a sufficiently reliable control. However, limitations are still obvious in using prohexadione-Ca against blossom blight. The simultaneous control of excessive shoot growth and shoot infections by fire blight is seen as a major advantage of using prohexadione-Ca in pome fruit trees. In trials on shoot infections, prohexadione-Ca-treated trees were much better protected than those treated with streptomycin or kasugamycin. After pre-treating trees with prohexadione-Ca, blossom infections could be controlled at the same degree of activity as with regularly applied streptomycin. Indoor experiments with apple trees and artificial inoculation confirm effects both against blossom and shoot infections. Prohexadione-Ca represents a considerable alternative to antibiotics for the control of fire blight (Erwinia amylovora) in pome fruit trees. Due to less acrotony, a higher number of lateral buds was enabled to grow, which led to improved feathering. However, more severe reductions in shoot length additionally involved lowered numbers of internodes. Moderate reductions of shoot growth were almost entirely due to shortening of the internodes. 'Red Boskoop', 'Braeburn', 'Freedom', and 'Fuji Nagafu 6'. 'Elstar', 'Golden Delicious', 'Jonagold', 'Rubinette', 'Šampion' and some of their mutants were more responsive than cvs. In apples, applications at a few centimetres of new shoot growth led to clear reductions in vegetative activity in all cultivars tested. Prohexaclione-Ca is a new, multi-functional plant bioregulator for use in pome fruits.
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