Efficacy of alternatives to antibiotic chemicals for the control of fire blight of pears

Abstract

The efficacy of various chemicals as alternatives to antibiotics for the control of fireblight (Erwinia amylovora) on pear trees was tested. The chemicals were applied in two ways. In 1999 and 2000, preselected pear twigs (80-90% bloom stage) were sprayed once either preventively 1 day before inoculation or curatively one or three days after artificial inoculation with pathogen concentrations of 10 5 and 10 7 cfu ml -1 . In 2000 and 2001, whole trees were sprayed 2 and 4 days before artificial inoculation of the flowers. From the incidence of diseased flowers it appeared that Bion (50% benzothiadiazole) at 0.2 g litre -1 H 2 O and Aliette (80% fosetyl-Al) at 2.5 g litre -1 H 2 O showed considerable preventive action by eliciting systemic acquired resistance mostly when they were applied in the whole trees. However the best control was achieved with the antibiotic Agrept (20% streptomycin) at 0.5 g litre -1 H 2 O. This showed both preventive and curative action. Kocide (77% copper hydroxide) at 0.9 g litre -1 H 2 O, Dentamet (citric acid in chelate) at 1.5 ml litre -1 H 2 O, Bactosan (an extract from the plant Pongamia pinnata) at 3.0 g litre -1 H 2 O and Bion at 0.1 g litre -1 H 2 O, showed preventive action, but only when the inoculum concentration was low.

Screening Molecules for Control of Citrus Huanglongbing Using an Optimized Regeneration System for ‘Candidatus Liberibacter asiaticus’-Infected Periwinkle (Catharanthus roseus) Cuttings

“…There are other examples of chemically managing bacterial disease in perennial fruit, such as fire blight (43). Although the epidemiology of fire blight and citrus HLB are different, treatment with an antibiotic has been used as part of the control strategy for this disease of pome fruit for many years (39).…”

Determination of application time for chemical control of fire blight disease in pear varieties

“…Thus trees will be protected for a longer time than with the usual bactericides. Even so it would be worthwhile to determine the optimum time of application (Tsiantos et al, 2003). Although not more effective than streptomycin they should have a role in Integrated Pest Management as they can reduce the applications of streptomycin and thus lessen the possibility of development of streptomycin-resistant strains.…”

Extensive efficacy tests of non-antibiotic fire blight control agents

“…Specific characteristics of future control agents are a high efficacy, "non-antibiotic" properties in terms of not used clinically to protect human or animal health, security for the environment, consumers and producers, no phytotoxic effects (plant and fruit), and potential use after hail storm damage. Despite the efforts put into this search for alternatives, no agent with the same efficacy and characteristics as streptomycin could be found until now (Tsiantos et al 2003;Adaskaveg et al 2008). Experimental designs were not uniform in these studies -e. g. designs with natural (Adaskaveg et al 2008) or artificial (Tsiantos et al 2003) inoculation exist and their statistical analyses vary greatly.…”

“…Despite the efforts put into this search for alternatives, no agent with the same efficacy and characteristics as streptomycin could be found until now (Tsiantos et al 2003;Adaskaveg et al 2008). Experimental designs were not uniform in these studies -e. g. designs with natural (Adaskaveg et al 2008) or artificial (Tsiantos et al 2003) inoculation exist and their statistical analyses vary greatly. A direct comparison of results has therefore to be viewed critically.…”