3.1.10
COMBINATION OF REDUCED FUNGICIDE DOSE AND ANTAGONISTIC PSEUDOMONAS FLUORESCENS STRAIN EPS288 FOR CONTROL OF BLUE MOULD ROT DURING POST-HARVEST OF APPLE AND PEAR

E MONTESINOS, JL JUAN, J FRANCES and A BONATERRA

Institute of Food and Agricultural Technology-CeRTA, University of Girona, Avda. Lluis Santalo, s/n, 17071 Girona, Spain

Background and objectives
A significant source of fruit losses during post-harvest of apple and pear in production areas of Spain is due to infections by Penicillium spp. (frequently Penicillium expansum) and other fungal rots. Formerly, control of fruit rot diseases was achieved by application of chemical treatments (combinations of fungicides or calcium salts). However, restrictions in pesticide use and consumer demand have led to an increasing tendency to use biological control microbial agents to protect apples and pear from fungal rot. However, in practice biological control has some problems of inconsistency or failure under certain conditions of application, due to the lack of a wide spectrum action, or to limited growth of the biological control agent because of the presence of inhibitory levels of some pesticide residues. The aim of this work was to evaluate, in pilot trials in commercial warehouses, a combined strategy of fungal rot post-harvest control consisting of reduced fungicide dose and biological control with antagonistic bacteria.

Materials and methods
The sensibility of antagonistic Pseudomonas fluorescens strain EPS288 to 20 pesticides used in apple and pear production, including insecticides, acaricides, fungicides and bactericides, was characterized by an agar incorporation test. Control trials of blue mould rot were performed with fruits collected from 11 commercial orchards of Golden Delcious apple conducted under integrated production practices, and from seven orchards of Passe Crassane and Conference pear. The experiments were done during 3 years (1995, 1996 and 1997). Fruits were harvested from orchards using standard criteria accepted in the area and several quality parameters were analyzed. Before storage, fruits were wounded and submitted to the following treatments: (i) non-treated, (ii) fungicide (imazalil plus folpet) at the recommended standard dose, (iii) P. fluorescens strain EPS288, and (iv) combined P. fluorescens EPS288, 25% of the recommended fungicide dose. Then fruits were inoculated with P. expansum and stored at 0C under controlled atmosphere (CA) or Ultra-LowOxigen (ULO) for 6 months in two warehouses near Girona.

Results and conclusions
The strain EPS288, a natural non-genetically modified P. fluorescens isolated from corn, was only susceptible to standard doses of copper derivatives and antibiotics such as streptomycin or kasugamycin, and was resistant to benomyl, imazalil and folpet fungicides.

The trials performed with apple and pear fruits from commercial orchards of wide diverse origin and quality, and stored in commercial warehouses, showed that biological control of P. expansum with P. fluorescens EPS288 was significant but less efficient than fungicide alone at standard dose. However, combination of the biological control agent with 25% reduction of fungicide was similarly efficient to the standard fungicide alone.

References
1. MontesinosE, Bonaterra A, Ophir Y, Beer SV, 1996. Phytopathology 86, 856-863.
2. Francos J, Bonaterra A, Juan JL, Vilardell P, Montesinos E, 1997. Acta Horticulturae 448, 35-41.
3. Juan JL, Camps F, Francos J, Montesinos E, 1997. Acta Horticulturae 448, 42-45.