Potential of certain salts and fungicides to control postharvest gray mould (b. cinerea)‎ of strawberry

Abstract EN

Effect of two fungicides (i.

e.

iprodione and cyprodinil+flydioxonil mixture) and two salts (sodium bicarbonate, SBC, and sodium benzoate, SBO) were evaluated separately or in mixtures in laboratory experiments as well as under field conditions against Botrytis cinerea instant of the fruit gray mould of strawberry.

All tested salts and fungicides as well as their mixtures significantly decreased the radial growth of B.

cinerea in vitro.

Complete inhibition of radial growth was obtained with SBC at 2.0 and1.0 g/100ml.

Also, high reductions were obtained with SBC at lower concentrations.

The fungicide iprodione at 500 mg/L completely inhibited radial growth of B.

cinerea, while complete inhibition was obtained with cyprodinil+flydioxonil at lower concentration (10 mg/L).

Mixing the tested fungicides with salts increased their inhibition effect on B.

cinerea growth at lower fungicide concentrations.

iprodione at 0.1 mg/L mixed with SBO at 1g/100ml completely inhibited radial growth.

Also, cyprodinil+flydioxonil at 0.1mg/L mixed with SBC at 0.2 g/100ml completely inhibited radial growth of B.

cinerea while 0.001mg/L cyprodinil+flydioxonil fungicide with SBO at 2.0g/100 completely inhibited radial growth.

On the other hand, the field experiments showed that all treatments with the tested salts and fungicides significantly decreased postharvest Botrytis gray mould on fruits harvested 1, 3, 7, 10 and 15 days after treatments and stored at 5˚C for seven days.

However, the treatment with 50% cyprodinil+flydioxonil + SBC 2% was the most effective and decreased mean percentage of infection to 4% compared to 23.86 % for the untreated control.

This was followed by 50% iprodione +SBC 2% , 25% iprodione + SBC and 25% cyprodinil+flydioxonil + SBC 2% , and cyprodinil+flydioxonil, alone, and iprodione, alone, with percentages of infection being 7% , 8% , 8.5% , 8.5% , and 9% , respectively, while (SBC 2% , alone) treatment showed the least effect with 12.93 percentage of infection.

Meanwhile, positive strong correlations (r = 0.981 to 0.943) were revealed between Infection (% ) and harvest interval periods with two salts mixed with iprodione and cyprodinil + flydioxonil after stored at 5˚C.

Also, the enzyme assay revealed that increases in the activity levels of pectolytic and cellulytic enzymes produced by the fungus were associated with high fruit rots incited by B.

cinerea.

Meanwhile, residues of all tested fungicides in treated strawberry fruits decreased with decreasing fungicide concentrations in the salt + fungicide mixtures.

cyprodinil (25% ) + SBO, and cyprodinil (25% ) + SBC treatments exhibited the lowest residue values being 1.420, and 1.680 mg/kg fruit one hour after treatment while the other treatments showed higher residue values while the highest was recorded for iprodion at recommend dose being 29.81 mg/kg fruit.

However, fungicide residues decreased with increasing time after preharvest treatments.