Population dynamics of Epicoccum nigrum, a biocontrol agent against brown rot in stone fruit.

AIMS: To study the population dynamics of Epicoccum nigrum on peaches and nectarines and to enhance its colonization on fruit surfaces to improve its biocontrol efficacy against brown rot. METHODS AND RESULTS: Twelve surveys were performed to study E. nigrum populations and their effect on the number of the pathogenic Monilinia spp. conidia in peach orchards in Spain and Italy between 2002 and 2005. Fresh conidia and five different formulations of E. nigrum conidia were applied three to six times to peach and nectarine trees from full flowering to harvest. The size of the E. nigrum populations was determined from the number of colony-forming units and conidial numbers per flower or fruit. Treatment with all conidial formulations increased the size of the indigenous conidial population on peach surfaces. CONCLUSIONS: Formulations of E. nigrum having high viability are most effective against conidia of the pathogen when applied at pit hardening and during the month immediately before fruit harvest. SIGNIFICANCE AND IMPACT OF THE STUDY: Application of an E. nigrum conidial formulation decreased the number of conidia of Monilinia spp. on fruit surfaces during the growing season to the same extent as fungicides.

Penicillium frequentans population dynamics on peach fruits after its applications against brown rot in orchards.

AIMS: The study provides useful information on the temporal population dynamics of the biological control agent, Penicillium frequentans, after its applications against brown rot in orchards. METHODS AND RESULTS: Population dynamics of P. frequentans were studied on peach flower and fruit surfaces after different field treatments. Eight experiments were carried out in commercial peach orchards in Spain, over four growing seasons from 2002 to 2005. Six different formulated P. frequentans conidia were applied four to six times from blossom to harvest and P. frequentans population sizes were monitored using conidial numbers and colony forming units (CFU) per flower or fruit. A consistent population of P. frequentans, ranging from 10(5) to 10(6) number of conidia or 10(3) to 10(4) CFU of P. frequentans per flower or fruit, was obtained. Colonization of peach surfaces by all P. frequentans formulation are similar and it appears to follow a general pattern: (i) higher colonization of fruits at preharvest than on the flowers at bloom; (ii) high populations just after treatments, especially after preharvest treatments; and (iii) a slight decline between treatments, especially in cool and moist springs. The exponential model was the most appropriate for fitting and comparing the P. frequentans dynamic populations on peaches and nectarines over time. The linearization of the P. frequentans population curve was essential to determine dynamic population and for population levels forecast. A positive relationship between number of blossom and preharvest applications, temperature, relative humidity and dynamic of P. frequentans population applied on peaches was studied using a multiple regression model. CONCLUSIONS: Blossom and preharvest applications were the most important spray times for obtaining the highest population of P. frequentans on peach surfaces. SIGNIFICANCE AND IMPACT OF THE STUDY: The study provides useful information on dynamic P. frequentans population and its effects on the brown rot biocontrol.