Anthracnose caused by Colletotrichum gloeosporioides and Colletotrichum acutatum andrnGummy stem blight caused by Didymella bryoniae (anamorph Phoma cucurbitacearum) arernamong the most important diseases of fruit and cucurbits. Currently, the control of fruit andrnvegetable diseases relies mainly on the use of synthetic fungicides. Elucidating non-chemicalrncontrol methods to reduce postharvest decay is becoming more important. This studyrninvestigated biological based approaches to controling these diseases. The first objectives of thisrnstudy were to analyze morphological, physiological and molecular methods in the differentiationrnof Colletotrichum isolates obtained from banana, mango and papaya fruits and to evaluate thernbiocontrol potential of antagonistic bacteria, yeasts and fungal isolates to manage anthracnoserndisease of banana, mango and papaya during storage. In the first phase, a phenotypic analysis ofrnColletotrichum isolated from banana, mango and papaya were carried out to identify the speciesrnresponsible for anthracnose disease on these hosts. A total of 45 isolates from three hosts werernused. The overall similarity among different isolates of Colletotrichum was determined usingrncultural characteristics. According to the results fungal isolates could be divided in to 12 distinctrngroups based on morphological similarity. Subsequent identification based on ITS sequence leadrnto the identification of Colletotrichum isolates as C. acutatum and C. gloeosporioides. Isolatesrnfrom mango were C. gloeosporioides while isolates from banana and papaya was C. acutatum.rnFurther, the study confirmed the cross infection potential of Colletotrichum isolates and absencernof host specificity. Effect of different temperature, pH level, culture media, light intensity,rncarbon and nitrogen sources were tested against the growth of C. acutatum and C.rngloeosporioides. Results indicated that the growth of these isolates varied with the differentrnenvironmental and nutritional conditions tested.rnThe second phase of this study was conducted to isolate, screen and identify indigenousrnmicroorganisms found on fruit surfaces in order to find a suitable biocontrol agent againstrnpostharvest fruit anthracnose caused by C. gloeosporioides and C. acutatum. Bacteria, yeast andrnfungal isolates recovered from leaf and fruit surfaces of banana, mango and papaya were testedrnIn vitro and In vivo against C. gloeosporioides and C. acutatum. The microbial antagonistsrninhibited mycelial growth in the dual culture assay and conidial germination of C. acutatum and C. gloeosporioides isolates in vitro. Studies were carried out to analyze the ability of thernantagonists to produce extracellular enzymes on an amended solid media. Fourteen (14) isolatesrnused produced cellulose and chitinase on amended media but only four isolates showedrnglucanase pectinase and protease activity on solid media. Additional experiments werernconducted to extract and determine the nature of antifungal substances produced by antagonistsrnthat were inhibitory towards Colletotrichum isolates. Microbial antagonist isolates differ in theirrnpreference of culture media. The results of In vivo experiments under artificial infectionrnconditions showed that suspensions containing unwashed cells of antagonists provided thernhighest levels of inhibition of anthracnose, while the washed cell suspension and autoclavedrnculture filtrates provided less protection against the disease after 30 d. Nineteen (19) differentrnantagonists were evaluated on their own and in combination with fungicide and hot water forrntheir ability to reduce postharvest fruit anthracnose diseases in vivo under natural infectionrnconditions. Integrating fungicides or hot water with antagonists controlled anthracnose morerneffectively than fungicide control. Nine antagonists were more effective than other isolates in therncontrol of postharvest anthracnose when fruit were treated under natural infection conditions.rnAfter phenotypic and molecular analysis, the bacterial isolates were identified as sixrnPseudomonas, three Bacillus and a Paenibacillus species. The Pseudomonas and Bacillus strainsrncan neither be sufficiently re-solved by MALDI-TOF MS nor by 16S rRNA gene sequencernanalysis. The most effective yeast (M-23-L-1) and filamentous fungal (M-30-F-2) isolates werernidentified as Candida rogousa and Trichoderma longibrachiatum, respectively. This experimentrnidentified six Pseudomonas and three Bacilli antagonist isolates as novel strains to be used asrnbiological control agents against anthracnose of tropical fruits.rnThe second objectives of this study were to characterize populations of Didymella bryoniae fromrncommercial watermelon and other cucurbit hosts from different parts of the USA on the basis ofrntheir biological and molecular diversity and to evaluate the effect of tiadinil and two thymolbasedrnformulations against D. bryoniae and Gummy Stem Blight (GSB) development. In the firstrnphase, morphological characteristics and rDNA Internal Transcribed Spacer (ITS) sequencesrnwere analyzed to identify the causal organism of this disease. Thirty five isolates of Didymellarnspp. and Phoma spp. associated with GSB on watermelon, canary melon, muskmelon and squashrnfrom Florida and Georgia were characterized based on morphology on culture media, pathogenicity assays and genetic characterization using ITS sequence analysis. All the isolatesrnwere pathogenic on watermelon cv. Melody, but to a varying degree. RAPD and ITS sequencernanalysis indicated genetic variation between the isolates. The ITS region analysis showed thernpresence of two isolates, DB-05 and DB-33, which showed a higher similarity to D. bryoniaernisolates from China. This is the first description of an isolate with this unique sequence in Floridarnand Georgia. The present study brings insights into the current genetic profile of D. bryoniaernisolates in Florida and Georgia, and its similarity with international isolates.rnDuring the second phase, direct antifungal activity of tiadinil and the effect of two-thymolrnformulations on D. bryoniae were evaluated in vitro. All test materials used in the study affectedrnfungal growth, with tiadinil at 10 ppm and thymol-based formulations at 0.1 ppm significantlyrn(P 0.05) reducing mycelial growth, conidia germination and germ tube elongation. Foliarrnapplication of tiadinil (before and after inoculation) on artificially infected watermelon seedlingsrnat 10 ppm significantly reduced the disease severity compared to the untreated controlsrn(P 0.05). The disease severity on seedlings treated with tiadinil at 3000 ppm was statisticallyrncomparable to chlorothalonil control (P 0.05). Plants with foliar applications of tiadinil at rn1000 ppm (before pathogen inoculation) had significantly lower disease severity than plants withrndrench application (P 0.05). Foliar application of tiadinil was affected by chemicalrnconcentration and frequency of application. Thus, based on this study, it is prudent to say thatrntiadinil and thymol-based formulations are potential materials for use in watermelon productionrnfor effective GSB disease suppression.rnThis study represents a novel report dealing with the biocontrol of anthracnose in banana, mangornand papaya fruit by the application of possibly new antagonist bacterial strains and a yeastrnisolate. It strongly recommends the use of a combination of biological control agents withrncommercial treatments as a safe and effective disease management option against the postharvestrnanthracnose of tropical fruits. The study also highlighted the possible utilization of tiadinil andrnthymol-based formulations against GSB as a management strategy.