Identification of the production and storage factors that affect conidial germination and bioactivity (fitness) will assist the success of biological control agents. Effects of culturing conditions on conidial fitness of Trichoderma atroviride LU132 were examined in different storage conditions over time. Abiotic factors (temperature, nutrients, water activity, pH) during production were studied. Conidia from the culturing regimes which resulted in greatest and least bioactivity against Rhizoctonia solani in dual culture were selected to assess effects of storage condition on conidial fitness. Fitness of the test conidia was examined after storage at 30°C and at 0 or 50% relative humidity (RH) over 6 months. Fitness declined over time, and the decline was greater for 50% RH than 0% RH. The greatest number of conidia and germination percentage resulted from conidia produced at 25°C, but greatest bioactivity resulted from those produced at 30°C. Different C to N ratios (5:1 or 160:1) did not affect these parameters. However, fewer conidia were produced at 30°C, and the least germination and bioactivity resulted from conidia produced at 20°C. Conidia can be divided into two groups: those adapted to extreme culturing conditions (e.g. high temperature), and those protected by nutrients during storage. However, environmental factors are not independent. For example, conidial production at 30°C is probably accompanied by water stress, oxidation, and rapid pH change which may also affect fitness
