is a perennial weed occurring in parks, gardens, pastures, orchards, roadsides, vegetable gardens, agricultural crops and horticultural crops. A common weed worldwide, it was originally introduced from Eurasia and now occurs in every province of Canada. It is an aesthetic problem during flowering and seed production, interrupting turfgrass uniformity and density; it reduces yields of agricultural crops; it causes slower drying of hay; its pollen is allergenic; and it acts as an alternative host for several pests and diseases. A number of herbicides are available for its control. Mechanical removal of T. officinale plants has limited success, due to the regenerative capacity of the long taproot. Insects, fungi, sheep and geese have been considered as biological control agents for dandelion.

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Phomopsis castanea(Sacc.) Höhn was found to occur endophytically in plant parts of European chestnut including flowers, leaves, shoots and fruits, when apparently healthy trees of four cultivars were sampled seven times throughout 1 year. This fungus is associated with the important post-harvest disease Phomopsis nut rot. The fungus was also shown to be endophytic in seedlings of the cultivar Perton’s Pride, and seed transmitted. There were apparent differences in the incidence of P. castanea isolated between the four cultivars and the two sites tested. The incidence of plant parts yielding P. castanea was highest for cultivar Marone at both sites, and lower for cultivars Sword, Buffalo Queen and Lucente. The plant parts with the highest incidence of P. castanea were the burr, the male flower, the stigma and style, and 1-year-old and 2-year-old shoots; those with the lowest incidence were the 3-year-old and 4-year-old xylem, the inner peduncle and the nut kernel. There were no apparent trends in the incidence of the fungus recovered from plant parts at different times of the year.

Selected cultural and environmental variables were investigated for their influence on the efficacy of Phoma herbarum and Phoma exigua to cause disease on dandelion (Taraxacum officinale) under growth room conditions. In both species, mycelial fragments caused significantly greater disease severity on dandelion than spore suspensions. Mycelial age was not an important factor in disease severity caused by P. herbarum, with all cultures causing high disease ratings. However, younger cultures of P. exigua caused the greatest disease severity on dandelion, but significantly less than that caused by P. herbarum. The initial pH of the growth medium (potato dextrose broth) did not affect disease severity caused by either Phoma species. Increasing concentrations of mycelia of P. herbarum were applied to dandelions that were then exposed to various leaf wetness durations. Disease severity increased with increasing leaf wetness duration. For dandelions exposed to no leaf wetness duration, the greater the mycelial concentration, the greater the disease rating. However, for dandelions exposed to all leaf wetness durations, all concentrations of mycelia caused similar disease ratings. As P. herbarum caused high disease ratings on dandelion, it therefore warrants further investigation as a potential bioherbicide for the control of this weed.