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Significantly greater Dictyocaulus viviparus stage three larval recoveries from herbage samples adjoining first stage larval infected dung pats with Pilobolus, and the effects of biotic and mechanical factors on dung pat integrity supported previous findings. Several meteorological factors including sunshine hours, relative humidity, rain total and wind speed showed significant correlations with growth of Pilobolus on dung surfaces. The influence of monitored variables on the recovery of third stage larvae from herbage and the growth of Pilobolus was modified by height of the sward surrounding the dung pat. Multiple regression analysis showed that 60 per cent of variation in D viviparus third stage larvae recovery from herbage was accounted for by known variables.

An involvement of Pilobolus species fungus in the dispersal of Dictyocaulus viviparus third stage larvae from dung to surrounding herbage under Irish conditions was investigated. The presence of Pilobolus kleinii on artificial dung pats containing first stage larvae of D viviparus was associated with a 19-fold increase (P less than 0.05) in numbers of third stage larvae recovered from the surrounding herbage. A subjective examination of natural dung pats showed that the presence of Pilobolus species was significantly correlated with hours of bright sunshine (r = -0.5, P less than 0.01), total rainfall (r = 0.41, P less than 0.05) and the height of herbage surrounding the pats (r = 0.31, P less than 0.001). A multiple regression analysis showed that meteorological parameters and the height of surrounding herbage accounted for 38 per cent of the variation in growth of Pilobolus species on dung pats. The incidence of extensive damage to natural dung pats within five days of deposition, caused by biotic factors, another possible cause of D viviparus third stage larvae dispersal, varied from 0 to 92 per cent of the pats depending on their degree of dryness.