Australian researchers have developed a Moisture Index to predict development success of the barber pole worm (Haemonchus contortus).
Development from egg to infective larvae requires adequate temperature and moisture. For example, development of barber pole eggs occurs with minimum and maximum temperatures that exceed 10ºC (50ºF) and 18ºC (64.4ºF). Temperatures below these values are unlikely to lead to development. In fact, the optimum temperature range for development is 25º to 35ºC (77º to 95ºF).
Greater temperatures lead to faster development from egg to infective larvae. However, adequate temperature is insufficient for successful development without rainfall. Development requires sufficient moisture at the right time in relation to when the eggs are deposited onto pasture in fecal pellets.
Moisture (evaporation) is a more important consideration than rainfall alone when estimating development success of the barber pole worm. According to the researchers, a cumulative ratio of rainfall to evaporation over a 3-day period is a useful predictor of development to infective larvae.