An investigation into the ecology, biology, distribution and control of Haemaphysalis longicornis Neumann, 1901 : a thesis presented in partial fulfilment of the requirements for the degree of Master of Veterinary Science at Massey University
In 1974, questionnaires were distributed to farmers in the East Coast and Hawke's Bay areas of the North Island of New Zealand. The tick Haemaphysalis longicornis Neumann 1901 was present on 59% of farms in the East Coast-Northern Hawke's Bay area and 7% of farms in the remainder of the Hawke's Bay area. In the former area the tick appeared to have spread rapidly between 1964, and 1974. In the East Coast-Northern Hawke's Bay area, approximately one third of all farmers considered that the tick was a significant problem on their farm. In the Central and Southern Hawke's Bay area the tick was not considered a problem and conditions were probably marginal for tick survival. The distribution of the tick was related to temperature, rainfall and altitude. Almost all farms where ticks were present were situated at less than 300 metres above sea level. The distribution of tick counts of sheep were positively skewed and it was shown that the data should be normalized by transforming to logarithms or square roots. Square roots represent the easiest method of transformation. A comparison between tick counts of the left ear, right ear, both ears and the body, showed that overall ear counts contribute to nearly 50% of the total tick count. However, the proportion of ticks on the ears compared with on the body varied over the counting period and ear counts were not highly correlated with body counts (highest correlation, r = O.38). The diamide, amitraz, showed a higher initial efficacy against H. longicornis compared with chlorfenvinphos, but the latter appeared to have a longer period of residual activity. In the Northern Hawke's Bay and East Coast area most (84%) sheep owners dip between January and March and over half (54%) dip in January or March and this period does not coincide with the adult and larval peaks. Increasing sheep numbers from 3 per 1000 m2 (equivalent to 30 per hectare) to 3 per 500 m2 (equivalent to 60 per hectare) resulted in lower tick survival in the more heavily stocked areas. An examination of the water balance of the unfed stages showed that larvae were very susceptible to desiccation at humidities below 80% R.H. Adults were more resistant to desiccation than nymphs. Larvae and nymphs regain water rapidly after desiccation. The critical equilibrium activities for the unfed stages was found to be approximately 0.8, 0.7 and 0.9 for larvae, nymphs and adults respectively. Immersion of unfed and engorged stages in water indicated that the former survive immersion for > 18 days while the latter showed lower survival. Evidence is presented to suggest H. longicornis can cause deaths from anaemia in young Red Deer.