DISTRIBUTION AND INFECTION PERIOD OF PHAEOCRYPTOPUS GAEUMANNII IN NEW ZEALAND

Abstract

Since its discovery in the central North Island of New Zealand in 1959, Phaeocryptopus gaeumannii (Rohde) Petrak, a needle parasite of Douglas fir (Pseudotsuga menziesii (Mirb.) Franco), has spread over much of the country. It can now be found in most areas where Douglas fir is grown in the North Island and in a number of localities in the South Island, mostly in the northern half. In several North Island areas infected trees are now partly defoliated, but whether P., gaeumannii is the prime cause has yet to be determined. In observations over three years, ascospores were first found within pseudothecia in late August or early September. The percentage of such mature pseudothecia increased to a maximum between September and December but then declined, becoming infrequent during January and February. Observations on trees and potted seedlings showed that foliage exposed to natural infection for several weeks following flush (late October-November) attained levels of infection exceeding 80%. Infection of foliage exposed after about mid-December to January was reduced to 6% or less. Emergence of pseudothecia was first observed in April and by June they were large enough to be seen with the naked eye.