Summary Twelve active ingredients were screened for their ability to control foliage disease caused by Phytophthora kernoviae and Phytophthora pluvialis . Inhibition of mycelial growth and sporangial production of both pathogens were assessed in in vitro assays after exposure to three concentrations of each active ingredient. While most of these active ingredients inhibited mycelial growth in vitro, due to their widespread use, phosphite, copper oxychloride and metalaxyl‐M were selected for further study. Four rates of each active ingredient were applied to two Pinus radiata genotypes, and detached needle assays at 6 and 90 days post‐treatment were used to determine treatment efficacy and persistence. Untreated needles showed significantly larger lesions than all fungicide‐treated needles after exposure to P. pluvialis or P. kernoviae on both sampling dates. Efficacy and persistence of the three active ingredients did not increase with increase in concentration. Larger lesions were formed on more susceptible genotype after inoculation with both Phytophthora species, even when higher rates of active ingredients were applied. Phosphite, copper oxychloride and metalaxyl‐M have potential to protect commercially planted P. radiata from these two Phytophthora species.

Background: The oomycete Phytophthora kernoviae is known from the United Kingdom and the Republic of Ireland, where it is considered to be a recent invader, from Chile where it was only discovered in 2014, and New Zealand where records date back to 1953. As there is little information in New Zealand linking P. kernoviae with plant disease, it may have been present for much longer and may be indigenous. Seasonal activity of P. kernoviae in a site known to have infested soil was tested by isolation from soil and foliage of existing shrubs and the use of indicator plants. In greenhouse studies, the susceptibility of a range of indigenous plants to P. kernoviae was tested via stem and foliar inoculation.Methods: Soil, litter and understorey vegetation samples were collected for isolation of P. kernoviae at monthly intervals for a year. Plants of Rhododendron catawbiense, which is known to be susceptible to foliar and shoot infection, were placed in the stand as indicator species. In laboratory and greenhouse studies, stem and foliar inoculations of a selection of arborescent plants representing major groups within the New Zealand flora were carried out and compared with three exotic plants of known susceptibility.Results: Phytophthora kernoviae was not isolated from foliage of understorey plants at the study site, but it was recovered from soil and litter from April to November (autumn through spring) inclusive. Little disease developed on the Rhododendron catawbiense indicator plants. All of the exotic, and most of the indigenous, species developed a lesion in response to stem inoculation. Stem lesions were more developed on exotic species than on indigenous hosts. In contrast, few species formed foliar symptoms. Phytophthora kernoviae was recovered from asymptomatic tissue, stems and foliage, of a number of species.Conclusions: Based on the results of the inoculations and the lack of historical records of disease of indigenous plants associated with P. kernoviae, this oomycete does not appear to be a damaging pathogen of New Zealand's indigenous flora. Although presence in the soil or litter was demonstrated at the study site, little disease developed on the indicator plants suggesting that at least part of the New Zealand population is of low pathogenicity to R. catawbiense.

Background: Red needle cast, a new foliage disease of Pinus radiata in New Zealand is described. The disease has been variable in incidence and severity both regionally and in different years. The early symptoms of discrete olive coloured lesions, often with a narrow dark resinous mark or band, were first recognised in winter of 2008 in plantation forests on the eastern coast of the North Island. These lesions develop further to result in rapid needle senescence and premature defoliation. The disease has been termed red needle cast in New Zealand as affected trees have a reddish appearance prior to the casting of the needles. The subsequent four years of monitoring have confirmed that, depending on location, symptoms are first observed in late autumn through late winter. Newly developing spring and summer foliage is seldom affected. Isolation from needles using a Phytophthora-selective medium frequently yielded an unknown species of Phytophthora which was subsequently found to be identical to Phytophthora pluvialis, a species described from Oregon, USA in 2013 where it is not associated with disease. Infection appears to be limited to the needles with no recoveries of Phytophthora pluvialis having been made from the roots, stems or branches. Occasionally a second species of Phytophthora, P. kernoviae, was also recovered from needles with the same symptoms.Methods: Needle symptoms were described in the field from 2008-2012 with isolation onto Phytophthora selective media. Koch's postulates was completed on potted plants and detached needles.Results: Symptoms were reproduced on both detached needles and potted plants of Pinus radiata when inoculated with zoospore suspensions of Phytophthora pluvialis.Conclusions: This paper presents evidence that Phytophthora pluvialis is the primary cause of red needle cast in New Zealand.

Nectria flute canker is a disease of Pinus radiata stems caused by Neonectria fuckeliana The fungus is not known in the North Island leading to concern that it may be transported north via asymptomatically colonised nursery stock Wounded P radiata seedlings and cuttings were exposed to natural inoculum from an adjacent infected forest and half were artificially inoculated No disease symptoms were recorded throughout the trial Neonectria fuckeliana was reisolated from 24 and 7 of inoculated seedlings and cuttings respectively 3 months after inoculation and at 12 months from 35 of the remaining inoculated seedlings only Neonectria fuckeliana was not isolated from uninoculated seedlings or cuttings exposed to natural inoculum These results indicate that nursery plants have little capability of retaining N fuckeliana within the tissue even when directly inoculated Nursery stock is therefore unlikely to be a pathway for transport of the fungus

The global movement of solid wood packaging material is an important pathway by which invasive organisms have increased their range. The International Standard for Phytosanitary Measures No. 15 (ISPM No. 15) was published by the Secretariat of the International Plant Protection Convention to provide guidelines for wood treatment to reduce the risk of accidental pest movement via solid wood packaging material. This study assessed the exposure temperature and time combinations necessary to kill a range of fungi and one species of Phytophthora colonizing wood. The ISPM No. 15 protocol (heat to 56 degrees C core temperature for 30 min) was included as one of the treatments in the experiment. The survival data collected in this experiment were utilized to develop a binomial generalized linear model that allowed statistical assessment of survival following treatment. The tolerance of the isolates to heat treatment was variable and it was found that the ISPM No. 15 protocol did not result in mortality of all species that were tested.

Chemical and biological agents were evaluated for their ability to suppress root rot, caused by Phytophthora cactorum, in field‐grown radiata pine seedlings in New Zealand. Trials were conducted over two seasons in an area of a forest nursery with a natural infestation of P. cactorum, and a history of root rot. In each season, symptoms of root rot developed during April, one month after root pruning, when seedlings were approximately six months old. In trial one, root rot incidence by mid July 2007 was 9·1% in untreated plots and 8·4% in plots that had been treated with metalaxyl‐M/mancozeb (14 kg ha−1) at seedling emergence. Disease incidence was lowest (2·1%) in plots that received seven monthly applications of phosphorous acid (6·5 L ha−1). Other treatments, including seed coating with thiram or Trichoderma spp., and foliar applications of methyl jasmonate, did not control disease. In trial two, effects of treatment timing relative to root pruning were investigated. By late June 2008, three months after root pruning, root rot incidence was 22·2% in the untreated plots. Phosphorous acid was the most effective treatment and almost completely suppressed disease (0·1% incidence) when applied fortnightly from February until May (seven applications). Metalaxyl‐M/mancozeb (15 kg ha−1) was not effective (21·4% incidence) when applied five months before root pruning. However, disease incidence was reduced when the chemical was applied one week after root pruning (14·9% incidence) and greater control was achieved (8·2% incidence) when the application rate was increased to 50 kg ha−1.

In an investigation of the forest fungus Neonectria fuckeliana ascospores from the air were trapped on petroleum jellycoated glass slides that were replaced weekly for a year To determine variation in spore counts between assessors examining the spore traps four assessors counted the same ten spore traps and spore numbers were compared Results were highly variable between assessors with almost 100 ascospores (54 of the higher count) being the difference between the highest and lowest counts for a single trap in one extreme case To explore sources of assessor variation the four assessors also counted the same five single transects of a spore trap and results were still highly variable Two possible sources of variation identified were poor visualisation of ascospores and misidentification of ascospores Potential solutions to assessor variability include further training using multiple assessors for each trap and calibrating assessors Molecular techniques could also be used to quantify spore numbers

Stem malformation associated with stained sapwood, typically developing after pruning, has become a problem in some Pinus radiata (Monterey pine) plantations in southern regions of New Zealand. Neonectria fuckeliana (syn. Nectria fuckeliana) is the most commonly isolated fungus from affected trees. In order to critically assess the pathogenicity of this fungus, Koch’s Postulates were conducted under controlled conditions in the glasshouse and under field conditions in the forest plantation. The pathogen was recovered from diseased tissue; however, there were marked differences in individual tree response to infection as some inoculated trees did not become diseased.

Neonectria fuckeliana causes a stem canker (Nectria flute canker) of plantationgrown Pinus radiata in southern regions of the South Island of New Zealand Initiation of disease is primarily associated with pruning operations and modification of pruning regimes has led to a reduction in disease incidence Factors that influence establishment of infection and symptom expression are being examined In one trial in which 50 trees were challenged with three different conidial concentrations individual trees varied markedly in their response to inoculation Twentytwo percent of controls (wounds inoculated with sterile water) developed depressions that resembled small cankers Six percent of the trees did not develop cankers at any concentration when inoculated with conidiospore solutions Fortyeight percent responded with increasing canker length with increasing dose and in 26 of trees severe cankering developed at all inoculum concentrations Perithecial formation on the cankers was correlated with canker severity Host genotype is being examined further with the goal of identifying families that contribute to susceptibility to canker formation

Ectomycorrhizal (ECM) fungi dramatically enhance the growth of the plantation species Pinus radiata and facilitate the establishment of nursery seedlings following outplanting This study investigated ECM species colonising P radiata seedlings in the nursery and their fate in the first year of outplanting Naturally occurring ECM communities of P radiata seedlings in the Te Ngae Nursery Rotorua were investigated and these seedlings were assessed following outplanting in Kaingaroa Forest Observations of the ECM communities were made eight times during the first year of the seedlings being in the plantation forest In addition the ECM communities of 1 2 and 8 year old P radiata plantation stands were also analysed It was found that nursery ECM survived the first year of outplanting The first nonnursery ECM Pezizales sp occurred 6 months after outplanting at Kaingaroa but these were in minor abundance Rhizopogon rubescens was the most persistent and dominant nursery ECM species Overall nursery ECM survived for 2 years following outplanting but were completely replaced by 7 years

Pitch canker is a highly damaging disease of Pinus radiata and the New Zealand forest industry is concerned by the potential impact of the disease, should it arrive, in New Zealand. To provide a rapid identification technique for this pathogen, a polymerase chain reaction‐based diagnostic method has been developed. The method is able to detect the presence of the pathogen within infected host tissue, as well as infested soil and the reliability of the test has been estimated using Bayesian statistics.

In southern New Zealand Neonectria fuckeliana is associated with a stem flute canker of Pinus radiata which can result in severe stem malformation and growth loss This research consisting of three distinct experiments aimed to determine pathogen survival in processed and unprocessed wood and woody debris In the first experiment the survival of the pathogen in living trees was examined by sampling trees infected with N fuckeliana in 6 different years In the second experiment the survival of the pathogen in woody debris was examined using 36 infected logs in a range of sizeclasses The logs were left on the forest floor in shaded and unshaded conditions and sampled for N fuckeliana after 4 and 9 months The third experiment examined the survival of the pathogen in processed wood Boards cut from infected trees were tested in six standard timber drying treatments Boards were sampled before and after drying to determine the presence of living N fuckeliana Neonectria fuckeliana was successfully isolated from trees at all infection times tested The fungus was also successfully isolated from 81 of logs after 9 months on the forest floor There was no significant difference between shaded and unshaded treatments Neonectria fuckeliana was not found in any boards following kilndrying but was successfully isolated from 69 of infected boards subjected to the two standard airdrying treatments for 9 weeks

Concern about the poor health of oak trees in Auckland was raised in 2001 An intensive investigation of oak trees showing symptoms of decline (twig and branch dieback epicormic growth trunk cankers bark loss and tree death) was conducted in the Auckland area during 2006 Disease symptoms on trees at 13 sites were documented and samples of leaves stems trunks roots and soil collected Soil samples were tested for the presence of soilborne fungi using baiting techniques Fungi and bacteria from plant tissues and soil were identified using either morphological characteristics biochemical testing or molecular techniques The investigation resulted in a range of fungi and bacteria being identified One fungus new to New Zealand was detected and several new host associations observed No particular organism was implicated as the cause of the oak decline but several fungi and bacteria were likely contributors to the tree decline and death in Auckland

Fusarium circinatum, the causal agent of pitch canker, attacks Pinus spp. in Mexico, Japan, South Africa, Chile, Spain and the United States. The pathogen was first recorded in conifer nurseries in South Africa and Chile. Pinus radiata is an economically important species in New Zealand and if F. circinatum were to establish here the impact could be severe. Therefore, the ability to identify F. circinatum in soil is essential for early detection and subsequent eradication of the pathogen. The object of this study was to ensure that F. circinatum could be readily isolated from soil using culturing and molecular techniques. Two samples of non-sterile commercial potting mix and two samples each of sterile and non-sterile nursery soil were inoculated separately and together with F. circinatum and F. oxysporum under strict quarantine conditions. Fusarium circinatum was re-isolated more frequently from the sterile soil than the non-sterile soil and very little F. circinatum was isolated from the potting mix. Molecular techniques were able to detect F. circinatum in soil and potting mix when the initial concentration of F. circinatum was high. Results suggest that F. circinatum is a poor competitor against other fungi in the soil environment.