Chapter 4 - Health

CHAPTER 4 - HEALTH

Lisa Berndt (Scion), Margaret Dick (Scion), Denis Hocking (NZFFA), Tara Murray (Scion), Ian Nicholas (Scion), Dean Satchell (NZFFA)

Of the 240 eucalypt species in New Zealand with Paropsis charybdis and Cardiaspina some individual species are more prone to fiscella. health problems than others, either insect attack or fungal. Siting can also influence the Eucalypt species do vary in their susceptibility likelihood of some health issues. This makes to pests. Many recent insect arrivals have species and site selection important factors attacked E. botryoides in particular and also in the health of eucalypt plantations. Insect E. saligna, but have not caused much damage attack is a natural part of the eucalypt forest to other species. There are currently no serious in Australia, something the trees have evolved insect pest problems with stringybark eucalypts to cope with, so ecological balance is or most of the ash group. This may be partly maintained. Some minor insect attack is fortuitous, but if some eucalypt species are therefore acceptable within a plantation, but more attractive than others, this should be a not when major parts of the crown are lost. major factor to consider during species selection, ranking equally with growth rate, Because of our proximity to Australia, we can tree form and wood properties. expect new health problems to arrive. To maintain healthy plantations, the best Some groups of eucalypts are healthier than strategy is to select more insect-resistant others. Most eucalypt taxonomists agree that groups of species, planted on the right site. the genus can be divided into seven or eight subgenera. The two major ones are the Symphyomyrtus, the Monocalyptus (or Eucalyptus) subgenera. The Corymbia Insects subgenus has now been separated out as a Any farm forester who has grown eucalypts separate genus, but for our purposes can still is probably aware of their susceptibility to be regarded as a "eucalypt". Symphyomyrtus insect pests. Some of these are now well is the largest subgenus, containing more than established in this country - many more exist 500 of the 800 recognised eucalypt species. across the Tasman Sea and may enter New Many of these are obscure and consist of small Zealand at any time. Commentators have trees found in isolated corners of Western suggested that the eucalypts are not an Australia. Others are timber and fibre species appropriate genus for forestry purposes in e.g., E. nitens, E. globulus and E. saligna, or this country because there is a seemingly common farm and ornamental trees e.g., endless supply of pests located a relatively E. viminalis, E. ovata, E. leucoxylon, E. cinerea short distance up-wind. (silver dollar). Most of the eucalypts used internationally in plantation forestry are Even when apparently good biological control Symphyomyrtus species and this has given systems have been put in place, the arrival rise to the unsupported view that only of hyper-parasites (parasites of the controlling Symphyomyrtus species are suitable for organisms) can upset the balance and plantation forestry. counteract their effect. This has happened

Visit www.nzffa.org.nz for the most up-to-date information available. 49 The second-largest subgenus is Monocalyptus monocalypts, whereas numerous examples (or Eucalyptus), referred to herecan be foundas that only attack Symphyomyrtus “monocalypts”. This subgenus contains some species. 135 species including the ashes, the stringybarks, and the true peppermints. The To summarise, Symphyomyrtus species seem subgenus Corymbia includes about 113to be more susceptible to insect attack. Some, species, many from tropical areas, the best- including E. botryoides, E. camaldulensis, known locally being C. ficifolia and C. maculata. E. viminalis, E. grandis and E. globulus appear to attract large numbers of insect pests. Three The monocalypts are considered to be the of these species represent the bulk of the most highly evolved group. They retain fewer world's plantation eucalypt resource. E. nitens of the features of their eucalypt rain forest also seems to be a popular insect target. predecessor(s). Many of the features separating subgenera relate to the flowers Nothocalyptus, with its single species and other reproductive structures, but E. microcorys, is a subgenus that appears to differences in natural plant chemicals that be relatively unattractive to insects. occur in the leaves and elsewhere are also Most entomologists are aware of the possibility recognised. These chemical differences are of a relationship between subgenus and probably important in influencing insect vulnerability to insect attack, but taxonomic preference which seems to favour groupings do not seem to have been included Symphyomyrtus species. as risk factors during selection of species for A quick survey of accessible literature suggests plantation forestry. In the meantime, the a 10:1 preference for Symphyomyrtus species planting of stringybark and ash eucalypts in as hosts for 50 common insect pests in south preference to Symphyomyrtus species may eastern Australia. The larger numbers of reduce the risk of serious damage from insect Symphyomyrtus species found in that area attack. do not account for the imbalance. Some Although monocalypts may be less vulnerable Symphyomyrtus species are attacked by nearly to insect attack than other eucalypt subgenera, every eucalypt pest. Notable in this group are they are more likely to be damaged by soil- E. saligna, E. botryoides, E. viminalisborne ,fungal pathogens, especially E. camaldulensis and other closely-related Phytophthora species, when grown on wetter species. Even possums seem to show a distinct sites and in heavier soils. The ashes and preference for Symphyomyrtus eucalypts. stringybarks are known to perform better on The monocalypt species are not free from free-draining sites. attack. Some quite serious monocalypt pests Almost all the monocalypt eucalypts have exist in Australia and the commercially blond or brown-coloured timber. None of the important E. regnans, E. obliqua and E. pilularis red-coloured timbers that seem to appeal to are frequently mentioned as insect hosts in Kiwi taste are found among the species the literature. This may reflect more intense currently established in New Zealand. Red observation of forestry species. Monocalypt timber is found mainly in Symphyomyrtus insect pests in New Zealand include the species, the best known being E. saligna and blackbutt leafminer (Acrocercops laciniella) E. botryoides. Two monocalypts with red which also attacks Symphyomyrtus eucalypts, timber are well known in Western Australia. and a number of other insects that do not These are E. marginata (jarrah), which has discriminate between species, e.g. leafrollers. never thrived in New Zealand, and E. jacksonii Some Symphyomyrtus pests also attack(red tingle). The latter has highly-regarded monocalypts. The emperor gum moth timber but its natural occurrence is very (Opodipthera eucalypti) is found on ash or restricted. With more trial, error and research, stringybark eucalypts, where it rarely causes this might be a red timber species for New major damage. On the other hand it can totally Zealand in the future. At this stage little is defoliate small Symphyomyrtus trees. Very known about its vulnerability to pests and few, if any, insect pests are restricted to diseases.

50 Visit www.nzffa.org.nz for the most up-to-date information available. P. charybdis on eucalpt foliage with typical scalloped leaf edges

Eucalyptus Tortoise Beetle (P. charybdis) P. charybdis populations in late summer. In 2001 the wasp Baeoanusia albifunicle was The Eucalyptus Tortoise Beetle is the most identified in New Zealand as a hyper-parasitoid serious defoliator of eucalypts in New Zealand. which appears to have reduced the impact of A native of Australia, it was first detected in Enoggera nassaui on P. charybdis. A second the Port Hills in 1916 and is now distributed primary parasitoid wasp, Neopolycystus throughout the country. The beetle feeds on insectifurax, was also detected in 2001. In the foliage of about 60 eucalypt species, mainly the upper North Island parasitism of Paropsis those of the subgenus Symphyomyrtus. It is by Enoggera nassaui tends to increase between particularly attracted to E. nitens and November and January, declining in February. E. globulus. Feeding is restricted to the adult Activity of the hyper-parasitoid follows a similar foliage and results in characteristic scalloping trend, while that of N. insectifurax peaks later of leaf edges. Severe defoliation of flush foliage in the summer when temperatures are at their gives trees a sparse ‘broom top’ appearance. highest. The presence of N. insectifurax may Two generations are produced each year, the therefore compensate for some of the decline female beetles beginning to lay eggs a few in Ennogera nassaui populations in late weeks after the onset of the spring foliage summer. flush. Baeoanusia albifunicle does not develop Since 1987 the beetle has been controlled in successfully on N. insectifurax and cannot many parts of New Zealand by the primary develop in unparasitised P. charybdis eggs. parasitoid wasp Enoggera nassaui. This insect Enoggera nassaui has been recorded from lays its eggs in the beetle eggs and reduces Northland to Southland and is probably well

Visit www.nzffa.org.nz for the most up-to-date information available. 51 established throughout the country. Recently, the hyper-parasitoid is likely to interfere with N. insectifurax and the hyper-parasitoid have biological control of P. charybdis, and where been found in the South Island, confirming a N. insectifurax populations may counteract this national distribution. Information about their interference. distribution will help to identify sites where

P. charybdis eggs P. charybdis larva P. charybdis adult

Enoggera nassaui P. charybdis eggs parasitizing P. charybdis eggs

Images showing the colour change which results from presence of N. insectifurax.

Gum Leaf Skeletoniser (Uraba lugens) expanding eucalypt industry as well as amenity trees. Gum leaf skeletoniser is an Australian moth that was first found in New Zealand in 1992 Uraba has been recorded from nearly 50 species at Mount Maunganui. After several years it of Eucalyptus in New Zealand and as the was eradicated from there but in 2001 it was common name implies these are the main found in Auckland. It is not known whether hosts. However, it has been recorded from the Auckland population originated from the other genera as well. Mount Maunganui ones or represents a separate incursion from Australia. It has now In 2004 Scion gained approval to import four spread throughout the greater Auckland region parasitoids of Uraba into containment, and as far north as Warkworth, with additional work began to determine if any of these would recordings in Waikato and Bay of Plenty. be suitable biological control agents. Since then For a map of the distribution, please see many problems have been encountered with http://gis.scionresearch.com/maful/viewer. mating and rearing the parasitoids, and with htm). Modelling work carried out at Scion hyper-parasitoid contamination of the parasitoid predicts that Uraba has the potential to survive shipments from Australia. In addition, rearing in all the commercial eucalypt growing regions Uraba in the laboratory as hosts for the of New Zealand and is thus a threat to the parasitoids has been difficult, with disease

52 Visit www.nzffa.org.nz for the most up-to-date information available. affecting the colony at various times. Two of with the remaining two species (Cotesia urabae the four potential parasitoids have been ruled and Dolichogenidea eucalypti (Braconidae)) out, one (Euplectrus sp. (Eulophidae)) because over recent summers with further host range a hyper-parasitoid is present in New Zealand, testing underway. Currently further work is and the other (Eriborus sp. (Ichneumonidae)) continuing as part of a Sustainable Farming because of difficulties obtaining enough from Fund project. Australia. However, progress has been made

Assessment of blackbutt leafminer (Acrocercops laciniella) damage in high-value hardwood eucalyptus species in Northland

A project of the Eucalypt Action Group of the New Zealand Farm Forestry Association supported by the Ministry of Agriculture Sustainable Farming Fund and the Neil Barr Foundation.

The first New Zealand record of A. laciniella was made in 1999 in Auckland. The pest spread rapidly throughout the North Island and was detected in the South Island in June 2004. Blackbutt leafminer is a small moth (Lepidoptera: Gracillaridae) whose larvae cause leaf damage in a wide range of eucalyptus species. It is related to New Zealand species of the same genus. Ten species of Acrocercops were present in this country prior to the introduction of A. laciniella.

Although Blackbutt Leafminer attacks all eucalypts present in Northland, this project which was based in the Kerikeri area, focussed on damage to 5- to 8-year-old trees of the major timber species E. pilularis, E. muelleriana, E. globoidea, E. agglomerata and E. microcorys. The aim was to classify the extent of leaf damage, to monitor changes over time, and to compare the susceptibility of different eucalypt species.

Conclusions

Over time, E. pilularis was the most susceptible of the monocalypt eucalypts.

High levels of damage were recorded in all species examined except E. microcorys and C. maculata.

Backbutt leafminer is the most serious pest recorded to date on stringybark eucalypt species in Northland.

It is likely that the leafminer reduces timber productivity by restricting photosynthetic activity, especially in the more susceptible eucalypt species.

The leafminer causes damage throughout the year in Northland. Peak population levels occur during late summer and early winter.

High levels of damage recorded after initial colonisation were not sustained.

Source: www.nzffa.org.nz

Visit www.nzffa.org.nz for the most up-to-date information available. 53 The Southern Ladybird (Cleobora mellyi) loss of vigour in the affected eucalypts.

Cleobora mellyi, the southern ladybird, was introduced into New Zealand from Tasmania Leaf mining sawfly in 1977 for control of the eucalypt tortoise (Phylacteophaga froggatti ) beetle, P. charybdis. It was only established in the Marlborough Sounds. This predator This insect was first identified at Auckland diets on psyllids and tortoise beetles, both airport in 1985 and has since spread throughout pests of eucalypts, and it shows some promise the country. The principal hosts of this insect for general control of eucalypt pests. are E. nitens, E. saligna, and E. botryoides, The NZ Farm Forestry Association, with support with defoliation damage being commonly from the MAF Sustainable Farming Fund has confined to the bottom 3 m of the tree. A distributed and released this ladybird to sites successful biological control programme was in the North Island to assess its effectiveness undertaken using an imported Bracon sp. as a biological control agent.

Eucalypt gall wasp (Ophelimus sp.)

Eucalypt Shoot Psyllids This is a more recent import than the sawfly, (Ctenarytaina spatulata) observed at Wellington in 1987. The main The eucalypt shoot psyllid (C. spatulata) was hosts are E. saligna, E. botryoides, and first identified in New Zealand in 1990. It E. grandis In the early phase of its spread, a appears to have arrived here without its own few attacks were so severe that some trees natural parasitoids, unlike the blue gum psyllid trees were killed. No control was attempted (C. eucalypti) which is well controlled by a for this insect. Although the insect is still small parasitoid (Psyllaephagus pilosus). So present on susceptible species, its effect effective was P. pilosus in New Zealand, it has appears less significant in recent times. now been introduced into California as a biocontrol agent for the blue gum psyllid. Brown lace lerp (Cardiaspina fiscella) Another common eucalypt shoot psyllid is Blastopsylla occidentalis (first identified in Another insect found close to Auckland airport, New Zealand in 1977) which probably came this was recorded in 1996. It moved rapidly from Western Australia. This species can throughout the North Island, but was soon produce copious white flocculence when under some biological control, which also feeding. It is reported that both psyllids appeared in the country soon afterwards, (C. spatulata and B. occidentalis) attack many however this was also hyper-parisitised. While species of eucalypts in Northland, and can still present the lace lerp is not as devastating cause damage to species within the subgenus as it was in its initial spread. Symphomyrtus. The very wide range of hosts includes many species of economic significance. Gum Emperor-moth (Antheraea eucalypti ) It appears that psyllid damage has become more prevalent in recent years. Some damage The caterpillar of the gum emperor-moth feeds possibly caused by shoot psyllid infestations on the foliage of the host plants. The main includes stunting of young plants, shedding hosts are eucalypts. The moth, however, of young leaves, and leaf and stem spots. appears to be selective when laying eggs and Moderate psyllid attack throughout the caterpillars have been recorded from only 24 Northland summer may cause leaf senescence of the 60 species of Eucalyptus that have been and premature shedding, resulting in a thinning examined in New Zealand. In 1977 it was of the crown. Winter growth flushes suffer reported that of the species that have been minor attack, with some leaf distortion and considered promising for plantations in New spotting, which may contribute to an overall Zealand (E. delegatensis, E. fastigata,

54 Visit www.nzffa.org.nz for the most up-to-date information available. E. obliqua, E. regnans, E. saligna, E. botryoides, Eucalypt Diseases E. muelleriana, E. pilularis, E. nitens, and E. oreades), only E. obliqua and E. muelleriana With increasing eucalypt plantations have yet to be recorded as having gum established in New Zealand since the 1960s, emperor-moth attack. new recordings of fungi on eucalypts have been a regular occurrence. Growth in trade The moth was first found in Wanganui in 1915 and the increasing mobility of people have and has since spread slowly from that area. created greater opportunities for the spread By 1960 it had become distributed in the wide of pathogens in addition to self-introductions coastal strip from New Plymouth through on trans-Tasman wind currents. Palmerston North to Levin, with records also from Wellington, isolated areas on the east With the establishment of these trees has coast of the North Island up to Ruatoria, and come a diverse invertebrate fauna and the Waikato region centred on Cambridge. The mycoflora. There are approximately 220 insect has frequently been used for biology species of fungi recorded from eucalypts studies in schools and teacher training in New Zealand. These can be broken down establishments, as well as in the home. Much as: about 10 mycorrhizal species; 110 of the spread of the moth has resulted from foliage and stem fungi; 70 wood decay intentional or accidental releases from these fungi, and about 30 others (sapstain, litter situations. The gum emperor-moth was first saprobes, nursery root associates). recorded as being established in the South Island in Nelson in 1968. Widespread outbreaks of the gum emperor-moth have not been Australian introductions recorded, and it is thought that populations are probably regulated by natural biological Many of the fungi, particularly the foliar control agents. Caterpillars are often found pathogens, are easily recognisable infected with a polyhedral virus and, under introductions. A few examples are tabulated conditions suitable for mycelial growth, may below in chronological order of detection. succumb to a parasitic fungus (Beauveria sp.). Some have proved capable of causing profound defoliation of plantation trees.

Table 10: Chronological order of Australian Pinhole Borer foliar pathogens recorded in New Zealand (Platypus apicalis and P. gracilis) Fungal pathogen First NZ collection When eucalypts are grown within a few kilometres of native forest, Mycosphaerella cryptica 1955 on E. delegatensis especially those with native beech, the eucalypt trees can be attacked Aulographina eucalypti 1980 on E. regnans by native pinhole borers. Although Mycosphaerella nubilosa 1981 on E. globulus attack by these beetles is usually abortive, it can result in kino Phaeophleospora 1981 on E. nitens production which can degrade the eucalypti appearance of the timber. Mycosphaerella 1998 on E. muelleriana suberosa Ghost moth (Aenetus virescens) Leptomelanconium 2002 on C. ficifolia This native insect, which only occurs australiense in the North Island, can burrow into the stem of young trees, but such damage is usually confined to Others have been described for the first time in New the knotty centre of the stem, and Zealand. Whether these are uncommon and is of minor consequence. unrecognised in their native land, or whether they originated in New Zealand is currently unknown.

Visit www.nzffa.org.nz for the most up-to-date information available. 55 Table 11: Chronological order of new foliar infection occurs in spring, decreasing pathogens first recorded in New Zealand through summer and autumn and seldom occurring in winter. Time of Fungal pathogen First NZ collection pruning can therefore influence attack. Winter is the most suitable (in fine, Trimmatostroma bifarium 1981 on E. fastigata dry weather), or in fine weather during other seasons, but pruning should not Pseudocercospora crousii 1981 on E. regnans be done when the weather is warm and wet. Prevention can be managed Phytophthora captiosa 1986 on E. botryoides by pruning branches <2.5 cm diameter. Applying horticultural fungicide on Sarcostroma 1988 on E. nitens pruning wounds may reduce infection. mahinapuense Silverleaf has sometimes been found Pseudocercospora acerosa 1999 on E. nitens in unpruned trees so not pruning is not a guarantee of preventing infection.

The most significant diseases on plantation Sarcostroma (Sarcostroma mahinapuense) eucalypts, at the present time, are detailed below. This disease has only been found on E. nitens on the west coast of the South Island where it has caused branch cankers and Stem Diseases dieback. Although the fungus is present in other parts of the country it is not associated with extensive cankering.

Silverleaf Disease (Chondrostereum purpureum) Foliar Diseases Chondrostereum purpureum has a very wide host range and is most well known as the Eucalypts vary in their susceptibility to foliar cause of silverleaf disease of fruit trees such diseases but as a general rule species that as peach and cherry. Plantation hosts include come from summer dry areas of Australia Eucalyptus, Acacia, Cupressus, Fagus, are particularly susceptible when grown in Fraxinus, Nothofagus etc. In eucalypts it was summer wet areas. In general terms, areas first recognised during a thinning operation south of Sydney and across to southern where outwardly healthy trees had internal Western Australia tend to have winter decay. It is associated with pruning wounds maximum rainfall and areas north of this, with the infection spreading up and down from particularly along the eastern coastline, tend the point of entry. to have summer maximum rainfall – a trend which becomes stronger as you move further It can cause silvering of foliage, stain and north. In areas of New Zealand with warmer, decay, branch death, timber degrade and the wet and humid summers (Northland, Bay death of young trees. Symptoms are not so of Plenty), species from northern coastal obvious in eucalypt species with silvery leaves NSW may well prove more successful than e.g., E. delegatensis. species from summer-dry Victoria, South Australia and southern Western Australia, Chondrostereum purpureum enters through especially inland areas of these states. pruning stubs. Fruiting bodies, which have a purplish underside when fresh and moist, There are many different foliar fungi on develop on dead wood - both branch and eucalypts with more arriving every year stem. Spores are released during periods of because of our proximity to Australia. Some rain or high relative humidity (>95%) and have very distinctive symptoms (e.g., are dispersed on moist wind currents. Most Aulographina eucalypti), some have very

56 Visit www.nzffa.org.nz for the most up-to-date information available. similar symptoms, while others can only be Mycosphaerella spp. identified by microscopic examination. Some foliar diseases may occur at low levels and There are about 28 species on eucalypts, with have no significant effect on tree health, and only eight species recorded in New Zealand. often occur on older leaves and in the lower Of these only two are associated with serious part of the crown. Foliar disease symptoms defoliation and dieback. These are M. cryptica are most severe in areas where there are and M. nubilosa which tend to have a different extended periods of leaf wetness and they host range. (Table 12) can occur regionally and locally (in valleys and gullies and at high altitude). Common foliage diseases are:

Mycosphaerella cryptica

Mycosphaerella nubilosa

Aulographina eucalypti

Pseudocercospora spp.

Phaeophleospora eucalypti

Table 12: Summary of Mycosphaerella cryptica and M. nubilosa hosts and symptoms

Mycosphaerella M. cryptica M. nubilosa species

Hosts Eucalyptus delegatensis, Eucalyptus globulus, E. nitens, E. diversicolor, E. fastigata, E. viminalis E. globulus, E. nitens, E. obliqua, E. regnans

Symptoms Early lesions red-brown, often Creamy-yellow – pale brown prominent purple margin. With age, irregular lesions. Later lesions lesion becomes grey. Old infected grey-black (perithecia on leaves may have holes, leaf buckling underside), 5-25 mm diameter and distortion. Some hosts: shoots and may coalesce. Severe on and twigs infected - cankers. Cankers juvenile foliage, adult foliage can girdle shoots and twigs - thin mainly resistant. Primarily crown and dead tops. Stunts growth E. globulus and subspecies and results in a bushy multi-leadered also E. nitens. crown. Can look like frost damage.

Comments Has caused serious defoliation of Has caused serious defoliation E. delegatensis. Also affects in plantations in Australia. E. regnans and other ash group eucalypts. Young trees are susceptible, Tasmanian provenances of E. delegatensis are much more resistant than Victorian provenances.

Spores are spread by water splash. Continuous high RH or high rainfall are favourable conditions for attack.

Visit www.nzffa.org.nz for the most up-to-date information available. 57 Target spot (Aulographina eucalypti) Spore production is ongoing during spring and summer until leaf shed, i.e. general The main hosts of this fungus in New Zealand increase in inoculum. are E. delegatensis, E. fastigata, E. globulus, E. nitens and E. regnans. Epidemic build up of stand infection during growth season; spots yellow, then crimson The symptoms are a corky leaf spot, roughly in January, later brown. circular in shape with a raised corky centre. The spots often do not go right through the The cycle slows down as temperatures cool leaf. Lesions can also form on petioles and after the end of summer. twigs. Other fungi, such as Trimmatostroma In the worst areas foliage is lost within one spp. can often be found on the lesions with year. Aulographina. In the worst areas, half or less of the current foliage is retained compared to Eucalypt Leaf Spot (Pseudocercospora spp.) healthy sites.

Major hosts are E. delegatensis, E. fastigata, This impacts on growth, especially but not E. globulus, E. nitens, E. obliqua, and solely in coastal areas of the Bay of Plenty E. regnans. region.

The symptoms are angular brown lesions which are first visible in January on new leaves, Control mechanisms and the main infection period is January – March. The spores, which are wind dispersed, In field trials of host resistant material, are produced on leaf spots. E. nitens from NSW was better than from Victoria.

E. globulus ssp. maidenii showed low Septoria Leaf Blight (Phaeophloeospora infection by P. eucalypti and Mycosphaerella eucalypti, previously called Septoria spp. pulcherrima, Kirramyces eucalypti)

Septoria was first found in New Zealand in 1981, but became important in the 1990s in E. nitens stand survey young E. nitens plantations. The hosts of this in April 2005 Forty-nine 8- to12-year-old stands fungi include E. globulus, E. nitens, E. viminalis, were visited and assessed for leaf spotting by E. grandis and several other species, but the P. eucalypti (categorised as trace, low, medium, most significant is E. nitens. high). The symptoms are leaf spots extending to The results were that: both sides of leaf which are initially yellow, then turn a crimson colour. Both juvenile and Infection by P. eucalypti was widespread. adult foliage are affected, resulting in the infected leaves being cast. It can also be Stands were worse within 20 km of the associated with M. cryptica. coast.

The disease development in a severely Stand condition appeared to relate to mean diseased plantation is as follows: annual temperature and mean daily temperatures for January and July, and to Infection of new leaves occurs from spring elevation. onwards (from spores on leaves remaining from the previous infected season). Stand condition was not affected by rainfall humidity or extreme temperatures. New juvenile leaves become resistant after several weeks.

58 Visit www.nzffa.org.nz for the most up-to-date information available. Mean Annual rainfall Mean Annual Temperature

Interaction of P. eucalypti with mean annual rainfall and temperature (from Hood and Alexander, 2006)

Summary

In the absence of a more intensive survey, further cultivation of E nitens cannot be encouraged within a zone extending 20 km in from the Bay of Plenty coast.

Further inland, ridge tops or valley floors should be avoided.

It is probable that improved eucalypt planting stock will become available for such risk sites, even if it may not be from within E. nitens.

Prospects are now limited for E. nitens in the Bay of Plenty region as a result of the impact of P. eucalypti and P. charybdis.

Foliar Phytophthora spp.

This disease was investigated after extensive growth patterns, host species and in location foliage death in a stand of 18-year-old within New Zealand. The method of E. botryoides was recorded in the spring of dissemination has not been determined. 1986. Similar symptoms were found in nearby E. macarthuri, E. sieberi and E. saligna. Defoliation and dieback was also recorded in Barron Rd Syndrome a stand of young E. fastigata in spring of 1987. (an eco-physiological disorder) Extensive defoliation of E. delegatensis was recorded from Southland, and minor infection This problem was identified on E. regnans, of E. nitens has been recorded. E. fastigata and other species. The symptoms are foliage loss, shoot galling, shoot abortion, Symptoms are infection of leaves, petioles leaf spots, dieback and mortality. The primary and twigs followed by defoliation and dieback. cause is thought to be planting the species in The symptoms are initiated in mid - late winter environmental conditions that differ from those or in early spring, but with few symptoms in in the source locations in Australia and summer. are not suitable for the species. A range of Two species of Phytophthora have been found fungi develop on the leaves with the most associated with leaf and twig lesions and common being Aulographina eucalypti and pathogenicity has been demonstrated. The Pseudocercospora spp. species differ in morphology, temperature-

Visit www.nzffa.org.nz for the most up-to-date information available. 59 Key Points

Some eucalypt species are more resistant to insect pests than others.

Insect resistance should be considered during species selection of eucalypts and is as important as growth rate, tree form and wood properties.

The planting of stringybark and ash eucalypts in preference to Symphyomyrtus species may reduce the risk of serious damage from insect attack.

Leaf spot diseases can be reduced by species selection and careful siting.