Eucalypt Pest Research Articles

PATHOGENS AND PESTS OF EUCALYPTS

Eucalypts are globally distributed perennials of Australian origin. They are affected by a wide range of parasites which cause epidemics or sporadic damage of varying degrees of importance in different environments. In isolated eucalypt communities such as Australia, exotic insects and pathogens which do not currently occur on this continent, but which have adapted to eucalypts elsewhere, are a constant threat. An example is guava rust (Puccinia psidii) in South and North America which could cause enormous damage to native eucalypt communities if it established in Australia. Major diseases of eucalypts in both native stands within and exotic plantations outside Australia include bacterial wilt, fungal leaf spots and blights, fungal stem cankers and root rots caused by soilborne Pythium, Armillaria and Phytophthora species. Insect pests of greatest importance include psyllids, fungus gnats, chalcids, scales and borers. Nematode and virus diseases have received little attention. There are diseases of unknown cause, as well as diseases of complex etiology, in which it is difficult to determine the relative roles of changing environment, human activities and potential pests and pathogens on outcomes such as decline and dieback of native or planted stands. Management of specific pests and pathogens can be achieved by determining their biology and epidemiology and interrupting their disease cycle by various strategies, whereas diseases of complex etiology more likely have to be managed by selection for resistant provenances of desirable species. International movement of germplasm for commercial and nursery purposes is extensive and protocols have been developed for safe movement via seed and in vitro material. Other avenues such as pollen and embryo transfer would be relevant for controlling movement of intracellular pathogens if any are found to be important pathogens in the future.

Nontarget species selection for host range testing of <i>Cotesia urabae</i>

Classical biological control is being attempted for Uraba lugens (Lepidoptera Noctuidae Nolinae) an Australian eucalypt pest established in New Zealand The Australian solitary larval endoparasitoid Cotesia urabae (Hymenoptera Braconidae) is the most promising agent under investigation A nontarget species list was compiled for host range testing The endemic species Celama parvitis is the sole New Zealand representative of the Nolinae and was highest priority The next most closely related subfamily is the Arctiinae of which New Zealand has four endemic species (Metacrias huttoni M erichrysa M strategica and Nyctemera annulata) and one introduced biological control agent (Tyria jacobaeae) The merits of including other more distantly related members of the Noctuidae and unrelated Lepidoptera filling a similar niche are discussed

Insect pests of eucalypts in California: implications of managing invasive species

For the first 150 years following their introduction, eucalypts planted in the California landscape were free of both insect pests and diseases. In the last 15 years, numerous herbivorous insect species have been introduced accidentally into the State and have caused significant damage to the trees. Several of these species, e.g. Phoracantha semipunctata (Fabricius), Phoracantha recurva Newman (Coleoptera: Cerambycidae) and Gonipterus scutellatus Gyllenhal (Coleoptera: Curculionidae), have also been introduced into other parts of the world where eucalypts are grown, whereas others, e.g. Glycaspsis brimblecombei Moore (Hemiptera: Spondyliaspidae) and Eucalyptolyma maideni Froggatt (Hemiptera: Spondyliaspidae), are currently restricted to California and Australia. Research programmes have provided management solutions to individual pest problems, but as more pest species are introduced, these solutions must be integrated across broad geographic, horticultural, and economic scales, in a systems approach.

Foliage insect diversity in dry eucalypt forests in eastern Tasmania

Species numbers and composition of the insect fauna occurring on trees and shrubs were studied in dry eucalypt forests in eastern Tasmania over nine years. In all, 1164 named and putative species representing 17 orders and 157 families were collected. The bulk of the species belonged to the orders Coleoptera (28%), Hymenoptera (25%), Hemiptera (18%), Lepidoptera (14%) and Diptera (10%). Of the species collected, 388 -- about one-third -- were identified at least to genus or species level. These included 21 named species not previously listed in the Tasmanian insect fauna and 90 undescribed species. A list of 22 host plants for 171 insect species was compiled from records of 132 insect species observed feeding during the study and from previous records ofinsect/host plant associations for 39 insect species found on the study plots. Most insects were feeding on eucalypts (127 insect species) and acacias (38 species). The most widely distributed and commonly collected species were several well-known pests of eucalypts: Gonipterus scutellatus (Coleoptera: Curculionidae), Uraba lugens (Lepidoptera: N octuidae), Amorbus obscuricornis (Hemiptera: Coreidae), Chaetophyes compacta (Hemiptera: Machaerotidae) and Eriococcus coriaceous(Hemiptera: Eriococcidae). Host plants supporting the richest insect fauna were Eucalyptus amygdalina (74 species), E. obliqua (64), E. viminalis (46), Acacia dealbata (35), E. dalrympleana (33), E. sieberi (31), E. delegatensis (30), E. pulchella (24) and E. globulus (19). The broad-striped ghost moth, Fraus latistria Walker (Lepidoptera: Hepialidae), was collected during the study. This species is classified as 'rare' on the list of Tasmania's threatened fauna and the collection established a new locality record.

Susceptibility of life stages of <i>Paropsis charybdis</i> to <i>Beauveria bassiana</i>

Paropsis charybdis (Coleoptera: Chrysomelidae) is a pest of eucalypts and is responsible for increasing problems in some New Zealand plantations. In bioassays at 25 oC, isolates of the entomopathogenic fungus, Beauveria bassiana, were tested against larvae, pupae and adults of P. charybdis. Using a topical spray application of 10 5 and 107 conidia/ml, larvae and pupae were highly susceptible to two isolates of the fungus and a commercially available B. bassiana product. In a second experiment, an isolate from the commercial product and a larval-active isolate were less pathogenic to adults than larvae or pupae. First to second instar larvae died more rapidly than older instars and pupae after infection.

Gonipterus scutellatus Gyllenhal (Coleoptera: Curculionidae) oviposition on seven naturally co-occurring Eucalyptus species

Gonipterus scutellatus is a significant insect pest of eucalypts in most countries where that genus has been introduced, but is usually only of minor significance in its native Australia. Because of this, much of the research on its biology and host preferences has been done outside Australia. This fact has the potential to produce misleading results as the insect may be forced to choose less preferred hosts, if normally preferred species are unavailable. In part of its native range, in Tasmania, oviposition of G. scutellatus was recorded on seven naturally co-occurring Eucalyptus species that were planted in even aged, replicated plots. Among the seven species were the economically important species, E. globulus and E. viminalis, which have been previously reported as highly preferred hosts. Within plots, oviposition occurred most commonly on three peppermint species ( E. pulchella, E. tenuiramis and E. amygdalina) and was rare or absent on the other species ( E. globulus, E. viminalis, E. ovata and E. obliqua). Of the peppermints, E. pulchella was the most preferred species for oviposition at this site. A low percentage of peppermints in mixed forest (containing these seven species) immediately adjacent to plots was always matched by low numbers of G. scutellatus eggs within plots; but high percentages of peppermints outside plots could either be matched by high or low numbers of eggs within plots. In the discussion, we suggest that previous studies of G. scutellatus host range may have been limited because the insect was not exposed to hosts it naturally encounters.

Major pests of man-made forests in israel: origin, biology, damage and control

The important pests of the three main tree genera used in afforestation in Israel are described. The pine pests are the Israeli bast scale,Matsucoccus josephi; the pine processionary caterpillar,Thaumetopoea wilkinsoni; the bark beetlesOrthotomicus erosus, Pityogenes calcaratus andTomicus destruens; and the Mediterranean shoot moth,Rhyacionia buoliana thurificana. The cypress pests are the bark beetlesPhloeosinus armatus andP. aubei. The eucalypt borerPhoracantha semipunctata is the sole significant pest of eucalypts. All of these pests, except for the last, are considered endemic species which maintained themselves in the natural relict stands. Routine chemical control operations are conducted only againstT. wilkinsoni. Natural enemies are capable of keeping the other pest populations under good control if appropriate silvicultural measures and practices are in use.

THE LIFE HISTORY OF MNESAMPELA PRIVATA (GUEN.) (LEPIDOPTERA: GEOMETRIDAE) A DEFOLIATOR OF YOUNG EUCALYPTS

AbstractThe autumn gum moth, Mnesampela privata (Guen.), is a pest of eucalypts in southern Australia, often completely defoliating young trees, particularly those in the blue gum group. Its life cycle in southern Tasmania is described and notes on its host range and natural enemies are given. The pest status of M. privata is discussed in relation to future increases in the planting of susceptible species of eucalypts.