Mnesampela Privata Research Articles

Climate change impacts the risk of invasion of eucalypt pests in Brazil

Abstract Identifying areas at high risk of invasion is considered an important step for prioritization of phytosanitary measures to prevent biological invasions. Because climate change is likely to affect species' habitat suitability, ideally this should be considered in invasion risk assessments. We evaluated whether climate change affects habitat suitability and invasion risk of eight potentially invasive Eucalyptus pests in Brazil: Eucalyptolyma maideni, Mnesampela privata, Ophelimus maskelli, Orgyia postica, Paropsis atomaria, Paropsisterna beata, Paropsisterna cloelia and Trachymela sloanei. The shifts in the distribution range varied depending on the species, year and climate change scenario. While a decrease in the distribution range was predicted for four species, an increase was predicted for two species. Moreover, a decrease and/or increase in distribution depending on the climate change scenario was predicted for two species. Increases in invasion risk were predicted in major Eucalyptus‐producing areas near international airports and high cargo volume seaports. Our study provides an important contribution to knowledge on the effects of climate change on the distribution of eight potentially invasive Eucalyptus pests and reinforces the need to consider the changes in species' habitat suitability in invasion risk assessments.

Suitable areas for invasive insect pests in Brazil and the potential impacts for eucalyptus forestry.

Brazil is among the world's largest producers of eucalyptus and the damage caused by native and invasive insect pests is one of the main factors affecting eucalyptus yield. The recent history of biological invasions of eucalyptus pests in Brazil prompts demand for phytosanitary measures to prevent new invasions. This study used ecological niche models to estimate suitable areas for nine eucalyptus pests. This information was used to assess the potential ports of entry, generate invasion risk maps considering the likelihood of introducing invasive species, and estimate the eucalyptus producing municipalities and areas within the species' suitable range. A large distribution range was predicted for Eucalyptolyma maideni (Hempitera: Aphalaridae), Orgya postica (Lepidoptera: Erebidae), Sinoxylon anale (Coleoptera: Bostrichidae), and Trachymela sloanei (Coleoptera: Chrysomelidae) in Brazil, while a comparatively smaller distribution was predicted for Ophelimus maskelli (Hymenoptera: Eulophidae), Mnesampela privata (Lepidoptera: Geometridae), Paropsis atomaria (Coleoptera: Chrysomelidae), Paropsisterna beata, and P. cloelia (Coleoptera: Chrysomelidae). High-risk areas of invasion near airports and seaports were predicted mainly in southern, southeastern, and northeastern Brazil. A large proportion of the municipalities (24.4% to 93.7%) and areas with eucalyptus plantations (31.9% to 98.3%) are within the climatically suitable areas estimated for the pests, especially in southern and southeastern regions, which comprises 61.5% of the Brazilian eucalyptus production. The results indicate that eucalyptus forestry may be significantly impacted by biological invasion. The findings provided by our study can assist decision-makers in developing phytosanitary measures to prevent new invasions of forest pests in Brazil. © 2022 Society of Chemical Industry.

Direct and indirect effects of marsupial browsing on a foundation tree species

Plant-mediated indirect effects can be important ecological drivers in plant communities, especially in systems where extended genetic effects of foundation species can shape communities and influence ecosystem dynamics. Here we investigate the direct and indirect effects of uncontrolled browsing by marsupial herbivores including the common brushtail possum Trichosurus vulpecula, Bennetts wallaby Macropus rufogriseus and the red-bellied pademelon Thylogale billardierii, in a Eucalyptus system known to have extended community and ecosystem genetic effects. In a common garden trial containing 525 full-sib families from an incomplete diallel crossing program located in northeastern Tasmania, Australia, we assessed the genetic basis to herbivore preferences, the impact of a single and repeated marsupial browsing event on tree fitness and morphological traits and the associated indirect plant-mediated effects on a subsequent herbivore, autumn gum moth Mnesampela privata. Marsupial browsing was not influenced by plant genetics, but spatial components instead affected the pattern of damage across the trial. Marsupial browsing had significant impacts on tree development, morphology and survival, resulting in reductions in survival, height and basal area, an increase proportion in multiple stems, delays in flowering as well as delays in phase change from juvenile to adult foliage. Fitness impacts were minimal in response to a once-off browsing event, but effects were exacerbated when trees suffered repeated browsing. We demonstrate clear plant-mediated indirect effects of marsupial browsing on subsequent tree use by an invertebrate herbivore, through induced changes in plant morphology. Such indirect effects have the potential to influence biotic community structure on a foundation species host-plant, and the evolutionary interactions that occur between organisms and the host-plant themselves.

Delayed mating and reproduction in the autumn gum moth Mnesampela privata

1 The success of mating disruption using synthetic sex pheromones depends not only on preventing mating, but also on delaying mating in the target insect. Using the geometrid pest of Eucalyptus plantations, Mnesampela privata (Guen´ee), we determined the effect of delaying mating when imposed on males only, females only or on both sexes simultaneously, for 1, 3, 5 and 7 days. 2 Delayed mating had a significant negative impact on reproduction, with a 0.89-fold decrease in the likelihood of mating and a 0.67-fold decrease in the likelihood of that mating resulting in fertile eggs for every day that mating is delayed. A mating delay of 7 days reduced the mean number of viable eggs laid to 4–13% of that laid by moths paired immediately after emergence. 3 Male only imposed mating delays had a significantly lower effect on reducing the likelihood of pairs mating than when both sexes were delayed. A delay imposed on one sex only or on both sexes simultaneously, however, had a similar negative impact on the proportion of fertile matings as well as on the total number of fertile eggs laid. 4 Longevity of mated female and male M. privata was significantly different between mating delay treatments, with a significant decline in female longevity when they mated with older males. 5 The underlying mechanisms causing a decline in female reproductive output when a mating delay was imposed on males versus females are discussed in relation to the reproductive biology of M. privata and the potential of using mating disruption strategies to control populations in Eucalyptus plantations.

Mating frequency and reproductive success in an income breeding moth, Mnesampela privata

AbstractThe frequency of mating in insects is often an important determinant of female reproductive output and male sperm competition. In Lepidoptera that provide male nutrients to the female when mating, it is hypothesized that polyandry may be more prevalent. This is thought to be especially so among species described as income breeders; that is, in species who do not derive all their nutrients for reproductive output entirely from the resources obtained during the larval stage. We selected the geometrid moth, Mnesampela privata (Guenée) (Lepidoptera: Geometridae), to examine this hypothesis further. We found this species was best characterized as an income breeder with female weight on emergence positively correlated with total egg load but not with the number of eggs laid. Further, in accord with income breeders, females emerged with a partially developed egg load and lifetime fecundity was positively correlated with the number of oviposition days. However, in the laboratory we found that incidence of repeated matings or polyandry was rare. When moths were paired singly over their lifetime, only 4% of mated females multiple mated. When females were paired with three males concurrently, female mating success increased from 60 to 81% with multiple mating among mated females increasing to just 15%. Dissection of wild caught M. privata found that polyandry levels were also low with a maximum of 16.4% of females collected at any one time being multiple mated. In accord with theory, mating significantly increased the longevity of females, but not of males, suggesting that females acquire essential resources from male ejaculates. Despite this, multiple mated females showed a trend toward decreasing rather than increasing female reproductive output. Spermatophore size, measured on death of the female, was not correlated with male or female forewing length but was negatively correlated with the number of fertile eggs laid and female longevity. Smaller spermatophore width may be related to uptake of more nutrients by the female from a spermatophore. We discuss our findings in relation to income breeding and its relationship to polyandry in Lepidoptera.

Identification, Synthesis and Field Testing of (3Z,6Z,9Z)-3,6,9-Henicosatriene, a Second Bioactive Component of the Sex Pheromone of the Autumn Gum Moth, Mnesampela privata

The sex pheromone of Mnesampela privata, an endemic pest of Eucalyptus plantations in Australia, was previously identified as a single bioactive compound, (3Z,6Z,9Z)-3,6,9-nonadecatriene (C19 triene). Initial field testing of lures containing 1 mg, 5 mg or 10 mg of C19 triene (>98% purity) caught no or very few male M. privata. (3Z,6Z,9Z)-3,6,9-Henicosatriene (C21 triene) was identified as an additional minor pheromone component in abdominal tip extracts of M. privata females from Tasmania. Levels of both compounds extracted from individual females varied greatly, but the ratio was relatively constant at 33:1 C19:C21 trienes. Electroantennograms (EAG) of synthetic C21 triene with male M. privata gave positive but consistently lower responses than elicited by the C19 triene. Field tests showed that the addition of 1-6% C21 triene to 1 mg C19 triene significantly increased trap catch and the detection of M. privata in plantations. Traps baited with a 16:1 ratio caught significantly more moths than those baited with a ratio approximating that of females.

Tarsal taste sensilla of the autumn gum moth, Mnesampela privata: morphology and electrophysiological activity

Abstract Mnesampela privata Guenée (Lepidoptera: Geometridae: Ennominae) is a native Australian geometrid that conducts considerable host assessment prior to ovipositing on its host plants, which belong to the genus Eucalyptus. The leaves of some of their hosts are covered with a particularly thick and waxy cuticle and we have shown that epicuticular waxes influence the oviposition preferences of females. This necessitates that M. privata has evolved specific chemosensory organs to assess the identity and perhaps even the quality of its hosts. In this work, we examined the morphology of tarsal taste sensilla and the sensitivity of their sensory neurones to a range of primary metabolites possibly influential on host assessment and oviposition. The ventral surface of the fifth tarsomere of females bear two parallel rows of up to eight sensilla, each loosely aligned with two parallel rows of five spines. Salts, sugars, and amino acids elicited phasi‐tonic multicellular neuronal responses of variable magnitude and form. Two pairs of sensilla are closely apposed to the most distal spine in each row; the sensory neurones associated with these sensilla exhibited notably larger responses to alanine and serine compared with those of all other sensilla. The arrangement of the taste sensilla in close proximity to prominent tarsal spines is unique and could represent an adaptation that enables them to penetrate the wax layer and be brought into contact with primary metabolites present closer to the leaf surface.

Long-term realised and projected growth impacts caused by autumn gum moth defoliation of 2-year-old Eucalyptus nitens plantation trees in Tasmania, Australia

Insect damage to production forests has the potential to reduce financial returns by retarding tree growth and causing mortality, however, long-term realised quantification of these losses is rare. In order to help elucidate economic damage thresholds for making spray decisions we capitalised on a natural outbreak of autumn gum moth, Mnesampela privata, in a 2-year-old Eucalyptus nitens plantation. Following the partial chemical control of this insect outbreak we measured the tree growth variables diameter at breast height over bark and height of five differing tree defoliation classes for 75 months following tree damage. At the end of this period a threshold model was fitted to describe the relationship between tree defoliation and realised tree wood volumes. The model revealed that realised stand wood volume was not significantly affected up until defoliation exceeded 60% and then declined sharply after this defoliation level was reached. Further support for this defoliation threshold was evident from multiple comparisons among defoliation classes that showed 50% defoliated trees did not have significantly different wood volume compared to more lightly defoliated trees, but did have significantly greater wood volume compared to trees that were 72% or more defoliated. To determine if the realised differences in wood volume resulted in differences in yield over a plantation rotation the E. nitens growth model NITGRO was used to on-grow trees to age 15 years for a ‘best case’ (type 1 growth response, constant growth rates from last inventory until harvest) and ‘worst case’ (type 2 growth response, divergent growth rates from last inventory until harvest) scenario. The threshold model was then fitted to the outcomes of both scenarios and the economic consequences of defoliation were clearly dependent on the growth function assumed.

Life history and behavioural traits of Mnesampela privata that exacerbate population responses to eucalypt plantations: Comparisons with Australian and outbreak species of forest geometrid from the Northern Hemisphere

Life history and behavioural traits of Mnesampela privata that exacerbate population responses to eucalypt plantations: Comparisons with Australian and outbreak species of forest geometrid from the Northern Hemisphere

Causes and Consequences of Host Expansion by Mnesampela privata

The autumn gum moth, Mnesampela privata, utilizes several species of Eucalyptus planted outside regions of endemism within Australia. We investigated whether foliar monoterpene composition influenced oviposition in the field on the natural primary host (E. globulus) and a novel host (E. rubida), both characterized by nonstructural epicuticular waxes. In the laboratory, oviposition preferences of females for species and families of known host, novel hosts, and non-hosts that were characterized by both nonstructural and structural waxes but also varied in foliar concentrations of the purportedly toxic plant secondary metabolite (sideroxylonal) were studied. Although M. privata laid as many eggs on trees of two families of E. rubida as they did on trees of two families of E. globulus, there were significant differences in the numbers of clutches of eggs laid. When combined with data for oviposition on another five families of E. globulus, we found a negative relationship between mean numbers of eggs and foliar concentration of alpha-pinene but a positive relationship between egg numbers and the concentration of alpha-terpineol. The field data suggest that female M. privata are just as willing to lay eggs on novel hosts with comparable foliar monoterpene compositions to those of the primary host, especially if they produce nonstructural epicuticular waxes. Oviposition assays in the laboratory endorse this mechanism of host plant hierarchy and support the long-held assumption of the host primacy of E. globulus. In laboratory assays, some larvae pupated on all hosts (except Corymbia eximia) but the number completing larval development was greater on hosts with softer leaves. Larval survival was also reduced on hosts with high concentrations of sideroxylonal but only if those hosts also had modest to high concentrations of monoterpenes. Larval survival was high on a host (E. macarthurii) with a high concentration of sideroxylonal but with virtually zero monoterpene content. This suggests that the monoterpene content of a host could antagonize the effect on M. privata larvae of its sideroxylonal content. The larval food plant most affected the fitness of female rather than male pupae. Of the known host expansion events, all have occurred in mixed species plantations. The co-occurrence in these plantations of either the primary host or other highly ranked species probably explains the eventual expansion onto the neighboring species of Eucalyptus and Corymbia.

Monitoring autumn gum moth (Mnesampela privata): relationships between pheromone and light trap catches and oviposition in eucalypt plantations

Summary Following the identification of a biologically-active compound from the sex pheromone gland of the autumn gum moth, Mnesampela privata (Guenée) (Lepidoptera: Geometridae), field studies were conducted to compare the potential efficacy of pheromone traps with light traps and to determine whether pheromone trap catches could forecast the future abundance of eggs and subsequent defoliation. Small to incipient populations of the adult moth were monitored over two moth flight seasons using pheromone traps in 12 plantations of either Eucalyptus globulus Labill. or E. nitens (Deane and Maiden) Maiden in Tasmania, Australia. In three of these plantations, light traps were also used to monitor adult moth numbers for one moth flight season. Pheromone trap catches from Tasmania were compared with those in a plantation of E. grandis W.Hill ex Maiden in Victoria where an outbreak of M. privata was ongoing. Early in the season (February—April), light traps caught five to six times more M. privata than pheromone traps per week but this situation reversed later in the season (May). Although small, total pheromone trap catches of male moths during March—April 2003 were positively correlated with the total numbers of eggs per tree recorded in June. Catches were substantially larger during March-July 2004 and again positively correlated with the total numbers of eggs per tree recorded in July. Sixty-nine percent of all eggs located in 2003 were parasitised compared with only 18% in 2004. Because pheromone trap catches could be positively correlated with oviposition, it is suggested they could forecast larval populations and, in the absence of high rates of egg parasitism, defoliation.

How Does Host Abundance Affect Oviposition and Fecundity ofMnesampela privata(Lepidoptera: Geometridae)?

In native forests in Australia, Mnesampela privata (Guenee) is uncommon, but in plantations, populations can outbreak. Two field trials (GES1 and GES2) were used to test whether oviposition on individual hosts by M. privata increases under plantation conditions of high host abundance. Oviposition on designated target trees was recorded over two consecutive seasons in arboreta where the relative abundance of preferred Eucalyptus hosts decreased, whereas the relative abundance of less preferred or noneucalypt trees increased. Neither trial supported the hypothesis that more eggs are laid on individual hosts when surrounded by trees of the same species. On the contrary, in the third arboretum type in GES2 (lowest relative abundance of eucalypts), more eggs were laid on target eucalypts whose immediate neighboring trees were noneucalypts. The average size of egg clutches increased between 1.3 and 11.7 times from the first to the second season of surveys, and the weight of females increased over the two consecutive seasons, which may have explained the increase in egg clutch size. It is proposed that outbreaks of M. privata occur in eucalypt plantations because high host abundance (and presumably also quality) drives the development of populations that are larger than can be supported by native forests.

Suitability of Eucalyptus and Corymbia for Mnesampela privata (Guenée) (Lepidoptera: Geometridae) larvae

Abstract 1 Mnesampela privata (Guenée) has a host list of 40 Eucalyptus and at least one Corymbia species. Larval survival and performance was studied on 19 species to investigate how certain leaf traits influence the suitability of different species.2 After 7 days, survival on Eucalyptus aggregata and Eucalyptus camphora is greater than 70% even though the toughness of leaves is 0.15–0.19 mg/mm2. However, after the same time, survival on genotypes of Eucalyptus melliodora and Eucalyptus sideroxylon was less than 60%, or even 0%, even though the toughness of some leaves was as low as 0.11 mg/mm2. An unmeasured allelochemical, rather than toughness, may reduce survival on these species.3 Dry weights of first‐instar larvae were negatively correlated with leaf toughness for 13 of the species studied. Species that produced the heaviest first‐instar larvae were not the same hosts that produced the heaviest second‐instar larvae.4 Dry weights of female pupae were negatively correlated with total oil content for five of the species studied.5 Larvae exhibit age‐related changes in feeding behaviour. Neonates skeletonize leaves (avoid leaf veins and oil glands) and post‐third‐instar larvae ingest whole leaf fragments (consume small leaf veins and oil glands). These findings suggest that neonates are sensitive to high leaf toughness and non‐oil plant secondary metabolites whereas older larvae are less sensitive to high leaf toughness and are likely to become larger adults on hosts with lower oil contents.

Identification, synthesis and activity of sex pheromone gland components of the autumn gum moth (Lepidoptera: Geometridae), a defoliator of Eucalyptus

The autumn gum moth, Mnesampela privata (Guenee) (Lepidoptera: Geometridae), is native to Australia and can be a pest of plantation eucalypts. Field-collected and laboratory-reared female autumn gum moths were dissected to remove glands likely to contain components of the sex pheromone. Using gas chromatography (GC) and combined gas chromatography-mass spectrometry (GC-MS), three compounds were identified from female extracts, namely (3Z,6Z,9Z)-3,6,9-nonadecatriene, 1-hexadecanol and 1-octadecanol (confirmed by comparison with synthetic samples). Nonadecatriene elicited an antennal response in male autumn gum moth during gas chromatographic analyses combined with electroantennographic detection (GC-EAD). In electroantennogram (EAG) recording male M. privata antennae responded to the nonadecatriene. Nonadecatriene was synthesised via Kolbe electrolysis, starting with (9Z,12Z,15Z)-octadeca-9,12,15-trienoic acid (linolenic acid) and propanoic acid or via an alternative four-step method also starting from linolenic acid. In field trials (3Z,6Z,9Z)-3,6,9-nonadecatriene proved attractive to male moths. Thus, we conclude that (3Z,6Z,9Z)-3,6,9-nonadecatriene is a sex pheromone component of autumn gum moth. This component has been identified in extracts from other geometrids in the same subfamily, Ennominae. However, to our knowledge this is the first example where (3Z,6Z,9Z)-3,6,9-nonadecatriene has been found in females and also proved attractive to male moths when presented on its own. Our results are discussed in relation to other geometrid pheromones.

Susceptibility of Eucalyptus globulus to Mnesampela privata defoliation in relation to a specific foliar wax compound

Increased abundance of several aliphatic benzyl and phenylethyl alkanoates were previously associated with reduced defoliation of Eucalyptus globulus Labill. by the autumn gum moth (Mnesampela privata Guenee) in two clonally replicated F2 families. We examine the robustness of this association by comparing the abundance of the implicated foliar wax compounds with defoliation levels in three plantation sites and a genetics trial in northern Tasmania. At all locations, the aliphatic alkanoate, benzyl n-tetracosanoate (C24), was found in significantly higher abundance in the foliar wax of E. globulus trees that had displayed low M. privata damage (designated resistant) compared to trees that had displayed high damage (designated susceptible). Further, when sites were combined, benzyl n-tetracosanoate (C24) accounted for 16 % of variation in field defoliation. Field defoliation was also positively correlated to M. privata oviposition both in the field and on foliage sprigs in a cage. In the cage bioassay, oviposition accounted for 20 % of variation in field defoliation making it a better predictor of tree defoliation in the field than either field oviposition, which accounted for 9 % of variation, or screening foliage for the abundance of benzyl n-tetracosanoate (C24). Despite both benzyl n-tetracosanoate (C24) and oviposition being related to field defoliation, there was no statistically significant relationship between the abundance of benzyl n-tetracosanoate (C24) and oviposition in the field or cage bioassay. Further work is therefore required to determine if increased levels of this compound in the foliar wax operates as a direct deterrent to M. privataoviposition.

Oviposition by autumn gum moth (Mnesampela privata) in relation to Eucalyptus globulus defoliation, larval performance and natural enemies

Abstract 1 Eucalyptus globulus Labill. exhibited consistent intraspecific variation in oviposition choice by Mnesampela privata (Guenée) (Lepidoptera: Geometridae) in field surveys of host plants that had been designated, based on the prior season's defoliation levels, as resistant or susceptible to M. privata. At both field sites significantly fewer egg batches were found on resistant compared to susceptible trees.2 In cage bioassays we demonstrated a significant oviposition preference by M. privata, with over two‐fold greater number of egg batches laid on foliage sprigs from susceptible compared to resistant trees. Despite differences in tree oviposition choice, we found no evidence in the field or the laboratory of adult females adjusting egg batch size in accordance to oviposition preference.3 Caged larval survival, development times and pupal weight did not vary significantly between resistant and susceptible trees. Similarly, in a laboratory feeding experiment, neonates utilized resistant and susceptible foliage equally.4 Larval mortality in the field attributed to natural enemies did not vary significantly between resistant and susceptible trees, nor did the percentage of Telenomus sp. parasitism of M. privata eggs within a batch and batches per tree.5 Failure to associate either larval performance or natural enemy efficacy with the observed intraspecific variation in E. globulus susceptibility to M. privata oviposition indicates that some other unidentified factors drive the evolution of host selection for oviposition.

Modelling a forest lepidopteran: phenological plasticity determines voltinism which influences population dynamics

Mnesampela privata is an Australian geometrid moth that is considered to have resource-driven outbreaks. An autumnal oviposition/larval development cycle is considered the “norm” in this species, but spring/summer activity has also been observed. This apparent plasticity of phenology and probable concomitant changes in voltinism have not been considered as possible causes of moth outbreaks. We developed GumMoth, a phenological model for M. privata that uses temperature to predict development times of immatures. Photoperiod determines whether individuals undergo direct development or pupal diapause. We used known catch dates of moths (in the same moth-active season or 365-day period) to simulate population phenologies on the Australian mainland (27°28′S to 38°14′S) and in Tasmania (40°54′S to 42°57′S). GumMoth successfully simulated phenological patterns that agreed with published records and demonstrated for the first time that multivoltinism is possible in M. privata. In seven paired simulations using dates for first and last moth catches, the earliest moth activity resulted in the pupae of four out of 11 generations undergoing diapause, whereas the latest moth activity resulted in pupae of five out of eight generations undergoing diapause (diapause individuals emerged the following moth-active season). Almost two-thirds of offspring of spring/summer active moths reached adulthood within that same moth-active season (i.e. no delay in development), whereas those of autumn active moths always reached adulthood the following moth-active season (i.e. development was delayed). Records from foresters and in the scientific literature confirmed that the more common autumn phenology is supplemented by spring/summer activity in many localities. At half of these localities, populations that required insecticide control or caused substantial defoliation also developed. Because plantation eucalypts are suitable M. privata hosts for only four to five tree-growth seasons after planting, local moth populations must increase quickly if an outbreak is to occur. We suggest that large populations are more likely when plantations are colonised in the first moth-active season after planting and population growth commences in the spring/summer of each subsequent year. Foresters can use catch dates and regional weather data in GumMoth to estimate the number and phenology of generations of M. privata. This information can be used to assess risk posed by regional populations and thereby adjust future surveillance intensity.

Genetic variation of Eucalyptus globulus in relation to autumn gum moth Mnesampela privata (Lepidoptera: Geometridae) oviposition preference

The autumn gum moth Mnesampela privata Guenée is a major defoliator of Australia’s commercially important pulpwood plantation species, Eucalyptus globulus Labill. However, little is known about genetic variability of E. globulus to M. privata oviposition preference. We examined oviposition preference by exposing juvenile foliage sprigs of different genetic origins to gravid female moths in cage bioassays. Foliage sprigs were collected from 40 E. globulus families grown in a common environment field trial in southern Tasmania. These families were derived from open-pollinated seed collected in native stands and represented four geographic races of E. globulus. Significant differences in the level of oviposition was detected between foliage sprigs from the different races, with those from the Furneaux race receiving over twice as many egg batches compared to those from either the Strzelecki Ranges or northeastern Tasmania races. The southern Tasmania race received an intermediate egg load. No significant variability in oviposition preference was identified between different localities within races or between different open-pollinated families within localities. Selections from both the Strzelecki Ranges and Furneaux races comprise a large component of the Australian E. globulus breeding population. There is therefore likely to be significant genetic variation for M. privata oviposition preference within the breeding population and by screening before deployment gains in plantation productivity in areas subject to M. privata outbreaks may be possible.

Genetic variation of Eucalyptus globulus in relation to autumn gum moth Mnesampela privata (Lepidoptera: Geometridae) oviposition preference

The autumn gum moth Mnesampela privata Guenée is a major defoliator of Australia’s commercially important pulpwood plantation species, Eucalyptus globulus Labill. However, little is known about genetic variability of E. globulus to M. privata oviposition preference. We examined oviposition preference by exposing juvenile foliage sprigs of different genetic origins to gravid female moths in cage bioassays. Foliage sprigs were collected from 40 E. globulus families grown in a common environment field trial in southern Tasmania. These families were derived from open-pollinated seed collected in native stands and represented four geographic races of E. globulus. Significant differences in the level of oviposition was detected between foliage sprigs from the different races, with those from the Furneaux race receiving over twice as many egg batches compared to those from either the Strzelecki Ranges or northeastern Tasmania races. The southern Tasmania race received an intermediate egg load. No significant variability in oviposition preference was identified between different localities within races or between different open-pollinated families within localities. Selections from both the Strzelecki Ranges and Furneaux races comprise a large component of the Australian E. globulus breeding population. There is therefore likely to be significant genetic variation for M. privata oviposition preference within the breeding population and by screening before deployment gains in plantation productivity in areas subject to M. privata outbreaks may be possible.

Floral nectar versus honey dew as food for wasp parasitoids: implications for pest management in eucalypt plantations

Summary The longevities of two species of native wasp parasitoid (Heteropelma scaposum (Morley) and Habronyx pammi (Gauld)) given floral nectar and honeydew from scale insects are compared. These parasitoids kill autumn gum moth (Mnesampela privata (Guenée)) which can outbreak in eucalypt plantations and cause considerable defoliation. The longevities of male He. scaposum given access to flowering Alyssum maritimum and Aster ‘Easter Daisy’ (both exotics) were no different from those of starved wasps. Hence, inter-row sowings of these plants in plantations on ex-pasture sites are unlikely to benefit these parasitoids. Compared to starved individuals, males of both species usually lived longer when given access to Eucalyptus globulus subsp. globulus leaves. Leaves from the previous season enabled male He. scaposum to live longer than did current season's leaves. The inference that it was honeydew on the surfaces of E. globulus subsp. globulus leaves that increased the longevities of both species of wasp was supported when Ha. pammi were found to live almost three times as long as starved wasps when provided with branchlets supporting colonies of live scale insects (Eriococcus species). The longevities of female Ha. pammi as well as males of a Pristiceros species were also increased when they were given access to branchlets with scale insect colonies. Both He. scaposum and Ha. pammi were seen feeding on honeydew in the wild (but not on flowers). Appreciating that the presence of scale insects on some plantation trees can benefit native parasitoids is in keeping with an ecologically sustainable approach to pest management.