Three different patterns of feeding of sixth-instar spruce budworm, Choristoneura fumiferana Clemens were simulated in the laboratory. Larvae were fed artificial diets whose nitrogen and total soluble sugar contents varied according to levels similar to those found in three types of balsam fir, Abies balsamea (L.) Miller foliage (current-year foliage from middle and lower crown sections and one-year-old foliage). The biological performance of offspring was studied according to the nutrition of their parents. Although food quality had no impact on pupal weight of female parents and individual mean egg weight, progeny fitness was influenced by parental nutrition. Old foliage simulated diet, poor in nitrogen, clearly affected the early larval development of progeny, especially the percent of egg hatch and first-instar survival. Lower crown current-year foliage simulated diet, with low total soluble sugar content, reduced the first-instar survival of the progeny. However, the selective pressure exerted by low food qualities on the parental generation and on the early stages of their progenies resulted in C. fumiferana populations having higher tolerance to starvation and higher survival after the diapause period. These results highlighted the potentially direct and indirect effects of C. fumiferana parental nutrition on the next generation. The patterns of feeding of parental generations would appear to affect the quality and size of subsequent populations through several selections on the different life-history stages of both generations.

In Japan, several forest-defoliating insects reach outbreak levels and cause serious defoliation. Stand mortality sometimes occurs after severe defoliation. However, in general, tree mortality caused by insect defoliation is low because of the prevailing moist climate in Japan. Evergreen conifers are more susceptible to tree mortality as a result of insect defoliation whereas deciduous broad-leaved trees are seldom killed. Insect defoliation occurs more frequently in man-made environments such as among shade trees, orchards, and plantations than in natural habitats. Outbreaks of some defoliators tend to occur in stands of a particular age: e.g. outbreaks of the pine caterpillar, Dendrolimus spectabilis Butler (Lepidoptera: Lasiocampidae) occur more frequently in young pine plantations. In contrast, defoliation caused by outbreaks of lepidopterous and hymenopterous pests in larch plantations is more frequent with stand maturation. There is a relationship between outbreaks of some defoliators and altitude above sea level. Most outbreaks of forest defoliators were terminated by insect pathogens that operated in a density-dependent fashion. Since the 1970s, Japan has been prosperous and can afford to buy timber from abroad. More recently, there has been an increasing demand for timber in Japan, that coincides with a huge demand internationally, so that the country will need to produce more timber locally in the future. The increasing pressure on the forestry industry to meet this demand will require more sophisticated methods of pest control coupled with more sustainable methods of silviculture.

Deciduous oak dieback in Japan has been known since the 1930s, but in the last ten years epidemics have intensified and spread to the island’s western coastal areas. The symbiotic ambrosia fungus Raffaelea sp. is the causal agent of oak dieback, and is vectored by Platypus quercivorus (Murayama). This is the first example of an ambrosia beetle fungus that kills vigorous trees. Mortality of Quercus crispula was approximately 40% but much lower for associated species of Fagaceae, even though each species had a similar number of beetle attacks. It is likely that other oaks resistant to the fungus evolved under a stable relationship between the tree, fungus and beetle during a long evolutionary process. Quercus crispula was probably not part of this coevolution. This hypothesis was supported by the fact that P. quercivorus showed the least preference for Q. crispulayet exhibited highest reproductive success in this species. Therefore, P. quercivorus could spread more rapidly in stands with a high composition of Q. crispula. The present oak dieback epidemic in Japan probably resulted from the warmer climate that occurred from the late 1980s which made possible the fateful encounter of P. quercivorus with Q. cripsula by allowing the beetle to extend its distribution to more northerly latitudes and higher altitudes. Future global warming will possibly accelerate the overlapping of the distributions of P. quercivorus and Q. crispula with the result that oak dieback in Q. crispula will become more prevalent in Japan.

Temperature and food quality can both influence growth rates, consumption rates, utilization efficiencies and developmental time of herbivorous insects. Gravimetric analyses were conducted during two consecutive years to assess the effects of temperature and food quality on fourth instar larvae of the forest tent caterpillar Malacosoma disstria Hübner. Larvae were reared in the laboratory at three different temperatures (18, 24 and 30°C) and on two types of diet; leaves of sugar maple trees Acer saccharum Marsh. located at the forest edge (sun-exposed leaves) or within the forest interior (shade-exposed leaves). In general, larvae reared at 18°C had lower growth rates and lower consumption rates than larvae reared at the warmer temperatures (24 and 30°C). Moreover, the duration of the instar decreased significantly with increasing temperatures. Type of diet also affected the growth rates and amount of food ingested by larvae but did not affect the duration of the instar. Larvae fed sun-exposed leaves consumed more food and gained higher biomasses. Values of approximate digestibility and efficiency of conversion of ingested food were also higher when larvae were fed sun-exposed leaves. Higher growth rates with increasing temperatures were primarily the result of the shorter stadium duration. The higher growth rates of larvae fed sun-exposed leaves were possibly the result of stimulatory feeding and consequently greater food intake and also a more efficient use of food ingested. This study suggests that the performance of M. disstria caterpillars could be enhanced by warmer temperatures and higher leaf quality.

Needle defoliation by diprionid sawflies decreases the increment and timber yield of Scots pine Pinus sylvestris L. The aim of this study was to provide approximate estimates of this decrease and preliminary estimates of the economic value of growth losses and tree mortality. Growth loss after needle damage by Diprion pini(Linnaeus) was studied in western Finland. Increment cores were sampled for radial growth measurements from trees subjected to slight, moderate and heavy defoliation. A literature survey was carried out to estimate radial growth losses after defoliation by Neodiprion sertifer (Geoffroy). Calculations for economic consequences were based on previous estimates and on the ongoing 9th Finnish National Forest Inventory. Moderate defoliation by N. sertifer and D. pini reduced volume growth by 21% and 86% and heavy defoliation by 38% and 94%, respectively. Tree mortality in defoliated stands was recorded as approximately 4%after an outbreak of N. sertifer and 30% after an outbreak of D. pini. The estimated average economic value of the losses due to reduced growth and tree mortality reached $40 ha−1 after a single-year outbreak of N. sertifer and $310 ha−1 in the case of D. pini. These preliminary estimates of economic losses indicate a much higher impact of pine sawflies than those revealed by the few earlier studies in Europe.

Two species of cerambycid beetles that attack eucalypts, Phoracantha semipunctata(Fabricius) and P. recurva Newman, have been accidentally introduced from Australia into most regions of the world in which their hosts have been planted. The beetles cause extensive mortality in plantations and landscape plantings of the trees. Management programmes have focused on integration of silvicultural practices, host plant resistance and biological control. To rear and release natural enemies of the larval stages of the beetles in California, mass rearing protocols for continuous production of two species of parasitoids have been developed. The methods described represent the first long-term and large-scale techniques for mass rearing parasitoids of any wood-boring cerambycid species. In addition to providing large numbers of parasitoids for releases, the mass rearing effort has also provided large numbers of parasitoids for fundamental studies of their biology and behaviour.

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.

The spatial distribution of blowflies of the genus Lucilia within fields in south west England was examined in 1999 and 2000. Blowflies are economically important agents of sheep myiasis in the UK and understanding local aggregation is an essential step in the development of appropriate sampling and fly control regimes. Fifty, 20 × 20 cm, non-odour-baited, sticky traps were used to catch flies, at randomized, 10 × 10 m grid co-ordinates in fields of permanent pasture. Clear aggregations were evident in all Lucilia distributions. All values of the σ2:mean ratio were greater than 1. The catches were shown to be highly aggregated using Morisita’s index of aggregation. Generalized linear modelling of binary presence/absence catch data was used to relate aggregation to microclimate and habitat. Deletion testing was used to identify significant terms in the models. In general, Lucilia blowflies were predominantly caught around the edges, in warmer and more humid areas of the field. The relationship between microhabitat and the distribution of Lucilia collected in 1999 was used as predictive model to explain the catches made in two fields in 2000. This gave a highly significant fit in one field (P = 0.001) and a relationship which approached significance in the second (P = 0.08). However, these regressions suggest that the relationships between abundance and microhabitat are complex and that ‘hot spots’ of blowfly catches were not necessarily found in the most extreme microclimate conditions. Nevertheless, microhabitat features do give a relatively good guide to presence or absence of Lucilia in the trap catches, thereby providing important information about the most appropriate location of traps to maximize and standardize sampling and control regimes.

Elucidation of the genetic variability of a model insect species, the grain aphid, Sitobion avenae (Fabricius), a predominantly asexual herbivore within the temperate agro-ecosystem tested, was initiated using molecular DNA markers (RAPDs). This revealed genetic profiles that appeared related to host adaptation at the specific level amongst the natural populations colonizing different grasses and cereals (Poaceae) within the same geographic location. These profiles were recorded either as ‘specialist’genotypes found on specific grasses, or as ‘generalist’ genotypes colonizing several host types including cultivated cereals or native grasses. These findings are compared with analogous systems found amongst insect species, including at a higher trophic level, i.e. interactions between hymenopterous aphid parasitoids. As the aphids and their respective plant hosts occur in the same geographical region at the same time, this appears to be a rare example of the evolutionary transition leading to sympatric speciation in insects. Hence, this study highlights the importance of understanding not only the demographic parameters to genetic diversity, but also the more intricate correlation of genetic diversity to host types in agricultural environments.

Several series of host-reared specimens of an Encarsia species, initially thought to be the cosmopolitan Encarsia inaron (Walker), were collected in the Azores Islands (Portugal). Subsequent morphometric analysis supported the presence of two species: E. inaron and a new species, described herein as Encarsia estrellae Manzari & Polaszek sp. n.Encarsia estrellae was reared from Aleyrodes singularis Danzig, A. ?singularis, and Bemisia sp. afer-group on several host plants. In addition, the D2 region of the 28S rDNA gene was sequenced in eight individuals belonging to these species, as well as single representatives of two closely related and one distantly related species. Phylogenetic analysis of these DNA sequences, together with 23 additional Encarsia sequences retrieved from the European Molecular Biology Laboratory (EMBL) and GenBank databases, further supported the specific status of E. estrellae, and the placement of E. dichroa (Mercet) in the E. inaron species-group. Additionally, E. inaron is redescribed and some taxonomic problems in the E. inaron species-group are discussed.

For most plant species, tolerance to many types of herbivory increases as plants age, but the applicability of this pattern to root herbivory has not been tested. Injury to roots of rice plants by larvae of the rice water weevil, Lissorhoptrus oryzophilus Kuschel, causes severe reductions in yields in the United States. It is generally thought that young rice plants, because their root systems are smaller, are less tolerant than older plants of root feeding by L. oryzophilus. Field experiments were conducted to test this hypothesis. Plots of rice (4.7 to 6.5 m2) were established and subjected to natural infestations of L. oryzophilus larvae. A soil insecticide was applied to plots at different times during the tillering phase of rice in order to manipulate the timing of weevil infestation. The impact of these treatments (timings of insecticide applications) was assessed by comparing relationships between yield loss and larval pressure for each treatment using analysis of covariance. Yield losses ranged from 13% to over 40% in plots not treated with insecticide. Patterns of yield losses from plots treated with insecticide at different times were best explained by the hypothesis that yield loss is determined both by the age of plants infested and by the size of larvae infesting plants. Young plants appear to be less tolerant than older plants, and feeding by large larvae appears to be more deleterious than feeding by smaller larvae. Management practices that delay infestation of rice by L. oryzophilus until plants are older may be an important component of management programmes for this pest.