Where to sample? Ecological implications of sampling strata in determining abundance and impact of natural enemies of the coffee berry borer,Hypothenemus hampei

Several parasitoids of African origin have been introduced to coffee producing areas of the Americas and Asia as biological control agents of the coffee berry borer (CBB) Hypothenemus hampei (Coleoptera: Curculionidae). These parasitoids have become established in the field but their effect on the CBB has been limited. A two-year field study in Western Kenya has found Prorops nasuta (Hymenoptera: Bethylidae) to be the predominant parasitoid emerging from CBB-infested coffee berries collected on coffee trees or from the ground. P. nasuta comprises more than 75% of the total natural enemies collected. The density of P. nasuta was 90% higher in the berries collected from the ground than from the trees. Its hyperparasitoid, Aphanogmus sp. (Hymenoptera: Ceraphronidae), also emerged from both type of berries. Across the two seasons, the average P. nasuta density per berry was 18–35 times higher than that of Aphanogmus sp. Throughout the two years sampled, significantly higher numbers of P. nasuta and Aphanogmus sp. occurred between February and March, which coincides with the beginning of the rainy season. Higher numbers of live CBB females were recorded in berries collected from the trees. Nevertheless, mortality of adult CBB was considerably higher from January to March and started to decrease from April onwards. The possibly negative effects of cultural control practices in Latin America which include the removal of berries fallen to the ground on biological control of CBB are discussed, and the use of screened collection devices for these berries which would permit the release of parasitoids but prevent escape of the pest is proposed.     

"Conilon" coffee berries bored by Hypothenemus hampei (Ferrari) (Coleoptera: Scolytidae): what matters if they drop down during the fruiting phase?

Falling of berries bored by Hypothenemus hampei (Ferrari) may be the major loosing factor during the fruiting period. However, only those bored berries which remain in the soil surface before a new yielding period have been recognized as responsible for the damage level Ho achieved by new developing berries. In this paper, we investigated in the plants and in the soil surface, the presence of Coffea canephora cv. Conilon berries bored by H. hampei during the yielding period in Ouro Preto d'Oeste, Rond?nia, Brazil. We took samples, weekly, from December 2000 to June 2001. The data were submitted to the Surviving Regression Analysis, based on a censored Weibull model. During the yielding period, berries fall down continuously and, in average, the proportion of H. hampei bored berries was 4 to 20 times higher in the soil (P < 2,3 x 10-18, n = 62,747) than in the plants. Thus, we argue that adding the "soil environment" to the integrated management strategies could point to new technologies for the control of this insect.     

Is there meaningful plant resistance to diaprepes abbreviatus (Coleoptera: Curculionidae) in citrus rootstock germplasm?

Host plant resistance to the Diaprepes root weevil, Diaprepes abbreviatus (L.) was assessed for seedlings of 54 Poncirus trifoliata (L.) Raf. selections and two families of progeny from crosses between Citrus and P. trifoliata. Weight gain was consistently lower when larvae were reared in pots containing the progeny of Citrus reticulata Blanco 'Sunki' x P. trifoliata 'Flying Dragon' compared with larvae reared on progeny of 'Pearl' (C. reticulata x C. paradisi Macf.) x 'Flying Dragon'. This is the first evidence of genetic control of resistance to the Diaprepes root weevil within sexually compatible citrus rootstock germplasm. There was a significant positive correlation between percentage root loss and larval weight gain within the resistant progeny, indicating a possible antixenotic effect. Two varieties of P. trifoliata were identified as more resistant than 'Flying Dragon' based on larval weight gain.     

Occurrence of species of the genus Pityophthorus Eichhoff (Coleoptera,Curculionidae, Scolytinae) in?the?province of Quebec,Canada

Twig beetles in the genus Pityophthorus Eichhoff, 1864 include more than 300 species worldwide, with maximum diversity in tropical and subtropical regions. To date, approximately 50 species of Pityophthorus have been recorded in Canada, and these species are associated mainly with coniferous trees. Since 1981, no comprehensive study on this difficult taxonomic group has been conducted in Quebec, Canada, most likely due to their limited significance as forest pests. Based on data gathered from five years of field sampling in conifer seed orchards and compiled from various entomological collections, the distribution of Pityophthorus species in Quebec is presented. Approximately 291 new localities were recorded for the Pityophthorus species. Five species-group taxa, namely Pityophthorus puberulus (LeConte, 1868), Pityophthorus pulchellus pulchellus Eichhoff, 1869, Pityophthorus pulicarius (Zimmermann, 1868), Pityophthorus nitidus Swaine, 1917,and Pityophthorus cariniceps LeConte&Horn, 1876 were the most widespread. In contrast, Pityophthorus consimilis LeConte, 1878, Pityophthorus intextus Swaine, 1917, Pityophthorus dentifrons Blackman, 1922, Pityophthorus ramiperda Swaine, 1917, and Pityophthorus concavus Blackman, 1928 display a notably limited distribution. In addition, the first distribution records of Pityophthorus intextus and Pityophthorus biovalis Blackman, 1922 are furnished, and the subspecies Pityophthorus murrayanae murrayanae Blackman, 1922is reported from Quebec for the second time. Moreover, distribution maps are provided for all Pityophthorus species recorded in the province of Quebec.     

Should the flower bud weevil Anthonomus santacruzi (Coleoptera: Curculionidae) be considered for release against the invasive tree Solanum mauritianum (Solanaceae) in New Zealand?

The invasive tree Solanum mauritianum Scop. has been targeted for biological control in South Africa and New Zealand, by deploying insect agents that could constrain its excessive reproductive output. The flower-feeding weevil Anthonomus santacruzi (Curculionidae) was approved for release in South Africa in 2007 but following the loss of the original culture in quarantine, new stocks were introduced from Argentina in 2008–2009. This study was initiated to confirm that the host range of the new culture was the same as that of the previous one, but also to assess the risks associated with the weevil's release in New Zealand. Different testing procedures, including no-choice tests and multi-choice tests in different arenas, produced inconsistent and ambiguous results. During no-choice tests, oviposition and larval development to adulthood occurred on three non-target species including two native South African and one native New Zealand Solanum species. However, subsequent multi-choice tests and a risk assessment suggested that the risks of anything more than collateral damage to non-target Solanum species are low. Overall, these data do not deviate substantially from the results of the original quarantine tests which facilitated the release of A. santacruzi in South Africa in 2009. Although we argue that none of the New Zealand native and cultivated species are at risk, stronger evidence from open-field trials and chemical ecology studies may be required to convince the regulatory authorities that A. santacruzi is suitable for release in New Zealand.     

Could research in the native range, and non-target host range in Australia, have helped predict host range of the parasitoid Microctonus aethiopoides Loan (Hymenoptera: Braconidae), a biological control agent introduced for Sitona discoideus Gyllenhal (Coleoptera: Curculionidae) in New Zealand?

It is generally accepted that knowledge of the natural and novel host range of proposed biological control agents can help to inform predictions of potential host range in new areas of introduction. To test this hypothesis, this paper describes a retrospective study conducted to contrast and compare the natural host range of Microctonus aethiopoides Loan (Hymenoptera: Braconidae) with its novel host range found in Australia and New Zealand, where it has been introduced to control the adult stage of the weevil Sitona discoideus Gyllenhal (Coleoptera: Curculionidae), a pest of lucerne. Surveys carried out in and near lucerne crops in Morocco and Australia each resulted in collections of over 3,000 weevils, of which respectively 84?% and 93?% were S. discoideus. The host ranges determined from these surveys for each M. aethiopoides population were then compared with information already available for field host range in New Zealand. In Morocco, species in the genera Sitona and Charagmus (Curculionidae: Entiminae: Sitonini) and Hypera (Curculionidae: Hyperinae: Hyperini) were found to be parasitised by M. aethiopoides. In Australia, an earlier record of non-target parasitism of ‘Prosayleus’ sp. 2 (Curculionidae: Entiminae: Leptopiini) is still the only known instance of non-target parasitism by M. aethiopoides. The known non-target field host range in New Zealand is much greater, comprising 19 native and introduced weevil species mainly in the subfamily Entiminae (tribe Leptopiini) but also in Curculioninae, Cyclominae and Lixinae. This is discussed in the context of predictions that could have been made at the time of introduction 30?years ago had the Moroccan and Australian data, modern molecular technologies and current understanding of weevil classification been available. The absence of Leptopiini in Morocco and the record of a native Australian leptopiine host could have indicated that native weevils in this tribe in New Zealand might be at risk of attack by M. aethiopoides.     

Factors influencing the geographical distribution of Dendroctonus rhizophagus (Coleoptera: Curculionidae: Scolytinae) in the Sierra Madre Occidental, México

The bark beetle, Dendroctonus rhizophagus Thomas & Bright, is endemic to the Sierra Madre Occidental (SMOC) in México. This bark beetle is a major pest of the seedlings and young saplings of several pine species that are of prime importance to the nation's forest industry. Despite the significance of this bark beetle as a pest, its biology, ecology, and distribution are poorly known. Three predictive modeling approaches were used as a first approximation to identify bioclimatic variables related to the presence of D. rhizophagus in the SMOC and to obtain maps of its potential distribution within the SMOC, which is a morphotectonic province. Our results suggest that the bark beetle could have an almost continuous distribution throughout the major mountain ranges of the SMOC. This beetle has a relatively narrow ecological niche with respect to some temperature and precipitation variables and inhabits areas with climatic conditions that are unique from those usually prevalent in the SMOC. However, the bark beetle has a broad ecological niche with respect to the number of hosts that it attacks. At the macro-scale level, the D. rhizophagus distribution occurs within the wider distribution of its main hosts. The limit of the geographical distribution of this bark beetle coincides with the maximum temperature isotherms. Our results imply a preference for temperate habitats, which leads to the hypothesis that even minor changes in climate may have significant effects on its distribution and abundance.     

Is the Ca:Al ratio superior to pH,Ca or Al concentrations of soils in accounting for the distribution of plants in deciduous forest?

The distributions of vascular plants in south Swedish deciduous forests were related to exchangeable (exc) and soil solution concentrations of H⁺ (pH), Ca, Al and the Ca:Al ratios within these fractions. Topsoils (0–5 cm) of 172 sites with a pH_KCl of 3.2–3.9 (corresponding to 3.7–4.4 in soil solution) were used. In the soil solution both total Al_t and quickly reacting Al_r were determined. Exchangeable concentrations were generally well related to plant distributions, the highest correlation coefficients usually being given by pH_KCl>Ca_exc>Al_exc.>(Ca:Al)_exc. The (Ca:Al)_exc ratio was clearly inferior. Out of the soil solution variables studied, Ca concentration, followed by pH, was best correlated with plant distributions, Al_t, Al_r, and the Ca:Al ratios having similar and lower coefficients. It is concluded that the use of Ca:Al ratios as a general measure of Al toxicity in controlling plant distributions is rather problematic. It seems difficult to apply evidence for Ca-Al interactions from solution culture experiments to field conditions when measured as exchangeable or soil solution concentrations of the soil.     

Evaluation of the Boll Weevil Anthonomus grandis Boheman (Coleoptera: Curculionidae) Suppression Program in the State of Goiás, Brazil

The boll weevil Anthonomus grandis Boheman (Coleoptera: Curculionidae) is the most important cotton pest in Brazil. A large-scale field-testing of a Boll Weevil Suppression Program (BWSP) was implemented to assess its technical and operational feasibility for boll weevil suppression in the state of Goiás, Brazil. The pilot plan focused on 3,608 ha of cotton during the 2006/2007 and 6,011 ha in the 2007/2008 growing seasons; the areas were divided into four inner zones with an outer buffer zone. We analyzed data on boll weevil captures using pheromone traps installed in the BWSP fields, on the detection of the first insect and the first damaged floral bud, greatest damage, and number of insecticide applications. The nonparametric Mann–Whitney U test was used to evaluate the differences between presuppression and suppression years. Fourteen pheromone-baited trapping evaluations were used to compare the weevil populations from 2006/2007 and 2007/2008 growing seasons. The BWSP regime reduced in-season boll weevil captures from 15- to 500-fold compared to presuppression levels in the preceding year. The low capture rates were related to delays in infestation and damage by weevils. The smaller population size measured by trapping and field monitoring reduced the number of required insecticide treatments. The BWSP strategy was efficient in suppressing populations of this pest and is a viable program for cotton production in subtropical and tropical regions, with long-term economic and environmental benefits.     

Potential of Lariophagus distinguendus (Förster) (Hymenoptera: Pteromalidae) to suppress the maize weevil Sitophilus zeamais Motschulsky (Coleoptera: Curculionidae) in bagged and bulk stored maize

Grains are often stored in jute bags in developing countries, especially in Africa, as well as in small quantities in bulk. Parasitoids suitable for biological control of stored-product pests should be able to find their hosts in bulk grain or in jute bags over a certain distance in a warehouse containing stacks of bagged grain. The potential of using Lariophagus distinguendus for the biological control of Sitophilus zeamais was assessed in maize stored in jute bags and bulk grain. The ability of the parasitoid to penetrate the jute cloth and the grain mass and parasitize its host was studied under controlled conditions of 25 ± 1 °C and 65 ± 5% RH. Experiments were carried out in small 5-kg jute bags containing 28 d old S. zeamais larvae within infested maize kernels, and in cylinders filled with maize grains and containing caged hosts at different depths. L. distinguendus parasitized S. zeamais in the jute bags and in the storage cylinders at various depths. In the jute bag experiment, out of the 60 L. distinguendus adults released, a mean ± SD of 7.03 ± 1.78% and 6.34 ± 1.01% of the 40 females and of the 20 males released, respectively, entered the jute bags. Significantly, no differences were found between the female and male L. distinguendus that entered the bags. Mean reduction of S. zeamais in the jute bags by parasitoids was 81%. The parasitic wasps also significantly reduced the emergence of S. zeamais in bulk maize. At depths of 20–45 cm from the grain surface, mean reduction of S. zeamais was 74%, while from 95 to 100 cm, mean reduction was 34%. When results from depths lower than 50 cm were pooled and compared with pooled data from depths higher than 90 cm, there was a significant reduction in parasitism at depths of more than 90 cm. For depths below 50 cm a mean of 5.3 L. distinguendus adult offspring per cage emerged compared with a mean of 2.6 at depths of more than 90 cm. These results support the approach to utilize L. distinguendus as a component in the integrated control of S. zeamais in bagged or bulk stored maize.     

Ant associations in the Neotropical shrub Turnera subulata (Turneraceae): Costs or benefits to the host plant?

The results of ecological interactions depend on the costs and benefits involved in different ecological contexts. Turnera subulata is a shrubby plant with extrafloral nectaries that are associated with ants. Here, we test the hypotheses that the association between T. subulata and ants results in: (i) positive effects on host plant growth and reproduction; (ii) plant herbivory reduction and (iii) inhibition of the host plant visitation by beneficial organisms. Thirty experimental plots were established in northeastern Brazil, either in association with ants or without ants (N = 15 plots/treatment), with four plants each (total 120 plants). Vegetative growth (plant height and number of leaves), reproductive investment (flowers and fruits), herbivory rates and numbers of beneficial visitors were quantified during all phenological stages of the host plant. Data were analysed using generalized linear mixed models. At the host plant maturation stage, we found a trade‐off between growth and reproduction. Plants with ants had lower mean height; however, they invested more in reproduction (a higher number of flowers and fruits) compared to plants without ants. During the flowering stage, the abundance of sucking herbivores was higher in plots without ants but chewing herbivore abundance increased in the maturation stage in plots with ants. The cumulative proportion of leaves with herbivore damage did not differ between treatments, and the presence of ants reduced the number of beneficial visitors (e.g. pollinators and natural enemies) to the host plants. Our results show that association with ants results in some costs for the host plant, however, these costs appear to be offset by the defensive role of ants, which favours plant reproductive investment. In general, our results help to elucidate mechanisms involved in trophic interactions within the complex network of interactions involving ants and plants.     

Testing the ‘island rule’ for a tenebrionid beetle (Coleoptera,Tenebrionidae)

Insular populations and their closest mainland counterparts commonly display body size differences that are considered to fit the island rule, a theoretical framework to explain both dwarfism and gigantism in isolated animal populations. The island rule is used to explain the pattern of change of body size at the inter-specific level. But the model implicitly makes also a prediction for the body size of isolated populations of a single species. It suggests that, for a hypothetical species covering a wide range of island sizes, there exists a specific island size where this species reaches the largest body size. Body size would be small (in relative terms) in the smallest islets of the species range. It would increase with island size, and reach a maximum at some specific island size. However, additional increases from such a specific island size would instead promote body size reduction, and small (in relative terms) body sizes would be found again on the largest islands. The biogeographical patterns predicted by the island rule have been described and analysed for vertebrates only (mainly mammals), but remain largely untested for insects or other invertebrates. I analyse here the pattern of body size variation between seven isolated insular populations of a flightless beetle, Asida planipennis (Coleoptera, Tenebrionidae). This is an endemic species of Mallorca, Menorca and a number of islands and islets in the Balearic archipelago (western Mediterranean). The study covers seven of the 15 known populations (i.e., there are only 15 islands or islets inhabited by the species). The populations studied fit the pattern advanced above and we could, therefore, extrapolate the island rule to a very different kind of organism. However, the small sample size of some of the populations invites some caution at this early stage.     

Exotic Pine Plantations in Victoria, Australia: A Threat to Epigaeic Beetle (Coleoptera) Assemblages?

Ground-dwelling invertebrates were sampled by pitfall traps over a 14 week period in parent eucalypt forest and three stages of exotic Pinus radiata plantations established after forest clearance in central Victoria. The four treatments each yielded numerous beetle morphospecies, and the assemblages corresponded only partially with the understorey vegetation. More than 200 beetle morphospecies were captured during this short survey, with 30 found in all four treatments; few morphospecies were abundant (only five with >100 individuals in a total of 3382 beetles). Each treatment had unique morphospecies, but all were rich, with the lowest diversity being 91 morphospecies (young pines). These data confirm that beetle diversity can remain substantial in exotic softwood plantations, but considerable care is needed to interpret this apparent diversity in relation to forest management and the effect of replacement of native forests by exotic taxa.     

The effects of host plant on the coccinellid functional response: Is the conifer specialist Aphidecta obliterata (L.) (Coleoptera: Coccinellidae) better adapted to spruce than the generalist Adalia bipunctata (L.) (Coleoptera: Coccinellidae)?

Female Aphidecta obliterata consumed an average of 26.6 ± 5.8 Elatobium abietinum and males consumed an average of 19.9 ± 3.2 Elatobium abietinum, but there was no significant difference in the number consumed between the sexes. In Petri dish trials, the larval stages of A. obliterata and all stages of Adalia bipunctata appeared to exhibit a Type II response to prey density, although A. obliterata adults showed a more linear response to prey density. There was no significant difference between the functional responses of the 3rd instars of the two coccinellid species, but there was a significant difference between the responses shown by the 1st instars, with A. obliterata larvae consuming more than those of A. bipunctata, especially at low densities, suggesting that the two species respond differently to an increase in prey density.At low prey densities, adults and 4th instars of both species exhibited a similar response to an increase in prey density but at higher densities the 4th instars and adult stages of A. bipunctata showed higher attack rates when compared with the same stages of A. obliterata.Adult and 4th instar A. obliterata exhibited Type II functional responses on spruce sections. The 4th instar A. obliterata larva appeared to be a more effective predator than the adult of the species, and was more effective when compared with adult A. bipunctata at lower prey densities but A. bipunctata adults appeared to be a more effective predator at higher prey densities.The host plant affected the rate of consumption by adult A. obliterata as adults on Sitka spruce sections consumed significantly higher numbers of aphids than their counterparts on Norway spruce. This was most noticeable at densities above 16 aphids.The distributions of the two coccinellid species in the olfactometer were significantly affected by the presence of host plant material. Aphidecta obliterata adults were found in significantly higher numbers in the Sitka spruce chambers than the control chambers (those without plant material). Adalia bipunctata adults were found in significantly lower numbers in the Norway spruce chamber than the control chamber.Although A. bipunctata has a higher level of voracity than A. obliterata, the latter is more adapted to the spruce environment and the boom and bust population dynamics of E. abietinum.     

Relationship between land uses and diversity of dung beetles (Coleoptera: Scarabaeinae) in the southern Atlantic forest of Argentina: which are the key factors?

The loss of natural habitats is one of the main drivers of biodiversity decline. Anthropogenic land uses preserving biotic and abiotic conditions of the native ecosystem are more suitable to preserve the native biodiversity. In this study, we explored changes in species richness and composition in different land uses of the southern Atlantic forest, considering three independent factors: (1) canopy (presence–absence), (2) type of vegetation (native–exotic) and (3) livestock (presence–absence). We expected a gradient of response in the richness and composition of the native forest dung beetle community, from land uses preserving canopy and native vegetation to open land uses with exotic vegetation. Dung beetles were sampled in protected native forests and four land uses, using two potential food resources: human dung and carrion. The species richness and composition of each habitat, as well as differences in composition and the influence of factors over diversity, were then analyzed. As expected, our results showed that land uses preserving canopy and native vegetation maintain the dung beetle diversity of the native forest. Moreover, while the three factors analyzed influenced dung beetle diversity, canopy cover was the main driver of dung beetle diversity loss. The main conclusion of this study is that the conservation of canopy (either native or exotic) is determinant to preserve highly diverse dung beetle communities and subsequently, the ecological functions performed by this taxon. However, the ecophysiological mechanism behind the response of dung beetles to habitat disturbance is poorly understood.     

Ground Beetles (Coleoptera, Carabidae) in Forest Fragments of the Manawatu, New Zealand: Collapsed Assemblages?

Botanically diverse and well-maintained, protected forest fragments in the Manawatu area of the North Island of New Zealand contained very species-poor carabid assemblages. In a nearby large forest tract, the potential source area, nine species were caught in pitfall traps, while the largest forest remnant had two species, and a well-managed suburban forest patch had three species but only one with a potentially reproducing population. Lack of grazing and high botanical diversity was insufficient to maintain the potential carabid assemblage in these fragments. Predation risk and a low dispersal power in endemic New Zealand ground beetles, combined with fragment size and degree of isolation could contribute to this collapse. Active management of ground-active invertebrate species seems necessary to protect them in isolated forest fragments in New Zealand.     

Effects of larval host plants on over-wintering preparedness and survival of the cotton bollworm, Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae)

Laboratory colonies of cotton bollworm larvae, Helicoverpa armigera, kept at 20 degrees C under a photoperiod of L:D=10:14 were fed on five host plants (cotton, corn, kidney bean, tobacco and tomato) and an artificial diet (control) to determine the effects of larval host quality on survival and pupal over-wintering preparedness. A separate experiment showed that diapausing pupae weighed more and contained greater nutrient stores than did non-diapausing pupae. Diapausing pupae reared on different host plants showed significant differences in terms of over-wintering reserve storage, and degree of cold-hardiness (extent of low-molecular-weight substances and SCPs), and survivorship. The more nutrients the host plant had, the more the pupae weighed and the higher the levels of total lipids and glycogen. Body water content was also significantly affected by larval food quality. The mean pupal super-cooling capacities varied significantly from -16.7 to -18.9 degrees C according to host plants the larvae feed on, and these significantly related to water content, pupal weight, lipid and glycogen content, and the levels of glycerol. Levels of trehalose, glycerol, and inositol, which were mainly low-molecular-weight substances, showed no significant differences among different host plants, except for trehalose. Pupal mortality varied from 39.7% on corn to 3.3% on the artificial diet, which was significantly related to pupal weight, total lipid content, trehalose levels, and super-cooling points. These results suggest that larval food quality can affect survival and influence the over-wintering preparedness of the cotton bollworm.     

Movement activity and habitat use of Carabus ullrichii (Coleoptera: Carabidae): The forest edge as a mating site?

Some carabid species are not restricted to a single habitat only, but use various types of habitats. In these species, relatively little is known about the utilization of occupied habitats and factors affecting their movement within these habitats. In this study, we focus on the movement activity of ubiquitous Carabus ullrichii during its reproductive period at the border of two types of habitats, a meadow and a forest. We tracked 21 adult individuals using radio telemetry and recorded in total 1,687 position fixes. Movement activity was associated with the type of habitat and specific environmental conditions such as time of the day and air temperature. Both sexes activated preferably at dusk and during the night, although males were most active at temperatures around 15°C, while females showed no preference for temperature. Males were able to walk as fast as females, but they were more associated with forest edge. We assume that the inner edge of the forest could be used as a mating site and after mating males stay there and wait for new females with which to mate, while fertilized females disperse into the surroundings. They moved further into the closed forest where they were likely looking for oviposition sites and food resources to support reproduction. Exclusively females were recorded to visit the meadow at a greater distance from the forest edge and their movements there were almost always direct.