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International audience; Key message:Melolontha hippocastani is a major pest in European mixed and broadleaf forests. Investigating its oviposition behavior, we observed that a dense shrub layer reduces the density of egg clusters and eggs in the soil. Conversely, canopy openness and a large proportion of oak appear as favoring conditions.Context:Melolontha hippocastani is a major pest in European mixed and broadleaf forests. In north-eastern France, an epidemic phase has been observed since 2007, characterized by a high mortality rate of seedlings and young trees, and by massive swarming flights every 4 years.Aims:We investigated the oviposition behavior of M. hippocastani in the northern Vosges Mountains.Methods:We set up study plots in the infected area after adults had emerged and the females had laid their eggs. We excavated pits and counted the eggs and egg clusters they contained. We also carried out dendrometric surveys.Results:A dense shrub layer had a negative effect on the density of egg clusters and the number of eggs in the soil, while canopy openness and the proportion of oak basal area had positive effects.Conclusion:We hypothesized that a dense shrub layer could create a barrier for females. On the other hand, an open canopy may improve conditions for the larvae in the soil, just as a high proportion of oak trees in the surrounding area may provide a good food source for both larvae and adults. We suggest several research orientations and propose guidelines for forest management in view of our results.

A plant's offspring may escape unfavourable local conditions through seed dispersal. Whether plants use this strategy to escape insect herbivores is not well understood. Here, we explore how different dandelion ( Taraxacum officinale agg.) populations, including diploid outcrossers and triploid apomicts, modify seed dispersal in response to root herbivore attack by their main root-feeding natural enemy, the larvae of the common cockchafer Melolontha melolontha. In a manipulative field experiment, root herbivore attack increased seed dispersal potential through a reduction in seed weight in populations that evolved under high root herbivore pressure, but not in populations that evolved under low pressure. This increase in dispersal potential was independent of plant cytotype, but associated with a reduction in germination rate, suggesting that adapted dandelions trade dispersal for establishment upon attack by root herbivores. Analysis of vegetative growth parameters suggested that the increased dispersal capacity was not the result of stress flowering. In summary, these results suggest that root herbivory selects for an induced increase in dispersal ability in response to herbivore attack. Induced seed dispersal may be a strategy that allows adapted plants to escape from herbivores.

Root-feeding Melolonthinae larvae are a forest pest species in Europe that can exert serious damage. In Poland, they are classified as the most dangerous pest on land dedicated to afforestation and the most serious threat to natural regeneration in the stands. This study was performed in three forest districts in east Poland (Lubart&oacute, w, Marcule, and Wyszk&oacute, w forest districts) in mixed conifer forests, where the presence of Melolontha spp. grubs was evaluated in autumn and spring of 2012 to 2017, respectively. In spring 2012, 2014, and 2016, consecutively &lsquo, small sawdust pits&rsquo, in rows between seedlings were prepared, and in adjacent inter-rows similar control pits without sawdust were marked. In spring and autumn of the following year, sawdust and soil from both types of pits were sieved and Melolonthinae larvae were counted and compared. More grubs were found in sawdust pits in spring than in autumn. In Marcule Forest District (FD) (2014), more grubs were found in inter-rows than in rows with seedlings, when compared to grubs detected using the traditional method of &ldquo, autumn large pits assessment&rdquo, recommended by Polish forest rules. The Melolonthinae population size and location of grubs were related to the weather conditions in the evaluated periods, as well. We conclude that to properly assess the cockchafer threat, it is necessary to perform spring assessment and to search in inter-rows. This could be recommended for decisions on control.

The role of soil characteristics for cue-directed behaviour of rhizophagous insects remains largely unexplored to date. Here, we studied behavioural responses of polyphagous cockchafer larvae (Melolontha melolontha; Scarabaeidae) to roots of one of its preferred host plants, dandelion (Taraxacum sectio ruderalia; Asteraceae). Plants were grown in substrates with different adsorptive capacities, i.e. in vermiculite or sand. A behavioural assay was developed which allowed both monitoring the release of attractive CO2 from roots and observation of larval behaviour at the same time. In sand, larvae got closer to the roots than in vermiculite where they eventually stopped orienting towards the roots: However, their total locomotory activity and the number of turning events/stationary points were higher in vermiculite. Larval behaviour was not correlated with CO2 concentrations in both vermiculite and sand. On average, larvae kept a greater distance to vermiculite-grown roots. However, a feeding bioassay revealed that the larvae consumed more of vermiculite-grown roots than of sand-grown ones. This result showed that the weaker orientation of larvae towards vermiculite-grown roots was not due to the lower palatability of these roots. Vermiculite might adsorb foraging-relevant cues of dandelion roots, alter composition of root exudates, and/or physically impair oriented movements of soil-dwelling insects. Our study shows that the type of substrate affects responses of rhizophagous larvae to host roots at multiple levels independently of root-derived CO2 gradients.

The paper presents a review of information on control measures used to prevent damages due to cockchafer Melolontha spp. grubs in European countries including Poland. There are described the methods used at times when mechanical and chemical treatments were applied as well as those under advanced research. In the past, cockchafer grubs were manually removed from plowed soils. Later on, chemical pest control commenced in plant protection practice, and a range of insecticides were either spotted directly onto plants or applied into planting rows, otherwise an entire planting area was treated. In that case, powder or granular insecticide formulations were mixed with upper soil layers, but liquid insecticides were poured into the soil around seedlings. The active substance of initial plant protection products used in Poland to control cockchafer grubs was lindane (organochlorine neurotoxin), which showed pretty high efficacy. Nevertheless, organochlorine products must have been withdrawn from the market and less damaging to the environment pesticides (organophosphates and carbamates) were recommended for use in forest protection against cockchafer grubs. As a result of progressive restrictions concerning application of chemicals into forest environment, alternate solutions have been sought, e.g. biological methods of cockchafer grub control have been tested. Up to date studies showed insecticidal properties of bacteria, fungi and nematodes. However, even though the knowledge and awareness of practitioners have raised with time, the problem of cockchafer grub populations damaging forest crops has not yet been solved and seems to be more and more difficult to overcome.

Background In this paper, a regression model for predicting the spatial distribution of forest cockchafer larvae in the Hessian Ried region (Germany) is presented. The forest cockchafer, a native biotic pest, is a major cause of damage in forests in this region particularly during the regeneration phase. The model developed in this study is based on a systematic sample inventory of forest cockchafer larvae by excavation across the Hessian Ried. These forest cockchafer larvae data were characterized by excess zeros and overdispersion. Methods Using specific generalized additive regression models, different discrete distributions, including the Poisson, negative binomial and zero-inflated Poisson distributions, were compared. The methodology employed allowed the simultaneous estimation of non-linear model effects of causal covariates and, to account for spatial autocorrelation, of a 2-dimensional spatial trend function. In the validation of the models, both the Akaike information criterion (AIC) and more detailed graphical procedures based on randomized quantile residuals were used. Results The negative binomial distribution was superior to the Poisson and the zero-inflated Poisson distributions, providing a near perfect fit to the data, which was proven in an extensive validation process. The causal predictors found to affect the density of larvae significantly were distance to water table and percentage of pure clay layer in the soil to a depth of 1 m. Model predictions showed that larva density increased with an increase in distance to the water table up to almost 4 m, after which it remained constant, and with a reduction in the percentage of pure clay layer. However this latter correlation was weak and requires further investigation. The 2-dimensional trend function indicated a strong spatial effect, and thus explained by far the highest proportion of variation in larva density. Conclusions As such the model can be used to support forest practitioners in their decision making for regeneration and forest protection planning in the Hessian Ried. However, the application of the model for predicting future spatial patterns of the larva density is still somewhat limited because the causal effects are comparatively weak.

The aim of the study was to evaluate the possibility of using botanic antifeedants to reduce the damage caused by Melolontha spp. grubs. To achieve the objective, the experiments were established in semi-field conditions to estimate the antifeedant activity of rutin, quercetin (flavonoids from buckwheat Fagopyrum esculentum) and an extract from black alder Alnus glutinosa leaves against Melolontha melolontha grubs. The grubs were placed individually in the pots with a soil in which 2 year old Pinus sylvestris trees were planted. The pots were put in garden pavilions placed in the open area. Then the soil in the pots were watered with the emulsions of rutin, quercetin, an extract from A. glutinosa leaves, and with pure water-comparative variant. After 4 months, the weight and mortality of grubs were compared, as well as the weight of tree roots in all pots. There was no effect of the antifeedants on the development and extent of damage caused by M. melolontha grubs. The results do not indicate the use of botanic antifeedants in the protection of forests against the cockchafer grubs

In many insect species olfaction is a key sensory modality. However, examination of the chemical ecology of insects has focussed up to now on insects living above ground. Evidence for behavioral responses to chemical cues in the soil other than CO2 is scarce and the role played by olfaction in the process of finding host roots below ground is not yet understood. The question of whether soil-dwelling beetle larvae can smell their host plant roots has been under debate, but proof is as yet lacking that olfactory perception of volatile compounds released by damaged host plants, as is known for insects living above ground, occurs. Here we show that soil-dwelling larvae of Melolontha hippocastani are well equipped for olfactory perception and respond electrophysiologically and behaviorally to volatiles released by damaged host-plant roots. An olfactory apparatus consisting of pore plates at the antennae and about 70 glomeruli as primary olfactory processing units indicates a highly developed olfactory system. Damage induced host plant volatiles released by oak roots such as eucalyptol and anisol are detected by larval antennae down to 5 ppbv in soil air and elicit directed movement of the larvae in natural soil towards the odor source. Our results demonstrate that plant-root volatiles are likely to be perceived by the larval olfactory system and to guide soil-dwelling white grubs through the dark below ground to their host plants. Thus, to find below-ground host plants cockchafer larvae employ mechanisms that are similar to those employed by the adult beetles flying above ground, despite strikingly different physicochemical conditions in the soil. Open-Access-Publikationsfonds 2012 peerReviewed

Straipsnyje keliama mintis, kad lie. bužỹs ‘vabzdys, vabalas, utėlė’ ir la. buzis ‘utėlė’ (abu iš rytų bl. *bužias m.), taip pat la. būza ‘utėlė’, yra buvę vediniai iš ide. žodžio, reiškusio ‘ožka’ (ide. *bhugos m. ‘ožys’, *bhugā f. ‘ožka’), plg. arm. buc ‘ėriukas; ožiukas’, Av. būza- m. ‘ožys’, n. persų buz ‘ožys, ožka’ ir t. t. Tokia pati semantinė raida paliudyta ir kitose ide. kalbose, plg. arm. bcic ‘utėlė’ : buc ‘ėriukas; ožiukas’; jazgulamų vazák ‘smulkus juodas šokinėjantis vabzdys’ : vaz f. ‘ožys, ožka’; šugnų vazič f. ‘žiogas’ : vaz m. ‘ožys’, vāz f. ‘ožka’. Suponuojami pakitimai gali būti rekonstruojami taip: ‘ožys, ožka’ (ankst. ide.) >‘šokinėjantis ožiukas’ (ide.) >‘šokinėjantis vabzdys’ (vėlyvas ide. ar poide. procesas, paliudytas iranėnų, armėnų, rytų baltų kalbose) >‘utėlė’ (arm., rytų bl.) >‘bet koks vabzdys’ (tik lie.). In his paper the author suggests that Lith. bužỹs ‘insect, cockchafer, beetle, louse’ and Latvian buzis ‘louse’ (both from East Baltic *bužias m.), as well as Latv. būza ‘louse’, were originally derivatives from the Indo-European word for ‘she-goat’ (IE. *bhugos m. ‘buck, he-goat’, *bhugā f. ‘she-goat’), cf. Armenian buc ‘lamb; young goat, kid’, Avestan būza- m. ‘he-goat’, New Persian buz ‘goat’ and so on. The same semantic development is also attested in other Indo-European languages, cf. Arm. bcic ‘louse’ : Arm. buc ‘lamb; young goat, kid’; Yazghulami vazák ‘a tiny black insect, which moves about by jumping’ : Yazgh. vaz f. ‘goat’; Shughni vazič f. ‘grasshopper’ : Sh. vaz m. ‘he-goat’, vāz f. ‘she-goat’. The suggested transformations may be reconstructed in the following way: ‘goat’ (early IE) >‘jumping kid’ (IE) >‘jumping insect’ (a late Indo-European or post-Indo-European process, attested in Iranian, Armenian, East Baltic) >‘louse’ (Armenian, East Baltic) >‘any insect’ (only in Lithuanian).

Demirbag, Zihni/0000-0001-5487-1977 WOS: 000246813500006 PubMed: 17575913 A bacterial isolate (Mm2) of Melolontha melolontha was identified and characterized. Based on various morphological, physiological, biochemical and molecular characteristics, it was identified as Bacillus thuringiensis subsp. tenebrionis. This isolate was compared to the reference strains by electron microscopy, SDS-PAGE analysis, plasmid pattern, cry gene content and insecticidal activity. Cells of the isolate harbored flat square inclusions containing a protein component of approximate to 65 kDa. After trypsin digestion of solubilized crystals, SDS-PAGE resolved a unique proteinase-resistant peptide of approximate to 50 kDa. Plasmid pattern showed similar bands to those of the reference strain, PCR analysis showed that the isolate has cry3 gene. Toxicity tests (against 5 coleopteran species) showed 80% insecticidal activity against the larvae of M. melolontha. The isolate Mm2 may be valuable as biological control agent for M melolontha and other coleopteran insects.

The soil-dwelling larvae of several Scarabaeidae species (white grubs), like the cockchafer (Melolontha melolontha) and the garden chafer (Phyllopertha horticola), are serious pests in European cultivated grassland, reducing grass yield and destroying the turf by root-feeding. Nevertheless, the factors responsible for the development of large grub populations and the associated damage risk are poorly understood. The objectives of the study were to survey grub densities in grassland sites with different damage histories and find correlations with environmental and management variables. Data on grub densities were collected at 10 farms in the eastern Austrian Alps in September and October 2011. At each farm, one recently damaged site (high risk) and one site at which grub damage had never been observed by the farmers (undamaged site = low risk; each site: 500 m(2)) were sampled. All sites were dominated by P. horticola (99% of 1,422 collected individuals; maximum density 303 grubs/m(2)), which indicates that grub damage there is mainly caused by that species. Recently damaged sites tended to higher grub densities than undamaged sites. However, 3 out of 10 undamaged sites harbored high grub populations as well. Humus content together with the depth of the A-horizon significantly explained 38% of P. horticola grub density variance, with highest densities in deeper humus-rich soils. The risk of grub damage was positively connected to the humus content and negatively related to the cutting frequency. For the investigated mountainous grassland sites, these results suggest an important role of humus for the development of high grub densities and an effect of management intensity on grub damage.