Among the semi-natural elements in agricultural landscapes, wildflower strips sown at field margins or within fields are potential habitats for the natural enemies of insect pests. As insects are sensitive to a variety of flower traits, we hypothesized that mixtures with high functional diversity attract and support a higher abundance and species richness of aphid flower visiting predators than mixtures with low functional diversity. During a field experiment, repeated over two years (2014 and 2015) in Gembloux (Belgium), aphid predators (i.e., lacewings, ladybeetles and hoverflies) were pan-trapped in five sown flower mixtures (including a control mixture, with three replicates of each mixture) of low to high functional diversity based on seven traits (i.e., flower colour, ultra-violet reflectance and pattern, start and duration of flowering, height and flower class, primarily based on corolla morphology). In both years, the species of flowering plants in the sown mixtures (i.e., sown and spontaneous flowers) were listed, and the realized functional diversity in each plot calculated. Over the two years, a high functional diversity was not associated with high abundance and richness of aphid predators. Moreover, ladybeetles, which made up the majority of the predators trapped, were more abundant in mixtures with very low or intermediate functional diversity at sowing, especially in 2014. We hypothesize that certain flowers, which were abundant in certain mixtures (and not in those exhibiting the highest functional diversity), attracted predators and were sufficiently abundant to support them. Our results present novel information that could be used for developing flower mixtures that provide effective ecosystem services, such as pest control., Séverin Hatt, Roel Uyttenbroeck, Thomas Lopes, Pierre Mouchon, Julian Chen, Julien Piqueray, Arnaud Monty, Frédéric Francis., and Obsahuje bibliografii
An experiment was conducted to compare the predation efficiency of the coccinellids Harmonia axyridis and Coleomegilla maculata on potato plants, Solanum tuberosum, and on a wild aphid-resistant species, Solanum tarijense. Harmonia axyridis females reduced aphid populations more than C. maculata females. Aphid predation by the predators was reduced on S. tarijense compared to S. tuberosum. Coleomegilla maculata spent less time on S. tarijense than on S. tuberosum. Harmonia axyridis spent the same amount of time on both plant species. The plant species did not affect IGP between larvae. Compared to S. tuberosum, the resistant plant offers M. persicae an enemy-free space against both coccinellid predators., Bruno Fréchette ... [et al.]., and Obsahuje seznam literatury
The factors that affect the local distribution of the invasive Harmonia axyridis are not yet completely resolved. Hypotheses predicting positive and independent effects of prey abundance and degree of urbanization on the adult abundance of this species in Central Europe were tested. Populations of H. axyridis were sampled in a period when it was most abundant, by sweeping lime trees (Tilia spp.) at 28 sites along a 20 km transect across urban (western Prague) and surrounding rural areas. The sites differed in aphid abundance (number of Eucallipterus tiliae per 100 sweeps) and degree of urbanization (percentage of the surrounding area within a 500 m radius covered by impervious human constructions). Multiple linear regression analysis of log-transformed data revealed that abundance of H. axyridis (number of adults per 100 sweeps) increased significantly with both aphid abundance (P = 0.015) and urbanization (P = 0.045). The positive relationship between degree of urbanization and abundance of H. axyridis was thus not a side effect of variation in aphid abundance, which was also greater in urban than rural areas. The effect of urbanization might constrict the habitat available to H. axyridis and force this species to aggregate in urban green "refugia". These results point to a plurality of factors that determine coccinellid abundance at natural sites.
For biological control it is necessary to store mass-reared biological control agents when the demand is low. The objective of this study is to increase their shelf life without significantly reducing their fitness. The ladybird Hippodamia variegata is a widespread and voracious aphidophagous predator, with an important role in decreasing the abundance of pest aphids in many parts of the world. We investigated the effect of storage at three temperatures: constant 1°C, constant 6°C, and an alternating thermal regime of 12°C/0°C (the higher temperature for 12 h and the lower one for another 12 h). They were exposed to each of the temperature regimes for either 15, 25, 35, 45 or 60 days. We recorded survival, pre-oviposition period, fecundity and voracity of adult H. variegata following storage. The survival of adult beetles significantly declined with increasing storage duration at all three temperatures. Storage at 6°C up to 35 days and at 12°C/0°C up to 45 days had no significant effects on the fecundity of the ladybirds, but storage for longer significantly decreased fecundity. Beetles stored at 1°C for any of the durations had significantly lower fecundities. Prolonged cold storage caused an increase in the pre-oviposition period at all storage temperatures. Generally, 6°C and 12°C/0°C are the best temperatures for storing the ladybirds as they had the least negative effect on their fitness. The results of this research can help in improving the quality of H. variegata stored for use as biological control agents in the following season.
We investigated the predatory potential and food preference of different life stages of Coccinella septempunctata L. for a nutritious aphid (mustard aphid, Lipaphis erysimi) and toxic aphid (cabbage aphid, Brevicoryne brassicae). We provided all the life stages of C. septempunctata with either L. erysimi or B. brassicae and found that the second, third and fourth instar larvae and adult females of this predator consumed daily greater numbers of L. erysimi. However, the first instar larvae and adult males consumed similar numbers of both of these aphids. In choice condition, each larva, adult males and females were each provided separately with a mixed aphid diet in three proportions (i.e. low: high, equal: equal and high: low densities of L. erysimi: B. brassicae). We hypothesized that life stages of C. septempunctata will prefer L. erysimi regardless of its proportions. Laboratory experiments supported this hypothesis only at the adult level in terms of high values of β and C preference indices. However, it rejects this hypothesis at the larval level, as larvae preferred B. brassicae when provided with certain combinations and showed no preference in a few combinations. We infer that mixtures of nutritious and toxic aphids may enable this ladybird to overcome any probable nutritional deficiency and/or reduce the toxicity of a toxic diet, especially for the larvae. Results of the treatment in which a high proportion of B. brassicae were consumed along with fewer L. erysimi indicates that a mixed diet could be better for the development of immature stages of C. septempunctata., Mushtaq A. Guroo, Ahmad Pervez, Kuldeep Srivastava, Rakesh K. Gupta., and Obsahuje bibliografii
Reduced oviposition by ladybirds in the presence of tracks of fourth instar larvae owing to the presence of oviposition deterring pheromones is well established across many genera. However, deterrence, if any, by other life stages has not been well investigated, in particular the effect of conspecific presence. The present study investigates the effects of conspecific presence and semiochemicals of conspecific life stages (eggs, fourth instar larvae, pupae, adult males and females) on oviposition by five ladybird (Coleoptera: Coccinellidae) species, viz. Coccinella septempunctata, Coccinella transversalis, Cheilomenes sexmaculata, Propylea dissecta and Anegleis cardoni. Results reveal that the presence of life stages inhibits oviposition and the inhibition is density-dependent, although the degree of inhibition is species-specific. Surface semiochemicals of eggs and larval and adult tracks also show density-dependent inhibitory effects. Moreover, the semiochemicals in tracks (oviposition deterring pheromones) and egg surface semiochemicals are not similar, indicating semiochemical parsimony. Of all species tested, C. transversalis and C. septempunctata were the most and the least responsive to both conspecific presence and semiochemicals, respectively., Geetanjali Mishra ... [et al.]., and Obsahuje seznam literatury
The effects of imidacloprid on 1-day-old third instars of Harmonia axyridis were assessed by topical treatment and contact with treated glass plates in laboratory bioassays. When 5 µl of imidacloprid solutions were applied topically, the LD50 was 0.085 g/l per insect after 24 h. Contact with imidacloprid-treated plates had little effect on the number of third instars that became adults. Average duration of larval development was not significantly affected by duration of contact and imidacloprid concentrations. There were no significant differences in maximal larval weight, weight gain and day at maximum larval weight. There were significant differences in average weight gain per day (from third instar to prepupa) after treatments with different imidacloprid concentrations. A temporary knockdown effect was observed with higher concentrations and longer durations of contact with treated plates. Compared with untreated third instars, contact with imidacloprid-treated plates caused an increase in time spent (in seconds) on the glass plates resulting from an increase in number of stops (per second) and angular speed (degrees per second) and a decrease in linear speed, excluding stops (mm/second). The changes in locomotory behavior (i.e., duration of stay on untreated plate, number of stops and angular speed) lasted up to 24 h after contact with imidacloprid-treated plates.
Cannibalism and intraguild predation (IGP) are both common phenomena amongst aphidophagous coccinellids and serve as vital alternative feeding strategies which can prolong survival during periods of aphid scarcity. A reduction in essential prey density and the acceptance of conspecific or heterospecific prey are likely to have a considerable influence on both larval development and adult reproduction. However, little is known about the legacy of larval diet on adult performance. This paper considers the effects of the diet provided to larvae of Harmonia axyridis (Pallas) and Adalia bipunctata (Linnaeus) (Coleoptera: Coccinellidae) on the reproductive output of the resulting females. Results showed that larval diets, including treatments analogous to competition and IGP, did not affect adult longevity, ovipositional lag, proportion of eggs laid in clutches or ovariole number in H. axyridis or A. bipunctata. However, some variation in the maximum clutch size and oviposition rate was seen. A larval diet of unlimited aphids resulted in the largest clutches of eggs being laid by both species. The total number of eggs laid over 30 days was largest for H. axyridis when larvae were reared on unlimited aphids or limited aphids supplemented with either conspecific or heterospecific eggs, whereas oviposition was lower for A. bipunctata females that had received conspecific or heterospecific eggs in their larval diets. The results have also enabled us to make some general comparisons of reproductive parameters between the two species, and to refute the hypothesis that the maximum clutch size laid by a female ladybird is limited by the number of ovarioles within an ovary. We conclude that IGP of A. bipunctata eggs by H. axyridis larvae has a positive effect on reproductive output and is therefore likely to further contribute to the spread and increase of H. axyridis in Britain.
Chilocorus kuwanae Silvestri is an effective predator of Unaspis euonymi (Comstock), a scale insect harmful to spindle trees (Euonymus europeus L. and E. japonicus Thumb). The feeding behaviour was studied on wild adults, collected from spindle trees in the Botanic Garden of Perugia University, and fed on overwintering U. euonymi females. The insects were exposed to gradually changing constant temperatures (13°-->10°-->8°-->6°-->4°-->2°-->13°-->15°C) for a ten day period at each temperature. C. kuwanae adults preyed on the scale also at low temperatures. The number of scales eaten decreased with decreasing temperatures from the initial 13°C to 4°C, and at 2°C the trophic activity of C. kuwanae adults almost stopped although they made brief walks in the petri dishes. At all tested temperatures the ladybirds made holes in or lifted the scale cover and preyed on the female. Sometimes they lifted the scale cover , but did not prey on these U. euonymi females which were destined to die from cold. As the temperature dropped from 13°C to 4°C, the number of females eaten by ladybird males and females did not differ statistically. When the temperature was raised to 13°C and 15°C, the ladybirds resumed feeding. Large differences were recorded between sexes, with females showing a much higher feeding activity than males. Scale cover lifting was most frequent at the beginning of the experiment and then decreased with diminishing temperatures, although no significant difference was recorded among temperatures within the range from 10°C to 4°C. The threshold for trophic activity can be taken as 2°C since we noted that a few (12%) individuals on one day showed predatory activity. At 13°C and 15°C lifting activity rose again but remained at a lower level than at the initial exposure to 13°C. There was no significant difference in activity at 13 and 15°C upon raising the temperature. As for total number of U. euonymi damaged by C. kuwanae the trend in damage revealed the same pattern as for number of scales eaten. At the final exposure to 15°C, 60% of C. kuwanae females laid eggs. Our data demonstrate that C. kuwanae can reduce U. euonymi populations in a submediterranean environment even in winter when the range of temperatures is similar to that tested in this experiment.
Larvae of Aphidoletes aphidimyza (Rondani) (Diptera: Cecidomyiidae) secrete an oviposition-deterring pheromone (ODP). In choice tests, females of A. aphidimyza laid significantly fewer eggs on Vicia faba L. plants infested with Aphis fabae Scopoli (Homoptera: Aphidoidea) that were previously exposed to conspecific third-instar larvae or a water extract of their ODP.
A. aphidimyza females also laid fewer eggs on aphid-infested plants that were previously exposed to unfed first-instar larvae of Chrysopa oculata Say, Chrysopa perla (L.) or Chrysoperla carnea (Stephens) (Neuroptera: Chrysopidae), or second-instar larvae of Coccinella septempunctata L. (Coleoptera: Coccinellidae). However, the response to traces of C. carnea larvae was very weak.