Suitability of some farmscaping plants as nectar sources for the parasitoid wasp, Microplitis croceipes (Hymenoptera: Braconidae): Effects on longevity and body nutrients

In support of an ongoing study to evaluate potential farmscaping plants for utilization in organic vegetable production systems, we examined the effects of the nectar of three flowering plant species, sweet alyssum (Lobularia maritima), buckwheat (Fagopyrum sagittatum), and licorice mint (Agastache foeniculum), on the lifespan and body nutrient levels of the wasp, Microplitis croceipes (Cresson) (Hymenoptera: Braconidae), a key parasitoid of some caterpillar pests of vegetable crops in the USA. The greatest longevity (～16 days) was recorded for honey-fed wasps (positive control). Buckwheat significantly increased the lifespan of female and male wasps by at least two-fold relative to wasps provided water only (longevity = 3–4 days). Licorice mint significantly increased female longevity and numerically increased male longevity. Sweet alyssum slightly increased longevity of both sexes but this was not significantly different from the water only control. Females had a significantly longer longevity than males on all the diet treatments. The greatest carbohydrate nutrient levels (sugar content and glycogen) were recorded in honey-fed wasps followed by wasps fed buckwheat, whereas very little nutrients were detected in wasps provided sweet alyssum, licorice mint or water only. However, female wasps were observed to attempt to feed on all three flowering plant species. Thus, the low nutrient levels detected in wasps provided sweet alyssum or licorice mint may be because the nectars were not accessible or were of poor quality. Further studies will evaluate the effects of the promising farmscaping plants on the beneficial and pest insect communities in the field.     

Floral diversity, parasitoids and hyperparasitoids – A laboratory approach

Adding floral resources to agro-ecosystems to improve biological control can enhance the survival, egg load, and parasitism rate of insect parasitoids. However, this may not always be the case because the herbivore may benefit from the added resource as much as, or more than the third-trophic level. In addition, the natural enemies of those in the third-trophic level may also derive improved fitness from the added resources. Both these processes will dampen trophic cascades, leading to less-effective biological control. In this study, the effect of adding different flowering plants on the longevity, egg load, aphid parasitism rates and hyperparasitism of Aphidius ervi Haliday (Hymenoptera: Braconidae) by its hyperparasitoid Dendrocerus aphidum Rondani (Hymenoptera: Megaspilidae) were investigated, using the pea aphid Acyrthosiphon pisum Harris (Homoptera: Aphididae) as the herbivore. Parasitoids exposed to buckwheat survived, on average, between four to five times as long as those in the control (water) and those in phacelia, alyssum and coriander treatments survived three to four times as long. Hyperparasitoids exposed to buckwheat survived five to six times as long as those in the control and three to five times longer with the other plants compared with the control. Almost all flower species significantly increased parasitoid and hyperparasitoid egg loads and the number of parasitised aphids and parasitised mummies compared with control. Understanding the factors influencing the dynamics of multitrophic interactions involving flowering plants, herbivores, parasitoids and hyperparasitoids is a fertile area for future research. One of the most challenging areas in contemporary ecology concerns the relative importance of different types of biodiversity mediating trophic interactions and thereby influencing the structure of communities and food webs. This paper begins to explore this using an experimental, laboratory-based approach.     

Floral resources to enhance the potential of the parasitoid Aphidius colemani for biological control of the aphid Myzus persicae

Flowering plants have been widely used to enhance biological control. However, this approach has been limited to some extent by the lack of suitable flowering plant species of wide applicability, particularly for global pests. A key example is the green peach aphid, Myzus persicae (GPA). It is commonly attacked by the polyphagous koinobiont aphidiidae, Aphidius colemani, which is also of global occurrence. Here, eight flowering plants were evaluated for the potential enhancement of GPA biological control using A. colemani under laboratory conditions. These included buckwheat (Fagopyrum esculentum), alyssum (Lobularia maritima), white rocket (Diplotaxis erucoides.), wild mustard (Sinapis arvensis), lavender (Lavandula angustifolia), wild marjoram (Origanum vulgare), thyme (Origanum marjorana) and pepper mint (Mentha piperita). The effects of access to these flowers on the longevity (days), potential fecundity (number of dissected eggs) and parasitism rate for A. colemani compared with the control treatment (water) were studied. Longevity of A. colemani which had access to buckwheat was 4–5 times longer than the control and 2–3 times longer than it was in the other plant treatments; the latter did not differ significantly between each other. Potential fecundity of A. colemani was the highest when it had been provided with buckwheat flowers. Exposing A. colemani to flowering plants for longer time intervals (12 hr and 24 hr) increased the number of eggs produced compared with 6 hr. The number of parasitized aphids/female A. colemani with buckwheat flowers was the highest of all treatments; it ranged from 14 in the control to 219 with buckwheat. Further studies should be carried out under field conditions to determine the effect of a range of flowering plants on A. colemani. For example, although buckwheat was highly effective, in many climates it may be a useful component in mixtures comprising other, more robust species.     

The effects of floral understoreys on parasitism of leafrollers (Lepidoptera: Tortricidae) on apples in New Zealand

Abstract

• 1 Field and laboratory experiments on the conservation biocontrol of lepidopteran leafroller pests were carried out in apples at Lincoln, New Zealand.
• 2 Apple understoreys were planted with replicated treatments of alyssum (Lobularia maritima), phacelia (Phacelia tanacetifolia) and buckwheat (Fagopyrum esculentum).
• 3 Rates of parasitism of experimentally released larvae of the light‐brown apple moth, Epiphyas postvittana (Walker) (Lepidoptera: Tortricidae), by Dolichogenidea tasmanica (Cameron) (Hymenoptera: Braconidae) were significantly lower in phacelia and control treatments, and leafroller pupae were significantly more abundant in controls than in buckwheat and alyssum treatments.
• 4 Naturally occurring leafroller damage was up to 29% lower above all the floral understorey treatments compared with controls and there were more than twice as many D. tasmanica cocoons in the alyssum and buckwheat treatments than in controls.
• 5 Suction sampling of the understoreys gave D. tasmanica adult densities that were significantly more abundant in alyssum compared with other treatments. Numbers of Anacharis zealandica (Hymenoptera: Figitidae) (a parasitoid of larvae of the predatory brown lacewing) did not differ between treatments.
• 6 In the laboratory, flowering buckwheat and alyssum enhanced D. tasmanica longevity by up to 78% compared with the control, and buckwheat also enhanced potential fecundity by 62%.
• 7 In choice experiments, leafroller larvae in the laboratory consumed more than three‐fold more apple leaf material than they did of the three understorey species, although alyssum increased leafroller fecundity and longevity.
• 8 The use of floral understoreys for conservation biocontrol of apple pests is discussed, along with the potential negative effects of some flowering species on pest populations and orchard agronomic practices.

     

Evaluating the potential of buckwheat and cahaba vetch as nectar producing cover crops for enhancing biological control of Homalodisca vitripennis in California vineyards

The glassy-winged sharpshooter, Homalodisca vitripennis (Germar) is a significant pest of grapevines in California due to vectoring Xylella fastidiosa Wells et al., Buckwheat (Fagopyrum esculentum Moench) and vetch (Vicia sativa L. cv. ‘cahaba white’) are potential nectar-producing cover crop plants in California vineyards that could enhance Gonatocerus ashmeadi Girault, a parasitoid of H. vitripennis. Three aspects of these 2 plant species were evaluated. (1) Effect on parasitoid fitness: In the laboratory, buckwheat and vetch enhanced survival of G. ashmeadi by 9 and 6 days, respectively, compared to water. G. ashmeadi offspring production was 81% and 142% greater when females were provided vetch or buckwheat, respectively, compared to water. Buckwheat decreased G. ashmeadi female offspring by 19% compared to water and vetch. (2) Nectar production phenology in southern California: From April through September, buckwheat required only 23–32 days from sowing to nectar-producing flowers. Vetch required an additional 14–33 days to produce extrafloral nectar during June–August. The range in length of the nectar producing period between August 2007 and November 2007 was 41–52 days and 163–164 days for buckwheat and vetch, respectively. (3) X. fastidiosa Wells et al. host testing and H. vitripennis transmission studies: Needle inoculation of cover crop plants showed that X. fastidiosa successfully infected and replicated in buckwheat, vetch, sweet alyssum [Lobularia maritima (L.) Desv.] and coriander (Coriandrum sativum L.), plants that were assessed here or elsewhere as nectar producing cover crops for use in vineyards. H. vitripennis successfully transmitted X. fastidiosa between buckwheat and grapevine in the greenhouse and field. H. vitripennis successfully transmitted X. fastidiosa from grapevine to vetch in the field, while transmission studies investigating movement from vetch to grapevine in the greenhouse were inconclusive.     

Flowering alyssum (Lobularia maritima) promote arthropod diversity and biological control of Myzus persicae

Radish, Raphanus sativus is an important vegetable crop worldwide. It is the second most important vegetable after cabbage and cauliflower in winter (January to March) in Nepal. This crop is damaged by various herbivores such as the green peach aphid, Myzus persicae, the soybean hairy caterpillar, Spilarctia casigneta and the flea beetle, Monolepta signata. Prophylactic pesticide use is a part of the common pest management practice in Nepal. The candidate floral plant, alyssum, Lobularia maritima, was deployed in a radish field to improve pest biological control. Beneficial arthropods trapped such as Syrphidae, Coccinellidae, Carabidae, Staphylinidae, Formicidae, Lycosidae, Apidae and Ichneumonidae were significantly more abundant in flowering alyssum plots than the control (non-flowering) plots. Flowering alyssum in radish fields significantly increases the population of observed syrphids (larva and adult). Similarly observed ladybirds was slightly higher in flowering plot compared with control plot however that was not significant. These beneficial predators potentially increase the biological control of M. persicae. These results provide evidence of the alyssum’s ability to increase the abundance of predators and support the suppression of M. persicae in radishes. This study is useful in developing an integrated pest management protocol by integrating flowering strips in radish fields. Habitat manipulation in radish fields by maintaining flower strips can improve pest biological control and support the provision of multiple ecosystem services that restore diminished ecosystem functions in agriculture.     

Measuring parasitoid movement from floral resources in a vineyard

The movement of natural enemies from floral resources is of particular importance in habitat manipulation research, as the distances that they disperse have consequences for the deployment of floral resources to improve insect natural enemy fitness. A number of marking techniques can be used to measure natural enemy movement; however, many of these are labour-intensive and not appropriate for many natural enemy species, the alternative, self-marking techniques, are less common. The aim of this study was to determine whether rubidium chloride (RbCl) could be used to measure the movement of Dolichogenidea tasmanica (Cameron) (Hymenoptera: Braconidae) from flowering buckwheat, Fagopyrum esculentum Moench plants in an organic vineyard. D. tasmanica is the most common parasitoid of leafroller larvae, a serious pest of grapevines in Australia and New Zealand. Foliar applications of rubidium chloride were made to a single strip of buckwheat in the centre of each of five vineyard areas. Sticky traps were placed in each area at distances of 0, 4, 10 and 30 m in opposite directions from the buckwheat to collect adult D. tasmanica. D. tasmanica were marked with rubidium after buckwheat plants had been sprayed with RbCl and were trapped up to 30 m from the plants within a seven-day sampling period. This study indicates that RbCl can be used to mark parasitoids to measure their movement from floral resources and may be used to inform decisions on the deployment of appropriate flowering plant species in conservation biological control.     

Host range of a newly introduced parasitoid, Binodoxys communis among common aphid species in Hawaii

Binodoxys communis (Gahan) (Hymenoptera:Braconidae), a parasitoid of aphids originally from China, was introduced into Hawaii and evaluated in the laboratory for its ability to detect, accept, oviposit and develop in Aphis gossypii reared on two host plants, plus five other common aphid species. The parasitoid was able to detect all six aphid species and to successfully sting five species, with highest preference for those in the genus Aphis. Aphis species were highly suitable for parasitoid development. Other species were only marginally suitable. Parasitoids spent less time searching on plants of less acceptable aphids. Aphid defensive behaviors did not affect oviposition success, but did lengthen the parasitoid’s handling time of several aphid species. Host acceptance was positively correlated with host suitability, yet one unsuitable host was readily accepted for oviposition.     

Responses of the specialist biological control agent,Aleochara bilineata,to vegetational diversity in canola agroecosystems

Plant biodiversity is known to affect insect populations, both herbivores and their natural enemies, and as a consequence, habitat management through increased plant species composition and abundance can be exploited for sustainable pest management. In agroecosystems where crop monocultures are the routine production practice, plant biodiversity can be increased by maintaining small populations of weeds, with potential beneficial effects arising from concomitant increases in the abundance of predator and parasitoid populations. We manipulated weed populations in both species of canola, Brassica rapa L. and Brassica napus L., to investigate responses of adults of Aleochara bilineata Gyllenhal (Coleoptera: Staphylinidae), an important natural enemy of root maggots (Delia spp., Diptera: Anthomyiidae). Larval root maggots feed on canola taproots, disrupting the flow of water and nutrients within the plants, causing substantial yield reductions. Aleochara bilineata is a predator–parasitoid that attacks all root maggot pre-imaginal life stages. Activity density of A. bilineata increased as monocotyledonous weed biomass declined. Significant preferences between canola species were observed, with A. bilineata associated most frequently with B. rapa compared with B. napus. Our research suggests that improved management of root maggot infestations in canola through enhancement of populations of the A. bilineata predator–parasitoid could be accomplished by reducing weed infestations; however, such recommendations should consider other predators in the system and the role of weeds in reducing root maggot oviposition and damage.     

Can the growing of transgenic maize threaten protected Lepidoptera in Europe?

We evaluated whether protected European butterflies can potentially be at risk if transgenic maize is extensively grown in Central Europe. We explored potential consequences of both insect resistant (IR) and herbicide resistant (HR) transgenic maize. IR maize can produce pollen that is toxic to lepidopteran larvae, and this puts butterfly species at possible risk if the presence of young larvae coincides with maize flowering, during which large quantities of maize pollen can be deposited on vegetation. By considering the timing of maize flowering in Europe and the phenology of the protected Lepidoptera species, we found that 31 species had at least one generation where 50% of the larval stage overlapped with maize flowering, and 69 species for which first instar larvae were present during maize pollen shedding. HR maize allows high concentration herbicide treatments on fields without seasonal limitation, which can drastically reduce weed densities. In cases where such weed species are host plants for protected butterflies, reduced host plant/food availability can result, causing population decreases. By using published information, we first identified the important weed species in major maize-growing European countries. Subsequently, we checked whether the host plants of protected Lepidoptera included species that are common maize weeds. We identified 140 protected species having food plants that are common weeds in one or more of the major European maize-growing countries. If HR maize is grown in Europe, there is a potential hazard that their food plants will seriously decline, causing a subsequent decline of these protected species.     

Response of the two rare arable weed species Lithospermum arvense and Scandix pecten-veneris to climate change conditions

Rare weeds are currently under pressure due to intensifying arable management practices, and as a consequence of climate change, these practices will likely become even more intensive, together with a greater uniformity of land use. As a result, ecological stresses will increase for most species of rare weeds, in some cases leading to their further decline or even extinction. Moreover, climate change will alter the suitability of the environment for many plants, since average temperatures are predicted to increase and precipitation extremes to become more common. For most arable weed species it is unclear, whether the anticipated changes in environmental conditions are disadvantageous or beneficial. Little is known about specific biological responses of rare weeds to climate changes, and this study attempts to close some of these knowledge gaps. Here, the rare arable weed Lithospermum arvense and the endangered arable species Scandix pecten-veneris were investigated with regard to the effects of higher temperature and different crop densities on flowering time, shoot development, plant height, dry mass and seed production. Semi-field experiments were conducted with winter wheat crop for 3 years, involving 48 climate cages, in which every second was a variant of warmer temperature and contrasting crop density. We observed that S. pecten-veneris flowered earlier under warmer conditions and had fewer seeds and less biomass in the dense wheat crop compared to control conditions, while L. arvense grew taller, it produced fewer seeds in the high density crop. We suggest that such data concerning the biological responses of weeds can improve the precision of bioclimatic distribution models. Finally, we discuss strategies, such as relocation or non-intrusive management practices, for preventing further disappearances of rare arable weeds. Our results should be of considerable interest for the fields of plant ecology, biodiversity research and conservation.     

Olfactory attractiveness of flowering plants to the parasitoid Microplitis mediator: potential implications for biological control

In agricultural landscapes, the lack of floral nectar can be a major difficulty for nectar feeding parasitoids. This problem can be reduced by the addition of suitable wildflowers. To date, flowers have mainly been studied in terms of effects on parasitoid fitness, not taking into account the essential role of flower attractiveness for foraging parasitoids. This study experimentally tested the olfactory attractiveness of five wildflowers (bishop’s weed, cornflower, buckwheat, candytuft, and oregano) to the parasitoid Microplitis mediator (Haliday) (Hymenoptera: Braconidae). We conducted choice experiments in a Y-tube olfactometer to test the attractiveness of flowers against air, and relative attractiveness in paired choice tests. Our results showed that all the flowers were highly attractive and that in paired choice tests cornflower and candytuft were equally attractive and more attractive than buckwheat. These results indicate that M. mediator has evolved innate preferences that could be effectively exploited in biological control.     

Enhancing biological control by an omnivorous lacewing: Floral resources reduce aphid numbers at low aphid densities

The availability of plant resources to omnivorous arthropod predators may have a positive, negative or negligible effect on their population densities and predation rates, depending on the availability of prey. At high prey densities, flowering buckwheat has been shown to negatively impact populations of the brown lacewing, an omnivorous predator, due to the probable increase in parasitism rate of lacewing larvae by their primary parasitoid, Anacharis zealandica. However, little is known about the effect of buckwheat flowers on this insect community at low prey densities. We used field cages to assess the effects of nectar provision by flowering buckwheat on the population dynamics of the pea aphid, the brown lacewing and its parasitoid A. zealandica in an alfalfa field, under low aphid densities in the New Zealand summer. The insects were sampled every 2 weeks with a suction device, then counted and released on each sampling date from 15 January to 15 March 2007. Buckwheat significantly increased lacewing populations and significantly decreased aphid numbers by 70% and 39%, respectively. The buckwheat had its greatest effect at the end of summer (February/March) for both these species. It had no effect on A. zealandica abundance.     

The current status of biological control of weeds in southern China and future options

China has become one of the countries most seriously affected by invasive alien weeds in the world. Weeds impact agriculture, the environment and human health, and conventional control methods such as herbicides are expensive, damaging to human health and unsustainable. As the impacts and costs of weed control in China increase, there is an urgent need to manage some of the more important weeds through more sustainable methods. Classical biological control of invasive alien weeds is environmentally-friendly and sustainable. Biological control in China began in the 1930s with the introduction of two agents into Hong Kong for the control of Lantana camara. Since then, a further seven biological control agents have been introduced into China to control four weed species. In addition, 11 biological control agents targeting seven weed species have naturally spread into China. Together, these biological control agents are helping to control some of China's worst weeds. However, these efforts are only a small portion of the weeds that could be targeted for weed biological control. This paper reviews the current status of weed biological control efforts against introduced weeds in ten provinces and regions in southern China and provides a platform to identify the most effective and appropriate weed biological control opportunities and programmes to pursue in the future. Introducing additional safe and effective biological control agents into China to help manage some of the worst weeds in the region should reduce the use of herbicides and impacts on human health and the environment, while increasing productivity and food security.     

Increasing floral diversity for selective enhancement of biological control agents: A double-edged sward?

Floral resource subsidies can have differential effects on insect herbivores compared with the herbivores’ natural enemies. While the nectar of many plant species enhances parasitoid fitness, it may also increase damage by herbivores. This may occur as a result of enhanced herbivore fitness or by enhancing fourth-trophic-level processes, possibly disrupting a trophic cascade as a result. The responses of different arthropod guilds to different floral resource subsidies were compared using Plutella xylostella (Hyponomeutidae), its parasitoid Diadegma semiclausum (Ichneumonidae) and data from two other published herbivore–parasitoid systems. These were Dolichogenidea tasmanica (Braconidae) and its host Epiphyas postvittana, and Copidosoma koehleri (Encyrtidae) and its host Phthorimaea operculella. The parasitoids and hosts in the three systems exhibited differential responses to the nectar sources. The differential response was not explained by morphology, demonstrating that physical access to nectaries alone does not determine the potential of flowers as a food source. For some flowering plants, enhancement of herbivore and parasitoid fitness occurred. Other flowering plants, such as buckwheat and phacelia, conferred a selective enhancement on parasitoids by increasing only their fitness. More effective conservation biocontrol may be achieved by the provision of selective floral resources. Attempts to ‘engineer’ agroecosystems to enhance biological control require an extensive knowledge of the ecology of the herbivore, its enemies and their interactions with potential resource subsidies.     

Flower color affects tri-trophic-level biocontrol interactions

The adults of many parasitoid species require nectar for optimal fitness, but very little is known of flower recognition. Flight cage experiments showed that the adults of an egg parasitoid (Trichogramma carverae Oatman and Pinto) benefited from alyssum (Lobularia maritima L.) bearing white flowers to a greater extent than was the case for light pink, dark pink or purple flowered cultivars, despite all cultivars producing nectar. Survival and realised parasitism on all non-white flowers were no greater than when the parasitoids were caged on alyssum shoots from which flowers had been removed. The possibility that differences between alyssum cultivars were due to factors other than flower color, such as nectar quality, was excluded by dying white alyssum flowers by placing the roots of the plants in 5% food dye (blue or pink) solution. Survival of T. carverae was lower on dyed alyssum flowers than on undyed white flowers. Mixing the same dyes with honey in a third experiment conducted in the dark showed that the low level of feeding on dyed flowers was unlikely to be the result of olfactory or gustatory cues. Flower color appears, therefore, to be a critical factor in the choice of plants used to enhance biocontrol, and is likely also to be a factor in the role parasitoids play in structuring invertebrate communities.     

Phytotoxic Potential of Trans-chalcone on Crop Plants and Model Species

Chalcones are flavonoid precursors that recently have been found to disrupt mitochondrial function and induce apoptosis in Arabidopsis radicles. However, whether they are potentially useful for weed control as selective herbicides depends on whether they are phytotoxic for important weeds and are not toxic for crops. This work determines the phytotoxicity of chalcone for the germination and early development of a variety of crop species and associated weeds. Also, the phytotoxic potential was investigated in chalcone-watered or sprayed adult plants of Arabidopsis, a common model in phytotoxicity assays. Chalcone was detrimental mainly to the germination of Plantago lanceolata and Lactuca sativa and to the early root growth of Amaranthus retroflexus, Echinochloa crus-galli, and P. lanceolata, and likewise detrimental to the development of adult Arabidopsis. The morphology and physiology of adult Arabidopsis plants watered or sprayed with chalcone confirmed that this metabolite is also phytotoxic for adult plants and showed that the mechanism of its action on plant metabolism depends on whether it is administered by spraying or watering. These results support the role of chalcone as a plant growth regulator and its potential use in weed management in the field.     

Inhibitory effects of leachate from Eupatorium adenophorum on germination and growth of Amaranthus retroflexus and Chenopodium glaucum

Amaranthus retroflexus L. and Chenopodium glaucum L. are two widely distributed destructive weeds. Their strong adaptability and massive seed production make them the hardest weeds to deal with. This present study intended to investigate the effect of leachate from Eupatorium adenophorum on the growth of these weeds and explore the potential to develop an environmental friendly strategy to use the leachate to control the weeds. Seeds of A. retroflexus L. and C. glaucum L. were soaked in solutions containing 0%, 0.6%, 1.25%, 2.5%, and 5% leachate from E. adenophorum leaves. A. retroflexus and C. glaucum seedlings grown in pots were sprayed with leachate solutions in the same concentration range. The effects of these leachate solutions on membrane permeability and germination of seeds, and growth and physiological characteristics of the seedlings were investigated. The highest concentration of leachate (5%) caused significant damage to the cell membrane of seeds of both weed species, whereas lower concentrations (0.6%) promoted repair of the membrane system, as reflected by higher and lower than control in relative conductivity (RC), respectively. Different concentrations of leachate showed distinct allelopathic inhibitory effects on the two weed species; lower concentrations showed weak inhibitory or even positive effects, whereas higher concentrations showed stronger inhibitory effects. Higher concentrations of leachate (2.5% and 5%) delayed germination and significantly decreased the emergence rate of the seeds, survival rate, and dry matter accumulation of the seedlings. When treated by 5% leachate, the emergence date of A. retroflexus was delayed by 3.6 d, emergence rate of the seeds and survival rate was 69.1% and 70.6% of the control, respectively, seedling dry matter was 48.6% less than the control; In the case of C. glaucum, the emergence date was delayed by 2.7 d, emergence rate of the seeds and survival rate was 45.1% and 58.6% of the control, respectively, seedling dry matter was 44.7% less than the control. There were significant interactions among the different concentrations of leachate and the length of treatment period with respect to activities of antioxidant enzymes, malondialdehyde (MDA) contents, and chlorophyll contents. Seedlings treated with 0.6%, 1.25%, or 2.5% leachate solution for 24–72 h showed increased superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) activities. When seedlings were treated with leachate solutions for 96 h, antioxidant enzyme activities and chlorophyll content decreased in A. retroflexus, but only CAT activity decreased in C. glaucum. When seedlings of the two weed species were treated with 5% leachate solution, CAT activity and chlorophyll content decreased and MDA content gradually increased with longer treatment times (from 24 to 96 h). The two weed species showed different allelopathic responses to E. adenophorum; A. retroflexus was more sensitive than C. glaucum. Based on the investigation, it could be speculated that the delayed germination and low germination rate of the weeds after treatment by leachate could be due to the fact that leachate damaged the membrane system of the seeds. By delaying germination, lowering the germination rate of the weeds and inhibiting seedling growth, leachate from E. adenophorum could provide an effective way of controlling the weeds.     

Effects of floral resources on the efficacy of a primary parasitoid and a facultative hyperparasitoid

Resources added to agroecosystems to enhance biological control are potentially available to multiple members of the resident insect community—not only the biological control agents for which the resources are intended. Many studies have examined the effects of sugar feeding on the efficacy of biological control agents. However, such information is lacking for other, interacting species such as facultative hyperparasitoids, which may contribute to pest suppression but can also interfere with introduced biological control agents. Under greenhouse conditions, we tested the direct effects of sugar and nectar provisioning on the longevity, host‐killing impact and offspring production of two pupal parasitoids associated with leek moth, Acrolepiopsis assectella: the introduced biological control agent, Diadromus pulchellus, and the native facultative hyperparasitoid, Conura albifrons. Adding sucrose, buckwheat or a combination of buckwheat and common vetch to a sugar‐deprived system (potted leek plants in cages) increased parasitoid longevity and resulted in higher leek moth parasitism and mortality compared to water or common vetch treatments. However, the two parasitoid species exhibited a distinct temporal response to the treatments, likely influenced by differences in their life histories. This study provides insight into how integrating conservation biological control techniques could affect the success of a classical biological control programme.