Attractiveness of synthetic volatile blends of flowering rice panicles to Trigonotylus caelestialium (Kirkaldy) (Heteroptera: Miridae)

The attractiveness of 22 synthetic volatile blends or seven individual chemicals emitted from flowering rice panicles to a rice leaf bug, Trigonotylus caelestialium (Kirkaldy), were investigated with an olfactometer to identify the active compounds responsible for the invasion of the bugs into paddy fields. n‐Decanal attracted only male bugs, whereas β‐caryophyllene attracted only females. β‐Elemene repelled males and methyl benzoate marginally repelled females. The other chemicals did not attract or repel male and female bugs at all. Two‐, 3‐, 4‐ and 5‐component blends of β‐caryophyllene, n‐decanal, n‐tridecene, methyl salicylate and geranyl acetone were attractive to neither females nor males. Two‐component blends comprised of β‐caryophyllene and methyl salicylate, or n‐decanal and methyl salicylate, marginally repelled females. The three‐component blend comprised of β‐caryophyllene, n‐decanal and geranyl acetone marginally repelled females. The five‐component blend comprised of β‐caryophyllene, n‐decanal, n‐tridecene, methyl salicylate and geranyl acetone repelled males. The seven‐component blend comprised of β‐caryophyllene, n‐decanal, n‐tridecene, methyl salicylate, geranyl acetone, methyl benzoate and β‐elemene attracted female bugs and marginally attracted male bugs. Six‐component blends without any one of these seven components were not attractive to the bugs although the six‐component blend without n‐decanal was marginally attractive to females. The six‐component blend without n‐tridecene repelled males. These findings suggest that mixtures of these seven compounds play an important role in the attractiveness of flowering rice panicles to both sexes of the bugs, although the attractiveness of individual compounds differs between sexes.     

Tolerance of Bt corn (MON 810) to maize stem borer, Chilo partellus (Lepidoptera: Pyralidae)

Transgenic corn (MON 810), expressing the Bacillus thuringiensis (Bt) protein, Cry1Ab, was evaluated under greenhouse conditions for its tolerance to the maize stem borer, Chilo partellus. Bt corn (MON 810) provided effective protection against the stem borer even under a high level of larval infestation in the greenhouse. The observed tolerance is examined and discussed in the light of the susceptibility of C. partellus to the Cry1Ab protein in laboratory bioassays. The implications of the tissue concentrations of Cry1Ab in MON 810, and baseline susceptibility recorded in the current study, for insect-resistance management are discussed.     

Density thresholds for Nesidiocoris tenuis (Heteroptera: Miridae) in tomato crops

Nesidiocoris tenuis (Reuter) (Heteroptera: Miridae) is common in vegetable crops of the Mediterranean area, with an increasing worldwide range of geographical distribution. This omnivore is a reputed predator of small arthropod pests, but also produces injuries on vegetative and reproductive plant parts. The aim was to estimate density thresholds based on N. tenuis and whitefly abundance for the management of N. tenuis in tomato crops. The assay was carried out in mesh-walled and plastic greenhouses in southern Spain during 2004 and 2007. The natural population dynamics of N. tenuis and whitefly were monitored, and impact on yield quantified. The economic injury level and intervention threshold were predicted based on the zoophytophagous response of N. tenuis and the yield compensation of tomato plants. The proportion of aborted flowers on the tomato plants was related directly to the abundance of N. tenuis and inversely to the interaction between the number of N. tenuis and the number of whitefly immatures. Over-compensation of fruit weight was predicted for flower abortion rates due to N. tenuis lower than 0.171. No yield reduction is expected for values <0.65 N. tenuis per leaf, independent of the whitefly abundance, nor for up to 5 N. tenuis and >26 whitefly immatures per leaf. For intermediate N. tenuis levels, the outcome depends on the prey density. The probability of N. tenuis producing yield loss in tomato crops increases at N. tenuis:whitefly ratios >0.168. Yield reduction is expected after N. tenuis population peaks, when whitefly numbers have been reduced.     

Use of maize pollen by adult Chrysoperla carnea (Neuroptera: Chrysopidae) and fate of Cry proteins in Bt-transgenic varieties

We investigated the use of maize pollen as food by adult Chrysoperla carnea under laboratory and field conditions. Exposure of the insects to insecticidal Cry proteins from Bacillus thuringiensis (Bt) contained in pollen of transgenic maize was also assessed. Female C. carnea were most abundant in a maize field when the majority of plants were flowering and fresh pollen was abundant. Field-collected females contained an average of approximately 5000 maize pollen grains in their gut at the peak of pollen shedding. Comparable numbers were found in females fed ad libitum maize pollen in the laboratory. Maize pollen is readily used by C. carnea adults. When provided with a carbohydrate source, it allowed the insects to reach their full reproductive potential. Maize pollen was digested mainly in the insect's mid- and hindgut. When Bt maize pollen passed though the gut of C. carnea, 61% of Cry1Ab (event Bt176) and 79% of Cry3Bb1 (event MON 88017) was digested. The results demonstrate that maize pollen is a suitable food source for C. carnea. Even though the pollen grains are not fully digested, the insects are exposed to transgenic insecticidal proteins that are contained in the pollen.     

A 3-year field-scale monitoring of foliage-dwelling spiders (Araneae) in transgenic Bt maize fields and adjacent field margins

Concerns have been raised that genetically modified Bt maize may harm non-target organisms, and there is a general call and need for a risk assessment of Bt maize. Spiders are important pest predators in agroecosystems and in maize, and can be exposed to the Bt toxin by herbivorous or pollen-collecting prey, by active Bt maize pollen feeding, and by ingesting their pollen-dusted webs. The foliage-dwelling spider fauna of Bt maize fields and adjacent margins was monitored and compared to non-transgenic maize fields. The study took place during the vegetation seasons of 2001–2003 in Bavaria, South Germany. Maize fields and adjacent nettle field margins were colonized by a typical spider assemblage, dominated by space-web spiders (Theridiidae and Linyphiidae). Abundance and species richness of spiders was higher in nettle margins than in maize fields. The proportion of hunting spiders tended to be higher in nettle margins, whereas space-web spiders tended to be more frequent in maize fields. Bt maize showed no consistent effect on individual numbers, species richness and guild structure of spiders in maize fields and adjacent nettle field margin strips. The spider abundance was higher in Bt treatments in 2003, whereas in 2001 and 2002 no significant differences were found. The results provide an important contribution for the implementation of case-specific and general surveillance of transgenic plants to be employed due to the regulations of the European Community.     

Oviposition of the Colorado potato beetle (Leptinotarsa decemlineata) and natural predation on its egg masses in Bt-expressing fields

Generalist predators are relevant natural enemies of the Colorado potato beetle (CPB) in Europe. In fields of insect resistant genetically modified plants (GMPs), predators could be exposed to toxins either directly (e.g., via pollen), or indirectly through feeding on herbivorous prey. Hence, they represent an important functional group to consider when studying environmental impacts of GMPs. CPB females show a ‘bet-hedging’ strategy in spatial and temporal distribution of eggs, through which the species tries to minimize the risks of progeny loss due to adverse conditions. Experimental fields of GM eggplants expressing Cry3Bb toxin and potatoes expressing Cry1Ab toxin were set up. CPB egg masses were counted on naturally infested plants at four time points during the field season of each crop. To assess predation, newly deposited egg masses were marked at the same dates. Daily visual observations were conducted recording the numbers of intact or preyed eggs and neonate larvae. In both cases, oviposition was similar between GM and control plots, as the number of egg masses per plant and the number of eggs per mass did not differ significantly between treatments. A statistical analysis of the spatial distribution of egg masses revealed a similar aggregation in the potato field, whereas in the eggplant field, the variance of the number of egg masses per plant was smaller than expected in GMP plots. The predation rate was similar between treatments. These results suggest that the ecological function of natural predation on CPB eggs in GM plots was not impaired.     

Host-plant mediated effects of transgenic maize on the insect parasitoid Campoletis sonorensis (Hymenoptera: Ichneumonidae)

Determining the impact of genetically modified (GM) crops on beneficial organisms is an important aspect of the environmental risk assessment of GM crops. In the present study, the impact of Bt maize expressing Cry1Ab on the development and behaviour of the parasitoid Campoletis sonorensis was compared to individuals reared on hosts fed conventionally bred plants partially resistant to the European corn borer (Ostrinia nubilalis Hübner) and on susceptible maize hybrids. Adult parasitoids reared on Bt maize-fed Spodoptera frugiperda larvae were significantly smaller (15–30%) than those reared in hosts fed either of the conventional maize hybrids. The magnitude of this effect was dependent on the size of the host at oviposition and its subsequent growth rate. The development time of C. sonorensis was not affected by the maize treatment. In choice tests, female parasitoids displayed no preference for hosts fed a specific maize hybrid. No Cry1Ab was detected within adult parasitoids.     

The effects of mullein plants (Verbascum thapsus) on the population dynamics of Dicyphus hesperus (Heteroptera: Miridae) in tomato greenhouses

The response of Dicyphus hesperus Knight (Heteroptera: Miridae) to whitefly populations in tomato greenhouses was measured in the presence and absence of mullein (Verbascum thapsus L.) as an alternative host plant. The dynamics of the D. hesperus population on tomato (Lycopersicon esculentum Mill.) and on mullein plants were followed through an entire growing season. In houses with mullein plants, more predators occurred on mullein when whitefly density was low on tomato. A mark-release-recapture experiment where rabbit IgG was used as an external marker showed that D. hesperus adults moved from mullein plants to tomato plants. D. hesperus was always more abundant in houses with mullein than in the houses with tomato plants alone. Movements between tomato and mullein plants are discussed as a strategy to optimize predator foraging. The use of mullein as an alternative host plant may contribute to the establishment of D. hesperus and help to preserve the predator population when prey on tomato crops is scarce.     

Effect of diet and mating status on ovarian development and oviposition in the polyphagous predator Macrolophus caliginosus (Heteroptera: Miridae)

The mirid bug Macrolophus caliginosus is commercially reared on eggs of Ephestia kuehniella, constituting an effective but expensive factitious food. Artificial diets can decrease the rearing costs of this natural enemy, but developing and evaluating an artificial diet is a very time-consuming activity. In the current study, development and reproduction of M. caliginosus on two artificial diets based on egg yolk were investigated. The artificial diets resulted in longer development and lower adult weights, but survival was comparable with that of control insects fed E. kuehniella eggs. Reproductive potential of the predator reared on factitious and artificial foods was assessed using a dissection method. The influence of nymphal food on fecundity was less important than that of adult food. Adults fed E. kuehniella eggs had a preoviposition period of about 4 days, whereas adults offered only plant material started laying eggs about 7 days after emergence. Ovarian scores at day 7 were higher for females fed E. kuehniella eggs than for those given access only to a tobacco leaf. Ovarian scores were not significantly affected by mating status. In a final test, a parallel comparison of two methods for assessing reproductive response to diet was made. Here, adult couples were offered one of four diets: E. kuehniella eggs, one of two artificial diets or no food. Half of the females were dissected and the other half was held for determining lifetime oviposition. Females fed E. kuehniella eggs had superior ovarian scores and laid more eggs than those fed either artificial diet or those given no extra food. A good correlation (r = 0.97) was obtained between ovarian scores and oviposition data, indicating that dissecting females after 1 week provides a reliable estimate of fecundity as affected by diet quality. Rapid reproductive assessments as used in the current study will help to increase the rate of development of artificial diets and may contribute to more cost effective production methods for augmentative biological control agents.     

Contributions of Robert (Bob) J. O’Neil to the field of predaceous Heteroptera

Predaceous Heteroptera are important components of natural and managed habitats. The extent of predatory habits among taxa ranges from those that are totally (or nearly totally) predaceous to those that are nearly totally phytophagous, but occasionally feed on arthropod prey. Because of that variability in predatory habit, the contributions of heteropteran taxa to management of pest species will vary greatly. The late Robert (Bob) J. O’Neil (1955–2008) added significantly to understanding the roles of and benefits from facultatively predaceous Heteroptera. His focus on behavioral and physiological attributes that permitted facultatively predaceous species to persist in agricultural habitats demonstrated that facultative predators could help prevent pest outbreaks, but were less effective at reducing numbers of species already considered above economic thresholds.     

Wing Movement Behavior in Long- and Short-Winged Morphs of the Flightless Bug Pyrrhocoris apterus L. (Heteroptera: Pyrrhocoridae)

The aim of the present paper was to study, with the use of video-recordering and computerized methods, the flight and wing movement behavior in two wing morphs of the flightless bug Pyrrhocoris apterus during the first 14 days of their adult life. We demonstrated the capability of macropterous males and females of this heteropteran to flap their fore- and hindwings for the first time. Flight was not observed in any of the tested males and females. We revealed that wing flapping does not occur earlier than on the fourth and fifth day after adult emergence in males and females, respectively. Time-series analysis of the obtained data showed that the maximum activity of wing flaps is limited to the light phase of the 12-h light/12-h dark photocycle, with the peak occurring in the morning, i.e., about 3 h after turning the light on. No substantial differences in the peaks of wing flapping activities in males versus females were found. The present paper is the first experimental demonstration of wing flap activity in a representative species with a nonfunctional alary polymorphism.     

Effects of soybean proteinase inhibitors on development of the soil mite Scheloribates praeincisus (Acari: Oribatida)

Proteinase inhibitors (PI) are present in plant tissues, especially in seeds, and act as a defense mechanism against herbivores and pathogens. Serine PI from soybean such as Bowman–Birk (BBPI) and Kunitz have been used to enhance resistance of sugarcane varieties to the sugarcane borer Diatraea saccharalis (Fabricius) (Lepidoptera: Crambidae), the major pest of this crop. The use of these genetically-modified plants (GM) expressing PI requires knowledge of its sustainability and environmental safety, determining the stability of the introduced characteristic and its effects on non-target organisms. The objective of this study was to evaluate direct effects of ingestion of semi-purified and purified soybean PI and GM sugarcane plants on the soil-dwelling mite Scheloribates praeincisus (Berlese) (Acari: Oribatida). This mite is abundant in agricultural soils and participates in the process of organic matter decomposition; for this reason it will be exposed to PI by feeding on GM plant debris. Eggs of S. praeincisus were isolated and after larvae emerged, immatures were fed milled sugarcane leaves added to semi-purified or purified PI (Kunitz and BBPI) or immatures were fed GM sugarcane varieties expressing Kunitz and BBPI type PI or the untransformed near isogenic parental line variety as a control. Developmental time (larva-adult) and survival of S. praeincisus was evaluated. Neither Kunitz nor BBPI affected S. praeincisus survival. On the other hand, ingestion of semi-purified and purified Kunitz inhibitor diminished duration of S. praeincisus immature stages. Ingestion of GM senescent leaves did not have an effect on S. praeincisus immature developmental time and survival, compared to ingestion of leaves from the isogenic parental plants. These results indicate that cultivation of these transgenic sugarcane plants is safe for the non-target species S. praeincisus.     

Prey mediated effects of Bt maize on fitness and digestive physiology of the red spider mite predator Stethorus punctillum Weise (Coleoptera: Coccinellidae)

The present study investigated prey-mediated effects of two maize varieties expressing a truncated Cry1Ab, Compa CB (event Bt176) and DKC7565 (event MON810), on the biology of the ladybird Stethorus punctillum. Although immuno-assays demonstrated the presence of Cry1Ab in both prey and predator collected from commercial maize-growing fields, neither transgenic variety had any negative effects on survival of the predator, nor on the developmental time through to adulthood. Furthermore, no subsequent effects on ladybird fecundity were observed. As a prerequisite to studying the interaction of ladybird proteases with Cry1Ab, proteases were characterised using a range of natural and synthetic substrates with diagnostic inhibitors. These results demonstrated that this predator utilises both serine and cysteine proteases for digestion. In vitro studies demonstrated that T. urticae were not able to process or hydrolyze Cry1Ab, suggesting that the toxin passes through the prey to the third trophic level undegraded, thus presumably retaining its insecticidal properties. In contrast, S. punctillum was able to activate the 130 kDa protoxin into the 65 kDa fragment; a fragment of similar size was also obtained with bovine trypsin, which is known to cleave the protoxin to the active form. Thus, despite a potential hazard to the ladybird of Bt-expressing maize (since the predator was both exposed to, and able to proteolytically cleave the toxin, at least in vitro), no deleterious effects were observed.     

Life History and Laboratory Host Range ofEccritotarsus catarinensis(Carvalho) (Heteroptera: Miridae), a New Natural Enemy Released on Water Hyacinth (Eichhornia crassipes(Mart.) Solms-Laub.) (Pontederiaceae) in South Africa

A mirid,Eccritotarsus catarinensis(Carvalho), was studied as a potentially damaging natural enemy for water hyacinth, (Eichhornia crassipes(Mart.) Solms-Laub.), in South Africa. In the laboratory, eggs were inserted into the leaf tissue parallel to the leaf surface. The four nymphal instars fed gregariously with the adults mainly on the undersurface of the leaves, causing severe chlorosis at high population levels. The duration of immature stages (egg and nymphs) was approximately 23 days, while the adults survived for approximately 50 days. Favorable biological characteristics ofE. catarinensisincluded a high rate of increase, gregarious habits, long-lived and mobile adults, and several generations per year. Laboratory host range of the mirid was determined by adult choice trials on 67 plant species in 36 families and adult no-choice trials on five species in the Pontederiaceae. Feeding was recorded on all Pontederiaceae tested and oviposition on four of the five species. However, these plant species proved to be inferior hosts forE. catarinensisin comparison to water hyacinth, suggesting thatE. catarinensiswould be an acceptable natural enemy for water hyacinth in South Africa.     

Escape of Lygus hesperus (Heteroptera: Miridae) Eggs from Parasitism by Anaphes iole (Hymenoptera: Mymaridae) in Strawberries: Plant Structure Effects

Herbivorous insects in natural and agricultural systems experience variation in parasitoid attack on different plant species due to direct and indirect plant influences on parasitoids. Lygus hesperus is a native polyphagous mirid that suffers up to 100% parasitism by the native egg parasitoid Anaphes iole in certain weed hosts, but with inundative releases in commercial strawberries, we achieve <65% L. hesperus suppression. We examined L. hesperus egg distribution in individual strawberry plants and parasitism by A. iole of eggs in different strawberry plant structures to determine whether plant-related factors affected parasitoid performance in strawberries. L. hesperus laid more eggs (46.5% of all eggs laid) in the fruit (between the achenes [seeds] in the fleshy receptacle) than in the petiole (23.3%), leaflet (20.3%), peduncle (6.2%), or calyx (3.7%). In a no-choice test, parasitism by A. iole was higher in the petiole (96.7%), calyx (91.9%), and leaflet (85.2%) than in the fruit (51.8%), in which the achenes appeared to hinder parasitoid access to host eggs. In addition, in young fruits in which the interachene distance was minimum, parasitism was considerably lower (25.4%) than in fruits in which receptacle swelling had resulted in interachene distances that were medium (65.7% parasitism) or large (77.1% parasitism). Our results suggest that strawberry fruits can provide refugia from parasitism by A. iole and that maximum protection occurs when the achenes are contiguous. The presence of refugia in strawberries limits the impact of augmentative biological control with A. iole, highlighting the need for its integration with other strategies to effectively suppress L. hesperus in strawberries.     

The Host Range ofEccritotarsus catarinensis(Heteroptera: Miridae), a Potential Agent for the Biological Control of Waterhyacinth (Eichhornia crassipes)

The host range ofEccritotarsus catarinensiswas determined using 33 plant species to assess the risk of using this insect, a native of South America, for the classical biological control of waterhyacinth (Eichhornia crassipes) in Australia and Papua New Guinea. The results, in conjunction with the results of Hillet al.(1999) who tested 67 species (mostly South African), strongly suggest thatE. catarinensisis restricted to the Pontederiaceae, a family of aquatic plants. All five species of Pontederiaceae in the Australian testing,E. crassipes, Pontederia cordata, Monochoria vaginalis, M. cyanea,andM. australasica,were suitable for insect development. Colonies persisted for at least four generations onE. crassipes, P. cordata,andM. vaginalis.Two-way choice and multiple-choice preference trials were conducted and discussed.E. catarinensisdid not exhibit a clear preference for waterhyacinth over other Pontederiaceae in these trials. Most oviposition occurred into the upper surface of the lamina during laboratory testing despite observations that the underside was preferred in the field. Although not considered suitable for release in Australia, this insect may be useful in other countries where more serious waterhyacinth problems occur and whereM. vaginalisis a serious weed, such as in Southeast Asia.     

Predation potential of three flatworm species (Platyhelminthes: Turbellaria) on mosquitoes (Diptera: Culicidae)

We conducted a field survey for flatworms to select species as potential biological control agents against Aedes aegypti and Culex pipiens (Diptera, Culicidae) breeding in artificial containers. Laboratory experiments were performed to determine the daily predation rate, differential predation on each mosquito larval instar, selective predation on either A. aegypti or C. pipiens, and predator tolerance to water from artificial containers. Girardia anceps (Tricladida, Paludicola, Dugesiidae), Mesostoma ehrenbergii and Bothromesostoma cf. evelinae (Rhabdocoela, Typhloplanoida, Typhloplanidae) were found in temporary puddles and permanent pools. In the laboratory, they killed between 52% and 100% of immature mosquitoes coexisting in the same habitat. No preference of flatworms for mosquito preys was detected. Predation rate was related to predator size and instar of preys. Girardia anceps and B. evelinae survived after a dry period and when re-flooding occurred, they laid eggs. Tolerance to water from artificial containers was highest in G. anceps and this species could be a suitable predator to reduce mosquito populations from artificial containers using an inoculative approach.     

Bt maize fed-prey mediated effect on fitness and digestive physiology of the ground predator Poecilus cupreus L. (Coleoptera: Carabidae)

We investigated the effects of a Bt maize hybrid on fitness and digestive physiology of the ground-dwelling predator Poecilus cupreus L., as compared with the near-isogenic hybrid. A tritrophic assay revealed that there was a great decline in the detection of Cry1Ab toxin through the trophic chain, the concentration of the toxin being 945, 349 and 37 ng g⁻¹ of fresh weight in Bt maize leaves, Spodoptera littoralis (Boisduval) larvae and P. cupreus larvae, respectively. Moreover, the toxin was only detected in 8% of the P. cupreus adults collected from fields growing Bt maize. Developmental time of both larvae and pupae of P. cupreus was not adversely affected by the Cry1Ab toxin via fed-prey. To elucidate potential detrimental effects due to a reduction in the quality of the prey, we assessed the digestive proteolytic activities of P. cupreus adults from a laboratory culture and insects collected in commercial Bt and non-Bt maize fields. Field-collected P. cupreus adults had higher proteolytic activities than those reared in the laboratory, whereas no significant differences were found between P. cupreus adults reared on Bt and non-Bt maize fed-S. littoralis or between P. cupreus adults collected in commercial Bt and non-Bt maize fields.     

The response of maize (Zea mays) to Azospirillum inoculation in various types of soils in the field

Application of a peat-based powder inoculant of Azospirillum brasilense, as well as a granular inoculant (each containing 0.5–1.0×10⁷ Azospirillum/g moist peat), in the seed furrows of Zea mays resulted in significantly increased yields (11 to 14%) in light soils at low rates of N fertilization. In general, there was no effect of inoculation on plant yields in heavier soils nor when N fertilization was high. Pre-emergence application of granular inoculant and inoculation associated with irrigation were more efficient in increasing yield than inoculation post-emergence or seed coating.E. Fallik is with ARO-The Volcani Centre, Department of Postharvest Science of Fresh Produce, Bet-Dagan 50250, Israel. Y. Okon is with The Hebrew University of Jerusalem, Faculty of Agriculture, Department of Plant Pathology and Microbiology, Rehovot 76100, Israel     

The effects of pollen consumption of transgenic Bt maize on the common swallowtail, Papilio machaon L. (Lepidoptera, Papilionidae)

Effects of exposure to maize pollen of event Bt176 (cultivar “Navares”) on the larvae of the European common swallowtail (Papilio machaon L.) were studied in the laboratory. First instar larvae were exposed to different pollen densities applied to leaf disks of Pastinaca sativa L. for 48 h. Pollen densities applied in this study were in the range recorded from the field. Larvae which were exposed to higher Bt maize pollen densities consumed more pollen and had a lower survival rate. The LD₅₀ with regard to larvae surviving to adulthood was 13.72 pollen grains consumed by first-instar larva. Uptake of Bt maize pollen led to a reduced plant consumption, to a lower body weight, and to a longer development time of larvae. Effects on pupal weight and duration of the pupal period were present but less pronounced and smaller than effects on larvae. Larvae having consumed Bt-maize pollen as first instars had a lower body weight as adult females and smaller forewings as adult males. We conclude that possible effects of Bt maize on European butterflies and moths must be evaluated more rigorously before Bt maize should be cultivated over large areas.