Neoleucinodes elegantalis (Lepidoptera: Crambidae): an organism invisible to the defences of tomato fruits

Insect–plant interactions involving species of the genus Solanum have been intensively studied, resulting in several articles on insect–plant interactions. However, the interactions between herbivores and the fruits of Solanum lycopersicum (tomato) are not well known. Neoleucinodes elegantalis is a borer that causes great yield losses in S. lycopersicum crops because of the direct damage that it causes to the fruits and the difficulty of controlling it. In the field, the outside of a tomato fruit infested with the larvae of N. elegantalis is visually similar to uninfested fruits. Even a minor injury by herbivores can elicit a defensive response. Due to the lack of studies on interactions between fruit borers and S. lycopersicum, our aim in this study was to determine the locations of S. lycopersicum fruit in which the N. elegantalis larvae prefer to feed. An evaluation of nutritional sources was done through histochemical and biochemical tests and the defensive response of the S. lycopersicum fruit to attack by N. elegantalis larvae was evaluated through the detection of protease inhibitors (PIs) and lipoxygenase (LOX) activity. Our results show that the columella region is preferred by the N. elegantalis larvae and that this region has a nutritional source. Furthermore, attack by N. elegantalis larvae in the columella does not induce a significant increase in lipoxygenase activity and PIs. Thus, our results provide a better understanding of the interaction between the larvae of N. elegantalis and S. lycopersicum fruits and a better understanding of the evolution of plant–herbivore interactions, with an emphasis on the choice of feeding location as a strategy to avoid plant defences.     

Stimuli affecting selection of oviposition sites by female peach twig borer, Anarsia lineatella Zeller (Lepidoptera: Gelechiidae)

In laboratory and field experiments, stimuli were tested that might affect oviposition decisions by female peach twig borer moths, Anarsia lineatella Zeller (Lepidoptera: Gelechiidae). When given a choice between immature green peach fruits, green mature peach fruits and soft-ripe peach fruits, the latter received the fewest eggs. Fuzzy halves of peach fruits received ten times more eggs then shaved hairless halves. Volatiles from both almond and peach shoots induced more oviposition by females than by control stimuli. Similarly, volatiles from immature green peach fruits, mature green or mature hard-ripe peach fruits induced more oviposition than their respective control stimuli. In a choice experiment, volatiles from immature peach fruit stimulated three times more oviposition than those from soft-ripe peach fruit. Discrimination against mature soft-ripe peach fruits as potential oviposition sites may lie in the phenology of A. lineatella and host peach fruits. Larval development to the pupal stage takes 15–27 days. Therefore, any eggs laid on a ripe fruit 14 days before it falls from the tree will not likely develop into adult insects because developing larvae will only reach third or fourth instar before the fruit is decomposed, and only first and second instar larvae can overwinter.     

Ant cues affect the oviposition behaviour of fruit flies (Diptera: Tephritidae) in Africa

Abstract. Although most studies on fruit fly oviposition behaviour focus on horizontal interactions with competitors and cues from host plants, vertical interactions with predators are poorly documented. The present study provides direct evidence indicating that the oviposition behaviour of the two main mango fruit fly species, Ceratitis cosyra (Walker) and Bactrocera invadens Drew‐Tsurata & White, is affected by secretions of the dominant arboreal ant Oecophylla longinoda (Latreille). When offered ant‐exposed and unexposed mangoes in the absence of the ants, both fly species are reluctant to land on ant‐exposed fruits and, when having landed, often take off quickly and fail to oviposit. The number of puparia collected from unexposed mangoes is approximately eight‐fold higher than from ant‐exposed ones. The results obtained from laboratory experiments and field observations confirm that adult fruit flies are more affected through repellence by ant cues than by direct predation. The use of cues by fruit flies in predator avoidance has implications for evolutionary ecology, behavioural ecology and chemical ecology.     

Adult response of the almond seed wasp,Eurytoma amygdali, to chemicals from its host and certain nonhosts

Females of the almond seed wasp,Eurytoma amygdali Enderlein (Hymenoptera, Eurytomidae), responded in an olfactometer positively to odours from almond flowers and unripe fruits, but not to almond leaf odours and odours from flowers and unripe fruits of certain other nonhostPrunus species. Males responded to none of these odours. Extracts of undamaged unripe almond fruits (using ethanol, methanol, acetone, hexane, dichloromethane, or petroleum ether) stimulated female aggregation on glass surfaces treated with these extracts; in addition, certain fruit extracts (ethanol, methanol, or acetone) stimulated oviposition. Extracts of undamaged almond leaves (ethanol, methanol, or acetone) and flowers (ethanol or methanol) also stimulated female aggregation and oviposition. Aggregation and oviposition in response to an ethanol extract of almond fruits was intense in females aged 5 to 14 days and from 12∶00 to 18∶00h (photophase between 06∶00 and 20∶00). Certain almond fruit (ethanol, methanol, acetone or hexane) and flower extracts (ethanol or methanol) also provoked female response in the olfactometer. The results strongly suggest that certain chemical stimuli emanating from parts of the almond tree play a major role in host selection and oviposition. Some of the extracts tested may be a good source for the isolation, identification and synthesis of compounds stimulating attraction, aggregation and oviposition in nature. *** DIRECT SUPPORT *** A3414024 00003     

An improved culturing method for opiine fruit fly parasitoids and its application to parasitoid monitoring in the field

Good culturing methods play an important role in the study of insect behavior and its application to pest management. Here, we describe and validate a new method for rearing the parasitoid wasp, Diachasmimorpha kraussii, which attacks some of the world's worst fruit fly pests and is an internationally used biological control agent. Our method differs from standard culturing approaches by presenting adult wasps with host‐infested artificial media within a “culturing bag,” which mimics a natural (fruit) oviposition substrate. In laboratory trials using wild collected D. kraussii, the culturing bag method was compared to the use of host‐infested nectarines, and a commonly used laboratory method of presenting host‐infested artificial media within Petri dishes. The culturing bag method proved to be a significant improvement on both methods, combining the advantages of high host survival in artificial media with parasitism levels that were the equivalent to those recorded using host‐infested fruits. In our field study, culturing bags infested with the Queensland fruit fly, Bactrocera tryoni, and hung in a mixed peach and nectarine orchard proved to be effective “artificial fruits” attracting wild D. kraussii for oviposition. Significantly more adult wasps were reared from the culturing bags compared to field collected fruits. This was shown to be due to higher fruit fly larval density in the bags, as similar percentage parasitism rates were found between the culturing bags and ripe fruits. We discuss how this cheap, time‐efficient method could be applied to collecting and monitoring wild D. kraussii populations in orchards, and assist in maintaining genetic variability in parasitoid laboratory cultures.     

Host-marking by female pepper weevils, Anthonomus eugenii

Pepper weevils, Anthonomus eugenii Cano (Coleoptera: Curculionidae), feed and oviposit in flower buds and small fruits of plants in the genus Capsicum, as well as several species of Solanum (Solanaceae). Females chew a small hole into the fruit, deposit a single egg within the cavity, and seal the hole with a clear anal secretion that hardens into an ‘oviposition plug’. Female oviposition behavior was studied in a series of small‐arena bioassays to determine whether previous oviposition in Jalapeño pepper fruit deterred subsequent oviposition and to determine what specific cues from an infested fruit influence female behavior. In choice and no‐choice tests, females preferred clean fruit to fruit that had received four eggs 24 h previously (i.e., infested fruit), whether the fruit was infested with conspecific eggs or their own eggs. Further bioassays demonstrated that the presence of female frass, or oviposition plugs alone, in the absence of eggs or any fruit damage, was sufficient to deter oviposition. In addition, females given the choice between an infested fruit with the oviposition plug removed or an unaltered infested fruit preferred the fruit with no plugs, even when eggs, frass, and feeding damage were still present. To determine whether females would avoid infested peppers under more natural conditions, we quantified oviposition on infested and uninfested sentinel pepper fruit within individually caged plants and on clean and infested plants caged together. Females consistently laid more eggs on clean fruit than on infested fruits and moved within and among pepper plants to search for more acceptable oviposition sites. We conclude that oviposition plugs, along with contaminated female, but not male, frass contain a deterrent that, in the absence of any other cue, is enough to alert a female that a patch is occupied.     

Virgin and recently mated males are equally able to achieve new matings in Neoleucinodes elegantalis

Lepidopteran male mating success is recognized to be directly related to physical and behavioural traits such as ability, vigour, activity and persistence in courtship. In the tomato fruit borer Neoleucinodes elegantalis Guenée, the mating system is known to be monogamic and therefore males' sexual investment is apparently low. The hypothesis that recently mated males have a remating probability equal to that of virgin males is tested. The impact of body size in remating success and the cost of remating are also analyzed. Mated males show as much propensity to remate as naïve ones. Copula duration and the time taken to copulate are similar in mated and virgin males. However, spermatophore size is not related to male size. The results suggest the ability of N. elegantalis males to remate within 24 h between mating events and their propensity to remate are not affected by copula investment. © 2013 The Royal Entomological Society     

Behavioral analysis of learning and memory in Anastrepha fraterculus

We evaluate the influence of prior exposure to artificial substrate for oviposition on learning and memory in the fruit fly Anastrepha fraterculus (Wiedemann) (Diptera: Tephritidae). Some females were previously exposed to artificial fruits made of water, agar, and blackberry [Rubus spec. (Rosaceae)] or guava [Psidium guajava L. (Myrtaceae)] pulp for 48 and 72 h. We also studied adult flies exposed for 72 h to essential oil of lemongrass [Cymbopogon citratus (DC) Stapf, Poaceae] and adult flies from larvae exposed to the oil. Control females were naive with respect to these experimental substrates. Prior experience with blackberry‐based artificial fruits resulted in an increase in the number of punctures and deposited eggs by A. fraterculus, and memory lasted for up to 72 h. On the other hand, fly behavior was independent of exposure to guava‐based substrate. Prior exposure of 1‐ or 15‐day‐old females to artificial substrate with lemongrass oil modified innate substrate selection behavior. The scent of lemongrass oil during the larval stage modified innate oviposition responses of adult A. fraterculus. The study shows that A. fraterculus females are able to learn and retain information through chemical stimuli released by both host (blackberry and guava) and non‐host (lemongrass) species, and they can use olfactory memory obtained during the larval stage to select oviposition sites.     

Phytophagous insect oviposition shifts in response to probability of flower abortion owing to the presence of basal fruits

Phytophagous insects use a wide range of indicators or associated cues to avoid laying eggs in sites where offspring survival is low. For insects that lay eggs in flowers, these unsuitable sites may be created by the host plant's resource allocation to flowers. In the sequentially flowering host plant, Yucca glauca, late‐opening distal flowers are more likely to be aborted in the presence of already‐initiated basal fruits because they are strong resource sinks. If flowers are aborted, all eggs of the phytophagous insect, Tegeticula yuccasella, within the flower die. We used the phytophagous insect T. yuccasella that lays eggs in and pollinates host plant Y. glauca flowers to test the hypothesis that phytophagous insect females are less likely to invest eggs in host plant flowers if basal fruits are present because they are more likely to be aborted. We also investigated potential predictors of arrival of T. yuccasella at inflorescences at the onset of flowering. These factors may influence a phytophagous insect's decisions to select oviposition sites. We carried out a behavioral experiment using wild‐caught T. yuccasella females on manipulated inflorescences with distal flowers with basal fruits and without fruits. As potential predictors of T. yuccasella arriving at inflorescences, we used floral display size and day of onset of flowering. In support of our hypothesis, our experimental results showed that T. yuccasella was significantly less likely to oviposit in distal flowers on inflorescences with basal fruits. We also found that T. yuccasella arrival was higher at inflorescences with larger floral display size and earlier in the flowering season. These findings uncover a novel indicator of unsuitable oviposition sites—the presence of basal fruits, that phytophagous insects use to make oviposition decisions. Further, our study contributes to the growing body of evidence that shows that females prefer sites that increase the probability of survival of their offspring.     

Mechanism and effectiveness of safflower oil against female Queensland fruit fly Bactrocera tryoni

Queensland fruit fly, Bactrocera tryoni (Froggatt) (Diptera: Tephritidae), infests many horticultural fruit crops in the eastern part of Australia. Farmers usually apply synthetic insecticides to control this pest. Little is known on the use of plant products especially vegetable oils for fruit fly control although they are considered to be safer than synthetic insecticides. In this study, safflower oil was investigated for its mechanism and effectiveness against female B. tryoni. In a laboratory test, safflower oil treatments (2.5 and 5.0 ml l^?1) reduced the number of fly punctures on treated artificial fruits, no matter whether pre‐punctures were present or absent. Safflower oil treatments also reduced the number of fly landings and eggs laid, but only when the treated artificial fruits were without pre‐punctures. These results confirmed that safflower oil is active against female B. tryoni mainly by preventing this fruit fly from making oviposition punctures, not by discouraging them from depositing eggs or by repelling them. The slippery nature of safflower oil is considered to be responsible for a reduction in the susceptibility of artificial fruit to fruit fly punctures. Further investigation using fruit‐bearing tomato plants (a no‐choice test) in a glasshouse situation revealed that safflower oil application at concentrations of 10 and 15 ml l^?1 reduced the number of oviposition punctures but failed to reduce the number of eggs laid. To increase efficacy of safflower oil under field conditions, multiple tools may be needed to reduce fruit fly populations and oviposition behaviour, such as the addition of trap‐crops, provision of artificial oviposition sites, or mixing the insecticides with the oil.     

Sex‐biased oviposition by a nursery pollinator on a gynodioecious host plant: Implications for breeding system evolution and evolution of mutualism

Dioecy, a breeding system where individual plants are exclusively male or female, has evolved repeatedly. Extensive theory describes when dioecy should arise from hermaphroditism, frequently through gynodioecy, where females and hermaphrodites coexist, and when gynodioecy should be stable. Both pollinators and herbivores often prefer the pollen‐bearing sex, with sex‐specific fitness effects that can affect breeding system evolution. Nursery pollination, where adult insects pollinate flowers but their larvae feed on plant reproductive tissues, is a model for understanding mutualism evolution but could also yield insights into plant breeding system evolution. We studied a recently established nursery pollination interaction between native Hadena ectypa moths and introduced gynodioecious Silene vulgaris plants in North America to assess whether oviposition was biased toward females or hermaphrodites, which traits were associated with oviposition, and the effect of oviposition on host plant fitness. Oviposition was hermaphrodite‐biased and associated with deeper flowers and more stems. Sexual dimorphism in flower depth, a trait also associated with oviposition on the native host plant (Silene stellata), explained the hermaphrodite bias. Egg‐receiving plants experienced more fruit predation than plants that received no eggs, but relatively few fruits were lost, and egg receipt did not significantly alter total fruit production at the plant level. Oviposition did not enhance pollination; egg‐receiving flowers usually failed to expand and produce seeds. Together, our results suggest that H. ectypa oviposition does not exert a large fitness cost on host plants, sex‐biased interactions can emerge from preferences developed on a hermaphroditic host species, and new nursery pollination interactions can arise as negative or neutral rather than as mutualistic for the plant.     

Are citrus species favorable hosts for the Mediterranean fruit fly? A demographic perspective

We studied, under laboratory conditions, demographic parameters of adult Mediterranean fruit flies, Ceratitis capitata (Wiedemann) (Diptera: Tephritidae) (medfly), obtained from three sweet orange varieties, lemon, and bitter oranges. These data were combined with immature developmental rates and survival on the same hosts to estimate host‐specific population parameters. Pairs of newly emerged adults from each citrus variety were held individually in transparent plastic cages, and females were allowed to oviposit in either red domes (artificial, pre‐punctured plastic oviposition devices), or intact, whole citrus fruits. We found strong effects of larval host (citrus fruits) on adult longevity and fecundity. In all five citrus varieties, females did not manage to deposit eggs into fruit pulp. The proportion of eggs laid in either the flavedo or albedo area of the fruit peel differed depending on the citrus variety. In all cases except bitter oranges, females oviposited fewer eggs in citrus fruits than in the artificial oviposition substrates, suggesting that most citrus fruits cause a significant reduction in the reproductive potential of medflies. Negative correlations were found between fecundity and (a) the density of oil glands, and (b) the amount of essential oils in the flavedo area of citrus fruits. There was no correlation between fecundity and other fruit physical characteristics, such as resistance of fruit peel to pressure and thickness of the flavedo. Apparently, resistance of citrus fruits to medfly infestation is directly related to citrus essential oils. The intrinsic rate of increase (r) was higher in bitter oranges than in the three sweet orange varieties tested. A negative r was estimated for flies that developed and oviposited in lemons, indicating a tendency for population decrease in this host. The suitability of citrus fruits for medfly development and the practical implications of our findings for management of medflies in citrus orchards are discussed.     

No effect of larval experience on adult host preferences in Polygonia c‐album (Lepidoptera: Nymphalidae): on the persistence of Hopkins’ host selection principle

Abstract 1. The possible effect of juvenile imprinting or ‘chemical legacy’ on the subsequent oviposition – often called the ‘Hopkins’ host selection principle’– has been a controversial but recurrent theme in the literature on host‐plant preference. While it appears possible in principle, experimental support for the hypothesis is equivocal. The present study points out that it is also important to consider its theoretical implications, and asks under what circumstances, if any, it should be favoured by natural selection. 2. Following this reasoning, it is predicted that host preference in the polyphagous butterfly Polygonia c‐album L. (Lepidoptera, Nymphalidae) should not be influenced by larval environment. This was tested by rearing larvae on three natural host plants: the high‐ranked Urtica dioica and the medium‐ranked Salix cinerea and Ribes uva‐crispa, and exposing the naive females to oviposition choices involving the same set of plants. 3. It was found that larval host plant had no effect on oviposition decisions of the adult female. Hence, the Hopkins’ host selection principle does not seem to be applicable in this species. 4. Based on recent insights on how accuracy of environmental versus genetic information should affect the control of developmental switches, the conditions that could favour the use of juvenile cues in oviposition decisions are discussed. Although the Hopkins’ host selection hypothesis cannot be completely ruled out, we argue that the circumstances required for it to be adaptive are so specific that it should not be invoked as a general hypothesis for host selection in plant‐feeding insects.     

Clutch size in frugivorous insects as a function of host firmness: the case of the tephritid fly Anastrepha ludens

Abstract. 1. Optimal clutch size theory predicts that individuals will oviposit the number of eggs that increases their fitness. In Anastrepha ludens Loew (Diptera: Tephritidae), females oviposit larger clutches in unripe (firm) fruits than in ripe (soft) fruits. The following hypotheses were tested: (1) Using fruit firmness as an indicator of fruit quality, A. ludens females vary the number of eggs per clutch every time they reach an oviposition decision. (2) Maximising offspring survival with respect to either unripe or ripe fruit requires placing large clutches in firm fruit and smaller clutches in soft fruit. 2. Agar spheres were used as artificial hosts. Three agar concentrations resulted in three degrees of firmness. Mango fruits Mangifera indica L. served as natural hosts. Ripe and unripe fruits were used to test soft and firm host conditions respectively. Females laid significantly larger clutches in the firmer artificial hosts than in the softer hosts. They also laid significantly more eggs in artificial hosts without sugar than in hosts with sugar. Firm (unripe) mangoes also received significantly larger clutches than soft (ripe) mangoes. 3. When an individual female was first presented with a firm artificial host, it laid a large clutch. If subsequently offered a soft host, the female laid a significantly smaller clutch. Finally, if again offered a firm host, clutch size was increased significantly. 4. Possible trade‐offs in offspring fitness were explored in ripe and unripe mangoes by measuring offspring egg‐to‐adult survival, pupal weight, mean adult longevity, and fecundity. Despite the fact that larval survival was greater in soft fruit than in firm fruit, parameters such as pupal weight, mean longevity, and fecundity of adults stemming from both fruit types did not differ significantly. 5. A probable trade‐off between high offspring mortality caused by host unsuitability and low offspring and adult mortality caused by parasitism and predation is discussed as the reason for the exploitation of sub‐optimal hosts.     

Combination of edible vegetable oil and artificial fruit to reduce Bactrocera dorsalis oviposition in chilli fruits

Bactrocera dorsalis (Hendel) is a major pest of a wide variety of fruits and vegetables. This study aimed to evaluate the potency of combining edible vegetable oil application and artificial fruit provision to reduce the oviposition of B. dorsalis in chilli fruits. Experiments were conducted in laboratory using a 20‐L plastic container provided with chilli fruits and in semi field using a fruit‐bearing chilli plant caged with insect screen. The laboratory test revealed that the combination of coconut oil application and artificial fruit provision significantly reduced fruit fly visits, eggs laid and the number of infested chilli fruits no matter when the chilli fruits were without prepuncture or with prepuncture. Further study using a caged chilli plant also found that this combination had significant effects on fruit fly visits and infestation in chilli fruits. These results provide an indication that coconut oil and artificial fruit can work together to reduce fruit fly attacks on chilli fruits. Combining the use of coconut oil and artificial fruit is likely to create an integrated behavioural manipulation (push and pull) of female B. dorsalis that lead to a much lower fruit fly infestation in chilli fruits.     

Potential host fruits for Drosophila suzukii: olfactory and oviposition preferences and suitability for development

Drosophila suzukii (Matsumura) (Diptera: Drosophilidae), the spotted wing drosophila, is a pest endemic to Southeast Asia that invaded the Americas and Europe in 2008. In contrast to most of its congeners, D. suzukii possesses a serrated ovipositor that allows it to lay eggs in unwounded commercial fruits, resulting in severe revenue losses for the industry. The purpose of this study was to determine the susceptibility of known host fruits, including cherry, strawberry, blueberry, and grape, and potential host fruits, such as banana and apple, to attack by D. suzukii. Based on the responses to volatile cues offered in a six‐choice olfactometer, the preference of female D. suzukii was ranked in the following order: strawberry = cherry > banana = apple = blueberry = grape, but in no‐choice and choice oviposition tests, the preferences were ranked as follows: cherry > strawberry = blueberry > grape = banana > apple. Furthermore, we reconfirmed that D. suzukii mainly targets rotten fruit for feeding and ripe fruit for oviposition, and females preferred fruits with intensive mechanical damage. Based on developmental parameters, apple was the least suitable host. This study has implications for the control of D. suzukii, especially in mixed fruit orchards, by providing a promising avenue for exploiting behaviour‐based control tools and emphasizing the importance of phenology in host fruit susceptibility.     

Diving Into The Water: Cues Related to the Decision‐Making by an Egg Parasitoid Attacking Underwater Hosts

Although adult parasitoids spend a majority of their lives above ground, females of several species must search for their host in the water or on the soil. Adult parasitoids above ground can use a variety of sensory cues to detect their hosts from a distance. However, their sensory cues can be impaired from volatile chemicals, and their visual stimuli can be decreased while submerging or burrowing in the water of soil during their search for their hosts. Searching underwater or underground would incur high foraging costs, that is, time and energy consumption and increase risk of drowning. Therefore, to reduce such costs and increase searching efficiency, the decision on where to start submerging or burrowing for attacking hosts is important for parasitoids. Furthermore, there are no studies that have examined the cues of submerging or burrowing parasitoids on their exploit for the decision to attack their hosts. We have examined the cues used by the egg parasitoid Tiphodytes gerriphagus attacking underwater hosts. We compared the searching behaviors of T. gerriphagus among four oviposition site conditions. The four sites investigated were oviposition site with both host adult chemical residues and presence of eggs, with only the presence of eggs, with only the host adult chemical residues, and without any cue. Our results indicated that T. gerriphagus more frequently contacted and submerged at oviposition sites with the adult residues rather than at oviposition sites without them. Nonetheless, the presence of underwater host eggs did not affect the host‐searching behavior. This suggests that T. gerriphagus decided to submerge at the oviposition site in response to the adult residues. Furthermore, our observation also suggested that T. gerriphagus has already detected that the adult residues might be volatile before contacting the oviposition site. Finally, we will discuss the exploitation patterns of host‐searching cue by parasitoids that need to submerge from the context of its reliability and detectability problems.     

Specificity of systemically released rice stem volatiles on egg parasitoid,Trichogramma japonicum Ashmead behaviour

The yellow stem borer, Scirpophaga incertulas Walker (YSB), infested rice plants emit chemicals through the surface of their infested stems. These induce attractant activity and cause arrestment responses and ovipositional stimulation in its egg parasitoid, Trichogramma japonicum Ashmead. Laboratory experiments on short‐range host searching and oviposition were performed to assess the how these crude stem extracts and their fractions influence the biological control efficiency of Trichogramma. The activity of these chemicals as long‐range attractants was confirmed through wind tunnel bioassays. Stem borer‐infested plant extracts had enhanced the parasitization rate of T. japonicum, whereas host eggs treated with the extract from undamaged stems or solvent‐treated control failed to evoke changes in the parasitoid’s behaviour. A preliminary GC‐MASS analysis indicated the presence of several hydrocarbon compounds. The analysis also revealed qualitative and quantitative differences between the chemical profiles of the infested and non‐infested plants. We hypothesized that herbivore‐induced plant chemicals are released through the stem surfaces and attract T. japonicum, even over long distances. These cues elicit parasitoid arrestment on pest‐damaged plants and subsequently lead to the successful parasitization of the stem borer.     

Host species and vegetable fruit suitability and preference by the parasitoid wasp Fopius arisanus

Parasitoids that oviposit in a concealed host inside a plant part need to be able to find both the plant and the host. Egg parasitoids of fruit‐infesting Tephritidae need to assess the oviposition site based both on the host egg and the infested fruit. Infestation by Tephritidae fruit flies threatens fruit and vegetable production. Management methods have been implemented including biological control, using Fopius arisanus Sonan (Hymenoptera: Braconidae). The parasitism by F. arisanus in three Tephritidae flies in vegetable fruits was investigated. Laboratory assays were conducted to assess the parasitoid's preference and survival. Zucchini, sweet pepper, and tomato were artificially infested with eggs of Bactrocera dorsalis Hendel, Ceratitis capitata Wiedemann, and Ceratitis cosyra Walker (all Diptera: Tephritidae), then exposed to mated naïve F. arisanus females in a 20:1 egg:parasitoid ratio. Parasitoid behavioral activities (resting, antennating, probing, ovipositing) were observed on the infested fruits. Parasitism rate was determined by dissection of fruit fly eggs under a stereomicroscope. Behavioral activities of F. arisanus differed between all the fruits when infested with B. dorsalis or C. cosyra eggs but differed only between some of the fruits when infested with C. capitata. Fopius arisanus preferred B. dorsalis over C. capitata and C. cosyra, with a parasitism rate 2× higher on B. dorsalis compared to the Ceratitis species. Preference for fruits was dependent on the infesting fruit fly. The emergence of F. arisanus was higher with B. dorsalis than with Ceratitis spp. Although B. dorsalis completed its development earlier than Ceratitis spp., host fly species did not affect the developmental time of F. arisanus. We discuss the significance of F. arisanus preference in relation to naturally occurring Tephritidae infestations. We also discuss whether some fruits might constitute a refuge for Tephritidae flies and whether this will affect the current biological control efforts against B. dorsalis.     

Do plant cues influence the oviposition behavior of Japanese beetles?

A bioassay arena was developed to test the response of the Japanese beetle, Popillia japonica Newman (Coleoptera: Scarabaeidae), to various plant‐derived factors that may influence the selection of oviposition sites. In choice experiments with natural and artificial plant cues, females preferred to lay eggs in ryegrass rather than in artificial resources. Artificial grass stems received more eggs on average than bare ground, indicating the role of vertical objects on the soil surface as oviposition cues. Popillia japonica females were able to discriminate between the quality and quantity of the artificial stems, as more eggs were laid in soil blocks that had larger diameter stems or a higher number of stems per soil block. Beetles were capable of evaluating plant characteristics on the soil surface and adjusted their investment accordingly; more eggs were laid in resources that were chosen more frequently. Observations of females in choice arenas revealed how surface cues influence digging behavior and the time spent under the soil surface. The number of digging events was not significantly different among the three treatments with surface cues (ryegrass, grass roots, and artificial grass), but beetles spent significantly more time in the soil under ryegrass than any of the other treatments. These findings suggest that oviposition by P. japonica is selective and is influenced by plant‐derived cues evaluated before and after digging into the soil.