Plant preference in relation to life history traits in the zoophytophagous predator Dicyphus hesperus

Dicyphus hesperus Knight (Heteroptera: Miridae) is an omnivorous predator used to control pests of greenhouse vegetables. Plant preferences and life history traits were studied using nine plant species: Lycopersicon esculentum Mill. (Solanaceae), Capsicum annuum L. (Solanaceae), Verbascum thapsus L. (Scrophulariaceae), Nepeta cataria L. (Lamiaceae), Stachys albotomentosa (Lamiaceae), Nicotiana tabacum L. (Solanaceae), Vicia sativa L. (Fabaceae), Zea mays L. (Gramineae), and Chrysanthemum coronarium L. (Asteraceae). Plants were selected from among potential target crops, natural hosts, plants used for mass rearing, and plants on which D. hesperus has not been reported. Plant preference was measured by multi‐choice host plant selection and oviposition assays. Development and reproduction were measured on each of the plant species on both a plant diet alone and on a plant diet supplemented with Ephestia kuehniella Zeller (Lepidoptera: Pyralidae) eggs. Dicyphus hesperus females and nymphs expressed a preference for some plants over others. Plant preference ranged from low preference plants, such as Z. mays, V. sativa, C. coronarium, and C. annuum, to high preference plants such as V. thapsus, N. tabacum, and S. albotomentosa. When E. kuehniella eggs were supplied, there were few differences in the development time and fecundity of D. hesperus among plants, with the exception of corn and broad bean, where fecundity was lower. On a plant diet alone, nymphs were able to complete their development on V. thapsus, C. annuum, and N. cataria. However, mortality and development time were much lower on V. thapsus than on C. annuum and N. cataria. On most of the plant species D. hesperus did not lay any eggs when fed on a plant diet alone. On V. thapsus, females laid a few eggs and lived longer than when fed on prey. Dicyphus hesperus females tended to prefer host plants on which nymph survival without prey was greatest.     

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.     

Preference and consumption of Macrolophus pygmaeus preying on mixed instar assemblages of Myzus persicae

This study examines the effects of changes in the prey frequency and abundance on prey selection among the four instars of Myzus persicae by the predator Macrolophus pygmaeus under laboratory conditions. The central hypothesis was that M. pygmaeus will become more selective as prey density increases. It was also observed that M. pygmaeus can occasionally abandon a prey item that had already been killed (non-consumptive prey mortality). It was assumed that the frequency of this behavior would increase with the prey size and prey density. For these purposes prey selection was evaluated by simultaneously presenting all instars of M. persicae to the predator in equal proportions and at increasing densities. M. pygmaeus showed a higher predation rate and a higher preference for smaller prey instars at all prey densities. However, if the predation rate by the predator is expressed in terms of biomass consumed, then biomass gain was higher when feeding on the larger instars of M. persicae. The prey selectivity was indicated by the total prey mortality (consumptive plus non-consumptive prey mortality) as well as by the non-consumptive prey mortality, was associated with relatively high prey densities, depending on the prey instar. Therefore, we argued that the predatory impact of M. pygmaeus on the various instars of the aphid depends not only on prey traits but also on their relative abundance in a patch. Observed decreases in biomass gain from larger prey were likely the result of high prey availability at densities before saturation, which might have caused confusion in the predator’s prey selection.     

Prey‐mediated changes in the selectivity of the predator Macrolophus pygmaeus (Heteroptera: Miridae)

When foraging in communities with mixed prey, generalist predators may be confronted with prey species that differ in quality, size and mobility and interact with one another. To examine prey selection, predation by Macrolophus pygmaeus (Heteroptera: Miridae) was recorded by providing a diet of either one or two prey species of Myzus persicae (third‐instar nymphs), Aphis gossypii (fourth‐instar nymphs), Trialeurodes vaporariorum (third‐instar nymphs) and Ephestia kuehniella (eggs). In the experiments, prey mobility, prey quality and prey biomass were considered. The biomass consumed by the predator was dependent on the combination of prey species and the quantity of biomass offered. In choice experiments with diets mixed of two prey species at equal densities, the predation to A. gossypii was significantly reduced in the presence of E. kuehniella but the rate of consumption of M. persicae, T. vaporariorum and E.kuehniella was not significantly affected by the coexistence of any other species in the mixed prey diet. When equal amounts of biomass from two prey species were provided in combination, the total consumed biomass was significantly reduced in the mixed prey diets composed of E. kuehniella eggs and aphid nymphs. Thus, under the mixed‐prey situation, prey selection by predators may be affected by interactions among prey species differing in traits such as quality, mobility and size.     

Coexistence of ecologically similar colonising species III. Drosophila aldrichi and D. buzzatii: larval performance on,and adult preference for,three Opuntia cactus species

Two Drosophila species, D. buzzatti and D. aldrichi, coexist on several species of Opuntia cacti in Australia, primarily on O. tomentosa and O. streptacantha in the northern part of the cactus distribution, and on O. stricta in the south. Thorax length of field-collected adults was less, and the variance in length greater, than that for flies reared on simulated rots in the laboratory, indicating that these species are affected by crowding in nature. A larval performance index, measured on simulated cactus rots at low, moderate and high densities in single-species cultures, and at moderate and high densities in mixed-species cultures, was used to compare the relative intensity of intra- and interspecific competition at the same total larval density per 5 g necrotic cactus. Larval performance of both fly species was greatest on O. streptacantha, intermediate on O. tomentosa, and least on O. stricta in both single-species and mixed-species cultures. On O. stricta, the performances of D. aldrichi and D. buzzatii were not different when in single-species cultures, but that of D. aldrichi decreased significantly in mixed-species cultures. On the other two cactus species, the performances of D. aldrichi and D. buzzattii were not different in mixed-species cultures. The order of preferences by adult females for the cacti differed from that for larval performance, with females of both species prefering O. stricta. Analysis of microbial numbers growing on the cacti showed little difference among cacti at the rot age used for testing adult preference, but later growth was greater on O. tomentosa and O. streptacantha, the cacti that best supported larvae. Differential larval performance on O. stricta may contribute to the rare presence of D. aldrichi in the southern part of the cactus distribution, while the superior quality of O. tomentosa and O. streptacantha (larger rot size and higher microbial concentration) may reduce competition and facilitate cocxistence of the fly species in the north.     

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 role of plant chemical cues in determining host preference in the generalist aphid parasitoid Aphidius colemani

The host preference behaviour of the generalist aphid parasitoid Aphidius colemaniwas investigated using a Y-tube olfactometer. Female A. colemanishowed a preference for the host-plant complex on which they had been reared, even though the same aphid host was involved, demonstrating a host plant preference. This preference was not evident when the parasitoids were dissected from their mummies prior to adult emergence. Host plant preference exhibited during host selection appeared to be induced by chemical cues encountered on the mummy case at the time of emergence, but preferences could be changed by subsequent foraging experiences. It is concluded that plant chemical cues play a major role in determining initial preferences through a process of emergence conditioning but that learning processes, involving cues encountered during oviposition in or contact with the host, can modify these initial preferences.     

Nymphal Development and Survival of Macrolophus pygmaeus Rambur (Hemiptera: Miridae) on Two Eggplant Varieties as Affected by Temperature and Presence/Absence of Prey

Nymphal development of the predator Macrolophus pygmaeus Rambur (Hemiptera: Miridae) was investigated on two eggplant varieties, Bonica and Black Beauty, in an attempt to identify the possible role that plant variety plays in the development and survival of the predator and to determine whether these biological characteristics are influenced by temperature and prey. The development of nymphs was studied in the presence and absence of the prey, Myzus persicae (Sulzer), at 15, 20, 25, 30, and 35°C, 65 ± 5% RH, and 16:8 h (L:D) photoperiod. Significant differences in the periods of nymphal development were evident in the two varieties at 15°C when M. persicae was offered as prey, and at 15 and 30°C, when there was no prey, significantly shorter periods of development were recorded on Bonica than on Black Beauty. Mortality rates of the nymphs were similar in the presence of prey on both varieties but, in the absence of prey, higher mortality rates were recorded on Black Beauty than on Bonica. In both presence and absence of prey, at 35°C, a small number of nymphs reached adulthood on Bonica, whereas no nymphs did so on Black Beauty. Therefore, the less suitable variety, Black Beauty, had a significant effect on the development and survival of nymphs of this predator, mainly in the absence of prey and at lower and higher temperatures. It is concluded that the selection of a suitable variety for the development and survival of M. pygmaeus, particularly in the absence of prey, could improve the efficiency of a biological control program in which this predator is going to be used. This is of particular importance for its establishment and effectiveness at the beginning of the growing season when temperature is relatively low and the prey is absent or scarce, as well as in summer when temperatures are high enough (around 30°C or even higher).     

Host suitability and preference studies of Trichogramma cordubensis (Hymenoptera: Trichogrammatidae)

Studies of host suitability and preferences of Trichogramma cordubensis Vargas and Cabello (Hymenoptera: Trichogrammatidae) were performed with eggs of six Lepidoptera (Noctuidae) species: Thysanoplusia orichalcea Fabricius, Peridroma saucia (Hübner), Xestia c-nigrum L., Phlogophora meticulosa (L.), Noctua pronuba (L.), and N. atlantica (Warren). Host suitability was studied by analysing separately the effects of the attacked host species and the influence of the rearing host species on different biological parameters of T. cordubensis. Host preference was analysed by offering eggs of two host species simultaneously to a single female wasp without previous oviposition experience (dual-choice tests). Results show that P. saucia, followed by P. meticulosa were the least suitable hosts for T. cordubensis, since on these species the preimaginal development of the parasitoids was significantly longer and, the number of parasitized eggs as well the number of offspring per female were significantly lower. Contrarily, T. cordubensis parasitized at a higher rate the eggs of the endemic non-target species, N. atlantica. Dual choice tests showed that the option of the first host to be accepted by the wasp was random; however, the mean number of parasitized eggs differed significantly when two host species were offered simultaneously to T. cordubensis, always being the host species with heavier eggs the most parasitized.     

A comparison of methodologies for the assessment of host preference of the gregarious egg parasitoid Trichogramma platneri

The innate preference of Trichogramma platneri for the eggs of six host species (Chrysoperla carnea (Stephens), Cydia pomonella (L.), Ephestia kuehniella (Zeller), Helicoverpa zea (Boddie), Manduca sexta (L.), and Sitotroga cerealella (Olivier)) was evaluated as the first host accepted by an individual female parasitoid when eggs were presented simultaneously. Selective exploitation of the same hosts by T. platneri was evaluated in no-choice, paired-choice, and multiple-choice tests, using number of parasitoids emerged, proportion of female offspring, and proportion of time spent on host eggs as different measures of preference. T. platneri showed a strong innate preference for C. pomonella and M. sexta. H. zea and M. sexta were the most preferred hosts and S. cerealella the least preferred, in the no-choice and choice tests. The number of progeny emerged and proportion of female offspring were equally suitable measures of host preference for T. platneri. Although no-choice and choice tests provided very similar preference ranking for T. platneri, a polyphagous species, the no-choice tests appeared poorer at separating hosts that were close in rank and multiple-choice tests were considered likely to be more realistic for more specialized control agents.     

The food requirements of Blepharidopterus angulatus (Heteroptera: Miridae) as a predator of the lime aphid, Eucallipterus tiliae

The weight of lime aphids consumed by B. angulatus increases at an increasing rate during nymphal development, with the fifth instar contributing 50% of the total consumption. Males and females reach different adult weights, but show no difference in food consumption. The efficiency of conversion of aphid food into body tissues diminishes from the third instar onwards. Females continue to oviposit for 5 weeks at least, laying on average just over one egg per day. The daily food requirements of ovipositing adult females increase as they get older, being more than twice as great as those of fifth-instar nymphs. Nymphs can tolerate a less than optimal food supply, and in the early instars they can compensate for an inadequate diet by converting food into body tissues with increased efficiency. Teneral adult weight is, however, proportional to the weight of food consumed during the fifth instar. B. angulatus can develop successfully on parasitized aphids and can utilise honeydew to prolong survival and, to a limited degree, to increase in weight. Leaf tissue has no significant value as a source of food.

---

Résumé Les besoins alimentaires de B. angulatus ont été étudiés au laboratoire à une température de 14 degrés.Quand B. angulatus est largement approvisionné avec des pucerons du tilleul, sa consommation de nourriture s'accroît de plus en plus au cours du développement, de même que son poids, de sorte que le 5ème stade larvaire absorbe un peu plus de 50% du poids total de pucerons consommés pendant toute la durée du développement larvaire. Ce 5ème stade larvaire est plus long que le 4ème, lequel est également plus long que chacun des trois premiers stades. La consommation journalière est moindre au début et à la fin de chaque stade, en particulier dans les derniers stades.Le prédateur consomme jusqu'à 90% du poids du corps de la proie. Quand les pucerons lui sont donnés en excès, la larve du 5ème stade de B. angulatus tend à tuer plus de proies qu'elle n'en consomme, ce qui sans doute est dû à la stimulation provoquée par la proie.Le rendement de croissance (efficience de la transformation du poids d'aphides absorbés en poids du corps du prédateur) diminue à partir du 3ème stade larvaire (de 46% pour le ler stade à 19% chez les adultes femelles). Au 5ème stade larvaire le rendement de croissance des mâles est significativement plus faible que celui des femelles, de sorte que les mâles sont plus légers que les femelles à l'état de maturité, bien que les deux sexes consomment le même poids de pucerons.Les femelles adultes commencent à pondre environ deux semaines après la mue imaginale et chacune dépose en moyenne 44 ufs, environ 1, 2 par jour. Les besoins alimentaires des femelles adultes en cours de ponte s'accroissent avec leur âge; leurs besoins journaliers en pucerons sont plus de deux fois aussi grands que ceux des larves du 5ème stade.Les larves peuvent supporter un apport en nourriture réduit par rapport à l'optimum.La résistance à la restriction alimentaire est plus grande au 3ème stade larvaire qu'aux ler et 5ème stades. Le ler et le 3ème stade larvaire peuvent compenser une réduction de l'apport alimentaire, par un meilleur rendement de croissance, ce que ne peuvent faire les larves du 5ème stade. B. angulatus peut se développer de façon satisfaisante en se nourrissant de pucerons parasités et momifiés. Il peut aussi utiliser le miellat en cas de disette ce qui lui permet d'accomplir un développement partiel, d'un stade au suivant, mais pas au-delà. En moyenne B. angulatus ne survit pas plus longtemps quand on ne lui offre que de l'eau ou des feuilles de tilleul, l'insecte peut en effet piquer celles-ci, pour lutter contre la dessication.

     

Evaluation of cold-stored eggs of Dolycoris baccarum (Hemiptera: Pentatomidae) for parasitization by Trissolcus nigripedius (Hymenoptera: Scelionidae)

Trissolcus nigripedius Nakagawa (Hymenoptera: Scelionidae) is an egg parasitoid of Dolycoris baccarum L. (Hemiptera: Pentatomidae), a polyphagous insect pest of many crops including soybean. As a method for mass-rearing to augment the parasitoid, cold storage of host eggs were evaluated in the laboratory. After 0 (control), 8, 20, 60, 90, and 120 days of refrigeration, host eggs were given to adult female T. nigripedius. Host acceptance behaviors of the parasitoid, categorized as drumming, oviposition, and marking, on the refrigerated eggs and biological attributes of offspring were assessed. Most of the attributes examined were affected by the refrigeration of host eggs. But host eggs could be refrigerated for up to two months without significant change in emergence rate and sex ratio and with 90% of parasitism. In addition, the second generation of the parasitoid was not negatively affected at all. However, frozen eggs of D. baccarum can not be used for rearing the parasitoid since parasitism rate decreased to 44% on host eggs frozen for 8 days. Refrigeration of D. baccarum eggs could be useful for mass-rearing and augmentation of T. nigripedius to control D. baccarum without reduction in the quality of parasitoid’s progeny. Furthermore, refrigerated eggs could be supplemented in the field to boost the population of T. nigripedius since immature D. baccarum can not hatch after 20 days of refrigeration.     

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.     

Semi-field demographic performance of the invasive planthopper,Orosanga japonica (Hemiptera: Ricaniidae) on two host plants

Orosanga japonica Melichar (Hemiptera: Ricaniidae) is an invasive polyphagous pest in Iran. The planthopper damaged host plants by sap-sucking and egg laying on new twigs. This study aimed to determine the life table parameters of O. japonica on Rubus ulmifolius Schoot (elm leaf blackberry) and Melia azedarach L. (chinaberry) under field conditions in Rudsar (North of Iran) during 2019–2020. The collected life history data were analyzed based on age-stage, two-sex life table theory. The results showed that the incubation period of O. japonica was too long (≈ 270 days) on both host plants. The nymphs emerged from mid-May 2020. The planthopper had five nymphal stages under field conditions. The nymphal duration was 41.39 ± 0.56 days and 38.13 ± 0.62 days on R. ulmifolius and M. azedarach, respectively. The total preadult survival rates were 53.2% and 51.7% on R. ulmifolius and M. azedarach, respectively. Based on the results, a significant shorter total developmental time was observed on M. azedarach. When adults emerged in late July, they laid eggs after 26.05 days and 26.75 days on R. ulmifolius and M. azedarach, respectively. The fecundity on M. azedarach (131.69 egg/female) was significantly higher than that on R. ulmifolius. However, the life table parameters were all not significantly different on the two host plants. The intrinsic rate of increase (r) were 0.0097 ± 0.0005 day⁻¹ and 0.0105 ± 0.0006 day⁻¹ on R. ulmifolius and M. azedarach, respectively. Generally, these findings could be helpful to establish an efficient management strategy for this exotic pest.     

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.     

Production of Anagrus epos Girault (Hymenoptera: Mymaridae) on Homalodisca vitripennis (Germar) (Hemiptera: Cicadellidae) eggs

Anagrus epos Girault (Hymenoptera: Mymaridae) is a natural enemy candidate for a classical biological control program targeting the glassy-winged sharpshooter (GWSS), Homalodisca vitripennis (Germar) (Hemiptera: Cicadellidae), in California. Little is known about the biology or ecology of A. epos when it utilizes GWSS eggs as a host. Here, we report the results of laboratory studies that describe the host age preference for oviposition, longevity of A. epos adults provided with different food sources, and developmental rates at six different constant temperature regimes. Anagrus epos is a gregarious parasitoid in GWSS eggs with up to 14 adults emerging from each GWSS egg. In choice and no-choice tests for oviposition, A. epos females successfully parasitized all developmental ages of GWSS eggs (1–8 days old). In choice tests, parasitism rates were significantly higher in 1-, 3-, 4-, and 5-day-old GWSS eggs than in 2-, 6-, 7-, and 8-day-old eggs. If provided with honey and water, honey only, water only, or no food or water, A. epos females lived on average 8.2, 4.7, 2.6, and 1.6 days, respectively. Anagrus epos required 294.1 degree-days above a lower temperature threshold of 12.4 °C to develop from egg to adult (eclosion). Our results provide baseline information useful in the development of an efficient parasitoid mass rearing program for A. epos release and evaluation in California.     

Nymphal development and lerp construction of Glycaspis sp. (Hemiptera: Psylloidea) on Eucalyptus sideroxylon (Myrtaceae) in central-west New South Wales,Australia

The ability to form lerps is common in Australian Psylloidea. Various species of Glycaspis Taylor (Aphalaridae) form conical lerps on different species of Eucalyptus. Lerps, being a rich sugar source, are preferentially fed by bell miners (Aves: Meliphagidae). In this paper we report the process of lerp construction by a purported new species of Glycaspis living on Eucalyptus sideroxylon. This taxon constructs lerps with anal sugary exudates first building the ribs of the lerps and later filling the space between the polymerized ribs with horizontal tractions of the same sugary substance. Developmental events in this taxon do not follow Dyar's rule strictly. Oviposition induces a non-lethal hypersensitive response in the host leaf. Population trends assessed in 2011–2012 and 2012–2013 showed distinct variations, which have been related to environmental factors. In the 2012–2013 sampling, oviposition occurred preferentially proximally to leaf cracks (possibly induced by intense frost events); we infer that this could be a strategy of this taxon to establish an ‘easier’ access to moisture. Sensillar designs vary between the nymphal instars and adults. The trichoid sensilla and sensillar cavities on the antennae perform mechanosensory and olfactory functions. The mouthpart complex includes a relatively long stylet bundle.     

Diapause induction under greenhouse conditions in two populations of Dicyphus hesperus (Hemiptera: Miridae)

The effects of daylength on induction of reproductive diapause were investigated in two populations of Dicyphus hesperus to determine which was more suitable as a biological control in greenhouses without supplemental light. A population from British Columbia Canada (49°36' N Lat.) had a critical daylength of about 15.5 h, whereas that of a population from California, USA (35°43' N Lat.) was between 14.0 and 13.5 h. Under natural daylengths in greenhouses at 49°N Lat., females of both populations exhibited reproductive diapause at a daylength that was consistent with their respective critical daylengths. In spring, a lower proportion of both populations diapaused when exposed to diapause-inducing conditions than in autumn. Reproductive diapause of the females of the BC population was 100% in autumn, but half of those females laid eggs when held in the greenhouse for 6 weeks. A maximum of 63% of females of the California population diapaused in autumn, and most began to lay eggs after 2 weeks. The differences in response to daylength presumably reflect differences between the two localities in the reliability of the critical daylength as a predictor of conditions unsuitable for growth and reproduction. Under greenhouse conditions the California population is essentially non-diapausing, and would be the more suitable of the two populations for use as a biological control agent.     

Assessment of risk of attack to safflower by Ceratapion basicorne (Coleoptera: Apionidae), a prospective biological control agent of Centaurea solstitialis (Asteraceae)

Ceratapion basicorne (Coleoptera: Apionidae) is a prospective biological control agent of yellow starthistle (Centaurea solstitialis, Asteraceae: Cardueae), which is an important invasive alien weed in the western United States. Previous studies have shown that it is possible for this insect to oviposit on and complete development on safflower (Carthamus tinctorius) under no-choice laboratory conditions; however, it has never been reported as a pest of safflower. Field experiments were conducted at three sites in eastern Turkey during 3 years to evaluate the risk of attack on safflower by this insect in its native range. At two sites where C. basicorne was the only apionid observed, no safflower plants were attacked despite high attack rates on yellow starthistle test plants (48–98% of plants infested). At a third site, where C. basicorne and three other species in the same genus; C. scalptum, C. orientale, and C. onopordi were present, 8–26% of safflower plants were infested, but none of the insects reared from safflower during 3 years were C. basicorne. Other authors have reported rearing C. basicorne from field-collected plants of only Ce. solstitialis, Ce. cyanus, Ce. depressa, and Cnicus benedictus. Our results indicate that C. basicorne does not attack safflower under field conditions and that its introduction would not pose a risk to this crop.     

Establishment of Peristenus digoneutis and P. relictus (Hymenoptera: Braconidae) in California for the control of Lygus spp. (Heteroptera: Miridae)

Lygus hesperus Knight is native to the western United States and is a perennial pest of numerous crops in California. It is responsible for triggering the early season application of insecticides on cotton, Gossypium hirsutum L., and strawberries, Fragaria L. Despite several surveys conducted in alfalfa (Medicago sativa L.) grown in central California, nymphal parasitoids associated with L. hesperus and L. elisus have not been found. Two exotic parasitoids were released into California beginning in 1998. Peristenus relictus (Ruhte), formerly P. stygicus Loan, and P. digoneutis Loan were collected from several locations in southern Europe and released at up to six locations over a 6-year period. At the original release site in Sacramento, a 0.25-ha plot of alfalfa, parasitism by P. digoneutis and P. relictus combined increased from zero to 90%, 3 years after the last releases were made. Parasitoids have been recovered from vacant fields of weedy annuals within 2 km of this site. Recoveries at more southerly release sites in central California have been poor.