bluuebunny/crossref_metadata_2025 huggingface dataset:
Response of the braconid parasitoid Cotesia (=Apanteles) glomerata to volatile infochemicals: effects of bioassay set‐up, parasitoid age and experience and barometric flux
Authors: Steinberg S. , Dicke M. , Vet L. E. M. , Wanningen R.
Published: April 2011

Upon initiating a research project on the role of volatile infochemicals in the tritrophic system Cotesia (= Apanteles) glomerata (L.) ‐ Pieris brassicae (L.) ‐ cabbage, a bioassay was developed to investigate the response of C. glomerata. The bioassay should be effective in terms of high responsiveness and minimum variability and constructed through a comparative approach. Twenty seven treatments, organized in a factorial randomized block design, compared the effect of three bioassay set‐ups (glasshouse flight chamber, wind‐tunnel and Y‐tube olfactometer), three parasitoid age groups (1–2, 4–5 and 8–9 days old females), three pre‐treatment experiences (naive, damage experienced and oviposition experienced wasps) and the day‐to‐day effect on response of C. glomerata to clean cabbage (CC) and plant‐host complex (PHC) in a dual choice test.

The best results with regard to the strength and consistency of response to the PHC were obtained in the glasshouse flight‐chamber by 4–5 days old female wasps with either damage or oviposition experience (94 and 90%, respectively). It is therefore recommended as a suitable bioassay for studying the role of volatile infochemicals in host‐habitat location by C. glomerata.

A day‐to‐day variation in response was found in the glasshouse and wind‐tunnel. It was correlated with the direction of change in barometric pressure within the time period of the experiment, showing that steadily increasing atmospheric pressure yields a significantly higher response than steadily decreasing or fluctuating barometric flux. To control for the day effect it is suggested to conduct further experiments in a block design, having day as a block. Several aspects of the infochemical ecology of C. glomerata are discussed.
Laboratory evaluation of parasitic hymenoptera used in attempts to biologically control aphid pests of crops in Australia
Authors: Hughes R. D. , Woolcock L. T. , Hughes M. A.
Published: April 2011

As an integral part of a programme to attempt the biological control of several crop‐infesting aphid pests in Australia by the introduction of specific hymenopterous parasites, a laboratory technique to try to predict their likely effectiveness in the field, was developed with the aim of improving selection of natural enemies in future. It was based on demonstrating whether the parasites attack a greater proportion of their hosts with increased host density, i.e. whether they show a Type 3 functional response (Holling, 1959). To overcome the problem of super‐parasitisation at low densities when a parasite is confined with aphids on one plant (van Lenteren & Bakker, 1976) we used several plants in a large cage, all with the same density of host aphids. A parasite released into such a cage searches for and attacks the aphids on one plant, then leaves it to repeat the process on a second plant, and so on. After a standard exposure time the parasitisation rate is estimated separately for the aphids on each plant and the average performance of the parasite calculated. Using this technique for seven parasites introduced into Australia for biological control of crop aphids, only one, Aphidius salicis Halliday, attacking carrot aphid showed a Type 3 response.
Flight responses in a wind tunnel of the parasitoid Microplitis croceipes to three spring and three summer host plants of Heliothis spp
Authors: Kaas J. P. , Elzen G. W. , Ramaswamy S. B.
Published: April 2011

Flight responses of the parasitoid, Microplitis croceipes (Cresson) (Hymenoptera: Braconidae) to two phenological stages of spring host plants (crimson clover, Trifolium incarnatum L., hairy vetch, Vicia villosa Corbiere, and cutleaf geranium, Geranium dissectum L.) and summer host plants (cotton, Gossypium hirsutum L., sorghum, Sorghum bicolor L., and soybean Glycine max (L.) Merr.) of Heliothis virescens (F.), were measured in a dual choice situation in a wind tunnel. Preflowering clover was more attractive than preflowering geranium, followed by preflowering vetch. Clover was preferred over geranium in flowering stages as well. No within species differences were detected for the two phenological stages. Preflowering and flowering cotton and soybean were preferred over preflowering and flowering sorghum. The findings could be important in pre‐determining release sites for M. croceipes in the field.
Pitfall trap catches of and aphid predation byPterostichus melanariusandPterostichus madidusin insecticide treated and untreated potatoes
Authors: Dixon P. L. , McKinlay R. G.
Published: April 2011

Aphids were countedin situand carabid beetle populations assessed by pitfall trapping between 1983–1985 in potato fields in Scotland treated with demeton‐S‐methyl (DSM) or untreated.Macrosiphum euphorbiae(Thomas) (Homoptera: Aphididae) was the most abundant aphid. Nineteen species of carabid beetles were trapped but the fauna was dominated byPterostichus melanarius(Ill.) andPterostichus madidus(Fabr.) (Coleoptera: Carabidae). Pitfall trap catches of these carabids were variable but generally lower in sprayed than unsprayed plots for a few days after DSM application and higher a week or two later. Of 1800P. melanariusand 910P. madidusdissected, 14.4 per cent and 30.5 per cent respectively, contained aphid remains. The proportion that had eaten aphids often was higher in sprayed than unsprayed plots immediately after treatment. In additional experiments, aphids treated with DSM fell from plants; four to five per cent of the theoretically applied dose of DSM reached the ground in a closed‐canopy potato crop; and no mortality occurred whenPterostichusspp. were exposed to DSM in a field bioassay. It is proposed that observed patterns in trap catch ofPterostichusspp. around times of pesticide application may be due in part to aphids falling to the ground after treatment. Beetles that eat these fallen aphids may be less hungry, less active and less likely to be trapped. Later increases in catches may be attributed to hungry, more active beetles, a consequence of prey removal by the insecticide. Although this hypothesis requires further research, it is clear that the effects of insecticide treatment on carabid populations cannot be measured by pitfall trapping alone.
Resistance to Spodoptera exigua in Apium prostratum
Authors: Diawara M. M. , Trumble J. T. , Quiros C. F. , Millar J. G.
Published: April 2011

Two Apium accessions were compared with the commercial cultivar ‘Tall Utah’ 52–70R (A. graveolens [L.]) for resistance to Spodoptera exigua (Hübner)(Lepidoptera: Noctuidae). Oviposition rate was not significantly different between the three genotypes. In all accessions, eggs were usually placed on the upper half of the plants. Implications of this oviposition pattern on S. exigua management in celery are discussed. The wild species A. prostratum ssp prostratum var filiform (A230) showed a significantly higher resistance to S. exigua than 52–70R. The levels of carcinogenic and mutagenic linear furanocoumarins in the commercial cultivar 52–70R (1.41 μg/g in the petioles; 5.85 μg/g in the leaves) and in the plant accession A. nodiflorum (5.40 μg/g in the petioles; 2.99 μg/g in the leaves) were far below the concentration reported to produce acute contact dermatitis (18.0 μg/g). The levels of furanocoumarins in A. prostratum petioles (186.14 μg/g) and leaves (326.45 μg/g) were 10 and 18 times higher, respectively, than the concentration known to cause contact dermatitis. However, resistance in A. prostratum was primarily due to non‐preference and the linear furanocoumarins did not induce non‐preference. Therefore, the resistance shown by this plant accession does not appear to be furanocoumarin‐based and may be suitable for transfer to commercial celery for use in S. exigua management.
Interactive effects of temperature and concentration of the flavonol rutin on growth, molt and food utilization of Manduca sexta caterpillars
Authors: Stamp N. E. , Horwath K. L.
Published: April 2011

A factorial experiment tested the effects of varying concentrations of the flavonol rutin and daytime temperatures of 20 and 30 °C on growth, molting and food utilization efficiencies of third instar tobacco hornworms (Manduca sexta (L.)). Cool temperature prolonged both the growth (= feeding) and non‐feeding periods and consequently the relative consumption rates (RCR) and relative growth rates (RGR). Temperature had no impact on the amount of food consumed and the utilization indices of efficiency of conversion of ingested food and efficiency of conversion of digested food to larval biomass. But rutin was more concentrated in the frass of the larvae at the warm temperature. With increasing levels of rutin in the diet, the efficiency of conversion of ingested food tended to decline. Rutin reduced RCR and RGR. At the cool temperature, rutin increased the time spent in the first portion of the non‐feeding period disproportionately. Analysis of growth rate intervals within the growth period indicated that at the cool temperature rutin had no discernible impact over the first half of the growth period, during which developmental competence to molt is likely achieved. Overall, these results indicate an overlap in the growth and molting phases and suggest that rutin interferes with physiological processes at the time of molt initiation, with these effects magnified at a cool temperature.
Behavioral responses of Ceratitis capitata flies to bait spray droplets and natural food
Authors: Prokopy R. J. , Papaj D. R. , Hendrichs J. , Wong T. T. Y.
Published: April 2011

In studies carried out on field‐caged non‐fruiting host trees, we examined effects of environmental and adult physiological and experiential state factors on responses of released Mediterranean fruit flies, Ceratitis capitata (Wiedemann), to droplets of proteinaceous bait (PIB‐7) with or without 20% insecticide (malathion). We confirmed that fresh PIB‐7 is both attractive and phagostimulatory to proteindeprived medflies and found that presence of 20% malathion ultra low volume concentrate (ULVC) in PIB‐7 droplets does not significantly repel medflies from approaching droplets but does significantly deter feeding on them. A single relatively fresh deposit of bird feces, an important source of protein for medflies in natural environments, attracted several times more laboratory‐cultured and wild medflies than 20 droplets of 80% PIB‐7/20% malathion ULVC (about the average number of droplets per m2of plant canopy in aerial bait spray programs). Attraction to protein was significantly greater among wild medflies deprived of protein continuously from eclosion than among wild medflies that had recent (within 3 days) or continuous access to protein. Attraction to protein increased significantly with increasing age (2, 7 and 12 days) of protein‐deprived wild medflies. But we found no significant positive impact of recent brief experience of wild medflies with protein on degree of subsequent attraction to protein. In final experiments that mimicked the size, density and distribution of bait spray droplets on tree foliage typical for an aerial medfly control program, very few (4%) or no released protein‐deprived wild medflies found a bait droplet within the 15 min test period even though most found a single deposit of bird feces. We conclude that the effectiveness of aerial bait sprays against medflies might be enhanced substantially (and the proportion of infested area treated with bait spray reduced considerably) by (1) including synthetic equivalents of attractive components of bird feces in the spray mixture, and (2) adjusting spatial and temporal patterns of bait spray applications according to estimates of the composition and abundance of natural medfly food and the age structure of medfly adult populations in infested regions.
The development of an improved model trap for monitoring Ephestia cautella
Authors: Quartey G. K. , Coaker T. H.
Published: April 2011

Delta, Covered funnel and Uni‐traps containing pheromone used for monitoring male Ephestia cautella (Walker) (Lepidoptera: Phycitidae) moths were compared in a wind tunnel in moving and still air. The shape and design of the traps and the form of pheromone plume emitted from them determined the moth's latency time, numbers orientating, alighting on the traps and captured. To improve trap design, the visual responses of the moths to rectangles of different colours and sizes and to brown and white stripes, showed that more moths were attracted to darker coloured 6 × 50 cm vertical rectangles on a white background and to 7.5 mm brown and white stripes. A cylindrical trap containing pheromone incorporating these features captured 90% and 80% of the moths released in the wind tunnel in moving and still air respectively, compared with 70% and 35% for the best commercial traps.
Development of Aphelinus mali an endoparasitoid of woolly apple aphid, Eriosoma lanigerum at different temperatures
Authors: Asante S. K. , Danthanarayana W.
Published: April 2011

Developmental times for both sexes of Aphelinus mali (Haldeman) (Hymenoptera: Aphelinidae) an endoparasitoid of woolly apple aphid, Eriosoma lanigerum (Hausmann) (Hemiptera: Pemphigidae) were studied at 13, 15, 18, 20, 25 and 30 °C and compared with those of E. lanigerum. Mean developmental times ranged from 11.7–53.3 days for males, 11.8–55.4 days for females and 11.8–54.4 days for both sexes combined and were significantly inversely related to temperature. A good linear model fit (r2 > 0.99) between developmental rate and temperature in the range 13–30 °C was observed. Results indicate significant differences between developmental times of males and females at 13, 18, 20, and 25 °C but no differences at 15 and 30 °C. The notional developmental threshold was 8.3 °C for both males and females. Compared with its host, A. mali has a higher lower developmental threshold. An average of 252.8, 256.7 and 254.8 degree‐days (DD) above the lower threshold were required by A. mali to complete development from time of oviposition to adult emergence for males, females and both sexes combined, respectively. Field experimentation also indicated that the developmental time of A. mali lags significantly behind that of its aphid host throughout the year. These findings are discussed in relation to its status as a biological control agent for E. lanigerum.
Occurrence of hop aphid phagostimulants in the honeydew of aphids
Authors: Dorschner K. W. , Kenny S. T.
Published: April 2011

Several aphid honeydews were incorporated into sucrose solutions and presented to hop aphids, Phorodon humuli (Schrank), as artificial diets in free‐choice bioassays. Small additions of honeydew collected from two species of aphid feeding on hop, Humulus lupulus L., arrested the searching behavior of the hop aphid and appeared to stimulate prolonged periods of ingestion. This effect was more dependent on the host plant honeydew source than the species of aphid that produced the honeydew. Aphid honeydews collected from plants other than hop (non‐hosts to P. humuli) contained hop aphid phagostimulants that were less effective. Our results indicate that analysis of aphid honeydew could help describe chemical cues involved in the recognition of appropriate host plants by aphid species.
Caterpillars' compensatory feeding response to diluted nutrients leads to toxic allelochemical dose
Authors: Slansky F. , Wheeler G. S.
Published: April 2011

Many herbivores increase their consumption rate as dietary nutrient concentration declines. This compensatory response can mitigate the fitness‐lowering impact of reduced food quality, but little is known about its costs. In this study we tested the hypothesis that one cost to a faster consumption rate can be the ingestion of a toxic dose of an allelochemical occurring in the food. We fed velvetbean caterpillars a diet with progressively diluted nutrient levels but containing the same concentration (% fresh mass, fm) of caffeine, a methylxanthine alkaloid. Larvae compensated for the reduced nutrient level, with those fed the most diluted diet increasing their biomass‐relative consumption rate (fm) 2.6‐fold over larvae fed the undiluted diet. Consequently, their rate of caffeine ingestion increased to a pharmacologically effective dose, interfering with food utilization, slowing growth, reducing subsequent feeding and lowering survival. These results suggest that greater allelochemical ingestion can be one cost of an increased consumption rate, although additional studies with other allelochemicals and species are necessary to more broadly evaluate whether insects can adaptively balance their intake of nutrients and allelochemicals through adjustments in consumption rate. In addition, these results highlight the importance of measuring consumption rates of allelochemicals and other ingested biocides, not just their dietary concentration, when assessing efficacy against herbivores.
Evolution of insect‐plant relationships ‐ a devil's advocate approach*
Authors: Jermy T.
Published: April 2011

Most hypotheses concerning the evolution of insect‐plant relationships are based on the assumptions that, (1) phytophagous insects reduce plant fitness, and that (2) insect‐plant relationships are the result of unconstrained selection. It can be shown, however, that there is little evidence to support these assumptions. As an alternative, it is proposed that the evolution of insect‐plant relationships results primarily from autonomous evolutionary events; namely from heritable functional changes within the insects' nervous system that determine plant recognition and ultimately host plant specificity. These changes cannot be evoked by selective ecological agents. They originate from intrinsic changes (mutations sensu lato) within the insect genome. Ecological factors play a secondary role: by either supporting or preventing the establishment of the new genotype with the novel food preference.
Three inhibitor types from wheat endosperm are differentially active against α‐amylases of Lepidoptera pests
Authors: Gutierrez C. , Garcia‐Casado G. , Sänchez‐Monge R. , Gomez L. , Castañera P. , Salcedo G.
Published: April 2011

Crude α‐amylase preparations from seven Lepidoptera pests were susceptible to inhibition by salt‐soluble proteins of bread wheat (Triticum aestivum L.) endosperm. Protein fractions that corresponded to tetrameric, dimeric, and monomeric wheat α‐amylase inhibitors, were decreasingly effective against the insect α‐amylase activity. To further confirm these results, purified inhibitors were tested against an α‐amylase preparation from Ephestia kuehniella (Zeller). This preparation showed decreased activity when increasing amounts of an heterotetrameric inhibitor (reconstituted from its isolated subunits WTAI‐CM2, ‐CM3 and ‐CM16) were assayed. Activity was only partially inhibited by homodimeric (WDAI‐1, synonym 0.53; WDAI‐2, synonym 0.19) and monomeric (WMAI‐1, synonym 0.28) inhibitors.
Improved two‐component blend of the synthetic female sex pheromone of Cryptophlebia leucotreta, and identification of an attractant for C. peltastica
Authors: Newton P. J. , Thomas C. D. , Mastro V. C. , Schwalbe C. P.
Published: April 2011

A series of field evaluations using the Pherocon‐1C trap examined various doses and blends of the following synthetic pheromone compounds: (E)‐7‐dodecenyl acetate (E7–12:Ac), (E)‐8‐dodecenyl acetate (E8‐12:Ac), (Z)‐8‐dodecenyl acetate (Z8‐12:Ac), decyl acetate (10:Ac), dodecyl acetate (12:Ac), tetradecyl acetate (14:Ac), hexadecyl acetate (16:Ac), and octadecyl acetate (18:Ac). It was concluded that E7–12:Ac is not a true sex pheromone in Cryptophlebia leucotreta (Meyrick) because it only led to significant male catches at doses greater than 1 mg per lure and did not perform as well as mixtures of E8–12:Ac and Z8–12:Ac. The latter mixtures led to significantly higher catches of C. leucotreta when the ratio of E8–12:Ac to Z8–12:Ac was 9:1 rather than 1:1 as in commercial lures. Increases in dosages of this blend from 1 mg to 50 mg per lure did not lead to increases in male moth catches. An additional 10% 12:Ac had no consistent significant effect on numbers of captured males. 10:Ac, 12:Ac, 14:Ac, 16:Ac, and 18:Ac, individually or in various combinations with 9:1 E8–12:Ac and Z8‐12:Ac corresponding to their average proportions in female pheromone glands, did not lead to significant increases in C. leucotreta catches. Blends of E8–12:Ac and Z8–12:Ac at 1 mg per lure also resulted in catches of males of the litchi moth, Cryptophlebia peltastica (Meyrick), when containing 70% or more Z8–12:Ac. Maximum catches of C. peltastica occurred in traps baited with 100% Z8–12:Ac.
Flight periodicity of Prostephanus truncatus and longevity of attraction to synthetic pheromone
Authors: Tigar B. J. , Key G. E. , Flores‐S M. E. , Vazquez‐A M.
Published: April 2011

Double‐sided sticky traps were baited with polythene vials containing synthetic components of the aggregation pheromone of Prostephanus truncatus (Horn) and used to investigate the effect of time of day on capture of this insect. P. truncatus exhibited a bimodal pattern of flight activity with a major peak between 18.00 and 21.00 h, and a smaller peak between 07.00 and 09.00 h. The effective life of the pheromone bait was also investigated over 33 days. The highest numbers of P. truncatus were caught during the first 8 days and the majority of the beetles were caught within 14 days. Catches then showed a steady decline. Captures of the predatory histerid Teretriosoma nigrescens Lewis, were much lower than those of P. truncatus and showed fluctuations which did not appear related to numbers of its prey. Environmental factors such as rainfall, temperature, wind and trap positioning appeared to influence results, especially when considered over a short time scale.
Genetic control of geographic variation for cannibalism in the southwestern corn borer, Diatraea grandiosella
Authors: Tarpley M.D. , Breden F. , Chippendale G. M.
Published: April 2011

The southwestern corn borer, Diatraea grandiosella Dyar, is a subtropical insect whose range has expanded northward within this century. Geographic variation exists between populations at the extremes of the range for a suite of morphological and behavioral characters, including cannibalism. Laboratory colonies established from a Missouri population (37°N lat.) with a high cannibalism rate and a Mexican population (19°N lat.) with a low cannibalism rate were used to examine the genetic basis of cannibalism by means of a controlled breeding design. When larvae were held in pairs on artificial diet in 30 ml plastic cups at 30 °C 16L:8D, the highest incidence of cannibalism in both Missouri and Mexican populations was found in larvae 15 to 18 days‐of‐age (5th and 6th instars). Under these conditions, cannibalism was expressed in 33 % of the pairs formed from Missouri larvae and 11 % of the pairs formed from Mexican larvae. First and second generation crosses between Missouri and Mexican populations showed an intermediate level of cannibalism, whereas backcrosses to the parental generations showed a regression to the parental phenotypes. These results indicate that cannibalism is under additive genetic control. Larvae from the Missouri parental population were more likely to consume their victim (i.e., cannibalize) once intraspecific killing had occurred than were larvae from the Mexican parental population or from any of the crosses, and female larvae were cannibals more often than were males. Under the conditions employed, no advantage was detected for cannibalism over instraspecific killing for larval weight gain or growth rate.
A multivariate analysis of growth and development parameters of the legume pod borer, Maruca testulalis on variably resistant cowpea cultivars
Authors: Oghiakhe S. , Odulaja A.
Published: April 2011

Principal component analysis was employed to study the variation patterns in 18 cowpea cultivars developed for resistance to Maruca testulalis Geyer (Lepidoptera: Pyralidae) based on 7 developmental parameters of the pest on floral buds, flowers and sliced pods. On the whole, three developmental parameters: percentage pupation (V2), percentage emergence (V5) and growth index (V7) were the most important for the grouping of the cultivars with respect to M. testulalis damage. However, out of the three parameters, growth index (V7) had the highest factor score. Using the cluster analysis technique, the cultivars were sorted into five distinct groups for each part. The importance of these findings in the determination of protection periods for particular cultivars and cultural control studies of M. testulalis in cowpea are discussed.
Effect of plant water stress on honeydew production, weight gain and oviposition of brown planthopper Nilaparvata lugens on rice cultivars
Authors: Baqui M. A. , Kershaw W. J. S.
Published: April 2011

Glasshouse studies were made on honeydew production, adult and nymphal body weight gain, fecundity and size of egg groups of brown planthopper Nilaparvata lugens (Stål) (Homoptera: Delphacidae) (BPH) on CVS TN1, ASD7, Babawee, Mudgo, Rathu‐Heenati and Ptb33 rice plants with watering regimes of 10 ml, 20 ml, 30 ml and excess water daily. Honeydew production, weight gain, fecundity and size of egg groups were greatest on TN1, followed by ASD7. BPH did less well on Babawee, Mudgo and Rathu‐Heenati and they did worst on Ptb33. Watering regimes greatly affected performance, with significantly less honeydew, less weight gain, lower fecundity and smaller egg groups on plants with 10 ml water daily than on plants with excess water. The 20 ml and 30 ml watering regimes also significantly reduced honeydew production on TN1 and ASD7 and fecundity and weight gain of adults and nymphs on Mudgo. On Babawee adults gained most weight on the 20 ml and 30 ml treatments, and nymphs gained most weight on the 30 ml treatment. BPH laid most eggs on TN1, ASD7, Babawee and Rathu‐Heenati when plants were given 30 ml water daily.
Management of a German cockroach population with a juvenoid bait formulation: computer simulation
Authors: Zeman P.
Published: April 2011

A computer model was applied to simulate responses of German cockroach populations to feeding on juvenoid baits during an equilibrium, exponential, and the earliest phase of population growth. The simulations show that the renewal potential of the cockroach populations will be exhausted when about 80% or more adults become sterile. The attainment of this activity threshold will be preceded by a lag time with no apparent control effect. The time delay appears substantially shorter for both growing populations (30–60 days) than for the equilibrious one (90–120 days), but, the former ones will continue growing throughout this lag. The simulations predict that even a worse baits' performance can give sufficient control effect in the field if the baits are laid in an early phase of population growth. Thus, optimum tactics should integrate administration of juvenoid baits with an introductory reduction of cockroach population.
Effects of host plant leaf damage on cabbage looper moth attraction and oviposition
Authors: Landolt P. J.
Published: April 2011

Mated female Trichoplusia ni (Hubner) moths, when presented a choice of either undamaged cotton plants, Gossypium hirsutum L., or damaged plants (cut leaves or feeding T. ni larvae) in a flight tunnel, were most often attracted first to the damaged plants. However, these same moths oviposited primarily on the undamaged plants. In a similar test with cabbage plants, Brassica oleracea L., the presence of conspecific larvae decreased both attraction and oviposition. Cuts to cabbage leaves had no significant effect on attraction or oviposition. When presented one plant at a time, percentages of cabbage looper moths attracted were not affected by the presence of larvae on either cabbage or cotton plants, or by cuts to cabbage plant leaves. Percentages of moths attracted were, however, higher using cotton plants with cut leaves. The results suggest an important role for damage induced plant volatiles in host location as well as host acceptance by T. ni.
Influence of developmental conditions on cold‐hardiness of adult Dalbulus leafhoppers: implications for overwintering
Authors: Larsen K. J. , Lee R. E. , Nault L. R.
Published: April 2011

Little is known about how adults of the corn leafhopper, Dalbulus maidis (DeLong & Wolcott), and its congeners survive subfreezing temperatures at high elevations during the dry winter in Mexico. In the laboratory, duration of survival at −5 °C was measured for four Mexican Dalbulus species: D. maidis, D. elimatus (Ball), D. gelbus DeLong and D. quinquenotatus DeLong & Nault; and a closely related North American species, Baldulus tripsaci Kramer & Whitcomb. Adult leafhoppers reared under environmental conditions that simulated the beginning of the dry winter season during October in Mexico (‘October‐reared’) were at least twice as tolerant of −5 °C than adults reared under environmental conditions that simulated the beginning of the wet summer season during June (‘June‐reared’). Dalbulus species found primarily at high elevations, such as D. elimatus, were seven times more tolerant of −5 °C than D. quinquenotatus, a species which overwinters at low to mid elevations on its Tripsacum hosts. October‐reared D. maidis adults survived relatively short periods at −5 °C (LT50 = 8.9 h) compared to October‐reared D. elimatus adults (LT50 = 42.3 h). This suggests that in Mexico, D. maidis either overwinters in protected habitats at higher elevations or it migrates to lower, frost‐free regions. October‐reared B. tripsaci adults, which overwinter in the egg stage, were intolerant of −5 °C (LT50 = 2.6 h). A conditioning period for 1 h at +5 °C before and after exposure to −5 °C significantly improved survival for D. maidis. Supercooling points (SCPs) were between −23 and −20 °C, indicating that mortality of these leafhoppers at −5 °C was due to cold shock injury rather than internal ice formation.
Larval performance of two leafroller species on known and potential hosts
Authors: Smirle M. J.
Published: April 2011

Two univoltine leafroller species, Archips argyrospila Walker and Archips rosana L., were reared from eclosion to adulthood on known or potential host plants. Both species were able to complete development on eight of the ten plants tested, the exceptions being apricot and peach. Rates of development differed among hosts, and indicated a range of host suitability. Differences in female pupal weights were apparent following the different rearing treatments, but these did not correlate with subsequent female fecundity. When development was compared between the two leafroller species, A. rosana had higher survivorship, more rapid development and higher female fecundity than did A. argyrospila, regardless of host. These findings indicate that A. rosana may successfully exploit a wider host range than does A. argyrospila. Comparisons of survivorship and developmental rates among hosts for each species of leafroller suggest that both species may have the potential for host‐range expansion.
Conserving genetic variability of a wild insect population under laboratory conditions
Authors: Delpuech J‐M. , Carton Y. , Roush R. T.
Published: April 2011

Drosophila melanogaster (Meigen) was used to test the power of isofemale lines in preserving genetic variability. We performed experiments in two ways. One series consisted of measuring the genetic variability for three enzymatic loci in 32 isofemale lines, in the first and 23rd generations of culture. In the second series, we tested the capacity of the larvae to eliminate a parasitoid by encapsulation after eight years of laboratory breeding. In general, individual isofemale lines appeared to change during the 23 generations of the study, but the global frequency of these alleles among the 32 isofemale lines stayed relatively unchanged. The only rare allele observed was also conserved. Changes in allozyme frequencies at any one locus were independent of those at other loci. Genetic variation of a biological trait, the capacity of the larvae to encapsulate a parasitoid, also changed, but it could be restored to a level close to that of the starting population by mass hybridizing together individuals of each line.

D. melanogaster (Meigen) a été utiliseé pour tester la capacité des lignées isofemelles à conserver la variabiliteé génétique d'une population naturelle. Deux types d'expériences ont été réalisées. L'une a consisteé à déterminer la variabiliteé génétique de 3 locus enzymatiques pour 32 lignées isofemelles à la première et à la 23éme génération d'élevage au laboratoire. L'autre a consisté a tester la capacité des larves à éliminer un parasitoïde par le processus d'encapsulation après 8 années d'élevage au laboratoire. D'une façon générale, certaines lignées isofemelles perdent de la variabilité durant les 23 générations de l'étude. Mais la fréquence globale des allèles reste inchangée si l'on considère l'ensemble des 32 lignées. Le seul allèle rare observé a également été conservé. Les modifications des fréquences allèliques à chacun des locus ont lieu de façon indépendante les unes des autres. La variabilité génétique d'un caractère biologique, la capacité des larves à encapsuler le parasitoïde, a également varié, mais elle a pu être restaurée à un niveau proche de la population initiale en rassemblant plusieurs individus de chacune des lignées.
Responses of a compatible lucerne variety to attack by spotted alfalfa aphid: changes in the redox balance in affected tissues
Authors: Jiang Y. , Miles P. W.
Published: April 2011

The spotted alfalfa aphid, Therioaphis trifolii maculata (Buckton), caused local browning of cells surrounding feeding sites on lucerne plants (cv. Hunter River). Aqueous extracts of infested leaves underwent a marked browning process that did not occur in extracts of healthy leaves. The process was accelerated by addition of tyrosinase and peroxidase and reversed by reducing agents such as ascorbate and glutathione. In the presence of added reducing agents, the extracts produced brown precipitates, probably conjugates of phenolics with leaf proteins similar to those involved in the sealing of damaged tissues in vivo.

Partially autoxidised catechin (PAC) solutions showed an absorbance peak at 438 nm that was increased by polyphenol oxidase and decreased by ascorbate and glutathione. When extraction of tissues into PAC was used to assess redox activities, healthy tissues showed a rapid, short lived oxidising activity combined with a much more persistent reducing activity, whereas infested leaves had even greater oxidising activity and no detectable reducing activity.

Soluble phenolics increased in infested leaves and stems. Total protein decreased, but the specific activity of peroxidase, catechol oxidase and superoxide dismutase relative to protein content increased. The ability of extracts to reduce cytochrome c increased, indicating an overall increase in superoxide radicals in attacked tissues.

These results are consistent with a general disturbance of redox balance induced in tissues by aphid feeding, including accumulation of oxidases and phenolic substrates and loss of reducing activity and protein.
Distribution of second generation European corn borer, Ostrinia nubilalis, egg masses in field corn and relationship to subsequent tunneling damage
Authors: Sorenson C. E. , Kennedy G. G. , Van Duyn J. W. , Bradley J. R.
Published: April 2011

The relationship between second generation European corn borer (Ostrinia nubilalis Hübner) egg mass numbers and subsequent field corn damage, as measured by stalk cavity numbers, was studied in 79 fields in northeastern North Carolina over three years. A mean of 0.028 egg masses per plant (645 egg masses/23400 plants) was found over the course of the study. Significant differences in oviposition rate were detected between fields and years. Ca. 85% of egg masses were deposited in a five leaf zone surrounding the primary ear; of these, 89% were found on the lower four leaves in this zone. Egg masses appeared to be distributed randomly within fields but at low rates of incidence, and oviposition was relatively uniform between sampling areas within individual fields. Under moderate to high oviposition pressure (mean number of egg masses per plant over the duration of the oviposition period >ca. 0.02), eggs laid during the early phases of the oviposition period account for more subsequent stalk damage than eggs laid during the later phases of the oviposition period. Variations in second generation egg mass numbers accounted for ca. 70% of variation in stalk cavity numbers.
Ovipositional preference of Siphoninus phillyreae and its fitness on seven host plant species
Authors: Leddy Paula M. , Paine Timothy D. , Bellows Thomas S.
Published: April 2011

The relationship between ovipositional preference of Siphoninus phillyreae (Haliday) (Homoptera: Aleyrodidae) and host plant suitability on seven host plant species (Citrus sinensis (L.) cv. ‘Washington’ [navel orange], Fraxinus uhdei (Wenz.) [shamel ash], Heteromeles arbutifolia Roemer [toyon], Malus domestica Mill. cv. ‘Granny Smith’ [apple], Pistacia vera L. cv. ‘Kerman’ [pistachio], Prunus persica (L.) cv. ‘O'Henry’ [peach], and Pyrus communis L. cv. ‘Bartlett’ [pear]) was evaluated. Ovipositional preference of S. phillyreae was determined by measuring egg density after adult female whiteflies were given a simultaneous choice of all host plants for oviposition. Immature survival, developmental time, and adult size were examined to determine host plant suitability for S. phillyreae. All studies were performed under greenhouse conditions. S. phillyreae showed distinct ovipositional preference among host plant species. Host plant species had a significant effect on immature survival, but little or no effect on developmental time or forewing length. For four of the seven host plant species tested, there was an association between ovipositional preference and survival.
Systemic antifeedant effects of azadirachtin on the peach‐potato aphid Myzus persicae
Authors: Nisbet A. J. , Woodford J. A. T. , Strang R. H. C. , Connolly J. D.
Published: April 2011

The electrical penetration graph (EPG) method was used to analyse the feeding behaviour of apterous, adult Myzus persicae (Sulzer) (Homoptera: Aphididae) on Nicotiana clevelandii (Gray) seedlings, treated systemically with azadirachtin. A preliminary experiment showed that the effects of tethering aphids for EPG recording were minimal. The percentage of the 9 h recording period devoted to non‐penetration activities, and to stylet pathway patterns increased as the azadirachtin concentration in the root treatment increased. The number of probes initiated, and the numbers of sieve tube penetrations also increased with increased azadirachtin concentration. The mean time elapsing between the initiation of the first probe to reach a sieve element and contact with this tissue was not significantly altered by azadirachtin treatment. However, azadirachtin treatment significantly reduced the percentage of probes that reached sieve elements and increased non‐penetration activity before and after the first period of ingestion from the sieve elements. The percentage of the recording period spent in the EPG pattern associated with sieve tube penetration was significantly reduced by an azadirachtin concentration of 300 ppm, and the duration of each individual penetration was significantly reduced by an azadirachtin concentration of 100 ppm. When the total EPG was split into 3 h periods, significant interactions were seen between time period and azadirachtin concentration for the duration of non‐penetration, pathway, and sieve tube penetration patterns.
Effects of a host plant, Brassica juncea, on calling behaviour and egg maturation in the diamondback moth, Plutella xylostella
Authors: Pittendrigh B. R. , Pivnick K. A.
Published: April 2011

The influence of the presence of seedlings of a host plant, Oriental mustard, Brassica juncea (L.) Coss., on the calling behaviour and egg maturation in the diamondback moth, Plutella xylostella (L.), was investigated. In the presence of plants, females began calling at a younger age, began calling earlier in the night, and spent more time calling. Females which were kept with plants until after their first night of calling and then were isolated from plants, subsequently called less, at a level not significantly different from females which had never been exposed to plants. Of all females, both with and without plants, which were dissected at the end of the first night of calling (n = 150), 93% contained mature eggs. Heavier females were significantly more likely to have mature eggs at adult emergence, to begin calling at a younger age and to spend more time calling on their first night of calling. The number of developed eggs in calling females was not significantly different in the presence or absence of host plants on the first night of calling. However, by the second night, females in the presence of plants contained significantly more eggs, indicating that the presence of plants accelerated egg maturation, both before and after the onset of calling.
Hemocyte surface changes in the migratory grasshopper, Melanoplus sanguinipes in response to wounding and infection with Beauveria bassiana
Authors: Miranpuri G. S. , Khachatourians G. G.
Published: April 2011

Surface changes of hemocytes from the migratory grasshopper, Melanoplus sanguinipes (Fab.), following wounding and/or infection with Beauveria bassiana (Bals.) Vuillemin were assessed using fluorescein labelled wheat germ agglutinin (WGA) and concanavalin A (Con A). Binding was observed on outer wall of hemocytes when either Con A or WGA conjugates were tested. After infection there was an increase in the percentage of hemocytes which bound to WGA and which remained so for 24 h. However, after wounding this increase in binding subsided after only 1 h. Furthermore, it was found that the increase in WGA‐binding occurred within the first 15 min of wounding or infection. In addition, ConA binding in males only increased 3‐fold in fungus‐injected insects within 1 h of treatment and remained high for 24 h. These results indicated the presence of mannose (and/or glucose) residues (Con A specificity) and N‐acetyl‐D‐glucosamine residues (wheat germ agglutinin; WGA specificity) on outer wall surfaces of the hemocytes. The implications of these results in the immune response of M. sanguinipes to infection with B. bassiana are discussed.
Effects of the antifeedant polygodial on plant penetration by aphids, assessed by video and electrical recording
Authors: Powell G. , Hardie J. , Pickett J. A.
Published: April 2011

Adult apterous Myzus persicae (Sulz.) discriminated within 2 min between mature Chinese cabbage (Brassica pekinensis L.) leaf halves treated with (±)‐polygodial solution and solvent alone, and walked off leaf areas treated with polygodial faster than off the solvent‐treated areas. However, when aphids were attached to a fine gold wire and stylet penetration of cabbage leaves was recorded electrically, polygodial treatment did not affect the number or duration of electrically‐recorded penetrations, time taken to initiate a first penetration, or total penetration time. As the tethering of aphids causes behavioural restrictions which may negate the response to polygodial, indications of stylet penetration by freely‐moving insects were sought. Simultaneous electrical recording and video monitoring showed that stylet penetration duration could be accurately inferred from antennal and body movements, enabling assessment of penetration times without attachment to the wire tether. When freely‐moving M. persicae were video recorded during 15 min access to cabbage seedlings, polygodial treatment again had no apparent effect on stylet penetration. However, when aphids were presented with a choice of polygodial‐ and solvent‐treated sides of floating mature cabbage leaf discs, video recordings revealed that the insects spent less time and made fewer penetrations on the polygodial‐treated side. In addition to this rapid repellent effect, prolonged exposure to polygodial also produced behavioural changes. After being held for 24 h on polygodial‐treated leaves or green paper prior to behavioural examination, aphids penetrated seedlings fewer times but for longer periods. The relevance of the results to virus transmission studies is discussed.
In vitro rearing of Bracon mellitor and Catolaccus grandis with artificial diets devoid of insect components
Authors: Guerra Antonio A. , Robacker Karen M. , Martinez Susana
Published: April 2011

Bracon mellitor Say (Hymenoptera: Braconidae), and Catolaccus grandis Burks (Hymenoptera: Pteromalidae), ectoparasitoids of the boll weevil, Anthonomus grandis Boheman, were reared in vitro for the first time on artificial diets devoid of insect components. The duration of the life cycles from egg to adult when these parasitoids were reared in vivo on boll weevil larvae, on semi‐artificial diets retained with cotton fabric pads, or on diets with low agar concentrations (0.7%) were ca. 15.5, 16.5, and 15.0 days, for B. mellitor and 16.0, 17.5, and 15.5 days, respectively, for C. grandis. Percent adult emergence obtained with the same treatments was 58, 25, and 65 percent, for B. mellitor and 50, 28, and 60 percent, respectively, for C. grandis. Adult morphological characteristics and mating appeared normal. Male to female sex ratios were ca. 45:55 for both species.
Evaluation of artificial diets and two species of natural prey as laboratory food for Chilocorus spp
Authors: Hattingh Vaughan , Samways Michael J.
Published: April 2011

Promising diets were screened and the most successful modified with additives used in artificial diets for other entomophagous insects. Two suitable diets were obtained, one for adults and one for larvae of Chilocorus nigritus (Fabricius) (Coleoptera: Coccinellidae). They were still inferior to natural prey and not adequate as the sole food source for rearing consecutive generations. They are valuable as substitute food in the insectary during shortages of natural prey. Oleander scale Aspidiotus nerii Bouché and Asterolecanium miliaris (Boisduval) were evaluated as natural prey for C. nigritus and two other potential biocontrol agents in southern Africa, C. bipustulatus (Linnaeus) and C. infernalis Mulsant. A. nerii and A. miliaris were suitable for all life stages of C. nigritus and adults of C. bipustulatus and C. infernalis. A. miliaris was inadequate for larvae of C. bipustulatus and C. infernalis.
Effect of maize plants on colonisation of cowpea plants by bean flower thrips, Megalurothrips sjostedti
Authors: Kyamanywa S. , Baliddawa C. W. , Ampofo K. J. O.
Published: April 2011

The effect of non‐host maize plants on colonisation of cowpea by Megalurothrips sjostedti (Trybom) (Thysanoptera; Thripidae) was investigated.

There were no differences in population density and activity of M. sjostedti on sole cowpea crop and mixed cowpea/maize crop during the colonisation phase (i.e. 10–30 days after emergence of the plants. However, subsequently M. sjostedti numbers were lower in the mixed than in the sole crop, suggesting that maize did not interfere with colonisation of cowpea crop by thrips. In a choice situation, higher numbers of M. sjostedti oriented towards, and settled on, sole cowpea plants than on those mixed with maize. Olfactory tests indicated that fewer thrips oriented towards a cowpea/maize mixed odour source. When equal numbers of thrips were introduced into the centre of sole‐ and mixed‐cropped cowpea plots, the thrips became randomly distributed in each plot. Fewer thrips were recovered from the mixture than from the sole crop.

It is concluded that, although non‐host plant odours do not reduce thrips colonisation they interfere with host plant utilisation.