Effect of temperature on the development of the yam moth, Dasyses rugosella Stainton (Lepidoptera: Tineidae)

Studies on the effect of temperature on the development of the yam moth, Dasyses rugosella Stainton were carried out in the laboratory at four different temperatures, 20°C, 24°C, 29°C and 33°C. The mean fecundity per female at 20°C, 24°C, 29°C and 33°C was 37.6±1.9, 84.2±2.7, 112.3±3.9 and 109.3±3.9 eggs, respectively. Oviposition period ranged from 4.7 days at 20°C to 2.9 days at 33°C. Hatchability of eggs was highest at 29°C with 70.0% and lowest at 20°C with 15.0%. The developmental time decreased with increase in temperature. The mean developmental time at 20°C, 24°C, 29°C and 33°C was 13.8±0.3, 7.8±0.2, 5.1±0.2 and 3.9±0.2 days for the egg, 90.0±0.7, 50.1±0.7, 36.1±0.8 and 23.6±0.8 days for the larval stages, 22.3±2.6, 12.2±0.2, 10.1±0.1, and 7.8±0.2 days for the pupa and 126.1±0.8, 70.1±0.8, 51.3±0.9, and 35.1±0.8 days for the period from egg hatching to adult emergence, respectively. Since fecundity, oviposition and development of the moth were impaired at 20°C, storage of yam tubers at low temperatures (well below 20°C but not lower than 12°C to avoid chilling injury) will significantly retard the development of D. rugosella and help in its control. Unmated individuals lived longer than their mated counterparts. Adult females were always larger than the males. The wing span of the female ranges from 16.9-18.5 and in males from 13.0-15.0 mm. The body length for males ranged from 5.0-6.5 and was 6.5-9.0 mm for females.     

Structure-activity relationships for analogs of (+)-(E)-endo-Β-bergamoten-12-oic acid,an oviposition stimulant ofHelicoverpa zea (Boddie)

-Bergamotenoic acid, a compound previously shown to stimulate oviposition inH. zea, was converted into a set of bicyclic analogs and tested with a set of acyclic side chain analogs to ascertain the molecular structure that maximizes insect behavioral response. While changes in the bicyclic ring elicited no variation in response, alteration in the side chain structure of-bergamotenoic acid resulted in significant changes in moth preference. Free rotation about the C-C bond proximal to the carboxylic acid group appears to be an important structural factor, since saturation of the side chain double bond significantly increased activity. The carboxylic acid group seems to be required for strong oviposition stimulation, since analogs lacking the carboxylic acid group exhibited no significant oviposition activity. Oviposition preference ofH. zea was also influenced by the length of the hydrocarbon chain to which the carboxylic acid is attached. While hexanoic acid was found inactive, the ovipositional preference for the heptanoic and octanoic acids was greatest for the one 8-carbon tested. This and other work suggest that carboxylic acids of specific chain lengths influence the oviposition behavior of bothHelicoverpa andHeliothis species and may be associated with host-plant selection. The potential use of this information in designing integrated pest management strategies for control ofH. zea is discussed.     

Mating disruption of Ephestia kuehniella (Zeller) (Lepidoptera: Pyralidae) in a storage facility: Spatio-temporal distribution changed after long-term application

In the present study, we evaluated the application of mating disruption (MD) for stored-product Pyralidae in a large storage facility of amylaceous products in central Greece. Dispensers were placed in late 2010 until fall 2015, and the stored-product Pyralidae populations were monitored by using pheromone-baited sticky traps and Petri dishes containing semolina were used as oviposition traps. The infesting species that was found was the Mediterranean flour moth, E. kuehniella (Zeller). After the application of MD, the numbers of adult males found on the pheromone-baited traps were reduced in the MD-treated facility, as compared with the untreated (UTC), no MD, facility. Similarly, the numbers of larvae in the oviposition traps were also reduced, as compared with the UTC facility. During the successive years of MD deployment, there was a noticeable decrease in the number of Ephestia kuehniella male adults in the MD-treated facility, but the high density areas, and the infestation foci, were different among years. Hence, in 2014, the majority of the male adults were found at the areas where some years earlier, during the beginning of MD, there were no individuals, or their numbers were low. This suggests that, despite the effectiveness of the method, may be a spatial displacement to other areas. This fact could eventually alter the monitoring protocol, as new infestation foci may occur.     

Antifeedants in the Feces of the Pine Weevil Hylobius abietis: Identification and Biological Activity

Egg-laying females of the pine weevil, Hylobius abietis (L.), regularly deposit feces adjacent to each egg. Egg cavities are gnawed in the bark of roots of recently dead conifer trees. After egg deposition, the cavity is sealed by feces and a plug of bark fragments. Root bark containing egg cavities with feces is avoided as food by pine weevils, which indicates the presence of natural antifeedants. Here we present the first results of the isolation and chemical analyses of antifeedant compounds in the feces of H. abietis. In feeding bioassays, methanol extracts of the feces revealed strong antifeedant properties. Methanol extracts were fractionated by medium-pressure liquid chromatography and the antifeedant effects were mainly found in the fractions of highest polarity. Volatile compounds in the active fractions were identified by gas chromatography–mass spectrometry (GC–MS) and the nonvolatile compounds were characterized by pyrolysis–GC–MS. Based on mass spectra, a number of compounds with various chemical structures were selected to be tested for their antifeedant properties. Antifeedant effects were found among compounds apparently originating from lignin: e.g., a methylanisol, guaiacol, veratrol, dihydroxybenzenes, and dihydroconiferyl alcohol. A weak effect by fatty acid derivatives was found. The types of naturally occurring antifeedant compounds identified in this study may become useful for the protection of planted conifer seedlings against damage by H. abietis.     

Volatile Emissions from Aesculus hippocastanum Induced by Mining of Larval Stages of Cameraria ohridella Influence Oviposition by Conspecific Females

Larval stages of the horse chestnut leafminer Cameraria ohridella can completely destroy the surface of horse chestnut leaves, Aesculus hippocastanum. This study investigated the effect of the degree of leaf browning caused by the insect’s larvae on olfactory detection, aggregation, and oviposition of C. ohridella adults. The influence of A. hippocastanum flower scent on oviposition of the first generation was also evaluated. Utilizing gas chromatography coupled with parallel detection by mass spectrometry and electroantennography (GC-MS/EAD), more than 30 compounds eliciting responses from antennae of C. ohridella were detected. Oviposition and mining by C. ohridella caused significant changes in the profile of leaf volatiles of A. hippocastanum. After oviposition and subsequent mining by early larval stages (L1–L3), substances such as benzaldehyde, 1,8-cineole, benzyl alcohol, 2-phenylethanol, methyl salicylate, (E)-β-caryophyllene, and (E,E)-α-farnesene were emitted in addition to the compounds emitted by uninfested leaves. Insects were able to detect these compounds. The emitted amount of these substances increased with progressive larval development. During late larval stages (L4, L5) and severe loss of green leaf area, (E,E)-2,4-hexadienal, (E/Z)-linalool oxide (furanoid), nonanal, and decanal were also released by leaves. These alterations of the profile of volatiles caused modifications in aggregation of C. ohridella on leaves. In choice tests, leaves in early infestation stages showed no significant effect on aggregation, whereas insects avoided leaves in late infestation stages. Further choice tests with leaves treated with single compounds led to the identification of substances mediating an increase or decrease in oviposition.     

Early Herbivore Alert: Insect Eggs Induce Plant Defense

Plants are able to “notice” insect egg deposition and to respond by activating direct and indirect defenses. An overview of these defenses and the underlying mechanisms is given from a tritrophic perspective. First, the interface between plant and eggs is addressed with respect to the mode of attachment of eggs on the plant surface. It is elucidated which plant cells might respond to components from insect eggs or the egg deposition. The scarce knowledge on the elicitors associated with the eggs or the egg-laying female is outlined. Since endosymbiotic microorganisms are often present on the eggs, and microorganisms are also abundant on the leaf surface, the role of these hidden players for eliciting oviposition-induced plant responses is considered. Furthermore, the question of which physiological and molecular processes are induced within the plant in response to egg deposition is addressed. Second, studies on the response of the herbivorous insect to oviposition-induced plant defenses are outlined. Third, the importance of oviposition-induced plant volatiles and contact cues for host and prey location of parasitoids and predators is discussed in the context of other informative chemicals used by carnivores when searching for food. Finally, physiological and ecological costs of oviposition-induced plant responses are addressed.     

Oviposition attractants and repellents of mosquitoes

Infusions of various organic materials have been known to modify ovipositional behavior of gravid female mosquitoes. Previously, we found that an infusion of Purina Laboratory Chow elicited negative ovipositional behavior inCulex pipiens quinquefasciatus Say andCulex tarsalis Coquillett. In the present chemical studies, the Purina Laboratory Chow infusion, fermented for 10 days, was distilled to give an active distillate which, upon ether extraction, gave an active ether extract. Fractionation of the ether extract yielded an active acidic fraction and inactive nonacidic fraction. Gas Chromatographie analysis on Porapak R and AT-1200-H₃PO₄ columns of the acidic fraction showed the presence of acetic, propionic, isobutyric, butyric, isovaleric, and caproic acids. In bioassay tests, these lower aliphatic carboxylic acids, individually and in combination, exhibited ovipositional repellency against the two species of mosquitoes at the concentration of 6 × 10^–2%. At this concentration, butyric acid caused 100% mortality in first-instar larvae ofC. p. quinquefasciatus. Gravid female mosquitoes might have acquired, through evolutional adaptation, the ability of avoiding ovipositing in unsuitable sites in which toxic compounds might be detrimental to the survival and development of their offspring.Diptera: Culicidae.     

Female-produced oviposition deterrents of the cigarette beetle,Lasioderma serricorne (F.) (Coleoptera: Anobiidae)

Oviposition deterrents of the cigarette beetle,Lasioderma serricorne, were isolated from its adult body extract and found to be identical to (2S,3R,1'S)-2,3-dihydro-3,5-dimethyl-2-ethyl-6-(l-methyl-2-oxobutyl)-4H-pyran-4-one (-serricorone) and its lR-epimer (-serricorone) by spectroscopic evidence. Serricorone was previously found as one of the minor sex pheromone components of the same insect, and hence indicating bi-functional nature. The presence of two isomers in the body was proved by careful treatment. Each of them exhibited the same level of oviposition deterring activity, which was less potent than the crude body extract at an increased concentration.     

Plant secondary compounds as oviposition deterrents for cabbage butterfly,Pieris rapae (Lepidoptera: Pieridae)

Oviposition byPieris rapae butterflies was deterred by spraying the plant secondary compounds coumarin and rutin on cabbage plants in greenhouse choice tests. In no-choice tests ranging from 5 min to 24 hr, acceptance of rutin-treated plants for oviposition increased with trial duration. Both coumarin and rutin deterred oviposition primarily by affecting prealighting rather than postalighting behavior, indicating that deterrence was mediated by noncontact cues.     

Deterrence of repeated oviposition in sorghum shootflyAtherigona soccata

The sorghum shootfly,Atherigona soccata, under low population density conditions lays one egg per sorghum plant. Possible regulatory mechanisms of this oviposition behavior are reported. The presence of an egg thoroughly washed and reattached to a leaf does not deter further oviposition, indicating the absence of visual cues. When washings from eggs were sprayed on sorghum plants, or when plants from which eggs had been removed were presented to a gravid female, significant deterrence was observed. Apparently a deterrent pheromone is associated with the water-soluble glue with which the females attach their eggs to the leaves. Some deterrent effect persists for at least 7 days.