An automated technique for monitoring carbon dioxide respired by insects*

ABSTRACT. A non-dispersive infrared gas analyser equipped with a Luft-type sonic detector and flow-through reference cell was automated to monitor the total volume of carbon dioxide (CO₂) respired by single insects or groups of insects. The infrared analyser was interfaced with an integrator for quantification, a microprocessor to control intermittent air flow through the insect respiration chambers, and a microcomputer for data storage and reduction. This technique has been used to monitor the CO₂ Output of diapausing and non-diapausing mature fifth instar larvae and of developing pupae of the codling moth, Cydia pomonella (L.) (Lepidoptera: Tortricidae). The resulting data were accurate, quantitative and reproducible.     

Les régulateurs de croissance d'insectes (RCI), mimiques de l'hormone juvénile,en tant que moyen de lutte morphogénétique et ovicide contre les tordeuses des vergers

Résumé La métamorphose des insectes est régie par un équilibre hormonal complexe dans lequel l'hormone juvénile (HJ) joue un rôle important. Au dernier stade larvaire, la teneur en HJ est particulièrement faible dans le corps de l'insecte. Si un régulateur de croissance d'insectes (RCI)-un mimétique de l'HJ-est appliqué à ce moment-là, la mue nymphale est pertubée provoquant des déformations morphogénétiques caractéristiques. La teneur en HJ est également très faible dans les ufs fraîchement pondus. Les traitements aux RCI peuvent par conséquent perturber le développement embryonnaire de certaines espèces et produire ainsi un effet ovicide. Depuis quelques années deux RCI-le fenoxycarb et le CGA 45 128-ont été testés pour leur activité morphogénétique sur le dernier stade larvaire de quelques ravageurs tels qu'Adoxophyes orana F.v.R., ainsi que pour leur activité ovicide sur les ufs frais de Cydia pomonella L. et Grapholita funebrana Tr. Après quelques années d'expérimentation et de commercialisation des RCI dans les vergers européens, il s'avère que l'utilisation de ces produits peu toxiques, sélectifs et peu nocifs pour la faune utile, constitue une amélioration considérable pour l'aménagement de la lutte intégrée.

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Insect growth regulators (IGR), mimics of juvenile hormone, as morphological and ovicidal means of control against orchard tortricids

Summary Metamorphosis is regulated by a complex hormonal balance in which juvenile hormone (JH) plays an important part. At the last larval instar the content of JH is particularly low in the insect body. If an insect growth regulator (IGR) — a mimic of JH-is applied at this time, the pupal moult may be disturbed with the characteristic morphogenetical deformations. The JH content is also very low in freshly laid eggs. Therefore IGR treatments may disturb the embryonic development of some species and produce an ovicidal activity. During a few years two IGR-fenoxycarb and CGA 45128-were evaluated for their morphogenetical effect on the last larval instar of Adoxophyes orana F.v.R. and their ovicidal effect on freshly laid eggs of Cydia pomonella L. and Grapholita funebrana Tr. After a few years of experimentation with both compounds and of commercialisation of fenoxycarb in European orchards, IGR confirmed to present a considerable improvement in integrated pest management due to selectivity, and low mammal toxicity.

     

Death of Cydia pomonella larvae and damage to apple fruit, after field application of codling moth granulosis virus

In field experiments, larvae of codling moth Cydia pomonella (L.) rarely acquired granulosis virus on hatching from the egg, but picked up most later, on the tree surface. Deposits of virus sprayed in 1.0% w/v skimmed milk did not affect neonate larval behaviour. Larvae died, usually in the first instar, after entering treated fruit, but they frequently entered via the calyx or near the base of the stalk or through cracks in the skin, where little feeding damage by first-and sometimes second-instar larvae was seen.

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Résumé En verger, la pulvérisation d'oeufs de carpocapse avec du virus de la granulose en suspension dans l'eau (additionnée de lait écrémé dilué à 1%) n'a pas modifié la survie des chenilles avant pénétration dans le fruit; par contre la pulvérisation des arbres a provoqué une forte mortalité. Bien que des chenilles consommant des poils et la surface des feuilles aient été observées avant leur pénétration dans le fruit, ce qui aurait pu provoquer leur contamination par le virus, il semble que la contamination létale provienne des fruits seuls.La présence de produit n'a modifié ni le comportement larvaire, ni le taux de pénétration dans les fruits; la mortalité y a lieu ensuite, généralement au premier stade. Dans 74 à 78% des cas, les chenilles ont pénétré dans le fruit par le calice ou près de la base du pédoncule — aucun dégât provenant de larves du premier stade n'y était visible, de même que dans le calice pour les larves du deuxième stade. Par contre, toute pénétration par la surface du fruit était repérable dès le premier stade. Il est possible que la répartition des lieux de pénétration dans le fruit influe sur la létalité due au virus et explique les variations d'efficacité observées en verger. Un système de classification des dégâts, provoqués lors de la pénétration dans le fruit, de chenilles du premier au troisième stade est proposé pour évaluer l'efficacité des essais en verger.

     

Population-biomass dynamics and the absence of - 3/2 self-thinning in the clonal weed Salvinia molesta

Abstract In the field, the population density (n) of crowded, living ramets of Salvinia molesta ranged from 2500 m ^?2 in nutrient-poor water to more than 30 000 m^?2 in nutrient-rich water. Biomass of living shoots (B) in some localities exceeded 600 gm^?2 dry weight (150 tonnes ha^?1 fresh weight) and shoots plus roots of living and floating dead material exceeded 1600 gm^?2 dry weight (400 tonnes ha^?1 fresh weight). The ultimate limit B= 10⁵n^0.5 suggested by previous authors was not exceeded. The highest n and smallest ramets occurred in nutrient-rich water and B was a linear function of n. Field experiments confirmed no effect of n, but a strong effect of nutrient availability, on ramet weight. In a glasshouse experiment, ramet populations did not ‘self-thin’ along the log log B-n trajectory of slope -0.5, which has been suggested for aclonal plants, but followed trajectories having slopes closer to +1.0 before halting at the ambient B-n limit. Nutrient concentrations in the plants increased during the experiment, causing ramet size to decrease and slopes of log log B-n trajectories to depart from +1.0 by amounts which reflected the degree to which nutrient concentration had changed. Under constant conditions, mean ramet size is expected to remain constant and log log B-n trajectories to travel in a straight line of slope +1.0 to the ambient B-n limit. This behaviour of salvinia, whose ramets consist of a single structural module, is contrasted with that expected of clonal plants whose ramets are made up of multiple structural modules. A logistic model explained the increases in n and biomass of living and dead ramets when ramets were assumed to have constant longevity, constant time to decay, and when both the B-n limit and size of ramets were dependent on nitrogen content of the plant. There was no indication that physiological integration within phenets halted production of new ramets when carrying capacity was reached and new ramets continued to be produced on top of older ramets. Rates of ramet mortality were equal to, and dependent on, rates of ramet natality.     

Field observations quantifying attraction of four tortricid moths to high-dosage pheromone dispensers in untreated and pheromone-treated orchards

Orientational responses of four species of feral tortricid moths (Lepidoptera: Tortricidae) to polyethylene tube dispensers of pheromone were observed in a 0.8 ha apple orchard treated with such pheromone dispensers and in an untreated 0.8 ha orchard. Male oblique‐banded leafrollers, Choristoneura rosaceana (Walker) (mean 7.2 ± 0.4 moths/night during 21 nights), Oriental fruit moths, Grapholita molesta (Busck) (mean 10.5 ± 2.1 during 20 evenings), and the redbanded leafrollers, Argyrotaenia velutinana (Walker) (mean 2.0 ± 1.1 during 14 nights) were observed approaching within 100 cm of their respective polyethylene‐tube pheromone dispensers in the untreated orchard. Furthermore, C. rosaceana (mean 2.0 ± 0.7 during 17 nights) and G. molesta (mean 1.5 ± 0.4 over 20 evenings) came within 100 cm of their respective polyethylene‐tube pheromone dispensers in the pheromone‐treated orchard. Most visits lasted less than 10 s, after which the majority of moths departed by flying upwind. In the untreated orchard, the number of C. rosaceana observed orienting to polyethylene tube dispensers was greater than the number captured in optimized monitoring traps (1.9 ± 0.4) per night of observation. The numbers of A. velutinana (2.0 ± 1.1) or G. molesta (10.5 ± 2.1) attracted to polyethylene‐tube dispensers in the untreated orchard did not differ statistically from the numbers captured in optimized monitoring traps per night of observation. In the pheromone‐treated orchard, the number of C. rosaceana (2.0 ± 0.4) or G. molesta (1.2 ± 0.2) observed orienting to polyethylene‐tube dispensers did not differ statistically from the numbers of male moths of these species captured in optimized monitoring traps per night of observation. No codling moths, Cydia pomonella L. were observed orienting to, or landing near, their respective polyethylene‐tube dispensers in either the untreated or pheromone‐treated orchards, although substantial numbers were captured in monitoring traps per night of observation (6.0 ± 1.7) in the untreated orchard. The attraction of male moths to polyethylene tube dispensers thus occurred in three of the four species observed. These results provide support for the idea that false‐plume‐following is an important component of the mechanisms mediating communicational disruption in moths by polyethylene‐tube dispensers.     

Short-term variations in catches of the pea moth,Cydia nigricana, in interacting pheromone traps

Short-term variations in the relative catch in each of two or three interacting pheromone traps for the pea moth,Cydia nigricana (F.), were investigated for traps aligned along the wind. The proportional catch in each trap varied widely, although the mean values accorded with previous estimates. Over consecutive short intervals during a single trapping period the proportion caught in the centre trap of a three-trap line was constant. The proportion caught in the upwind trap of two-and three-trap lines showed trends in time. These trends differed between trapping periods, but two lines of traps operated simultaneously gave similar results to each other. It is suggested that these results, which are predicted by a model based on various components of moth orientation behaviour, are caused by changes in systematic behavioural processes, not random effects. Possible mechanisms are discussed.

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Variations à court terme des captures deCydia nigricana dans des pièges à phéromones en interaction

Résumé Des données antérieures concernant les interactions entre des pièges à phéromone alignés le long du vent ont été utilisées pour déduire les caractéristiques du comportement d'orientation deC. nigricana. Ces données ont été introduites dans un modèle de simulation quantitative qui prédisait que quand les captures totales sur une ligne ont été regroupées sur une période globale de piégage, la proportion capturée dans chaque piège devrait aussi avoir des valeurs moyennes semblables, mais varie plus largement que précédemment indiqué. Les simulations concernant des intervalles consécutifs beaucoup plus courts pendant la même période de piégage ont suggéré une forme spécifique de cette variation.Cette note signale des variations à court terme dans la proportion capturée au piège qui confirment ces prédictions. Nous montrons que sur des intervalles consécutifs brefs pendant une simple période de piégage, la proportion capturée dans le piège central d'une ligne de 3 pièges est contstante, bien que sa valeur change suivant les périodes de piégage. La proportion capturée dans le piège face au vent de 2 ou 3 lignes de pièges suit cette tendance dans le temps, ce qui est généralement bien représenté avec des courbes simples. Ces tendances changent suivant les périodes de piégage, mais des lignes de pièges fonctionnant simultanément fournissaient des résultats similaires. On suggère que ces résultats sont dus à des changements dans des processus comportementaux systématiques et non à des effects aléatoires. Les mécanismes possibles sont discutés.

     

Diapause induction in the codling moth, Cydia pomonella: effect of prediapause temperatures

The effect of four prediapause temperatures (18, 22, 26 and 30°C) on the photoperiodic response of the codling moth, Cydia pomonella (L.), was studied under controlled conditions. The highest rates of diapause were recorded, for all day-lengths, at temperatures of 22 and 26°C while relatively lower rates of diapause were elicited at 18 and 30°C. The same trend was demonstrated by projecting the values of the critical photoperiod which induces 50% diapause (=CPhP₅₀) over the prediapause temperature. The change in diapause incidence as a function of photoperiod, at all prediapause temperatures, exhibited a response characteristic of long-day insects, i.e. high rates of diapause at short days (12–13.5 h) and a decrease in diapause incidence at long days (14–15 h). The results for temperatures 22, 26 and 30°C support the view that lower prediapause temperatures enhance diapause induction, at a give photoperiod, while higher temperatures tend to avert or diminish the process. On the other hand, the low rates of diapause obtained at 18°C contradict this view. Nevertheless, high correlation was found between the laboratory evidence and field data, indicating the adaptability of the Israeli codling moth to subtropical climate.     

Control of diapause in codling moth larvae

Diapause in a New Zealand strain of codling moth (Cydia pomonella Linnaeus [Lepidoptera: Olethreutidae]) was induced in larvae by photoperiods of 15 h or less. Once diapause had been initiated, it could not be terminated by any combination of conditions tested for at least 20 days after cocooning. In diapausing larvae a low rate of pupation occurred at 25 °C under a long day (18 h) photoperiod. A high rate of pupation was achieved under a long day regime when larvae were decocooned, and provided with apple as nourishment. Diapause could be terminated predictably in 94–100% of larvae by 1) conditioning at 15 °C and constant darkness for periods of 40–100 days, then 2) chilling at 2±2 °C and constant darkness for 20–50 days followed by 3) any post-chill condition periods at 25 °C, 18 h photoperiod. Complete diapause termination was achieved when 100 days conditioning was followed by 30 days or 50 days post-chill period. Under these conditions, 76% termination occurred in the post-chill period after 10 days, and 93% after 25 days.To terminate diapause in codling moth larvae, we recommend that a 100 days conditioning followed by 30 days chilling and 50 days post chilling periods be used.     

Control efficacy of Bacillus thuringiensis and a new granulovirus isolate against Cydia pomonella in orchards

Abstract

Codling moth, Cydia pomonella, is one of the most serious pests of apple and pear worldwide. This study evaluates the efficacies of a granulovirus, a Bacillus thuringiensis (Bt) strain and their combination in the control of C. pomonella in China. A Cydia pomonella granulovirus (CpGV) was isolated from C. pomonella cadavers in an orchard in Gansu, China. Droplet-feeding bioassays showed the median lethal concentration (LC₅₀) of this CpGV isolate (CpGV-C1) against the third instar C. pomonella larvae was 770 OBs µl^?1. The LC₅₀ values of Bt C-33 and kurstaki HD-1 against the third instar larvae were 26.3 µg ml^?1 and 15.7 µg ml^?1, respectively. Field tests indicated the control efficacies of CpGV-C1 and the combination of CpGV-C1 and Bt against C. pomonella larvae in apple orchards were similar to that of beta-cypermethrin. Our data demonstrated that the combination of CpGV and Bt might effectively protect apple fruits from the damage of C. pomonella larvae and had the potential to be developed as a low-cost, highly effective insecticide.     

寄主植物挥发物对梨小食心虫受孕雌虫的引诱作用初探

梨小食心虫Grapholita molesta(Busck),是一种世界性的蛀果害虫。利用产卵选择试验研究了15种寄主植物挥发物对梨小食心虫受孕雌虫的产卵引诱活性。室内试验表明:受孕雌虫对不同挥发物的产卵选择趋性不同,其中对叶醇和己酸丁酯表现出明显的产卵选择趋性。为验证寄主挥发物对受孕雌虫的实际诱捕效果,进行了田间诱捕试验。结果发现,挥发物中己酸丁酯、苯甲腈、叶醇、E-2-己烯醛以及乙酸己酯诱捕到的雌虫均为受孕雌虫,显著高于空白对照及其他物质,其中己酸丁酯的平均诱捕量最多,苯甲腈次之,E-2-己烯醛、乙酸己酯这两种物质的平均诱捕量分别为第三、第四,叶醇的诱捕量低于乙酸己酯,其余物质的诱捕量均较低。综合室内及田间试验结果发现,寄主植物挥发物对受孕雌虫的引诱作用也随它们之间的作用距离表现出一定的差异性。