Attraction of male pear psylla, Cacopsylla pyricola, to female-infested pear shoots

Post-diapause winterform pear psylla, Cacopsylla pyricola (Förster) (Homoptera: Psyllidae), exhibit a highly clumped distribution in late winter in pear orchards. The behaviors leading to clumped distributions in this species are unknown, but could include aggregation for mating activities. Choice tests and assays with an olfactometer were done to test whether male psylla of the overwintering morphotype are attracted to pear shoots infested by post-diapause females and to shoots previously occupied by females. Paired choice tests in small arenas showed that males accumulated on pear shoots currently occupied or previously occupied by females if those shoots were paired with uninfested shoots or shoots previously occupied only by males. Assays with an olfactometer showed that males were attracted to volatile odors from female-infested or previously infested shoots. The exact source of the attractants (i.e., the female psylla, the pear shoot, or a combination of these sources) remains to be determined.     

Attraction of male winterform pear psylla to female-produced volatiles and to female extracts and evidence of male–male repellency

Pear psylla, Cacopsylla pyricola (Förster) (Homoptera: Psyllidae), is a major pest of commercial pears in North America and Europe. Olfactometer trials have shown that males of both the summer and winter morphotype are attracted to female-infested host material. Additional work with the summer morphotype has shown that males are attracted to females even in the absence of the host plant, which is evidence that female C. pyricola produce a volatile sex attractant. Here, we describe similar results with the winterform, confirming for this morphotype that the female psylla rather than the infested host material is the source of the attractant. Male winterforms displayed attraction to odors from live females in the absence of the host plant, freshly killed females, and female whole body extracts. The female whole body extracts were at least as attractive as a comparable number of live females, suggesting that we were successful at extracting the components of the attractant with this procedure. All previous olfactometer trials with C. pyricola used the insect as the attractant source; the current study is the first to demonstrate that volatile chemicals isolated from the female insect were attractive to male conspecifics. Winterform males were also assayed to odors produced by conspecific males. We found that male psylla avoided volatile odors from live males, freshly killed males, or whole body extracts of males. To our knowledge, these results are the first indication that males of any member of the Psyllidae avoid odors associated with conspecific males.     

Phenological model of pear psylla Cacopsylla pyri

A phenological model of first‐ and second‐generation pear psylla, Cacopsylla pyri L. (Homoptera: Psyllidae), was developed. The model included a time‐distributed delay and was based on authors’ observations and literature data of termination of reproductive diapause, oviposition‐period length, and developmental duration of juvenile stages depending on temperature. After calibrating microclimate, the model provided a good simulation of observations from different orchards in Switzerland and Italy over several years. The model or simulated output tables can be used to improve timing of monitoring and control measures.     

Effects of elicitors of host plant defenses on pear psylla,Cacopsylla pyricola

Pear psylla, Cacopsylla pyricola (Foerster) (Hemiptera: Psyllidae), is a key pest of cultivated pear [Pyrus communis L. (Rosaceae)] in North America and Europe. We examined the effects of foliar applications of three commercially available chemical elicitors of host‐plant defenses — Actigard (acibenzolar‐S‐methyl), Employ (harpin protein), and ODC (chitosan) — on survival, development, feeding, and egg laying of C. pyricola. All three defense elicitors reduced the number of nymphs present on pear (cvs. Bartlett or D'Anjou) 30 days after releasing 10 adults on the trees. Choice assays showed that females settled and oviposited on untreated trees more often than on trees treated with any of the three defense elicitors. Results of no‐choice assays confirmed that the effects of Actigard, Employ, and ODC on C. pyricola were due to activation of systemic plant responses that led to reduced oviposition preference and nymph survival. However, results did not provide evidence that plant responses to elicitors led to reduced nymphal feeding rates or development. Results of our laboratory studies suggest that commercial defense elicitors may be useful in the integrated management of pear psylla once the effects of elicitors at an ecological scale are better understood.     

Mate finding in the forest cockchafer, Melolontha hippocastani, mediated by volatiles from plants and females

The response of the forest cockchafer, Melolontha hippocastani F. (Coleoptera, Scarabaeidae), towards volatiles emitted by different host plants and conspecifics was tested in field experiments during the flight period at dusk. Funnel traps containing artificially damaged leaves from the host plants Carpinus betulus L. and Quercus rubra L., as well as from the non‐host plant Prunus serotina Ehrh. caught significantly more beetles than empty control traps. On the other hand, traps baited with undamaged leaves from Q. rubra did not catch significantly more beetles than empty controls. Leaves from C. betulus damaged by beetle feeding did not attract more beetles than artificially damaged leaves. By use of gas chromatography coupled with electroantennographic detection (GC‐EAD) electrophysiological responses of males and females were shown for 18 typical plant volatiles. A synthetic mixture of selected typical green plant volatiles was also highly attractive in the field. A total of 9982 beetles was caught during the field experiments, among them only 33 females. This suggests that attraction to damaged foliage during flight period at dusk is male‐specific. Field experiments testing the attractiveness of female M. hippocastani towards conspecific males by employing caged beetles and beetle extracts indicated that males of M. hippocastani use a female‐derived sex pheromone for mate location. On wired cages containing either unmated feeding females, or unmated females without access to foliage, or feeding males in combination with extracts from unmated females, significantly more males landed during the flight period than on comparable control cages containing feeding males or male extracts. A possible scenario of mate location in M. hippocastani involving feeding‐induced plant volatiles and a female‐derived sex pheromone is discussed.     

Specificity of sex pheromones, the role of host plant odour in the olfactory attraction of males, and mate recognition in the aphid Cryptomyzus

Abstract. Choice tests in an olfactometer showed that males of the aphid Cryptomyzus galeopsidis spent more time in the odour of conspecific females than of a sibling species or a more distantly related Cryptomyzus species, which all co-occur on red currant. Analysis of the pheromone-emissions of females showed the presence of a nepetalactol and a nepetalactone, two known aphid sex pheromone components. However, no interspecific difference in the ratio of the components ( c. 30:1) was found, and this ratio did not change as the females aged. Males were only slightly attracted by a synthetic 30:1 mixture of these two components, and in a choice test preferreď the odour of conspecific females. The sex pheromone of Cryptomyzus spp. must thus consist of more than two components, the first time this has been reported for aphids. Host plant odour did not attract males or enhance the activity of the pheromone.     

Fungal,host and non-host volatiles modify attraction of the walnut twig beetle,Pityophthorus juglandis,to pheromone lures

1. Thousand Cankers Disease (TCD) of walnut trees is caused by the pathogenic fungus Geosmithia morbida vectored by the walnut twig beetle (WTB) Pityophthorus juglandis. Monitoring efforts for WTB rely on pheromone-baited traps, but lures are likely effective at attracting beetles only over short distances. Fungal-derived kairomones may increase the efficacy of current lures, while additional volatiles may repel beetles from valuable trees.
2. The objective of this study was to determine the extent to which fungal, host and non-host volatiles modify the attraction of WTB to pheromone-baited traps. A trapping study that combined fungal, host-associated and non-host compounds with WTB-pheromone lures was conducted over three years in black walnut plantations experiencing a TCD outbreak in Walla Walla, WA.
3. Traps baited with pheromone and G. morbida volatiles (i.e., isoamyl and isobutyl alcohol) consistently attracted more WTB, while other fungal volatiles inconsistently increased attraction compared to those baited with pheromone lure alone. This is the first field study that demonstrates fungal volatiles can increase the attraction of a bark beetle to its pheromone in a hardwood system.
4. One fungal (benzyl alcohol) and two additional volatiles (limonene, piperitone) repelled WTB from pheromone-baited traps. Although limonene is known to repel WTB, this is the first demonstration that benzyl alcohol and piperitone repel a bark beetle.
5. Fungal volatiles may increase the efficacy of monitoring efforts and may play an important role in management tactics for WTB, especially in detecting the introduction and establishment of nascent populations and protecting trees from colonizing beetles.

     

Behavioural responses of the aphid parasitoid Diaeretiella rapae to volatiles from Arabidopsis thaliana induced by Myzus persicae

In response to herbivory by insects, several plant species have been shown to produce volatiles that attract the natural enemies of those herbivores. Using a Y‐tube olfactometer, we investigated responses of the aphid parasitoid Diaeretiella rapae MacIntosh (Hymenoptera: Aphidiidae) to volatiles from Arabidopsis thaliana Columbia (Brassicaceae) plants that were either undamaged, infested by the peach‐potato aphid, Myzus persicae Sulzer (Homoptera: Aphididae), or mechanically damaged, as well as to volatiles from just the aphid or its honeydew. In dual‐choice experiments, female D. rapae given oviposition experience on A. thaliana infested with M. persicae were significantly attracted to volatiles from A. thaliana infested with M. persicae over volatiles from undamaged A. thaliana and similarly were significantly attracted to plants that had been previously infested by M. persicae, but from which the aphids were removed, over undamaged plants. Diaeretiella rapae did not respond to volatiles from M. persicae alone, their honeydew, or plants mechanically damaged with either a pin or scissors. We conclude that an interaction between the plant and the aphid induces A. thaliana to produce volatiles, which D. rapae can learn and respond to. Poor responses of D. rapae to volatiles from an A. thaliana plant that had two leaves infested with M. persicae, with the two infested leaves being removed before testing, suggested the possibility that, at this stage of infestation, the majority of volatile production induced by M. persicae may be localized to the infested tissues of the plant. We conclude that this tritrophic interaction is a suitable model system for future investigations of the biochemical pathways involved in the production of aphid‐induced volatiles attractive to natural enemies.     

Conditioned olfactory responses of a predatory mite, Neoseiulus womersleyi, to volatiles from prey-infested plants

To clarify the prey‐finding behavior of the predatory mite Neoseiulus womersleyi (Schicha) (Acari: Phytoseiidae), we studied its olfactory responses to volatiles from the prey‐infested plant on which the mites had been collected. We used a local N. womersleyi population called Kanaya collected from tea (Camellia sinensis L.) (Theaceae) plants infested by Tetranychus kanzawai Kishida (Acari: Tetranychidae) in Kanaya City, Japan. Neoseiulus womersleyi (Kanaya population) were more attracted to volatiles from tea plants infested with five female T. kanzawai per leaf for 7 days than to intact tea leaves in a Y‐tube olfactometer. Tetranychus kanzawai‐induced tea leaf volatiles were identified as (E)‐β‐ocimene, (E)‐4,8‐dimethyl‐1,3,7‐nonatriene, and (E,E)‐α‐farnesene. As olfactory responses are known to differ among local populations of N. womersleyi, we compared the responses of the Kanaya population with those of a Kikugawa population collected from tea plants infested by T. kanzawai in Kikugawa City. To test the influence of previous predation experience, we reared the two populations on tea plants infested by T. kanzawai or on kidney bean plants (Phaseolus vulgaris) infested by Tetranychus urticae Koch. The Kanaya population was more attracted to the volatiles from infested plants on which they had been reared. Because the Kanaya population was not attracted to the plant volatiles they had not previously experienced, the positive response to previously experienced volatiles might be the result of learning. By contrast, the Kikugawa population showed no preference for previously experienced volatiles from infested plants. The implications of this flexibility in foraging behavior are discussed.     

褛裳夜蛾的交配行为及雄蛾对性腺提取物的反应节律

详细观察了褛裳夜蛾成虫的交配行为,利用风洞、触角电位技术研究了雄蛾对性腺提取物的反应节律,通过林间诱蛾试验进行了验证,旨在为褛裳夜蛾性信息素的精确提取及性信息素组份分离、鉴定提供依据。研究结果表明:成虫的求偶、交配行为均发生在暗期,有一定的节律性:雌蛾在羽化3d以后开始求偶,1周左右表现最为强烈,3-4日龄雌蛾在暗期4-6h开始求偶,最大求偶率在暗期6-8h;5-9日龄在进入暗期就开始求偶,最大求偶率出现在暗期4-6h。风洞试验表明,3-7日龄的雄蛾对性腺提取物均有明显的性行为反应,5日龄雄蛾在暗期4-6h对性腺提取物的反应最为强烈。3-6日龄的成虫在暗期4-6h开始交配,而7-8日龄的成虫于暗期2-4h开始交配,6日龄的成虫交配率最高,交配高峰在暗期4-8h。雄蛾对性腺提取物的触角电位反应也有一定的节律性:雄蛾对4日龄雌蛾性腺提取物开始有电生理反应,对6-7日龄暗期5h性腺提取物反应最为强烈。林间诱蛾试验测定了性腺提取物的引诱活性,7日龄雌蛾性腺提取物林间诱蛾量最高,引诱高峰在暗期4-6h,该结果也验证了褛裳夜蛾雄蛾对性腺提取物的反应节律。     

Phosphorus export from roots to shoots of barley, buckwheat and rape seedlings with different P status

Seedlings of barley (Hordeum vulgare L. cvs Salka and Zita), buckwheat (Fagopyrum esculentum Moench) and rape (Brassica napus L. ssp. napus cv. Line) were grown in complete nutrient solutions with 8 or 10 different P concentrations in the range of 0–2 mM. Phosphate export from roots to shoots was determined from the amount of ³²P (or ³³P) absorbed and exported to shoots in 1 h from a nutrient solution containing 0.1 mM radiolabelled phosphate. P export was also determined in the presence of a metabolic uncoupler (DNP, 2.4-dinitrophenol) and a protein synthesis inhibitor (CH, cycloheximide). Phosphorus export from roots to shoots reached a maximum at a certain optimum level of phosphorus in shoots and roots, and decreased at both higher and lower P levels. Maxinmm P export was 1.7 ± 0.2 and 4.5 ± 0.5 (mean ±se of the three species) times higher than the P export at the lowest and highest [P]_root, respectively. Hill plots as well as plots of the untransformed decreasing P export vs root or shoot P concentrations above the optimum were linear and had high correlation coefficients. The Hill coefficient (n_H) based on [P]_root, was —7.7 for barley cv. Salka and varied between -3.8 and -4.5 for the other species. Based on [P]_shootot n_H was—16.1 for barley cv. Salka, -3.7 for barley cv. Zita and -6.4 for the two dicotyledonous species. Relative to the amount of P simultaneously absorbed by the root system, the import of P per unit shoot weight decreased linearly over the whole range of shoot P concentrations in the dicotyledonous species. In contrast, the relative import of P per unit shoot weight of the two barley cultivars increased at low levels of [P]_shoot and decreased at higher levels. DNP and CH almost eliminated P export from roots to shoots of seedlings with low or high P status. In seedlings with medium P status only 60 to 75% of the P export was affected.     

Orientation of males of sorghum midge,Contarinia sorghicola to sex pheromones from virgin females in the field

The orientation of males of the sorghum midge,Contarinia sorghicola Coq. (Diptera: Cecidomyiidae) towards virgin female baited sticky traps was studied in the field. Male response increased linearly with an increase in the number of virgin females in the sticky traps. Five females per vial were optimum for monitoring midge populations in the field. Numbers of males trapped were significantly greater in traps placed at 0.5 and 1.5 m above ground level compared with those placed at 2.5 m. Peak trap catches occurred at 0900 h. The number of males trapped decreased significantly after 1400 h; male catches continued till sunset. Trap catches followed the same pattern as the number of ovipositing females on sorghum panicles at the half-anthesis stage. Midge activity decreased with an increase in temperature and a decrease in relative humidity. Peak midge density was observed during the second fortnight of October in the rainy season and during February-March in the post-rainy season. Sex pheromones can be used to monitor midge population dynamics for integrated pest management and to screen for host plant resistance to this insect.