Comparative analysis of peach and pear fruit volatiles attractive to the oriental fruit moth,Cydia molesta

Cydia molesta is an important pest of peach and pear fruits late in growing season. We identified and quantified volatiles from immature and mature fruits of peach and pear using gas chromatography-mass spectrometry. Antennally, active compounds were identified by gas chromatography-electroantennogram detection and were further tested in the field. Consistent electroantennographic activity was obtained for nine compounds from headspace collections of the mature fruits of two peach and two pear varieties. Esters were the major components, but qualitative and quantitative differences were found among four odor profiles. Blends mimicking pear fruit volatiles were more attractive to both sexes than blends mimicking peach fruit volatiles in both orchards. Our finding indicated that mixtures mimicking peach and pear fruit volatiles attracted both females and males of C. molesta, and these host volatiles may also be involved in the host switch behavior from peach to pear in mid-late season.     

果实种类及发育阶段对梨小食心虫幼虫钻蛀率和蛹重的影响

【目的】明确梨小食心虫Grapholitha molesta在寄主果实上的钻蛀率和蛹重与寄主种类和果实发育阶段的关系,为其田间预测预报和综合防控提供技术依据。【方法】在室内条件下测定了接卵后72 h梨小食心虫初孵幼虫在不同发育阶段的3个种共6个品种水果［苹果Malus pumila (嘎啦苹果), 桃Amygdalus persica (大久保毛桃、丰白毛桃和霞光油桃), 梨Pyrus bretschneideri (砀山酥梨和玉露香梨)］果实上的钻蛀率以及在不同果实状态的4个水果品种(大久保毛桃、丰白毛桃、砀山酥梨和玉露香梨)果实上72 h的钻蛀率;比较了接卵后24 h和72 h初孵幼虫在不同发育阶段的3个苹果品种(嘎啦苹果、富士苹果和金冠苹果)果实上的钻蛀率;并测定了不同发育阶段的金冠苹果、富士苹果、嘎啦苹果、砀山酥梨和丰白毛桃上的梨小食心虫蛹重。【结果】接卵后72 h梨小食心虫初孵幼虫在6个不同水果品种果实上的钻蛀率从高到低依次为：霞光油桃＞嘎啦苹果＞砀山酥梨＞玉露香梨＞大久保毛桃＞丰白毛桃;除霞光油桃外,其他5个水果品种果实的发育阶段显著影响初孵幼虫钻蛀率。对于嘎啦苹果,接卵后72 h初孵幼虫在其幼果上的钻蛀率最高(73.69%),在其着色期果实上钻蛀率最低(32.51%);在大久保毛桃、丰白毛桃、砀山酥梨和玉露香梨上,接卵后72 h初孵幼虫的钻蛀率均随果实生长发育而增加。初孵幼虫在3 个苹果品种着色期和成熟期果实上的钻蛀率随处理时间的增加而显著下降,而在其幼果上变化不显著。寄主种类及其发育阶段也显著影响梨小食心虫蛹重,成熟毛桃和梨饲养的雌、雄蛹重显著高于未成熟果实饲养的蛹重,着色期苹果不利于蛹重的增加。【结论】果实种类及发育阶段显著影响梨小食心虫初孵幼虫钻蛀率和蛹重,取食成熟期梨和桃的梨小食心虫初孵幼虫钻蛀率和蛹重显著高于取食未成熟果实的个体。     

Interaction of a solitary larval endoparasitoid, Microplitis mediator, with its host, Mamestra brassicae: host acceptance and host suitability

Abstract:  Microplitis mediator (Haliday) (Hym., Braconidae) is an important parasitoid of early instar larvae of the European cabbage moth, Mamestra brassicae L. (Lep., Noctuidae). In the laboratory, we examined attack responses of female M. mediator to the first three larval instars of M. brassicae . Females were presented with M. brassicae larvae either one individual at a time in a no-choice experiment, or three individuals, one from each instar, simultaneously in a choice experiment. Whether or not there was choice, naïve female parasitoids attacked a high proportion of larvae and did not discriminate among instars. In the no-choice experiment, attacked larvae were reared, and parasitoid cocoons were produced from about 76% of larvae attacked as first and second instars, but from only 19% of larvae attacked as third instars. Dissections of attacked larvae from the choice experiment showed that about 79% of attacks on first and second instars resulted in oviposition compared with only 49% for third instars. When given choice, frequency and number of attacks on first instar larvae increased with increasing parasitoid experience. Our results suggest that first and second instar larvae of M. brassicae are suitable hosts for M. mediator , but that third instar larvae are suboptimal both because oviposition attempts were frequently unsuccessful and because immature parasitoids failed to complete development. Nevertheless, naïve attacking parasitoids exhibited minimal discrimination among instars, although experienced parasitoids most frequently attacked first instar larvae. The host selection behaviour of M. mediator is discussed in the context of optimal foraging theory and implications for biological control.     

Olfactory responses of Grapholita molesta to different developmental stages of immature fruit of peach,plum, and apple

The Oriental fruit moth, Grapholita molesta (Busck) (Lepidoptera: Tortricidae), is known to shift its host use from stone fruits (the primary hosts) to pome fruits (secondary hosts) as the season progresses. Grapholita molesta recognizes potential hosts by semiochemicals from fruits, but few studies have addressed the olfactory responses of G. molesta to host fruits during the seasonal transition of the moth from stone to pome fruits. So, we investigated the olfactory responses of larvae and gravid females of G. molesta to different fruit stages (collected on May 31, June 11, and June 25) of immature peach, plum, and apple fruits, using both multiple and two choice tests. In the multiple choice tests, for fruits collected after June 11, larvae showed a significant preference for peach as their first choice, compared to plum or apple. The final choice rate (when larvae had stayed on the fruit for more than 1 h) of larvae was also highest for peach fruits collected on June 11 and June 25. In two choice tests (Y-tube test), the response rate and overall choice rate of larvae and mated ovipositing adult females were also highest on peaches collected on May 31 (larvae) and June 25 (adults), respectively. In conclusion, we found that both the adults and larvae of G. molesta were highly attracted to immature peach fruits in laboratory choice tests.     

A comparison of the host preference of monarch butterflies (Danaus plexippus) for milkweed (Asclepias syriaca) over dog-strangler vine (Vincetoxicum rossicum)

Observations in the field indicate that monarch butterflies will oviposit on dog‐strangler vine, an invasive introduced species in the same family as milkweed (Asclepias spp.), the principal larval host of monarchs. The potential impact of this behaviour depends on the strength of the preference of monarch adults to oviposit on these two hosts and the relative ability of larvae to survive on each. We determined the preference for milkweed vs. dog‐strangler vine of ovipositing adults and first instar larvae in choice and no‐choice tests. We also compared the ability of larvae to consume, develop, and survive on either host. In the presence of both hosts, adults exhibited a strong preference to oviposit on milkweed over dog‐strangler vine (mean 80.7 eggs compared to 0.4 eggs over 48 h, respectively). In the absence of milkweed, adults ceased oviposition (mean 0.9 eggs in 48 h), but resumed oviposition when the dog‐strangler vine was replaced with milkweed (mean 99.1 eggs in 48 h). Given a choice between hosts over 24 h, 92% of larvae moved to milkweed leaves and consumed 3.94 cm² of milkweed leaves compared to 2% of larvae that moved to dog‐strangler vine and consumed negligible amounts of leaf material (0.01 cm²). Without a choice, larvae on dog‐strangler vine never consumed more than mean 0.02 cm² larva^?1 in a 24‐h period, did not develop beyond the first instar, and died within 96 h. We obtained no data in support of an effect of the presence of dog‐strangler vine on monarch butterfly populations.     

Oviposition preference in the oligophagous tomato fruit fly, Neoceratitis cyanescens

We assessed the role of visual and olfactory cues on oviposition preference in the oligophagous tomato fruit fly, Neoceratitis cyanescens (Bezzi) (Diptera: Tephritidae). In a field survey, we evaluated the stage of susceptibility of field‐grown tomatoes by monitoring N. cyanescens infestations from fruit‐setting up to harvest, in relation to post‐flowering time, size, and visual properties of fruit. In two‐choice laboratory experiments, we tested the degree to which females use visual and olfactory cues to select their host plant for oviposition. In addition, we investigated the ability of flies to avoid fruit already infested by conspecific eggs or larvae, and the influence of natal host fruit on oviposition preference. Neoceratitis cyanescens females preferentially lay their eggs in small yellow‐green unripe fruit (2–3.5 cm diameter, 10–21 days post‐flowering). Damage to fruit was significantly affected by brightness and size properties. In laboratory experiments, females chose to lay their eggs in bright orange rather than yellow domes. On the sole basis of olfactory stimuli, females showed a significant preference for unripe vs. ripe host fruit, for unripe fruit vs. flowers or leaves, and for host vs. non‐host fruit (or control). However, colour interacted with odour as females dispatched their eggs equally between the yellow dome and the bright orange dome when unripe fruit of tomato was placed under the yellow dome vs. ripe fruit under the bright orange dome. When offered real ripe and unripe tomatoes, females preferred unripe tomatoes. Females significantly chose to lay eggs in non‐infested fruit when they were given the choice between these or fruit infested with larvae. In contrast, recent stings containing eggs did not deter females from laying eggs. Rather, they could have an attractive effect when deposited within <1 h. Regardless of their natal host plant, tomato or bugweed, N. cyanescens females laid significantly more eggs in a dome containing bugweed fruit. However, 15% of females originating from tomato laid eggs exclusively in the dome with tomato, against 3% of females originating from bugweed.     

Host-marking by female pepper weevils, Anthonomus eugenii

Pepper weevils, Anthonomus eugenii Cano (Coleoptera: Curculionidae), feed and oviposit in flower buds and small fruits of plants in the genus Capsicum, as well as several species of Solanum (Solanaceae). Females chew a small hole into the fruit, deposit a single egg within the cavity, and seal the hole with a clear anal secretion that hardens into an ‘oviposition plug’. Female oviposition behavior was studied in a series of small‐arena bioassays to determine whether previous oviposition in Jalapeño pepper fruit deterred subsequent oviposition and to determine what specific cues from an infested fruit influence female behavior. In choice and no‐choice tests, females preferred clean fruit to fruit that had received four eggs 24 h previously (i.e., infested fruit), whether the fruit was infested with conspecific eggs or their own eggs. Further bioassays demonstrated that the presence of female frass, or oviposition plugs alone, in the absence of eggs or any fruit damage, was sufficient to deter oviposition. In addition, females given the choice between an infested fruit with the oviposition plug removed or an unaltered infested fruit preferred the fruit with no plugs, even when eggs, frass, and feeding damage were still present. To determine whether females would avoid infested peppers under more natural conditions, we quantified oviposition on infested and uninfested sentinel pepper fruit within individually caged plants and on clean and infested plants caged together. Females consistently laid more eggs on clean fruit than on infested fruits and moved within and among pepper plants to search for more acceptable oviposition sites. We conclude that oviposition plugs, along with contaminated female, but not male, frass contain a deterrent that, in the absence of any other cue, is enough to alert a female that a patch is occupied.     

梨小食心虫的产卵选择性

为了准确掌握梨小食心虫的产卵特性,研究模拟室外条件下该虫在不同寄主果树的叶片、桃枝不同部位及不同品种桃果上的产卵偏好.结果表明: 梨小食心虫成虫对7种寄主果树叶片的产卵偏好由高至低依次为:桃＞樱桃＞苹果＞李＞梨＞海棠＞杏.在桃树叶片上的产卵量占总产卵量的33.5%,平均单叶卵量达8.3粒;虫卵在不同寄主叶片正、反两面的分布有所差异,苹果和海棠叶片正面卵量多于背面,桃、李、梨、杏叶背面卵量多于正面,桃叶背面卵量是正面的3.3倍,樱桃叶两面卵量差异不明显;该虫在桃枝上产卵部位选择顺序为:叶片＞托叶＞叶柄＞枝条,叶片是其主要产卵部位,占总产卵量的88.7%;梨小食心虫在桃枝上主要选择靠近顶端未展叶的前10片桃叶背面产卵,前10叶卵量占总产卵量的725%,其中第3片叶上产卵最多,占9.3%;第25叶以后仅占总产卵量的1.1%;在不同类型桃果上的产卵偏好次序为:油桃＞蟠桃＞毛桃;绒毛疏密及其特点是影响梨小食心虫在寄主果树叶片和果实上产卵选择的首要因素.     

Flight Tunnel Responses of Diachasmimorpha longicaudata (Ashmead) (Hymenoptera: Braconidae) to Olfactory and Visual Stimuli

Cohorts of mass-reared, naive Diachasmimorpha longicaudata, parasitoids of tephritid fruit flies, were released in a laminar airflow wind tunnel to study their responses to visual and olfactory stimuli associated with their host habitat. Parasitoids were five times more likely to land on yellow plastic spheres emitting the odor of ripe, guava fruit (Psidium guajava L.) than to spheres emitting clean air. The rate of landing was not modified by the presence of green artificial leaves adjacent to the spheres in the tunnel or by the inclusion of green leaf volatiles emanating with the guava odors. However, hovering activity was twice as frequent around spheres adjacent to artificial leaves than around isolated spheres. Oviposition activity on spheres emitting guava odor was not affected by the presence of artificial leaves nor by green leaf volatiles. This suggests that inexperienced D. longicaudata may be instinctively attracted to foliage and to fruit odor but that landing (arrestment) and oviposition are influenced more by odor than by the appearance of fruit or foliage. D. longicaudata are not instinctively attracted to larvae of Bactrocera dorsalis in the absence of host-habitat stimuli. More wasp activity occurred around oviposition units containing larvae if the odor of ripe/overripe guava was present. Successful wasp reproduction occurred only in units with guava odor.     

What Do Mexican Fruit Flies Learn When They Experience Fruit?

Mexican fruit flies learn fruit characteristics that enable them to distinguish familiar fruits from novel fruits. We investigated whether mature Mexican fruit flies learn fruit color, size or odor. We found no evidence that female flies learn fruit color or size after experience with host fruit, including oviposition. However, green fruit and fruit models were more attractive than yellow and red fruit and fruit models regardless of previous experience. Females with grapefruit experience were more attracted to fruit models with extract of either grapefruit peel or pulp, than to models without extract. Females with no experience with grapefruit were not attracted to models treated with grapefruit extract. These results indicate that females learned fruit odor during exposure to grapefruit.     

Induction of volatile emissions from ripening apple fruits infested with Cydia pomonella and the attraction of adult females

We studied the effect of herbivory by Cydia pomonella L. (Lepidoptera: Tortricidae) first instar larvae on the volatile emissions from immature apples collected at the end of August. Volatiles from infested, artificially damaged, and healthy fruit were collected using solid-phase microextraction and analysed using combined gas chromatography mass spectrometry. The results show that neonate C. pomonella larvae induce the release of E--ocimene from immature fruit compared to healthy or artificially damaged fruit. Seven further compounds, a terpene, an alcohol, four aldehydes, and a ketone, were consistently found in all treatments. There were no significant differences amongst these latter compounds, although the amount of the terpene E,E--farnesene was three to five times higher from the infested as compared to healthy fruits. Headspace volatiles were also collected on Tenax to test for behavioural responses to the volatiles. Volatile collections from infested fruit attracted mated adult females in a Y-tube olfactometer, whereas no preference was evinced for volatiles from healthy or artificially damaged fruits when compared to a solvent control.     

Infestation of coconut fruits by Aceria guerreronis enhances the pest status of the coconut moth Atheloca subrufella

The coconut mite, Aceria guerreronis (Acari: Eriophyidae) and the coconut moth, Atheloca subrufella (Lepidoptera: Phycitidae), exploit the same habitat—meristematic region underneath the coconut fruit perianth. The coconut fruit perianth, however, is a tight structure allowing free colonisation of the meristematic region of the fruit only by small arthropods such as the eriophyid and tarsonemid mites. Fruits infested by the mites develop different levels of necrosis around the perianth providing access to colonising larvae of the coconut moth, which bore the fruit under the perianth resulting in fruit abortion. Based on field observations, we hypothesise that A. subrufella will colonise coconut fruits only if they exhibit damage on the perianth such as the necrosis caused by the coconut mite. Fruits with and without necrosis were collected from different production areas located in three different states along the Brazilian Atlantic coast and inspected for infestation with coconut moth larvae. In the laboratory, coconut fruits with and without necrosis were offered to moths for oviposition preference and tested for colonisation by neonate and third instar larvae. The results showed that the moths showed no preference for fruits with or without necrosis for oviposition and, hence, neonate larvae have to go under the perianth bract to reach the meristematic region of the fruit. However, neonate larvae were unable to colonise fruits without necrosis (0%) compared to 23% and 60% of fruit colonisation success when exhibiting mite necrosis or mechanical damage, respectively. Similar results were found with respect to older coconut moth larvae. Thus, the data support the hypothesis that the indirect interaction through previous fruit colonisation and necrosis caused by the coconut mite allows the larvae of A. subrufella to be a key pest of coconut fruits.     

Is fruit size important in the selection of oviposition sites by cranberry fruitworm,Acrobasis vaccinii?

Under laboratory conditions, females of Acrobasis vaccinii (Riley) (Lepidoptera: Pyralidae) oviposit significantly more often on larger than on smaller cranberry fruit. This behaviour ensures that neonate larvae have access to maximum resources and are larger when moving to the next fruit. However, while there is some evidence that on a large spatial scale females may lay eggs in patches of larger fruit, there was no evidence of such an oviposition preference within patches in natural bogs. These results may be explained by the fact that the oviposition period for A. vaccinii begins early in the cranberry season, before fructification is completed, leading to potential competition among females for the first fruit present in the environment. Laying eggs on the first fruit available may be advantageous as this behaviour increases the probability that females select unexploited fruit. This strategy would be particularly effective for maximizing female fitness in grazer frugivorous species (such as the cranberry fruitworm) that live in environments where severe climatic conditions induce limited flowering/fruit formation and where hosts thus are rare.     

Apple and peach fruit volatiles and the apple constituent butyl hexanoate attract female oriental fruit moth, Cydia molesta, in the laboratory

Volatiles emitted from immature and mature peach and apple fruits were all attractive to mated female oriental fruit moth, Cydia molesta (Busck), in a dual choice arena. Females did not discriminate between odours emitted by these two major host plants. The same natural blends were behaviourally ineffective for virgin females. A major component of apple fruit volatiles, butyl hexanoate, also attracted female C. molesta. Mated females were attracted to two medium dosages, while virgin females responded positively to the lowest of the five dosages tested. The time course of the captures of the moths shows a diurnal activity cycle known from the field. The possible implications of a semiochemical which attracts females are discussed in the context of previous findings that gravid females may immigrate from peaches into apple orchards particularly in the later phase of the season.     

Gregarious development of the solitary endo-parasitoid, Microplitis rufiventris in its habitual host, Spodoptera littoralis

Abstract:  Earlier research has shown that the koinobiont parasitoid, Microplitis rufiventris , attacks and can develop on early instars of Spodoptera littoralis larvae with preference to third instars. However, the present study was carried out using the newly moulted sixth instar larvae at two different temperatures (20 ± 1 and 27 ± 1°C) to study the developmental interaction between the parasitoid and the last instar host larvae. Parasitoid eggs laid in singly parasitized host larvae invariably died. As the number of parasitoid eggs/host larvae increased, the proportion of eggs that hatched and number of viable parasitoid larvae successfully reached to their final instar increased. The effect of superparasitization seems to be dose (no. of eggs + parasitoid factors)-temperature-dependent. The results demonstrate a kind of 'Allee effect' suggesting that superparasitized last instar S. littoralis larvae provide a better host environment than singly parasitized hosts for the parasitoid, M. rufiventris . This may be due to host's hormone and/or low dose of factors injected with parasitoid eggs. The supernumerary individuals of wasp larvae developed normally to the point of emergence but most did not successfully emerge from the host. The improvement of both hatchability and post-embryonic development of parasitoid wasp was significantly (P < 0.01) greater at 20°C than at 27°C. The results of the present study are useful in understanding the evolution of life-history strategies and host range in parasitic hymenoptera.     

Chemical stimuli from corn plants affect host selection and oviposition behavior of Sesamia nonagrioides (Lepidoptera: Noctuidae)

The role of chemical stimuli in host selection and oviposition of Sesamia nonagrioides (Lef) was studied in the laboratory using eight corn hybrids. Female oviposition preference was evaluated on plants of the eight hybrids, their extracts in pentane and methanol, and volatiles collected by steam distillation in ether. Results from two-choice bioassays indicate various degrees of female preference to the hybrids. Four hybrids received more eggs than control plants, whereas the remainder received fewer eggs. Relatively similar results were obtained when filter paper sticks baited with pentane and steam distillation extracts were evaluated. Methanol extracts from all eight hybrids received fewer eggs than the methanol controls. Results showed that pentane and steam distillation extracts contain chemicals that elicit female oviposition response, while methanol extracts may contain chemicals that deter or repel females to oviposition.     

Electrophysiological and behavioral response of the oriental fruit moth <Emphasis Type="Italic">Grapholita</Emphasis><Emphasis Type="Italic">molesta</Emphasis> (Busck, 1916) (Lepidoptera: Tortricidae) to the volatiles of apple fruits at different stages of development

The oriental fruit moth, Grapholita molesta, occurs in Southern Brazil throughout the year, and migrates from peach to apple orchards. Because moths rely on volatile organic compounds (VOCs) during the host-location process, variations in the emission of these compounds during fruit maturation can influence the time of infestation and preference of the moths for a particular genotype. The aim of this work was to identify VOCs emitted by the apples “Eva” and “Gala” at different stages of development and to determine the behavioral and electrophysiological responses of G. molesta to these compounds. For this purpose, VOCs from immature, maturing, and mature fruits of both cultivars were collected and analyzed by gas chromatography and gas chromatography-mass spectroscopy. The response of the antennae of virgin males and females and mated females to volatiles released by the three fruit stages was registered by gas chromatography coupled to an electroantennography. A dual-choice behavioral test for the different combinations of insect groups and fruit stage was also performed. Amongst the volatiles released by mature fruits, twelve compounds elicited a response. The antennae of the oriental fruit moth did respond to isoamyl hexanoate and α-farnesene emitted by “Eva” maturing fruits. In general, virgin females did not respond to volatiles in olfactometer bioassays and mated females were attracted to volatiles released by mature fruits. Our results show that the variation in the emission during the maturation of fruits can influence the orientation of G. molesta.     

Oviposition behaviour of two tephritid fruit flies,Dacus tryoni and Dacus jarvisi,as influenced by the presence of larvae in the host fruit

Summary When offered a choice, females of the fruit flies Dacus tryoni (Frogg.) and D. jarvisi (Tryon) strongly preferred to lay in fruits without larvae rather than fruits which already contained larvae. Fruits which contained even low densities of larvae, including newly hatched ones, received many fewer eggs than control fruits. This preference was not influenced by the species of larvae present in the fruits nor by the distance to uninfested fruits. Discrimination occurred when fruits with and without larvae were close together (10 cm apart) and also when they were separated by distances of about one metre. Laboratory assays suggested that the flies detect chemical changes in the fruit associated with the decomposition which accompanies larval feeding, but they do not seem to detect the larvae Perse. This behaviour may be significant when these two species utilise the same host since the species which is able to infest fruits first will reduce the availability of hosts for the other species. In contrast to many other Tephritids (e.g. Rhagoletis, Anastrepha and Ceratitis) female Dacus don't discriminate against fruits which contain eggs nor do they deposit a pheromone to deter oviposition by females that subsequently visit the fruit. An hypothesis is proposed to explain the absence of oviposition-deterring pheromones in Dacus, and their presence in many other species of Tephritidae, on the basis of differences in life history and population structure.     

梨小食心虫的产卵选择性

为了准确掌握梨小食心虫的产卵特性,研究模拟室外条件下该虫在不同寄主果树的叶片、桃枝不同部位及不同品种桃果上的产卵偏好.结果表明: 梨小食心虫成虫对7种寄主果树叶片的产卵偏好由高至低依次为:桃＞樱桃＞苹果＞李＞梨＞海棠＞杏.在桃树叶片上的产卵量占总产卵量的33.5%,平均单叶卵量达8.3粒;虫卵在不同寄主叶片正、反两面的分布有所差异,苹果和海棠叶片正面卵量多于背面,桃、李、梨、杏叶背面卵量多于正面,桃叶背面卵量是正面的3.3倍,樱桃叶两面卵量差异不明显;该虫在桃枝上产卵部位选择顺序为:叶片＞托叶＞叶柄＞枝条,叶片是其主要产卵部位,占总产卵量的88.7%;梨小食心虫在桃枝上主要选择靠近顶端未展叶的前10片桃叶背面产卵,前10叶卵量占总产卵量的725%,其中第3片叶上产卵最多,占9.3%;第25叶以后仅占总产卵量的1.1%;在不同类型桃果上的产卵偏好次序为:油桃＞蟠桃＞毛桃;绒毛疏密及其特点是影响梨小食心虫在寄主果树叶片和果实上产卵选择的首要因素.     

寄主植物对桃蛀螟生长发育及产卵选择行为的影响

为明确寄主植物对桃蛀螟生长发育及产卵选择行为的影响,利用实验种群生命表和二项产卵选择试验,研究了玉米、大豆、棉花和桃等4种寄主植物对桃蛀螟种群生长发育及产卵选择性的影响。结果表明:取食棉花的桃蛀螟幼虫存活率最低、幼虫历期最长,取食玉米的幼虫存活率最高、幼虫历期最短,取食桃和大豆的幼虫存活率和历期居于棉花处理组和玉米处理组之间;玉米处理组的桃蛀螟化蛹率、蛹重和蛹历期均为最高,棉花处理组为最低,大豆和桃处理组的这些参数均显著小于玉米处理组而大于棉花处理组;发育至成虫后,取食玉米的桃蛀螟羽化率显著高于其他3个处理组;取食桃的桃蛀螟成虫寿命(雌虫和雄虫)及个体发育历期均显著高于其他3种处理组;同时取食桃的桃蛀螟单雌产卵量最高,其次是玉米处理组,两者均显著高于大豆和棉花处理组。二项产卵选择试验结果显示,桃蛀螟雌蛾在棉花和玉米处理组、玉米和大豆处理组或棉花和大豆处理组间的落卵量差异不显著;但在包含桃的处理组中,桃蛀螟在棉花、玉米或大豆处理区的落卵量均显著高于桃处理区。上述结果表明,供试4种寄主植物中,桃蛀螟偏好在棉花、玉米和大豆上产卵,其中玉米对桃蛀螟的适合度相对较高,棉花对桃蛀螟的适合度相对较低...