Effect of bunch sanitation on spatial distributions of abscised fruit and phycitine moths (Lepidoptera: Pyralidae) in California date gardens

Phycitine moths are an economic impediment to California date, Phoenix dactylifera L., production. Summer populations build to damaging levels on abscised dates that get trapped in fruit bunches. This study was conducted to determine the relationship between abscised fruit and moth infestation, and to evaluate changes in the spatial distribution of abscised fruit and moth-infested fruit after a bunch-sanitation treatment. Over the 9 wk of this study, there was a 69.9% reduction in the number of moth-infested fruit after a single sanitation treatment. Linear regression analysis showed a significant relationship between abscised fruit and phycitine moth-infested fruit; 42 and 76.6% of the variation in the number of infested fruit was explained by the number of abscised fruit in noncleaned and cleaned plots, respectively. The pattern of reinfestation by moths over the 9 wk posttreatment period was analyzed with spatial analysis with distance indices. Significant spatial associations were found between abscised fruit and moth-infested fruit, supporting the regression analysis. The sanitation treatments caused significant gaps in both abscised fruit and moth-infested fruit. Over time, gap sizes became smaller, indicating a nonrandom pattern of reinfestation that likely was caused by the movement of moths from nontreated areas into treated areas. This study, the first spatial analysis conducted in dates, suggests that in-season bunch sanitation could be effective at reducing summer moth densities if applied on a large regional scale.     

Influence of host plant stages on carob moth (Lepidoptera: Pyralidae) development and fitness

Different generations of the carob moth, Ectomyelois ceratoniae (Zeller), use different date, Phoenix dactylifera L., fruit stages as they become available during the summer months in southern California. These are the kimri, khalal, and tamar fruit stages. This study was conducted to determine whether carob moth development and fitness were affected by these different fruit stages. Developmental time from neonate larvae to adult, when reared at 31.9 degrees C and 82.1% RH, ranged from 30.5 to 32.3 d for females and 27.1 to 29.5 d for males on the different field-collected fruit stages. Males and females had the highest emergent weight when reared as larvae on kimri fruit and the lowest on tamar fruit. Females laid the most eggs when reared on kimri fruit and the least when reared on tamar fruit. Estimates of population doubling times ranged from 5.4 d on artificial diet (included as a control) to 7.5 d on tamar fruit. This short doubling time shows the ability of carob moth to develop rapidly under optimal conditions. Degree-day (DD) estimates for carob moth development ranged from 636 DD on kimri fruit to 658 DD on tamar fruit, which translate to 32-50 d under field temperatures in the area where dates are grown. Potential implications for field management of E. ceratoniae include improved timing of insecticide treatments to limit population growth early in the season rather than the conventional late season approach.     

北京郊区苹果小卷蛾成虫发生规律研究

苹果小卷蛾AdoxophyesoranaFischervonR slerstamm为北京郊区大桃生产中的主要害虫 ,试验采用黑光灯诱杀、糖醋盆诱集 2种方法在不同生态环境果园对其成虫发生期进行了观测。结果显示苹果小卷蛾在北京地区 1年发生 3代 ;越冬代成虫羽化高峰为 5月底至 6月初 ,第 1代幼虫防治适期为 6月1 0～ 1 5日 ;第 1代成虫羽化高峰为 7月中旬 ,第 2代幼虫防治适期为 7月下旬。     

Potential for outbreaks of leafrollers (Lepidoptera: Tortricidae) in California apple orchards using mating disruption for codling moth suppression

Two species of leafrollers, Argyrotaenia citrana (Fernald) and Pandemis pyrusana Kearfott, represent serious obstacles to the implementation of mating disruption for control of codling moth in coastal California apple orchards. Larval and adult densities of A. citrana and P. pyrusana and subsequent fruit damage were compared under different codling moth control treatments. Leafroller larval counts and levels of fruit damage were significantly higher in most plots that were untreated or treated only with codling moth pheromone. Leafroller fruit damage levels in these plots were commonly between 10 and 15% at harvest. As summer larval counts were good predictors of fruit damage levels, larval sampling could be a useful tool for predicting leafroller outbreaks. Use of pheromone trapping for A. citrana to detect localized outbreaks within an orchard was not useful and failed to correlate with larval numbers, whereas adult monitoring for P. pyrusana appears more promising. Efforts to implement a codling moth mating-disruption program in California must include changes in strategies for monitoring and controlling leafroller species.     

Numerical and temporal relationships in a three-level food chain

Summary Densities were examined in natural populations consisting of horsenettle (Solanum carolinense), larvae of a horsenettle-specific phytophagous moth (Frumenta nundinella), and a polyphagous parasitoid wasp (Scambus pterophori), that parasitized the moth. Herbivore and parasitoid densities were both positively associated with fruit density, but moth larval density was linear while parasitoid density increased parabolically; thus, optimum moth survivorship was at intermediate moth densities. There was no evidence of escape from herbivory in time by plant populations due to either mean flowering date or a spread of flowering in seasonal time. However, one plant population and one moth population apparently escaped in space due to isolated location. Although plant reproductive success is reduced whether or not moth larvae are parasitized, both presence of a numerical herbivore refuge and parasitoid attack at high fruit and moth densities would be expected to stabilize long-term temporal dynamics of this simple food chain.     

Re-evaluating the role of selective abscission in moth/yucca mutualisms

Conflicts of interest are common to mutualisms, particularly those derived from exploitative interactions. Conflicts of interest are particularly pronounced in pollination/seed predation mutualisms, such as moth/yucca interactions, where consumption of seeds by larvae of a plant's pollinator will raise the fitness of the pollinator but lower the fitness of the plant. A central question in these mutualisms is, therefore, “what limits seed predation?” If plants with excess flowers selectively abscise flowers containing many eggs, they may reduce seed predation and overall increase their fecundity. If eggs in abscised flowers die, selective abscission may additionally contribute to the limitation or regulation of pollinator populations, thereby decreasing the probability of future overexploitation. We examined the effect of selective abscission in the mutualism between Yucca kanabensis and one of its pollinating moths, Tegeticula altiplanella. Per capita mortality of moth eggs due to abscission was high (95.5%), but did not increase on inflorescences with more ovipositions per flower. Overall mortality was partitioned into two components based upon the proportion of visited flowers abscised (i.e. resource‐limitation) and additional mortality (=selective abscission). Resource‐limitation per se inflicted 93.9% egg mortality, or most of the mortality due to abscission. But, the average number of eggs in fruit was lower than the average number of eggs in flowers, indicating that there was some selectivity of abscission. However, neither source of mortality increased on inflorescences with more ovipositions per visited flower. Egg mortality resulting from selective abscission was not as high as possible, because the yuccas appeared to use oviposition‐damaged ovules as a cue for selective abscission, and there was considerable variation in the relationship between oviposition number and damaged ovules. However, even if yuccas had retained the flowers containing the fewest eggs, selective abscission still would not have been higher on inflorescences with more ovipositions per flower. Considering also that, 1) number of ovipositions is a poor predictor of the number of larvae that hatch and feed on the developing seeds in a fruit and that, 2) there are several moth/yucca interactions in which selective abscission does not occur, we conclude that abscission, and particular selective abscission, may have density‐limiting effects on moth populations, but will fail as general explanations for regulating the dynamics of moth populations.     

Population dynamics of the potato tuber moth on processing tomatoes in Israel

The potato tuber moth (PTM),Phthorimaea operculella (Zeller) (Lepidoptera: Gelechiidae), is a major pest of processing tomatoes,Lycopersicon esculentum Mill. (Solanaceae), in Israel. The larvae penetrate the tomato fruit through the stem end and present a serious threat to crop quality. Foliage and fruit samples were taken in nine commercial tomato fields located in Israel's three main tomato growing areas, two of which are potato growing areas as well. PTM was not found where potatoes were absent. Potato harvest in nearby fields was found to be the most significant factor affecting seasonal trends in PTM population density in tomatoes. All four larval instars were found in foliage on all sampling dates. Significantly higher proportions of first instars were found during the population density increase which followed potato harvest. Damaged fruits did not contain first instar larvae, indicating that PTM never undergoes complete development within tomato fruit. Fruit damage levels at harvest were positively correlated to the peak mean population densities on foliage and the date they were observed. In tomato fields not adjacent to potatoes, infestation was first observed at the edge of the field. Both before and after the potato harvest in nearby fields, population density at the edge of the field was significantly higher than at the center. In tomato fields adjacent to potatoes, no significant differences were found between population densities at the edge and center before the potatoes were harvested. After the potato harvest, population density at the center of tomato fields was higher than at the edge. Deceased, October 1988     

Integrated control of apple pests in New Zealand

In a study at Appleby Research Orchard, Nelson, examination of the fruit from mature ‘Delicious’ apple trees sprayed with ryania over 5 years showed that less than 10% of 5th‐instar larvae of the codling moth (Laspeyresia pomonella) seeking cocooning sites originated from fruit on the ground. In 1972 and 1973 the survival of such larvae was studied by tagging with cobalt‐58 and releasing them beneath mature trees. In both years about 25 % of the tagged larvae returned to the tree to spin cocoons. Larvae released on bare ground 0–1 m from the tree trunks were more successful than those released in the sward 1–2 m away. Once on the trees, most larvae spun cocoons beneath exfoliating bark on the lower parts of the leaders and the trunk. Fifty‐two percent of the cocoons located were formed on the ground, and overwintering mortality of these was estimated to be near 100%. The pre‐cocooning mortality of larvae released on the ground was similar to that of larvae released on the trees in the same year. It was concluded that larvae from windfalls could be ignored in estimating 5th‐instar larval mortality of codling moth on ‘Delicious’ trees. On the cultivars ‘Dunn's Favourite’ and ‘Cox's Orange Pippin’, however, the higher percentage of larvae in windfalls made their inclusion in mortality estimates essential.     

Host status of fresh prunes by potential quarantine pests in laboratory tests and evaluation of packinghouse culls.

The status of fresh prunes, Prunus domestica L., as a host for codling moth, Cydia pomonella (L.) (Lepidoptera: Tortricidae); peach twig borer, Anarsia lineatella Zeller (Lepidoptera: Gelechiidae); omnivorous leafroller, Platynota stultana Walshingham (Lepidoptera: Tortricidae); oriental fruit moth, Grapholita molesta (Busck) (Lepidoptera: Tortricidae); navel orangeworm, Amyelois transitella (Walker) (Lepidoptera: Pyralidae); and walnut husk fly, Rhagoletis completa Cresson (Diptera: Tephritidae), was investigated in laboratory tests and by examination of packinghouse culls. In laboratory no-choice tests, the mean number of adults reared per fruit was 0.01 for codling moth, 0.08 for omnivorous leafroller, 0 for oriental fruit moth, and 1.6 for navel orangeworm. In choice tests the mean number of adults reared per apple or fresh prune was for codling moth, 0.78 and 0.02 (significantly different); for omnivorous leafroller, 0.05 and 0.02; and for oriental fruit moth, 2.07 and 0 (significantly different), respectively. Walnut husk fly oviposited in fresh prunes in no-choice tests but pupae did not develop from the fruit. In choice tests, walnut husk fly did not oviposit in fresh prunes when caged with its normal host, green walnuts, in which large numbers of pupae developed. Inspection of packinghouse culls for immature insects showed that fresh prunes with possible larval feeding sites in the form of frass or fruit gum extrusions were lighter in weight, significantly less firm, similar in color, and had significantly higher soluble solids than noninfested fruit. Based on packinghouse cull samples, 1 fresh prune per 133 harvested fruit would be expected to show possible insect damage. Eleven peach twig borer larvae were found in fresh prune cull samples (213.9 kg) removed from a 16,744.5-kg harvest. The calculated level of infestation was 1 infested fruit per 8,501.8 fruit harvested or per 21.7 cartons of medium-sized packed fruit. Based on our results, the risk of infestation of fresh prunes by the insects in this study would be minimal in fruit exported from the San Joaquin Valley of California.     

苹果蠹蛾幼虫爬行特性

本文通过收集苹果和梨树上的蛀果模拟自然落果,研究了苹果蠹蛾Cydia pomonella(L.)脱果幼虫的爬行特性。结果发现,58.91%的幼虫钻出蛀果进行了爬行,而41.09%滞留于果堆内部;在进行爬行的幼虫中,50%的幼虫爬行距离在0～1m之间,95%的幼虫爬行距离在0～7m之间,这意味着在实际防治过程中,落果周围0到7m的范围都需要做防治处理,而0～1m的范围需要重点防治;幼虫在果堆放置后的0～25d持续脱果,表明当果园内有落果时需要马上及时清理;幼虫结茧的高度大部分在50cm以下,在实际防治过程中,树干缚带诱杀幼虫时应将诱集带设置在距地面0～0.5m的主干上,以保证落果幼虫也可以被诱集带捕获。     

Consequences of ants and extrafloral nectar for a pollinating seed‐consuming mutualism: ant satiation,floral distraction or plant defense?

Non‐pollinating consumers of floral resources, especially ants, can disrupt pollination and plant reproductive processes. As an alternative food resource to flowers, extrafloral nectar (EFN) may distract and satiate ants from flowers, thereby reducing their antagonistic effects on plants. Yet, EFN may actually attract and increase ant density on plants, thus increasing the disruption of pollination and/or their defense of plants. In this study, we tested the effects of ants and EFN on pollinating seed‐consuming interactions between senita cacti and senita moths in the Sonoran Desert. Prior study of senita showed that EFN can distract ants from flowers, but consequences for plant–pollinator interactions remain unstudied. In our current study, ant exclusion had no effect on pollination or oviposition when moths were abundant (>85% flower visitation). Yet, in an ant by EFN factorial experiment under lower moth abundance (<40% visitation), there was a significant effect of ant exclusion (but not EFN or an ant × EFN) on pollination and oviposition. In contrast with our predictions, ant presence increased rather than decreased pollination (and oviposition) by moths, indicating a beneficial effect of ants on plant reproduction. While ant density on plants showed a saturating response to continuous experimental variation in EFN, in support of ant satiation and distraction, the probability of pollination and oviposition increased and saturated with ant density, again showing a beneficial effect of ants on plant reproduction. Ants showed no significant effect on fruit set, fruit survival, or fruit production of oviposited flowers in the ant exclusion experiment. Ants did not affect the survival of moth larvae, but there was a marginally significant effect of ants in reducing wasp parasitism of moths. We suggest that EFN may not only distract ants from disrupting plant–pollinator interactions, but they may also enhance plant–pollinator interactions by increasing pollination and reducing wasp parasitism. Though often considered dichotomous hypotheses, ant distraction and plant defense may be synergistic, though the mechanism(s) for such positive ant effects on plant–pollinator interactions needs further study.     

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.     

Pollen dispersal in Yucca filamentosa (Agavaceae): the paradox of self-pollination behavior by Tegeticula yuccasella (Prodoxidae)

We investigated pollen dispersal in an obligate pollination mutualism between Yucca filamentosa and Tegeticula yuccasella. Yucca moths are the only documented pollinator of yuccas, and moth larvae feed solely on developing yucca seeds. The quality of pollination by a female moth affects larval survival because flowers receiving small amounts of pollen or self-pollen have a high abscission probability, and larvae die in abscised flowers. We tested the prediction that yucca moths primarily perform outcross pollinations by using fluorescent dye to track pollen dispersal in five populations of Y. filamentosa. Dye transfers within plants were common in all populations (mean ± 1 SE, 55 ± 3.0%), indicating that moths frequently deposit self-pollen. Distance of dye transfers ranged from 0 to 50 m, and the mean number of flowering plants between the pollen donor and recipient was 5 (median = 0), suggesting that most pollen was transferred among near neighbors. A multilocus genetic estimate of outcrossing based on seedlings matured from open-pollinated fruits at one site was 94 ± 6% (mean ± 1 SD). We discuss why moths frequently deposit self-pollen to the detriment of their offspring and compare the yucca-yucca moth interaction with other obligate pollinator mutualisms in which neither pollinator nor plant benefit from self-pollination.     

Interannual differences in growth and hatch date distributions of age-0 year walleye pollock Theragra chalcogramma (Pallas) sampled from the Shumagin Islands region of the Gulf of Alaska, 1985 – 2001

Daily increments of age-0 year walleye pollock Theragra chalcogramma otoliths from 1985 to 2001 were examined for interannual variability in growth and hatch dates. Fish were collected in summer and autumn surveys near the Shumagin Islands in the western Gulf of Alaska (GOA). Hatch date distributions of these fish were compared with hatch dates of larvae from spawning aggregations located in Shelikof Strait and the Shumagin Islands based on their spawning times. The hatch date distributions of age-0 year fish captured from the Shumagin Islands area were similar to those observed for larvae from the Shelikof Strait spawning group. Age-0 year fish whose hatch dates corresponded to the Shumagin Islands spawning, which occurred earlier in January and February, were not found. Sea surface temperature was associated with variability in hatch date distribution and growth.     

Entomopathogenic nematodes for control of diapausing codling moth (Lepidoptera: Tortricidae) in fruit bins

Fruit bins infested with diapausing larvae of codling moth larvae, Cydia pomonella (L.), are a source of reinfestation of orchards and may jeopardize the success of mating disruption programs and other control strategies. Bins are not routinely treated for control of overwintering codling moth before placing them in orchards. Entomopathogenic nematodes provide a noninsecticidal alternative to methyl bromide that could be applied at the time bins are submerged in dump tanks at the packing house for flotation of fruit. Diapausing codling moth larvae in miniature fruit bins were highly susceptible to infective juveniles of Steinernema carpocapsae (Weiser). Immersion of bins in suspensions of S. carpocapsae ranging from 5 to 100 infective juveniles per milliliter of water resulted in 68-100% mortality. Immersion times of 1 or 5 min in suspensions with 5 infective juveniles of S. carpocapsae per milliliter of water, with and without Tween 80 (0.01%), yielded essentially the same mortality of codling moth larvae. Highest mortalities in codling moth larvae (88%) after treatment of bins in suspensions of 5 infective juveniles of S. carpocapsae per milliliter of water were observed after incubation for 24 h at 25 degrees C and 70% RH. Lowest mortalities (37%) were observed after incubation at 15 degrees C and 35% RH. Comparative tests conducted with Heterorhabditis marelatus Liu & Berry, Steinernema kraussei (Steiner), and S. carpocapsae with 5 infective juveniles per milliliter of water resulted in 21.7, 53.9, and 68.7% mortality, respectively. The use of miniature fruit bins as described in this article provides an effective means of assessing nematode efficacy without the cumbersome size of commercial bins.     

Inhibition of premature leaf abscission by a leafminer and its adaptive significance

We tested the possibility that a lepidopteran leafminer, Coptotriche japoniella Puplesis and Diskus, inhibits the host plant Eurya japonica Thunberg from abscising mined leaves prematurely to increase its survivorship in immature stage. We monitored abscission patterns of mined leaves with sacrificed larvae, mined leaves with living larvae, and unmined leaves from April to July 2004 and 2005 until leafminers emerged as adults. Unmined leaves rarely abscised before July. Mined leaves with sacrificed larvae fell at a constant rate after May, abscising significantly more than unmined leaves. In contrast, mined leaves with living larvae rarely fell before adult emergence; afterward they abscised rapidly. We also examined larval/pupal survivorship and mortality sources on the ground and trees after leafminers completed larval development. Leafminers on the ground suffered a higher mortality from predation than those on trees, and thus they emerged as adults on the ground less successfully. These findings suggest that the leafminer C. japoniella prevents the host plant from abscising mined leaves prematurely until adult emergence, thereby increasing their survivorship.     

Relationships of abscised cotton fruit to boll weevil (Coleoptera: Curculionidae) feeding, oviposition, and development

Abscised cotton, Gossypium hirsutum L., fruit in field plots planted at different times were examined to assess adult boll weevil, Anthonomus grandis grandis Boheman (Coleoptera: Curculionidae), use of squares and bolls during 2002 and 2003 in the Lower Rio Grande Valley of Texas. Although boll abscission is not necessarily related to infestation, generally more bolls abscised than squares and abundances of fallen bolls were not related to the planting date treatments. During 2003, fallen squares were most abundant in the late-planted treatment. Although large squares (5.5-8-mm-diameter) on the plant are preferred for boll weevil oviposition, diameter of abscised squares is not a reliable measurement because of shrinkage resulting from desiccation and larval feeding. Fallen feeding-punctured squares and bolls were most abundant in late plantings but differences between fallen feeding-punctured squares versus fallen feeding-punctured bolls were found in only one treatment in 2003. During the same year, fallen oviposition-punctured squares were more numerous in the late-planted treatment than in the earlier treatments. Treatment effects were not found on numbers of oviposition-punctured bolls, but fallen oviposition-punctured squares were more common than bolls in the late-planted treatment compared with earlier treatments each year. Dead weevil eggs, larvae, and pupae inside fallen fruit were few and planting date treatment effects were not detected. Living third instars and pupae were more abundant in fallen squares of the late-planted treatment than in the earlier treatments and bolls of all three treatments. This study shows that fallen squares in late-planted cotton contribute more to adult boll weevil populations than bolls, or squares of earlier plantings.     

Flowers for better pest control? Effects of apple orchard groundcover management on mites (Acari), leafminers (Lepidoptera,Scitellidae), and fruit pests

Flowering companion plants provide nectar, pollen, alternative prey, shelter, and overwintering habitat for arthropod natural enemies and thus might increase their abundance and efficacy in pest control in agricultural fields. We report the results of a 6-year study on the effects of annual and perennial flowering herbs sown in alleys of an apple orchard on phytophagous and predacious mites, leafminer moths and their parasitoids and on pests causing fruit injury. Plots with weed-free bare ground and with regularly mowed grass served as controls. The abundance and diversity of predatory phytoseiid mites increased in the presence of flowering ground cover plants. However, this positive effect on phytoseiids was confined only to spring and autumn and intraguild predation (Typhlodromus pyri gradually displaced Amblyseius andersoni in the presence of flowers) also constrained their enhancement. Spider mites’ (Tetranychidae) abundance was low in all years and did not increase with the alley herb coverage. Incidence of the leafminer Leucoptera malifoliella was similar among the treatments despite the higher parasitism rate and parasitoid diversity in the plot with flowering herbs. We demonstrated that in the presence of flowering ground cover plants, the sex ratio of eulophid parasitoids' (mainly Chrysocharis pentheus) reared from L. malifoliella larvae and pupae shifted towards a male bias. Ground cover management had no effect on fruit injury caused by codling moth (Cydia pomonella) and summer fruit tortrix moth (Adoxophyes orana) and on the percentage of apples without insect damage.     

Seasonal and cultivar-associated variation in oviposition preference of Oriental fruit moth (Lepidoptera: Tortricidae) adults and feeding behavior of neonate larvae in apples

The Oriental fruit moth, Grapholita molesta (Busck) (Lepidoptera: Tortricidae) has become a pest of tree fruits since its introduction to the United States in the early twentieth century. Oriental fruit moth has historically been a major pest problem in peach production, and outbreaks in commercial apple (Malus spp.) orchards in the eastern United States were rare until the late 1990s. Recent outbreaks in Mid-Atlantic apple orchards have lead researchers to investigate host-associated effects on oriental fruit moth biology, behavior, and population dynamics. Studies were designed to assess cultivar level effects in apples on oviposition and larval feeding behavior of oriental fruit moth. In a mixed cultivar apple orchard, total oriental fruit moth oviposition and oviposition site preferences varied between cultivars. These preferences also varied over time, when sampling was repeated at various times of the growing season. Although most adult female oriental fruit moth preferentially oviposited in the calyx and stem areas of apple fruit, noticeable numbers of eggs also were laid on the sides of fruit, contradicting some previous reports. Oriental fruit moth females exhibited a strong ovipositional preference for fruit that were previously damaged by oriental fruit moth or codling moth, Cydia ponmonella (L.). The majority of newly hatched oriental fruit moth larvae were observed to spend <24 h on the surface of apple fruit before entry, and this behavior was observed on several apple cultivars. Neonate larvae exhibited a preference for entering fruit at either the stem or calyx ends, regardless of their initial site of placement. Our findings underscore the importance of adequate spray coverage and accurate timing of insecticide applications targeting oriental fruit moth.     

苹果蠹蛾的蛀果与脱果特性

苹果蠹蛾Cydia pomonella(L.)是我国重大植物检疫性有害生物,对苹果属以及梨属的水果生产造成严重的危害。该虫以初孵化的1龄幼虫蛀入果肉,在果实内部取食为害并完成发育,老熟幼虫在黑暗中离开果实并寻找场所结茧化蛹。为掌握苹果蠹蛾幼虫进入及脱出果实时的行为特性,从而为实施有效的防治措施提供基础信息,本文在内蒙古格棱布楞滩对苹果蠹蛾幼虫的蛀果与脱果特性开展了详细研究。取得的主要研究结果如下:1)在苹果蠹蛾种群密度较高的情况下,单个果实平均蛀孔数可达5.25个,初期蛀入果实的幼虫在2～8头之间;2)苹果及梨蛀果中的幼虫数量与蛀孔数无关,虽然果实上的最高蛀孔数可达14个,但一般情况下受害果实中的幼虫数不超过3个;3)当果实表面蛀孔数较多时(苹果超过5个,梨超过2个),苹果蠹蛾幼虫向种室钻蛀的行为发生偏移,通常转入在果肉中为害;4)落果后5d内,落果内的幼虫近半数脱果(43.1%),落果后15d内,落果内的幼虫几乎全部脱果(99.9%);5)在脱果幼虫中,94%选择在夜间脱果,6%在日间脱果;6)至试验结束,蛀果中还有64%的幼虫滞留。以上研究结果表明,在种群密度较高的情况下,苹果蠹蛾幼虫存在激烈的种内竞争;及时清除苹果蠹蛾幼虫蛀果后造成的落果对未脱果幼虫有很好的防治效果。