Diapause termination in the millet stem borer, Coniesta ignefusalis (Lepidoptera: pyralidae) in Ghana as affected by photoperiod and moisture

Studies were conducted in northern Ghana in 1997 and 1998 on the effects of contact moisture and photoperiod on the termination of larval diapause in the stem borer, Coniesta ignefusalis (Hampson). Results obtained over the two years consistently showed that on its own, photoperiod had no significant effect on diapause termination. In combination with contact moisture, however, a long day photoperiod of 13L:11D accelerated diapause termination and increased the cumulative percentage pupation. Contact with moisture was crucial for diapause termination but its influence was more pronounced in larvae collected from the field after March. Generally, access to moisture earlier than April resulted in very high larval mortality. These observations, together with the fact that some of the larvae (12%) denied access to water throughout the experimental period subsequently pupated, suggest that moisture may not be the sole factor triggering diapause termination in C. ignefusalis. The implications of these findings are discussed.     

Diapause termination in the spotted stem borer, Chilo partellus (Lepidoptera: Pyralidae) in the laboratory

The effect of temperature, photoperiod, artificial diet and water on the termination of diapause by larvae of the stem borer, Chilo partellus (Lepidoptera: Pyralidae), was studied in the laboratory. Termination of diapause as indicated by pupation was affected mainly by a combination of high temperature and a long day photoperiod. Total darkness did not prevent termination of diapause and pupation occurred also in larvae which were never exposed to water. Long days accelerated pupation, but, under 16 h daylength, termination of diapause was faster than under constant illumination. Provision of artificial diet had no effect or slowed down pupation but water decreased the time to pupation. Under 28°C, 16 h daylength and availability of water, C. partellus diapausing larvae terminated diapause and pupated in about 9 days.     

Treatment of millet crop plant (Sorghum bicolor) with the entomopathogenic fungus (Beauveria bassiana) to combat infestation by the stem borer,Chilo partellus Swinhoe (Lepidoptera: Pyralidae)

Experiments were done to test if Beauveria bassiana can become an endophyte in sorghum and confer protection from stem borer. Four-week-old sorghum seedlings were treated with B. bassiana. The plants were examined for endophytic presence of B. bassiana, 30 and 60 days after treatment. Stem cultures from treated plants showed growth of B. bassiana. PCR amplification using fungal specific primers for a conserved region of β tubulin gene yielded identical 360 bp products from both B. bassiana and treated sorghum plants. In a subsequent experiment, B. bassiana treated and untreated (control) sorghum plants were artificially infested with stem borer (Chilo partellus) larvae 15 days post treatment and the extent of damage was compared. About 40% of the control plants developed dead heart while no plant in the B. bassiana treated plot did. In the surviving control plants, stem tunneling by shoot borer was significantly higher compared to B. bassiana treated sorghum plants.     

Tolerance of Bt corn (MON 810) to maize stem borer, Chilo partellus (Lepidoptera: Pyralidae)

Transgenic corn (MON 810), expressing the Bacillus thuringiensis (Bt) protein, Cry1Ab, was evaluated under greenhouse conditions for its tolerance to the maize stem borer, Chilo partellus. Bt corn (MON 810) provided effective protection against the stem borer even under a high level of larval infestation in the greenhouse. The observed tolerance is examined and discussed in the light of the susceptibility of C. partellus to the Cry1Ab protein in laboratory bioassays. The implications of the tissue concentrations of Cry1Ab in MON 810, and baseline susceptibility recorded in the current study, for insect-resistance management are discussed.     

亚洲玉米螟两个不同地理种群对暗期干扰的滞育反应

为了探明亚洲玉米螟Ostrinia furnacalis (Guenée)不同地理种群对暗期干扰的滞育反应, 本文在研究了亚洲玉米螟南昌种群（28°41′N, 115°53′E）和哈尔滨种群（44°56′N, 127°10′E）光周期反应的基础上, 在室内分别测试了25℃和28℃温度下1 h的光脉冲干扰光周期L9∶D15和L12∶D12对这两个不同地理种群幼虫滞育抑制的影响。结果表明： 在25℃和28℃下, 哈尔滨种群的临界日长分别比南昌种群延长了1 h 40 min和2 h; 在所有测试的暗期干扰实验中, 除了极少数光脉冲干扰点外, 南昌种群幼虫滞育的发生率显著低于哈尔滨种群; 1 h光脉冲干扰光周期L9∶D15的滞育发生率明显低于干扰光周期L12∶D12, 且前者表现了暗期的中间对光脉冲最敏感, 而后者显示了暗期的初期对光脉冲最敏感; 28℃下光脉冲对滞育的抑制效果强于25℃。这些结果进一步提示, 即使在同种昆虫中, 如果地理种群和实验条件不同, 暗期干扰对滞育抑制的效果也可能不同。     

扬州地区水稻二化螟寄生蜂种类及主要寄生蜂发生动态

本文报道了江苏扬州地区水稻二化螟Chilo suppressalis(Walker)寄生蜂主要有10种,即中华钝唇姬蜂Eriborus sinicus(Holmgren)、二化螟盘绒茧蜂Cotesia chilonis(Munakata)、稻螟小腹茧蜂Microgaster russata Haliday、螟甲腹茧蜂Chelonus munakatae Munakata、中华茧蜂Amyosoma chinensis(Szepligeti)、螟黄足盘绒茧蜂Cotesia flavipes(Cameron)、夹色姬蜂Auberteterus alternecoloratus(Cushman)、桑蟥聚瘤姬蜂Iseropus(Gregopimpla)kuwanae(Viereck)、螟蛉瘤姬蜂Itoplectis naranyae(Ashmead)以及二化螟盘绒茧蜂的重寄生蜂绒茧灿金小蜂Trichomalopsis apanteloctena(Crawford)。田间系统调查表明:扬州地区7-9月水稻二化螟寄生蜂的主要种类为二化螟盘绒茧蜂、中华钝唇姬蜂、螟甲腹茧蜂、稻螟小腹茧蜂、螟蛉瘤姬蜂、桑蟥聚瘤姬蜂,但这些寄生蜂对一代水稻二化螟幼虫的寄生率较低,对二代水稻二化螟幼虫的寄生率高。水稻二化螟越冬期的系统调查表明:扬州地区二化螟越冬幼虫的寄生蜂主要有3种,即二化螟盘绒茧蜂、中华钝唇姬蜂和稻螟小腹茧蜂,其中二化螟盘绒茧蜂和中华钝唇姬蜂是寄生水稻二化螟越冬幼虫的优势种。水稻二化螟越冬幼虫的寄生率调查表明,扬州地区水稻二化螟越冬幼虫的寄生率在不同年份间有一定的波动,但一般都在15%以上,有的甚至高达89.88%,因此寄生蜂对二化螟越冬幼虫具有很好的控制作用,能有效压低来年水稻二化螟的田间越冬基数。此外,3种寄生蜂出茧时间在1月和2月之间达到最长,分别达到19.79 d、17.26 d和27.00 d,该结果表明,在扬州地区这3种寄生蜂可能都存在滞育现象。     

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.     

Some aspects of feeding responses in the stem borer Chilo partellus swinhoe (Lepidoptera: Pyralidae).

Feeding responses of Chilo partellus larvae to different food sources, were studied. Maize and sorghum were more preferred to artificial diet by the larvae irrespective of their rearing media. Larvae fed on maize and sorghum leaves as well as maize and sorghum stems. The rearing medium did not have any effect on the feeding preference; it could only improve but not induce the feeding behaviour.     

黄翅绢野螟生物学特性及田间种群动态

【目的】黄翅绢野螟Diaphania caesalis是热带木本粮食作物菠萝蜜Artocarpus heterophyllus的重要钻蛀性害虫,对热区快速发展的菠萝蜜产业威胁巨大。本研究旨在明确该虫的生物学特性及田间发生规律,为准确预测和高效治理该虫提供理论基础。【方法】在室内温度26±1℃、相对湿度70%±5%、光周期14L∶10D条件下,以菠萝蜜叶片为食料,观察黄翅绢野螟各龄期形态特征、发育历期及繁殖能力,并在田间网室中观察该虫年生活史;通过室内选择和非选择试验,研究该虫的寄主多样性;2018年1-12月通过田间系统调查,分析该虫在海南省琼中县的种群动态规律。【结果】黄翅绢野螟卵、幼虫、预蛹、蛹和成虫的发育历期分别为4.58±0.50, 21.00±1.36, 2.50±0.51, 10.20±0.53和12.31±3.16 d,平均世代历期为50.50±3.54 d。各龄期主要形态特征为:卵椭圆形,表面具网纹;幼虫体黄褐色,化蛹前变白色,蜕裂线呈倒"Y"形;蛹红褐色,足和翅芽长至第5腹节;成虫体麦黄色,前翅有瓜子状和塔状黄斑。雌蛾可多次产卵,单雌产卵量为147.25±84.24粒...     

A microsporidian pathogen of the poroporo stem borer,Sceliodes cordalis (Dbld) (Lepidoptera: Pyralidae): Effects on adult reproductive success

Larvae of Sceliodes cordalis were infected over a range of ages and doses with Nosema sp. (NSC). The resulting spore loads in adults ranged from 9.3 × 10⁵ to 8.9 × 10⁷ spores and varied with the age of the larva at infection and with the dose ingested. Infection caused small reductions in female weight, mating success, potential fecundity, longevity, and egg viability. The magnitude of spore loads in female moths was not found to influence any of these factors apart from potential fecundity in very low weight moths. The cumulative effects of infection reduced natality in the laboratory colony from 11,400 to 6000 hatching eggs per 100 females. Laboratory reared, infected females were smaller, had a lower longevity, a reduced spore load, and were more fecund (eggs per milligram adult weight) than infected females from a field population. Manipulation of NSC in a biological control program is not considered to be of any value.     

不同配方信息素诱芯对二化螟的诱捕效果比较研究

2004年和2005年夏季在江淮稻区二化螟Chilo suppressalis性诱剂诱捕的结果表明：一种新型诱芯（其中顺-11-十六碳烯醛∶顺-9-十六碳烯醛为2∶1）对第1代二化螟的日平均诱捕量相当于二化螟标准诱芯的5倍左右,而在越冬代和第2代成虫发生期则分别相当于后者的1.5839倍和1.7474倍。二化螟诱捕量取决于顺-11-十六碳烯醛和顺-9-十六碳烯醛的比例,而与其各自的剂量或信息素总剂量无明显关系,且它们的最佳配比可能因世代夜间温度的不同而不同,二化螟标准诱芯在第1代诱捕效果下降的原因可能是两种不饱和十六醛比例不适。     

Factors controlling the distribution of a subtropical corn borer,Diatraea grandiosella (Lepidoptera: Pyralidae)

During this century the southwestern corn borer, Diatraea grandiosella (Lepidoptera: Pyralidae), has extended its range from subtropical Mexico into the United States, below 38° N latitude. This maize‐feeding insect is now found from Arizona east to Alabama and north to Kansas, Missouri, and Tennessee. The species has adapted to the shorter growing seasons, longer summer daylengths, and lower winter temperatures present in the southern US than are present in Mexico. Life history, morphological, and behavioral traits were compared for populations of D. grandiosella from southeastern Missouri and southcentral Mexico and revealed differentiation in a suite of characters, some of which show clear adaptation to a northern climate while others are obviously less adaptive. An electrophoretic comparison of enzymes from D. grandiosella from the central portion of its range in the US and from a population from southcentral Mexico indicated that considerable genetic differentiation has occurred. Quantitative genetic studies should be undertaken on the original and dispersed populations to differentiate between those characters that have been directly responsible for the adaptation of this insect to northern maize‐growing regions and those that have changed merely due to genetic correlations with characters undergoing selection. Data from such studies, together with available information about the dispersal of this insect, should provide insight into factors regulating the movement of tropical insects into temperate regions.     

Mutation in acetylcholinesterase1 associated with triazophos resistance in rice stem borer, Chilo suppressalis (Lepidoptera: Pyralidae)

Two full-length genes encoding different acetylcholinesterases (AChEs), designated as Ch-ace1 and Ch-ace2, were cloned from strains of the rice stem borer (Chilo suppressalis) susceptible and resistant to the organophosphate insecticide triazophos. Sequence analysis found an amino acid mutation A314S in Ch-ace1 (corresponding to A201 in Torpedo californica AChE) that was consistently associated with the occurrence of resistance. This mutation removed an MspA1 I restriction site from the wild type allele. An assay based on restriction fragment length polymorphism (RFLP) analysis was developed to diagnose A314S genotypes in field populations. Results showed a strong correlation between frequencies of the mutation and phenotypic levels of resistance to triazophos. The assay offers a prospect for rapid monitoring of resistance and assisting with the appropriate choice of insecticide for combating damage caused by C. suppressalis.     

Seasonal changes of phospholipids in last instar larvae of rice stem borer Chilo suppressalis Walker (Lepidoptera: Pyralidae)

Phospholipids of the cell membrane have been studied from the viewpoint of how overwintering insects inhabiting temperate zones adapt to low temperature. The transition of cell membrane phospholipids from a liquid crystalline phase to a gel phase is a crucial cause of cold or freezing injuries. We determined the qualitative and quantitative changes of phospholipids in the last instar larvae of the rice stem borer in summer and winter. We found that the total amount of their phospholipids did not change significantly between summer and winter and that the sum of phosphatidylcholine (PC) and phosphatidylethanolamine (PE) comprised about 85% of their total phospholipids. In summer, the ratio of their PE to PC was almost one, while from autumn to mid‐winter it increased and reached three in February. The fatty acid compositions of PC hardly changed, and the percentage of unsaturated fatty acids did not exceed 50%. In contrast, the percentage of unsaturated fatty acids of PE in overwintering larvae increased up to 80% as ambient temperatures fell and oleic acid mainly contributed to the high percentage of unsaturation. In the present study, the relationship between the quantitative and qualitative changes of phospholipids and adaptation of the rice stem borer to cold winter climate are discussed.     

Age- and density-related oviposition behavior of the European corn borer,Ostrinia nubilalis (Lepidoptera: Pyralidae)

Age-related oviposition patterns ofOstrinia nubilalis were studied at three population densities in the laboratory by releasing newly eclosed adults in wire-screened cages and analyzing their oviposition throughout the adult stage with digital analysis. Oviposition sequences of individual females depositing egg masses were documented on the third and seventh nights after eclosion with a video camcorder. During a sequence, a female produced an egg in an average time of 15 or 26 s on the third and seventh nights, respectively, and completed depositing an egg mass the size of 20–39 eggs in an average time of 316 and 525 s, respectively. Females were not easily disturbed during egg mass deposition and pulsated their abdomen before deposition of each egg. Females produced few egg masses the first night after eclosion. Oviposition increased on nights 2 and 3 but declined steadily thereafter as females matured. Females older than 6 nights produced fewer egg masses; the proportion of egg masses with fewer than 20 eggs increased gradually. By the end of the adults' lifetime, nearly 100% of the egg masses had fewer than 20 eggs. The data are fundamental to our research to define the role of phytochemicals in modifying oviposition behavior of the European corn borer.     

Diapause termination, post-diapause development and reproduction in the beet webworm, Loxostege sticticalis (Lepidoptera: Pyralidae)

Effects of photoperiod and cold exposure on diapause termination, post-diapause development and reproduction in Loxostege sticticalis were examined. Larvae were reared at diapause inducing condition (22 °C, L:D 12:12) consistently or transferred to long day photoperiod (L:D 16:8) and darkness (L:D 0:24) respectively, after entering into diapause. Diapause was terminated in approximately 40% of the larvae after 36 days, and no significant differences were observed between photoperiods, suggesting larval diapause was terminated spontaneously without being induced by photoperiods. Cold exposure significantly hastened diapause termination. The diapause termination incidence increased significantly with peaks of 98% at both 5 °C and 0 °C exposure for 30 days, as compared to 42% in controls not exposed to cold, while the mortality and number of days required for diapause termination decreased dramatically. The optimal low temperature exposure periods under 5 °C or 0 °C were 20 days and 30 days, showing a higher termination incidence and shorter time for diapause termination. This suggests that the low temperatures in winter play an important role in diapause termination under natural conditions. The threshold temperatures for post-diapause development in prepupae and pupae were 9.13 °C and 10.60 °C respectively, with corresponding accumulations of 125 and 200 degree-days. Adults that experienced larval diapause significantly delayed their first oviposition, oviposition period was prolonged, and the lifetime number of eggs laid was decreased, however both males and females have significantly longer longevity. The field validation of diapause termination, the degree-days model, and the relationship between diapause and migration in L. sticticalis were also discussed.     

Interactions between Fusarium species from sugarcane and the stalk borer, Eldana saccharina (Lepidoptera: Pyralidae)

In this study, beneficial relationships between Fusarium species in sugarcane and the stalk borer, Eldana saccharina (Lepidoptera: Pyralidae) were demonstrated in vitro . In addition, Fusarium species with antagonistic properties were found to inhabit sugarcane. Attenuated Fusarium isolates from sugarcane stalks collected across the South African sugar industry were incorporated into diet formulated to mass rear E. saccharina . Of the over 200 Fusarium isolates obtained, 10 that significantly improved the survival and development of E. saccharina larvae and considered to be beneficial were selected for further study, as were 10 that were detrimental or antagonistic to the stalk borer. Twelve of the selected isolates were identified as F. sacchari by direct sequencing of translation elongation factor-1α fragments, eight of which resulted in reduced numbers of surviving larvae and significantly lower larval masses. F. proliferatum isolates resulted in increased survival and mass of E. saccharina and three of the five isolates assigned to the F. pseudonygamai group enhanced E. saccharina development. Results from olfactory choice experiments suggested the production of attractive and repellent metabolites by certain isolates. Findings from this study may offer additional or alternative strategies for managing E. saccharina infestation of sugarcane.     

Incidence and control of dogwood borer (Lepidoptera: Sesiidae) and American plum borer (Lepidoptera: Pyralidae) infesting burrknots on clonal apple rootstocks in New York

Surveys were conducted in the major apple growing regions of New York state to determine the incidence of borers infesting burrknots on clonal apple rootstocks. Dogwood borer, Synanthedon scitula (Harris), was generally prevalent throughout the state, but American plum borer, Euzophera semifuneralis (Walker), was limited to western New York apple orchards near infested stone fruit trees. Insecticides evaluated in the field for efficacy against both borers were chlorpyrifos, endosulfan, indoxacarb plus oil, methoxyfenozide, fenpropathrin, and kaolin clay. Also, white latex paint was tested alone and mixed with chlorpyrifos. One application of chlorpyrifos applied at the petal fall developmental stage was equivalent to chlorpyrifos applied at petal fall and again in mid-July, and it provided season-long control of dogwood borer and American plum borer. One application of chlorpyrifos applied any time between the half-inch green developmental stage and petal fall, or after harvest the previous season, controlled both overwintered and summer brood larvae of dogwood borer. Multiple applications of fenpropathrin, indoxacarb plus oil, and endosulfan applied during the dogwood borer flight period controlled the summer brood.     

Role of membrane transport of water and glycerol in the freeze tolerance of the rice stem borer, Chilo suppressalis Walker (Lepidoptera: Pyralidae)

Overwintering larvae of the rice stem borer, Chilo suppressalis accumulate glycerol and are freezing tolerant to about -25 degrees C. However, non-diapausing larvae cannot accumulate glycerol and are killed by freezing. We compared the extent of tissue damage, the effects of glycerol concentration, and the transport of glycerol and water in fat body tissues from these larvae at selected freezing temperatures. Tissues from overwintering larvae, but not non-diapausing larvae, survive when frozen at -20 degrees C with 0.25 M glycerol, but the protection afforded by glycerol is offset by the water-channel inhibitor mercuric chloride. Glycerol in higher concentration (0.75 M) affords some protection even to the fat body of non-diapausing larvae. Radiotracer assays of overwintering larvae show that water leaves the tissues during freezing while glycerol enters, and that mercuric chloride disrupts this process. Transport is also disrupted after lethal freezing at -35 degrees C. Therefore, membrane transport of water and glycerol is involved in the avoidance of freezing injury to fat body cells of the rice stem borer, apparently by mediating the replacement of water with glycerol in freezing-tolerant tissues.