STUDIES OF FLUCTUATIONS IN INSECT POPULATIONS XII. FURTHER EVIDENCE OF PROLONGED LARVAL LIFE IN THE WHEAT-BLOSSOM MIDGES

Contarinia tritici emerges the same year as the larvae are in the wheat ears and up to 3 years later. Its parasites emerge up to 2 years after the larvae are in the wheat ears, but never the same year. This indicates that the supernumerary generation of C. tritici that occurs on couch grass in August and September may be expected to be free from parasites and so constitutes a dangerous source of replenishment of the pest.
Emergence of Sitodiplosis mosellana can take place after the larvae have been in the soil up to twelve winters. Most of any one year's larvae do not necessarily emerge as midges after one winter, although usually this is so. Any one year's flight is probably a composite one derived from several previous generations of this one-generation-a-year gall midge.     

Do polyphagous predators help control orange wheat blossom midge, Sitodiplosis mosellana Géhin (Dipt.,Cecidomyiidae) in winter wheat?

Abstract: Polyphagous predatory invertebrate populations were manipulated using exclusion techniques in order to examine their impact on Sitodiplosis mosellana Géhin. Experiments were conducted within the framework of the LINK Integrated Farming Systems Project in the UK, which allowed the effect of the predators to be compared between integrated and conventional farming systems. In 1995 and 1996, the exclusion technique indicated that polyphagous predators had little impact on S. mosellana numbers prior to oviposition, but may reduce the number of midge returning to the soil to diapause and thereby help to prevent populations building up in the soil. Sowing date affected ear infestation levels with earlier-drilled, conventionally farmed plots suffering heavier infestations. A strong correlation was found between the number of larvae per ear and the percentage of ears infested. At 100% infestation there was a mean of 2.8  S. mosellana larvae per ear.     

耕作方式对麦红吸浆虫种群动态的影响

为了解不同耕作方式对麦红吸浆虫Sitodiplosis mosellana （Géhin）种群动态的影响, 2010年和2011年, 在中国科学院河北省栾城农业生态系统试验站不同耕作方式的小麦样地中, 通过淘土、 成虫网捕和剥穗等方法对麦红吸浆虫进行了调查研究。结果表明： 两年取土筛检出的幼虫数量依次为秸秆还田免耕田>秸秆站立免耕田>秸秆还田旋耕田, 但2011年网捕调查显示, 秸秆还田旋耕田中的成虫数量高于另外两种样地。两年剥穗检查出的幼虫数量的排序与取土筛检出的幼虫数量的排序相反, 依次为秸秆还田旋耕田>秸秆站立免耕田>秸秆还田免耕田。分析表明免耕有利于幼虫的越冬, 但免耕田麦穗受害较轻。旋耕对幼虫越冬不利, 但抽穗后受害较严重。在耕种方式是旋耕的情况下, 漫灌可加重吸浆虫的危害。研究结果有助于进一步了解大范围耕作方式的变迁对麦红吸浆虫发生的影响。     

不同抗性小麦品种上麦红吸浆虫幼虫的空间分布型与理论抽样数

【目的】为了解小麦品种抗性对麦红吸浆虫Sitodiplosis mosellana(Géhin)幼虫在麦穗上空间分布型的影响,为科学调查提供合理的抽样依据。【方法】2015年5月采用剥穗调查法对陕西省周至县试验田种植的4个抗虫和4个感虫小麦品种麦红吸浆虫幼虫危害进行调查,应用6种聚集度指标和Iwao M*?m回归法综合分析了幼虫在抗性不同小麦品种上的的空间分布结构。【结果】幼虫在抗、感小麦品种整穗及麦穗上、中、下部位上空间分布型一致,均呈聚集分布,但在抗虫品种上聚集强度大于感虫品种;抗、感小麦品种上分布的基本成分均为个体群,个体间相互吸引。聚集均数λ分析表明,幼虫在抗性较强品种上的聚集主要由小麦穗部化学物质和形态结构等环境因素引起,感虫品种上则由环境因素和成虫的产卵习性共同作用所致。幼虫在抗、感小麦品种上的发生趋势一致,均是上部发生最重,中部次之,下部最轻。根据Iwao回归法中的分布型参数,确立了幼虫在不同虫口密度和允许误差条件下的理论抽样数。【结论】麦红吸浆虫幼虫在抗性不同小麦品种上均呈聚集分布,调查时应根据当地栽培品种平均虫口密度选择适宜的抽样数量。     

一种改进的小麦吸浆虫淘土调查方法及其效果

在多年调查实践的基础上,提出了一种改进的小麦吸浆虫Sitodiplosismosettana(Gelin)淘土调查方法——袋筛箩瓷盘法,并通过试验比较了该方法与传统的箩筛法和近年提出的袋筛箩盐水法的淘捡效果。结果表明,袋筛箩瓷盘法淘捡幼虫多,时间花费少。袋筛箩瓷盘法与袋筛箩盐水法比较,两者的捡虫效果相当,袋筛箩瓷盘法花费时间略少,但不需用食盐调节水的比重,减少了经济支出;与箩筛法比较,箩筛法的捡虫效果仅是袋筛箩瓷盘法的83%,且花费时间比后者多1倍。建议在生产上及时大范围推广袋筛箩瓷盘法淘捡小麦吸浆虫技术。     

STUDIES ON SOIL POPULATION OF CONTARINIA PISI WINN. IN 1957 IN YORKSHIRE AND LANCASHIRE

For studying the population of pea-midge cocoons, larvae and pupae in the soil, a new method of examining the 'float' obtained from washing soil through the wet-extraction apparatus is described.
Examination of soil samples in the summer of 1957 from fields which carried heavily attacked pea crops in 1956 indicated that pupae were present at depths of 0–3, 3–6, 6–9 in., respectively, from 18 June onwards, and that the peak emergence of midges was in the period 28 June-2 July; observations on adult activity in pea fields confirmed this. Small numbers of pupae were recovered throughout July.
Similar studies on pea fields in 1957 showed the build-up of the cocoon population and the rate of pupation of this generation of larvae. The first flight of 1957 was composed of individuals from the 1956 generation and was far larger than the second flight, which was composed of some 1956 generation and part of the first 1957 generation.
There were indications that increases of temperature might accelerate pupation with a resulting earlier emergence of adults.
The size of midge populations recorded from soil from green pea and dry-harvesting pea fields tended to be similar and appeared to be related to sowing date.     

低温对麦红吸浆虫滞育解除及蜕皮激素受体基因EcR和热激蛋白基因Hsp70和Hsp90表达水平的影响

【目的】本研究旨在明确破茧率和破茧所需时间作为典型的专性幼虫期滞育昆虫麦红吸浆虫Sitodiplosis mosellana滞育解除指标的可行性,探讨蜕皮激素受体基因EcR和热激蛋白基因Hsp70和Hsp90在低温解除滞育中的作用。【方法】9月上旬采自田间的麦红吸浆虫滞育幼虫在低温(4℃)和自然变温处理不同时间(0~90 d)后转移至24℃化蛹,调查幼虫的破茧率、化蛹率及破茧和化蛹所需时间;采用qPCR技术分析4℃低温终止滞育并在24℃下恢复发育的幼虫EcR, Hsp70和Hsp90的mRNA水平。【结果】不同时间低温(4℃)和自然变温处理的麦红吸浆虫滞育幼虫破茧率和化蛹率以及破茧和化蛹所需时间均存在显著差异。未经低温(4℃)处理的幼虫在水分满足的条件下破茧率为71.3%,但均不能化蛹;低温(4℃)处理60 d内,随着处理时间的延长破茧率和化蛹率逐渐升高,破茧和化蛹所需时间逐渐缩短;与4℃低温处理30~60 d相比,自然变温处理30~60 d的幼虫化蛹率显著较低;4℃低温处理60 d和自然变温处理90 d后幼虫的化蛹率均超过91%。低温(4℃)处理显著提高了麦红吸浆虫幼虫EcR, Hsp70和Hsp90的表达量,其中处理30 d时其表达量最高,随着低温(4℃)处理时间的延长,表达量逐渐降低,大部分幼虫滞育解除后表达量趋于恒定。【结论】低温能显著促进麦红吸浆虫的滞育解除,效果优于9-10月自然变温;破茧率及破茧所需时间可作为评判麦红吸浆虫幼虫滞育强度的参考,但不能独立作为滞育解除的指标;EcR,Hsp70和Hsp90的表达水平与滞育强度密切相关,在麦红吸浆虫滞育解除中发挥潜在作用。     

THE FRIT FLY AND ALLIED STEM-BORING DIPTERA IN WINTER WHEAT AND HOST GRASSES

Sampling for stem-boring larvae was undertaken in 1954-56 on ley plots of Lolium perenne, Dactylis glomerata, Festuca arundinacea, F. rubra, Agrostis tenuis and Poa pratensis in randomized experiments at Hurley, Berks. The samples showed infestations by dipterous larvae, mainly species of Oscinella, Meromyza and Opomyza. The larvae showed preferences for specific grass hosts. More larvae were found where plots had been grazed throughout the season than where an early hay cut had preceded grazing. The total numbers of larvae varied between o and 688 per sq.yd. in November.
The larval populations of the leys were reflected in the populations in winter wheat which followed the plough-up of the leys. Populations of up to sixty-five larvae per sq.yd., mostly species of Oscinella , were found in the wheat in March. In 1956 a heavy larval infestation was associated with the death of considerable numbers of wheat plants.     

黑光灯诱集麦红吸浆虫成虫的数量及性比的变化

在河南省洛宁县小麦田夜间用黑光灯诱集麦红吸浆虫Sitodiplosis mosellana（Gehin）成虫,结果表明黑光灯对麦红吸浆虫成虫有极强的吸引作用,2010年4月30日至2010年5月19日之间日累计灯诱数量在9～5661头之间。5月7日是麦红吸浆虫发生的最高峰,当晚从20：00-23：30累计灯诱数量多达5661头;20：00以前天未完全黑,麦红吸浆虫成虫对黑光灯灯光不太敏感,灯诱数量较少;21：00-21：30时间段是麦红吸浆虫成虫夜间灯诱的高峰期,监测期间该时间段累计灯诱4134头;22：30以后吸浆虫活动显著减少。每晚灯诱数量与当日田间黄色粘板捕捉数量、网捕数量具有显著的相关关系,诱集到的红吸浆虫性比偏向雌性,表明黑光灯可以用作麦红吸浆虫成虫的监测工具。     

小麦品种（系）对麦红吸浆虫抗性指标筛选与抗性评价

【目的】筛选小麦对麦红吸浆虫Sitodiplosis mosellana抗性的准确鉴定方法, 明确生产上栽培小麦品种（系）对吸浆虫的抗性, 为抗虫小麦品种的筛选和利用提供科学依据。【方法】2012-2014年在陕西周至县建立麦红吸浆虫抗性鉴定圃, 调查并分析各参试小麦材料的估计损失率、粒被害率、穗被害率、单穗虫口和实际产量损失率及其相关性, 筛选出较准确的指标; 并以筛选到的指标为依据, 评估参试材料的抗性。【结果】估计损失率连续两年与其他3个抗性指标及实际产量损失率的相关性最强, 且均达到极显著水平。2012-2013年参试的85份和2013-2014年评估的80份材料中, 高抗、中抗和低抗材料合计分别为25份和40份; 重复种植的16份材料中, 14份两年均表现为抗性, 其中科农1006和晋麦47连续表现为高抗。【结论】估计损失率为具代表性且较准确的吸浆虫抗性鉴定指标。筛选出的抗性材料可作为抗吸浆虫的主推品种或后备品种, 也可作为亲本材料进行抗性育种研究。     

EFFECTS OF PREVIOUS WHEAT CROPS, SEED-RATE AND NITROGEN ON EYESPOT, TAKE-ALL, WEEDS AND YIELDS OF TWO VARIETIES OF WINTER WHEAT: FIELD EXPERIMENT 1954-56

In a replicated field experiment mean yields of wheat from plots that, in the preceding 2 years, had carried oats, beans or potatoes were 39.2 and 42.6 cwt. per acre in 1954 for Holdfast and Cappelle, respectively; 42.8 and 55.8 in 1955 and 34.9 and 49.6 in 1956. Previous wheat crops had more effect than any other treatment in increasing the incidence of eyespot, take-all and weeds and in decreasing the number of ears per unit area and the yield of grain. In 1956 on plots carrying the first, second and third successive wheat crops the percentages of straws with eyespot were respectively 12, 54 and 42 and with take-all 0.1, 1 and 16. Cappelle was less severely infected by eyespot than Holdfast. The second and third successive wheat crops yielded an average of 23.3 cwt./acre less than the first wheat crop. Cappelle consistently yielded more than Holdfast, the mean difference being 13.8 cwt./acre after potatoes but only 3.8 cwt./acre after two wheat crops. The higher seed-rate gave an average increase in grain yield of 3.3 cwt./acre; but where eyespot and take-all were both severe the lower seed-rate yielded as much total and more dressed grain than the higher. Wheat given a spring top dressing of 6 cwt./acre Nitro-Chalk yielded an average of 4 cwt./acre more grain than wheat given 3 cwt./acre.     

山东省麦红吸浆虫发生环境的初步分析

本初步分析丁山东省麦红吸浆虫发生的环境条件．结果表明．毗邻四省是麦红吸浆虫的高发区．为扩散到我省提供了虫源条件．鲁南各有虫县常年的4月上旬～5月上旬的温度和麦田湿度有利于麦红吸浆虫的化蛹和羽化．麦红吸浆虫成虫峰期和小麦抽穗期相吻合．为麦红吸浆虫产卵提供了条件．小麦品种混杂,增加了田间感虫机会．地膜蒜地形成了麦红吸浆虫的早期虫源．田间种群数量的积累．666停用后没有很好的替代土壤处理药剂．也是有利于麦红吸浆虫发生的条件．     

小麦吸浆虫滞育幼虫甘油含量的季节变化(英文)

采用比色分析方法测定了小麦吸浆虫Sitodiplosis mosellana滞育期间幼虫甘油含量的季节变化。结果表明,幼虫离穗入土以前,甘油含量很低,仅为2.96±1.19μg/mg。幼虫离穗入土后,甘油含量急剧升高。入土后5d,甘油含量即上升为6.58±1.11μg/mg;至入土后17d,甘油含量达到高峰,12.21±2.21μg/mg。以后随时间的短期变化其含量变化不大,但随季节变化表现了一定的规律性,呈现了上升——下降——再上升——再下降的变化趋势,即夏季和冬季含量较高,秋季和春季含量较低。结茧幼虫和裸露幼虫比较,结茧幼虫的甘油含量在盛夏和冬季略高于裸露幼虫,秋季和春季时二者含量相当,两者在统计学上并无显著的差异。同一季节的当年滞育幼虫和进入第2年滞育幼虫的甘油含量无明显差异。由此可见,小麦吸浆虫幼虫滞育期间,甘油含量受季节或滞育深度的影响较大。     

太行山前平原麦田昆虫种类调查及4种药剂对麦红吸浆虫的药效实验

以藁城为例,采用淘土、扫网、挂黄板等方法对太行山前平原麦田昆虫群落进行了调查,结果表明该区域超高产麦田昆虫种类相对较少,总计22种,隶属于6目14科。害虫主要有2类,吸浆虫类和麦蚜类。小麦吸浆虫以麦红吸浆虫为主。天敌昆虫常见有蚜茧蜂、食蚜蝇、草蛉和瓢虫4类。采用氧乐果、毒死蜱、高效氯氰菊酯、吡虫啉4种常用药剂对麦红吸浆虫成虫进行了田间药效实验,结果表明上述4种药剂对麦红吸浆虫均有较好的防治效果,虫口减退率均在80%以上。其虫口减退率从高到低依次为:氧乐果、毒死蜱、高效氯氰菊酯、吡虫啉。建议根据麦红吸浆虫的发生情况,选择中低毒药剂毒死蜱、高效氯氰菊酯、吡虫啉交替使用。     

CHANGES OF GLYCEROL CONTENT IN DIAPAUSE LARVAE OF THE ORANGE WHEAT BLOSSOM MIDGE, SITODIPLOSIS MOSELLANA (GEHIN) IN VARIOUS SEASONS

Abstract  The glycerol contents in diapause larvae of the orange wheat blossom midge, Sitodiplosis mosellana (Gehin), collected from various seasons, were measured. The results showed that there was less glycerol content in larvae during living on the wheat head. Content of glycerol began to increase significantly when the larvae left the wheat head and entered the soil. A change trend of upper- lower- upper- lower in larvae glycerol contents during diapause in soil was observed from June to April of next year. More glycerol could be examined in larvae collected in summer and winter than in spring and autumn. There was not more glycerol in cocooned larvae than that in non-cocooned larvae during various seasons from the point of statistics. Comparing the glycerol content of larvae being diapause in the first year with that of larvae in the second year, there was yet no obvious difference when larvae were collected in the same season belonged to different years. Therefore, it is shown that the content of glycerol in larvae of the wheat midge in diapause is affected mainly by the seasons or diapause intensity.     

白眉野草螟的生物学特性和监测防控对策

【目的】白眉野草螟Agriphila aeneociliella是近年来在山东莱州市、山西泽州县等地新发现的小麦害虫,对其生物学特性进行观察和研究,以期为有效监控提供科学依据。【方法】通过田间调查、网室观察、配对饲养和灯光诱测等方法,系统研究了白眉野草螟年生活史与田间生活习性。【结果】在我国黄淮海麦区,白眉野草螟1年发生l代,11月至翌年2月以低龄幼虫越冬,3月至4月为害麦苗,5月至8月以老熟幼虫结土茧滞育越夏,9月至10月化蛹羽化、交配产卵,并孵化出幼虫越冬。成虫具有趋光性,产卵在土壤颗粒缝隙中或土表;幼虫喜趋嫩为害,田间呈点片分布;越冬幼虫抗寒性强;滞育茧不耐水淹。【结论】秋季成虫羽化期、早春低龄幼虫为害始期、夏季滞育期是白眉野草螟监测防控的关键时期。     

Survival of mature larvae of codling moth (Cydia pomonella) on apple trees and ground

The effects of predation by carabid and staphylinid beetles and birds (blue- and great-tits) on mature larvae of the codling moth Cydia pomonella were investigated in a field experiment. The number of predatory beetles on the ground beneath eight of 16 apple trees was reduced by an insecticide spray, and tits were excluded from the trunks and lower branches of eight trees by means of Terylene netting. Beetles had no significant effect on survival of larvae on trees, but only 8% of larvae survived to adulthood on trees exposed to blue- and great-tits, whereas on trees protected from them 48% survived. Larvae were taken rapidly by the tits from the time larvae first built cocoons in summer and, by the time the majority of larvae had emerged from apples in late summer or autumn, tits had removed most from cocoons beneath flakes of bark glued to trees. Thus tits fed on larvae mainly in summer and autumn. On trees protected from tits, 8% of mature larvae were killed by fungi, of which Verticillium lecanii was most important. It was calculated that, of the larvae maturing in apples, 44% failed to build cocoons on the trees, 47% were taken by tits, then 1% were killed by fungi. Larvae failing to build cocoons on trees may build them on the ground. Of larvae in cocoons planted on or in the ground in 1975, only one (0.3%) persisted through the winter; 98.6% disappeared, and 1.1% were found dead, covered by fungi; in 1976, all larvae disappeared by December. Larvae disappeared even in the absence of predators, and are thought to have moved in response to damp ground conditions.     

Hessian fly-associated bacteria: transmission, essentiality, and composition

Plant-feeding insects have been recently found to use microbes to manipulate host plant physiology and morphology. Gall midges are one of the largest groups of insects that manipulate host plants extensively. Hessian fly (HF, Mayetiola destructor) is an important pest of wheat and a model system for studying gall midges. To examine the role of bacteria in parasitism, a systematic analysis of bacteria associated with HF was performed for the first time. Diverse bacteria were found in different developmental HF stages. Fluorescent in situ hybridization detected a bacteriocyte-like structure in developing eggs. Bacterial DNA was also detected in eggs by PCR using primers targeted to different bacterial groups. These results indicated that HF hosted different types of bacteria that were maternally transmitted to the next generation. Eliminating bacteria from the insect with antibiotics resulted in high mortality of HF larvae, indicating that symbiotic bacteria are essential for the insect to survive on wheat seedlings. A preliminary survey identified various types of bacteria associated with different HF stages, including the genera Enterobacter, Pantoea, Stenotrophomonas, Pseudomonas, Bacillus, Ochrobactrum, Acinetobacter, Alcaligenes, Nitrosomonas, Arcanobacterium, Microbacterium, Paenibacillus, and Klebsiella. Similar bacteria were also found specifically in HF-infested susceptible wheat, suggesting that HF larvae had either transmitted bacteria into plant tissue or brought secondary infection of bacteria to the wheat host. The bacteria associated with wheat seedlings may play an essential role in the wheat-HF interaction.     

Studies of wireworm populations

A method has been developed, and is here briefly described, by means of which all the wireworm larvae of all stages can be collected from soil samples. By use of that method, complete wireworm populations have been obtained from soil samples of three types, two of which provide large homogeneous populations for detailed study while the third gives information about the seasonal and spatial infestation of fields. These collections show that the wireworm population of English pasture land is on the average about three times as large as has been commonly supposed. Populations have been found ranging up to ten millions per acre in the top 12 in. of soil. In two pastures studied intensively throughout the year, the wireworm population has been found to consist of large numbers of small larvae, decreasing numbers of larger larvae, and comparatively few of the very large larvae that have usually been allowed to represent the population. Such a composition is shown to be characteristic of wireworm populations under old grass at all seasons of the year and in several fields in different parts of the country. This result suggests that in research on the wireworm problem it is desirable to take into consideration the whole wireworm population throughout the year, not merely the large larvae during the cropping season.     

STUDIES OF FLUCTUATIONS IN INSECT POPULATIONS XIII. AN IMPROVED METHOD OF ASCERTAINING THE CORRECT DATE TO SAMPLE WHEN ASSESSING LARVAL INFESTATIONS OF THE WHEAT-BLOSSOM MIDGES

Fully fed larvae of the wheat-blossom midges need moist conditions in order to descend from the ears to the soil. A dry spell coinciding with the fully fed stage therefore causes an accumulation of larvae, which subsequently leave the ears in a body when rain comes. Conversely, in wet weather each larva leaves the wheat as soon as it finishes feeding, and, since all the eggs are not laid on the same day, the descent will then be a gradual process.
A method is described of taking small samples of wheat ears at frequent intervals, thus facilitating the determination of the correct date on which to take the main sample for the assessment of infestation by the two wheat-blossom midges.