Western corn rootworm adult movement and possible egg laying in fields bordering maize

Abstract:  Western corn rootworm (WCR), Diabrotica virgifera virgifera LeConte, larval damage in maize following soybean was observed in Croatia in 2003 along the edges and within soybean fields which bordered continuous maize fields in previous year. The explanation was that WCR adults moved from the continuous maize to the neighbouring soybean fields to lay eggs. This study was designed to measure how far WCR adults will enter into neighbouring fields to lay eggs. The WCR adult population was monitored in continuous maize fields in 2003 and 2005 by using Pherocon^® AM non-baited yellow sticky traps in the middle and on the borders of the maize field and at different distances and directions into neighbouring fields planted by wheat and soybean. Larval presence and root damage ratings (Iowa State University 1–6 ) were recorded at different locations within the maize field in following years. Approximately, the same concentration of WCR adults was recorded along the edges of the maize fields as recorded in the centres of those fields. A significant number of WCR adults was recorded up to a distance of 50 m into neighbouring fields. Regression analysis showed medium negative correlation between distance from previous maize field and root damage in the following year. Findings indicate that WCR egg lying can reach approximately 20 m into fields neighbouring maize fields and that significant root damage caused by WCR larvae in first-year maize following soybean and wheat can happen up to a distance of 20 m into those fields. Most farmers's fields in Croatia are up to approximately 50 m wide. As an edge effect for WCR egg laying can reach approximately 20 m into fields neighbouring maize fields, our research results indicate that it is possible to see WCR larval damage in rotated fields without those WCR's being the variant form.     

小麦间作大蒜或油菜对麦长管蚜及其主要天敌种群动态的影响

麦长管蚜是我国冬小麦产区的重要害虫.试验探索了不同间作方式对麦长管蚜及其主要天敌的影响.结果表明,在调查期内,麦-油(油菜)间作田和麦-蒜(大蒜)间作田中麦长管蚜无翅蚜的种群密度多显著低于单作田;麦-油间作田中有较高的瓢虫种群密度和瓢蚜比;5月2日前,麦-油间作田中蚜茧蜂的种群密度高于单作田和麦-蒜间作田;5月5日后,麦-油间作田的僵蚜率和蜂/蚜比也显著高于单作田和麦-蒜间作田;麦-蒜间作田有翅蚜的种群数量较高,但瓢虫和蚜茧蜂的种群数量无明显变化.麦-油间作和麦-蒜间作均能对麦田中麦长管蚜起到较好的控制作用.     

农业景观结构对麦蚜寄生蜂群落组成的影响

麦蚜是中国北方小麦上最重要的害虫之一,既能直接刺吸危害也可传播多种病毒,但麦蚜通常的危害期只有2～3个月。随着现代农业与设施农业的发展,农业景观结构发生了巨大的改变,整个麦蚜寄生蜂群落也随之发生了显著的变化。经典假说认为复杂的农业景观能够维持局部的物种多样性及种间关系,也能够维持更大的天敌资源。作者在4种不同的麦田景观类型下研究了麦蚜及寄生蜂的群落结构,发现简单农业景观与复杂农业景观中寄生蜂寄生率与多样性差异不显著,但初寄生蜂在800m2左右的生境面积中寄生率与多样性最高,重寄生蜂却并没有表现出这种分布,而在更大的生境中重寄生率与多样性更高。研究结果表明:1)生境面积是影响麦蚜及寄生蜂群落的重要因子,2)简单农业景观与复杂农业景观下麦蚜及寄生蜂群落多样性差异不显著,3)一定程度的生境破碎化能够促进初寄生蜂的种群而抑制重寄生蜂的种群,但高度的生境破碎化会同时抑制2种寄生蜂的种群。     

Wireworms and the sugar-beet crop; field trials and observations

Observations on wireworms in the sugar-beet crop during 1937–40 indicated the importance of alternative food, such as buried turf, weeds, excess seedlings and interdrilled wheat in determining the degree of injury to the crop.
In 1938, out of thirty-six recorded fields growing sugar beet after ploughed-up grass only one suffered severe wireworm damage. Six of these fields were selected for resowing with sugar beet in 1939, and all suffered moderate or severe attacks. Several other fields in their first year from grass showed only slight damage. These observations were supported by an analysis of the Norfolk War Agricultural Committee crop records for 1940.
Seven trials were carried out in 1939 to determine the effect of increasing the seed rate from normal (about 14–16 lb./acre) to 17–25 lb., and of interdrilling with wheat. In three trials, increasing the seed rate gave significantly higher plant populations before singling. It gave significant increases after singling in one out of two trials. However, in the one trial harvested the increase in 'washed beet' was only 7.6% and 'total sugar' 15%. Interdrilling with wheat at 40–70 lb./acre gave significant increases in the plant population before singling in three out of five trials, and after singling in three out of four trials. Increased plant populations both before and after singling were obtained in two other trials with alternating treatments. Increased seed rate and interdrilled wheat together gave greatly improved plant populations before singling in each of two trials and after singling in the one trial where such an observation was possible.     

Investigations on the gout fly (Chlorops pumilionis Bjerk.) in Devon and Cornwall

Field observations from 1943 to 1946 on attacks by gout fly on wheat in south-west England show that there are two generations of the fly during the year, the first emerging in May from October-laid eggs and the second emerging in late July and early August. The first generation severely damages spring wheat and may also attack very late sown and backward autumn wheat; wheat not above ground before 20 October escapes attack by the second generation. In south-west England, the optimum period for drilling wheat to escape gout-fly damage is mid-October. In this area, both generations of gout fly show a marked preference for wheat; attacks on barley are negligible.     

Influence of Edaphic Factors and Previous Crop on Pratylenchus spp. Population Densities in Potato

Root and soil samples from commercial potato fields were assayed for nematodes in 1983 and 1984. Pratylenchus spp. population densities in Suffolk County, New York, were consistently, though not always statistically, higher in potato fields that had been planted to rye or wheat rather than potatoes during the previous growing season. Regardless of the previous crop, population densities in the two potato production areas in Suffolk County differed significantly: population densities on the south fork were 1.9-5.5 times higher than those on the north fork. Species prevalence differed significantly on the two forks but was not related to the previous year''s crop. P. penetrans and P. crenatus were found primarily on the north and south forks, respectively. Differences in species distribution were associated with differences in soil types. P. crenatus was usually found on loams and silt loams, but P. penetrans was found more frequently on sandy soils.     

Induced resistance to herbivores and the information content of early season attack

Current models of induced plant defenses all assume that herbivory is predictable. Present damage must provide information about the likelihood of future attack. We tested this assumption by measuring the relationship between damage early in the season and the number of subsequent attacks by cotton leaf perforators, Bucculatrix thurberiella, to plants of wild cotton, Gossypium thurberi, at three sites in the Sonoran desert. Damage early in the season was a good predictor of the number of new mines initiated throughout the season for plants in Florida Canyon. This result was neither evidence for nor against induced resistance nor was it a consequence of induced resistance. This is because induced resistance has been found to affect survival of miners but previous damage did not affect the initiation of new mines. At two other sites, early damage was not related to future attacks. This difference in predictability of attack may be related to inducibility of plants since Florida Canyon was the only site that provided evidence of induced resistance in a previous study. We found no evidence that the usefulness of information based on early season damage decreased as the season progressed. Assessment of attacks on all shoots of the plant was more useful at predicting later damage to an assay shoot than was assessment of solely the assay shoot. Number of mines, produced only by G. thurberiella, was a better predictor of subsequent attacks by G. thurberiella than were chews and rasps which were made by many different herbivores. However, general chewing damage was a better indicator of the level of induction against G. thurberiella than was the more specific mining damage. Plants may respond more to chewing damage even though mining damage is a better predictor of future attacks.     

Influence of certain soil factors on chocolate spot of beans

In the summer of 1941 chocolate spot of beans was widespread in the South-Eastern Agricultural Province and caused much damage to the crop. Soil samples were collected from forty-nine affected fields on a variety of soil types, and the relation between the severity of attack by chocolate spot and the texture, pH, available potassium and available phosphorus determined. Severity of attack was classified into three grades: 'slight', in which only spotting of the foliage occurred; 'moderate', in which death of leaves and blossoms on the three or four lowest nodes occurred; and 'severe', in which there was generally a total loss of crop. No significant relation between severity of attack and soil texture, pH or available potassium was found. A highly significant relation was found to exist between the severity of attack and the amount of available phosphorus in the soil as determined by the method of soil analysis used in this Province. Damage by chocolate spot was generally slight on soils containing 'medium to medium high' or higher amounts of available phosphorus, and generally severe on soils containing low amounts of available phosphorus.     

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。     

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．     

Morphological traits of wheat (Triticum aestivum L.) associated with resistance to shoot fly,Atherigona approximata Malloch

Shoot flies (Atherigona spp.) are the members of muscidae family which have got economic importance as pest of several crops of Gramineae family mostly cereals and millets. One of the most effective management strategies for controlling shoot fly is the use of resistant wheat cultivars carrying specific resistant traits. Among thirty wheat genotypes screened at the University of Agricultural Sciences, Dharwad-Karnataka (India), two advanced germplasms UAS BW-12417 and UAS BW-11110 recorded least oviposition and dead heart due to shoot fly and found to be less preferred by Atherigona approximata Malloch. The morphological traits of different wheat genotypes revealed a significant negative correlation of shoot fly oviposition and dead heart with leaf length, leaf length to breadth ratio, seedling height, average seedling growth rate, seedling vigour, leaf glossiness and trichome density of wheat leaves, which indicated the enhanced shoot fly infestation as decrease in the values of above-mentioned morphological traits. Meanwhile, increase in leaf breadth and leaf area of wheat genotype aggrandised the oviposition and dead heart damage by shoot fly. Under the changing climate where, the minor insect pests attaining major pest status, the present investigation would pave way for breeders to tailor future breeding programmes to evolve shoot fly resistant hybrids with high yielding traits.     

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。     

Short-term forecasting of wheat yield loss caused by the grain aphid (Sitobion avenae) in summer

A damage model was used to take into account the effect on winter wheat yield of the size, duration and timing of Sitobion avenae infestation in summer, and the influence of insecticide applications. It was validated as far as possible using available data, and appeared to be sufficiently accurate to be useful. The model was applied to a total of 32 winter wheat fields over the period 1975 to 1983 in eastern England and the Netherlands, to obtain estimates of yield losses associated with not applying insecticides at the end of ear emergence (G.S. 59), mid-anthesis (G.S. 65) or the end of anthesis (G.S. 69). These estimates of future yield losses were related in multiple regressions to the number of S. avenae per tiller at the time the insecticide was applied, and the rate of population increase over the previous few days. Basing the decision about whether to apply insecticide on forecasts from the multiple regression equations appeared to be slightly more profitable than prophylactic spraying when the chemical cost alone was considered, but substantially more profitable when the application cost and wheeling loss were also taken into account. The strategy minimising losses involved forecasts at all three crop growth stages. It was validated using a further 21 fields studied in 1984 and 1985, and gave better results than the EPIPRE system, which over-estimated the number of fields requiring spraying, and the economic threshold of George & Gair (1979), which under-estimated the number requiring spraying. However, the accuracy of the damage model needs to be checked against measured yield losses in order to establish the success of the multiple regression strategy conclusively.     

Observations on take-all and eyespot diseases of wheat in Yorkshire

Wheat crops were surveyed in Yorkshire from 1944 to 1946 on farms where crops were reported to be unsatisfactory. Take-all ( Ophiobolus graminis (Sacc.) Sacc.) and eyespot ( Cercosporella herpotrichoides Fron.) were both found to be present; the latter is the most serious trouble on the better wheat lands.
The variation in the incidence of these diseases on selected farms during the three seasons has been compared.
The effect of rotation has been examined; both diseases were found to be encouraged by too frequent cropping with wheat or barley. The incidence of disease in wheat crops following a 1-year seeds ley was found to be influenced by the nurse crop used to undersow the seeds, and also by the time at which the ley was ploughed up. Oats were found to be preferable to either wheat or barley as a nurse crop, and in 1946 late ploughing considerably reduced the amount of eyespot disease present in the following wheat crop.
A 1-year ley is considered to be of too short a duration to ensure the disappearance from the soil of Ophiobolus graminis and Cercosporella herpotrichoides surviving from the previous crop, and a period of 2–3 years is suggested as being desirable.     

SLUG DAMAGE AND NUMBER OF SLUGS (GASTROPODA: PULMONATA) IN WINTER WHEAT IN FIELDS WITH SOWN WILDFLOWER STRIPS

Previous observations have shown that slugs found favourableconditions for reproduction in wildflower strips and that theycaused high damage to oilseed rape adjacent to the strips. Inthe current study slug numbers and damage were estimated inwildflower strips and at different distances from the stripsinto winter wheat crops, from 1994 to 1996. Slug damage wasestimated using an index of defoliation and slug numbers andactivity were measured using wheat bran traps. Investigationsbegan when winter wheat seedlings emerged and lasted for fiveweeks. Slug damage was never severe in any of the fields studied.In most fields, slug damage was higher close to the wildflowerstrips than at greater distances from the strips. The decliningslug damage with increasing distances from the wildflowers stripswas related to the distribution pattern of juvenile Arion lusitanicus,suggesting that this species was responsible for the higherdamage near the strips. Other slug species (Deroceras reticulatum,Arion fasciatus, Deroceras laeve) were more or less evenly distributedover the field or were almost entirely confined to the wildflowerstrips. Results showed that winter wheat was not at risk fromslug feeding in spite of the establishment of wildflower stripsand that therefore the application of molluscicide along thestrips is unnecessary. (Received 23 June 1997; accepted 17 October 1997)     

Methods of Predicting Risks of Wheat Damage by White-Fronted Geese

Abstract: Accurately predicting occurrence of wildlife damage is crucial for effective management of problematic wildlife species, because accurate predication allows deterrence efforts to be focused at sites or times where damage is most likely. We explored methods to predict occurrence of white-fronted geese (Anser albifrons) grazing in wheat fields around Lake Miyajimanuma, Japan. Depletion of waste rice grains caused geese to forage on wheat leaves in spring, reducing wheat harvest in grazed fields. The cumulative number of goose-days per hectare of rice-planted area from the beginning of the staging period explained the variation in the proportion of geese foraging in wheat fields. A logistic regression model on the location of vulnerable fields showed that goose grazing was likely to occur in wheat fields far from roads and windbreaks and those close to (within 1,000–2,000 m of) previously grazed fields. Although probability of occurrence of goose grazing was initially low in wheat fields with scaring devices, effectiveness of such devices was lost over the 4 survey years. We recommend farmers in the study area prepare counter-damage measures when the cumulative number of goose-days per rice-planted area approaches a threshold above which some geese are predicted to start foraging on wheat (e.g., 199.46 goose-days/ha rice × 28.95 for 10% of geese foraging on wheat). Further, farmers should be aware that grazing on wheat is more likely to occur if wheat fields within 1,000–2,000 m have already been exploited during that particular season and should concentrate deterrence efforts to wheat fields that are far from roads and windbreaks. Systematic deployment of scaring devices over the entire habitat has a risk of accelerating the decline in effectiveness. Thus, we need methods to retard goose habituation to scaring devices, such as scaring with guns, providing alternative feeding sites, and preventing diet change by geese.     

Field efficacy of insect pathogen,botanical, and jasmonic acid for the management of wheat midge Sitodiplosis mosellana and the impact on adult parasitoid Macroglenes penetrans populations in spring wheat

The wheat midge, Sitodiplosis mosellana, is a serious pest of wheat worldwide. In North America, management of S. mosellana in spring wheat relies on the timely application of pesticides, based on midge adults levels caught in pheromone traps or seen via field scouting during wheat heading. In this context, biopesticides can be an effective alternative to pesticides for controlling S. mosellana within an Integrated Pest Management program. A field study using insect pathogenic fungus Beauveria bassiana GHA, nematode Steinernema Jeltiae with Barricade polymer gel 1%, pyrethrin, combined formulations of B. bassiana GHA and pyrethrin, Jasmonic acid (JA) and chlorpyrifos (chemical check) was performed to determine to which extent they affect midge larval populations, kernel damage levels, grain yield, and quality, and the impacts on adult parasitoid Macroglenes penetrans populations. The results indicated that biopesticides JA and S. Jeltiae were the most effective in reducing larval populations and kernel damage levels, and produced a higher spring wheat yield when compared to the water control at both study locations (East Valier and North Valier, Montana, USA). Increased test weight in wheat had been recorded with two previous biopesticides at East Valier but not for North Valier, when compared over water control. These results were comparable in efficacy to the chlorpyrifos. This study also suggested that B. bassiana and pyrethrin may work synergistically, as exemplified by lower total larval populations and kernel damage levels when applied together. This study did not demonstrate the effect of any treatments on M. penetrans populations.     

葱斑潜蝇的生物学特性

葱斑潜蝇 1年发生 4～ 5代 ,世代重叠严重。以蛹在土中越冬 ,翌年 5月初越冬蛹羽化 ,5月上旬越冬代成虫开始产卵。室内自然变温饲养 ,得到全世代的发育起始温度为 10 .34℃ ,有效积温为 2 57.2 5日度。该虫主要以幼虫潜食叶肉造成危害。周年发生 ,呈春、秋季两个高峰 ,以春季为重。田间天敌主要是潜蝇姬小蜂 Diglyphus sp.、稀网姬小蜂 Euplectrus sp.以及金小蜂科 Pteromalidae中的一种寄生蜂 ,均为幼虫寄生。     

Evidence for gene flow and local clonal selection in field populations of the grain aphid (Sitobion avenae) in Britain revealed using microsatellites

Samples of the grain aphid, Sitobion avenae (F.), a major European pest of cereals, were collected in June and July 1997 from fields sown with winter wheat in a rough transect south-west of Rothamsted, UK. These aphids were genotyped at four microsatellite loci known from previous studies to be highly polymorphic. Allelic frequencies were similar between samples collected in the fields and in the 12.2 m high suction trap at Rothamsted, and there were many widespread genotypes (clones), providing evidence that the species is highly migratory. However, field samples were found to display a high level of genotypic heterogeneity (= variable clonal composition), most probably the result of clonal selection. The suction trap genotypes sample were slightly different from the field samples, indicative of the inclusion of genotypes from plant hosts (cereals and grasses, Poaceae) other than winter wheat and/or genotype-biased emigration from the field. The relevance of these data to modelling of aphid outbreaks is briefly discussed.     

尿素施用量对小麦根际土壤微生物数量及土壤酶活性的影响

在大田高产条件下,研究了不同尿素施用量下两种不同穗型小麦品种“兰考矮早8”和“豫麦49—198”根际微生物数量和土壤酶活性的变化。结果表明：微生物数量随小麦生育时期的进行呈规律性变化,其中微生物总量在拔节期和抽穗期时数量较多。尿素施用量对小麦根际微生物数量和酶活性均产生一定的影响,并且处理间差异达到显著水平。两个小麦品种根际微生物总量、细菌、放线菌、真菌数量随着尿素施用量的增加呈先上升后下降的趋势,但两个品种根际微生物数量最高时的尿素量略有差异。同一生育时期,随着尿素施用量的提高,土壤蛋白酶、过氧化氢酶呈先增加后降低的变化趋势,以他（391kg／hm^2）或T3（586kg／hm^2）处理的酶活性较高,T4（782kg／hm^2）处理的酶活性略有降低;脲酶活性则呈上升趋势,以T4（782kg／hm^2）处理的脲酶活性最大。表明适宜尿素施用量有益于小麦根际微生物数量和酶活性的提高,过高则微生物数量和酶活性下降。