Field-evolved resistance to Bt toxin Cry1Ac in the pink bollworm, Pectinophora gossypiella (Saunders) (Lepidoptera: Gelechiidae), from India

BACKGROUND: The pink bollworm is one of the most destructive pests of cotton. Transgenic cotton producing Bt toxin Cry1Ac or a combination of Cry1Ac and Cry2Ab2 has been used effectively against this pest. However, some other insects have evolved resistance to Bt toxins in the field. During the 2007–2008 and 2008–2009 seasons, pink bollworm populations in India were surveyed to evaluate their responses to Cry1Ac and seed powder containing Cry1Ac and Cry2Ab2. RESULTS: The results provide evidence that resistance to Cry1Ac had evolved by 2008 in a population sampled from non‐Bt cotton in the Amreli district of Gujarat in western India. The median lethal concentration of Cry1Ac for five‐day‐old larvae (LC₅₀) was significantly higher for insects derived in 2008 from Amreli than for any of the other field populations tested from four locations in India. For Cry1Ac, the mean LC₅₀ for the strain derived from Amreli in 2008 was 44 times higher than for the most susceptible population. However, for seed powder of Bollgard II containing primarily Cry2Ab2, the 2008 Amreli population was only slightly less susceptible than the most susceptible population. CONCLUSIONS: The data reported here constitute the first evidence of field‐evolved resistance of pink bollworm to Cry1Ac. This initial evidence spurred more extensive evaluations during the 2009–2010 growing season, which confirmed field‐evolved resistance to Cry1Ac in Amreli. The lack of cross‐resistance to Cry2Ab2 suggests that plants producing this toxin are likely to be more effective against resistant populations than plants producing only Cry1Ac. Copyright © 2011 Society of Chemical Industry     

2种不育剂和1种抗凝血剂对藏北草原高原鼠兔的控制效果

2012年4月至2013年4月在藏北草原进行了炔雌醚、莪术醇和增效敌鼠钠盐控鼠试验。均配制成青稞药饵,投放药饵后第20、75和350天进行控效调查。结果显示:炔雌醚具杀灭高原鼠兔作用,20d校正灭效达72.24%,对成年雌雄鼠繁殖器官均能起到明显损坏作用,且适口性最好;增效敌鼠钠盐控鼠效果最好,20d校正灭效达94.46%;莪术醇也有一定效果,75d幼体比最低,总体看,3种药物均具有一定控制效果,有一定实际应用潜力,但还需进一步试验验证其控鼠效果。     

Evidence that wheat cultivars differ in their ability to build up inoculum of the take‐all fungus,Gaeumannomyces graminis var. tritici,under a first wheat crop

The effect of wheat cultivar on the build‐up of take‐all inoculum during a first wheat crop was measured after harvest using a soil core bioassay in field experiments over five growing seasons (2003–2008). Cultivar differences in individual years were explored by analysis of variance and a cross‐season Residual Maximum Likelihood (REML) variance components analysis was used to compare differences in those cultivars present in all years. Differences between cultivars in the build‐up of inoculum were close to or at significance in two of the five trial years (2004 P < 0·05; 2006 P < 0·07), and current commercially listed cultivars were represented at both extremes of the range. In 2007 and 2008, when environmental conditions were most favourable for inoculum build‐up, differences were not significant (P < 0·3). In 2005 the presence of Phialophora spp. at the trial site restricted the build‐up of take‐all inoculum under all cultivars. The cross season REML variance components analysis detected significant differences (range: 3·4–47·8% roots infected in the soil core bioassay; P < 0·01) between the nine cultivars present in all years (excluding 2005). This is the first evidence of relatively consistent differences between hexaploid wheat cultivars in their interactions with the take‐all fungus, and this could give an indication of those cultivars that could be grown as a first wheat crop, in order to reduce the risk of damaging take‐all in a second wheat crop. This phenomenon has been named the take‐all inoculum build‐up (TAB) trait.     

不同季节出生的布氏田鼠繁殖发育模式分析

布氏田鼠是我国内蒙古东部草原的主要害鼠之一,具有明显的季节性繁殖特征。本研究于2013年采集内蒙古东乌珠穆沁旗草原繁殖盛期(6-7月)和末期(8月)的布氏田鼠,比较了种群组成和繁殖器官的季节特点。结果表明,从繁殖盛期到末期,越冬鼠比例呈现下降趋势,当年鼠比例逐渐上升。不同年龄、性别的布氏田鼠存在明显的繁殖状态上的差异:与当年出生个体相比,越冬鼠参与繁殖时间长,在整个繁殖期都参与繁殖,是繁殖期尤其是繁殖早期种群繁殖的主力;与雄鼠相比,当年出生雌鼠会更多参与繁殖,在6月中旬的繁殖盛期,当年生雌鼠的怀孕率达39%,而当年雄鼠未参与繁殖。这些结果表明,不同性别、不同时期出生的布氏田鼠采取了不同的繁殖策略,体现为各自在种群繁殖中的贡献不同,因此在分析其暴发成灾机制时应考虑种群中性别和年龄组成。     

Population structure and reproductive mode of Didymella fabae in Syria

Didymella fabae is a highly destructive fungal pathogen of faba bean (Vicia faba) that represents a significant yield‐limiting biotic constraint in all locations where the crop is grown. However, nothing is known about the population structure of this pathogen anywhere in the world. Population genetic analyses employing 18 sequence‐tagged microsatellite (STMS) markers covering eight genetic linkage groups and a PCR‐based mating type marker were used to elucidate the genetic structure and reproductive mode of the pathogen in three populations in Syria. High gene diversity within populations but low genetic differentiation among populations was observed and the entire collection of isolates was assigned to a single genetic population using a Bayesian clustering algorithm. Independent analyses were performed based on four unlinked sets of STMS markers to infer reproductive mode. A simulation approach was used to estimate which of the repeated multilocus genotypes were probably the result of asexual reproduction and should be clone‐corrected. A 1:1 ratio of mating types could not be rejected in any clone‐corrected population, probably due to small sample sizes. Likewise, frequency of clones and sample size, but not marker linkage, had strong effects on multilocus gametic disequilibrium. The null hypothesis of random mating was rejected in the majority of populations for both non‐clone‐corrected and clone‐corrected samples and with four sets of unlinked markers indicating a predominance of asexual reproduction in these populations. This represents the first detailed screening of clonal and genetic composition of D. fabae populations in Syria.     

大隆(TALON)灭鼠的试验研究

作者于1980年3～4月和7～8月间,在青海省天峻县和门源县草甸草原牧场进行了新杀鼠剂大隆杀灭我国西北草原主要害鼠—高原鼠兔(Ochotonacurzoniae)、中华鼢鼠(Myospalax fontanieri kukunoriensis)的试验研究。大隆对鼠兔的LD_(50)为0.1380mg/kg(0.1192～0.1568mg/kg),对鼢鼠的LD_(50)为0.4388mg/kg(0.2742～0.7022mg/kg)。 0.015％、0.030％和0.060％三种浓度大隆毒饵对鼠兔的现场灭效均达90％以上。一系列试验证明,大隆对草原害鼠的毒力强,使用浓度低,适口性好,无明显的耐药性,对天敌的危害性小。作者认为大隆可以应用于草原灭鼠,并可能有较好的前景。     

Regulatory Mechanisms and Dynamics of an Island Population of Clethrionomys glareolus (Schreber, 1780)1

A scheme of density regulation in an island population of Clethrionomys glareolus (Schreber) is presented. The key factor for the changes in numbers was mortality of untrappable voles. A peak in population numbers followed low mortality of the spring generation, and, in peak years, mortality of the autumn generation was always high. An experimentally enriched food supply resulted in low mortality of both the spring and autumn generations. Natality, which is usually stable, increased slightly as a consequence of the additional food supply. This was due to an earlier start of the breeding season (6 weeks earlier) and to an increase in numbers of mature (i.e. capable of reproduction) females.     

Informal Notes on the 4th East African Herbicide Conference at Arusha,Tanzania

Abstract

An IPM schedule using synthetic sex pheromone (Z‐3‐dodecenol‐E‐2‐butenoate) as the principal component against sweet potato weevil has been evaluated for the first time in India. The components of the IPM Programme were: (a) disinfecting the planting materials by dipping the slips in monocrotophos 0.05% for 10 min; (b) installation of pheromone traps from the first day of planting at 10 m distance (one trap/100 m²) to destroy the male weevils; and (c) re‐ridging the crop at 30 and 60 days after planting. The continuous elimination of the male population by pheromone traps in the treatment has resulted in a drastic decline in the population build‐up of the weevil and consequent reduction in the damage, leading to increased production of marketable tubers over 53%. In the first season weevil damage was reduced from 33% to 9.7% and in the second season from 39% to 9.5% by adopting the IPM schedule. The control field showed a four‐ to seven‐fold increase in the pest population (516 to 741 in the control and 114 to 128 in the treatment).     

AquaCrop作物模型在黄土塬区夏玉米生产中的适用性评价

为评价Aqua Crop作物模型在黄土塬区的适用性,基于Hsiao等人推荐的玉米参数对模型参数进行调试及验证。在陕西长武地区模拟2003、2004、2005、2007、2008、2010年玉米生育期内生物量、蒸发蒸腾量的变化过程及收获时产量、地上部生物量,将模拟值与收集到的实测值进行对比、分析。结果表明,这6年模拟产量与实测产量间的校正决定系数(Adj)R2为0.9270,相对误差在-2.479至11.182之间;模拟地上部生物量与实测地上部生物量间的Adj.R2为0.7842,模型对产量的模拟效果优于对生物量的模拟;2005年和2008年模拟蒸散量与实测蒸散量间的Adj.R2分别为0.6229和0.7973。模拟效果较好,对黄土塬区夏玉米水分优化管理模拟有重要意义。     

Dairyland populations of bur cucumber (Sicyos angulatus) as a possible seed source for riverbank populations along the Abukuma River,Japan

In 2006, the distribution of bur cucumber (Sicyos angulatus L.) along the river bank of the Abukuma River, Japan, was examined. Twenty‐six populations were found in the area surrounding the upper reach of the river and they were limited to dairy land. On the basis of polymerase chain reaction–restriction fragment length polymorphism analysis for four of the six polymorphic loci that were detected in 16 non‐coding regions of the chloroplast DNA from 300 samples, five multilocus haplotypes (A–E) were identified. Despite its smaller size, the surrounding area's population showed a higher genetic diversity at the haplotype level than did the riverbank population. The haplotype composition of the surrounding area's population was similar to that of the riverbank population in the upper‐stream region. The distribution of haplotype D was biased towards the upper reach of the river, possibly because of migration from the surrounding area's population. The distribution of haplotype E was biased towards the middle‐to‐lower reaches of the river and was associated with the existence of source populations other than the surrounding area's population. The results also showed that the estimated seed flow from another dairy land could transport seeds into the middle reach of the river at a high frequency, suggesting that dairy land is largely responsible for the development of the riverbank populations. The eradication of dairyland populations should be given priority in order to prevent future migration along the river bank and to protect the existing endangered wetland species from invasive S. angulatus.     

Resistance of Pakistani field populations of spotted bollworm Earias vittella (Lepidoptera: Noctuidae) to pyrethroid,organophosphorus and new chemical insecticides

BACKGROUND: The spotted bollworm Earias vittella (Fab.) is a serious pest of cotton and okra in Pakistan. Owing to persistent use of insecticides, this pest has developed resistance, especially to pyrethroids. The present studies aimed at determining the extent of resistance to pyrethroid, organophosphorus and new chemical insecticides in Pakistani populations of E. vittella. RESULTS: Field populations of E. vittella were monitored at Multan, Pakistan, from 1999 to 2007 for their resistance against six pyrethroid, four organophosphorus and six new chemical insecticides using a leaf‐dip bioassay. Of the pyrethroids, resistance was generally low to zeta‐cypermethrin and moderate to high or very high to cypermethrin, deltamethrin, esfenvalerate, bifenthrin and lambda‐cyhalothrin. Resistance to organophosphates chlorpyrifos, profenofos, triazophos and phoxim was recorded at very low to low levels. Among new chemicals, E. vittella had no or a very low resistance to spinosad, emamectin benzoate and methoxyfenozide, a very low to low resistance to abamectin, a very low to moderate resistance to indoxacarb and a moderate resistance to chlorfenapyr. CONCLUSION: The results indicate a lack of cross‐resistance between pyrethroid and organophosphorus insecticides in E. vittella. Rotation of insecticides showing no, very low or low resistance, but belonging to different insecticide classes with unrelated modes of action, may prevent or mitigate insecticide resistance in E. vittella. Copyright © 2009 Society of Chemical Industry     

Field evaluation of reduced insecticide spray programs for managing plum curculio, Conotrachelus nenuphar (Coleoptera: Curculionidae), in Alabama peaches

BACKGROUND: Plum curculio (PC), Conotrachelus nenuphar (Herbst.), is an important pest of peaches in the southeastern United States. Commercially acceptable control of this insect is typically achieved by weekly or biweekly application of broad‐spectrum conventional insecticides, resulting in 6–12 sprays per season. Experiments were conducted in a peach orchard in Alabama during 2007–2009 to compare the conventional calendar‐based insecticide spray program involving weekly applications of phosmet with three different reduced spray programs using three targeted (well‐timed) insecticide sprays (TIS) of phosmet, permethrin or thiamethoxam applied in an alternated fashion. RESULTS: All three TIS programs significantly reduced PC damage at harvest compared with the untreated control in two of the three years (2008 and 2009). Fruit damage due to stink bugs, which are emerging pests of peaches in the region, was also significantly reduced in the TIS programs in both years. In a separate trial in which one of the TIS programs (three targeted sprays of phosmet) was evaluated in a larger peach block in 2009, percentage fruit damage due to PC increased from < 1% in June to ～4% in late July. CONCLUSION: All the TIS programs evaluated provided effective control of PC and represent potential alternatives to the conventional weekly spray program in peaches with concomitant reduction in insecticide usage and associated costs. However, an additional spray may be necessary for effective control of PC and stink bugs in late‐season peach varieties. Copyright © 2011 Society of Chemical Industry     

Effect of anaerobic soil disinfestation amendment type and C:N ratio on Cyperus esculentus tuber sprouting,growth and reproduction

Anaerobic soil disinfestation (ASD) is a cultural technique primarily targeted for control of soilborne plant pathogens, but can also impact weed propagules. A repeated pot study was conducted to evaluate ASD treatment impact on sprouting and growth of introduced Cyperus esculentus (yellow nutsedge) tubers using dry molasses‐based and wheat bran‐based amendment mixtures at four carbon‐to‐nitrogen (C:N) ratios (from 10:1 to 40:1) and compared with a non‐amended control. The mean percentage of sprouted tubers recovered after ASD treatment was lower for wheat bran‐based (42%) than dry molasses‐based (65%) amendments, and tuber production was 1.6‐fold higher in dry molasses‐based than wheat bran‐based treatments. The highest percentage of sprouted tubers (79%) and the highest mean production of large tubers (threefold higher than wheat bran‐based and 1.7‐fold higher than molasses‐based amendments) were observed for the non‐amended control. Tuber sprouting was significantly lower from all ASD treatments (regardless of amendment C:N ratio) compared with the non‐amended control at a 15 cm burial depth. New tuber production was lowest at C:N ratios of 10:1 and 20:1 and more than twofold higher in the non‐amended control. Wheat bran‐based amendments reduced above‐ground C. esculentus biomass compared with the non‐amended control and ASD treatments with molasses‐based amendments, and reduced below‐ground biomass compared with molasses‐based amendments. Above‐ground biomass was highest at amendment C:N ratio of 10:1, and below‐ground biomass was highest at amendment C:N ratio of 40:1 and the non‐amended control. ASD treatment with wheat bran‐based amendments at lower C:N ratios reduced tuber sprouting and reproduction compared with the non‐amended control, but not at rates high enough to use as a primary weed management tactic.     

Effect of log seasonality on reproductive potential ofMonochamus galloprovincialis reared in scots pine logs under laboratory conditions

Insect reproduction may be affected by a number of factors including seasonal changes in larval or adult nutrition. The effect of season on the reproductive potential ofMonochamus galloprovincialis (Olivier) females reared inPinus sylvestris L. (Scots pine) logs was investigated by constructing fertility tables for each log that differed only in the season they were cut. Population parameters were compared among three seasonal cohorts. The intrinsic rate of increase and most of the associated population parameters of beetles that emerged from logs cut during spring were higher than for beetles emerged from summer and autumn logs. Slight differences were found between summer and autumn cohorts. We suggest that seasonal differences in the nutritional quality of logs caused differences inM. galloprovincialis survival and reproductive potential. http://www.phytoparasitica.org posting March 16, 2008.     

Population genetic structure,gene flow and recombination of Cochliobolus miyabeanus on cultivated wildrice (Zizania palustris)

A collection of 168 Cochliobolus miyabeanus isolates was made from cultivated wildrice (Zizania palustris) paddies in Minnesota, USA, during 2007 and 2008. Analysis of 26 polymorphic amplified fragment length polymorphism (AFLP) markers generated with three primer‐pair combinations indicated a moderate average gene diversity () of 0·283. Genotypic diversity was high in all collection areas with the exception of a paddy in Itasca County. Significant population subdivision by collection site was found with amova tests using both the entire fungal population data (F_ST = 0·29, P < 0·001) and the clone‐corrected data (F_ST = 0·08, P < 0·001), and with a Markov chain Monte Carlo approach. Abundant immigrants, shared haplotypes and admixed genotypes were found in paddies in central‐eastern areas. Although indirect tests did not support the hypothesis of random mating at the subpopulation level, sexual recombination nevertheless may be possible in areas where both mating type idiomorphs, MAT1‐1 and MAT1‐2, were found. These results may have implications in breeding for resistance and disease management.     

Population genetics of Phytophthora infestans in Denmark reveals dominantly clonal populations and specific alleles linked to metalaxyl‐M resistance

Control of the potato late blight pathogen Phytophthora infestans relies heavily on chemicals. The fungicide metalaxyl‐M (Mefenoxam) has played an important role in controlling the disease, but insensitivity to the fungicide in certain isolates is now of major concern. A genetic basis for resistance to metalaxyl suggests the possibility for linking resistance phenotypes to specific population genetic markers, but in order to do this, the population genetic structure and mode of reproduction in a population must first be well described. The dynamics of metalaxyl‐M resistance in the Danish population of P. infestans was characterized over the course of the 2013 growing season, as was the population genetic structure, using simple sequence repeat (SSR) genotypes and single nucleotide polymorphism (SNP)‐based mitochondrial haplotyping of over 80 isolates. Both mating types A1 and A2 were present in most fields, but tests for recombination showed that clonal reproduction dominates in Danish populations. Genotype was not linked to haplotype and no differentiation was observed at the haplotype level, but rather between fields. Resistance phenotypes were linked to specific SSR alleles, demonstrating the potential for a more precise SNP‐based marker system for predicting resistance to metalaxyl‐M.     

Catching Ips duplicatus (Sahlberg) (Coleoptera: Scolytidae) with pheromone‐baited traps: optimal trap type,colour, height and distance to infestation

BACKGROUND: Field trapping experiments were carried out to evaluate effective trap characteristics for maximising Ips duplicatus (Sahlberg) catches in pheromone‐baited traps in China. RESULTS: Window‐slot and cross‐barrier traps had significantly higher catches than multiple‐funnel traps. The colour of window‐slot traps showed a significant effect on catches, with dark colours (black and red) being more effective than light colours, especially white and yellow. Window‐slot traps at a 1.5–2.0 m level caught more beetles than those at either ground level (0–0.5 m) or at 3.5–4.0 m. Ips duplicatus can be attracted to pheromone‐baited traps over a distance of > 100 m from the forest edge in an open grassy field. There was a strong diurnal pattern of flight activity, with catches on window‐slot traps occurring during the daytime with one broad peak at mid‐ to late afternoon. The seasonal flight activity of I. duplicatus as monitored by pheromone‐baited window‐slot traps during 2007–2008 indicated that three major flight peaks occurred in early June, late June–early July and late July respectively, suggesting the existence of a potential second generation. CONCLUSION: The optimal trap characteristics will improve the performance of pheromone‐baited traps as a critical monitoring or mass‐trapping tool to combat outbreaks of this pest species. Copyright © 2009 Society of Chemical Industry     

Cross-resistance patterns and fitness in fufenozide-resistant diamondback moth, Plutella xylostella (Lepidoptera: Plutellidae)

BACKGROUND: Fufenozide is a novel non‐steroidal ecdysone agonist with good efficacy against diamondback moth (DBM), Plutella xylostella (Lepidoptera: Plutellidae). At present, it is widely applied for the control of a range of lepidopterous pests in China. This study compared the activities of fufenozide and 12 other insecticides against unselected and fufenozide‐selected strains of DBM to examine potential patterns of cross‐resistance. The relative fitness of the fufenozide‐selected strain was assessed to provide information pertinent to insecticide resistance management. RESULTS: Compared with the susceptible strain (JSS), the fufenozide‐resistant strain (JSR) showed high cross‐resistance to dibenzoylhydrazines and benzoylphenylureas, low cross‐resistance to abamectin and no cross‐resistance to organophosphates, carbamates and pyrethroids. JSR had a lower reproductive ability and a relative fitness of 0.5 compared with JSS. CONCLUSION: P. xylostella has the potential to develop resistance to fufenozide, albeit at the expense of fitness. Cross‐resistance between the same and other classes of insecticides is of concern, and should be a key consideration when implementing fufenozide‐based control strategies for this species. Copyright © 2011 Society of Chemical Industry     

Characterisation of abamectin resistance in a field‐evolved multiresistant population of Plutella xylostella

BACKGROUND: Plutella xylostella (L.) has evolved resistance to various kinds of insecticide in the field. Reversion and selection, cross‐resistance, inheritance and mechanisms of abamectin resistance were characterised in a field‐derived multiresistant population of P. xylostella from China. RESULTS: Compared with a susceptible Roth strain, the field‐derived TH population showed ～5000‐fold resistance to abamectin. Rapid reversion of abamectin resistance was observed in the TH population when kept without insecticide selection. The TH‐Abm strain, selected from the TH population with abamectin, developed 23 670‐fold resistance to abamectin, a high level of cross‐resistance to emamectin benzoate and low levels of cross‐resistance to spinosad and fipronil. Genetic analyses indicated that abamectin resistance in the TH‐Abm strain was autosomal, incompletely dominant and polygenic. P450 monooxygenase activities in the TH‐Abm strain were significantly elevated compared with the TH strain. Piperonyl butoxide (PBO) inhibited a small part of abamectin resistance in the TH‐Abm strain. CONCLUSION: Field‐evolved high‐level resistance to abamectin in the TH population was not stable. Selection of the TH population with abamectin resulted in an extremely high level of cross‐resistance to emamectin benzoate and low levels of cross‐resistance to spinosad and fipronil. Enhanced oxidative metabolism was involved in, but may not be the major mechanism of, polygenic abamectin resistance in the TH‐Abm strain. Copyright © 2009 Society of Chemical Industry     

Insecticide resistance of the oriental fruit fly, Bactrocera dorsalis (Hendel) (Diptera: Tephritidae), in mainland China

BACKGROUND: In order to investigate the extent of resistance of oriental fruit fly, Bactrocera dorsalis (Hendel), which is a widespread pest throughout tropical, subtropical and temperate fruit crops, 25 populations of this insect were collected from 13 sites in mainland China in 2007 and 2008. In addition, resistant strains were established that showed increasing development of resistance. RESULTS: Compared with the susceptible strain, one population of B. dorsalis expressed high resistance (RR = 70.4‐fold), 16 populations expressed medium resistance (11.5‐fold < RR < 25.8‐fold) and eight populations had low resistance or remained susceptible (1.4‐fold < RR < 8.9‐fold) to trichlorphon. As regards β‐cypermethrin, one population showed high resistance (RR = 44.0‐fold), nine populations expressed medium resistance (12.2‐fold < RR < 28.4‐fold), 14 populations expressed low or minor resistance (3.0‐fold < RR < 9.7‐fold) and one population remained susceptible (RR = 1.1‐fold). As regards avermectin, five populations had developed high resistance (44.3‐fold < RR < 104‐fold), seven populations expressed medium resistance (11.4‐fold < RR < 38.6‐fold) and three populations expressed low or minor resistance (3.5‐fold < RR < 5.6‐fold). A continuous resistance selection in the laboratory strain showed that the resistance ratios to trichlorphon, β‐cypermethrin and avermectin were 71.6‐fold, 333‐fold and 70.4‐fold respectively. CONCLUSION: The data provided a comprehensive survey of insecticide resistance in Bactrocera dorsalis in mainland China. All results suggested that early resistance management programmes should be established for restoring the efficacy of pesticide‐based control measures. Copyright © 2010 Society of Chemical Industry