Comparative efficacy of indigenous heterorhabditid nematodes from north western Himalaya and Heterorhabditis indica (Poinar,Karunakar & David) against the larvae of Helicoverpa armigera (Hubner)

The efficacy of three Heterorhabditis spp of entomopathogenic nematodes (EPNs) from north western Himalaya, India was studied against the larvae of pod borer, Helicoverpa armigera (Hubner) (Lepidoptera: Noctuidae), under the laboratory conditions. The larvae were exposed to 10, 20, 30 and 40 infective juveniles (IJs) of each nematode species for different time periods and they were found to be susceptible to all the EPNs tested. However, the susceptibility of larvae to nematode infection varied according to the concentrations of IJs and their exposure periods. The efficacy of these indigenous entomopathogenic nematodes was also compared against commercially available entomopathogenic nematode, H. indica. Appreciably good performance was achieved by H. bacteriophora (HRJ), which showed 73.3% mortality of insect larvae in 96 h exposure time against third instar larvae, while H. indica produced 80.0% mortality. However it was noticed that with the advancement of larval stage its mortality rate reduced and vice versa with the exposure period. All tested EPNs were also found to reproduce within the host and maximum production of IJs was recorded in H. bacteriophora (26.0 ± 3.76 × 10³ IJs/larva) at the concentration of 40 IJs/larva.     

两种昆虫病原线虫防治核桃云斑天牛田间效果评价

云斑天牛Batocera lineolata Chevrolat是核桃树的严重蛀干害虫,隐蔽性强,化学、物理防治方法难以奏效,昆虫病原线虫可以主动寻找寄主并在蛀道内建立种群,省工长效。本研究评价了不同剂量（250、500、1000、2000和4000 IJs/mL）的2种昆虫病原线虫（小卷蛾斯氏线虫Steinernema carpocapsae和嗜菌异小杆线虫Heterorhabditis bacteriophora）对核桃云斑天牛卵和幼虫的防治效果。结果表明,2种线虫对天牛卵和幼虫的最终防控效果随施用剂量增大而增强。施用剂量为4000 IJs/mL的小卷蛾斯氏线虫和嗜菌异小杆线虫对该天牛卵的校正防治效率分别达65.0%和39.5%,对幼虫的最终校正防治效率分别达93.8%和82.4%;2种线虫在2000 IJs/mL剂量下对天牛卵的校正防治效率分别达48.8%和32.3%,对幼虫的校正防治效率分别达85.9%和83.4%。从而说明,适宜剂量的昆虫病原线虫对云斑天牛幼虫的田间防控效果好于对卵的效果,可以作为云斑天牛的有效防治技术。     

Genetic improvement of the desiccation tolerance and host-seeking ability of the entomopathogenic nematode <Emphasis Type="Italic">Steinernema feltiae</Emphasis>

Entomopathogenic nematodes (EPNs) from the genus Steinernema (Steinernematidae) are used for biological control of insect pests. The infective stages of these nematodes are intolerant of extreme environmental conditions. Genetic improvement has been suggested as an approach for improving their ability to overcome these limitations. In this study, we bred a heterogeneous population of the EPN Steinernema feltiae Filipjev for desiccation tolerance (both rapid and slow) and enhanced host-seeking ability. We selected for tolerance of rapid desiccation by exposing infective juveniles (IJs) to ambient conditions (22–25°C; 50–65% r.h.) for 100 min. A survival rate of 80–90% was reached after ten selection cycles. To select for tolerance of slow desiccation, we exposed IJs to 97% r.h. for 72 h, followed by further exposure to 85% r.h. for an additional 72 h. A high survival rate (>85%) was obtained after 20 selection cycles. We selected for enhanced downward dispersal by forcing IJs to move through a sand column to reach larvae of last-instar Galleria mellonella placed at the bottom of the column. After 25 selection cycles, the majority (>75%) of these nematodes were found at the layer close to the insects. No reduction in fitness was detected in the selected populations. Nevertheless, the nematode population selected for enhanced downward dispersal displayed significantly higher infectivity than the foundation population. The population selected for slow desiccation was more tolerant of heat stress than the foundation population. These findings establish the basis for improvement of this nematode for use as a biological control agent under field conditions.     

Screening for environmental stress-tolerant entomopathogenic nematodes virulent against cotton bollworms

A total of 27 entomopathogenic nematode (EPN) strains originally isolated from different cotton fields were characterized in laboratory experiments for their virulence, reproductive potential and environmental tolerance. The EPN strain collections included 16 Steinernema carpocapsae (SC), three Steinernema siamkayai (SS), one Steinernema monticolum (SM), and seven Heterorhabditis bacteriophora (HB). Their virulence was tested against cotton bollworms such as the American bollworm Helicoverpa armigera, the spotted bollworm Earias vittella and the cotton leafworm Spodoptera litura. Larvae of H. armigera, E. vittella and S. litura were susceptible to all the tested EPN species/strains with significant differences among EPN species/strains. The most virulent strains were APKS2 (SC), TRYH1 (HB) KKMH1 (HB) and KKMH2 (HB) on H. armigera (91.9–93.5% mortality); KKMS1 (SC), APKS2 (SC), TRYH1 (HB), KKMH1 (HB), KKMH2 (HB) and APKH1 (HB) on E. vittella (92.7% mortality); and APKS2, TRYH1, KKMH1, KKMH2 and KKMH3 on S. litura (92.7% mortality). The results of the invasion rate assay indicated that the EPN strains more virulent against the target host had greater invasion rates. In the multiplication assay, KKMH1and OCMS1 (SC) produced a greater number of infective juveniles (IJs) (32.1–32.4 x 1000 IJs/ cadaver) in Carcyra cephalonica. Test for tolerance to heat at 40°C for 2 h revealed that KKMH1, TRYH1, KKMH2, KKMS1 and APKS2 were highly tolerant (>85% survival). IJs exposed to ambient room conditions (27–29°C; 65–70% r.h.) for 2 h showed that APKS2, OCMS1 and KKMS1 were more tolerant (68–69% survival) of rapid desiccation than others. APKS2, KKMS1 and KKMH1 showed better survival (70–73%) in slow desiccation assay when exposed to 25°C with 97% r.h. for 72 h, followed by 25°C with 93% r.h. for 48 h. The H. bacteriophora KKMH1 and S. carpocapsae APKS2 performed best in nine traits out of ten tested, followed by H. bacteriophora TRYH1, which performed best for six traits. It is suggested that the EPN strains KKMH1 and APKS2 could be deployed for a cotton bollworm management program after testing their performance under field conditions.     

海南槟榔园昆虫病原线虫对红脉穗螟的致病力

红脉穗螟Tirathaba rufivena Walker是槟榔上的重要害虫。本研究采用大蜡螟诱捕法,对海南省主要槟榔产区槟榔园中采集到的土样进行昆虫病原线虫的诱捕,并评估了目标线虫对红脉穗螟的致病力。在采集的150份土样中共有12个土样经检测发现含有昆虫病原线虫,检出率为8%。其中,屯昌、定安和万宁三个市县采集的土样中检出的带线虫比率相对较高,分别为12.90%、11.76%和10.00%,而海口和保亭土样中未检出昆虫病原线虫。在室内以大蜡螟为试虫测试线虫的致病力,结果表明诱捕的12个线虫种群均对大蜡螟幼虫具有一定的致病力,但致病力的大小存在较大差异（120 h校正死亡率21.11%～72.22%）。选取致病力较高的Tc05、Wn01和Wn09样本测试对红脉穗螟3龄幼虫的致病作用,结果显示在600 IJs/mL线虫液处理后24 h,Wn01种群对寄主的校正死亡率达到86.67%,半致死浓度LC₅₀为283.70 IJs/mL;Tc05和Wn09对红脉穗螟的致病力相近,校正死亡率分别为61.67%和65.00%,LC₅₀分别为504.75 IJs/mL和502.70 IJs/mL。研究表明,Wn01,Tc05和Wn09线虫种群对红脉穗螟幼虫具有一定的控制潜力。     

Entomopathogenic nematodes for the management of Agrotis ipsilon: effect of instar, nematode species and nematode production method

BACKGROUND: Previous laboratory studies have indicated the potential of some entomopathogenic nematode (EPN) species for the control of larvae of the black cutworm (BCW). To determine the most promising EPN species and the most susceptible BCW stages, a more in‐depth evaluation of seven EPN species against different BCW instars was carried out, the efficacies of in vitro‐ and in vivo‐produced EPNs were compared and the suitability of BCW instars for EPN reproduction was examined. RESULTS: Heterorhabditis megidis was the most virulent species, irrespective of larval stage in small arenas, followed most often by H. bacteriophora. In pots with grass, Steinernema carpocapsae tended to be the most virulent species, followed by H. bacteriophora, H. megidis and S. riobrave. Fourth and/or fifth instars were the most susceptible stages to most EPN species, and pupae the least susceptible. Furthermore, H. bacteriophora, H. megidis and S. carpocapsae successfully reproduced in fifth and sixth instars and pupae. In vivo‐produced H. megidis and S. carpocapsae controlled fifth instars better than the corresponding in vitro‐produced products; production method did not affect H. bacteriophora and S. riobrave efficacy. CONCLUSIONS: Several in vitro‐produced commercial EPN strains were highly virulent to BCW and warrant further testing under field conditions, along with some in vivo‐produced strains. Copyright © 2011 Society of Chemical Industry     

Desiccation survival of entomopathogenic nematodes of the genusHeterorhabditis

The present study aims at determining the desiccation tolerance of entomopathogenic nematodes from the genusHeterorhabditis recently isolated in Israel. We first verified the most suitable desiccation conditions that lead to induction of the anhydrobiotic state usingHeterorhabditis bacteriophora HP88. After direct exposure of infective juveniles (IJs) to 97% and 93% r.h. for 96 h, the survival rate was > 70%. By contrast, exposing HP88 IJs to 88% and 85% r.h. resulted in poor survival (< 10%) or complete mortality. Following exposure to 97% and 93% r.h. for 24, 48, 72 or 96 h, survival ranged from 68% to 79% with no significant differences between the exposure periods. Stepwise reduction of r.h. conditions (97% > 93% > 88% > 85% r.h.) at a 24-h or 72-h interval resulted in enhanced survival (30% survival) of IJs at the final r.h. level compared with IJs which were either directly exposed to 85% r.h. (0% survival) or were preconditioned at the higher r.h. levels prior to exposure to 85% r.h. (15% survival).H. bacteriophora HP88 IJs were able to survive for at least 18 days after preconditioning. At 97% r.h. nematode viability remained stable at 70–85% and at 93% r.h. survival ranged between 37% and 60%. The data indicate that survival is influenced by rate of water removal from the nematode’s body and a minimal relative humidity level (>93%). Substantial differences in survival ability were observed among IJs of 12 new heterorhabditid populations, isolated from different climatic regions in Israel, which were preconditioned at 97% r.h. for 72 h following by an additional 72 h at 93% r.h. Maximum survival was recorded with HIS-19 (64%), moderate (40–55%) survival was observed with seven isolates, includingH. bacteriophora HP88, and five isolates displayed poor (<25%) desiccation tolerance. Contribution from the Agricultural Research Organization, Bet Dagan, Israel, No. 502-99, 1999 series.     

Phoretic dispersal of the entomopathogenic nematode Heterorhabditis amazonensis by the beetle Calosoma granulatum

Entomopathogenic nematodes (EPN) have limited ability to travel and need to adopt alternative strategies to reach hosts that are far away. They can attach themselves to an organism that acts only as a dispersal agent to transport the EPN to places that they cannot reach by themselves. The larval and adult stages of Calosoma granulatum (Coleoptera: Carabidae) beetle are important predators of caterpillars that live in the soil of Brazilian agricultural systems. The nematode Heterorhabditis amazonensis (Rhabditida: Heterorhabditidae) is a native of Brazil and plays a major role in the control of Spodoptera frugiperda (Lepidoptera: Noctuidae) caterpillars. This study assessed the ability of C. granulatum to carry and disperse H. amazonensis. The experimental arenas consisted of two types of containers with substrate connected by a plastic tube through which the insects could move freely. Only one of the containers received infective juveniles (IJ) and the other was used as the test container. We first used C. granulatum larvae and adults to evaluate the influence of different concentrations of IJs on phoretic behavior. Then different distances traveled by the adult beetle were tested to measure their effect on IJ transport. The results showed that C. granulatum is a good phoretic dispersal agent and the transport of IJs by the larvae is less influenced than transport by the adult, by a change in the IJ concentration. The distance traveled by the adult influences the number of EPN carried and the detection of phoresy even at greater distances (40 cm) indicates that C. granulatum is capable of transporting the EPN for distances greater than those evaluated.     

Effect of rapid and gradual increase of osmotic stress on survival of entomopathogenic nematodes

The effect of rapid and gradual exposure of entomopathogenic nematodes to osmotic stresses on the induction of a dormant state was determined with the nematodeSteinernema feltiae IS-6 infective juveniles (IJs). Rapid exposure of nematodes to glycerol at concentrations of 24% and 28% (w/w) caused the nematodes to enter a dormant state which was characterized by shrinking and impeded motility of all nematodes within 8 h. However, pre-exposure to gradually increasing glycerol concentrations of 5%, 10% and 18% at 4-h intervals resulted in dormancy after 4 h exposure to 24% glycerol. The total time of exposure to glycerol solution was 16 h in gradual osmotic stress. For nematodes exposed to 24% glycerol solution either rapidly or gradually, recovery occurred after 40 min in distilled water. Infectivity of osmotically stressedS. feltiae IJs was evaluated by two criteria, insect mortality and invasion rate. The assays indicated that infectivity of nematodes desiccated by rapid and gradual osmotic stresses was similar to that of fresh nematodes. Rapid exposure ofS. carpocapsae ‘All’,S. riobravis ‘Texas’,S. glaseri ‘NI’ andHeterorhabditis bacteriophora HP88 IJs to the 24% glycerol solution resulted in dormancy within 8 h. These treatments caused mortality of 48.4% and 11.7% amongS. glaseri Nl andH. bacteriophora HP88 IJs, respectively. Similar effects were observed when these nematode species were exposed to increasing osmotic stress of 5%, 10% and 18% at 6-h intervals. Under these same conditions, mortality ofH. bacteriophora HP88 andS. glaseri Nl IJs was 27.5% and 61.8%, respectively. http://www.phytoparasitica.org posting Sept. 29, 2004.     

Effect of spray volume on the deposition, viability and infectivity of entomopathogenic nematodes in a foliar spray on vegetables

BACKGROUND: Spray volume can influence the amount of free water on the leaf surface and subsequently the ability of entomopathogenic nematodes (EPNs) to move. In this study, an investigation was made of the effect of spray volume (548, 730 and 1095 L ha⁻¹) on the deposition, viability and infectivity of EPNs against Galleria mellonella on savoy cabbage, cauliflower and leek. RESULTS: Increasing spray volume decreased nematode deposition on 7.1 cm² leek leaf discs at a 15° angle with the spray nozzle. Although the number of living nematodes observed on leek after 240 min of exposure was not significantly different between the low-volume application (548 L ha⁻¹) and the high-volume application (1095 L ha⁻¹), a greater infectivity was obtained in the latter application. The higher number of droplets deposited on the leek discs in the high-volume application may have stimulated nematode movement. No significant effect of spray volume was observed on the relative deposition of Steinernema carpocapsae on the bottom side of cauliflower and savoy cabbage leaf discs. In spite of the low S. carpocapsae deposition on the bottom side of the savoy cabbage discs, high infectivity was obtained against G. mellonella. Using the lowest spray volume on savoy cabbage, infectivity decreased with increasing exposure time, while infectivity was not affected by exposure time when a spray volume of 730 L ha⁻¹ or more was used. CONCLUSION: Spray volume is an important application parameter, as it affects nematode infectivity. Future research should investigate the effect of spray volume in the field and its influence on the effect of adjuvants. Copyright © 2012 Society of Chemical Industry     

昆虫病原线虫生物防控草地贪夜蛾的室内及田间效果和影响因素

联合国粮食及农业组织2018年向全球发布草地贪夜蛾Spodoptera frugiperda是重要的预警害虫。据报道,2019年我国已有26个省（区、市）的作物受到草地贪夜蛾为害。目前已经发现草地贪夜蛾幼虫对某些化学农药产生抗性的现象,为缓解其抗药性产生,具有主动寻找寄主害虫的昆虫病原线虫为草地贪夜蛾的生物防治提供了应用潜能。该文从昆虫病原线虫高效侵染种（品系）及其浓度、共生菌、草地贪夜蛾幼虫易感龄期、田间致死力及影响防控效果的因素等方面进行综述,以期为田间有效利用昆虫病原线虫防治草地贪夜蛾提供参考。     

昆虫病原线虫对小地老虎的致病力测定及防治效果

为探讨应用昆虫病原线虫防治小地老虎技术的可行性,采用培养皿滤纸法比较9个品系的昆虫病原线虫对小地老虎幼虫的致病力,同时通过盆栽试验验证了斯氏线虫属小卷蛾斯氏线虫Steinernema carpocapsae NC116品系、芫菁夜蛾斯氏线虫S.feltiae SF-SN品系和异小杆线虫属嗜菌异小杆线虫Heterorhabditis bacteriphora H06品系的保苗效果和防治效果,并测定了苦参碱与NC116品系混用对小地老虎3龄幼虫的联合作用效果。结果表明,NC116品系对小地老虎3龄幼虫致病力最高,其对3龄、4龄和5龄的LD50分别为2.4、7.5、和31.2条/头,表明随小地老虎幼虫龄期递增,其致病力下降。盆栽玉米苗上分别施用线虫100~200条/头时,对玉米保苗效果及对小地老虎3龄幼虫的控制效果依次为NC116H06SF-SN。0.8 mg/L苦参碱和NC116品系混用后,可使小地老虎3龄幼虫死亡率提高109.89%,二者表现增效作用。     

昆虫病原线虫致病机制研究进展

昆虫病原线虫与体内细菌共生,专性寄生在昆虫体内,在害虫生物防治中发挥着重要作用。昆虫病原线虫致病性研究是其高效应用的基础,涉及线虫及其共生细菌对昆虫的交互作用。本文针对斯氏属和异小杆属线虫的致病因子及这类线虫与寄主昆虫互作机制进行了综述,为昆虫病原线虫的致病机制研究和应用提供参考。     

Laboratory and field investigations using indigenous entomopathogenic nematodes for biological control of Plutella xylostella in Kenya

This study was undertaken to determine the potential utility of entomopathogenic nematodes for management of diamondback moth (DBM) larvae in Kenya. Five Kenyan EPN isolates, Heterorhabditis indica, Steinernema karii, Steinernema weiseri, Steinernema sp. and Heterorhabditis taysearae were tested for their ability to penetrate DBM and their speed of kill (LT₅₀). Heterorhabditis indica and S. weiseri were found to have the quickest rate of kill and S. weiseri was found to have the largest proportion of nematodes penetrating. Three of the isolates, Steinernema sp. (95), S. weiseri and H. indica, were used in a field experiment to test their ability to reduce DBM populations and damage to kale. All three nematodes caused significant reductions in populations of DBM and DBM damage, with the population reductions being similar to those caused by application of Bacillus thuringiensis ssp. kurstaki. This study shows that EPNs have great potential that should be exploited in the management of DBM in Kenya.     

昆虫病原线虫对甘薯蚁象的致病力测定

昆虫病原线虫是隐蔽性害虫的有效生物防治因子,对8种斯氏线虫和3种异小杆线虫进行筛选证实夜蛾斯氏线虫Steinernema feltiae对甘薯蚁象Cylas formicarius的致病力最强;在此基础上进一步研究了11个不同地理来源的S.feltiae品系对甘薯蚁象末龄幼虫的致病力,获得强致病力的品系S.feltiae JY-17并测定了不同因素对该线虫品系致病力的影响。研究结果表明：在25℃条件下,甘薯蚁象不同发育阶段对S.feltiae JY-17的敏感性依次为末龄幼虫〉低龄幼虫〉蛹〉预蛹期〉成虫;在不同测试温度条件下,sfeltiae JY-17致病力由高到低顺序为25℃〉20℃〉30℃〉15℃〉10℃〉35℃;在25℃条件下,当寄主密度为196．6头·m^-2时,线虫对蚁象末龄幼虫的LD50=5．532条·头^-1,LD90=28．049条·头^-1;当线虫与寄主比例为5：1时,LT50=44．306h。本研究为利用昆虫病原线虫防治甘薯蚁象提供了理论依据。     

Response of Arabidopsis thaliana to 22 ALS inhibitors: baseline toxicity and cross-resistance of csr1-1 and csr1-2 resistant mutants

The baseline toxicity of 22 acetolactate synthase (ALS)-inhibiting herbicides and the cross-resistance patterns of chlorsulfuron- and imazapyr-resistant (R) lines on these 22 ALS-inhibiting herbicides were investigated using the model species Arabidopsis thaliana. The 22 herbicides consisted of 18 sulfonylureas (SU), three imidazolinones (IMI) and one triazolopyrimidine (TP). The ED₅₀ values (doses of herbicides required to reduce dry matter by 50%) of the post-emergence-treated Col and Ler susceptible (S) lines ranged from 22 to 4822 mg ha⁻¹ and from 17 to 3143 mg ha⁻¹ respectively. The csr1-1 chlorsulfuron-resistant line (substitution of Pro₁₉₇ to Ser) conferred a high resistance to the only TP tested as well as to nine SU herbicides (R:S ratio ≥30), a low resistance to two SU herbicides (R:S≥5 and <30) and little or no resistance to the three IMI and seven other SU herbicides (R:S <5). This result contradicts the expectation that an ALS mutation selected by an SU herbicide confers high cross-resistance to other SU herbicides. We found that the efficacy of specific ALS inhibitors was different for different species and therefore could not be predicted from our results with A. thaliana; however, the cross-resistance patterns in A. thaliana were highly correlated with cross-resistance patterns in unrelated species with the same resistance mutation. These results have implications for resistance management.     

Temperature requirements for after-ripening in buried seeds of four summer annual weeds

Freshly matured, seeds of the four summer annuals Ambrosia artemisiifolia, Polygonum pensylvanicum, Amaranthus hybridus and Chenopodium album were buried in soil at (12/12 h) daily thermoperiods of 15/6, 20/10, 25/15, 30/15 and 35/20°C and at a constant temperature of 5°C. After 0, 1, 3 and 5 months, seeds of each species at each temperature were exhumed and tested at a 14-h daily photoperiod at all six temperatures. Fresh seeds of A. artemisiifolia and P. pensylvanicum did not germinate at any temperature, those of A, hybridus germinated to 4 and 64% at 30/15 and 35/20°C, respectively, and those of C. album to 11–20% at 25/15, 30/15 and 35/20°C. Seeds of A. artemisiifolia and P. pensylvanicum, which germinate only in spring, required exposure to low (5, 15/6°C) temperature to after-ripen completely (i.e., to gain the ability to germinate over a wide range of temperatures), and little or no after-ripening occurred at high (25/15, 30/15 and 35/20°C) temperatures. Seeds of A. hybridus and C. album, which germinate in spring and summer, required exposure to low temperature to after-ripen completely, but at high temperatures they rapidly gained the ability to germinate at high temperatures. Regardless of the burial temperatures and species, when after-ripening occurred, seeds firs germinated at high and then at low temperatures. The minimum germination temperature for a species decreased with after-ripening temperature and with an increase in the length of the burial period.     

不同品系昆虫病原线虫抗逆性分析

昆虫病原线虫作为一种高效的生物防治因子,具有广泛的应用前景.但昆虫病原线虫的生物活性受自然环境影响较大,筛选抗逆优良品系对于更好地推广和应用昆虫病原线虫具有十分重要的意义.为了评价昆虫病原线虫的抗逆性差异及生防潜力,在室内条件下测试了17个采自不同地区的昆虫病原线虫品系对高温、低温及干燥环境的抗性.结果显示:Stein...     

Comparative biology and life table of Habrobracon hebetor (Hymenoptera: Braconidae) on Anagasta kuehniella (Lepidoptera: Pyralidae) at five constant temperatures

Habrobracon hebetor Say is an ectoparasitoid that has been used as a control agent of various lepidopteran pests. Temperature-dependent life table and thermal characteristics of H. hebetor are important in understanding the dynamics of host–parasitoid relationships and for optimizing biocontrol programmes. The influence of five constant temperatures (15, 20, 25, 30 and 35 °C) on the biology of H. hebetor when parasitizing Anagasta kuehniella Zeller was studied. The survival rate of immature stages increased from 16.67% to 83.81% as temperature increased from 15 to 30 °C and then decreased at 35 °C. Total development time ranged from 45.70 days at 15 °C to 7.10 days at 35 °C. The lower temperature threshold for immature stages varied slightly around a value of 11–12 °C. The net reproductive rate (R₀) values were significantly different among temperatures and the highest value was found at 30 °C (85.10). The high survival rate and net reproductive rate combined with a relatively short generation time at 30 °C resulted in the intrinsic rate of increase (r_m) being highest (0.312 d^?1) at this temperature. Considering the acquired results, the temperature range between 25 and 30 °C was optimal for H. hebetor.     

Control of Avena fatua and Fagopyrum tataricum with tank mixtures of linuron or linuron + MCPA and sequential applications of linuron, and post-emergence A. fatua herbicides

Linuron (0.21 and 0.28 kg/ha) and linuron + MCPA (0.21+0.56 kg/ha) in a tank mixture with field rates of barban, difenzoquat and flamprop-methyl reduced the phytotoxicity of these herbicides to Avena fatua. When linuron was applied immediately following or 6 days after the A. fatua herbicides no reduction in phytotoxicity to A. fatua occurred, suggesting that the antagonism may be occurring as a result of physical or chemical incompatability when the herbicides are mixed together. The possibility of obtaining broad-spectrum weed control with one trip over the field by applying linuron and one of these wild oat herbicides separately but at the same time using a double-boom, double-tank system deserves evaluation. When linuron was applied in a tank mixture (0.21 and 0.28 kg/ha), immediately after, or 6 days after diclofop-methyl (0.70 kg/ha), there was no reduction of A. fatua control, and wheat tolerance to the tank mixture was good. This tank mixture offers potential for control under field conditions of A. fatua and some broad-leaved weeds in one spray operation. Linuron + MCPA (0.21+0.56 kg/ha) in a tank mixture severely reduced A. fatua control with diclofop-methyl. No loss of phytotoxicity to Fagopyrum tataricum occurred when the A. fatua herbicides tested were tank mixed with linuron or linuron + MCPA. Lutte contre Avena fatua et Fagopyrum tataricum avec des mélanges extemporanés de linuron ou de linuron + MCPA et des applications successives de linuron et d'herbicides de postlevée actifs contre A. fatua