Chemical Control of Phalaris minor and Avena ludoviciana in Wheat

Abstract

In field experiments conducted at the Punjab Agricultural University, Ludhiana during 1973–74 and 1974–75, pre-emergence application (one day after sowing) of methabenzthiazuron (1.05 kg a.i./ha), metoxuron (1.6 kg a.i./ha) and chlortoluron (0.75 kg a.i./ha) gave effective control of Phalaris minor and Avena ludoviciana in wheat without any phytotoxic effect on the crop. Methabenzthiazuron, metoxuron and chlortoluron gave 1410, 1420 and 1090 kg/ha, respectively, more grain than the unweeded crop and 590, 600 and 270 kg/ha more than the crop hand-weeded twice. Nitrofen (1.25 kg a.i./ha) applied pre-emergence was effective against P. minor only and gave substantial increase in grain yield. Terbutryne, dichlormate and linuron, while effective against P. minor, also had a phytotoxic effect on the crop.     

Use of pyrethroid analogues to identify key structural features for enhanced esterase resistance in Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae)

It has been reported previously that the major resistance mechanism to pyrethroid insecticides by the cotton bollworm Helicoverpa armigera (Hübner) in Australia is a consequence of overproduction of esterase isoenzymes. This paper reports structure-activity relationships that support such a view, based on in vivo bioassays conducted with a range of pyrethroid structures containing a variety of acid and alcohol moieties and the correlation with in vitro esterase inhibition assays against the same structures, and identifies the critical regions of the molecule with regard to esterase inhibition, and hence resistance. The implications of this work in terms of possible resistance management are evaluated and discussed.     

Seasonal Dynamics of Metabolic Mechanisms Mediating Pyrethroid Resistance in Helicoverpa armigera in Central India

Very high cypermethrin and fenvalerate resistance frequencies were recorded in Helicoverpa armigera (Hübner) populations in central India during the 1993–94, 1994–95 and 1995–96 cropping seasons. Synergism assays and biochemical analyses of detoxification enzyme levels indicated that mono-oxygenases and esterases were important metabolic mechanisms mediating pyrethroid resistance. Piperonyl butoxide- (PBO) and profenofos-suppressible pyrethroid resistance were correlated with enhanced levels of cytochrome P450 and general esterases respectively. Enzyme assay data indicated that high cytochrome P450 levels generally coincided with low esterase activity and vice versa. Similarly, synergist bioassays showed that PBO-insensitive resistance was frequently associated with profenofos-sensitive resistance and vice versa. Oxidase- and esterase-mediated mechanisms evidently alternated in a reciprocal manner, with perceptible shifts in relative importance occurring during mid-October in all three seasons and in late January in 1995. Apart from metabolic mechanisms, a synergist-insensitive resistance mechanism (believed to be nerve insensitivity), accounted for an average of 51, 30 and 28% of cypermethrin resistance during the 1993–94, 1994–95 and 1995–96 seasons respectively. © 1997 SCI.     

转Bt基因棉种植前后3个棉铃虫种群对4种杀虫剂的抗性变化

分别于1990年、1992年、2001年和2005年从山东泰安、山东夏津和湖北天门采集3个棉铃虫H elicoverpa arm igera种群,采用点滴法测定了4种杀虫剂对其的毒力,以监测各种群的抗药性变化趋势。结果表明:19901992年3个种群棉铃虫对氰戊菊酯的抗性增长迅速(13.256.1倍);19922001年抗性增长速度有所减缓(3.111.0倍);20012005年抗性水平降低。3个种群棉铃虫对灭多威和辛硫磷的抗性变化趋势与氰戊菊酯的基本相似,但抗性水平较低;对硫丹则均一直处于敏感水平。引起抗药性变化的原因主要与各类药剂的使用频率和转B t基因抗虫棉的大面积推广有关。     

对孤雌生殖产两性子代的暗黑赤眼蜂的研究

试验证阴暗黑赤眼蜂孤雌生殖能产雌雄两性子代。雌蜂占90％以上,与两性生殖没有区别。在山西运城该蜂寄生棉铃虫及黄地老虎卵,人工接种时也能寄生杨雪毒蛾和多种夜蛾科害虫卵,但不能在柞蚕、蓖麻蚕卵内寄生。用杨雪毒蛾卵作寄主繁殖该蜂,方法简便,效果良好。在棉田小区中分别释放暗黑赤眼蜂和松毛虫赤眼蜂防治棉铃虫,寄生率分别为63.7％和47.9％。由于该蜂雌性比特高,对棉铃虫的防治效果较好,值得进一步研究。     

Changes in susceptibility to conventional insecticides of a Cry1Ac-selected population of Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae)

The changes in the susceptibility of the cotton bollworm, Helicoverpa armigera (Hübner) to three insecticides (lambda-cyhalothrin, phoxim and endosulfan) commonly used for control of this pest in China were monitored by bioassays at various generations. The insects were originally collected from Bt cotton fields and selected with Cry1Ac over 44 generations. In comparison with a susceptible strain, the larval resistance of the Bt-selected populations to Cry1Ac toxin increased 106-fold. Simultaneously, the resistance levels to lambda-cyhalothrin, phoxim and endosulfan declined dramatically. The results indicated no positive cross-resistance between Cry1Ac toxin and the insecticides. Evidence of the lack of cross-resistance to three commonly used synthetic insecticides in our laboratory-derived Cry1Ac-resistant population may suggest that growers can confidently use these insecticides if and when resistance to Cry1Ac cotton does occur.     

Nerve Insensitivity to cis-Cypermethrin is Expressed in Adult Heliothis virescens

Adult and third-instar larval Heliothis virescens were examined for nerve insensitivity to cis-cypermethrin using a rapid and robust neurophysiological method. Three laboratory strains, BRC susceptible, PEG-87 resistant and MS2 metabolic resistant, were compared with a series of pyrethroid-resistant strains collected from a field site in Louisiana, USA, during the 1992 cotton season. Nerve insensitivity was present in a proportion of the individuals in both the PEG-87 and the field strains, at both life stages, minimal in the MS2 strain and absent in the BRC strain. Frequencies of nerve-sensitive and nerve-insensitive individuals in each strain were not significantly different at the two life stages examined.     

增效剂的增效作用与棉铃虫抗药性水平之间的关系研究

以不同抗药性水平的棉铃虫三龄幼虫试虫,分别测定增效磷（ＳＶ１）,八氯二丙醚（Ｓ２）月桂氮Ｚｕｏ酮（ＤＣ）,ＩＳ－９６１对久效磷（ｍｏｎｏｃｒｏｔｏｐｈｏｓ）灭多威（ｍｅｔｈｏｍｙｌ）,氰戊菊酯（ｆｅｎｖａｌｅｒａｔｅ）的增效作用,结果表明：４种增效剂的增效作用,除与被测定药剂种类有关外,还与棉铃虫抗药性水平密切相关,其增效作用一般随抗性水平的提高而增加,但增加的幅度低于抗药性提高的幅度。     

Possible Methods for Controlling Ischaemum afrum (J. F. Gamel) Dandy,in Fallow

Abstract

Different mechanical cultivations and herbicide treatments were compared for controlling Ischaemum afrum in a heavily infested fallow area. Of the mechanical cultivations, disc ploughing to a depth of more than 15 cm, following removal of tufts and watering, was found very effective (83% reduction). Incorporated pre-emergence triluralin (1.90 kg a.i./ha) alone or in tank mixtures with oxadiazon (0.95 + 0.95 kg a.i./ha) was also found promising (79 and 76% reduction respectively). Three applications of dalapon (8.09 kg a.i./ha), as post-emergence, at two weekly intervals or two applications followed by another application at 4.05 kg a.i./ha gave almost complete eradication of Ischaemum afrum seedlings for about 12 weeks (99% reduction).     

Response of transplanted rice to nitrogen fertilization under different weed management practices

Abstract

Rice yield increased significantly and consistently up to 120 kg N/ha when weeds were not controlled. But when weeds were effectively controlled by two hand weedings (20 and 40 days after transplanting) or by use of thiobencarb at 1–0 kg a.i./ha rice yield increased significantly up to 80 kg N/ha. The optimum dose of N for transplanted rice under mid‐hill conditions of Himachal Pradesh (Palampur) was 82 kg/ha when two hand weedings were done and 86 kg/ha when weeds were managed using thiobencarb. The yield response per kg of N in the respective treatments was 20 and 24 kg of grain. The weed dry weight was significantly lower in thiobencarb and hand weeded plots compared with unweeded check though the difference in weed dry weight due to the former two treatments was not significant.     

荸荠枯萎病病原菌及其生物学研究

１９９６－１９９７年用诊断剂地监测,证明冀鲁豫６个棉铃虫种群对三氟氯氰菊酯,氯氰菊酯,灭多威,久效磷和辛硫磷已有较高的抗性效率。其中３３％的样本抗性频率顷５０％以上,５１％的样本抗性频率在２０％－５０％之间,只有１６％的样本抗性频率在２０％以上。点滴法测定结果表明,棉铃虫对三氟氯氰菊酯的抗性指数在４７．倍以上,最高达１９５．６倍。     

棉铃虫对拟除虫菊酯的抗性稳定性研究

应用生物测定的方法研究了棉铃虫Ｈｅｌｉｃｏｖｅｒｐａａｒｍｉｇｅｒａ（Ｈüｂｎｅｒ）对溴氰菊酯高抗（１３６．７３倍）、对三氟氯氰菊酯（９．５０倍）和凯明二号（３．４０倍）低抗的３个种群的抗性稳定性。结果发现,无论棉铃虫的抗药性是高或低,在连续几代不接触药剂的情况下,都表现为抗性不断下降;第８代后３个种群都表现为抗性基本稳定,变化不大。停药后第８代分出部分种群作抗性再恢复试验,经６代连续点滴筛选后,３个种群抗性都有所回升。而且,棉铃虫对单剂抗药性衰退明显,但再恢复较快;对混剂的抗性衰退慢,再恢复也慢。     

棉铃虫对拟除虫菊酯农药的抗性治理效果评价

作者在河北省定州市600hm~2棉田设立了棉铃虫抗药性治理示范区,采取以降低农药的选择压和利用敏感个体的稀释作用为出发点的一系列措施,实施了抗性治理。为评价治理效果,1991～1995年连续监测了河北省3个地区棉铃虫对氰戊菊酯、溴氰菊酯、氯氰菊酯和三氟氯氰菊酯的抗药性水平。结果表明,在非治理区,固安县种群的抗性指数(RR)由1991年的9.8～15.5倍,上升到1995年的26.1～85.3倍;故城县种群由31.1～57.7倍,上升到90.7～155.4倍;而抗性治理区定州市种群的抗性发展却较缓慢,稳定保持在18.0～25.0倍之间的中抗水平,证明抗性发展得到了有效控制。与非抗性治理区比较,定州棉田棉铃虫的虫口数下降4～8倍、防治费用降低23.7％～50％、纯收入增加约40％,说明抗性综合治理获得了初步的成功。     

The effect of piperonyl butoxide on pyrethroid-resistance-associated esterases in Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae)

Pyrethroid resistance in field populations of Australian Helicoverpa armigera (Hübner) is primarily a consequence of the overproduction of esterase isoenzymes which metabolise and sequester pyrethroid insecticides. Biochemical studies have shown that pyrethroid-resistance-associated esterases in H armigera are inhibited by the insecticide synergist piperonyl butoxide (PBO). Esterase inhibition by PBO did not occur immediately after dosing, but exhibited maximum inhibition 3-4 h after dosage. Esterase activity subsequently recovered until full activity was restored by 24 h. Topical bioassays using a pre-treatment of PBO showed that maximum H armigera mortality was achieved with pre-treatment times corresponding to maximum esterase inhibition. These results demonstrated that, with correct temporal application, PBO can restore pyrethroid efficacy against H armigera. It would also be expected that restoration of efficacy with other conventional insecticides, currently compromised by esterase-based resistance mechanisms, would occur.     

兰州市桃蚜抗药性监测及治理对策研究

以甘肃省宕昌县桃蚜为敏感种群,测定了兰州、永登等地桃蚜对6种杀虫剂抗药性。结果表明兰州市安宁区桃蚜对溴氰菊酯已产生低水平抗性(6.84倍),对氰戊菊酯则处于耐药力增高或敏感性降低阶段,对灭多威、敌敌畏、氧乐果和乐果已显示出早期抗性;永登县桃蚜对溴氰菊酯和氰戊菊酯处于敏感性降低阶段,对灭多威、敌敌畏、氧乐果和乐果仍属敏感阶段;皋兰县和榆中县桃蚜对上述6种杀虫剂则处于敏感阶段。用酶抑制剂进行增效作用测定结果显示,兰州地区桃蚜的抗药性与羧酸酯酶和多功能氧化酶有关。针对兰州市桃蚜的抗药性现状和抗性机制,提出了以建立抗性监测制度、合理用药为主的抗性治理对策。