Evaluation of entomopathogenic nematodes for biocontrol of the european corn borer,Ostrinia nubilalis, on sweet corn in Israel

The potential of entomopathogenic nematodes for biological control of the European corn borer (ECB),Ostrinia nubilalis (Hübner), was evaluated under laboratory, screenhouse and field conditions. The ‘All’ and ‘Mexican’ strains ofSteinernema carpocapsae (Weiser) and the ‘HP88’ strain ofHeterorhabditis bacteriophora Poinar were compared in both dose response assays (5, 50 and 500 infective juveniles [IJ] per petri dish containing five 5th-instar ECB eggs; 72 h of incubation) and exposure time assays (3, 6 and 9 h of incubation). In the dose response assays the highest rates of ECB killing resulted from infestation with the Mexican strain ofS. carpocapsae. In the exposure time assays there were no significant differences between the killing rates of the three nematode strains. Sweet corn plants(Zea mays var.saccharata) grown in a screenhouse, were infested with ECB neonates and 4 days later sprayed with a suspension of the Mexican strain ofS. carpocapsae (50,000 IJ per plant). The number of ECB larvae found on treated corn plants after one week was significantly (P=0.05) lower (3- to 5-fold) than the number found on untreated plants. Similar treatment in the field significantly reduced the rate of economic ear damage from 20% to 5%. Contribution from the Agricultural Research Organization. No. 2260-E, 1997 series     

玉米雌穗挥发物对亚洲玉米螟幼虫取食选择的影响

为了探明玉米雌穗挥发物组成及其对亚洲玉米螟(Ostrinia furnacalis)幼虫取食行为的影响,本研究利用顶空吸附法及气相色谱/质谱联用技术(GC/MS)测定了离体玉米雌穗的挥发物组分,并通过幼虫取食选择试验测定了11种玉米雌穗挥发物在4个不同浓度下(5×10-6、5×10-5、5×10-4、5×10-3g/mL,正己烷为溶剂)对亚洲玉米螟取食行为的影响。结果表明:从离体玉米雌穗中共计收集并鉴定出32种挥发物组分,主要包括绿叶气味物质、萜类化合物和脂肪族化合物。其中,萜类化合物的含量最高,占玉米雌穗挥发物总释放量的84.40%。在所有测定的浓度范围内,β-石竹烯、十四烷表现为引诱活性,壬醛表现为驱避作用。除浓度为5×10-3 g/mL外,癸烷、反-罗勒烯、6-甲基-5-庚烯-2-酮对幼虫取食表现为引诱作用。     

Cyanazine metabolism in corn,fall panicum,and green foxtail*

The metabolism of cyanazine (2-chloro-4-(1-cyano-1-methyl-ethylamino)-6-ethylamino- 1,3,5-triazine) by corn (Zea mays, L.), fall panicum (Panicum dichotomiflorum Michx.), and green foxtail (Setaria viridis L.) was compared. Cyanazine metabolism by plants at the four-leaf stage was examined by thin-layer chromatography following foliar or root treatments with ¹⁴C-cyanazine. Five days following foliar ¹⁴C-cyanazine applicalion, fall panicum and green foxtail contained a larger number of water- and chloroform-soluble metabolites than corn, whereas, following root treatment, the opposite was true. Corn rapidly hydrolysed the nitrile group and hydroxylated the two-position on the triazine ring. Accumulation of the dealkylated cyanazine was evident in green foxtail, the most susceptible of the species studied. Metabolism of cyanazine supplied to the roots appeared to differ from foliar treatments in the weed species as more unchanged cyanazine was recovered. Rapid metabolism of cyanazine by corn roots provided evidence for an active cyanazine detoxication mechanism in the roots.     

防治玉米顶腐病和黑粉病药剂筛选

采用10种杀菌剂对玉米顶腐病菌室内测定结果表明,80%多&;#8226;福&;#8226;福锌可湿性粉剂、70%多&;#8226;福可湿性粉剂、97%多菌灵可湿性粉剂和98%烯唑醇可湿性粉剂抑菌效果最好,而且持效期较长。以97%多菌灵可湿性粉剂和98%烯唑醇可湿性粉剂按3〖DK1〗∶1或4〖DK1〗∶1的比例进行复配,抑菌效果达到了其各自单用的抑菌效果。经安全性测定,用98%烯唑醇可湿性粉剂进行种子包衣在低温条件下对玉米出苗和苗期生长有一定影响,97%多菌灵可湿性粉剂则无影响。田间防治试验表明,97%多菌灵可湿性粉剂或97%多菌灵可湿性粉剂与98%烯唑醇可湿性粉剂复配对玉米顶腐病和瘤黑粉病均有一定防效。在玉米4～8叶和8～12叶期时,以97%多菌灵可湿性粉剂20 g+有机硅5 mL/666.7 m2和97%多菌灵可湿性粉剂25 g+98%烯唑醇可湿性粉剂5 g+有机硅7 mL/666.7 m2用量分别喷洒,对顶腐病的防治效果达90%左右,并可兼治瘤黑粉病,防治效果达70%左右。     

玉米产业的新威胁——玉米细菌性条斑病

玉米细菌性条斑病是一种对玉米造成严重危害的新型细菌性病害,其病原为Xanthomonas vasicola pv. vasculorum,近10年间传播迅速,从非洲蔓延至南北美洲,目前分布于美国、巴西、阿根廷和南非等国家。本文对玉米细菌性条斑病的病原分类地位、危害症状、寄主、地理分布、传播途径、侵染循环、检测方法以及防控措施进行简述,以降低病菌随贸易传入我国的风险。     

亚洲玉米螟危害蛀孔在春玉米上的分布及其与产量损失的关系

亚洲玉米螟1、2代幼虫在河北张家口春玉米上的危害蛀孔 ,分布在雌穗着生节 (含穗柄 )及其上、下1～3节上的百分比分别为89.9%和85.7%。 1代幼虫蛀孔42.0%分布在雌穗下 1～3节 ,26.8%分布在雌穗上1～3节 ,每株平均有1.8个和2.1个蛀孔。玉米品种逐单 1号和自 330分别减产 19.3%和 23.5%。蛀孔数与产量呈极显著负相关 ,每株增加 1个蛀孔 ,两个品种产量损失率分别为 11.04%和 13.17%。雌穗上部 1个蛀孔的产量损失系数为3.9和 2.9,雌穗下部 1个蛀孔为 16.4和 12.4。 2代幼虫蛀孔 45.7%分布在雌穗以上茎节 ,28.5%分布在雌穗以下茎节 ,每株有 1～6个蛀孔时 ,蛀孔数与产量损失相关系数均未达到 5%的显著标准。     

Discovery and structure optimization of a novel corn herbicide,tolpyralate

Tolpyralate, a new selective postemergence herbicide developed for the weed control in corn, possesses a unique chemical structure with a 1-alkoxyethyl methyl carbonate group on the N-ethyl pyrazole moiety. This compound shows high herbicidal activity against many weed species, including glyphosate-resistant Amaranthus tuberculatus. Tolpyralate targets 4-hydroxyphenylpyruvate dioxygenase (4-HPPD), which is involved in the tyrosine degradation pathway. Inhibition of the enzyme destroys the chlorophyll, thereby killing the susceptible weeds. Details of tolpyralate discovery, structure optimization, and biological activities are described.     

Triazine absorption by excised corn root tissue and isolated corn root protoplasts

Absorption of four triazine herbicide analogs [ametryn (2-(ethylamino)-4-(isopropylamino)-6-(methylthio)-s-triazine), atrazine (2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine), atratone (2-methoxy-4-(ethylamino)-6-(isopropylamino)-s-triazine), and hydroxyatrazine (2-hydroxy-4-(ethylamino)-6-(isopropylamino)-s-triazine)] was compared using excised corn (Zea mays L.) root segments and isolated corn root protoplasts. The tissue absorbed ametryn, atrazine, and atratone for only 20 min. Ametryn and atrazine permeated tissue to passive equilibrium with the ambient solution in 10 min. Atratone permeated to 65 and 82% of passive equilibrium in 10 and 30 min, respectively. In contrast, hydroxyatrazine concentration in tissue was only 15 and 70% of the ambient concentration at 30 min and 24 hr, respectively. However, hydroxyatrazine permeated frozen/thawed tissue to 90% of passive equilibrium in 10 min. Protoplast absorption of ametryn and atratone was complete in 10 sec; hydroxyatrazine absorption by protoplasts did not reach a plateau until 5 min. Protoplasts absorbed the triazines to greater than passive equilibrium. Three kinetically homogeneous pools were detected for ametryn, atrazine, and atratone, whereas elution of hydroxyatrazine produced four pools. The three pools for atrazine were confounded by metabolism of atrazine to hydroxyatrazine. Pools for the triazines could not be identified as the free space, cytoplasm, and vacuole as proposed previously for mineral ions. Although the plasma membrane impeded diffusion of hydroxyatrazine, all analogs penetrated into the symplast.     

新疆同域亚洲玉米螟和欧洲玉米螟发生与分布研究

中国新疆伊犁是当前世界范围内唯一一处已知的亚洲玉米螟和欧洲玉米螟同域混生区?本文通过调查这一混生区玉米螟的野外主要寄主种类及其玉米螟群体组成和混生杂交情况, 为后续开展同域近缘种种间竞争?群体进化和杂交等研究提供本底数据?在田间寄主系统调查的基础上利用mtCOⅠ基因测序和OR4基因酶切法对混生区内4个主要县市5种寄主上的986个疑似玉米螟样本进行鉴定分析?结果表明:新疆伊犁混生区内玉米螟的野外寄主主要是玉米?高粱?稗草?狗尾草和苘麻, 偶见苍耳?大麻?反枝苋等?942个样本被鉴定为亚洲玉米螟, 相似性为99.02%~100%; 44个样本被鉴定为欧洲玉米螟, 相似性为99.24%~100%?亚洲玉米螟在混生区内所有调查地内均有分布, 且比欧洲玉米螟具有更广泛的寄主范围, 其主要取食并分布在玉米?高粱?稗草?狗尾草和苘麻上, 混生比例依次为73.33%~100%?100%?88.89%~100%?95.00%~100%?100%?欧洲玉米螟分布则极为有限, 目前仅主要分布在紧邻中亚哈萨克斯坦的霍尔果斯市和伊犁河谷最东部?西天山腹地新源县的极少数区域, 所占比例较低, 且主要取食玉米, 偶见取食稗草?狗尾草, 在3种寄主上的混生比例依次为0~26.67%?0~11.11%?0~5.00%?所有样本未发现杂合个体, 均为纯合体?综上, 亚洲玉米螟目前已在混生区内所有主要寄主植物上均成功取代欧洲玉米螟, 成为混生区绝对优势种?     

Effects of root diffusates of some weeds associated with corn plantations on the hatchability of the corn cyst nematode,Heterodera zeae

Twenty two summer weeds belonging to fifteen plant families and twelve winter weeds from eight plant families were tested to compare the effects of their root diffusates with the corn root diffusates (CRD) of cv. Giza 2 on the hatchability of the corn cyst nematode (CCN),Heterodera zeae.All tested weed root diffusates (WRD) successfully stimulated the hatchability of the cysts, but less than CRD did except the root diffusates (RD) ofRumex dentatus which failed to stimulate the nematode cysts.     

Susceptibility of field-collected populations of the southwestern corn borer,Diatraea grandiosella,to Bacillus thuringiensis

The susceptibilitity of newly hatched larvae of laboratory-adapted and field-collected populations of the Southwestern corn borer, Diatraea grandiosella (Dyar) (Lepidoptera: Crambidae), to a Bacillus thuringiensis protein (Cry1Ab) was examined using a larval feeding bioassay. D grandiosella populations were collected from five states: Missouri, Kansas, Texas, Tennessee and Kentucky. Using larval mortality as the end-point of the bioassay, the magnitude of differences in the susceptibility of the laboratory-adapted and the field-collected populations to Cry1Ab protein varied from one to 46 times depending on the time of observation and the standard of comparison (LC50 or LC95). However, significant differences in susceptibility to Cry1Ab protein among these populations were not detected when the comparisons were based on growth inhibition (EC50 or EC95); the magnitude of differences was less than fourfold. Either using larval mortality or larval growth inhibition, the results indicated that the field-collected populations of D grandiosella were susceptible to Cry1Ac, and differences in susceptibility may reflect natural variation among populations. The bioassay using larval growth inhibition offers advantages over that using larval mortality, including giving more accurate representation of the toxicological effects of the toxin.     

中国玉米绿色储运与生物安全处置技术进展

我国为玉米Zea mays生产、进口和消费大国之一,安全储藏至关重要。该文简要综述玉米干燥、机械通风、氮气气调、低温储藏和谷物冷却等储粮技术以及熏蒸、气调、热处理、辐照和复合处理等生物安全处置技术的研究进展,提出贯彻绿色生态储粮理念,综合控制玉米品质和有害生物,坚持发展环境友好型处置技术,构建绿色储运与害虫治理标准。     

Improved weed mapping in corn fields by combining UAV-based spectral,textural, structural,and thermal measurements

BACKGROUND

Spatial-explicit weed information is critical for controlling weed infestation and reducing corn yield losses. The development of unmanned aerial vehicle (UAV)-based remote sensing presents an unprecedented opportunity for efficient, timely weed mapping. Spectral, textural, and structural measurements have been used for weed mapping, whereas thermal measurements—for example, canopy temperature (CT)—were seldom considered and used. In this study, we quantified the optimal combination of spectral, textural, structural, and CT measurements based on different machine-learning algorithms for weed mapping.

RESULTS

CT improved weed-mapping accuracies as complementary information for spectral, textural, and structural features (up to 5% and 0.051 improvements in overall accuracy [OA] and Marco-F1, respectively). The fusion of textural, structural, and thermal features achieved the best performance in weed mapping (OA = 96.4%, Marco-F1 = 0.964), followed by the fusion of structural and thermal features (OA = 93.6%, Marco-F1 = 0.936). The Support Vector Machine-based model achieved the best performance in weed mapping, with 3.5% and 7.1% improvements in OA and 0.036 and 0.071 in Marco-F1 respectively, compared with the best models of Random Forest and Naïve Bayes Classifier.

CONCLUSION

Thermal measurement can complement other types of remote-sensing measurements and improve the weed-mapping accuracy within the data-fusion framework. Importantly, integrating textural, structural, and thermal features achieved the best performance for weed mapping. Our study provides a novel method for weed mapping using UAV-based multisource remote sensing measurements, which is critical for ensuring crop production in precision agriculture. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.