Infection of potato by Rhizoctonia solani: effect of anastomosis group

Glasshouse and field experiments showed that the pathogenicity and disease type on potato varied between different anastomosis groups (AGs) of Rhizoctonia solani. For example, severe stem and stolon disease developed in plants inoculated with a single isolate of AG3PT and AG5. Severe root disease was observed with single isolates of AG8 and to a lesser extent AG3PT, but rarely with single isolates of the other AGs tested. In both field and glasshouse experiments the AG2‐1 isolate (X81) produced only small lesions (<5 mm). However, this was not representative of two other AG2‐1 isolates. When AG2‐1 isolates of the three different rDNA IGS1 types were tested in a glasshouse trial, one caused more severe stem and stolon infection than AG3PT. In the field experiment, the yield of tubers, by weight, was significantly less (P < 0·05) in all inoculated plants than for uninoculated (control) plants. Yield losses were greatest and tuber numbers smallest in plots inoculated with an AG8 isolate, suggesting that root infection is important in determining quantitative yield loss. The incidence of black scurf was greatest in the progeny tubers in plots inoculated with AG3PT (83·9%), whereas only very small amounts of black scurf developed on tubers from plants infected with AG2‐1 (510 bp) or AG5 isolates. This is supported by laboratory tests, where isolates of AG3PT produced significantly more sclerotia on potato dextrose agar than isolates of AGs 2‐1, 4, 5 and 8.     

6种杀螨剂对黄瓜新小绥螨和朱砂叶螨的选择毒力评价

采用叶片残毒法测定了6种田间常用杀螨剂对黄瓜新小绥螨［Neoseiulus cucumeris (Oudemans)］和朱砂叶螨［Tetranychus cinnabarinus (Boisduval)］的毒力,并分析了这几种杀螨剂对这两种螨的选择毒力。结果表明：供试6种杀螨剂中甲氰菊酯与高效氟氯氰菊酯对黄瓜新小绥螨具有较强的毒力,对其成螨的LC50值分别为8.7和6.7 mg/L,且在对两种螨的毒力选择上表现为负向选择性,因此在释放黄瓜新小绥螨协同防治害螨时,需慎重选择使用。6种杀螨剂对两种螨的选择毒力大小依次为：哒螨灵>阿维菌素>炔螨特>毒死蜱>高效氟氯氰菊酯>甲氰菊酯,且哒螨灵对黄瓜新小绥螨的毒力最低,对其成螨的LC50值达到了593.7 mg/L,而阿维菌素对黄瓜新小绥螨成螨的LC50值为90.2 mg/L,对朱砂叶螨成螨的LC50值为17.8 mg/L。哒螨灵和阿维菌素具有较高的正向选择性,表明这两种杀螨剂在利用黄瓜新小绥螨及化学药剂协同防治朱砂叶螨中具有重要的应用价值。     

以甜果螨为食的东方钝绥螨的种群生命表

东方钝绥螨是叶螨的重要捕食性天敌,对多种叶螨的防控起着重要的作用。东方钝绥螨一直被认为是叶螨的专食性捕食者,其规模化生产不成功极大地限制了其应用。本试验在（25±1）℃、RH 80%±5%、光周期16L：8D的条件下,以甜果螨为食,东方钝绥螨能够完成发育和繁殖,并以此组建了东方钝绥螨试验种群生命表。试验结果表明,东方钝绥螨以甜果螨为食各发育阶段历期较短,分别为卵期1.77 d,幼螨期0.77 d,前若螨和后若螨期各为1.05 d。25℃时东方钝绥螨的世代平均周期为14.07 d,内禀增长率0.18,周限增长率1.20,种群倍增时间3.87 d。日均产卵量1.71粒/d,总产卵量平均22.50粒/雌。由此得出甜果螨是饲养东方钝绥螨的一种很好的替代猎物。     

释放巴氏钝绥螨对温室大棚茄子上西花蓟马及东亚小花蝽数量的影响

在北京市门头沟碧琨种植中心的温室大棚茄子上释放巴氏钝绥螨后,调查统计对茄子上西花蓟马及东亚小花蝽数量的影响。结果表明:释放巴氏钝绥螨对温室大棚茄子上的西花蓟马的种群数量在其高峰期具有一定的压低作用,尤其是释放200头/m2巴氏钝绥螨效果更好。温室大棚茄子上自然发生的本地天敌东亚小花蝽的种群数量,在各处理间的总体趋势相同,随着西花蓟马的数量变化而变化。     

释放捕食螨对蓟马传播烟草番茄斑萎病的控制效果

为有效防治烟田西花蓟马和烟草番茄斑萎病,分别在烟草移栽期和团棵期研究释放捕食螨种类、密度及捕食螨带白僵菌对烟田西花蓟马引起烟草番茄斑萎病的控制效果。结果表明:释放斯氏钝绥螨对烟草番茄斑萎病的控制效果略好于胡瓜钝绥螨;结合成本和防效考虑,移栽期和团棵期胡氏钝绥螨较适宜的释放密度分别为2.25×10~6头/hm~2和3.75×10~6头/hm~2;释放带球孢白僵菌的捕食螨防效低于不带球孢白僵菌的捕食螨。     

温度对胡瓜新小绥螨生殖力及钠钾泵α亚基基因表达的影响

胡瓜新小绥螨Neoseiulus cucumeris（Oudemans）广泛地用于蓟马类害虫的防治、控制及管理。本研究克隆了1条胡瓜新小绥螨钠钾泵α亚基基因序列,分析了温度对雌螨生殖力及钠钾泵α亚基基因表达的影响。在15、20、25和30℃下,胡瓜新小绥螨在25℃时生殖力最优。在上述温度条件下胁迫48 h,雌螨钠钾泵α亚基在15和30℃下表达量显著上升,能量代谢活跃。表达量越多,表明能量消耗越大,投入生殖的能量就越少,结合生殖力研究结果,二者一致。高温或低温均会降低胡瓜新小绥螨的生殖力,且高温影响更为严重。     

胡瓜钝绥螨控制柑桔害螨研究

利用胡瓜钝绥螨控制柑桔全爪螨和锈壁虱 ,研究结果表明 ,在不同生态区域胡瓜钝绥螨释放量为 90万头 /hm²,30d后防效可达 85%～95% ,控制害螨期长达 6个月 ,减少农药使用量40%～60%。生防园果实商品价值提高约1000元/667m²。本文还对在不同树龄、不同生态条件下使用捕食螨的适期、比例及配套技术等进行了研究     

水稻纹枯病菌强拮抗菌B34的分离与鉴定

 从水稻植株上分离到1株对水稻纹枯病菌有强烈拮抗作用编号为B34的菌株,在PDA平板上表现有对水稻纹枯病菌较强作用的抑菌带,其发酵菌液对纹枯病菌丝有强烈的致畸作用,抑菌率达到71.5%,使菌核的菌丝萌发率降低69.0%。离体防效和田间小区防效分别高达81%和48.74%,高于清水和井冈霉素处理。经生理生化检测及细胞壁化学成分分析,确定其为致黄假单胞菌(Pseudomonas aureofaciens)。     

Transovarial biotransference of etoxazole through a terrestrial trophic web

BACKGROUND: Transovarial transport is defined as the passage of chemicals from the maternal body to eggs within the ovaries. Little is known about the effects of transovarial transport on non‐target species. This study evaluates etoxazole (a transovarial acaricidal compound) on a terrestrial trophic web consisting of a ubiquitous phytophagous mite, Tetranychus urticae Koch, and three species of predatory mites. RESULTS: Predatory mite females that consumed eggs laid by etoxazole‐treated T. urticae also produced infertile eggs. There was a negative relationship between the proportion of etoxazole‐treated T. urticae females and the instantaneous rate of predatory mite increase at the population level (r² = 0.86). Reduced fertility of etoxazole‐treated T. urticae females continued for 18 days following application. Eggs laid by etoxazole‐treated T. urticae females remained toxic to predatory mite females for 42 days after treatment. CONCLUSIONS: Transovarial transport could lead to magnification in the ecosystem by enhancing both bioavailability and movement of an active ingredient. The potential for enhancement of residual activity by terrestrial organisms and its significance once reaching the food web should be taken into account for new classes of acaricides and insecticides. Copyright © 2012 Society of Chemical Industry