SOME EFFECTS OF DROPLET SIZE AND POSITION ON THE RESPONSE OF LETTUCE TO SUB-LETHAL DOSES OF MCPA

Summary. Senescent, expanded or expanding leaves of lettuce plants were treated individually with MCPA. The subsequent development of auxin-induced symptoms throughout the plants was recorded. The number of leaves affected and the severity of the symptoms increased with application to the less mature leaves. In addition more leaves were affected when the application was made to larger plants than to smaller ones. These results were associated with absorption/translocation differences in the leaves of different ages, and in their spatial relationship to tissues at particularly susceptible stages of development. In further experiments, applications of similar weights of MCPA to lettuce plants in droplet sizes of approximately 100 μ and 500 μ were compared. There were consistent trends for the small droplets to produce greater effects.
Quetques effets de la taille des gouttelettes et de leur position sur la reaction de la laitue à des doses sub-létales de MCPA     

THE PHYTOTOXICITY OF SOME HERBICIDES IN FIELD AND POT EXPERIMENTS IN RELATION TO SOIL PROPERTIES

Summary. The phytotoxicities in a number of soils of lenacil, linuron, prometryne and simazine to two indicator plants were determined in field and glasshouse experiments. The results were compared with estimates of the adsorption capacity of the soils obtained by two methods using dimethylaminobenzaldehyde as a model adsorbate. The possible influence of other soil properties was also considered.
One of the adsorption measurements had some predictive value for glasshouse behaviour but was not markedly superior to soil organic carbon content for this purpose. None of the factors studied was usefully correlated with field performance. Results from field experiments in spring were poorly correlated with those from similar experiments in autumn. Neither set of field results related closely to those obtained in the glasshouse. It is concluded that the influence of climate was more important than that of soil type.
La phytotoxiciti de quelquts herbicides dans des experiences en pots et en plein champ, en relation avec les propriétés du sol     

LONGEVITY OF CROP AND WEED SEEDS: SURVIVAL AFTER 20 YEARS IN SOIL

Summary. Results are presented of a 20-year investigation into survival of crop and weed seeds in undisturbed soil. Indications are that seeds reveal their survival potential during the first 4 years; only rarely did species which persisted for this initial period lose all viability in the subsequent 16 years.
Deterioration occurred more rapidly in acid peat than in loam soil, and the species which persisted in peat also remained viable in loam soil.
The Gramineae were short-lived in the soil, with the exception of Phleum spp., some seeds of which persisted for 20 years. Most leguminous species persisted for the whole period but not to the same extent as some of the weed species. Of the weeds, the species with the highest percentage seed survival were Ranunculus repens (53%), Chenopodium album (23%) and Rumex crispus (18%).
Longévité des semences de plantes cultivées et de mauvaises herbes: survivance après 20 années dans le sol     

蝉拟青霉防治菜粉蝶幼虫试验

蝉拟青霉对菜粉蝶幼虫有较强的致病性。田间试验,幼虫期喷洒2.4～1.8孢子,ml孢子悬浮液,感病率达65～70％。而在卵期施菌,可使90％初孵幼虫感病死亡。此菌可在一些自然基物上培养,能形成大量分生孢子,室温下贮存一年不失活性     

灭幼脲类杀虫剂—XRD—473对桔潜叶蛾,桔木虱及其天敌的毒杀试验

ＸＲＰ－４７３是灭幼脉类杀虫剂，试验结果表明，对柑桔潜叶蛾和柑桔木虱有较好的防治效果，对一些柑桔害虫的天敌较安全。用７０ｐｐｍＸＲＤ－４７３防治潜叶蛾１－２龄幼虫，校正死亡率为７８．７％和９３．６％，作为对比的杀灭菊酯为２２．％。用５０ｐｐｍ防治柑木虱初龄若虫校正死亡率９１．１５％，但对上述两种害虫的老龄幼、若虫效果稍差。用５０ｐｐｍ对脯食性天敌草蛉、蜘蛛、瓢虫捕螨田间施药试验，１０天后几种天敌数     

三种化学除草剂对水葫芦象甲的影响

室内外就草甘膦、克芜踪、农得时３种除草剂对水葫芦象甲卵、幼虫、蛹和成虫的影响进行了初步测试。象甲卵直接接触３种除草剂药液和清水对照后,孵化率分别为８３．３％、９３．３％、９２．２％和９５．６％;处理有卵植株叶片后,卵的孵化率分别为９０．０％、５３．４％、８５．６％和９３．６％。３种除草剂对初孵幼虫存活和蛹的羽化影响不大。但用克芜踪和农得时处理的叶片喂食象甲后,成虫产卵量分别为０．１７和０．２７粒／（对ｄ－１）,取食量分别为１０．８０和８．７０个取食斑／（对ｄ－１）,明显低于对照的产卵量１．１４粒和取食量１５．４０个／（对ｄ－１）,而草甘膦处理后象甲产卵量为１．１４粒／（对ｄ－１）,取食斑为１６．５０个／（对ｄ－１）,与对照差异不显著;克芜踪处理后７０天,象甲全部死亡,而草甘膦、农得时和对照的存活率分别为９２．５％、９５．０％和９７．５％。综合比较结果,３种除草剂对象甲的毒性影响依次为克芜踪＞农得时＞草甘膦     

影响两种蚜茧蜂日产卵量因素的研究

本文以桃蚜为寄主,研究了寄主密度、接蜂时间和环境温度对烟蚜茧蜂、菜蚜茧蜂的日产卵量及寄生率的影响。结果表明3种因素均对两种蚜茧蜂的产卵量有不同程度的影响。两种蚜茧蜂的日产卵量随寄主密度增加而增加,在27～32℃时,烟蚜茧蜂雌蜂活动频繁,羽化后第一天的产卵量多于低温(≤23℃)下的产卵量,从第二天起日产卵量下降,说明持续高温不利于雌蜂产卵。本研究认为:人工繁殖烟蚜茧峰时,温度为23℃,寄生蜂与寄主比为1:100的条件较为适宜。     

茶足柄瘤蚜茧蜂引种研究

茶足柄瘤蚜茧蜂,于1983年由美国俄克拉何马州引到陕西省泾阳县,可寄生于麦二叉蚜、棉蚜、豆蚜、酸模蚜、禾谷缢管蚜、玉米蚜。1983～1986年在棉田、小麦田、杂草地及植物园温室分别放蜂21307、11508、2933和19562头。1987年调查放蜂结果:棉田棉蚜僵蚜出蜂172头中,未见引进蜂;小麦田禾谷缢管蚜和麦二叉蚜分别出蜂34和314头,各有引进蜂1头;杂草地豆蚜出蜂420头中,有引进蜂6头;在植物园温室扶桑与海桐上僵蚜率分别为49.3％和32.2％,全是引进蜂。对影响茶足柄瘤蚜茧蜂在陕西定殖的因素作了讨论。     

东方钝绥螨对桔全爪螨和柏小爪螨的捕食作用

作者研究了东方钝绥螨对桔全爪螨和柏小爪螨的捕食作用。结果表明,东方钝绥螨对两种害螨的功能反应都为Holling Ⅱ型;其自身密度对捕食率具有干扰作用,密度增高,捕食率下降;同时,对害螨螨态的取食具有选择性,其幼、若和成螨都最喜食害螨的幼若螨。     

非致死浓度农药对智利植绥螨产卵孵化和定居的影响

在实验室内用6种农药的非致死浓度(LC_(0-0.7)),处理感染有叶螨卵的菜豆叶,观察对智利植绥螨产卵量和卵孵化率的影响。结果表明:尼索郎(50×10~(-6))和卡死克(50×10~(-6))对智利螨的产卵量和卵的孵化都没有有害影响。双甲脒(2×10~(-6))对智利螨的产卵量无影响,但卵的孵化率仅为对照的1/3。NC-129(200×10~(-6))、天王星(0.2×10~(-6))和功夫(0.05×10~(-6))均能降低智利螨的产卵量,比对照分别减少28.3％、17.8％和14.4％。尼索郎、卡死克和双甲脒不影响温室菜豆上智利螨的定居率,NC-129、天王星和功夫则有严重影响:对照组智利螨定居率为85％,NC-129组的定居率仅为25％,天王星和功夫处理后完全没有定居。试验指出,尼索郎和卡死克对智利螨属安全农药,NC-129对智利螨有较大的影响,双甲脒、天王星和功夫对捕食螨是有害的。     

温度、湿度、气压对截头堆砂白蚁原始繁殖蚁分飞的影响

经三年的室内试验观察，探讨了截头堆砂白蚁Cryptotermes domesticus(Haviland)原始繁殖蚁的分飞与温度、湿度、气压的关系。结果表明，该种白蚁分飞时适应的温度、湿度、气压范围较广，分飞时温度一般在25℃-30℃，相对湿度介于70％-90％，气压幅度在999百帕(hPa)-1006百帕(hPa)之间。温度在27℃-30℃之间较适宜，该种白蚁分飞次数较多，其中，28℃～29℃分飞次数最多，占总分飞次数的48.89％。相对湿度在70％-85％范围内分飞次数较多，其中相对湿度在75％-80％范围内分飞次数最多，占总分飞次数的35．35％。气压在1003百帕(hPa)～1005百帕(hPa)之间分飞次数较多，其中气压在1004百帕(hPa)-1005百帕(hPa)之间分飞次数最多，占总分飞次数的35．59％。     

高孢子含量Bt制剂对桃小食心虫毒效的初步试验

本文报道国产高孢子含量Bt(1.6×10~4IU)可湿性粉剂对挑小食心虫初孵幼虫的室内和田间药效,及其与低浓度化学农药混用的试验结果。室内实验表明,在苹果上分别喷洒高含量Bt可湿粉1000和2000倍液后接虫,第3天幼虫蛀果率均为零;喷洒2.5％溴氰菊酯(3个供试浓度)的结果与之相同,亦无1头幼虫蛀入果内。但是,高含量Bt可湿粉2000倍液在田间的残效期较短,施药后第3和第6天在苹果上接虫,死亡率分别为45.5％和54.6％。本试验观察到,高含量Bt可湿粉2000倍与2.5％溴氰菊酯6×10~4倍液混配后,明显延长了田间残效期,施药后第3和第6天接虫,幼虫死亡率分别为84.4％和73.2％,其杀虫效果相当于生产上常用的50％对硫磷1500倍液。     

利用食蚜瘿蚊防治保护地蔬菜桃蚜的试验

在蔬菜温室、弓棚、大棚内释放食蚜瘿蚊防治桃蚜,当单株蚜量在200头以下时,以1:20益害比释放瘿蚊成虫,9～12天后温室、弓棚内桃蚜分别减退75.1％～91.8％和80.1％～90.5％。1990年在5个大棚内以1:20益害比,一次释放,10天后蚜虫减退82.2％,30天后蚜虫有所回升,单株蚜量141.2头。1991年6～7月份,在16个大棚内分别释放瘿蚊,当单株蚜虫146头时,按1:20益害比,在2周内分2～3次释放瘿蚊,10天后单株蚜量减退86.4％,以后蚜虫仍逐日下降,在拉秧前60天内能有效地控制蚜害,不需使用化学农药。