Free amino acid content of phloem sap from Brassica plants in relation to performance of Lipaphis erysimi (Hemiptera: Aphididae)

Cultivars of Brassica juncea, B. napus and B. campestris, differing in host-suitability to the mustard aphid (Lipaphis erysimi pseudobrassicae Kalt.), were analysed for their phloem sap content of free amino acids. Sap was collected from excised mustard aphid stylets and analysed by means of high performance liquid chromatography. Aspartic and glutamic acid were, together with glutamine, the dominating amino acids. All plants had very little glycine, γ-aminobutyric acid (GABA), methionine and tryptophan in their sap. This amino acid pattern closely resembled that of cereals. The total concentration and the individual composition of amino acids were not found to be related to the level of aphid resistance previously found in the investigated Brassica species. However, one B. campestris cultivar, yellow sarson YSB-9, on which the aphids were shown to grow more slowly, had less amino acid content than other B. campestris varieties. The slow population growth of aphids on B. juncea, compared to that on B. campestris, is probably due to other than nutritional factors.     

萝卜蚜不同虫口密度下的二项式抽样设计

基于1990—1992年间对杭州市郊区小白菜上萝卜蚜（Lipaphiserysimi）种群的田间抽样调查数据,根据虫口密度（m）,将数据归为两组,一组为整个虫口密度范围的数据;另一组为虫口密度≤5头／株范围的数据．每组数据选择不同的数阈值（T）,利用每样方不超过T头蚜虫的植株比例（P_T）与种群密度的关系,通过拟合经验公式Ln进行二项式抽样设计．对抽样方差（用MSE估计）、抽样精度（用d估计）进行分析发现,当用整个密度范围的数据进行拟合,且种群处于较高密度（m≥5）时,其理想的T值为10,可用于小白菜上萝卜蚜种群的二项式抽样设计．当用虫口密度m≤5的数据进行拟合时,T＝4时可保证抽样精度,但从实际应用考虑,则不宜用于萝卜蚜的二项式抽样设计．应用本文方法所发展的0—1抽样方法,无论是在整个密度范围还是在密度≤5的范围,都由于产生较大的抽样误差而不宜用于萝卜蚜。     

Effects of mixed prey on the development and demographic attributes of a generalist predator,Coccinella septempunctata (Coleoptera: Coccinellidae)

Coccinella septempunctata Linnaeus, 1758 (Coleoptera: Coccinellidae) is an aphidophagous ladybird beetle species with cosmopolitan distribution. However, it may also thrive on arthropods other than aphids, when the latter are not readily available. Certain life history traits and demographic attributes of C. septempunctata were determined using seven different diets with different alternations and proportions of an aphid, Lipaphis erysimi (Kaltenbach,1843) and a mite, Tetranychus urticae Koch, 1836, in the laboratory (at 25±0.5°C, 65±5% RH and a photoperiod of 16 h L:8 h D).The larval duration was longest (12.61±6.17 days) when fed an alternating diet of two days aphid/two days mite. Adult longevity was longest (78.65±1.09 days) when fed aphids only and shortest (3.17±1.25 days) when fed mites only. Life expectancy (e_x) was highest (111 days) when adults were fed only aphids and lowest (11.3 days) when fed only mites. Survival rates of ladybird beetles were positively related to an increasing ratio of aphids in their diet. Their ability to prey on both aphids and mites indicates the effectiveness of C. septempunctata as a biological control agent on plants infested with these two pests.     

雷公藤粗提物毒力测定及甲素含量分析

以无水乙醇为溶剂从雷公藤根皮中提取有效成分,用高效液相色谱法分析雷公藤粗提物中甲索含量,并将雷公藤粗提物配成5％的乳油,用浸叶法和药膜法测定小菜蛾二龄幼虫、烟粉虱成虫以及无翅成蚜的室内毒力,并以几种杀虫剂作为对比。结果表明：该批雷公藤粗提物中甲素含量为0．0012％;5％雷公藤粗提物乳油对小菜蛾二龄幼虫、烟粉虱成虫以及无翅成蚜具有一定的生物活性,但与其他几种常用杀虫剂相比活性较低,还需对其进一步精制和提纯。     

Differential effects of weather,plant phenology and predators on the seasonal variation of aphids on cabbage

The aphids Lipaphis erysimi pseudobrassicae (Davis) and Myzus persicae (Sulzer) pose serious threats to the production of cruciferous crops in the tropics. Understanding their population dynamics is important for developing integrated pest management programmes to minimize their damage to crops. This study investigated the effects of climatic factors, natural enemies and plant age on the population dynamics of these pests. The population density of aphids and their natural enemies in 20 cabbage plants, and weather conditions were monitored for five cropping seasons from 2019 to 2021 in two agroecological zones of Ghana (Coastal Savannah and Deciduous Forest zones). The highest population density of L. e pseudobrassicae was recorded in January (dry season) in both agroecological zones, while the highest population density for M. persicae occurred in September (minor rainy season) and August (dry spell) in the Coastal Savannah and Deciduous Forest zones, respectively. The highest aphid densities were noted to occur during periods with low relative humidity and low rainfall. The population density of L. e. pseudobrassicae was significantly negatively related to plant age, air temperature and relative humidity, and positively related to syrphids (Paragus borbonicus) and spiders in the Coastal Savannah zone, while in the Deciduous Forest zone, it was significantly positively related to coccinellids. On the other hand, M. persicae population density was significantly positively related to syrphids and coccinellids in the Deciduous Forest zone. Rainfall negatively affected syrphids in the Coastal Savannah zone, while air temperature positively affected syrphids and negatively affected spiders in the Deciduous Forest zone. Coccinellids had a significant positive relationship with relative humidity in the Deciduous Forest zone. This study provides important insights into the key factors that regulate aphid population densities on cabbage and will support development of timely interventions to manage these pests.     

白蝴蝶挥发油对蚜虫的驱避作用及其化学成分

室内用四臂嗅觉仪测试白蝴蝶(Syngonium podophyllum)挥发油对红桃蚜(Myzus persicae)、萝卜(Lipaphis erysimi)和瓜蚜(A[jos gossypii)无翅蚜行为选择的干扰作用．结果表明,在所测试的浓度下,白蝴蝶挥发油对瓜蚜和萝卜蚜有显著的驱避效果,与对照比较,供试蚜虫较少选择处理区,在处理区的停留时间比对照明显缩短;所测试的浓度对红桃蚜无驱避作用．进一步采用气相色谱质谱联用技术对白蝴蝶挥发油进行了成份分析．表明该挥发油小分子主要成份是羰基化合物、脂肪酸和烃．     

Reproductive rate of the Indian mustard aphid (Lipaphis erysimi pseudobrassicae) on different Brassica oilseeds: colmparisons with Swedish strains of mustard (Lipaphis erysimi erysimf) and cabbage aphid (Brevicoryne brassicae)

The reproductive rate of the Indian mustard aphid (Lipaphis erysimi pseudobrassicae), a serious pest on Brassica oilseeds in India, was compared with that of Swedish strains of mustard aphid (L. e. erysimi) and cabbage aphid (Brevicoryne brassicae) on six common Indian and Swedish Brassica oilseed cultivars. There were clear differences between L. e. erysimi and L. e. pseudobrassicae in the relative suitability of the cultivars, emphasisipg the biological differences between these aphids. B. brassicae had similar reproductive rates on all cultivars.
In addition, the reproductive rate of L. e. pseudobrassicae was measured on both young and old plants of the six Brassica oilseed cultivars and 14 Indian rai (B. juncea) cultivars. Among the six Brassica cultivars, the reproductive rates were highest on turnip rape and toria (B. campestris), and lowest on yellow sarson (B. campestris) and rai (B. juncea). The ranking of the cultivars was similar for young and old plants. There were no significant differences between the rai (B. juncea) cultivars tested, neither among young nor among old plants. These results from laboratory studies are compared with field data from India on the relative susceptibility of different Brassica oilseed cultivars to L. e. pseudobrassicae.     

杭州郊区菜蚜种群的数量消长规律

对杭州郊区菜蚜的数量消长规律进行了连续多年的系统调查 .结果表明 ,在杭州郊区十字花科蔬菜上发生的菜蚜只有桃蚜 (Myzuspersicae)和萝卜蚜 (Lipaphiserysimi) .2种菜蚜混生种群的数量消长 1年中有 2个明显的高峰 ,分别出现在 5～ 6月和 1 1月前后 ;一般年份高峰期田间虫量可达平均每株 50 0头以上 ,且第 2个高峰虫量较高 ,持续时间较长 .在夏末秋初气温明显偏低的年份 ,8～ 9月作物上虫量上升迅速 ,最高也可达平均每株上千头的水平 .盛夏和隆冬季节数量都很低 .每年的 1 2月至次年的 5月以桃蚜占绝对优势 ,7～ 1 0月以萝卜蚜占绝对优势 ,而 5～ 7月和 1 0～ 1 2月则 2种蚜虫的发生比例交错变换 .温度是决定菜蚜混生种群数量消长规律和导致 2种蚜虫季节消长规律差异的一个主要因子 .文中对食料、天敌等因子的作用也做了讨论 .     

6种非嗜食植物乙醇提取物对蔬菜蚜虫的忌避作用

室内测定了6种非嗜食植物乙醇提取物对蔬菜两种蚜虫桃蚜Myzus persicae(Sulzer)和萝卜蚜Liphis erysimi(Kaltenbach)的忌避作用,结果表明细叶桉Eucalyptus tereticornis、胜红蓟Ageratum conyzoides、洋桃Averrhoa carambola、荷花玉兰Magnolia grandiflora等几种植物乙醇提取物对两种蚜虫的忌避率均在85％以上,这为蔬菜保护剂的研制提供了依据。     

多种植物提取物对桃蚜和萝卜蚜的拒食活性研究

采用改进的蜜露色斑法 ,测试 34种植物乙醇提取物 (0 0 1g干重·mL-1,0 0 1gDW·mL-1)和几种天然源药剂对桃蚜Myzuspersicae(Sulzer)和萝卜蚜Lipaphiserysimi(Kaltenbach)取食的影响。结果表明 ,白蝴蝶Syngonium podophyllumSchott.、苍耳XanthiumsibiricumPrtr.etWidd、白花非洲山毛豆Tephrosiavo gelliHook .的提取物对两种蚜虫的活性均较高 ,2 4h对桃蚜的拒食率分别达 0 6 82、0 6 2 9和 0 80 6 ,对萝卜蚜的拒食率分别为 0 4 0 5、0 370和 0 383,与对照之间差异极显著 ;油茶Camelliaoleifera和花椒Zanthoxylumschinifolium的提取物拒食作用亦较强 ,2 4h对桃蚜的拒食率分别为 0 5 5 2和 0 5 14 ,对萝卜蚜的拒食率分别为 0 5 70和 0 5 18。三种药剂 (0 3%印楝素乳油、鱼藤酮精、机油乳剂 )在所测试的浓度对两种蚜虫的拒食率均达 0 719以上 ,拒食效果显著。