大豆蚜Aphis glycines Matsumura的研究

大豆蚜在我国主要大豆产地都有分布, 以吉、辽、黑和内蒙自治区的一部分为害最重, 为猖獗发生区。大豆蚜的寄主植物除大豆外, 还有野生大豆和鼠李, 由调查和接种试验的结果, 肯定了大量地分布在东北三省的鼠李为越冬寄主。 大豆蚜的全年发生周期和为害特点在大豆上共分三个阶段:1)从侵害豆苗起到7月中旬大豆盛花期止, 是大豆蚜的盛发时期, 占有总蚜量的50—70%, 群聚于豆株上部幼嫩的枝叶上, 这时期的为害, 对大豆的生长威胁最大;2)到7月下旬, 由于大豆生长点停止生长, 大豆蚜即从群聚于植株上部发生转移到分散在中、下部的叶片背面, 并同时出现小型蚜, 生长迟缓, 为田间大豆蚜为害的消退阶段;3)8月下旬结荚后期到9月上旬黄熟期, 重新开始了大豆蚜的后期繁殖阶段, 随即在秋末季迁回鼠李, 经雌雄交配产卵越冬, 秋季雄性蚜和雌性产卵蚜分别发生在不同的寄主上, 雌性发生在鼠李上, 雄性发生在大豆上。全年在大豆上共繁殖15代。 根据大豆蚜的生活规律和几年来田间消长规律并结合几年的气象资料综合分析的结果, 初步得出大豆蚜的发生消长规律和其影响因子:1)上年越冬量及早期田间蚜量大, 因而造成了苗期大发生;2)6月下旬至7月上旬的旬平均温度在22—25℃, 相对湿度在78%以下时, 则极有利于田间大豆蚜的发育和繁殖, 即使早期蚜量少, 由于繁殖快, 往往也能造成7月花期的大发生;3)7月底开始随着大豆生长点的停止生长, 由于营养条件的恶化, 造成了大豆蚜的消退阶段。 综合上述, 我们可以根据大豆蚜的越冬数量、气象预报、历年的蚜情资料和当年的蚜情调查, 做出长期或短期的蚜情预报。 防治方法, 从几年的室内外试验和大面积试验结果, 0.5%666、6%可湿性666300—400倍、E605 15000倍、烟草冰100倍液以及20% 666拌种都具有良好的毒杀作用, 其中0.5%666粉和20%666 以种子量的0.7%用药量拌种已广泛推广应用于生产。     

桃一点叶蝉Erythroneura sp.在南京的生活习性观察及防治试验

桃一点叶蝉在长江流域为桃的重要害虫, 据在南京、徐州、洞庭东山等地调查, 为害桃的叶蝉共有4种即:桃一点叶蝉Erythroneura sp. , 小绿叶蝉Empoasca flavescens, 大绿叶蝉Cicadella viridis及棉叶蝉Chlorita biguttula。以桃一点叶蝉为主。它的主要寄主是桃, 其他尚有杏、李、中国樱桃、贴梗海棠、月季、苹果、梨等。桃一点叶蝉在南京一年发生四代, 以第四代成虫在常绿树如龙柏、侧柏、柳杉、桧柏、马尾松、杨梅上越冬。至早春桃现蕾萌芽时, 从越冬寄主上大部分直接迁飞到桃上, 少量可到其他寄主上, 4月以后都集中到桃上, 直到晚秋开始作越冬之迁飞。至11月中下旬全部迁到常绿树上越冬。 室内药效测定结果:25％马拉松乳剂, 30％E-605及25％DDT乳剂效果最好, 41％敌百虫效果不好, 效果最差的是10％γ666乳剂。两次田间防治试验结果与室内一致。在桃园内为避免经常使用DDT而引起螨类的大发生, 可采用马拉松, E-605来代替或与DDT混合使用防治桃一点叶蝉及其他桃树害虫。     

First record of an apparently rare fig wasp feeding strategy: obligate seed predation

1. Fig trees require host‐specific agaonid fig wasps for pollination, but their figs also support numerous non‐pollinating fig wasps (NPFW) that gall fig tissues or develop as parasitoids. 2. Ficus microcarpa L. is widely naturalised outside its native range and the most invasive fig tree species. Seed predators are widely used for the biological control of invasive plants, but no obligate seed predatory (as opposed to ovule or fig wall galling) NPFW have been recorded previously from any fig trees. 3. Philotrypesis NPFW are usually regarded as parasitoids or ‘inquilines’ (parasitoids that also eat plant material) of pollinator fig wasps, but the present study provides evidence that Philotrypesis taiwanensis, a NPFW associated with F. microcarpa, is an obligate seed predator: (i) adults emerge from seeds of typical appearance, with a surrounding elaiosome; (ii) it shows no preference for figs occupied by fig wasp species, other than the pollinator; (iii) it only develops in figs that contain pollinated ovules, avoiding figs occupied by an agaonid that fails to pollinate; (iv) larvae are distributed in layers where seeds are concentrated and (v) it has a negative impact on seed but not pollinator offspring numbers. 4. Philotrypesis is a large genus, and further species are likely to be seed predators.     

Evidence for sexual attraction pheromones released by male tropical donkey's ear abalone (Haliotis asinina), (L.)

Abstract

The tropical donkey's ear abalone (Haliotis asinina) is routinely collected in many parts of the Indo-Pacific and has significant potential for commercial aquaculture. Although its reproductive cycle has been investigated, no studies have reported the use of chemical signals to coordinate reproduction and spawning. Using a bioassay designed with one caged individual, whilst the other is free to roam, we investigated the presence of attraction pheromones released from mature individuals. Only mature females were attracted to caged mature males with all other treatments showing no significant attraction. Those mature females also took significantly less time to reach the mature males than other pairings. Temperature influenced the response with the maximum number of positives occurring between 25 and 31°C, which coincides with the optimum physiological temperatures and the spawning times for this species. We have also shown that the attraction pheromone is present in mature male testes and induces stereotypical pre-spawning behaviours (sweeping epipodial and cephalic tentacles) as well as attracting females. Some individuals also moved towards the surface of the water, this may also be a pre-spawning behaviour. This is the first time that a sexual attraction pheromone has been reported for any haliotid species and is likely to have a critical function in the synchronization of spawning in the wild between sexes.     

Estimation of survival rate and oviposition interval of Anopheles balabacensis mosquitoes from mark-recapture experiments in Sabah, Malaysia

An exophilic population of the vector mosquito Anopheles balabacensis Baisas was investigated in two mark-recapture studies (16.ix-13.x.1986 and 6-26.i.1987) at an inland, foothill village in Sabah, Malaysia. Wild female mosquitoes were intercepted as they came to feed on man or buffalo, given a bloodmeal, marked with fluorescent dust and released. The recapture rate was about 12%. A new method of analysis is proposed which uses cross-correlation and a time series model. The estimated survival per oviposition cycle was 0.48-0.54 and the oviposition cycle interval 2-3 days.     

The influence of permethrin-impregnated bednets and mass drug administration on the incidence of Plasmodium falciparum malaria in children in Sabah, Malaysia

A small-scale trial was carried out in the Upper Kinabatangan district of Sabah, Malaysia, to determine the effect of using permethrin-impregnated bednets on malaria transmission. A total of 306 nylon bednets with cotton borders, impregnated at a dose estimated to have been 0.062 g permethrin/m2 of nylon netting, were distributed to 139 households in five villages. At the time of distributing bednets, mass drug administration with Fansidar plus primaquine was also administered to the human population to clear all parasitaemias due to Plasmodium falciparum Welch. In another village, for comparison, mass drug administration was the only intervention. After intervention measures in December 1984 and January 1985, the parasite rates in children declined in all villages during the first month, significantly more in the villages with impregnated bednets than in the control, thus proving that the nets had an impact on malaria. However, after about 2 months, parasite rates started to increase again. After 4-6 months, parasite rates in the villages with bednets approached the rate in the control village without nets. The increase in parasite rates was paralleled by a significant deterioration in the quality, physical condition and the degree of non-utilization of bednets. Entomological evaluation proved the efficacy of permethrin-impregnated nets for controlling Anopheles balabacensis Baisas and other anophelines. Bioassays (1 h exposure) of permethrin-impregnated bednets gave 100% mortality initially and 44-61% mortality after 85-106 days. Mosquito collections in treated bednets were significantly reduced for at least 217 days. The project failed to achieve prolonged suppression of malaria transmission for a combination of entomological, sociological and practical reasons which are discussed in relation to the objectives and implementation of future bednet studies.     

Impact of permethrin-impregnated mosquito nets compared with DDT house-spraying against malaria transmission by Anopheles farauti and An.punctulatus in the Solomon Islands

Abstract. In villages of northern Guadalcanal in the Solomon Islands, where the predominant malaria vector is An.farauti No. 1 and An. puctulatus is also involved, malaria transmission rates were compared for three zones: (1) non-intervention: 438 people in seventeen villages; (2) residual DDT house-spraying two cycles per year: 644 people in thirty villages; (3) bednets impregnated with permethrin 0.5 g/m² twice per year, used by 580 people in sixteen villages. Regular DDT spraying in zones 1 and 3 had been withdrawn 18 months previously. Malariological blood smear surveys of children aged 1-9 years in August 1986 to January 1987 showed a mean-baseline malaria parasite rate of 38% (32/84). By February 19 88 , 18 months after introduction of impregnated bednets, the Plasmodium falciparum infection rate in children was lowest in the zone using impregnated bednets (21% of 29), intermediate in the untreated zone (29% of 34) and highest in the DDT zone (46% of 53), but these differences were not statistically significant. P.vivax infection rates were 9–14%. Using ELISA tests for malaria circumsporozoite antigen in the vectors, overall positivity rates were 0.7% of 49 ,902 An.farauti and 2.54% of 118 An.punctulatus, comprising 228 P.falciparum and 124 P. vivax infections. In the study zones, vector positivity rates were 0.93% of 31 ,615 An.farauti in the untreated zone; 0.32% of 16, 883 An.farauti in the DDT zone; 0.07% of 1404 An.farauti and 2.54% of 118 An.puctulatus in the impregnated bednet zone. There was no significant correlation between malaria parasite rates in the vectors and the children. Entomological inoculation rates were consistently highest in the untreated zone (1.6–2.8 infective bites/night), intermediate in the DDT zone (0.8– 1.1/night) and significantly lowest in the bednet zone (0.03-0.23/night). Geometric mean densities of P.falciparum sporozoites were also significantly higher in the DDT zone (50% > 10,000 sporozoites/mosquito compared with 20% in untreated zone). The highest individual infection density was an estimated 52,080 sporozoites of P.falciparum in a specimen of An.punctulatus from the bednet zone. P.vivax sporozoite densities were not significantly different between zones, and both species of vector had similar mean sporozoite loads for both species of malaria. It is concluded that permethrin-impregnated mosquito nets exerted significantly more impact on vector infectivity and the inoculation rate than resulted from DDT spraying. Even so, the inoculation rate for people in the bednet zone remained at one infective bite every 4–32 days, an insufficient reduction to control malaria without additional countermeasures. Ineffectiveness of house-spraying and the limited impact of impregnated bednets are attributed to exophily and other behavioural aspects of An. farauti.