蚜小蜂和粉虱座壳孢对烟粉虱的控制作用研究

研究了烟粉虱两种寄生性天敌桨角蚜小蜂(Eretmocerus sp．)和粉虱座壳孢(Aschersonia aley-rodis)单独使用和联合使用时对烟粉虱种群的控制作用。结果表明,在单独进行控制时,在一个世代内按5×10^6个孢子·ml^-1喷施粉虱座壳孢2次,对烟粉虱种群的控制作用达95．74％,按每株植株3头雌蜂的密度释放桨角蚜小蜂2次,对烟粉虱种群的控制作用达57.58％。在两者联合控制时,一个世代内喷施粉虱座壳孢2次,再释放桨角蚜小蜂1次或2次,对烟粉虱种群的控制作用达97．02％～97．91％,烟粉虱种群增长趋势指数低于1,种群数量逐渐下降,联合使用时,桨角蚜小蜂和粉虱座壳孢间无消极影响。     

粉虱寄生蜂种类的调查与鉴定

通过采集调查、室内饲养和鉴定,初步获得福建省部分地区粉虱寄生蜂２２种,隶属于蚜小蜂科Ａｐｈｅｌｉｎｉｄａｅ的恩蚜小蜂属Ｅｎｃａｒｓｉａ Ｆｏｅｒｓｔｅｒ（１９种）和桨角蚜小蜂属Ｅｒｅｔｍｏｃｅｒｕｓ Ｈａｌｄｅｍａｎ（２种）,以及广腹细蜂科Ｐｌａｔｙｇａｓｔｅｒｉｄａｅ的Ａｍｉｔｕｓ（１种）。     

宁波地区烟粉虱及其寄生蜂调查

烟粉虱Bemisia tabaci(Gennadius)是重要的世界性害虫之一,对农业生产造成了严重的危害.利用天敌对烟粉虱进行生物防治已经成为研究重点.本文于2007年6月至2008年11月对宁波地区不同寄主作物上烟粉虱虫口数量及其寄生蜂种类进行了调查.结果查得烟粉虱寄生蜂共7种,它们是恩蚜小蜂属Encarsm Forster的浅黄恩蚜小蜂En.sophia、日本恩蚜小蜂En.japonica、丽蚜小蜂En.formosa、黄盾恩蚜小蜂En.smithi和桨角蚜小蜂属Eretmocerus Haldeman的蒙氏桨角蚜小蜂Er.mundus、狄氏桨角蚜小蜂Er.debachi、盾黑桨角蚜小蜂Er.melanoscutus,其中优势种为浅黄恩蚜小蜂En.sophia、蒙氏桨角蚜小蜂Er.mundus和狄氏桨角蚜小蜂Er.debachi,这3种寄生蜂分别占收集到寄生蜂总数量的35.89%、49.66%和11.01%;此外,田间十字花科蔬菜上的烟粉虱虫13数量最高峰在2007年12月,自然寄生率最高峰在2008年10月,寄生率可达到13.86%;田间黄瓜上的烟粉虱虫口数量最高峰出现在2007年11月,自然寄生率最高峰在2007年8月,寄生率可达到8.22%;田间茄子上的烟粉虱虫口数量高峰出现在2007年7月和9月及2008年10月,自然寄生率高峰出现在2007年7月和9月及2008年9月,分别达到13.25%,10.30%和5.92%.     

内共生菌Wolbachia在蓖麻粉虱内的分布

【目的】在粉虱类害虫生物防治的载体植物系统中,蓖麻粉虱Trialeurodesricini是较好的替代寄主。Wolbachia是节肢动物中分布最广的细胞内共生菌,对昆虫的生殖和发育具有重要影响,明确蓖麻粉虱中Wolbachia的分布可为蓖麻粉虱Wolbachia的深入研究奠定基础,为粉虱类害虫的生物防治提供新的理论依据和思路。【方法】通过内共生菌Wolbachia的wsp基因A大组和B大组特异性引物对蓖麻粉虱的室内饲养种群及蓖麻粉虱与丽蚜小蜂同笼饲养20代的种群逐代进行PCR检测,对扩增到的基因进行测序并构建系统发育树,进行相关分析。【结果】蓖麻粉虱种群中只有A大组Wolbachia分布,感染率为40%,系统发育分析表明该类群的Wolbachia属于A大组中的Dro亚组,与报道的其他寄生蜂种群感染的Wolbachia同属一组。丽蚜小蜂种群中的Wolbachia属B大组,蓖麻粉虱与丽蚜小蜂混合饲养20代,逐代检测发现Wolbachia并未在蓖麻粉虱与丽蚜小蜂种群间发生水平传播。【结论】蓖麻粉虱的室内饲养种群中Wolbachia的感染率仅为40%,说明Wolbachia能够在蓖麻粉虱种群中稳定遗传,但在蓖麻粉虱个体间水平传播的能力较弱。短时间内Wolbachia无法在蓖麻粉虱与丽蚜小蜂种群间水平传播。     

基于SCAR标记技术的丽蚜小蜂快速识别

丽蚜小蜂Encarsia formosa Gahan作为温室粉虱Trialeurodes vaporariorum Westwood和烟粉虱Bemisia tabaci (Gennadius)等粉虱类害虫的优势寄生蜂而备受关注。针对丽蚜小蜂体型微小, 难以与其他同域近缘种寄生蜂快速、 准确区别的问题, 本研究采用SCAR (sequence characterized amplified region, 特异性扩增区域)标记技术, 筛选出一对丽蚜小蜂特征片段扩增引物(EFZZF/EFZZR), 其扩增片段的大小为287 bp。种特异性检验结果表明, 该对引物只对丽蚜小蜂的基因组DNA具有扩增能力, 对其近缘种属寄生蜂如浅黄恩蚜小蜂Encarsia sophia (Girault & Dodd)、 海氏桨角蚜小蜂Eretmocerus hayati Zolnerowich & Rose、 本地未知种桨角蚜小蜂Eretmocerus sp.、 蒙氏桨角蚜小蜂Eretmocerus mundus Mercet、 刺粉虱黑蜂Amitus hesperidum Silvertri不具有扩增效果, 对丽蚜小蜂的寄主包括不同生物型 (B型、 Q型、 ZHJ 1型和ZHJ 2型)的烟粉虱、 温室粉虱以及我国最常见的黑刺粉虱Aleurocanthus spiniferus (Quaintanca)等亦不具有扩增能力。同时, 该检测技术灵敏度高, 对成虫的最低检出阈值为7.812 ng/μL (相当于1/1 600头成虫)。研究结果对丽蚜小蜂的种类识别、 寄主谱的确定及其有效利用具有重要意义。     

大棚微生境下两种烟粉虱寄生蜂的竞争作用

海氏桨角蚜小蜂和丽蚜小蜂是烟粉虱的重要天敌,为更有效地发挥其控害作用,在大棚条件下评估了这两种寄生蜂在种内及种间竞争时对单雌寄生率及对烟粉虱的控害潜能的影响。结果显示:种间竞争导致丽蚜小蜂的单雌寄生率显著降低,而对海氏桨角蚜小蜂无显著影响,种内竞争对两种寄生蜂的单雌寄生率均无显著影响。与单头蜂对烟粉虱的致死率比较,两头蜂在夹叶笼内对烟粉虱的致死率无显著差异,表明两种蜂的种内和种间竞争作用对寄生蜂的控害潜能有干扰作用。     

两种蚜小蜂对烟粉虱寄主的产卵选择性(英文)

双斑恩蚜小蜂和桨角蚜小蜂是华南地区烟粉虱的两种优势种寄生蜂。本文研究了两种寄生蜂对不同龄期烟粉虱寄主的产卵选择特性。结果表明:两种寄生蜂均可寄生烟粉虱的1~4龄若虫。当只有1个龄期的烟粉虱若虫存在时,双斑恩蚜小蜂更多地寄生3龄和4龄若虫,较少寄生1龄和2龄若虫;而桨角蚜小蜂则更多地寄生3龄和2龄若虫,较少寄生1龄和4龄若虫。在4个龄期若虫同时存在时,双斑恩蚜小蜂会明显增加对3龄和4龄若虫的产卵寄生,降低对1龄和2龄若虫的寄生;而桨角蚜小蜂则增加对2龄和3龄若虫的寄生,减少对1龄和4龄若虫的寄生。寄主植物的差异不影响这二种蚜小蜂对各龄期烟粉虱若虫的产卵选择倾向。结果提示,烟粉虱若虫3龄和4龄是双斑恩蚜小蜂最适宜的寄主,而桨角蚜小蜂最适宜的寄主是烟粉虱2龄和3龄若虫。     

两种蚜小蜂对烟粉虱寄主的产卵选择性（英文）

双斑恩蚜小蜂和桨角蚜小蜂是华南地区烟粉虱的两种优势种寄生蜂。本文研究了两种寄生蜂对不同龄期烟粉虱寄主的产卵选择特性。结果表明: 两种寄生蜂均可寄生烟粉虱的1～4龄若虫。当只有1个龄期的烟粉虱若虫存在时,双斑恩蚜小蜂更多地寄生3龄和4龄若虫,较少寄生1龄和2龄若虫;而桨角蚜小蜂则更多地寄生3龄和2龄若虫,较少寄生1龄和4龄若虫。在4个龄期若虫同时存在时,双斑恩蚜小蜂会明显增加对3龄和4龄若虫的产卵寄生,降低对1龄和2龄若虫的寄生;而桨角蚜小蜂则增加对2龄和3龄若虫的寄生,减少对1龄和4龄若虫的寄生。寄主植物的差异不影响这二种蚜小蜂对各龄期烟粉虱若虫的产卵选择倾向。结果提示,烟粉虱若虫3龄和4龄是双斑恩蚜小蜂最适宜的寄主,而桨角蚜小蜂最适宜的寄主是烟粉虱2龄和3龄若虫。     

甘桔新害虫——高氏瘤粉虱研究

高氏瘤粉氨Aleurotubercutus takahashii David et Subramaniam是福建福州郊区桔园新发现的一种小型刺吸性害虫。国外在印度最早发现,并于1976年被鉴定命名。本通过该虫在替换寄主茉莉花上的田间调查和室内饲养观察,对该虫的形态特征、生物学特性及防治对策作了初步探讨。高氏瘤粉虱在福州年发生约8～9代,主要以成虫、若虫刺吸为害柑桔和莱莉叶片,在28±1℃条件下,世代历期为26-31天。以高龄若虫或拟蛹越冬。其寄生性天敌有桨角蚜小蜂(Eretmocerus sp．)、恩蚜小蜂(Encarsia sp.)等,寄生率为7．07-17．84%。     

茶园黑刺粉虱自然种群生命表

1989年黑刺粉虱Aleurocanthus spiniferus在我国茶区大发生。在皖南茶区选常年虫情较重的茶园,每5天1次系统地调查了全年各个世代各虫态的种群波动及其与气候因子的关系,及茶园生境、品种间虫口密度的差异,连续研究了3个世代的自然种群生命表,分析了粉虱种群暴发至衰退过程中各种致死因子的作用。2002年轻发生,又调查了种群数量与天气的关系。经轻、重发生年份的比较分析认为,该粉虱趋荫湿郁闭的茶丛中下层,1988年越冬代蛹的累积基数较大,越冬期间天气稍温暖干燥,死亡率较低。1989年春温暖湿润宜于化蛹、羽化和第1代卵的孵化而暴发。至第1代蛹期,寄生蜂的控制作用显著增强,羽化的成蜂紧接着寄生第2代粉虱的1、2龄幼虫。自第2代3龄幼虫起,长时期阴雨、高湿,几种虫生真菌在粉虱种群中酿成流行病。第1～3代粉虱种群趋势指数分别为0．47、0．09和0．02,种群数量逐代锐藏,于8月下旬崩溃。经关键因子分析认为,10余种寄生蜂的寄生和4种虫生真菌的侵染为重要制约因子。斯氏寡节蚜小蜂Prospaltella smithi、刺粉虱黑蜂Amitus hesperidum、蚧侧链孢Pleurodesmospora coccora、枝孢霉Cladosporium sp．、顶孢霉Acremonium sp．和韦伯虫座孢Aegerita webberi是优势种天敌。     

A fly larva (Syrphidae: Ocyptamus) that preys on adult flies

Predatory syrphid larvae feed on relatively immobile prey, but here we report the first case (as far as we are aware) of obligatory predation on very mobile prey. Larvae of an undescribed species of Ocyptamus (Diptera: Syrphidae) were found in whitefly (Hemiptera: Aleyrodidae) aggregations on the undersides of citrus leaves. However, instead of preying on the whitefly nymphs (as would be expected), the larvae preyed on adult flies (Diptera) that were attracted to the honeydew. In the laboratory, larvae captured significantly more flies on whitefly infested leaves than on washed leaves, and generally abandoned leaves that lacked whiteflies. Most cases of successful prey capture involved flies that probed the anterior part of the larva's body with its proboscis (as if it were honeydew). The syrphid larva lashed out at the fly and entangled it in sticky oral secretion. The prey did not recover when they were removed from the larva, suggesting that this new predatory species also employs venom to subdue its prey. Although the larvae consumed some honeydew, they were unable to complete their development on this diet. Two parasitoids were reared from Ocyptamus puparia, Proaspicera sp. (Hymenoptera: Figitidae) and Paracarotomus sp. (Hymenoptera: Pteromalidae), both of which are endoparasitic koinobionts.     

Population suppression of Bemisia tabaci (Hemiptera: Aleyrodidae) using yellow sticky traps and Eretmocerus nr. rajasthanicus (Hymenoptera: Aphelinidae) on tomato plants in greenhouses

We conducted three experiments for management of Bemisia tabaci (Gennadius) biotype ‘B’ on tomatoes under greenhouse conditions: (i) vertically placing yellow sticky cards either parallel or perpendicular to tomato rows at a rate of 1 per 3‐m row; (ii) releasing Eretmocerus sp. nr. rajasthanicus once at 30 adults/m² in the high whitefly density greenhouses (> 10 adults/plant), or twice at 15 adults/m² at a 5‐day interval in the low whitefly density greenhouses (< 10 adults/plant); and (iii) using combinations of yellow sticky cards that were placed vertically parallel to tomato rows and parasitoids released once at 30/m² in high whitefly density greenhouses or twice at 15/m² at a 5‐day interval in low whitefly density greenhouses. Our data show that yellow sticky cards trapped B. tabaci adults and significantly reduced whitefly populations on tomato. The yellow sticky cards that were placed parallel to tomato rows caught significantly more whitefly adults than those placed perpendicular to tomato rows on every sampling date. In the treatment where parasitoids were released once at 30/m² in high whitefly density greenhouses, the number of live whitefly nymphs were reduced from 4.6/leaf to 2.9/leaf in 40 days as compared with those on untreated plants on which live whitefly nymphs increased from 4.4/leaf to 8.9/leaf. In the treatment where parasitoids were released twice at 15/m² in low whitefly density greenhouses, the numbers of live nymphs of B. tabaci on tomato leaves were reduced from 2.1/leaf to 1.7/leaf in 20 days as compared with those on untreated plants on which numbers of live nymphs of B. tabaci increased from 2.2/leaf to 4.5/leaf. In the treatment of yellow sticky cards and parasitoid release once at 30/m² in high whitefly density greenhouses, the numbers of live nymphs of B. tabaci on tomato leaves were reduced from 7.2/leaf to 1.9/leaf, and in the treatment of yellow sticky cards and parasitoid release twice at 15/m² at a 5‐day interval at low whitefly density, the numbers of live nymphs of B. tabaci on tomato leaves were reduced from 2.5/leaf to 0.8/leaf; whereas the numbers of live nymphs of B. tabaci on untreated plants increased from 4.4/leaf to 8.9/leaf. An integrated program for management of B. tabaci on greenhouse vegetables by using yellow sticky cards, parasitoids and biorational insecticides is discussed.     

Population dynamics of Bemisia tabaci (Homoptera: Aleyrodidae) parasitoids on cassava mosaic disease–resistant and susceptible varieties

Three field trials were conducted at Namulonge Agricultural and Animal Production Research Institute to investigate the population dynamics of Bemisia tabaci Gennadius and its associated aphelinid parasitoids in Uganda. Results showed that more whitefly occurred on the cassava mosaic disease-resistant variety, (Nase 4) compared to the susceptible variety, (Ebwanatereka). Two species of aphelinid parasitoids, Eretmocerus mundus Mercet and Encarsia sophia Girault and Dodd, were identified during the study. Overall percent parasitism did not differ significantly (P>0.05) between varieties in all the trials, but significant differences occurred at 13, 15 and 21 weeks after planting during late season (2000), 18 weeks after planting during early season (2001), and 8 weeks after planting during late season (2001). The trends in the build up in numbers of both parasitoids species and apparent parasitism were similar, differed significantly on certain dates. It was, however, noted that percent parasitism decreased with nymph number. The significance of this phenomenon on the potential use of these aphelinid parasitoids as biocontrol agents of the cassava whitefly is discussed.     

烟粉虱及海氏桨角蚜小蜂对中国番茄黄化曲叶病毒感染烟草的嗅觉反应

双生病毒可通过调控寄主植物促进媒介昆虫烟粉虱种群增长,然而病毒侵染植物后是否通过调控植物挥发物来影响烟粉虱及其天敌的嗅觉反应还未见报道。【目的】本文旨在研究烟草植株感染中国番茄黄化曲叶病毒(Tomato yellow leaf curl China virus,TYLCCNV)后对烟粉虱Bemisia tabaci(Gennadius)及其重要寄生性天敌海氏桨角蚜小蜂Eretmocerus hayati(Zolnerowich and Rose)嗅觉反应行为的影响。【方法】利用Y形嗅觉仪方法,我们测试了烟粉虱及海氏桨角蚜小蜂对带毒植株、健康植株及烟粉虱危害植株的选择偏好性。【结果】烟粉虱及海氏桨角蚜小蜂选择携带TYLCCNV病毒的烟草显著多于健康烟草植株,但烟草被病毒与烟粉虱共同侵染时,烟粉虱对带毒烟草的选择仍显著多于无毒植株,而寄生蜂虽然仍较多选择带毒植株,但无显著差异。【结论】这些结果表明烟粉虱及海氏桨角蚜小蜂偏好选择携带TYLCCNV病毒的烟草,但这种偏好作用在烟粉虱取食共同危害时有一定程度的减弱。本研究首次报道了双生病毒侵染植物可增加烟粉虱及其天敌对植物的选择作用,并就其功能及机制进行了讨论。     

Population dynamics of Siphoninus philyreae in California in the presence and absence of a parasitoid, Encarsia partenopea

Abstract. 1. Densities of the whitefly, Siphoninus phillyreae Haliday, remained at low levels at two sites where a parasitoid, Encarsia parknopea (Walker), was released on whitefly-infested ash, Fraxinus sp., and pomegranate, Punica granatum. Populations of S.phillyreae at control sites, where parasitoids were absent, were increasing in density at the beginning of the summer.
2. By mid-summer, E.partenopea had appeared at all four control sites, and densities of S.phillyreae declined to levels similar to those at the release sites.
3. In the absence of the parasitoid, the age structure of S.phillyreae populations was dominated by the egg stage, indicating a population increasing in density. After E.partenopea became abundant at a site, the age structure of the population had a decreasing proportion of young stages.
4. The changes in S.phillyreae age structures were explained by examining the percentage of fourth instar S.phillyreae from which E.partenopea , as opposed to adult whiteflies, emerged. After the parasitoid became abundant at a site, the majority of fourth instars produced parasitoids rather than whitefly adults. The result was that the adult S.phillyreae population declined, and few eggs were laid.
5. The dynamics of the interaction between E.partenopea and S.phillyreae were similar on ash and pomegranate.     

Fitness of Encarsia sophia (Hymenoptera: Aphelinidae) parasitizing Trialeurodes vaporariorum and Bemisia tabaci (Hemiptera: Aleyrodidae)

Abstract Fitness and efficacy of Encarsia sophia (Girault & Dodd) (Hymenoptera: Aphelinidae) as a biological control agent was compared on two species of whitefly (Hemiptera: Aleyrodidae) hosts, the relatively smaller sweetpotato whitefly, Bemisia tabaci (Gennadius) biotype ‘B’, and the larger greenhouse whitefly, Trialeurodes vaporariorum (Westwood). Significant differences were observed on green bean (Phaseolus vulgaris L.) in the laboratory at 27 ± 2°C, 55%± 5% RH, and a photoperiod of 14: 10 h (L: D). Adult parasitoids emerging from T. vaporariorum were larger than those emerging from B. tabaci, and almost all biological parameters of E. sophia parasitizing the larger host species were superior except for the developmental times of the parasitoids that were similar when parasitizing the two host species. Furthermore, parasitoids emerging from T. vaporariorum parasitized more of these hosts than did parasitoids emerging from B. tabaci. We conclude that E. sophia reared from larger hosts had better fitness than from smaller hosts. Those from either host also preferred the larger host for oviposition but were just as effective on smaller hosts. Therefore, larger hosts tended to produce better parasitoids than smaller hosts.     

Biocoenology and control of whiteflies in sericulture

Abstract The damage caused by the whiteflies Dialeuropora decempuncta (Quaintance & Baker, 1913), Aleurodicus dispersus Russell, and Aleuroclava sp. to mulberry plants is extensive and they cause a huge economic loss to mulberry leaves which affects silkworm rearing. Dialeuropora decempuncta is a major pest in western Bengal, whereas spiralling whitefly A. dispersus has been reported to attack mulberry plants in South India. The whiteflies are present throughout the year in south India, with high populations in summer (March—June) and low ones in winter (October—January). The population is positively correlated with temperature and negatively correlated with humidity. Chemical control is the quick solution to minimize the pest population. However, the indiscriminate and large-scale use of highly poisonous synthetic chemical pesticides has resulted in ecological imbalance, in addition to their toxic effects on living organisms, including human beings. Hence there is a need for developing methods and materials within an eco-friendly atmosphere. Previous investigations indicate that neem-based insecticides may be a suitable alternative for pest management in sericulture. Use of neem products in sericultural pest control has many merits. It will also help in the successful introduction of biological controls in India. Several exotic parasitoids have been found to be highly effective, including two aphelinid parasitoids Encarsia haitiensis Dozier and E. meritoria Gahan. These are most promising and are reported to minimize the fly pest population. The parasitization potential and behaviour of the parasitoids have to be carefully assessed before they are introduced to control fly pest populations. There is a need for careful assessment of all these advanced biological technologies in order to develop a profitable, safe and durable approach for whitefly control in sericulture.     

The natural enemies of Bemisia argentifolii in Martinique

An eight year survey wasconducted in Martinique on vegetable crops andweeds to develop a list of the natural enemiesof the whitefly Bemisia argentifoliiBellows and Perring. More than fifteen speciesof predators and parasitoids were found as wellas one entomopathogenic fungus (Paecilomyces sp.). The primary predators wereladybirds (Delphastus pusillus and D. pallidus) and bugs (Nesidiocoris tenuis, Macrolophus cf. caliginosus, Orius insidiosus). The mostcommon parasitoids were Eretmocerustejanus, Encarsia luteola, E. nigricephala, E. transvena and Amitus bennetti. Observations on the biologyand distribution of these natural enemies are provided.     

Parasitoid Mark-Release-Recapture Techniques-- II. Development and Application of a Protein Marking Technique for Eretmocerus spp., Parasitoids of Bemisia argentifolii

In this study, we validate and apply techniques for marking and capturing small parasitoids of the silverleaf whitefly, Bemisia argentifolii Bellows & Perring [ = B. tabaci (Gennadius), strain B] for mark-release-recapture (MRR) studies. The marker is the purified protein, rabbit immunoglobulin G (IgG), which was applied externally by topical spray or internally by feeding. Marked parasitoids were then assayed using a sandwich enzyme-linked immunosorbent assay (ELISA) for the presence of the protein marker using an antibody specific to rabbit IgG. Virtually all of the externally marked Eretmocerus sp. (Ethiopia, M96076) (98.0%) contained enough rabbit IgG to be easily distinguished from unmarked parasitoids, regardless of the amount of protein applied or the post-marking interval. A field MRR study was then conducted to examine the dispersal characteristics of E. emiratus Zolnerowich & Rose. Parasitoids marked externally and internally with protein were released on three separate trial dates into the center of a cotton field bordered by cantaloupe and okra. Overall, a total of 1388, 637, and 397 marked and unmarked wasps were captured in suction traps during each trial, respectively with the majority of parasitoids captured between 0600 and 0800 h. Furthermore, even though we released an equal proportion of males to females, our traps consistently contained more males. Our results suggest that there are gender-specific differences in the dispersal behavior of E. emiratus . Almost 40% of the captured parasitoids collected during the three release trials were positively identified for the presence of the protein marker. The distribution of the marked parasitoids revealed two distinct patterns. First, almost all of the marked parasitoids recaptured in the cotton plot were in suction traps at or adjacent to the     

杀虫剂对湿地松粉蚧种群及其天敌的影响

湿地松粉蚧是于1988年传入我国广东省的一种重要林业外来入侵害虫。现在该害虫在我国的分布面积为35.52万公顷,严重影响着我国南方松林的生长健康。该害虫在其原产地美国南方并不造成大的危害,也不是一种主要害虫。只有当大量应用杀虫剂防治其它害虫时,由于杀死了其天敌,湿地松粉蚧种群才会明显增长。为控制这一外来入侵害虫,中美两国于1995年开展了从美国引进天敌防治广东省湿地松粉蚧的林业合作项目。本文报道了1996～1997年间在美国南方三个种子园使用杀虫剂防治球果种实害虫时,杀虫剂对湿地松粉蚧种群及其两种主要天敌有明显的影响,这也间接地说明了寄生性天敌对湿地松粉蚧在自然条件下的控制作用。相关分析显示湿地松粉蚧种群数量与其天敌是密切相关的,但杀虫剂可以打破这种平衡。这一方面说明从美国引进天敌防治湿地松粉蚧是可行的,另一方面也显示在美国采集湿地松粉蚧天敌应在使用过杀虫剂后的林分中。