Predatory beetles in cacao agroforestry systems in Brazilian Atlantic forest: a test of the natural enemy hypothesis

The natural enemy hypothesis predicts a positive correlation between plant species diversity and natural enemy control. This study aimed to evaluate the role of traditional cacao agroforests, known as “cabrucas,” on the conservation of the predatory beetle community compared to that of monodominant rubber agroforests. Predatory beetles were sampled in three habitats in Southeastern Bahia, Brazil: cabrucas and rubber agroforests and native Atlantic forests. In each habitat, 18 10 m² plots were established, in which canopy cover was measured and beetles were sampled with a modified Malaise/window trap. Land use intensification did not affect the composition of predatory beetles, with the presence of widely distributed species that are also capable of colonizing simpler environments such as the rubber agroforest. Canopy cover had a positive effect on generalist predator diversity and we observed a reduction in the abundance and species richness of generalist predators with increasing habitat homogenization. Despite the simplified structure of the habitat, the remaining tree diversity and canopy cover in cabrucas supported a community of generalist predators similar to the one found in the native forest. Species diversity of bark beetle predators was higher in cabrucas, which may be due to the high diversity of bark beetles and the favorable abiotic conditions, whereas the low abundance of prey in the native forest and severe abiotic conditions in the rubber agroforest probably determined the lower diversity of generalist predators in these habitats. Cabrucas play an important role in the conservation, supporting a community of predatory beetles more similar to the one found in native forest and that is more effective at controlling populations of herbivores than in homogeneous rubber agroforests.     

枣园生态系统中主要害虫、天敌生态位及种间竞争的研究

对太谷地区枣园生态系统中主要害虫、天敌的时间、空间生态位及不同营养层物种间竞争进行了调查研究。结果表明，在利用相同资源的物种中，存在着程度不同的生态位重叠和种间竞争现象。枣园间作物(或杂草的有无)和用药与否对时间生态位的宽度有明显的影响，但对生态位重叠与种间竞争的大小以及空间生态位的宽度没有影响；明确了害虫与天敌在时间与空间序列上的分布变化规律，为枣树害虫的综合生态调控提供了科学依据。     

帽儿山地区金龟类访花甲虫的调查分析

通过对黑龙江帽儿山地区金龟类访花甲虫种类的初步调查,结果表明,访花金龟共有15种,其中花金龟科有7种(46.67%),丽金龟科5种(33.33%),斑金龟科2种(13.33%),鳃金龟科1种(6.67%);优势种3种:短毛花金龟、小青花金龟和白星花金龟。金龟类访花优势种,主要访问的植物种类有:珍珠梅、深山唐松草、柳叶绣线菊、鸡树条荚蒾、蚊子草等。并对金龟类访花甲虫对花的选择特征进行了总结。     

阿克苏地区不同核农问作系统节肢动物时序动态研究

对新疆阿克苏地区核桃与农作物间作系统节肢动物进行系统调查,摸清主要害虫的发生规律,为南疆地区核桃主要害虫的控制及果园规范化生产提供理论依据。运用群落生态学方法分析核农闭作系统节肢动物的时序动态,结果表明,四种类型核桃园中,全年多样性指数与均匀性指数结果期核桃＋棉花间作园最大,幼树龄核桃＋棉花间作园次之;而优势集中性指数则是结果期核桃＋棉花澡作园最低。在核桃与农作物间作时,核桃园建议选择闻作棉花。     

Abundance and diversity of soil invertebrates in annual crops, agroforestry and forest ecosystems in the Nilgiri biosphere reserve of Western Ghats, India

Biologically mediated soil processes rely on soil biota to provide vital ecosystem services in natural and managed ecosystems. However, land use changes continue to impact on assemblages of soil biota and the ecosystem services they provide. The objective of the present study was to assess the effect of land use intensification on the distribution and abundance of soil invertebrate communities in the Nilgiri, a human-dominated biosphere reserve of international importance. Soil invertebrates were sampled in 15 land use practices ranging from simple and intensively managed annual crop fields and monoculture tree plantations through less intensively managed agroforestry and pristine forest ecosystems. The lowest taxonomic richness was found in annual crops and coconut monoculture plantations, while the highest was in moist-deciduous and semi-evergreen forests. With 21 ant species, agroforestry systems had the highest diversity of ants followed by forest ecosystems (12 species). Earthworms and millipedes were significantly more abundant in agroforestry systems, plantations and forest ecosystems than in annual crop fields. Ants, termites, beetles, centipedes, crickets and spiders were more abundant in forest ecosystems than in other ecosystems. It is concluded that annual cropping systems have lower diversity and abundance of soil invertebrates than agroforestry and natural forest ecosystems. These results and the literature from other regions highlight the potential role that agroforestry practices can play in biodiversity conservation in an era of ever-increasing land use intensification and habitat loss.     

Insect pest problems in tropical agroforestry systems: Contributory factors and strategies for management

Agroforestry trees are attacked by a wide spectrum of insects at all stages of their growth just like other annual and perennial crops. Pest management in agroforestry has not received much attention so far, but recent emphasis on producing high value tree products in agroforestry and using improved germplasm in traditional systems, and emergence of serious pest problems in some promising agroforestry systems have increased awareness on risks posed by pests. Insects may attack one or more species within a system and across systems in the landscape, so pest management strategies should depend on the nature of the insect and magnitude of its damage. Although greater plant diversity in agroforestry is expected to increase beneficial arthropods, diversity by itself may not reduce pests. Introduction of tree germplasm from a narrow genetic base and intensive use of trees may lead to pest outbreaks. In simultaneous agroforestry systems, a number of factors governing tree—crop—environment interactions, such as diversity of plant species, host range of the pests, microclimate, spatial arrangement and tree management modify pest infestations by affecting populations of both herbivores and natural enemies. Trees also affect pest infestations by acting as barriers to movement of insects, masking the odours emitted by other components of the system and sheltering herbivores and natural enemies. In sequential agroforestry systems, it is mostly the soil-borne and diapausing insects that cause and perpetuate damage to the common hosts in tree—crop rotations over seasons or years. An integrated approach combining host-plant resistance to pests, exploiting alternative tree species, measures that prevent pest build up but favour natural enemies and biological control is suggested for managing pests in agroforestry. Species substitution to avoid pests is feasible only if trees are grown for ecological services such as soil conservation and low value products such as fuelwood, but not for trees yielding specific and high value products. For exploiting biological control as a potent, low cost and environmentally safe tool for pest management in agroforestry, research should focus on understanding the influence of ecological and management factors on the dynamics of insect pest-natural enemy populations. Scientists and policy makers in national and international institutions, and donors are urged to pay more attention to pest problems in agroforestry to harness the potential benefits of agroforestry.This revised version was published online in November 2005 with corrections to the Cover Date.     

Pests and diseases in agroforestry systems of the humid tropics

Few studies have included detailed investigations of the interactions of agroforestry techniques with pests and diseases, although the relevance of such interactions has long been recognized. The objectives of this review are to provide basic information on pests and diseases in tropical agroforestry systems and to develop concepts which can assist in the future in the systematic data collection and analysis in this field. The emphasis is on simultaneous agroforestry systems with annual and perennial crops, although rotational systems are also discussed. Crop rotation is an important pest and disease control strategy in annual cropping systems, and the principle of altering host with non-host plants can also be applied in improved fallow systems, provided that hosts of crop pests and diseases are avoided when selecting the fallow species. When annual cropping systems are transformed into simultaneous agroforestry, the control strategy of frequent disturbance of pest and disease populations is to some extent substituted for the strategy of increased stability and internal control mechanisms. However, reduced pest and disease risk is not automatically achieved by introducing perennial plants and increasing the plant diversity in a system. If plant species are introduced that harbor pests or diseases of other species in the system, the risk of pest and disease outbreaks may actually increase. For evaluating such risks, it is important to consider host-ranges of diseases on the pathovar instead of the species level. Beside the selection of compatible plant species, their spatial arrangement may be important for reducing the spread of pest and disease organisms through the system, although little information is available on such effects, and they may be largely irrelevant for organisms with efficient dispersal mechanisms such as wind-dispersed fungi. In addition to the species-specific, biological effects of plants on pests and diseases, their unspecific, physical effects can be of major relevance for pest and disease development as well as the susceptibility of the affected plant species. Increased pest and disease incidence has often been observed directly at the tree-crop interface, caused by the humid microclimate, physical protection of mammal and bird pests by the trees and eventually reduced pest and disease tolerance of competition-stressed crops. Linear tree plantings and hedgerows affect the wind transport of small insects and disease propagules, the active immigration and emigration of pest organisms as well as the populations of natural enemies. Similarly, overhead shade has a major effect on the micro-climatic conditions under which pest and disease organisms, their natural enemies and the crops themselves develop, and its optimization is a highly efficient control strategy for many pests and diseases. On infertile soils, the susceptibility of crops to pests and diseases is strongly affected by the availability of plant nutrients, which may be influenced by agroforestry techniques in various ways. Soil management measures such as mulching and planting cover crops may affect crop health by improving soil fertility and by directly acting on pest and disease populations. The importance of a more systematic collection of pest and disease related information for agroforestry, e.g., in a central database, and of the development of strategies for reducing pest and disease risks in agroforestry in cooperation with farmers is stressed.This revised version was published online in November 2005 with corrections to the Cover Date.     

Effect of ground cover management on Thysanoptera (thrips) in clementine mandarin orchards

Conservation biological control by means of ground cover offers an interesting alternative to chemical control. A complex of Thysanoptera (thrips) species inhabits citrus, some of which are considered pests. This study investigated the effect of ground cover management on thrips species composition, distribution, and seasonal abundance in four commercial clementine mandarin (Citrus clementina Tanaka) orchards. Three soil management systems were compared: resident vegetation, Festuca arundinacea Schreber (Poales: Poaceae), and bare soil. Cover management affected thrips species diversity and abundance. Two of the main species causing fruit damage in Spanish citrus, Frankliniella occidentalis (Pergande) and Thrips tabaci Lindeman, were abundant in the resident ground cover. However, their abundance was strongly depressed in the F. arundinacea cover. The resident vegetation cover could provide a range of suitable host plants supporting populations of potential thrips pest species beyond the citrus blooming period. The F. arundinacea cover, which hosted Poaceae-specific thrips species, could also provide alternative food sources for Phytoseiidae mites. These predatory mites could reduce populations of potential thrips and other citrus pests below economic injury level. Our results confirm the suitability of F. arundinacea as a cover crop for clementine mandarins.     

植物多样性在园林病虫害生态控制中的作用

通过探讨植物多样性与害虫、天敌发生的关系,提出以提高植物多样性为基础,采取多种生态控制措施,达到预防、控制园林病虫害的目的。     

A push–pull strategy to control aphids combines intercropping with semiochemical releases

Even if insect pest populations can be reduced by increasing plant diversity through intercropping, natural enemies are not always favored in such systems. Alternatively, semiochemical substances have been tested to enhance biological control, with inconsistent results. Combining both strategies can be an interesting way to maximize pest control. In this work, a 2-year setup involving wheat–pea strip intercropping combined with the release of E-β-farnesene (EBF) or methyl salicylate (MeSA) was tested as a push–pull strategy to simultaneously repel aphids and attract beneficials. Two types of slow-release formulation (i.e., oil and alginate beads) containing EBF or MeSA were deployed with the intercropping. The abundance of aphids was significantly decreased, while hoverfly larvae and mummified aphids increased on both pea plants and wheat tillers by the release of oil-formulated EBF and MeSA. The proportion parasitism of the aphid-parasitism rate [mummies/(aphids + mummies)] was also increased by treating both crops in both years. Releasing EBF through oil rather than alginate beads proved significantly better for attracting natural enemies and reducing aphids. Aphids were negatively correlated with the density of hoverflies (both adults and larvae) and numbers of mummies. All these results showed that combining intercropping with the release of EBF or MeSA formulated in oil can significantly reduce aphid density and attract their natural enemies. Therefore, the combination of both strategies could help farmers reduce the use of insecticides.     

Weeds,aphids, and specialist parasitoids and predators benefit differently from organic and conventional cropping of winter cereals

The aphid–natural enemy interaction in winter wheat fields constitutes a complex system that has been frequently studied because of its implication for biological control. However, not all of the aphids living in cereal fields are crop pests, as there are also aphids living on weeds that may serve as alternative hosts or prey for aphid parasitoids or predators. In this context, a concomitant survey of the plant and insect communities was conducted to understand how different plant communities affect the abundance and richness of aphids and the interactions with their natural enemies. The plant community was split into functional groups (grasses, legumes and forbs), and the aphid community was divided into feeding groups according to their host preferences (specialists in grasses or forbs). The grass aphids, which dominated the total aphid catches, responded positively to grass cover, which was particularly enhanced in the conventional fields. Conversely, the forb aphids, which mainly conditioned the total species richness of the aphids, were closely correlated with the local abundance of legumes. The system of cereal aphid-parasitoids was enhanced in the conventional fields, where the abundance of grasses was higher, whereas the legumes of the organic fields indirectly played a key role in enhancing the richness of the parasitoids and the abundance of predators. Our findings indicate that a bottom-up effect exists throughout the plant community, aphids, and aphidophagous insects and that plant community characteristics should be considered to better understand cereal aphid control.     

Effects of forest restoration treatments on the abundance of bark beetles in Norway spruce forests of southern Finland

Restoration of protected areas in boreal forests frequently includes creating substantial volumes of dead wood. While this benefits a wide range of dead wood dependent invertebrate species, some of these are regarded as forest pests. Therefore, the risk of elevated levels of tree mortality in surrounding commercial forests must be considered. In a large-scale field experiment in southern Finland, we studied the effects of restoration treatments on the abundance of bark beetles within and in the vicinity of restored areas, in particular focusing on Ips typographus and Pityogenes chalcographus. The treatments applied to managed Norway spruce forests were controlled burning and partial harvesting combined with retaining 5, 30 or 60 m³/ha of cut down wood. We found that the abundance of bark beetles increased by both burning and harvesting with down wood retention, being highest where burning and harvesting had been combined. The actual volume of down wood retention had no significant effect. The effect of burning on the number of bark beetles along host tree boles was negative which suggests that burnt spruces provided a less suitable resource for bark beetles than unburnt dead spruces. The abundance of bark beetles along host trees also decreased with increasing volume of down wood retention. The abundance of P. chalographus was slightly elevated up to 50 m outside restored areas but the abundance was very low compared to that within the areas. The abundance of I. typographus was extremely low outside restored areas. We conclude that restoration treatments increase the abundance of bark beetles via increased availability of resources, but that the effect of burning is likely to be counteracted by decreased resource quality. Thus, burning might be the “safest” way to produce large quantities of dead wood. Furthermore, the fact that only few beetles were collected in adjacent areas suggests that restored areas pose little threat of serving as refugia in which bark beetle populations increase in sufficient numbers to attack live trees in adjacent forests. However, restoration actions repeated at consecutive years within a small area might enable the populations to grow to outbreak levels.     

Host acceptance behavior of the parasitoid Aphelinus mali and its aphid-host Eriosoma lanigerum on two Rosaceae plant species

The presence of a natural enemy in a habitat refuge is no guarantee of emigration by these into crop fields, when pest population outbreaks occur. Parasitoids from a refuge may not prefer foraging on the pest crop, exhibiting host fidelity, and therefore not constituting a source of natural enemies for improving biological control. An effective refuge must not only be a suitable sink for natural enemies, providing an acceptable host when these are not present in the crop, but it must also be a suitable source of parasitoids that readily accept the aphid-host on the crop. Therefore, crop-originated parasitoids would have to accept pests from the refuge as hosts to lay eggs in, and refuge-originated parasitoids would have to accept and lay eggs in pests from the crop. We here study the host fidelity of populations of Eriosoma lanigerum originating from two host plants (firethorn and apple) through reciprocal transfer experiments. Thereafter, the host fidelity of parasitoids from populations in the two host plants (firethorn and apple) was assessed. Reciprocal transfer experiments of parasitoids did not show an association between apple-originated parasitoids and their preference for any of the aphid hosts. Conversely, parasitoids from firethorn exhibited a higher number of attacks and in less time when aphids from apple were offered, suggesting a preference for apple-originated aphids. If future field work confirms these findings, firethorn could become an important management tool for enhancing biological control of woolly apple aphid in apple orchards, without being a substantial source of aphids.     

红环瓢虫的生物学与应用技术研究进展

红环瓢虫是杨树人工林害虫——草履蚧的主要捕食性天敌,对控制害虫危害具有重要的利用价值。该文对其形态分类、生物学特性和应用技术等方面的研究进展作了较为系统的综述,并提出了利用红环瓢虫开展杨树人工林草履蚧可持续控制的对策。     

洞庭湖区杨树有害生物及天敌昆虫调查

2007—2009年,通过线路踏查,标准地详查,室内饲养昆虫,灯光诱捕昆虫,查阅相关资料等方法,对洞庭湖杨树主栽区进行了杨树有害生物及天敌昆虫普查,普查发现洞庭湖区危害杨树的有害昆虫共计8目36科146种,病害12种,有害动物5种,有害植物4种,主要天敌昆虫13种。     

太原市油松小蠹虫及其综合防控技术研究

小蠹虫是一类重要的森林害虫,多为次期性害虫。通过调查,在太原市为害油松的主要种类是松六齿小蠹、松八齿小蠹和松十二齿小蠹;成虫扬飞期分别出现在5月份、7月份、8月份、9月份,是防治的关键时期;引起小蠹虫成灾的原因除自然因素外,主要是人为因素,所以防控小蠹虫要以虫情测报为基础,以检疫和林木管护措施为主导,并辅以生物、人工、化学等综合防控措施。     

管理措施对毛竹林节肢动物群落害虫与天敌相互作用的影响

利用毛竹林节肢动物群落的系统调查资料,比较和分析长期垦复施肥、垦复、劈草、撂荒和化学除草5种管理措施下群落林下层和竹冠层的共有物种分布特征,以及害虫与天敌功能群的相互关系.结果表明:与撂荒林比较,其余管理措施因破坏了林下栖境而不同程度地减少了2个林层间的天敌共有物种,这些减少的共有物种多属于蜘蛛目和膜翅目天敌,从而削弱了林层间的天敌互补作用,不利于充分发挥其自然控害作用,是毛竹叶部害虫暴发的重要原因之一.因此,在各项管理措施实施时,适度保留部分林下植被,有助于竹林的丰产培育和强化群落的自然控害潜能.     

“三江源”隆务河流域天然林区小蠹区系初步研究

青海省"三江源"区隆务河流域天然林区有小蠹虫19种,危害青海云杉、紫果云杉、油松、祁连圆柏和桦树,以中亚细亚种占优势。小蠹种群的动态变化受气温、立地条件、林木生长势、林分卫生状况等因子的影响。以提高经营管理措施和信息素等生物防治为主,适时进行化学触杀剂防治为辅的方法是控制小蠹种群危害的较好途径。     

花椒的主要害虫及防治技术

介绍了影响山西省花椒产量和造成花椒树死亡的主要害虫种类，分析了它们的为害特点和发生规律。提出了加强树盘管理、推广整形修剪、做好虫情预测预报、发挥天敌优势、实施科学用药的综合治理措施。     

人工林物种多样性与害虫的控制

根据国内外的最新研究成果,从人工林害虫可持续控制的需求出发,对利用物种多样性与系统稳定性控制虫害的可能性、人工林物种多样性与害虫控制的关系及其内在作用机制、天然林与人工林在抑制虫害能力上的差别进行综述,分析人工林植物物种多样性与昆虫物种多样性对害虫控制的影响,认为植物物种多样性主要从植食性昆虫搜寻寄主植物,植物营养的差异对植食性昆虫取食和发育的影响,及种类组成不同的植物群落中植食性昆虫天敌数量的变化3个方面影响害虫的发生;要通过调节植物群落中昆虫物种的多样性影响目标害虫的种群数量,既要维护其天敌类群的稳定,也要使与害虫处于同一营养层次的其他植食性昆虫有足够的多样性,甚至也要保护和利用中性、中位及顶位昆虫.对人工林害虫的控制,可借鉴天然林自控虫害的原理,采用生态育林、封山育林及生物技术措施,逐步调整林分的结构,提高其物种多样性,增强林分自身的抗虫能力.