寄生蜂低温贮藏研究进展

天敌昆虫大量释放的首要前提是在一定时间内积累足够数量的产品,因此天敌昆虫的规模化生产和田间释放一直都是害虫生物防治应用中的关键性环节。与杀虫剂不同,大多数天敌昆虫的贮藏时间一般较短,而且在大面积释放之前要进行数量储备,因此研究一种理想的贮藏方法以降低生物防治成本是非常重要的。低温可以诱导和延缓昆虫的发育进程,因此在低温下贮藏天敌昆虫不仅有利于延长其贮藏时间,为生物防治提供稳定、充足的种群数量,而且还能根据害虫的发生危害规律进行贮藏期调控,继而实现田间同步释放。寄生蜂是生物防治领域内研究历史最长、应用范围最广的类群之一,关于寄生蜂低温贮藏的研究已经开展了大量工作,并积累了丰富的文献资料。作者综合分析了国内外近80年来关于寄生蜂低温贮藏的研究成果,对影响寄生蜂低温贮藏耐受性的一系列生物因素(营养、能量贮存、年龄/龄期等)和非生物因素(温度、湿度、光周期等)进行了阐述,并分析了这些因素的功能及其对于成功低温贮藏的重要作用,从而为寄生蜂低温贮藏提供了较为全面的考虑因素。低温在诱导寄生蜂贮藏时间延长的同时,也会对其适合度产生一定程度的不利影响。长期低温暴露导致的致死或者亚致死效应对寄主和寄生蜂都会产生显著影响。低温伤害累积能直接影响昆虫体内许多生理过程和组织结构,低温下虫体会消耗大量能量,与其他昆虫一样,低温贮藏中寄生蜂能量的消耗(特别是脂肪)是以其存活或者生殖为代价的,要维持营养生长和生殖生长之间的能量平衡,而脂肪含量对维持这种平衡有着非常重要的作用,尤其是寄生蜂不能合成脂肪。低温贮藏时冷伤害效应有时不会立即出现,可能会传递到下一个发育阶段或者后代,对寄生蜂的存活、发育或生殖产生不利影响。除了低温贮藏中一些变化明显的适合度特征(存活率、寿命、生殖力和性比)外,作者还综述了其他一些重要的适合度特征(飞行扩散能力、寄生和交配行为、世代交叉效应等),这些特征不仅对贮藏后寄生蜂的品质评价非常重要,还会影响其用于生物防治的效果。一种理想的贮藏方法最终还是决定于田间的实际应用效果,但是很少有研究通过调查田间实际效果来评价寄生蜂低温贮藏后的品质。随着生物防治产业的需求和快速发展,低温贮藏方法(长期或短期)的创新会降低以天敌昆虫应用为主的生物防治成本,使应用更加简单、经济。

Progress in Research of Cold Storage of Insect Parasitoids

Mass production of beneficial insects has long been considered necessary for biological control programs, especially those based on augmentative releases. The major obstacle to the successful implementation of inundative releases is the difficulty and cost of rearing beneficial insects in large numbers for mass release at appropriate time. Unlike pesticides, most insects used in biological control programs have a relatively short shelf-life, so they must be produced shortly before they are used. The development of efficient storage methods can reduce the cost of biological control by spreading the production period over several months. Storage at low temperature has proved to be a valuable method for increasing the shelf-life of natural enemies such as insect parasitoids and to provide a steady and sufficient supply of insects for biological control programs. Cold storage also allows synchronized field releases of natural enemies during the critical stages of pest outbreaks. Insect parasitoids are used extensively in biological control programs. Because of their scientific and economic interest, there is a large literature dealing with the studies on cold storage of parasitoids. The present review focuses on research progress about cold storage in parasitoids for recent eighty years at home and abroad. The complex network of abiotic factors (such as temperature, humidity and photoperiod) and biotic factors (such as nutrition, energy storage and age/stage) affecting the phenotypic plasticity in cold storage tolerance was summarized this paper. Knowing the diversity of factors that cause post-storage effects is essential for a successful implementation of cold storage. This review provides a comprehensive list of documented factors that must be taken into account when designing cold storage protocols. The cold-induced extension of parasitoids shelf life is generally associated with major fitness costs. Both the host and the parasitoid are affected by prolonged exposure to cold resulting in lethal or sub-lethal consequences. Low temperature also induces depletion of energy reserves and chilling injuries accumulate following various physiological dysfunctions. There is therefore, in parasitoids as in other insects, a trade-off between survival and reproduction and fat reserves play a central role in the physiology of resource allocation for this trade-off, especially so in parasitoids that are unable to synthesize lipids de novo. The consumption of energy reserves, particularly lipids, during cold exposure is thus expected to translate into fitness cost on survival and/or reproduction. The effect of a stress such as cold storage might not be immediately detectable, but might carry over to another stage, negatively influencing either development, fecundity, survival. Even if parasitoids remain alive after cold storage, a reduction of fitness-related traits may be observed directly, later in development or even in the next generation. In addition to the obvious fitness indicators such as emergence, longevity, fecundity and sex ratio, many other important fitness traits might be affected by storage and therefore impact the effectiveness of biological control. For instance, dispersal ability, parasite and mating behaviors or intergenerational effects are important features to be included in post storage quality assessment. Ultimately, the success of a storage method depends on conservation of field performance. Unfortunately, there are very few studies that assessed post-storage performances through field survey. Augmentative biological control is likely to grow rapidly because of the increasing demand from farmers, who are progressively moving away from chemical pesticide use. Innovations in cold storage methods (short or long-term) may lead to a reduction of cost for biological control, thereby making it easier and more economical to apply.