Invasion and Displacement of Experimental Populations of a Conventional Parasitoid by a Heteronomous Hyperparasitoid

Aphelinid parasitoids have an outstanding record of success in programmes of classical biocontrol against whiteflies and scale insects. Heteronomous hyperparasitoids are aphelinids in which the sexes develop on or in different hosts. The female always develops as a primary endoparasitoid of Homoptera. The male develops as a secondary parasitoid hyperparasitoid of his own or another species of homopteran endoparasitoid. Caged experiments were performed with the cabbage whitefly, Aleyrodes proletella, to examine the invasion of a population of a conventional parasitoid, Encarsia inaron both sexes primary endoparasitoids by a heteronomous hyperparasitoid, E. tricolor. In all cages the heteronomous hyperparasitoid successfully invaded an established population of the conventional parasitoid and the conventional species population declined to very low levels within 8 weeks of the introduction of the heteronomous hyperparasitoid. The patterns of invasion were different in each cage. In two cages, high levels of male production by E. tricolor were observed, indicating that hyperparasitism of the conventional species was probably an important factor in causing the decline in the E. inaron population. In a reciprocal experiment in which E. inaron was introduced to an established population of E. tricolor the conventional species failed to invade or persist. A survey of published references to complexes of parasitoids containing a heteronomous hyperparasitoid and one or more conventional species indicated that, in the majority of cases, the heteronomous hyperparasitoid was the most important species in the complex. There are clear implications for the use of these parasitoids in programmes of classical biocontrol. This is because high competitive ability against other parasitoids is not necessarily a good indicator of the ability of a species to maintain high levels of pest control, especially when hyperparasitic behaviour is involved.     

Production, Survival and Evaluation of Liquid Culture-produced Inocula of Coniothyrium minitans Against Sclerotinia sclerotiorum

Growth of Coniothyrium minitans on potato dextrose broth was compared with that on an inexpensive molasses-yeast liquid medium at 18-22°C in static culture. Biomass and conidial production were, in general, similar, although the rate of biomass production was quicker and conidial production was slightly greater per unit volume of medium in the molasses-yeast medium. Air-dried biomass from molasses-yeast liquid culture containing mycelia, pycnidia and conidia of C. minitans was mixed (12%, w/w) with kaolin to give a kaolin-biomass dust. The ability of C. minitans to survive and subsequently infect and reduce the viability of sclerotia of Sclerotinia sclerotiorum from this kaolin-biomass dust was found to be little affected by storage for 48 weeks between 4 and 15°C but was decreased by higher storage temperatures. The kaolin-biomass dust preparation did not differ from a standard maizemeal-perlite inoculum of C. minitans in its ability to infect sclerotia of S. sclerotiorum or reduce their viability or carpogenic germination in glasshouse and field pot bioassays. Further, when either inoculum was applied once to glasshouse soil naturally infested with S. sclerotiorum prior to planting three successive crops of lettuce, the pattern of disease control, reduction of sclerotial numbers/ plot, infection of sclerotia, reduction of sclerotial viability and survival in soil were similar for both inocula. The potential for the commercial development of liquid-culture-produced inocula of C. minitans is discussed.     

Mandible Form Relative to the Main Food Type in Ladybirds (Coleoptera: Coccinellidae)

The Coccinellidae is an economically important family within the Coleoptera. Some members are phytophagous pests, but many are beneficial predators and valuable biocontrol agents. This study investigates the morphology of the mandibles of adult Coccinellidae in relation to diet. Using scanning electron microscopy on 86 species of Coccinellidae, it was found that the morphology of the mandibles was dictated by the general feeding method, and could only be used to indicate a phytophagous, mycophagous or carnivorous diet. Phytophagous Coccinellidae of the subfamily Epilachninae had mandibles with denticulate apical teeth and setae for feeding on leaf material. The mandibles of the mycophagous Psylloborini had secondary teeth on the ventral apical tooth for collecting fungal spores. The mandibles of carnivorous Coccinellidae and Scymninae had either a bifid or unidentate apex. The unidentate mandible seemed to be restricted to coccidophagous species. Many species also had a mandibular groove along which prey body juices were conducted. Although mandible morphology could be related to the overall feeding method, there was no relationship between specific diet or food taxon and mandible shape. Mandible shape does not appear to be especially restricting for changes in diet either in the ecological sense or over evolutionary time. Mandible morphology is of limited use in determining diet and host specificity in Coccinellidae that are being selected as potential biocontrol agents.     

Bacterial Antagonists of Aspergillus flavus

In order to search for bacteria capable of reducing the aflatoxin contamination of cottonseed, 892 indigenous bacterial isolates, including 11 that were endophytic to cotton, were screened for their ability to inhibit the growth of Aspergillus flavus on cottonseed in an in vitro bioassay. Only six isolates partially or totally inhibited fungal growth. All antagonistic isolates were recovered from boll, lint or seed surface or from the lint of mature bolls. One was retrieved from mature seeds. None of the endophytic isolates showed activity. In four field trials, the incidence of A. flavus -induced damage to locules inoculated simulteously with A. flavus plus the most A. flavus plus the most effective antagonistic isolate (D1) was reduced by 41-100% relative to locules inoculated with A. flavus alone. The severity of damage to locules inoculated simultaneously with A. flavus and with D1 was reduced by 60-l00% relative to locules inoculated with A. flavus alone. Isolate D1, identified as Pseudomonas cepacia, completely inhibited the growth of A. flavus on synthetic media.     

Relationship of Heliothis zea predators, parasitoids and entomopathogens to canopy development in soybean as affected by Heterodera glycines and weeds

The influence of canopy development in soybean on the survival of corn earworm, Heliothis zea (Boddie) (Lepidoptera: Noctuidae), egg and larval stages and population dynamics of arthropod fauna were evaluated in field trials during 1986–88 in eastern North Carolina. Soybean canopy size decreased as soybean cyst nematode, Heterodera glycines Ichinohe (Nematoda: Heteroderidae), initial population densities increased. Plant species composition of the soybean canopy was affected by weed population densities. Mortality of H. zea larvae due to parasitism and infection with entomopathogens was greater in closed canopy and (or) weedy soybeans than in very open and (or) weed free soybeans. Predation and parasitism of corn earworm eggs were similar across nematode and weed density treatments. Natural enemy populations increased to highest levels during July in closed canopy and (or) weedy soybeans, coinciding with availability of largest prey population reservoirs. A delay in colonization of very open and (or) weed free soybeans by beneficial arthropods until mid to late August allowed greater H. zea larval survival than in closed canopy and (or) weedy soybeans. Arthropod species richness was generally greatest in closed canopy and (or) weedy soybeans during mid to late July, with differences becoming nonsignificant in August and early September. Mean and maximum ambient temperatures were higher and relative humidities lower in open canopy than in closed canopy plots. These conditions were less favorable for development of pathogens and natural enemies.     

A contribution to the biology ofBangasternus fausti [Col.: Curculionidae], a potential biological control agent of diffuse knapweed,Centaurea diffusa,and its effect on the host plant

The biology of the weevilBangasternus fausti (Reitter), the larvae of which live in the flowerheads ofCentaurea diffusa (De Lamarck) and some relatedCentaurea spp., was studied in the field and in the laboratory in northern Greece and in the laboratory in Rome, Italy. The species is univoltine and overwinters as adults. Under laboratory conditions adults lived up to 90 days and up to 359 eggs were deposited by a single female (n=18). The maximum number of eggs laid by a female per day was 12 and the maximum number of days a female laid eggs was 73. Generally, there is only one larva per seedhead. One-hundred percent seed destruction was recorded in 18.7% of 502 field collected seedheads, each with oneB. fausti egg. The average mortality of the species, from egg to adult, was 94.4% in the field during 1988 (n=200) and 95.8% during 1987 (n=502).      

铜绿假单胞菌生防菌株抑菌代谢产物及其生防应用研究进展

微生物次生代谢产物的研究对开发微生物源农药具有重要意义。近年来一系列根际来源的铜绿假单胞菌被分离和鉴定,因其产生抑菌次生代谢产物,具有很好的生物防治效果。本文将系统综述铜绿假单胞菌生防菌株的种类及其抑菌代谢产物的多样性,并进一步介绍铜绿假单胞菌生防菌株的抑菌代谢产物合成机制及其遗传改造,简要讨论铜绿假单胞菌生防菌株抑菌代谢产物在生物防治上的应用和前景。     

中国虫草一新记录种

【目的】对一个寄生鳞翅目幼虫的虫草标本Dxhir140901进行分类鉴定。【方法】采用形态学比较和基于ITS1-5.8S-ITS2rDNA的系统发育与进化网络分析进行鉴定。【结果】形态学观察：标本的分离菌株形态显示其为典型的被毛孢属真菌,具有两型产孢结构：A型产孢细胞柱状,(1.8?6.3) μm×1.8 μm;B型产孢细胞锥形,基部柱状,向上逐渐变细无明显颈部,基部宽3?3.8 μm,长21?63 μm,颈部宽1.8?2.0 μm,菌丝末端可直接形成产孢细胞;孢子橘瓣形或卵形,(8.1?10.8) μm×(2.7?5.4) μm,具粘液,黏液层厚1.8?2.7 μm。系统发育分析结果显示该菌株与巨针线形虫草Ophiocordyceps macroacicularis聚为一支,支持率为98%,进化网络分析也支持上述结果。【结论】通过与O. macroacicularis的形态比较和分子系统学分析结果,Dxhir140901及其分离株Gzuifr-hir140901为巨针线形虫草Ophiocordyceps macroacicularis S. Ban, T. Sakane & Nakagiri的无性阶段,该种为中国新记录种。     

生防真菌基因标记技术研究进展

生防真菌在环境中的检测是生物防治研究中的一个重要问题,基因标记是检测生防真菌的一种新技术。概述基因标记的概念、基因标记的载体质粒和标记基因、基因标记的方法及其在生防真菌中的应用情况。     

Interaction of endophytic diazotrophic bacteria and Fusarium oxysporum f. sp. cubense on plantlets of banana ‘Maça’

The objective of this work was to evaluate the effect of endophytic diazotrophic bacteria Herbaspirillum and Burkholderia on the Fusarium oxysporum f. sp. cubense (Foc) establishment and on the plantlets growth of the ‘Maçã’ banana (Musa spp., group ABB). Two assays were carried out in a greenhouse at the National Center of Tropical Agroindustry in Fortaleza city, Ceará State (Brazil), using randomized block designs in the factorial arrangements 4?×?2 and 8?×?2. On the first trial plantlets were inoculated with the Burkholderia sp. AB202; Herbaspirillum sp., BA227, both of strains and controls bacteria, with and without Foc and cultivated in pots filled with an autoclaved mixture of washed sand and vermiculite (ratio 3:2 v v^?1), during 4 months. On a second assay, plants were subjected to following conditions: absence and presence of strains AB202, AB213 (Burkholderia spp.), BA227, BA234 (Herbaspirillum-like), AB202 plus BA227, AB213 plus BA234, the mixture of the four bacterial strain, absence and presence of the Foc; and cultivated in pots filled with autoclaved Haplic Arenosol, during 2 months. The plant association with diazotrophs and the Foc was confirmed, and factors interacted significantly on the most probable number of bacteria and the colony forming units of the pathogen on roots and plant rhizomes. The potential of the endophytes on the inhibition of Foc propagate units and on the plant growth promotion was demonstrated. The higher biomass was observed four and 2 months after plant inoculation with AB202 and BA234. Results showed that these endophytes may be used as potential biofertilizer and biocontrol agents.