Evaluation of certain entomopathogenic nematodes against the melon ladybird,Epilachna chrysomelina F. (Coleoptera: Coccinellidae)

Three native Egyptian nematode isolates; Heterorhabditis taysearae and Heterorhabditis sp. S1 (Heterorhabditidae) and Steinernema carpocapsae S2 (Steinernematidae) as well as H. bacteriophora Hp88 as an imported species, were used in the present work to evaluate their activities against larvae and adults of the melon ladybird, Epilachna chrysomelina. The target pest was found to be susceptible to all tested entomopathogenic nematodes under laboratory conditions of 30±5°C.

In the greenhouse, a single spray of nematode suspension (1000 infective juveniles per ml) of each of H. taysearae, H. bacteriophora Hp88 and Steinernema carpocapsae S2 on squash seedlings was enough to give a reasonable mortality of 4^th larval instar E. chrysomelina, reaching 65.2, 44.0 and 84.0%, respectively, one week after application. This gives evidence that the Egyptian nematode isolates could tolerate high temperature and could be recommended for application in the control programmes of E. chrysomelina larvae in cucurbit fields.     

Individual variation in two host plants of the ladybird beetle,Epilachna pustulosa (Coleoptera: Coccinellidae)

Individual variation in two species of host plants (thistle,Cirsium kamtschaticum, and blue cohosh,Caulophyllum robustum) of the herbivorous ladybird beetleEpilachna pustulosa was examined under laboratory conditions for their acceptability to adult beetles as a food resource, for adult preference and for larval performance. When clones of these plants were subjected to non-choice tests using posthibernating female beetles, there was found to be significant intraspecific variation among clones in terms of their acceptability, but interspecific variation was not detected. Significant intraspecific as well as interspecific variation were frequently detected in the two host plants when clones of these plants were subjected to choice tests using posthibernating female beetles; the magnitude of interspecific plant variation for beetle preference is not necessarily larger than that of intraspecific plant variation. Individual variation across plant species with respect to beetle larval performance was also significant. A positive correlation between adult preference and larval performance is suggested across the two taxonomically remote host plant species, thistle and blue cohosh, although this needs further investigation.     

Genetic architecture for normal and novel host-plant use in two local populations of the herbivorous ladybird beetle, Epilachna pustulosa

Trade-offs in host-plant use are thought to promote the evolution of host specificity. However, usually either positive or no genetic correlations have been found. Whereas factors enhancing variation in overall viability have been claimed to mask negative genetic correlations, alternative hypotheses emphasize the sequential changes in genetic correlation in the course of host-range evolution. In this study, the genetic architectures of performances on different hosts were compared in two populations of the herbivorous ladybird beetle, Epilachna pustulosa, using three host plants, one being normal for both, one novel for only one population, and the other novel for both populations. The genetic correlations between larval periods on normal hosts were significantly positive whereas those between normal and novel hosts were not different from zero. There was no evidence for reduced genetic variation on the normal host-plants. These results suggest that the host-range is not restricted by the antagonistic genetic associations among exploitation abilities on different plant species, but rather that selection of different host-plants may improve the coordination between genes responsible for the use of different plants.     

Divergent host plant preference causes assortative mating between sympatric host races of the ladybird beetle,Henosepilachna diekei

Divergent host preference (i.e. host fidelity) plays a significant role in the speciation process in phytophagous insects. However, how and to what extent this divergence reduces gene flow between populations has rarely been measured. Here, we estimated the intensity of assortative mating caused solely by host fidelity in two host races of the phytophagous ladybird beetle Henosepilachna diekei, specialized on Mikania micrantha (Asteraceae) and Leucas lavandulifolia (Lamiaceae) in West Java, Indonesia. These host races mated randomly in the absence of host plants under laboratory conditions, but demonstrated nearly complete assortative mating in field cages with the two host plants, by spending almost all of their time on their respective host plants. The frequency of assortative mating in the field cages was not affected drastically by host plant patch structure. These results suggest that fidelity to the different host plants yields directly almost complete reproductive isolation between the host races by limiting the habitat on the respective host plant. In addition, the high host fidelity also ensures female oviposition on the original host plant. As larvae cannot survive on non‐host plants, a positive association between female oviposition preference and larval performance on the host plant on which the beetles are specialized will further facilitate the evolution of host fidelity. © 2013 The Linnean Society of London, Biological Journal of the Linnean Society, 2013, 110 , 606–614.     

印楝素乳油对黄曲条跳甲种群控制作用评价

在生命表方法分析的基础上。建立了害虫累积为害量指标,用以描述和比较某一时间段内害虫动态持续为害力大小．应用该指标分析印楝素乳油对黄曲条跳甲(Phyllotreta striolata(F.))种群控制作用,结果表明,对成虫显著的忌避作用是其对种群控制的主要机理．印楝素0．50ml·L^-1对成虫的忌避率为83．75％,种群趋势指数I值降为0．3354,干扰作用控制指数为0．0863．采用田间试验获得的结果,避免了室内测定的空间限制,因而是评价异源植物次生化合物对害虫忌避作用的主要依据．该指标在以害虫控制为目标的动态研究中具有较好的应用前景．     

Response ofNabis roseipennis [Heteroptera: Nabidae] to Larvae of Mexican bean beetle,Epilachna varivestis [Col.: Coccinellidae]

Laboratory studies were done to measure predation by adult damsel bugs,Nabis roseipennis Reuter [Heteroptera: Nabidae], on 3^rd instar larvae of Mexican bean beetle (MBB),Epilachna varivestis Mulsant [Coleoptera: Coccinellidae], and to measure longevity and body weight of the nabids. In the 1^st experiment, field-collected nabids were isolated for 24h in 9 cm Petri dishes with lima bean foliage (Phaseolus lunatus L.) and were assigned to one of 3 prey treatments: either 4 3^rd-instar MBB larvae, 4 3^rd-instar larvae of boll weevil (BW),Anthonomus grandis Boheman [Coleoptera: Curculionidae], or 2 larvae of each species. No MBB larvae were attacked in either the MBB treatment or 2-species treatment. In contrast, BW larvae were attacked in both BW and 2-species treatments. Significantly more BW larvae were attacked in the BW treatment than in the 2-species treatment, and both were greater than the number of MBB larvae attacked. Nabids that did not attack prey lost weight during the 24 h, whereas those that attacked prey gained weight. In the 2^nd experiment, nabids that had attacked prey were isolated with lima foliage, and nabids that had not attacked prey were kept with MBB and lima foliage until an attack or death. In no instances were MBB attacked. Longevity and the pattern of weight loss did not differ between nabids that did or did not attack prey. We discuss possible reasons for the failure ofN. roseipennis to attack MBB larvae, as well as the implications for using nabids to influence pest populations in the field.      

河西走廊天然固沙植被区地表甲虫多样性及其对沙漠化的指示作用

干旱、半干旱区沙漠化强烈影响动植物分布及多样性,地表甲虫是荒漠中主要的动物类群,它们对沙漠化引起的植被和土壤环境变化响应十分敏感。鉴于此,以河西走廊中部张掖绿洲外围的天然固沙植被区作为研究区,依据沙漠化发育程度选择流动沙丘（ASD）、丘间低地（IL）、半固定（SFSD）和固定沙丘（FSD）4种生境,调查了地表甲虫群落组成及影响甲虫分布的植被和土壤环境。研究发现,4种生境地表甲虫群落组成明显不同并存在季节变异,5月ASD与IL、SFSD和FSD生境地表甲虫群落的相异性大于8月。5月和8月SFSD生境地表甲虫活动密度均显著高于其他生境,8月FSD生境地表甲虫多样性指数显著高于其他生境。不同大小甲虫对沙漠化的响应模式不同,大中型甲虫对沙漠化的响应较小型甲虫敏感,这在5月表现尤为明显。地表甲虫与环境因子的RDA分析结果表明,12个植被和土壤环境因子解释了49.8%的地表甲虫群落变异,其中植被环境解释了甲虫群落变异的16.3%,土壤环境解释了甲虫群落变异的4.2%,植被和土壤环境相互作用解释了甲虫群落变异的29.3%。pRDA分析结果表明,草本物种丰富度、灌木盖度、土壤有机碳含量和粗砂含量是影响地表甲虫分布的主要环境因子,它们解释了43.7%的地表甲虫群落变异。Pearson相关分析表明,草本物种丰富度与地表甲虫活动密度呈显著正相关,而与地表甲虫均匀度呈显著负相关;灌木盖度与地表甲虫多样性呈显著正相关;地表甲虫物种丰富度与灌木盖度和草本物种丰富度均呈显著正相关。此外,研究还发现戈壁琵甲、克氏扁漠甲、中华砚甲和甘肃齿足象可以用于指示FSD生境,东鳖甲属昆虫可以用于指数SFSD生境,谢氏宽漠王可以用于指示IL及ASD生境。     

Laboratory evaluation of the toxic properties of forest anchomanes, Anchomanes difformis against pulse beetle Callosobruchus maculatus （Coleoptera： Bruchidae）

Laboratory experiments were carried out to investigate the efficacy of crude stem extracts of forest anchomanes, Anchomanes difformis （P. Beauv.） a plant occurring in West African forests, against the pulse beetle Callosobruchus maculattts （Fabricius）. Crude stem extracts at 3% concentration showed high contact toxicity to adult beetles within 24 h after application, while it was moderately toxic to the beetles at the lowest （1%） concentration. At the highest application rate, the plant extract provided good protection to grains stored for 90 days. Grain viability and water absorption capacity were not affected by treatments with ethanol extracts ofA. difformis. The significance of these findings is discussed in relation to biopesticide-means of controlling cowpea bruchids.     

A high-throughput reporter gene assay to prove the ability of natural compounds to modulate glutathione peroxidase,superoxide dismutase and catalase gene promoters in V79 cells

The aim of the study was to establish a 96-well microtiter plate-based reporter gene assay to test the influence of natural compounds on the promoter activities of rat catalase, human glutathione peroxidase and human superoxide dismutase expressed in V79 cells. Luciferase expression vectors with the promoter regions of the genes coding for the three above-mentioned enzymes were constructed and transfected into V79 cells. Thereafter the ability of sodium ascorbate, L-carnitine, catechin, epigallocatechin gallate, genistein, paraquat, quercetin, 12-O-tetradecanoylphorbol-13-acetate and Trolox to enhance the promoter activities was evaluated. Genistein, paraquat and quercetin led to a statistically significant increase in the glutathione peroxidase and superoxide dismutase gene promoter activities. None of the compounds tested enhanced the catalase gene promoter activity. The reporter gene assay described in this report is easy to perform, fast and allows one to test a high number of compounds and different concentrations of a single compound at the same time.     

Life-history traits of the acarophagous lady beetle,<Emphasis Type="Italic">Stethorus japonicus</Emphasis> at three constant temperatures

Stethorus japonicusKamiya (Coleoptera: Coccinellidae) is an indigenous ladybird beetle in Japan, which feeds on many spider mite species. We evaluated the development, survivorship and life-history parameters of this lady beetle on a diet of eggs of the two-spotted spider mite, Tetranychus urticae Koch (red form) (Acari: Tetranychidae). In addition, the effect of short photoperiod on its reproduction was assessed. Survival rates from egg to adult were more than 71% at temperatures between 17.5 and 30 °C. The highest immature mortality was 100% at 35 °C followed by 76% at 15 °C and 52% at 32.5 °C. The lower threshold temperature for development from egg to egg-laying adult was 13.0 °C and the thermal constant was calculated as 238.7° days. Based on these data, the maximum number of generations that could complete development in a year under field conditions in Ibaraki, central Japan, would be between five and seven. The intrinsic rates of natural increase (r_m) were 0.093 at 20 °C, 0.156 at 25 °C and 0.241 at 30 °C. Reproductive diapause was induced at photoperiods with light phases shorter than 13 h at 18 °C.     

Laboratory evaluation of the chemosterilant lufenuron against the fruit flies Ceratitis capitata, Bactrocera dorsalis, B. cucurbitae, and B. latifrons

Four species of tephritid fruit flies, Ceratitis capitata, Bactrocera dorsalis, B. cucurbitae, and B. latifrons were evaluated for toxic, developmental, and physiological responses to the chemosterilant lufenuron. No significant mortality of laboratory strains of the first three species was observed after their exposure up to 50 μg/mL of lufenuron in agar adult diet, whereas B. latifrons adults fed with 50 μg/mL of lufenuron in the diet caused significant mortality compared to the control. Fertility of C. capitata adults fed on 50 μg/mL lufenuron-fortified diet between 7 and 12 days of age was approximately 46% of the no lufenuron control. Fertility of B. dorsalis and B. latifrons adults fed on 50 μg/mL lufenuron-incorporated diet was about 45% and 62% of the control, respectively. Lufenuron did not significantly affect fertility of B. cucurbitae adults. Lufenuron did not affect fecundity of C. capitata and B. dorsalis. Fecundity of B. cucurbitae and B. latifrons was not evaluated due to difficulty to count the eggs laid deep in the agar diet. Larvae fed on a liquid larval diet with ≤ 0.1 μg/mL of lufenuron were also evaluated. Pupal recovery, adult emergence, adult fliers, mating, egg hatch, and egg production of C. capitata were significantly decreased, while for B. dorsalis, pupal recovery, larval duration and adult emergence were affected. No effect of lufenuron on B. cucurbitae larvae was observed. B. latifrons was not performed because shortage of eggs at the time of this research. Lufenuron is a potential agent for management and control of C. capitata and B. dorsalis.