Comparative study of the effect of selected agrochemical products on Steinernema feltiae (Rhabditida: Steinernematidae)

The effect of three neurotoxic insecticides, three photosynthetic inhibitor herbicides and three enzymatic inhibitor herbicides on infective juveniles (IJs) of Steinernema feltiae Rioja (native) and ENTONEM® (commercial) strains were evaluated after a 48-h exposure at field tank concentrations and overnight treatment in mQ-water, using Spodoptera littoralis as target. Nematode survival was not affected by acetyl-cholinesterase inhibitors chlorpyrifos and pirimicarb, although chlorpyrifos seriously reduced their virulence. Both nematode strains showed differential sensitivity to cypermethrin, which affects the sodium channels of the nerve membrane, with the ENTONEM® strain being more tolerant than Rioja strain. However, these chemicals showed a strong sublethal effect on the nematode reproductive potential, limiting seriously their possible recycling in the field. Herbicides showed differential toxic effects on nematode survival. The commercial strain was tolerant to enzymatic inhibitor herbicides, whereas tribenuron and chlorsulfuron reduced Rioja strain survival. However, photosynthetic inhibitor herbicides severely affected survival of both nematode strains, with the Rioja strain being more sensitive. Sublethal effects on both nematode strains were observed only after exposition to terbutryn+chlortoluron+triasulfuron, increasing the time to kill insect larvae. These results are useful to optimize EPN dosages and to estimate their field recycling.     

An analysis of the deterrent effect of aphids on cabbage root fly (Delia radicum) egg-laying

Abstract. 1. The cabbage root fly, Delia radicum (L.), was deterred from laying eggs on brassica plants with >250 cabbage aphid, Brevicoryne brassicae (L.), or peach-potato aphid, Myzuspersicae (Sulz.).
2. Flies did not lay on plants infested with >250 aphids.
3. Preparations of (E)-β-farnesene, the aphid alarm pheromone, deterred the flies from laying only at the extremely high dose of 32 mg/plant.
4. Although M. persicae secreted large (1 ng/insect) amounts of alarm pheromone and B. brassicae extremely small (<0.01 ng/insect) amounts, both aphids equally deterred D. radicum from laying.
5. The deterrent effect appeared to result from the aphids physically disturbing the flies during host-plant selection.     

Efficacy of the entomopathogenic nematode, Steinernema feltiae, against Bemisia tabaci in relation to plant species

Abstract:  The use of infective juveniles (IJs) of the entomopathogenic nematode, Steinernema feltiae , to control the immature stages of the tobacco whitefly, Bemisia tabaci (Gennadius) (Hom., Aleyrodidae), on a range of host plants was investigated. Foliar applications of S. feltiae (10 000 IJs/ml) were made to tomato ( Lycopersicon esculentum ), cucumber ( Cucumis sativus ), poinsettia ( Euphorbia pulcherrima ), chrysanthemum ( Dendranthema spp.) and verbena ( Verbena hybrida ) infested with second instar B. tabaci , to determine whether efficacy was influenced by plant species. The effect of the adjuvants Agral, Triton X-100, methylcellulose, glycerol and spraying oil on the level of pest mortality was also assessed using two selected host plants, tomato and verbena. Following nematode application B. tabaci mortalities of 32, 28, 22 and 22% were recorded on tomato, cucumber, verbena and chrysanthemum, respectively, but a lower mean mortality was noted for whitefly feeding on poinsettia (10%). Mortality of B. tabaci on tomato and verbena was significantly increased by the addition of either Triton X-100 or Agral to the spray suspension. The use of Triton X-100 raised the mortality level to 63 and 37% on tomato and verbena, respectively, while 50 and 27% mortality followed the use of Agral on the two hosts. With the exception of glycerol no phytotoxic effects were observed by the adjuvants when applied to all five host plant species used in this study. The potential for use of the entomopathogenic nematode, S. feltiae , as a non-chemical alternative control measure for B. tabaci immatures is discussed.     

Comparison of the egg-laying behaviour and electrophysiological responses of Delia radicum and Delia floralis to cabbage leaf compounds

Abstract.  The behaviour and the sensitivity of adult cabbage root fly, Delia radicum and turnip root fly, Delia floralis are compared with host-plant extracts and isolated crucifer compounds previously identified as oviposition stimulants for D. radicum . The oviposition behaviour of both species is similar; 7–10-day-old females are stimulated to lay eggs by the methanol extract of cauliflower leaves that contains thia-triaza-fluorenes (CIF) as well as glucosinolates. The glucosinolate fraction is mainly composed of glucobrassicin, which alone stimulate both fly species to lay eggs. The C₅ and D_3,4 sensilla on the prothoracic tarsae of newly-emerged D. radicum contain neurones sensitive to the glucosinolate fractions tested and to glucobrassicin, whereas the CIF specifically stimulate a neurone in the C₅ sensillum. By contrast, newly-emerged D. floralis respond less to glucosinolates, especially to glucobrassicin, and have sensitive neurones to CIF in other sensilla than D. radicum . Recordings are also made from the longest sensilla present on the labellum because they are apparently sensitive to glucosinolates. By contrast to earlier investigations, no remarkable phasic-tonic responses of these neurones are seen. The two species are difficult to discriminate visually, have the same host plants, show identical host-selection behaviour, apparently respond to the same physical and chemical properties of their host-plants, but have a clearly different distribution of receptor neurones in the tarsal sensilla.     

The relationship between cabbage root fly (Delia radicum) larval feeding and the freeze-dried matter and sugar content of Brassica roots

Five genotypes of swede (Brassica napus var. napobrassica), two genotypes of kale (B. oleracea var. acephala), and two genotypes of rape (B. napus var. napus) were each inoculated at the 8–10 true leaf stage with five cabbage root fly (Delia radicum) eggs. The percentage pupation after larval feeding on individual plant genotypes ranged from 45 to 78%, and the mean pupal weight from 6.5 to 13.0 mg. After 5 weeks, larval feeding damage had reduced root weight by up to 47%, compared with uninoculated plants. The dry matter content of undamaged roots was higher in the kales and rapes than in the swedes. Whilst the dry matter content of the rapes and swedes were not changed by D. radicum damage, that of the kales was elevated. The ethanol-soluble sugar content of the root was reduced in all cases by D. radicum larval damage. However, the effect of D. radicum damage on the concentrations of individual sugars (glucose, fructose and sucrose) was crop- and genotype-dependent. In the roots of kales and rapes, the glucose and fructose concentrations were either very low or unaffected by D. radicum damage, whilst both glucose and fructose were generally reduced in swede roots by D. radicum damage. The root sucrose concentration was either reduced or not significantly affected by D. radicum damage in all of the crop types tested. The percentage pupation and the mean pupal weight of D. radicum were inversely correlated to root freeze-dried matter content. D. radicum pupal weight was positively correlated with root fructose, glucose and ethanol-soluble sugar contents.     

Inter- and intra-population differences in the effects of temperature on postdiapause development of Delia radicum

Canadian populations of D. radicum differ in their response to temperature during postdiapause development. Populations that are primarily of the early-emerging type ( ) (St-Jean, Quebec; London, Ontario) have high values for the parameters describing this response: % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaamOuamaaBa% aaleaacaWGTbaabeaakiabg2da9aaa!38F2!$$R_m = $$ 12.7–13.3; 28.0–31.8 °C ; T = 10.3–14.2 ( , the maximum developmental rate at the temperature, [ °C ] where the developmental rate is highest, and T , the parameter which gives the shape of the truncated normal curve fitted to the data), a low degree-day requirement for emergence (160–232 ), and may lack a developmental delay at temperatures above ca. 21 °C . Populations of the late-emerging type (Kildare, Prince Edward Island) have low parameter values ( , °C ; T = 6.4), high degree-day requirements (530 ), and a developmental delay at high temperatures. The parameters for the early-emergers in the population from Winnipeg, Manitoba (74% early) were intermediate ( , °C , T = 10.7, ), but resembled the early rather than the late type. This population varied from 31 to 90% early type over a 10-year period and the rate of postdiapause development at 20 °C was directly related to the percentage early. In the year with the most rapid development (90% early), development was significantly slower than in the populations from other locations with predominantly early populations, and the year with the slowest development (31% early) showed significantly faster development than that from Kildare, Prince Edward Island (100% late). Therefore the parameters for early and late types of development will not be accurate for use in mixed populations, and the parameters in mixed populations will change among years. Populations of D. radicum in North America and Europe (67 locations by years) varied from 0–100% early. At Winnipeg, the percentage early was directly related to the annual temperature accumulation ( ) during the growing season. The calculation of developmental parameters for the early-emergers of mixed populations provides a more accurate basis for estimating the times of first emergence and the first peak of emergence than parameters based on the whole population. Since postdiapause developmental rates vary both among and annually within locations, developmental models should be designed to include such variations.     

Evaluation of the nematodes Steinernema feltiae and Thripinema nicklewoodi as biological control agents of western flower thrips Frankliniella occidentalis infesting chrysanthemum

In greenhouse studies, we evaluated a commercial formulation of the entomopathogenic nematode Steinernema feltiae and the inoculative release of the thrips-parasitic nematode Thripinema nicklewoodi against western flower thrips (WFT), Frankliniella occidentalis Pergande infesting potted chrysanthemums. Foliar sprays of S. feltiae applied at 1.25-2.5×10³ IJ mL^-1 and 1000 - 2000 L ha^-1 at 3-day intervals alone (targeting feeding stages) or in combination with soil applications (simultaneously treating non-feeding stages in the soil at the same rates) decreased but did not provide adequate control of thrips in flowering plants artificially infested with a dense population. Similar nematode treatments applied for four to five applications at 6-day intervals in two batches of initially clean chrysanthemums failed to prevent unacceptable damage to flowers and leaves from a dense natural infestation within the greenhouse. Although some IJ survived up to 48 h within flowers and flower buds, few nematode-infected thrips (larvae and adults) were recovered. In studies with T. nicklewoodi (which is not amenable for mass production), the inoculative releases of two parasitized hosts per plant enabled the nematode to become established within existing WFT populations under greenhouse conditions. However, relatively poor transmission and slow speed of kill (nematode primarily suppresses populations through host sterilization) prevented low level inoculations being effective over a single crop cycle. Further studies showed that transmission of T. nicklewoodi persisted for nine host generations, infected up to 83% of adult thrips and provided long-term suppression of discrete caged populations, but only after uneconomically high thrips densities had been reached.     

Aboveground herbivory affects indirect defences of brassicaceous plants against the root feeder Delia radicum Linnaeus: laboratory and field evidence

1. Belowground herbivory has recently been shown to disrupt the host location behaviour of aboveground parasitoids and thereby impact plants indirect defences. Reverse interactions, on the other hand, have received little attention so far. 2. Lab and field studies were conducted to examine whether the presence of the leaf herbivore Pieris brassicae Linnaeus on brassicaceous plants influences the response of Trybliographa rapae Westwood, a specialist parasitoid of the root feeder Delia radicum Linnaeus. 3. The present results show that the attraction of the parasitoid towards host‐infested plants disappeared when these plants were also infested by P. brassicae. This absence of attraction was observed both when the complete odour blend or only undamaged leaves from damaged plants were offered, emphasising the role of systemically induced volatiles for host location in T. rapae. 4. Furthermore, the field study revealed that parasitism levels dropped from 30% on root‐infested plants to 4% on double‐infested plants. 5. The present study is the first to confirm that reduced attraction to host‐infested plants as a result of simultaneous attack by below‐ and aboveground herbivores translates into lower levels of parasitism in the field.     

Comparative effects of Steinernema feltiae (Nematoda: Steinernematidae) and insecticides on yield and cropping of the mushroom Agaricus bisporus

In a mushroom crop (Agaricus bisporus) affected by a very low level of sciarid fly (Lycoriella auripila) infestation, the effects of an indigenous isolate of insect-parasitic nematode (Steinernema feltiae) and of two commonly used insecticides (diazinon and diflubenzuron) were studied. When compared with untreated plots, nematodes applied to the casing had no adverse effects on mushroom yields whereas insecticides decreased yields. At a rate of 3 × 10⁶ infective juveniles per tray (surface area = 0.56 m²), S. feltiae elicited increases of 28.5% and 19% in the mean total numbers and weights of mushrooms respectively. Treatment only with diflubenzuron resulted in 14.6% and 6% reductions in mean total numbers and weights of mushrooms, respectively; treatment with both diazinon and diflubenzuron caused 18.5% and 9.4% losses. Application of nematodes generally reduced the mean weight per mushroom whereas insecticides increased it; nematodes delayed the onset of mushroom production (first flush) whereas diflubenzuron delayed the third and fourth flushes. Nematode contamination of sporophores was minimal when S. feltiae was applied at casing. Although their numbers declined with time, the nematodes persisted, in the casing layer, throughout the cropping period of seven weeks. It is concluded that yield benefits associated with nematode application can result mainly from nematode effects on A. bisporus and not solely from suppression of a damaging pest population.     

Recycling of entomopathogenic nematodes in Delia radicum and in other insects from cruciferous crops

Larvae of Deliaradicum Linnaeus (Diptera: Anthomyiidae) wereexposed to Steinernema feltiae Filipjev(Rhabditida) to study the ability of thenematodes to fulfill their life cycle (recycle)in this host. In addition, the recycling ofSteinernema and Heterorhabditis(Rhabditida) species was studied in larvae ofthe following insects: Meligethes spp.Stephens (Coleoptera: Nitidulidae),Dasyneura brassicae Winnertz (Diptera:Cecidomyidae), Ceutorrhynchus assimilisPaykull, C. pallidactylus Marsham (Coleoptera: Curculionidae) and Mamestrabrassicae Linnaeus (Lepidoptera: Noctuidae).All larval instars of D. radicum werestudied (larvae live and pupate in soil)whereas the final instars of the remaininginsects were studied (larvae only pupate in soil).On average, the following numbers of infectivejuveniles were produced in the different hosts:1,200–1,400 in C. assimilis; 700–1,300 inMeligethes spp. and 47,000 in M.brassicae. In D. radicum, around 400infective juveniles were produced on average inthe smallest larvae and around 3,500 in thelargest larvae. The highest number of nematodesrecorded in a D. radicum larva (thirdinstar) was 9,500 infective juveniles. Thenumber of nematodes produced in D.radicum cadavers was positively related to thesize of the insect host, but large variationwas observed.     

Insect-crop interactions in a diversified cropping system: parasitism by Aleochara bilineata and Trybliographa rapae of the cabbage root fly, Delia radicum, on cabbage in the presence of white clover

Parasitism of the cabbage root fly, Delia radicum (L.) by the staphylinid Aleochara bilineata Gyllenhal and the cynipid Trybliographa rapae Westwood was examined in a cabbage monoculture and a mixed stand of cabbage undersown with white clover. Number of overwintering cabbage root fly pupae per plant was consistently reduced in the mixed stand, and the incidence of plants attacked by cabbage root fly was either reduced or not different in the mixed stand compared to cabbage monoculture. For both parasitoids, the probability of D. radicum attacked plants having at least one parasitized pupa increased with density of cabbage root fly pupae around the plant. For A. bilineata, this positive relation between presence of parasitism and host density was consistently stronger in cabbage monoculture than in cabbage undersown with clover. Location of a host plant by T. rapae was not consistently affected by the presence of clover. D. radicum attacked plants situated in the cabbage and clover mixture were found by T. rapae as easily as in cabbage monoculture. Overall, the total risk of parasitism for a cabbage root fly pupa by A. bilineata was reduced in the mixed stand compared to the cabbage monoculture, whereas the risk of parasitism by T. rapae was not consistently affected by clover. For both parasitoids, intensity of parasitism showed a variable relationship with host density on individual plants attacked by the cabbage root fly. Overall, in spite of consistently lower total density of pupae in the mixed cabbage—clover than in cabbage monoculture, the density of unparasitized pupae was reduced by the presence of non-host plants only in two of the four experiments. The results emphasize the need to include not only herbivore and crop, but also other plant species as well as natural enemies when evaluating management methods.     

Steinernema feltiae (DD-136) and S. glaseri: Persistence in Soil and Bark Compost and Their Influence on Native Nematodes

Infective juveniles (J3) of the entomogenous nematodes Steinernema feltiae DD-136 (ca. 10,000 J3/100 ml) and S. glaseri (ca. 2,500 J3/100 ml) were incubated in steam-sterilized and nonsterilized sandy soil and bark compost for 8 weeks at 25 C. The nematodes were recovered by a two-step extraction procedure at 1-week intervals, and their infectivity to lepidopterous larvae (Spodoptera litura and Galleria mellonella) and their effect on the population and community of native nematodes in soil were determined. Survival of inoculated nematodes and mortality of insects were enhanced in sterilized media. Nonsterilized bark compost proved to be equally as suitable a medium as sterilized compost. In nonsterilized soil, the survival curve of S.feltiae declined more rapidly than that or S. glaseri which was less infective to insects despite its greater persistence even in nonsterilized soil. Soon after the addition of steinernematids to soil, the population of native nematodes showed a fluctuation with an increase in rhabditids and a decrease in other kinds of nematodes.     

EVect of the Entomopathogenic Nematodes, Steinernema feltiae and S. carpocapsae , on the Potato Cyst Nematode, Globodera rostochiensis , in Pot Trials

Two pot experiments, one in a glasshouse and the other in an outdoor sand plunge, were conducted to examine the influence of the entomopathogenic nematodes, Steinernema feltiae and S. carpocapsae , on the invasion and development of the potato cyst nematode, Globodera rostochiensis . Of a total of eight diVerent treatments with entomopathogenic nematodes in the glasshouse trial, three reduced the invasion of G. rostochiensis and one reduced the numbers of new cysts that were produced compared with controls. In the outdoor experiment, seven of the 12 treatments gave a reduction in invasion but none resulted in changes in the numbers of cysts found at plant senescence. In general, invasion of G. rostochiensis juveniles was reduced more eVectively by S. carpocapsae than by S. feltiae , and was greatest in the outdoor trial where larger inocula of entomopathogenic nematodes were used. Overall, the results indicated that use of S. feltiae and S. carpocapsae is unlikely to provide a viable control strategy for G. rostochiensis .     

Target Host Finding by Steinernema feltiae and Heterorhabditis bacteriophora in the Presence of a Non-Target Insect Host

The ability of Steinernema feltiae or Heterorhabditis bacteriophora infective juveniles (IJ), when applied to the soil surface, to infect a Galleria mellonella larva at the base of a soil-filled cup (276 cm³) was evaluated in the presence and absence of 100 larvae of a non-target insect, the aphid midge Aphidoletes aphidimyza, near the soil surface. In all four trials with either S. feltiae or H. bacteriophora, A. aphidimyza presence did not affect the number of IJ finding and infecting a G. mellonella larva. Steinernema feltiae and H. bacteriophora IJ movement (as measured by the percentage of IJ aggregating on either side of an experimental arena) in the presence of one or many A. aphidimyza larvae was evaluated in agar- and soil-filled petri dishes, respectively. Infective juvenile movement in the presence of A. aphidimyza did not differ from random, indicating that IJ were not attracted to A. aphidimyza. It is suggested, therefore, that A. aphidimyza does not reduce IJ efficacy when these two forms of biological control agent are present together in a field situation even though it is known that A. aphidimyza is susceptible to IJ of these species.     

Influence of cell density and phase variants of bacterial symbionts (Xenorhabdus spp.) on dauer juvenile recovery and development of biocontrol nematodes Steinernema carpocapsae and S. feltiae (Nematoda: Rhabditida)

The rhabditid nematodes Steinernema carpocapsae and Steinernema feltiae are used in biological control of insect pests. Mass production is done in liquid culture media pre-incubated with their bacterial symbionts Xenorhabdus nematophila and Xenorhabdus bovienii, respectively, before nematode dauer juveniles (DJs) are inoculated. As a response to food signals produced by the bacterial symbionts, the DJs exit from the developmentally arrested dauer stage (they recover development) and grow to adults, which produce DJ offspring. Variable DJ recovery after inoculation often causes process failure due to non-synchronous population development and low numbers of adult nematodes. This contribution investigated the influence of the bacterial cell density on DJ recovery and development to adults. At higher density of 10¹⁰ bacterial cells ml⁻¹, a higher percentage of DJ recovery was induced, and adults occurred earlier in both Steinernema spp. than at lower density of 10⁹ and 10⁸ cells ml⁻¹. Xenorhabdus symbionts produce phase variants. Recovery in bacteria-free supernatants was lower than in supernatants containing bacterial cells for both primary and secondary phase Xenorhabdus spp. and lower in secondary than in primary phase supernatants or cell suspensions. In general, recovery was lower for Steinernema feltiae and the time at which 50% of the population had recovered after exposure to the food signal was longer (RT₅₀ = 17.1 h) than for Steinernema carpocapsae (RT₅₀ = 6.6 h). Whereas >90% S. carpocapsae DJs recovered in hemolymph serum of the lepidopteran insect Galleria mellonella, recovery of S. feltiae only reached 31%. Penetration into a host insect prior to exposure to the insect’s food signal did not enhance DJ recovery. Consequences for liquid culture mass production of the nematodes and differences between species of the genera Steinernema and Heterorhabditis are discussed.     

Effects of entomopathogenic nematodes on the spruce web‐spinning sawfly Cephalcia arvensis panzer and its parasitoids in the field

Field tests were conducted in the Asiago Forest, Venetian Prealps (Italy) to evaluate the efficacy of nematode strains (Heterorhabditis sp. HL 81 Steinernema carpocapsae IS 230 S. feltiae C = bibionis,) IS 389 S. kraussei SK) against the spruce web‐spinning sawfly Cephalcia arvensis. Soil applications of 100 juveniles cm^‐2 of S. feltiae and S. kraussei resulted in 56% and 36.4% reduction of emergences of sawfly, respectively, when performed before the mature larvae drop and enter the soil. The effectiveness of S. feltiae becomes 32.3% if the nematodes are applied when the larvae have already prepared their chambers. S. feltiae parasitized more females and long‐term diapausing individuals than S. kraussei. The two most effective strains (IS 389 and SK) seem to be well adapted to low temperature, which is likely to be the most important limiting factor for nematode activity in the mountain spruce forests. An ichneumonid parasitoid (Xenoschesis fulvipes,) was strongly affected by S. feltiae, resulting in 66.6% reduction of emergences. Another ichneumonid Ctenopelma lucifer, seems to be less affected than X. fulvipes by the nematode application.     

Effect of various cauliflower cultivars on population density fluctuations of the cabbage aphid,Brevicoryne brassicae (L.) (Hom.: Aphididae) and its parasitoid Diaeretiella rapae (McIntosh) (Hymenoptera: Braconidae)

In this study, population density changes of the cabbage aphid, Brevicoryne brassica (L.), were tested in the field during 2011 under natural infestation at research field of the Shahed University (South of Tehran). This investigation was conducted on the eight cauliflower cultivars including Smilla, Snow mystique, White cloud, Buris, Galiblanka, Snow crown, SG and Tokita in randomised complete block design with five replications. Sampling was done after starting of aphid activity in the field every week and the total number of adult aphids and nymphs were counted in three leaves of the upper, middle and lower parts of the plant. In addition, the percentage of parasitism of the cabbage aphid by Diaeretiella rapae was evaluated. Results of the sampling showed that peak of the aphid population were at the first half of November. The parasitism percent of the cabbage aphid by D. rapae was significantly different among studied cultivars (p?<?0.05). Therefore, it can be concluded that using of Smilla, Buris and SG cultivars probably increases the efficiency of D. rapae in the control of the B. brassica (L.).     

Variations in Immune Response of Popillia japonica and Acheta domesticus to Heterorhabditis bacteriophora and Steinernema Species

The infectivities of Steinernema carpocapsae, S. glaseri, S. scapterisci, and Heterorhabditis bacteriophora to Japanese beetle larvae, Popillia japonica, and house cricket adults, Acheta domesticus, were compared using external exposure and hemocoelic injection. Only H. bacteriophora and S. glaseri caused high P. japonica mortality after external exposure. When nematodes were injected, P. japonica had a strong encapsulation and melanization response to all species except S. glaseri. Heterorhabditis bacteriophora and S. carpocapsae were able to overcome the immune response, but S. scapterisci was not. All species except S. scapterisci were able to kill and reproduce within the host. Only S. scapterisci and S. carpocapsae caused A. domesticus mortality after external exposure. When nematodes were injected, A. domesticus had a strong immune response to all species except S. scapterisci. Steinernema carpocapsae effectively overcame the strong immune response and caused high host mortality, but S. glaseri and H. bacteriophora did not. Steinernema scapterisci caused high host mortality and reproduced, S. glaseri and H. bacteriophora caused low host mortality but only S. glaseri reproduced, and S. carpocapsae was able to kill the host but reproduced poorly. Most (ca. 90%) of the S. carpocapsae in the hemocoel of P. japonica became encapsulated and melanized within 8 hours postinjection. The symbiotic bacterium, Xenorhabduf nematophilus, was often released before this encapsulation and melanization.     

Effectiveness of Steinernema spp. and Heterorhabditis bacteriophora against Popillia japonica in the Azores

Steinernema carpocapsae (Breton strain), S. glaseri, and Heterorhabditis bacteriophora were evaluated for their potential to control immature stages of the Japanese beetle, Popillia japonica, on Terceira Island (the Azores). In bioassays carried out at temperatures higher than 15 C, S. glaseri and H. bacteriophora caused 100% mortality of larvae, whereas S. carpocapsae caused 56% larval mortality. At temperatures slightly below 15 C, only S. glaseri remained effective. In field plots, in September, S. glaseri and S. carpocapsae reduced larval populations by 91% and 44%, respectively, when applied at the rate of 10⁶ nematodes/m². In April, S. glaseri caused 31% reduction in numbers of larvae, but S. carpocapsae was ineffective. In colder months (November-February) neither steinernematids nor H. bacteriophora reduced larval populations. Increasing the application rate from 10⁶ to 5 x 10⁶ infective stage S. glaseri per m² increased efficacy from 63% to 79% mortality.     

深圳香荚兰,首次发现于华南深圳的兰科新种

对兰科新种深圳香荚兰Vanilla shenzhenicaZ．J．Liu＆S．C．Chen作了描述与绘图。此新种为深圳发现的第一个兰科新种,与台湾香荚兰V。somai Hayata有亲缘关系。但是,本新种花序具4花,花较大,不完全开放;唇瓣不裂,紫红色,基部与蕊柱合生长度达3/4,刷状附属物位于唇盘的上部,甚易区别于台湾香荚兰。