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.     

Arabidopsis thaliana leaf-surface extracts are detected by the cabbage root fly (Delia radicum) and stimulate oviposition

Abstract. Oviposition of the cabbage root fly, Delia radicum (Diptera, Anthomyiidae) is stimulated by leaf‐surface extracts of Arabidopsis thaliana (L.) Heynh. (Brassicaceae) ecotype Columbia. The leaf surface of A. thaliana, similar to that of many other crucifers, contains glucosinolates and CIF (‘cabbage identification factor’; 1,2‐dehydro‐3‐thia‐4,10,10b‐triaza‐cyclopenta[.a.]fluorene‐1‐carboxylic acid). These compounds stimulate receptor neurones of the tarsal sensilla of D. radicum whereas additional, unknown compounds are detected by other receptor neurones.     

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.     

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.     

Spatial patterns of Trybliographa rapae parasitism of Delia radicum larvae in oilseed rape and cauliflower

Trybliographa rapae (Westwood) is an important parasitoid of Delia radicum (L.). Parasitism of D. radicum larvae by T. rapae in relation to host density on canola (oilseed rape) and cauliflower roots was examined at 10 field sites in Germany and Switzerland. For roots with host larvae, the proportion of roots with one or more parasitized hosts increased with increasing host density. However, for these infested roots, the parasitism of individual larvae was not consistently related to host density. When considering only roots on which there were parasitized larvae and the opportunity for multiple attacks, the proportion of larvae that were parasitized decreased with increasing host density in the field locations, and in a cage study under controlled conditions. A model of patch‐finding and number of attacks by female parasitoids suggests that patch‐finding is density‐dependent, but that low attack rate and interference effects limit numbers of attacks to three or less per visit to a host patch; the reduced number of attacks per visit leads to the inverse relationship of larval parasitism with host density in the host patches visited. The interplay of the density‐dependent and inversely density‐dependent processes appears to be responsible for the inconsistency of density dependence of overall larval parasitism in this and previous studies. In the laboratory, adult female T. rapae parasitized hosts at ≤4 cm deep in soil, but not at 6 cm deep. From the depth distribution of larval feeding sites in the field, we infer that between 4% and 20% of Delia larvae may be in a physical refuge from T. rapae parasitism, which may have a stabilizing influence on the host–parasitoid interaction.     

Occurrence of Steinernema species in cabbage fields and the effect of inoculated S. feltiae on Delia radicum and its parasitoids

Abstract 1 Seven organically grown cabbage fields were surveyed for entomopathogenic nematodes in the autumn by baiting. Nematodes were obtained from three fields with bait larvae infection ranging from 1.3–4.0%. 2 Inoculation of Steinernema feltiae (Rhabditida: Steinernematidae) in the spring increased bait larvae infection to 16.0–32.0%. 3 Four different species were found (Steinernema affine, Steinernema bicornutum, S. feltiae and Steinernema C1). 4 The number of Delia radicum (L.) (Diptera: Anthomyiidae) puparia was significantly reduced at plants where S. feltiae had been inoculated. 5 Delia radicum parasitoids were also affected by S. feltiae. The results indicated that Aleochara species (Coleoptera: Staphylinidae) were more negatively affected than Trypliographa rapae (Westw.) (Hymenoptera: Cynipidae).     

Life history comparison between two competitive Aleochara species in the cabbage root fly, Delia radicum: implications for their use in biological control

This study evaluates the efficacy of Aleochara bilineata Gyll and Aleochara bipustulata L. (Coleoptera: Staphylinidae) as biological control agents against the cabbage root fly, Delia radicum L. (Diptera: Anthomyiidae). Biological and demographic characters are documented and comparisons made between the two species. The following results were obtained:(1) The reproductive potential and longevity of A. bipustulata females are significantly higher than those of A. bilineata. These differences are correlated with the biology and ecology of the hosts of both species.(2) Under laboratory conditions the rate of increase (r_m) of both staphylinids species is significantly higher than that of the pest and their major competitor Trybliographa rapae West. (Hymenoptera:Figitidae). This may indicate that A. bilineata and A. bipustulata can be effective biological control agents.(3) Aleochara bilineata appears to be the most interesting biological control agent against D. radicum, because of its higher rate of increase, higher host specificity and host acceptance, and a development time which is well synchronised with that of its host. With its higher competitive ability, a population of A. bilineata may increase even if competition occurs. However, A. bipustulata presents interesting biocontrol characteristics, but the best strategy may be only to use the potential of its natural populations.     

Toxicity of the insect growth regulator diflubenzuron to the rove beetle Aleochara bilineata, a parasitoid and predator of the cabbage maggot Delia radicum

The insect growth regulator Dimilin^®, common name: diflubenzuron, applied at concentrations effective against the cabbage maggot Delia radicum L., did not affect the hatching of eggs of the staphylinid predator and parasite, Aleochara bilineata Gyllenhal. Applied externally in distilled water, Dimilin was non-toxic to first instar larvae, to larval instars developing within host puparia, and to adults. When Dimilin was dissolved in dimethylsulfoxide, then applied to the exoskeleton of host puparia, emergence of A. bilineata adults was suppressed. The conventional insecticide Furadan, at a concentration (0.001% in distilled water) equal to the lowest concentration of Dimilin used, was toxic to both eggs and larvae of A. bilineata.

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Résumé Lorsqu' appliqué dans des concentrations efficaces contre la mouche du chou Delia radicum L. (0.1, 0.01, 0.001% p/v dans de l'eau distillée), le Dimilin (diflubenzuron), un régulateur de croissance des insectes, n'a pas affecté l'éclosion des oeufs de Aleochara bilineata Gyllenhal, un staphylin prédateur et parasite. En application externe, à la plus forte concentration (0.1% p/v dans de l'eau distillée), cet inhibiteur de synthèse de la chitine s'est avéré non toxique pour les larves du premier stade, les stades larvaires qui se développent à l'intérieur du puparium de l'hôte, et les adultes. Le traitement au Dimilin n'a pas affecté la fertilité des staphylins adultes. Cependant, lorsque le diflubenzuron était dissous dans du diméthylsulfoxyde et appliqué sur l'exosquelette du puparium de l'hôte, l'émergence des adultes de A. bilineata était éliminée. L'insecticide conventionnel Furadan (carbofurane), à une concentration égale à la plus faible concentration de Dimilin utilisée (0.001% p/v dans de l'eau distillée), s'est avéré toxique à la fois pour les oeufs et pour les larves de A. bilineata.

     

The complementary effects of plant resistance and reduced pesticide dosage in field experiments to control the turnip root fly, Delia floralis, in swedes

The integration of different doses of chlorfenvinphos with plant resistance to different levels of Delia floralis attack in swedes was investigated at Saerheim Research Station in field experiments during 1987, 1988 and 1989. The indices of damage and grade 1 yields indicated different levels of resistance ranging from the partially resistant cvs Melfort, Angus and Vige down to the susceptible cvs Gry and Ruta. The relative resistance of the cvs changed with increasing levels of damage. Cvs Melfort and Angus were consistently the most resistant, while the resistance of Vige seemed to break down at high levels of attack. At these levels and in the absence of chemical treatment Gry was as resistant as Melfort and Angus. At the lowest level of attack, the resistance alone gave satisfactory control with Melfort, Angus and Vige. A half dose of chlorfenvinphos was sufficient to protect Melfort and Angus at higher levels of attack. Damage levels recorded in October showed that the different cultivars expressed widely different levels of resistance to D. radicum than to D. floralis.     

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.     

Relationship of in vitro and in planta screening: improving the selection process for biological control agents against Fusarium root rot in row crops

Fusarium root rot in row crops is typically managed by cultural practices and fungicide seed treatments. Biological control using microbial agents is another option but needs further development for improved disease management. Screening to identify biocontrol agents are crucial. However, relationships among the steps and how to improve the screening process are unresolved questions. Strains of Burkholderia (4), Bacillus (5) and Trichoderma (26) were studied in vitro against six Fusarium pathogens. All the bacteria and five selected Trichoderma strains were tested in planta in the greenhouse against diseases of Fusarium graminearum and Fusarium oxysporum. Burkholderia ambifaria C628, Bacillus simplex R180, and all Trichoderma isolates showed high reduction in disease levels in corn, soybean and wheat, ranging from 16 to 63%. Responses of the biocontrol agents during in vitro and in planta screening did not always correlate. In vitro and in planta tests should be considered independently in selecting biocontrol candidates.     

Use of two formulations and two application techniques to deliver Bacillus thuringiensis var. israelensis for the control of Musca domestica (Diptera: Muscidae) larvae and adults in poultry houses

A field study was carried out for 6 wks to assess, from both an efficiency and economic perspective, the effect of individual and integrated success of feeding and topical applications of two formulations of Bacillus thuringiensis var. israelensis (Bti) in controlling house fly (Musca domestica L.) larvae and adults in poultry houses. There was no significant difference between the 1 g and 2 g L^?1 spray applications of Bti. In the absence of spray applications, no significant differences in larval mortalities were observed between the 250 mg and 500 mg kg^?1 feed applications. The percentage mortality of larvae accomplished as a result of using a combination of 250 mg kg^?1Bti feed and 2 g L^?1 spray applications was equivalent to that obtained as a result of combining 500 mg kg^?1Bti and 1g L^?1 spray applications. Treatment with Bti caused significant reductions in the emergence (up to 74%) of house fly adults compared to the control. The fact that the emergence of adult house flies was affected by Bti treatments implies that Bti has sublethal effects on house fly larvae. The cost–benefit analysis (expressed in terms of mortality of larvae growing) indicated that the most effective combination for house fly larvae and adult house fly emergence control was the 500 mg kg^?1 of feed and 2 g L^?1 spray application combination that resulted in 67% larval mortality and a 74% decrease in adult house fly emergence. This study presents commercial users with various alternatives for possible combinations of the two Bti formulations.     

Paraiotonchium muscadomesticae n. sp. (Tylenchida: lotonchiidae) a Parasite of the House Fly (Musca domestica) in Brazil and a Key to Species of the Genus Paraiotonchium

Paraiotonchium muscadomesticae n. sp., a parasite of the house fly, Musca domestica L., is described and illustrated from material collected in Brazil. The life cycle of P. muscadomesticae is similar to that of P. autumnale (Nickle), consisting of alternating gamogenetic and parthenogenetic generations. Paraiotonchium muscadomesticae n. sp. can be distinguished from P. nicholasi Slobodyanyuk, P. autumnale (Nickle) Slobodyanyuk, and P. crassirostris (Yatham &Rao) Siddiqi by the shorter body length of young heterosexual females, 652 g.m (530-709) for P. muscadomesticae compared to 750 μm or more (801-1,050) for the others. Paraiotonchium muscadomesticae is close to P. nicholosi but differs from it by V ratio and spicule length (V = 80-84; spicule = 16-21 p.m in P. muscadomesticae compared to V = 73-78; spicule = 25-35 μm in P. nicholasi). Paraiotonchium muscadomesticae and P. nicholasi differ from all species of this genus by the absence of a bursa on males of these two species.