Effect of beetle size on predation of cabbage root fly eggs by ground beetles

Laboratory studies were done to determine the numbers of cabbage root fly (Delia radicum L.) (Diptera: Anthomyiidae) eggs eaten by sixty species of ground beetles (Coleoptera: Carabidae) collected from a range of habitats. For 35 species that were between 2.7 mm and 10 mm long, there was a linear relationship between the numbers of eggs eaten and beetle length. For each 1 mm increase in length above 2.7 mm, an additional 18 eggs were eaten/beetle/day. Eight further species within the above size range did not eat any fly eggs, as these species are known to be either phytophagous or to feed on moving prey. Large numbers of eggs were eaten by beetles in 13 of the 25 genera tested. Based on size, maximum numbers of eggs were eaten by 7 species of Agonum Bonelli, 5 species of Amara Bonelli and seven species of Bembidion Latreille. Only one of the 6 species of Pterostichus Bonelli tested, P. strenuus (Panz.), ate the expected numbers of eggs, the other species being too large to feed from such small prey items as cabbage root fly eggs. The numbers of beetles larger than 10 mm that ate eggs was highly variable and so 10 mm was considered the upper size limit of carabid predators of cabbage root fly eggs.     

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.     

Female meiosis in the onion fly and cabbage root fly (Diptera: Anthomyiidae).

The sequence of female meiosis was investigated in two populations of the cabbage root fly (Delia radicum) and three populations of the onion fly (D. antiqua). In contrast with the completely achiasmate males, both species showed high levels of recombination in females. However, significant differences in chiasma frequency occurred between individuals within populations and between the populations. It was not uncommon to find aneuploidy of the X chromosomes. The autosomes occasionally showed asynapsis or desynapsis, but normal disjunction of univalents was facilitated by distance pairing.     

Comparison of the sensitivity of four Delia species to host and non-host plant compounds

Abstract. The behavioural facilitation hypothesis, tested in the present study, suggests that evolution of host-plant shifts by phytophagous insects is based on the preadaptation of insects to the chemistry of potentially novel plant hosts. Thus, closely-related insects should have similar sensitivities to compounds that are shared by different host plants. The chemoreception is investigated for four phytophagous flies, Delia radicum, Delia floralis, Delia antiqua and Delia platura (Diptera, Calyptratae: Anthomyiidae), belonging to the same genus but developing mainly on different plant families, with particular secondary plant compound profiles. In addition, the carrot fly, Psila rosae, an acalyptrate Diptera, is included as an unrelated species that is associated with completely different host plants. For the comparison, the known oviposition stimulants of the cabbage root fly (glucobrassicin, sinalbin, sinigrin and a thia-triaza-fluorene compound; CIF-1) present on the cabbage leaf surface were chosen. Responses from prothoracic tarsal sensilla are recorded to contact stimulation in a dose-dependent manner. Among the different flies tested, only D. radicum responds to all the compounds. By contrast, D. floralis is only sensitive to CIF-1, and not specifically on the C₅ sensillum, a finding that is in conflict with previously published results. This discrepancy is possibly an indication of the variability among flies originating from different cultures or habitats. With the exception of sinigrin at high concentration, the various compounds tested do not stimulate D. antiqua or D. platura. However, the carrot fly appears to be completely insensitive to sinigrin even at the highest tested concentration of 10⁻¹ M. The responses of the contact-chemoreceptor neurones to the selected compounds therefore provide little evidence of common sensitivities that would explain host shift in Delia species and specialization at the physiological level. The wide divergence within closely-related species and rearing cultures appears to indicate that the sensitivity and distribution of sensory receptor neurones is very variable on an evolutionary scale.     

Bean seed fly (Delia platura, Delia florilega) and onion fly (Delia antiqua) incidence in England and an evaluation of chemical and biological control options

Bean seed fly and onion fly are significant pests of alliaceous crops in the UK. Their activity was monitored using yellow water traps at three field sites in England in 2002 and 2003. Bean seed fly were not split between Delia platura or Delia florilega because from the growers point of view control measures are independent of species. The traps were effective at catching bean seed fly, which was present from April until September. A total of 1729 bean seed fly were trapped in 2002 and 4501 in 2003, with peak activity in May in both years. In 2003, there appeared to be three to four peaks in abundance of the pest. Only 113 onion flies were trapped in 2002 and 23 in 2003. More male onion fly were trapped than females. Pot experiments were carried out to evaluate efficacy of a range of insecticides, garlic and two parasitic nematode species (Steinernemafeltiae and Steinernema kraussei) against bean seed fly and onion fly. Pots of salad onions were exposed to natural oviposition by bean seed fly, but the onion fly experiment was carried out in a glasshouse with eggs of the pest being inoculated into the pots. Tefluthrin seed treatment appeared to be especially effective at preventing bean seed fly damage and produced the most robust seedlings but did not appear to kill the larvae. A drench of chlorpyrifos at the ‘crook’ stage gave 100% control of bean seed fly larvae. A chlorpyrifos drench was the only treatment to give effective control of onion fly. There was some evidence that the parasitic nematode S. feltiae reduced numbers of bean seed fly larvae by about 50%. Guidelines for control of both bean seed fly and onion fly are discussed.     

The development of the bean seed fly <Emphasis Type="Italic">Delia platura</Emphasis> Mg. (Diptera,Anthomyiidae) and its harmfulness in forest-steppe agrocenoses of Samara Province

Delia platura Mg. is a polyphagous and polyvoltinic Holarctic species feeding mainly on booting cereals and seedling roots. In Samara Province, three generations of the species develop annually; the species hibernates as puparia in soil under winter crops at a depth of 10–20 cm; adults emerge during the first ten days of May. Most of all, the fly infests barley and winter wheat, preferring crop rotation systems with green-manure fallow and causing 2.6–7.2% yield loss.     

The influence of plant age on resistance of radish to cabbage root fly egg-laying

Cabbage root fly ( Delia brassicae ) egg-laying around radish plants ranging in age from newly emerged seedlings to plants with flowering shoots was studied in the field and laboratory. The attractiveness of radish changed with age, one peak in egg-laying occurring just before plants were of marketable size and further peaks as they produced flowering shoots. The pattern of egg-laying was similar for the six radish cultivars tested, both in the field and laboratory, irrespective of whether flies did or did not have a choice of plants of different ages. At any one age, there was no correlation between egg-laying and plant size. Selection within radish cultivars for the extremes of the range of egg-laying preference appeared to alter the cycle of attractiveness of different radish stocks to cabbage root fly, the response being influenced by environmental conditions.     

A comparative study of the interaction of the cholinesterase from the brain of the cabbage fly, the acetylcholinesterase from bovine erythrocytes and the butyrylcholinesterase from horse blood serum with organophosphorus inhibitors

Studies have been made of the effect of several organophosphorus inhibitors, R1(R2)P(O) . SCH2CH2SR and R1(R2)P(O)SCH2CH2SRR . -O4SCH3 (or -I), which differ by the structure of split (R, P) and phosphoryl (R1, R2) parts of the molecule, on cholinesterase (ChE) from the brain of the fly Delia brassicae, acetylcholinesterase (AChE) of the bovine erythrocytes and butyrylcholinesterase (BuChE) from the blood serum of the horse. For fly ChE, higher values of a constant (kII) of the inhibition rate (at pH 7.5 and temperature 25 degrees C) were obtained both with thiophosphates and with thiophosphonates. This finding reveals higher reactivity of the active centre of this enzyme, as well as significantly lower selectivity of the latter to the structure of organophosphorus inhibitors. The data obtained suggest the existence of differences in the size of hydrophobic regions of anionic and esterase parts of the active centre in ChE of the fly and AChE of mammals, as well as the existence of some similarity between ChE of the fly and BuChE.     

A glasshouse screening method to assess resistance in onions to damage by onion fly (Delia antiqua) larvae

Factors influencing the resistance of onion (Allium cepa) cultivars to onion fly (Delia antiqua) damage were investigated. These included different environments, methods of plant raising and egg inoculation, and plant size. A glasshouse compartment maintained at 14 to 37 °C was as satisfactory for assessing the resistance as a controlled environment. The basic test unit comprised 10 onion seedlings raised in a 400 × 50 × 50 mm deep plastic trough and inoculated with 50 onion fly eggs from a laboratory culture. Resistance was assessed by counting wilted plants every two or three days for 21 days after egg inoculation. The reciprocal of number of days for each plant to wilt (wilting rate) was an appropriate variate for statistical analysis, adjusted for the length of the longest leaf at the time of inoculation. The method enables cultivars or breeding lines of onion species to be reliably screened for resistance to larvae of this pest in a glasshouse so that only the most promising need be tested in the field.     

Host-stage selection by Trybliographa rapae, a parasitoid of the cabbage root fly Delia radicum

Host-stage selection by Trybliographa rapae Westwood (Hymenoptera: Figitidae) was studied in choice and no-choice experiments in the laboratory. The parasitoid was able to reproduce in first, second, and third instars of the cabbage root fly, Delia radicum L. (Diptera: Anthomyiidae), but oviposition occurred more frequently in third instars when all three developmental stages were offered simultaneously. Oviposition in third instars increased the rate of development of offspring and their body size, but did not alter sex ratio. Results are discussed in the light of predictions made by the theory of optimal host acceptance.     

Neuropeptides associated with the central nervous system of the cabbage root fly, Delia radicum (L)

The peptidome of the central nervous system of adult cabbage root fly, Delia radicum (L) was investigated using matrix assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF MS). Over twenty neuropeptides were identified from three different tissue sources, the combined brain/suboesophageal ganglion (SOG), the retrocerebral complex, and the thoracic-abdominal ganglion (TAG). A number of peptides were identified in all three tissues, including allatostatins, short neuropeptide F-like peptides, corazonin, a pyrokinin, and a myosuppressin. Adipokinetic hormone was restricted to the retrocerebral complex. Other peptides, including FMRFamides and sulfakinins were detected only in the brain/SOG and TAG. Some peptides, notably myoinhibitory peptides and tachykinins, which have been identified in other fly species, were not detected in any tissue sample. This study has structurally characterized for the first time, the neuropeptides from adult D. radicum.     

A relationship between dry matter and damage by larvae of the turnip root flyDelia floralis in cultivars of the swedish turnipBrassica napus

A series of trials from 1981–85 investigating the amount of damage caused by larvae of the turnip root flyDelia floralis (Fallen) to cultivars of Swedish turnipBrassica Napus (L.) of varying percentages of dry matter indicated that those of high dry matter were damaged less than low dry matter cultivars. Pupal numbers of turnip root fly gave good correlations with damage but there was no relationship between damage and cabbage root fly pupae.     

Morphology of the antennal sensilla of the cabbage root fly,Delia radicum L. (Diptera : Anthomyiidae)

The antennal sensilla of Delia radicum L. (Diptera : Anthomyiidae) were studied by scanning electron microscopy. On the scape and pedicel, grooved socketed bristles and setiferous plaques were found. There are 4 types of surface sensilla on the funicle: trichoid, basiconic, clavate, and grooved. Their numbers and distribution are described. There are 3–4 single-chambered pits on the dorsal surface of the funicle of both sexes and these contain basiconic sensilla. On the ventral surface, there is one multi-chambered pit, which contains 5 types of sensilla: grooved s., smooth-walled conical s., smooth-walled tapered s., striated s. and a novel type, flattened sensilla. These results are compared with previously published studies on several other fly species.     

Tolerance and antibiosis resistance to cabbage root fly in vegetable Brassica species

Four accessions of the wild species Brassica fruticulosa Cyrillo (Brassicaceae) were studied in order to identify its tolerance and antibiosis resistance to the cabbage root fly, Delia radicum L. (Diptera: Anthomyiidae), in comparison to a widely cultivated cauliflower cultivar and a rapid cycling Brassica oleracea L. line. Antibiosis was prominent, as the insects reared on resistant accessions showed reduced individual pupal weight, total pupal weight, adult dry weight, and the longest average fly eclosion time. Host plant resistance, however, did not affect the sex ratio of adult flies. A study of the root architecture of plants with and without root fly inoculation revealed differences in the structure within B. oleracea accessions. A long main root and a high number of lateral roots appeared to be important characteristics for a Brassica type, with a higher tolerance level to cabbage root fly attack.     

A technique for measuring the susceptibility of wheat bulb fly larvae to insecticides in the laboratory

A simple assay is described for measuring the toxicity of insecticides to larvae of wheat bulb fly (Delia coarctata) in the laboratory. The method should be suitable for other small soil insect larvae that cannot be obtained in large numbers and are difficult to treat and confine. A limitation of the technique is that it works only with insecticides that are soluble enough to be toxic in aqueous solution.     

Aleochara suffusa andA. bilineata (Col.: Staphylinidae) as parasitoids of brassica root flies in northern Norway

A sample ofDelia puparia collected in late autumn from a brassica field at Tromsø, northern Norway, was investigated to study the level of parasitism byAleochara. BothA. suffusa andA. bilineata were reared from puparia of the cabbage root fly,Delia radicum, and the bean seed flies,D. florilega and/orD. platura. Only two specimens ofA. bilineata emerged from puparia of the turnip root fly,D. floralis. BothAleochara species hibernated in the larval state and both pupated inside the host puparium. Most specimens ofA. suffusa emerged from small hosts (D. florilega/D. platura), whereas the majority of A.bilineata emerged from host species of larger size (D. radicum/D. floralis). The time to develop from first instar larva to adult was similar for bothA. suffusa andA. bilineata. Parasitoids developing in large hosts emerged later than those in small hosts, the delay being the same for both species ofAleochara.     

大蒜种质资源对蒜蛆的抗性评价

就大蒜种质资源对蒜蛆的抗性进行了虫圃田间鉴定,并对抗性与大蒜主要植物学性状和大蒜辣素含量的相关性进行了分析。结果表明:52份材料的感虫指数分布在7.14~90.38之间,种质资源间抗虫性差异达到了显著水平;聚类分析并结合感虫指数将52份种质资源分为高抗、抗、中抗、中感、感、高感6个类别,其中高抗和抗性材料分别为4份和8份。相关分析表明:感虫指数与植株的7个形态数量性状的相关性均未达到显著水平,而与鳞茎的鳞芽背宽、鳞茎的大蒜辣素含量均呈极显著的负相关,即抗性与二者显著正相关。表明大蒜辣素含量越高,大蒜对蒜蛆的抗性越强;从鳞芽背宽较宽和高大蒜辣素含量的大蒜资源中筛选抗蒜蛆的种质可能性更大。     

Specificity of accessory gland extracts. in three Delia fly species (Diptera: Anthomyiidae)

Abstract. Extracts of testes and male accessory (paragonial) glands made from three species of Delia (onion fly {D.antiqua) , seedcorn fly (D.platura) , and cabbage fly (D.radicum)) were injected into conspecific virgin females. Extracts of paragonial glands, but not testes, from onion, seedcorn and cabbage fly males stimulated oviposition and suppressed mating when injected into conspecific virgin females. When extracts of paragonial glands from males of these species were injected into heterospecific virgin females, the extracts of D.antiqua and D.platura were fully cross-reactive with respect to oviposition; interspecific injection stimulated oviposition at the level of the conspecific mated controls. Injection of D.radicum extract fully activated the D.antiqua and D.platura ovipositional response. D.antiqua extract caused mating inhibition and partial oviposition in D.radicum; that of D.platura had no effect on either oviposition or mating inhibition in D.radicum. These results suggest that D.antiqua and D.platura are more closely related to one another than either is to D.radicum , and agree with published anatomically-based phylogenies and a genetic distance calculation based on eight enzyme loci. The occurrence of sex peptide cross-reactivity, though asymmetrical, between D.radicum versus D.antiqua and D.platura indicates that, functionally, sex peptides have changed little during the evolution of this genus. An emerging pattern of broad cross-reactivity within genera suggests that sex peptides are not an initiator of reproductive isolation.     

Sequential Utilization of Hosts from Different Fly Families by Genetically Distinct,Sympatric Populations within the Entomophthora muscae Species Complex

The fungus Entomophthora muscae (Entomophthoromycota, Entomophthorales, Entomophthoraceae) is a widespread insect pathogen responsible for fatal epizootic events in many dipteran fly hosts. During epizootics in 2011 and 2012 in Durham, North Carolina, we observed a transition of fungal infections from one host, the plant-feeding fly Delia radicum, to a second host, the predatory fly Coenosia tigrina. Infections first appeared on Delia in the middle of March, but by the end of May, Coenosia comprised 100% of infected hosts. Multilocus sequence typing revealed that E. muscae in Durham comprises two distinct subpopulations (clades) with several haplotypes in each. Fungi from either clade are able to infect both fly species, but vary in their infection phenologies and host-specificities. Individuals of the more phylogenetically diverse clade I predominated during the beginning of the spring epizootic, infecting mostly phytophagous Delia flies. Clade II dominated in late April and May and affected mostly predatory Coenosia flies. Analysis of population structure revealed two subpopulations within E. muscae with limited gene exchange. This study provides the first evidence of recombination and population structure within the E. muscae species complex, and illustrates the complexity of insect-fungus relationships that should be considered for development of biological control methods.     

Community structure of Anthomyiidae (Diptera) of six peat-bogs in the ?umava Mts (Czech Republic)

The species composition of the family Anthomyiidae in six peat-bogs in the Šumava Mts is analysed with regards to dominance, constancy, seasonal occurrence and type of distribution of each species. Anthomyiid communities in all sites are compared based on the number of species, species richness, diversity and equitability indices, as well as coefficients of similarity and Principal Components Analysis (PCA). Three collecting methods are compared: yellow pan water traps (439 specimens/43 species), sweeping (93/18) and Malaise traps (97/22). Three species, Pegoplata aestiva (24.17%), Delia platura (14.47%), and Hylemya nigrimana (11.29%) were eudominant, two further species were dominant: Delia cardui (8.74%) and Botanophila fugax (8.27%). Two species, Botanophilia fugax and Delia platura, were found in all study sites. These species, together with those collected in five sites (Delia cardui, Heterostylodes nominabilis and Hylemya vagans), had a constancy rate higher than 75% and belonged to the category of euconstant species.