Delia Radicum Research Articles

Effectiveness of insecticides against pests of white cabbage grown using seedling technology

Among the two methods of growing white cabbage, the seedling technology is more widely used in North-Western Russia. Watering seedlings in cassettes with a systemic formulation of neonicotinoid insecticide Actara, WDG (250 g/kg thiamethoxam) prior to planting has been developed to protect white cabbage from early spring pests: flea beetles of the genus of Phyllotreta and the cabbage root fly. This approach is widely used by commercial growers and its efficacy requires monitoring under current conditions because of a possibility of resistance development. Testing Actara, WDG in 2019 and 2021 at the experimental field of All-Russian Institute of Plant Protection didn’t show any significant decrease of biological effectiveness of seedling treatment. Testing biological effectiveness of systemic insecticides belonging to the chemical class of carbamates Lannate, WSP (250 g/kg metomil) and the new class isoxazolines isocycloseram was carried out in parallel. Biological effectiveness of the latter insecticide was higher compared to Actara against the flea beetles and the cabbage root fly during a 21-day period. In addition, plant infestation with diamondback moth decreased. Efficacy indices of Lannate were significantly lower. Isocycloseram shows a good potential for inclusion into the Index of Registered Formulations of the Russian Federation to protect cabbage against a complex of insect pests. Having an additional active ingredient available to farmers will be begenicial for developing rotation schemes to combat pest resistance.

Genome analysis of cabbage root fly for targeted pest management

Genome analysis of cabbage root fly for targeted pest management

A high-quality functional genome assembly of Delia radicum L. (Diptera: Anthomyiidae) annotated from egg to adult.

Belowground herbivores are overseen and underestimated, even though they can cause significant economic losses in agriculture. The cabbage root fly Delia radicum (Anthomyiidae) is a common pest in Brassica species, including agriculturally important crops, such as oilseed rape. The damage is caused by the larvae, which feed specifically on the taproots of Brassica plants until they pupate. The adults are aboveground-living generalists feeding on pollen and nectar. Female flies are attracted by chemical cues in Brassica plants for oviposition. An assembled and annotated genome can elucidate which genetic mechanisms underlie the adaptation of D. radicum to its host plants and their specific chemical defences, in particular isothiocyanates. Therefore, we assembled, annotated and analysed the D. radicum genome using a combination of different next-generation sequencing and bioinformatic approaches. We assembled a chromosome-level D. radicum genome using PacBio and Hi-C Illumina sequence data. Combining Canu and 3D-DNA genome assembler, we constructed a 1.3Gbp genome with an N50 of 242Mbp and 6pseudo-chromosomes. To annotate the assembled D. radicum genome, we combined homology-, transcriptome- and ab initio-prediction approaches. In total, we annotated 13,618genes that were predicted by at least two approaches. We analysed egg, larval, pupal and adult transcriptomes in relation to life-stage specific molecular functions. This high-quality annotated genome of D. radicum is a first step to understanding the genetic mechanisms underlying host plant adaptation. As such, it will be an important resource to find novel and sustainable approaches to reduce crop losses to these pests.

Leaf-chewing herbivores affect preference and performance of a specialist root herbivore

Plants interact with a diversity of phytophagous insects above- and belowground. By inducing plant defence, one insect herbivore species can antagonize or facilitate other herbivore species feeding on the same plant, even when they are separated in space and time. Through systemic plant-mediated interactions, leaf-chewing herbivores may affect the preference and performance of root-feeding herbivores. We studied how six different leaf-chewing herbivore species of Brassica oleracea plants affected oviposition preference and larval performance of the root-feeding specialist Delia radicum. We expected that female D. radicum flies would oviposit where larval performance was highest, in accordance with the preference–performance hypothesis. We also assessed how the different leaf-chewing herbivore species affected defence-related gene expression in leaves and primary roots of B. oleracea, both before and after infestation with the root herbivore. Our results show that leaf-chewing herbivores can negatively affect the performance of root-feeding D. radicum larvae, although the effects were relatively weak. Surprisingly, we found that adult D. radicum females show a strong preference to oviposit on plants infested with a leaf-chewing herbivore. Defence-related genes in primary roots of B. oleracea plants were affected by the leaf-chewing herbivores, but these changes were largely overridden upon local induction by D. radicum. Infestation by leaf herbivores makes plants more attractive for oviposition by D. radicum females, while decreasing larval performance. Therefore, our findings challenge the preference–performance hypothesis in situations where other herbivore species are present.

Psila rosae (carrot root fly)

Psila rosae (carrot root fly)

Psila rosae (carrot root fly)

This datasheet on Psila rosae covers Identity, Overview, Distribution, Dispersal, Hosts/Species Affected, Diagnosis, Biology & Ecology, Natural Enemies, Impacts, Prevention/Control, Further Information.

Impact of Verimark, Radiant SC, and SPE-120 Against Cabbage Maggot in Radish, 2019

Impact of Verimark, Radiant SC, and SPE-120 Against Cabbage Maggot in Radish, 2019

Impact of Selected Insecticides Against Cabbage Maggot, Cabbage Looper, and Crucifer Flea Beetle Management in Broccoli, 2021

Impact of Selected Insecticides Against Cabbage Maggot, Cabbage Looper, and Crucifer Flea Beetle Management in Broccoli, 2021

How Predict Bean Production According to Complex Interactions between Bean Growth, Fusarium and Rhizoctonia Root Rots, Fly and Weed Development Under Different Planting Dates and Weed Control Treatments?

How Predict Bean Production According to Complex Interactions between Bean Growth, Fusarium and Rhizoctonia Root Rots, Fly and Weed Development Under Different Planting Dates and Weed Control Treatments?

Integrirani pristup zaštiti mrkve od dva značajna štetnika – mrkvine muhe i mrkvine cistolike nematode

Carrots are among the top ten vegetable crops in the world, with an annual world production of about 428 million tonnes grown on about 11.5 million hectares. The investment per unit area is not high and with good cultivation techniques yields of up to 50 t/ha can be achieved, together with major economic benefits from winter cultivation. During the growing season, carrots are susceptible to numerous pests. The most important are the carrot root fly (Psila rosae, Fabricius), whose root-feeding fly larvae reside in the soil or plant tissue, and the carrot cyst nematode (Heterodera carotae Jones), which is responsible for the decline of carrots in many countries and requires strict sanitation measures if crops are infected. As insecticides become less available in Europe, the appropriate use of non-chemical methods in integrated pest management (IPM) needs to be emphasised, highlighting the importance of developing new tolerant varieties. This review addresses the approaches to monitor and predict the occurrence of two important carrot pests and the main control measures according to the strategies of IPM.

Shoot and root insect herbivory change the plant rhizosphere microbiome and affects cabbage-insect interactions through plant-soil feedback.

Summary Plant–soil feedback (PSF) may influence plant–insect interactions. Although plant defense differs between shoot and root tissues, few studies have examined root‐feeding insect herbivores in a PSF context. We examined here how plant growth and resistance against root‐feeding Delia radicum larvae was influenced by PSF.We conditioned soil with cabbage plants that were infested with herbivores that affect D. radicum through plant‐mediated effects: leaf‐feeding Plutella xylostella caterpillars and Brevicoryne brassicae aphids, root‐feeding D. radicum larvae, and/or added rhizobacterium Pseudomonas simiae WCS417r. We analyzed the rhizosphere microbial community, and in a second set of conspecific plants exposed to conditioned soil, we assessed growth, expression of defense‐related genes, and D. radicum performance.The rhizosphere microbiome differed mainly between shoot and root herbivory treatments. Addition of Pseudomonas simiae did not influence rhizosphere microbiome composition. Plant shoot biomass, gene expression, and plant resistance against D. radicum larvae was affected by PSF in a treatment‐specific manner. Soil conditioning overall reduced plant shoot biomass, Pseudomonas simiae‐amended soil causing the largest growth reduction.In conclusion, shoot and root insect herbivores alter the rhizosphere microbiome differently, with consequences for growth and resistance of plants subsequently exposed to conditioned soil.

Challenging the Preference-Performance Hypothesis in an above-belowground insect.

The relationship between female oviposition preference and offspring performance has been a question of special interest in the study of host plant selection by phytophagous insects. The Preference-Performance Hypothesis (PPH) is one of the main hypotheses proposed to explain this relationship, stating that females should preferentially lay eggs on plants providing the best larval development. The PPH has been extensively tested on aboveground insects but its application to species with belowground larvae is still mostly unknown. In this study, the PPH was quantitatively tested in an above-belowground insect, the cabbage root fly Delia radicum. Female oviposition preference and larval performance were estimated on three brassicaceous species (Brassica oleracea, Brassica rapa, and Sinapis alba) as well as between four cultivars of B. rapa and four cultivars of S. alba. Larval performance was estimated through their survival and through three life-history traits (LHT) of emerging adults. The PPH was supported at the intraspecific scale but only in B. rapa and for some, but not all, of the life-history traits. No support for the PPH was found in S. alba as well as at the interspecific scale. This study pleads for the integration of insects with both above- and belowground life stages in the preference-performance debate. Moreover, it raises the importance of measuring several variables to estimate larval performance and to test the PPH quantitatively, both at the plant intraspecific and interspecific scales, before drawing general conclusions.

Influential Insider: Wolbachia, an Intracellular Symbiont, Manipulates Bacterial Diversity in Its Insect Host.

Facultative intracellular symbionts like the α-proteobacteria Wolbachia influence their insect host phenotype but little is known about how much they affect their host microbiota. Here, we quantified the impact of Wolbachia infection on the bacterial community of the cabbage root fly Delia radicum by comparing the microbiota of Wolbachia-free and infected adult flies of both sexes. We used high-throughput DNA sequencing (Illumina MiSeq, 16S rRNA, V5-V7 region) and performed a community and a network analysis. In both sexes, Wolbachia infection significantly decreased the diversity of D. radicum bacterial communities and modified their structure and composition by reducing abundance in some taxa but increasing it in others. Infection by Wolbachia was negatively correlated to 8 bacteria genera (Erwinia was the most impacted), and positively correlated to Providencia and Serratia. We suggest that Wolbachia might antagonize Erwinia for being entomopathogenic (and potentially intracellular), but would favor Providencia and Serratia because they might protect the host against chemical plant defenses. Although they might seem prisoners in a cell, endocellular symbionts can impact the whole microbiota of their host, hence its extended phenotype, which provides them with a way to interact with the outside world.

Identification of morphologically challenging Delia (Diptera: Anthomyiidae) species from field vegetable crops using polymerase chain reaction–restriction fragment length polymorphism (PCR-RFLP)

AbstractRoot feeding by the larvae of multiple Delia species can lead to economic loss in many agricultural crops. Field vegetables are subject to infestations by a species complex composed of Delia radicum (Linnaeus) (Diptera: Anthomyiidae), a pest in brassica crops (Brassicaceae), Delia antiqua (Meigen), believed to cause the majority of crop damage in onions, and the generalists Delia florilega (Zetterstedt), Delia platura (Meigen), and Botanophila fugax (Meigen) (Diptera: Anthomyiidae). Correct species identification is necessary to implement field management strategies, but these species are challenging to identify morphologically. We propose a polymerase chain reaction–restriction fragment length polymorphism method as a molecular tool to distinguish between five species of Delia and between two genetic lines of D. platura. The mitochondrial DNA cytochrome c oxidase subunit 1 barcode fragment is targeted, then the polymerase chain reaction product digested with four different restriction enzymes (AccI, BsrI, MlyI, and StyI). The BsrI enzyme distinguishes the two genetic lines of D. platura and D. florilega. The MlyI enzyme identifies B. fugax from the Delia species. Combining BsrI, StyI, AccI, and MlyI into double digestion reactions allows for rapid diagnostics among the species tested. Our method was validated using DNA from specimens collected in eastern Canada. This method provides tools in ecological and environmental studies where these species are of interest.

Connection between Nutrient Content and Resistance to Selected Pests Analyzed in Brassicaceae Hybrids

Rapeseed (Brassica napus L. ssp. oleifera Metzg) is attacked by a wide range of pests. Breeding of resistant cultivars is one of the best methods of protecting crops against insects, and non-cultivated species of Brassicaceae can be used as resistance donors. In this study, we investigated the relationship between nutrient content and resistance to two commonly occurring pests (Delia radicum and Brevicoryne brassicae) in 12 Brassicaceae hybrid combinations. The experiment was conducted at Poznań University of Life Sciences Experimental Station located in Dłoń. The assessment was carried out for three years (2017, 2018, and 2019) on randomly chosen individuals in two growth stages: vegetative stage and flowering stage. The resistance to B. brassicae and D. radicum was observed in all three years, however, macronutrient and micronutrient contents as well as total nitrogen, total sulfur, and sulfur sulfate were observed only in 2019. Statistically significant negative association between Ca and resistance to B. brassicae and D. radicum was discovered. Additionally, positive association between Cu and resistance to B. brassicae was observed. The importance of selected mineral elements in plant resistance is widely discussed.

Root-associated entomopathogenic fungi manipulate host plants to attract herbivorous insects

Root-associated entomopathogenic fungi (R-AEF) indirectly influence herbivorous insect performance. However, host plant-R-AEF interactions and R-AEF as biological control agents have been studied independently and without much attention to the potential synergy between these functional traits. In this study, we evaluated behavioral responses of cabbage root flies [Delia radicum L. (Diptera: Anthomyiidae)] to a host plant (white cabbage cabbage Brassica oleracea var. capitata f. alba cv. Castello L.) with and without the R-AEF Metarhizium brunneum (Petch). We performed experiments on leaf reflectance, phytohormonal composition and host plant location behavior (behavioral processes that contribute to locating and selecting an adequate host plant in the environment). Compared to control host plants, R-AEF inoculation caused, on one hand, a decrease in reflectance of host plant leaves in the near-infrared portion of the radiometric spectrum and, on the other, an increase in the production of jasmonic, (+)-7-iso-jasmonoyl-l-isoleucine and salicylic acid in certain parts of the host plant. Under both greenhouse and field settings, landing and oviposition by cabbage root fly females were positively affected by R-AEF inoculation of host plants. The fungal-induced change in leaf reflectance may have altered visual cues used by the cabbage root flies in their host plant selection. This is the first study providing evidence for the hypothesis that R-AEF manipulate the suitability of their host plant to attract herbivorous insects.

Differential effects of the rhizobacterium Pseudomonas simiae on above‐ and belowground chewing insect herbivores

AbstractPlant growth‐promoting rhizobacteria (PGPR) can enhance plant growth and defence. Via plant‐mediated effects, PGPR have been reported to impact the performance of generalist leaf‐chewing insects either negatively or positively. However, only a few insect species, mainly feeding on aboveground tissues, have thus far been investigated. Here, we investigated how addition of rhizobacteria to the soil in which cabbage plants are growing affects the performance of three chewing insect herbivores, two leaf chewers and one root feeder. In a greenhouse experiment, we grew white cabbage (Brassica oleracea) plants in soil supplemented with and without the rhizobacterium Pseudomonas simiae WCS417r. We investigated the consequences for three important insect pests of Brassica species, larvae of the cabbage moth Mamestra brassicae, the diamondback moth Plutella xylostella, or the cabbage root fly Delia radicum after 5 weeks of plant growth. We recorded aboveground plant biomass, insect biomass, plant defence marker gene expression levels and plant defence‐related hormone concentrations. Rhizobacterial inoculation increased aboveground plant biomass in non‐infested plants but not in infested plants. Rhizobacterial inoculation affected insect performance differently: on PGPR‐inoculated plants biomass of Plutella xylostella was lower, while biomass of Delia radicum was higher than on control plants. However, no effect was found on Mamestra brassicae biomass. Rhizobacterial inoculation increased the expression of the defence marker gene LOX2 in P. xylostella‐infested plants and MYC2 in M. brassicae‐infested plants. Transcription levels of the plant defence marker gene PAL1 showed upregulation between inoculated and non‐inoculated insect‐free plants. Levels of the phytohormones jasmonic acid, salicylic acid and abscisic acid were similar in inoculated and non‐inoculated plants. We conclude that rhizobacterial inoculation has potential to be applied in the protection of cabbage crops against the diamondback moth whereas this does not apply to reducing damage caused by the cabbage moth or cabbage root fly.

PP 1/259 (2) Delia radicum on oilseed rape

Specific scopeThis Standard describes the conduct of trials for the efficacy evaluation of insecticides against Delia radicum on oilseed rape. The EPPO Standard PP 1/009 specifically addresses Delia radicum in vegetable brassicas.Specific approval and amendmentFirst approved in 2007‐09.First revision approved in 2020‐09.

Volatiles from the fungus Fusarium oxysporum affect interactions of Brassica rapa plants with root herbivores

1. Soil is a diverse and heterogeneous environment where chemicals mediate numerous interactions between soil organisms and plants. To date, studies have extensively addressed volatile‐mediated interactions between soil microorganisms and the effects of microbial volatiles on plant growth. Yet, to our knowledge, it remains to be explored whether volatiles from soil‐borne fungi can influence plant interactions with root herbivores, facilitating or hampering performance of competitors that share the same host plant.2. In the present study, we investigated the effects of volatiles emitted by the soil‐borne fungus Fusarium oxysporum on the performance of two root herbivores: the plant parasitic cyst nematode, Heterodera schachtii, and the insect root herbivore, Delia radicum, upon infestation of Brassica rapa roots.3. Fungal volatiles slowed down the development of the root nematode cysts but increased their size, suggesting an enhanced egg load. In contrast, the performance of the insect root herbivore was unaffected by the exposure of roots to fungal volatiles. Additionally, fungal volatiles promoted the growth of plants infested with the root nematode, but not of those infested with the insect root herbivore.4. Together, our data show that volatiles from a soil‐borne fungus can affect root interactions with root herbivores. Increased production of nematode eggs and plant growth promotion suggest a specific modulation of root‐herbivore interactions by fungal volatiles.

Relationships among root maggot (Delia spp., Diptera: Anthomyiidae) infestation, root injury, and seed yields of canola Brassica napus L. and Brassica rapa L.

This study investigated the relationships between numbers of Delia species (Delia spp. Rob.-Desv., Diptera: Anthomyiidae) flies or eggs and root injury levels of Brassica napus L. and Brassica rapa L. (Brassicaceae) canola (oilseed rape), and between root injury levels and canola seed yields. Wild-collected Delia species adult flies or laboratory-obtained Delia radicum (L.) eggs were introduced into laboratory or field cages containing B. napus or B. rapa plants. The degree of root injury was strongly associated with infestation level using both flies and eggs. Linear response curves between numbers of Delia flies and root injury levels and quadrilinear response curves between numbers of D. radicum eggs and root injury levels showed that root damage increased with increasing levels of infestation; at high egg infestation levels, root damage levelled off in both Brassica species. Seed yield was not clearly related to fly or egg infestation rate, nor to ensuing root damage. No consistent yield relationship in B. napus ‘AC Excel’ was found with levels of root damage seen in the investigation. Conversely, B. rapa cultivar ‘AC Boreal’ seed yields tended to increase above uninfested controls when feeding damage was light but decreased with increased root injury. Despite procedures used to prevent infestation in Delia-free control cages, some root maggot damage was found in control cages in all 4 yr of the field study. Changes in climate, land use patterns, and cropping systems could influence the economic impact of this pest complex on canola in the future.