Entomopathogenic nematodes (EPNs) play a role in indirect defense of plants under attack by root herbivores. Several investigations have shown that EPNs are attracted or repelled by various volatile ...compounds (VOCs) released from insect damaged plant roots. We hypothesized that the directional responses of EPNs to the VOCs would be affected by foraging strategy and would vary among species, VOC type, and VOC concentrations. We tested the chemotactic responses of four commercial EPN species (Steinernema feltiae, S. carpocapsae, S. kraussei, and Heterorhabditis bacteriophora) to seven compounds released from insect (Melolontha hippocastani)-damaged (decanal, nonanal, octanal, undecane, 6-methyl-5-hepten-2-one, and 1,2,4-trimethylbenzene) and undamaged (2-ethyl-1-hexanol) potato tubers. Our results suggest that EPNs are able to distinguish herbivore-induced VOCs from those that are typical for healthy potato tubers. In our investigation, nonanal, octanal, and decanal had a greater influence on the movement of EPNs than other tested synthetic volatiles. Decanal was an attractant for H. bacteriophora and S. kraussei at both tested concentrations (as a pure compound and at a concentration of 0.03 ppm). The results suggest that the susceptibility to perception of chemical stimuli from the environment is a species-specific characteristic that prevails over the influence of the foraging strategy.
Abstract
In Slovenia, only the native natural enemies of plant pests that are on the EPPO Positive List of biological control agents can be used in agricultural production to control plant pests. The ...List of native species of organisms for biological control, which is an important part of the Regulations on biological control, currently includes a total of 35 species of beneficial insects and mites and entomopathogenic nematodes. Compared to the number of species on the first list that was established in 2006, the number of beneficial species that Slovenian growers of food and ornamental plants can currently use in everyday practice has doubled. This is the result of intensive professional and research work in the investigation of the occurrence and distribution of natural enemy species in Slovenia, which has been systematically supported by the state for many years. Natural enemy species, which are an integral part of the EPPO Positive List of biological control agents, can be included on the list of native biological control species via a special procedure. However, many natural enemy species that are not yet included on the EPPO Positive List have been identified in the period 2007–2022. In this paper, we list 75 such species and we present 5 candidates (Cotesia glomerata L., Diadegma semiclausum Hellen, Anisopteromalus calandrae Howard, Neochrysocharis formosa Westwood and Kampimodromus aberrans Oudemans) that, in our opinion, have high potential as biological controls and will be suitable in the future for mass rearing and use in augmentative biological control.
This paper provides the first detailed presentation of research and professional activities in the field of biological control in Slovenia during the period of 1990–2020. It presents information on ...the important pioneering role of Prof. Dr. Lea Milevoj in biological control research in Slovenia, especially in regard to the inventorying and laboratory rearing of indigenous beneficial organisms, evaluation of the influence of food type on the feeding behaviour of beneficial organisms, participation in the first introduction of a natural enemy within the context of classical biological control in Slovenia, preparation of rules on the biological control of plant pests and publication of the first Slovenian monograph on biological control. The paper also describes the activities of Slovenian researchers in regard to entomopathogenic nematodes, especially related to the assessment of their presence and efficiency in suppressing harmful insects and the identification of indigenous parasitic nematodes associated with economically harmful slugs. The paper also notes some applicative and basic research projects pertaining to parasitoids, especially in terms of their function as natural enemies of aphids, and in regard to predators of harmful insects and mites, especially predatory mites. The main goal of these activities is to implement the use of as many natural enemies as possible in food and ornamental plant production systems to replace the use of plant protection products.
Entomopathogenic nematodes (EPNs) are agents that can be used for the biological control of pests associated with pesticides in a tank mix. Compatibility studies need to be conducted to analyse which ...products are compatible with EPNs. The survival of infective juveniles (IJs) of four species of EPNs (Steinernema, Heterorhabditis) was determined after exposure to eight chemical herbicides. The effect of direct IJs exposure to herbicides for 1, 4 and 24 h was tested in a Petri dish at 15, 20 and 25 °C. The study showed that Steinernema kraussei was the most tolerant among the tested EPN species, while S. carpocapsae was the most sensitive to all tested herbicides. The lowest mortality of IJs was at 15 °C (19%). Our investigation showed, overall, the herbicides negatively affected EPN survival. The results confirmed that the compatibility is a species-specific characteristic, influenced by the temperature and time of exposure. Application of two different control ingredients (insecticide and herbicide) at the same time would reduce cost and time consumption in pest/weed control.
Phasmarhabditis papillosa
is a promising biocontrol agent of gastropods in crops. To enhance the efficacy of mollusc parasitic nematodes, a better understanding of the chemical signalling between ...hosts and parasites is needed. The objective of this research was to test the stimulus–response behaviour of the mollusc parasitic nematode
P. papillosa
towards mucus of the following mollusc species:
Arion vulgaris
,
Limax maximus
,
Deroceras reticulatum
, and
Helix pomatia
. The nematode chemotactic response was observed as directed motility towards mucus of the tested mollusc species at two temperature regimes under laboratory conditions. The motility of
P. papillosa
was more strongly expressed at a higher temperature (20 °C) than at a lower temperature (15 °C). When comparing mucus of different mollusc species, none of the tested molluscs significantly affected the directed motility of
P. papillosa
at the lower temperature (15 °C). At the higher temperature (20 °C), mucus samples from
L. maximus
and
H. pomatia
were observed to be more attractive than those from
A. vulgaris
or
D. reticulatum
for the nematodes. Our results indicate that
P. papillosa
distinguishes among mollusc species by exhibiting a chemotactic response to a signal emanating from mollusc mucus.
Upon herbivore attack, plants produce and emit volatile organic compounds (VOCs). Some of these compounds may be used in defensive strategy namely the attraction of the herbivores natural enemies. To ...increase our knowledge of aboveground-induced VOCs on beneficial organisms, we describe laboratory study on the chemotactic behavior of two-spotted lady beetle (Adalia bipunctata L.) and green lacewing (Chrysoperla carnea Stephens) larvae toward synthetic VOCs (methyl salicylate, (E)-β-farnesene, (E)-β-ocimene, and E-nerolidol) typically emitted by insect-damaged peach cultivars. All tested VOCs influenced the behavior of both tested organisms. Our results are suggesting that VOCs can influence the movement of green lacewing larvae only for short period of time, while on the other hand two-spotted lady beetle larvae can follow the chemical signal for longer period of time. Results demonstrate a laboratory attraction of two-spotted lady beetle and the green lacewing larvae to a synthetic (E)-β-ocimene. Furthermore, our study showed a repellency of two-spotted lady beetle and the green lacewing larvae to a synthetic (E)-nerolidol, (E)-β-farnesene, and methyl salicylate.
ABSTRACTThis paper addresses yield loss due to red deer (Cervus elaphus) grazing on permanent grasslands on three organic farms in SE Slovenia over two consecutive years. Deer graze on permanent ...grasslands throughout the year, but the resulting crop loss varies during the growing season. Accounting for three mowings, the quantitative yield loss due to deer grazing totalled 48–52%, or 3.9–4.3 t/ha. Deer had the highest consumption capacity in the spring (first mowing: yield loss of 1.7–1.9 t of air-dried hay/ha), and towards the end of the growing season, consumption decreased (third mowing: loss of 0.9 t/ha). A floristic inventory indicated low species diversity and production in permanent grasslands in SE Slovenia. The crude protein content in unprotected plots was generally greater than that in protected plots, but due to a large quantitative yield loss, the yield of crude protein and net energy for lactation on heavily grazed land were much lower than those on protected land in all mowings. The average additional cost per unit of heavily grazed area ranged from 182 to 344 EUR/ha, and the differences are the result of the different intensities of game grazing in individual locations and grassland production capacities.
Plants under herbivore attack emit mixtures of volatiles that can attract the natural enemies of the herbivores. Entomopathogenic nematodes (EPNs) are organisms that can be used in the biological ...control of insect pests. Recent studies have shown that the movement of EPNs is associated with the detection of chemical stimuli from the environment. To date, several compounds that are responsible for the mediation in below ground multitrophic interactions have been identified. In the review, we discuss the use of EPNs in agriculture, the role of belowground volatiles and their use in plant protection programmes.
Entomopathogenic nematodes (EPNs) play a role in indirect defenses of plants under attack by root herbivores. We have tested the chemotactic responses of 4 EPN species (
Steinernema
feltiae
,
S. ...carpocapsae
,
S. kraussei
, and
Heterorhabditis bacteriophora
) to 5 compounds (1 α-Pinene, 2 Terpinolene, 3 Bornyl acetate, 4 2-Ethyl-hexanol, and 5 2, 4-Di-tert-butylphenol) released by damaged (3, 4, 5) and undamaged (1, 2) carrot roots. We hypothesized that the EPN directional responses to the tested volatile compounds (VOCs) could be related to foraging strategy and would vary among species, VOC, and VOC concentrations. Our results indicate that all of the tested EPN species exhibited a weak attraction or repulsion to volatiles, irrespective of their foraging strategy. Terpinolene was a repellent for EPN species classified in all three foraging groups. However, such values of chemotaxis index (CI) were reported with EPN species only when pure concentration of VOC was used. Based on our current results, we conclude that responses to distinct volatile cues are a species-specific characteristic. Our results suggest that EPNs are able to distinguish herbivore-induced chemicals from chemicals that are typical for healthy roots.
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