The role of botanical treatments used in apiculture to control arthropod pests

Among pests of bees and beehives, arthropods make up a large and important group. Mites like Varroa destructor, Acarapis woodi, or Tropilaelaps spp., beetles (Aethina tumida, Oplostomus spp.), and lepidopterans (Galleria mellonella, Achroia grisella) decrease honey bee population and vitality, with subsequent significant colony production losses. Synthetic chemicals have been traditionally used to protect honey bee colonies from pests’ infestations but they have often been of poor selectivity, consequent high toxicity to bees and humans, and resistance development by the targeted apiary pests. The current European policy encourages the usage of eco-friendly methods to combat bee pests and the international research highlights plant secondary metabolites as candidate alternatives of significance. In this review, we argue the potential of plant-derived substances in the protection of the bee colonies against their arthropod pests. The before mentioned major apiary arthropods are briefly described followed by the recent reports on the botanical extracts and notable constituent compounds exhibiting activity against them. We discuss the different ways the essential oils are reported to be applied to the bee or the apiary, along with the importance of the application method to the exhibited efficacy. We designate synergism issues of blends, attractants, and repellency cases, as well as selectivity and mode of action as reported for bees or insect pests. © 2022, INRAE, DIB and Springer-Verlag France SAS, part of Springer Nature

Cell wall modifications in giant cells induced by the plant parasitic nematode meloidogyne incognita in wild-type (Col-0) and the fra2 arabidopsis thaliana katanin mutant

Meloidogyne incognita is a root knot nematode (RKN) species which is among the most notoriously unmanageable crop pests with a wide host range. It inhabits plants and induces unique feeding site structures within host roots, known as giant cells (GCs). The cell walls of the GCs undergo the process of both thickening and loosening to allow expansion and finally support nutrient uptake by the nematode. In this study, a comparative in situ analysis of cell wall polysaccharides in the GCs of wild-type Col-0 and the microtubule-defective fra2 katanin mutant, both infected with M. incognita has been carried out. The fra2 mutant had an increased infection rate. Moreover, fra2 roots exhibited a differential pectin and hemicellulose distribution when compared to Col-0 probably mirroring the fra2 root developmental defects. Features of fra2 GC walls include the presence of high-esterified pectic homogalacturonan and pectic arabinan, possibly to compensate for the reduced levels of callose, which was omnipresent in GCs of Col-0. Katanin severing of microtubules seems important in plant defense against M. incognita, with the nematode, however, to be nonchalant about this “katanin deficiency” and eventually induce the necessary GC cell wall modifications to establish a feeding site. © 2019 by the authors. Licensee MDPI, Basel, Switzerland

PIN1 auxin efflux carrier absence in Meloidogyne incognita-induced root-knots of tomato plants

The nematode species Meloidogyne incognita infects a large variety of cultivated crops and is one of nature’s most notorious pests. One cultivated plant which is prone to M. incognita infestation is the tomato. Knowing that in A. thaliana the PIN auxin efflux transporters distribution is being altered upon early invasion by M. incognita, the PIN1 allocation patterns in the giant cells of tomato plants after 15 and 25 days of infection were investigated. PIN1 was absent from the giant cells’ membrane in both assessment timings examined, indicating the maintenance of a local auxin maxima, which was also supported by IAA immunodetection. PIN1 distribution pattern could be attributed on either the nematodes nutritional needs throughout its life cycle or due to the tomato plants differential responses upon M. incognita infection. © 2021, Koninklijke Nederlandse Planteziektenkundige Vereniging

Greenhouse biofumigation with Melia azedarach controls Meloidogyne spp. and enhances soil biological activity

The need for environmentally friendly agricultural practices has led to the development of plant-based nematicides for root-knot nematode control. The efficacy of these botanicals has been tested primarily under laboratory and rarely under actual field conditions. Moreover, any side effects on non-target soil organisms that support soil biological activity are usually ignored. Herein, we evaluate the efficacy of Melia azedarach preparations against Meloidogyne spp. in a tomato greenhouse, by root gall examination and soil J2 enumeration. We also assessed side effects on soil microbes through PLFA analysis and microbivorous nematodes, and we quantified several plant growth parameters (e.g., fruit number and weight, root weight). Different treatments within the greenhouse included M. azedarach ripe fruit powder (MFP), ripe fruit water extract (MWE) and furfural, one of the principal active ingredients of M. azedarach and previously known to exhibit fumigant nematicidal activity. Results were compared to those obtained with the commercial nematicide oxamyl (Vydate® 10 SL) and an untreated control. All treatments were repeated every 20 days throughout the cultivation period. MFP and MWE suppressed Meloidogyne spp. often at the same levels obtained by furfural and oxamyl treatments and enhanced soil biological activity, as indicated by the proliferation of soil microbes and microbial feeding nematodes. Furfural and oxamyl adversely affected the soil community, especially the free-living nematodes. Moreover, furfural was phytotoxic to tomato plants in spite of its natural origin. © 2017, Springer-Verlag GmbH Germany

Strong synergistic activity and egg hatch inhibition by (E,E)-2,4-decadienal and (E)-2-decenal in Meloidogyne species

Recent research has been focused on the potential of plant natural products for the control of nematodes, but few studies are reported on synergistic interactions and egg hatch inhibition properties of botanicals. Herein, we evaluate the nematicidal activity of (E,E)-2,4-decadienal, 2-undecanone, furfural and (E)-2-decenal alone and in binary mixtures, on different Meloidogyne spp. and growth stages. (E,E)-2,4-decadienal exhibited strong paralysis activity on second-stage M. incognita,M. javanica and M. arenaria juveniles (EC50/4d = 8.06, 9.04 and 12.90 μg mL−1, respectively) and all its binary mixtures demonstrated synergy on all nematode species. (E,E)-2,4-decadienal best inhibited M. incognita undifferentiated egg hatch and J2 release from eggs immersed in 10 μg mL−1 solution. SEM experiments revealed malformations, in the form of constrictions, along the larvae body retained in eggs treated with (E)-2-decenal. Egg masses treated with 1 μg mL−1 solution of (E)-2-decenal released less than 50 % of the eggs if compared with the control. (E)-2-decenal and (E,E)-2,4-decadienal arrested M. incognita life cycle in pot bioassays (EC50 = 77.46 and 114.47 mg kg−1), with the latter additionally promoting tomato growth. Ailanthus altissima powder (AWP) and water extract (AWE), naturally containing (E,E)-2,4-decadienal and (E)-2-decenal, strongly arrested M. incognita life cycle in tomato plants, and AWP was far more active than AWE. Thus, we conclude that (E,E)-2,4-decadienal and (E)-2-decenal are promising nematicidal agents used alone, in artificial blends or as naturally present in botanical soil amendments. © 2015, Springer-Verlag Berlin Heidelberg

Τhe Nematicidal Potential of Bioactive Streptomyces Strains Isolated from Greek Rhizosphere Soils Tested on Arabidopsis Plants of Varying Susceptibility to Meloidogyne spp.

A total of 461 indigenous Streptomycetes strains recovered from various Greek rhizosphere habitats were tested for their bioactivity. All isolates were examined for their ability to suppress the growth of 12 specific target microorganisms. Twenty-six were found to exert antimicrobial activity and were screened for potential nematicidal action. S. monomycini ATHUBA 220, S. colombiensis ATHUBA 438, S. colombiensis ATHUBA 431, and S. youssoufensis ATHUBA 546 were proved to have a nematicidal effect and thus were further sequenced. Batch culture supernatants and solvent extracts were assessed for paralysis on Meloidogyne javanica and Meloidogyne incognita second-stage juveniles (J2). The solvent extracts of S. monomycini ATHUBA 220 and S. colombiensis ATHUBA 438 had the highest paralysis rates, so these Streptomycetes strains were further on tested for nematodes’ biological cycle arrest on two Arabidopsis thaliana plants; the wild type (Col-0) and the katanin mutant fra2, which is susceptible to M. incognita. Interestingly, S. monomycini ATHUBA 220 and S. colombiensis ATHUBA 438 were able to negatively affect the M. incognita biological cycle in Col-0 and fra2 respectively, and increased growth in Col-0 upon M. incognita infection. However, they were ineffective against M. javanica. Fra2 plants were also proved susceptible to M. javanica infestation, with a reduced growth upon treatments with the Streptomyces strains. The nematicidal action and the plant-growth modulating abilities of the selected Streptomycetes strains are discussed. © 2020 by the authors

Cytotoxic tirucallane triterpenoids from Melia azedarach fruits

The phytochemical investigation of the dichloromethane-soluble part of the methanol extract obtained from the fruits of Melia azedarach afforded one new tirucallanetype triterpene, 3-α-tigloylmelianol (1) and three known tirucallanes, melianone (2), 21-β-acetoxy-melianone (3), and methyl kulonate (4). The structure of the isolated compounds was mainly determined by 1D and 2D NMR experiments as well as HPLC-Q-TOF mass spectrometry. The cytotoxicity of the isolated compounds toward the human lung adenocarcinoma epithelial cell line A549 was determined, while no activity was observed against the phytonematode Meloidogyne incognita. © 2010 by the authors.Fil:Bueno, C.A. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.Fil:Alché, L.E. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina