Phytoparasitica最新文献

Anticarsia gemmatalis (Hübner, 1818) (Lepidoptera: Erebidae) larvae inflict damage on host plants by consuming their leaves. Controlling them represents a key strategy for mitigating economic losses in Brazilian soybean cultivation. In this study, we elucidate the impact of dysbiosis, induced via exposure to the antibiotic tetracycline (TCN), on A. gemmatalis in the presence or absence of the protease inhibitors GORE1 and GORE2. These peptides, each comprising three amino acids (VAL-LEU-LYS and VAL-LEU-ARG, respectively), were investigated. In vitro analyses revealed that the affinity of trypsin-like enzymes for the substrate diminished in caterpillars with dysbiosis that were concurrently exposed to the peptides. Noteworthy differences emerged across treatments in survival analyses, nutritional parameters, and pupal weight. Among these, caterpillars exposed to the GORE2 peptide exhibited the highest mortality and lowest pupal weight. Histological alterations were observed in A. gemmatalis exposed to TCN and peptides. Digestive cells exhibited cytoplasmic vacuolation and heightened apocrine secretion within the intestinal lumen compared to the control group. The present study has successfully demonstrated notable shifts in protein degradation, particularly evident in the altered affinity of A. gemmatalis trypsin-like enzymes when subjected to TCN and the inhibitory effects of GORE1 and GORE2 peptides. Encouragingly, the antibiotic exposure exhibited no detrimental impacts on the survival, nutritional parameters, or overall fitness of A. gemmatalis. Moreover, our findings collectively underscore the potential efficacy of integrating GORE1 and GORE2 peptides for A. gemmatalis management. These peptides have demonstrated significant inhibitory capabilities, coupled with morphological alterations observed in midgut cells, possibly arising from the delayed expression of proteases. This morphological shift appears to impede the pest's nutrition and survival, positioning these tripeptides as a promising tool in addressing the challenges posed by this soybean pest.

The Japanese beetle, Popillia japonica Newman (Coleoptera: Scarabaeidae), is a major pest of turfgrasses, pastures and hay meadows in the invaded areas of North America and Europe. This study evaluated the efficacy of two biocontrol agents (the fungus Metarhizium anisopliae (Metschn.) Sorokin and the nematode Heterorhabditis bacteriophora Poinar) and the insecticide chlorantraniliprole against P. japonica larvae using a soil seeder modified for soil injection with minimum grass disturbance (“Eco Defender 25”). In 2021, trials were carried out at two hay meadows in the Lombardy region of Italy, using water and undisturbed plots as controls. Both biological agents and the insecticide reduced larval densities at one or the other site, but not at both sites, compared to the control. In the following spring, drone surveys conducted over the hay meadows did not show differences in grass quality between treatments, including the undisturbed plots. Overall, the soil injector demonstrated efficacy under distinct conditions, highlighting the need for further optimization according to soil properties.

There is a shift of dominance from grasses to broad-leaf weeds and sedges in direct-seeded rice (DSR) due to the continuous use of grass herbicides. The uncontrolled growth of broad-leaf weeds and sedges in DSR throughout the entire crop season resulted in a 52–64% reduction in crop yield. Field studies were carried out to evaluate control of sedges and broad-leaf weeds with post-emergence application of 8, 12, 16 g ha⁻¹ of metsulfuron; 435, 580, 725 g ha⁻¹ of 2,4-dimethyl amine salt; 2, 4, 6 g ha⁻¹ of pre-mix of metsulfuron plus chlorimuron, and azimsulfuron 20 g ha⁻¹ in direct-seeded rice. The post-emergence application of azimsulfuron 20 g, metsulfuron plus chlorimuron 4 g and 2,4-D amine salt 725 g ha⁻¹ effectively reduced density and biomass of Cyperus rotundus L., C. iria L., Phyllanthus niruri L., Alternanthera philoxeroides (Mart.) Griseb., Mollugo nudicaulis Lam., Digera arvensis Forsk., Caesulia axillaris Roxb. and Ammannia baccifera L. Metsulfuron 16 g ha⁻¹ as post-emergence resulted in effective control (92.2–98.9%) of broad-leaf weeds but gave partial control (19.8–37.1%) of sedges. The maximum grain yield was recorded in weed-free treatment and it was statistically similar to grain yield obtained with post-emergence use of azimsulfuron 20 g or metsulfuron plus chlorimuron 4–6 g or 2,4-D amine salt 580–725 g ha⁻¹ herbicides. It is concluded that post-emergence use of 2,4-D amine salt 725 g or metsulfuron plus chlorimuron 4 g ha⁻¹ is efficient and economical herbicides for control of broad-leaf weeds and sedges in direct-seeded rice.

The present study highlights, for the first time, the chemical composition of secondary metabolites (lipophilic and hydrophilic compounds) present in the phloem tissues of infected mature Pinus pinaster Ait. trees (on average 74 years old), which may be potentially determinant in the development of the pine wood nematode (PWN) Bursaphelenchus xylophilus. The levels of secondary metabolites in the phloem of infected trees were fairly constant along the height of the trees (an average of 30% dry phloem), but slightly lower compared with total extractives content in the phloem of mature healthy P. pinaster trees (30.0 vs. 39.9%). The hydrophilic fraction represented 91% of the total soluble compounds (27.3% of phloem mass) and it was mainly composed of phenolic compounds and reducing sugars (44.8% and 58.8% of the ethanol-water extracts). The lipophilic fraction (2.7% of phloem mass), was dominated by tricyclic diterpenic compounds (54.2–63.2% of the total lipophilic extracts) and fatty acids. Differences in the relative concentrations of individual compounds were observed compared to healthy pines, suggesting a response to the biotic stress imposed by nematode damage by an increased content of diterpenic resin acids, specifically dehydroabietic and abietic acids, and of total unsaturated fatty acids with a predominance of 9-octadecenoic acid.

Abstract

Trichogramma parasitoids are effective biocontrol agents and a reliable component of integrated strategies against lepidopterous pests. The success of these parasitoids in pest management relies not only on their ability to parasitize their hosts but also on their adaptation to the climatic conditions of the release area, particularly temperature. The expression of life history traits of Trichogramma spp. can vary significantly with temperature, depending on the species or strains being tested. Trichogramma cacoeciae (Marchal), T. euproctidis (Girault), T. minutum (Riley), and T. brassicae (Bezdenko) (Hymenoptera: Trichogrammatidae) are currently used in biocontrol programs against important lepidopteran pests. We aimed to assess the temperature sensitivity of these parasitoids during oviposition and preadult development, and to identify the most tolerant species to high temperatures conditions commonly encountered in Mediterranean Basin countries during the growing seasons. The biological characteristics of the four species were determined at seven temperature regimes expressed as temperatures during oviposition and preadult development (25/25, 25/30, 25/35, 25/40, 30/30, 35/35 and 40/40 °C), using Ephestia kuehniella Zeller (Lepidoptera: Pyralidae) eggs. Trichogramma cacoeciae showed the highest level of parasitism at 30/30 °C, while the other species exhibited the highest levels at 25/25 °C and 25/30 °C. All Trichogramma species were able to develop and survive from 25 °C to 35 °C, but not at 40 °C. Temperature significantly affected the longevity and fecundity of female progeny, with both decreasing when the temperature increased from 25 °C to 35 °C. When exposed to 35/35 °C, T. cacoeciae demonstrated the most optimal performance in terms of parasitization efficiency, developmental capacity, progeny longevity, and fecundity.

This research aimed to study the diversity of soft scale parasitoids and examine their potential in the biological control of harmful Coccidae on cultivated and ornamental plants. Forty species of parasitoid wasps from four families (Hymenoptera: Chalcidoidea) were reared and determined from 16 species of soft scales (Hemiptera: Coccidae). A total of 6,249 individuals of parasitoid wasps were collected from 35 localities in Serbia from 2014 to 2017. The most numerous genera are Metaphycus with 10, Coccophagus with 7, and Blastothrix with five reared species. The most abundant species is C. lycimnia, reared from second-instar larvae of all 16 species of scale insects and from females of 11 soft scale species, with a total of 1,053 individuals. Of the 40 identified species, 15 are new to the fauna of Serbia: Coccophagus piceae, Coccophagus proximus, Coccophagus silvestrii, Encarsia gigas (Aphelinidae), Adelencyrtus intersectus, Anagyrus schoenherri, Blastothrix brittanica, Blastothrix erythrostetha, Blastothrix hedqvisti, Encyrtus infidus, Metaphycus hageni, Metaphycus stanleyi, Metaphycus unicolor, Microterys hortulanus (Encyrtidae) and Eunotus obscurus (Pteromalidae). Ninety-nine (99) hymenopteran/coccoid associations were identified in this study, of which 16 associations are new.

The velvetbean caterpillar (VBC), Anticarsia gemmatalis Hübner (Lepidoptera: Noctuidae), is a significant soybean pest in the Americas and controlled mainly with chemical insecticides. Toxicity, survival, respiration, and anti-feeding effect of the VBC larvae exposed to four neurotoxic insecticides (α-cypermethrin, abamectin, chlorpyrifos, and thiamethoxam) by ingestion were evaluated. Toxicity bioassays demonstrated that abamectin (LC₅₀ = 0.097 g L^–1), thiamethoxam (LC₅₀ = 0.537 g L^–1), and chlorpyrifos (LC₅₀ = 1.998 g L^–1) were toxics to VBC. The survival rate was 98% in control caterpillars, declining to 35% in larvae exposed to LC₅₀ of thiamethoxam, 26% in larvae treated with chlorpyrifos, 23% in larvae treated with abamectin, and 10% in those treated with α-cypermethrin. The neurotoxic insecticides reduced low respiration rates and produced feeding inhibition in VBC caterpillars. Our results suggest that abamectin, α-cypermethrin, chlorpyrifos, and thiamethoxam are highly effective against VBC and may be implemented to manage its populations in soybean crops.

Dacus frontalis (Diptera: Tephritidae) is an emerging species affecting fruit production in Africa and may pose a serious risk to the Cucurbitaceae fruit producing industry in Europe in response to climate change. To understand how temperature affects the fitness and population dynamics of this species and consequently its invasive potential, we investigated for the first time the survival and development time of immature stages, longevity and fecundity of D. frontalis adults in the laboratory at four constant temperatures of 15, 20, 25 and 30 °C. In addition, the lower developmental threshold and thermal constant were calculated using a temperature summation model. Results showed that the rearing temperature has a significant effect on the survival, development, reproduction, and longevity of the pumpkin fruit fly. The highest survival rates of eggs, larvae, pupae, adult females and males were observed at 20 °C. The development time of immature stages and from egg to adult, decreased significantly with increasing temperature from 15 to 30 °C. Females produced a significantly higher number of eggs at 20 °C, and no oviposition was observed at 15 °C. Pupae were able to survive at 15 °C with the longest development time, suggesting that this tephritid species can overwinter as pupae in the field in North Africa. The thermal constant of egg, larval, and pupal stages were 33, 95, and 210 DD, respectively. The minimum temperature threshold of egg, larval, and pupal stages were 4.6, 13.5, and 9.5 °C, respectively. These thermal requirements may explain the seasonality of D. frontalis observed in North Africa. Implications for pest management and potential geographical distribution are discussed.

Chelonus inanitus L. (Hymenoptera: Braconidae) is an egg-larval parasitoid of Lepidoptera, with the potential for biological control of noctuids. The lack of information merits research on its reproductive and developmental biology. We studied the reproduction of mated parasitoid pairs during female lifetime and the development of the progeny on two hosts, the factitious Ephestia kuehniella Zeller (Lepidoptera: Pyralidae) and the natural Spodoptera littoralis Boisduval (Lepidoptera: Noctuidae). The longevity of pairs subjected or not to parasitism was compared. Development of the progeny after parasitization and growth rates were studied. Reproduction decreased the longevity of both sexes in every host. The similar survival patterns proved that sex was not a factor influencing longevity. Females parasitized immediately after emergence and offspring production peaked at 2–2.5 days. Low parasitization rates (3–12%) were generally observed. Reproduction on S. littoralis was fourfold less efficient, probably due to failure of immature stages leading to poor progeny. Sex ratio of the progeny was mostly male-biased. Males developed faster in both hosts. Development was 20 days shorter in the natural host. Strikingly, the parasitoid performed successfully better on the factitious host. Inbreeding, poor understanding of host preference, and inadequate rearing and handling practices are discussed as possible causes of the worse parasitoid performance on S. littoralis.

A species of Heterodera has been known to parasitise cereals in Australia since the 1930s. It caused significant yield losses across Australia’s cereal growing regions until resistance breeding largely brought it under control, although it still occurs occasionally, especially in South and Western Australia. Australian cereal cyst nematode has long been considered to represent Heterodera avenae. However, in 2002 the name Heterodera australis was proposed for Australian cereal cyst nematode, as it could be distinguished from all non-Australian populations of H. avenae via biochemical and molecular methods. This new species proposal came with speculation that both H. avenae and H. australis might occur in Australia, and that H. australis might represent a native species. The name H. australis has generally not been accepted by Australian scientists, nor the notion that it is native. There remains some uncertainty as to the validity of H. australis and whether more than one species of cereal cyst nematode occur in Australia. Using a molecular barcoding approach (COI, 18S, ITS, 28S) we examined the species composition of cyst nematodes present in soil samples collected between 1989–2023 from Australian cereal growing regions. We find only one species of Heterodera parasitising cereals and, based on phylogenetic analyses, accept the validity of H. australis as the name best representative of this species. We also argue that, based on presently available evidence, H. australis is not native and was most likely introduced into Australia from Asia in the 1850s, rather than from Europe as has been generally assumed.