Phytoparasitica最新文献

The white mango scale, Aulacaspis tubercularis Newstead (Hemiptera: Diaspididae) is an exotic pest that causes important economic damage in the Spanish mango crops. Prospecting for potential natural enemies, the parasitic wasp Arrhenophagus chionaspidis Aurivillius (Hymenoptera: Encyrtidae) was first detected attacking immature male stages of A. tubercularis in Tenerife (Canary Islands, Spain) in 2022. Still, its influence on pest populations was not evaluated. This endoparasitoid was identified by its morphological characteristics and characterized for the first time by DNA barcoding of adult females using partial (651 bp) mitochondrial cytochrome oxidase 1 (mtCOI) gene (Genbank accession number OQ646824). Its potential utilization as biological control agent of A. tubercularis in mango crops is discussed. Therefore, further studies need to be conducted about its biology, population dynamics and rate of natural parasitism for the development of effective biological control strategies of A. tubercularis in mango.

Screen house leaf cage experiments were conducted under no-choice conditions to ascertain the antibiosis mechanism operating in introgression cotton lines against the whitefly, Bemisia tabaci (Gennadius) during July and September 2022. Seventeen cotton introgression lines and two parents, namely Synthetic polyploid (A2D1) and upland cotton line PIL 43, were assessed for development and survival of various biological parameters like fecundity, nymphal and pupal growth index. An antibiosis mechanism of resistance was documented in the parent, Synthetic polyploid and introgression lines, D5-BW-WF-28, C1-P-1, C1-P-31, and C1-P-36, and were categorized as resistant lines. In resistant introgression lines, survival and the nymphal/pupal growth index were lower, but the overall development period was longer. Among biophysical parameters, trichome density, leaf area and vascular bundle length showed significantly positive whereas leaf lamina thickness exhibited negative association with fecundity. Sugars were found to be higher in susceptible genotypes whereas phenols and proteins were comparatively higher in resistant lines. However, total soluble and reducing sugars showed a positive correlation, while total soluble proteins and total phenols manifested a negative correlation with fecundity. It may thus be concluded that antibiosis mechanism of resistance is operating in cotton introgression lines; and biophysical and biochemical parameters play a predominant role in imparting resistance against B. tabaci. To the best of our knowledge, this is the first report illustrating the development of whitefly resistant introgression lines using Synthetic cotton polyploid (A2D1).

Abstract

The sweet potato/cotton whitefly Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) is one of the most destructive vegetable pests in greenhouses in Türkiye. While the preferred method of control primarily relies on insecticides such as neonicotinoids, organophosphates and pyrethroids, their intensive use has caused whiteflies to rapidly become resistant. Samples were collected from 13 Turkish B. tabaci greenhouse populations. Bioassays from the Marmara Region identified as high as a 53-fold increase in resistance to chlorpyrifos-ethyl, a 303-fold increase to imidacloprid and a 282-fold increase to acetamiprid. Bioassays in the Central Anatolia Region reported a 76-fold increase in resistance to deltamethrin and—15-fold increase to thiamethoxam. Most of the populations showed cross-resistance for neonicotinoids. All collected B. tabaci populations were determined to be MEAM 1 (also referred to as biotype B) for diagnostic band E_0.14. The E_0.14 esterase variant that helps to diagnose biotype B insects was found in all individuals from field populations. Almost all populations showed higher non-specific esterase, glutathione-S-transferase (GST) and monooxygenase activity when compared to susceptible SUD-S population. AChE insensitivity assays for individual B. tabaci suggest a target-site modification as a mechanism of resistance to chlorpyrifos-ethyl. This is the first report of AChE variants identified based on their sensitivities to chlorpyrifos ethyl-oxon and pirimicarb in Turkish B. tabaci populations. Fixed ace mutations in the target-site of organophosphates and pyrethroids were identified in six populations. Resistance to organophosphates and neonicotinoids were at least partially related to both ace mutations and insensitive AChE and monooxygenase activities, respectively. The results will help develop effective resistance management programs of B. tabaci in Türkiye.

Illinoia liriodendri (Monell) (Hemiptera: Aphididae) is an Eastern North American native aphid species that infests ornamental tulip trees, Liriodendron tulipifera L. (Magnoliales: Magnoliaceae), in many localities of Spain and southern Europe. This is a comprehensive three-year study on the biology and ecology of the aphid, where its life cycle, phenology, population dynamic trends, comfort damages, natural enemy complex and its potential to control aphid populations have been investigated for the first time in Europe. The monoecic-holocyclic annual cycle of I. liriodendri has been demonstrated. The highest infestation levels were recorded in May and June, but infestation severity varied among localities. No clear trend regarding the effect of planting site (pit vs. ground) on aphid abundance was observed. A strong positive relationship between the aphid infestation severity and the honeydew dripping was recorded. There was a wide complex of natural enemies associated with the aphid. Coccinellidae were the most abundant predators (< 95%) and showed a positive numerical response to the aphid infestation. Several parasitoid species (mainly Hymenoptera: Aphidiinae and Hymenoptera: Aphelinidae) were found parasitizing I. liriodendri in Spain. The role of natural enemies as agents for controlling the aphid populations is discussed.

Several Oriental and Australian species of Ficus have been introduced outside their native range and planted as ornamentals in urban habitats throughout the Mediterranean. This translocation of plant species has led to the introduction of host-specific insects such as their pollinating fig wasps (Hymenoptera: Agaonidae). Here, the Australian fig wasp Pleistodontes imperialis Saunders, 1882 is reported for the first time from Greece. Partial COI genes were sequenced for specimens sampled in Greece and Cyprus, and they appear to share identical haplotypes. Interestingly, this species-specific wasp not only develops in figs of its usual host, Ficus rubiginosa, but also in figs of Ficus watkinsiana, another Australian species introduced in Greece, which is pollinated by a second agaonid species (Pleistodontes nigriventris Girault, 1915) in its native range. Although no negative economic or environmental impacts have been observed yet, monitoring of alien Ficus spp. in the region is encouraged to prevent their possible establishment in natural habitats.

Abstract

Dysdercus koenigii, a global cotton pest, inflicts significant crop losses via sucking the moisture and oil contents from leaves and seeds. The growing environmental hazards with conventional pesticides have led to the exploration of nanotechnology to formulate alternative products and nanoemulsions as suitable insecticide delivery vehicles for target pests. We formulated nanoemulsions using β-cyfluthrin (a pyrethroid) and DMSO (Dimethyl sulfoxide) in 1:2, 1:4, 1:6, 1:8 and 1:10 proportions. The nanoemulsions (NE) were characterized morphologically and biophysically (size, pH, viscosity, PDI and zeta potential) by Transmission Electron Microscopy, Dynamic Light Scattering and Zeta Potential Analyzer. Each NE was transparent, stable, had 11.4–174.1 nm droplet size and, optimal PDI and zeta potential. The spherical and monodispersed 1:2 β-cyfluthrin + DMSO NE was found as the most optimal formulation inducing 100% mortality in D. koenigii fifth instars after 24 h; the NE (LD₅₀ = 3.536 mg/L) displayed 44% higher efficacy than the β-cyfluthrin alone (LD₅₀ = 5.059 mg/L). The LD₅₀ dose of the 1:2 NE enhanced the activity of α-esterase, β-esterase, glutathione-S-transferase, and acetylcholinesterase in nymphs in comparison with β-cyfluthrin alone. The β-cyfluthrin nanoemulsion can act as a potential tool to manage D. koenigii after thorough field assessment and evaluation of the impact on non-target organisms.

Abstract

Phytosanitary management on tomato crop is a challenge for organic and conventional growers. Whitefly Bemisia tabaci (Gennadius) and mite Tetranychus evansi Baker and Pritchard are among the major pests. Methyl-salicylate (MeSa) is a methyl ester from salicylic acid and activates secondary metabolism pathways in plants. Zingiberene (ZGB) is a secondary compound associated with resistance to B. tabaci. The aim of the study was to study the relationship between the exogenous MeSA spraying and zingiberene content in tomato leaves and adult whitefly and mite responses. MeSa concentrations [0 (control), 100, 200, 300, 400, 500 µg L⁻¹)] were applied on tomato to evaluate the ZGB content and the relationship with whitefly and spider mite on plants. After the last ZGB analysis, plants were placed in B. tabaci-highly infested greenhouse. The number of adult whiteflies on plants was determined three days later. Tomato leaflets were collected from treated plants and infested with five T. evansi e females. The number of larvae emerging from eggs was evaluated after 96 and 120 h. Reduction of adult whiteflies (from 78 to 8%) was also observed in plants exogenously treated with MeSa [significant and negative correlation (0.88)]. The number of eggs and number of larvae were linearly reduced with increase of MeSa concentration. Positive correlation (0.97) between exogenous MeSa concentrations vs. ZGB contents was observed. Negative correlations (0.90, 0.89 and 0.94) were estimated, between MeSa concentration vs. tomato red spider mite oviposition and egg hatchability (96 and 120 h), respectively. These results indicate that exogenous MeSa applications increases ZGB content and plant resistance to B. tabaci and T. evansi.

Due to the damaging effects of root-knot nematodes on crops and the dangerous effects of chemical nematicides on both people and the environment in Egypt, the purpose of this study was to assess the power of polysaccharides and polyphenol extracts as well as their nano-forms from marine algae (Laurencia papillosa and Dilophys fasciola) used as eco-friendly alternatives for the control of Meloidogyne incognita. The nano-forms of algal extracts efficiently suppressed M. incognita egg hatching and increased juvenile mortality compared to the control. The tested treatments effectively decreased galls and egg masses of tomato roots compared to the control in the field. Dilophys fasciola extract and its nano-form showed promising nematicidal activity compared to L. papillosa extract. Generally, algal treatments boosted tomato plant defense system against M. incognita by triggering the production of some biochemical constituents such as phenolic compounds, polyphenol oxidase and chitinase enzymes. Consequently, the productivity and quality parameters of tomato fruits significantly increased.

Abstract

Insect pests are exposed to repeated applications of pesticides to effectively manage the pest species. This induces insecticide resistance and resurgence of target insect pest, along with an accelerated growth rate of the targeted individual. The present experiment was put into execution to examine transgenerational hormesis against different biological parameters of Phenacoccus solenopsis when exposed to sublethal concentrations of Pyriproxyfen (Pyriproxyfen® 10 EC) and Buprofezin (Buprofezin® 25 WP). Insects exhibited concentration-dependent mortality diminishing in succeeding generations. P. solenopsis receiving the sublethal concentration of LC₁₀ (0.03%) of Pyriproxyfen® exhibited hormesis in natality in generation G-4 (1282.4 nymphs/20 females) and G-5 (1296.2 nymphs/20 females). The adult female exposed to LC₁₀ (0.02%) of Buprofezin® also expressed hormesis in natality in G-4 (1261.5 nymphs/20 females) and G-5 (1282.8 nymphs/20 females). Hormesis in female longevity was also found when treated with a sublethal concentration of LC₁₀ for Pyriproxyfen® (0.03%) in G-4 (46.41 days) and G-5(46.35 days). Similarly, adults in G-4 and G-5 at a sublethal concentration of LC₁₀ (0.02%) for Buprofezin® induced hormesis 45.53 days and 46.69 days, respectively, whereas in G-4 (4.79 days) and G-5 (4.92 days) at stimulatory concentrations of LC₁₀ (0.03%) for pyriproxyfen®. The research findings indicate that the consistent application of sublethal concentrations can elicit stimulatory effects on various biological traits. This highlights insects’ remarkable ability to adapt to stressors. It is imperative to consider this aspect when incorporating pest management programs.

In the past decade, due to straw incorporation and soil salinization, wheat crown rot (FCR) mainly caused by Fusarium pseudograminearum has become widespread in the Huang-Huai wheat-growing region of China. It poses a serious threat to the high and stable yield of wheat and has brought potential toxin pollution to animal feed made from wheat straw. The phenylpyrrole fungicide fludioxonil is widely used in seed dressing or coating. Previous studies of our research group have shown that fludioxonil has a strong inhibitory effect on the mycelial growth of F. pseudograminearum, but the mechanism of inhibition has remained unclear. In this paper, the inhibitory mechanism of fludioxonil on the mycelial growth of F. pseudograminearum was studied, and the inhibitory effect of fludioxonil on spore germination, germ tube elongation and sporulation were evaluated, and the field control efficacy of fludioxonil on FCR was determined. The results showed that fludioxonil made the mycelium of F. pseudograminearum malformed as follows: the top mycelium branches increased, the mycelium became dense, the mycelium spacing became shorter; mycelial cells in the colony became irregularly enlarged, branches increased but were short and uneven in thickness, had blunt round top or were enlarged. Compared with mycelial growth, the inhibitory effect of fludioxonil on conidial germination was weaker, and the EC₅₀ value to conidial germination was 7.2358–55.3856 μg/mL. However, fludioxonil delayed the germination time of conidia and increased the probability of conidia germination from intermediate cells. Fludioxonil also recorded a strong inhibitory effect on germ tube elongation, and the EC₅₀ to germ tube elongation was only 0.0078 μg/mL. Fludioxonil caused conidial cells enlargement, but the teratogenic effect on the germ tube was not obvious. Fludioxonil could also delay the formation time of conidia. In the mung bean soup liquid medium containing fludioxonil, it took 72 h to form conidia, while 0.8 μg/mL completely inhibited conidia formation. The EC₅₀ values of fludioxonil to sporulation ranged from 0.1439–0.2739 μg/mL. The control efficacies of fludioxonil against FCR at the jointing and filling stages of wheat were better than that of carbendazim, and it reduced the whiteheads rate at the milk stage, but decreased the control efficacy at the filling stage. Fludioxonil could be used as a seed dressing agent in the prevention and control of FCR.