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Exclusion of ground-nesting ants promotes biological control, but facilitates the establishment of an exotic canopy-nesting ant species
No full textExclusion of ground-nesting ants from tree canopies is an ant-management technique used in fruit crops. This strategy aims to disrupt the symbiotic relationship between ants and honeydew-producing herbivores, which are protected by ants, and enhance the biological control of these herbivores. Here, we evaluated this strategy to enhance the biological control of mealybugs in persimmon, but obtained an unexpected outcome. Using a randomized block design in a commercial persimmon orchard during two consecutive years, we demonstrated that physical barriers based on sticky bands excluded native ground-nesting ant species from persimmon trees and reduced the protection that these ants provided to mealybugs. The exclusion of native ground-nesting ants also increased the density and efficacy of the biological control agents of the mealybug. However, physical barriers favoured the establishment of the exotic canopy-nesting ant species Cardiocondyla obscurior. This ant species established its colonies under the sepals of persimmon fruit, and its abundance increased by more than 10 times in trees with physical barriers. Our results show that the exclusion of native ground-nesting from fruit trees can promote the control of invasive mealybugs, but may also facilitate the establishment and spread of exotic canopy-nesting ant species, hence increasing their invasive potential. Further research should evaluate alternative ant management strategies to enhance biological control of honeydew-producing herbivores without benefiting exotic canopy-nesting ant species
Tracing pistachio nuts’ origin and irrigation practices through hyperspectral imaging
Full text linkPistachio trees have become a significant global agricultural commodity because their nuts are renowned for their unique flavour and numerous health benefits, contributing to their high demand worldwide. This study explores the application of Hyperspectral Imaging (HSI) and Machine Learning (ML) to determine pistachio nuts' geographic origin and irrigation practices, alongside predicting essential commercial quality and yield parameters. The study was conducted in two Spanish orchards and employed HSI technology to capture spectral data. It used ML models like Partial Least Squares (PLS), Support Vector Machine (SVM), and Extreme Gradient Boosting (XGBoost) for analysis.
The results demonstrated high accuracy in classifying pistachios based on origin, with accuracies exceeding 94%, and in assessing water content and colour pigments, where both PLS and SVM models achieved 99% accuracy. The research highlighted distinct spectral signatures associated with different irrigation treatments, particularly in the Near-Infrared (NIR) region, with PLS showing an accuracy of 92%. However, challenges were noted in predicting fruit orientation, while predicting height location within the tree was more successful, reflecting clearer spectral distinctions. Regression models also showed promise, particularly in predicting yield (R2 = 0.89 with PLS) and percentage of blank nuts (R2 = 0.71 with PLS). The correlation analysis revealed key insights, such as an inverse relationship between blank nuts and yield, and a strong correlation between yield and split nuts. Despite challenges in predicting fruit orientation, the research showed promising results in forecasting yield and commercial quality factors, indicating the effectiveness of spectral analysis in optimising pistachio production and sustainability
Dynamic intraguild interactions between two sympatric and congeneric coccinellid species associated with aphids could explain their coexistence in citrus agroecosystems
Full text linkScymnus interruptus and Scymnus subvillosus (Coleoptera: Coccinellidae) are the most frequent aphid predators in
Western Mediterranean citrus agroecosystems. Intraguild predation (IGP) between them would be expected, but
how IGP might affect their coexistence and biological control function remains unknown. In this work, we assess
the frequency of predator encounters in the field and investigate intraguild predation between these two
predators in laboratory settings. Different field prey scenarios derived from the field observations were simulated
with the two dominant aphid species in this agroecosystem, Aphis gossypii and Aphis spiraecola.
Scymnus subvillosus and S. interruptus engaged in IGP but the magnitude and symmetry varied with the prey
species and abundance. At high aphid densities, IGP was symmetric and weak, whereas, at low aphid densities,
IGP was strong and very asymmetric, with S. interruptus taking the role of the intraguild predator. The developmental
time of S. subvillosus was reduced when competing with S. interruptus at high extraguild prey densities.
The adult size of both predators under weak IGP also increased even when the developmental time had been
reduced.
We predict that high aphid infestations in the spring would benefit S. subvillosus, while the strong and
asymmetric IGP at low aphid infestations would hinder its coexistence with S. interruptus. Our results give a
theoretical explanation to what is observed in the field: S. subvillosus is typically dominant during the high aphid
infestations of the spring, whereas S. interruptus increases in relative dominance during the summer and fall when
aphid abundance is much less
Editorial overview: Parasites/parasitoids/biological control (2024) — research advances on plant-derived food sources in biological control
No full textBeneficial insects, such as biological control agents (BCAs), play a crucial role
in agriculture [1,2]. A conservative study estimated the annual value of natural
control attributable to beneficial insects to be about 4.5 billion dollars in the
USA alone [3]. In Europe, biological control is a cornerstone of pest management
under the new European Green Deal. Most BCAs are omnivores,
feeding on both pests and plant-derived food sources [4]. This omnivory has
led to the use of food supplements to support beneficial organisms in agricultural
systems. For example, nectar, pollen, extrafloral nectar, plant guttation,
and honeydew have been identified as important plant-derived food
sources for BCAs in ecosystems. These plant-derived products provide a rich
source of carbohydrates and proteins, significantly enhancing the success of
biological pest control. However, the availability of these food sources can be
highly variable [4], making their presence unpredictable for foraging insects.
Many of these sources are ephemeral (e.g. pollen or floral nectar), and their
quality as a food source is variable (e.g. honeydew or plant guttation) [5–7]. In
this issue, we delve deeper into these complexities, offering recent advances
on the role of plant-derived food sources for beneficial insects and the potential
for their management to enhance biological control
Olive Leaf Mottling Virus: A New Member of the Genus Olivavirus
Full text linkStudies of the virome of olive trees with symptoms of leaf mottling by high-throughput
sequencing (HTS) revealed the presence of a new virus. Full coding genome sequences of two
isolates were determined and consisted of a single RNA segment of 16,516 nt and 16,489, respectively.
The genomic organization contained 10 open reading frames (ORFs) from 5′ to 3′ : ORF1a, ORF1b
(RdRp), ORF2 (p22), ORF3 (p7), ORF4 (HSP70h), ORF5 (HSP90h), ORF6 (CP), ORF7 (p19), ORF8
(p12), ORF9 (p23) and ORF10 (p9). Phylogenetic analyses clustered this virus in the genus Olivavirus,
family Closteroviridae, with the closest species being Olivavirus flaviolae, commonly named olive leaf
yellowing-associated virus (OLYaV). However, amino acid sequences of all taxonomically relevant
proteins showed, in all cases, a divergence higher than 25% between OLYaV and the new virus,
indicating that it represents a new species in the genus Olivavirus for which the common name
of olive leaf mottling virus (OLMV) is proposed. This study represents an advance in the genus
Olivavirus and provides new insights into the olive virome
Non-destructive assessment of ’Fino’ lemon quality through ripening using NIRS and chemometric analysis
No full textThe lemon industry has the challenge of providing fruits with high-quality standards worldwide. Replacing the subjective fruit quality assessment methods with objective and non-destructive techniques. Total soluble solids (TSS) and titratable acidity (TA) have been revealed as important ripening markers in lemons. Therefore, this study proposes, for the first time, using near-infra-red spectroscopy (NIRS) as a rapid and non-destructive alternative to evaluate these quality traits in 'Fino' lemons (Citrus limon L. Burm) during ripeness. NIR spectra (950–1700 nm) of intact lemons collected from two different orchards at three ripening stages were acquired, while standard destructive methods were used to determine TSS and TA in the juice of each fruit. The prediction of the quality parameters was carried out using partial least squares regression (PLS-R) models. Three approaches were followed to validate the models: internal, external, and recalibrated external validation. The results following the first approach presented a good predictive performance for both quality parameters (TSS: R2 = 0.84, RMSEP = 0.42 and RPD = 2.5; TA: R2= 0.72, RMSEP = 0.45 and RPD = 2.0). When the external validation was performed, the best results were obtained for the TSS prediction using recalibrated models, maintaining good predictive performance accuracy (R2 = 0.74 and 0.67, RMSEP = 0.42 and 0.58, and RPD = 2.4 and 1.7). Regarding distinguishing different origins, models based on partial least squares discriminant analysis (PLS-DA) were externally validated, achieving 66.4% correct classification, respectively. Thus, applying NIR technology in the lemon fruit packinghouses is a promising alternative to improve fruit management and meet consumer demands
Chitosan and Other Edible Coatings with Antimicrobial Activity: Synthesis, Properties and Horticultural Applications
Full text linkAntimicrobial edible coatings for whole or fresh-cut fruits and vegetables based on natural biopolymers that serve as carriers of antimicrobial agents or that are inherently antimicrobial, such as chitosan, are increasingly gaining interest from researchers and industry due to their potential to maintain quality and safety. Additionally, edible coatings can also function as a barrier to water vapors and gases, regulating physiological aspects in fruit. Despite the substantial research progress in antimicrobial edible coatings for fresh and fresh-cut fruits and vegetables, the development of tailor-made solutions according to specific commercialization needs still represents a technological challenge due to important physical, physiological, and biochemical differences among the wide variety of fresh horticultural commodities. The development of edible films and coatings with antimicrobial activity requires knowledge of the chemical bases to develop optimized edible coating formulations, the effects of the coatings on different postharvest pathogens in in vitro studies and in different fruit matrices, as well as their effect on fruit quality during postharvest storage
Acoustic response discrimination of phulae pineapple maturity and defects using factor analysis of mixed data and machine learning algorithms
Full text linkAcoustic response is non-destructive evaluation technique that replicates the conventional method for determining
maturity by tapping the fruit. The physical (dimensions, color, firmness, and specific gravity) chemical
(TSS, %TA, and TSS/TA), and acoustic properties of Phulae pineapple were determined and used to classify the
maturity and defect, e.g. translucency flesh symptoms. Results showed that all physical parameters of the two
maturity stages were not significantly different (p > 0.05). Translucency flesh (TF) defects were observed in 23.5
% and 27.3 % of pineappls in the green and green-yellow stages, respectively. The dominant resonance frequency
(fn) of Phulae pineapple ranged of 0.057 to 3.010 kHz. All the physical, chemical, and acoustic properties were
used to classify for maturity and defects using the factor analysis (FA) technique and machine learning (ML).
Results showed that maturity was correctly classified at 84.0 % by all parameters, while elected non-destructive
parameters (color, specific gravity, and stiffness coefficients) showed lower results for distinguishing pineapples.
Random Forest (RF) provided a better classification than other MLs with 99.93 % accuracy of maturity classification,
while TF classification was 99.59 %. Results showed acoustic method integrated with ML was a fast
reliable, and cost effective technique for assessing Phulae pineapple qualit
Reducción del pardeamiento interno de la granada ‘Mollar de Elche’ durante la frigo-conservación mediante herramientas pre y postcosecha
Full text linkEn los últimos años, la corteza de la granada cv. Mollar de Elche está presentando un
pardeamiento interno tras el periodo de frigo-conservación. Aunque se desconocen las causas,
podrían deberse al cambio de las condiciones climatológicas durante el desarrollo del cultivo. Por
lo que es necesario conocer cómo se puede incidir, mediante tratamientos pre y postcosecha,
en atenuar la aparición del daño.
Para ello, se seleccionaron dos parcelas con diferente incidencia en campañas anteriores (P1:
baja y P2: alta). En ambas parcelas se estudió el efecto de aplicaciones de calcio más boro
(Ca+B) y cobre (Cu), comparándolo con árboles que no recibieron ningún tratamiento (CTL).
Las granadas, tras su recolección, se almacenaron a 5 y 9 ºC durante 4 y 8 semanas. Se evaluó,
en la zona de la corona, la incidencia del daño y la concentración de macro y micronutrientes en
ambas partes de la corteza.
La aparición del pardeamiento se manifestó desde la primera salida de frigo-conservación (4
semanas) con diferente comportamiento según la temperatura de conservación y la procedencia
de los frutos. A 9 ºC, la incidencia se redujo con respecto a 5 ºC, principalmente en la parcela
de alta incidencia (P2).
Además, en la P2, de entre los tratamientos empleados, Ca+B atenuó la alteración tras 4
semanas de almacenamiento. Tras 8 semanas, este tratamiento únicamente disminuyó el daño
en los frutos almacenados a 9 ºC, ya que a 5 ºC todos los frutos presentaron un elevado índice
de pardeamiento, donde ningún tratamiento influyó.
En la parcela de baja incidencia (P1), como sucedió en campañas anteriores, el pardeamiento
interno fue menor y cuando se presentó en mayor incidencia, tras 8 semanas almacenado a 5
ºC, ningún tratamiento redujo el pardeamiento
Habitat heterogeneity reduces abundance of invasive mealybugs in subtropical fruit crops
Full text linkThe simplification of agricultural landscapes has been associated with an increase in pest pressure. While monocultures increase the resources available for pests and may facilitate their dispersion, the lack of non-crop habitats may reduce the resources available for pest natural enemies. Herein, we tested which of these hypotheses, namely ‘resource concentration’ and ‘natural enemies’, can better explain the abundance of invasive mealybug pests in two subtropical fruit crops. For this aim, 17 persimmon orchards and 16 citrus orchards were sampled during three different seasons across two consecutive years. Using a model selection approach, we assessed the effects of the surrounding landscape (proportion of focal crops and semi-natural habitats at different distances) and inter-row ground cover vegetation on the abundance of mealybugs and their natural enemies. The proportion of focal crop in the landscape increased the abundance of mealybugs attacking both crops. This effect was found at closer distances (up to ~600 m) in citrus and at both closer and further distances (up to 1250 m) in persimmon. Non-crop habitats, both surrounding semi-natural habitats and ground cover vegetation, decreased the abundance of mealybugs by increasing the activity of their parasitoids in persimmon. Conversely, non-crop habitats did not decrease the abundance of the main mealybug species attacking citrus, likely because this mealybug species was not attacked by native or naturalized parasitoids. Synthesis and applications: Our models show that the increase in habitat heterogeneity at local and landscape scales can reduce the abundance of invasive mealybugs in subtropical crops via ‘resource concentration’ and ‘natural enemies’ mechanisms. Therefore, habitat diversification strategies should be considered in the conservation biological control of invasive mealybugs. Importantly, our findings also show that the presence of efficient natural enemies is critical to maximize their control through habitat diversification strategies