Various pesticide residues can be found in different bee colony components. The queen larvae of honey bee (
L.) receive non-contaminated food from nurse bees. However, there is little knowledge about ...how pesticide residues affect developing bees. Additionally, little is known about the migration of lipophilic pesticides between bee matrices. While wax, royal jelly (RJ), and bee larvae are chemically distinct, they all contain lipids and we expected the lipophilic fungicide tebuconazole to be absorbed by different contacting materials. Our aim was to analyze the translocation of tebuconazole residues from queen cell wax to RJ, queen larvae, and newly emerged queens and to evaluate its potential risk to queens. We demonstrated the potential for the migration of tebuconazole from wax to RJ, with a strong dilution effect from the original contamination source. No residues were detected in queen bee larvae and newly emerged queens, indicating that the migration of tebuconazole probably did not directly endanger the queen bee, but there was some risk that tebuconazole might still affect the homeostasis of developing bees.
Bumblebee species with declining population trends tend to show lower genetic diversity levels than stable species. The observed difference might be explained by abundance differences, with declining ...bumblebee species having lower genetic diversity levels simply due to their lower local species abundances. However, whether this holds true is not known. Here, we investigated whether bumblebee local abundances determines population genetic diversity levels. Therefore, local species abundances were measured for bumblebee species at four locations in Belgium and two locations in Estonia during bumblebee foraging years 2013-2017. These locations and countries were chosen to ensure the greatest possible variance in both local abundances and population trends for these species. Hence, genetic diversity levels were obtained for seven species by genotyping collected specimens with 16 microsatellites. Our results showed that the observed patterns in genetic diversity did not depend on local species abundance. So, although declining bumblebee species can become locally abundant, they will still show lower genetic diversity levels than stable species. This result implies that measuring bumblebees' local abundance cannot be used to directly determine the health status of a population. Furthermore, this result has also major impact on future conservation strategies as increasing the genetic diversity levels of declining species will be very difficult, and habitat quality should be high to maintain their populations, otherwise these species are doomed to disappear first.
Yield losses of crops due to plant pathogens are a major threat in all agricultural systems. In view of environmental issues and legislative limitations for chemical crop protection products, the ...need to design new environmentally friendly disease management strategies has gained interest. Despite the unique capability of green leaf volatiles (GLVs) to suppress a broad spectrum of plant pathogens, their capacity to control the potato late-blight-causing agent
has not been well studied. This study addresses the potential role of the GLV Z-3-hexenyl acetate (Z-3-HAC) in decreasing the severity of late blight and the underlying gene-based evidence leading to this effect. Nine-week-old potato plants (
L.) were exposed to Z-3-HAC before they were inoculated with
genotypes at different time points. These pre-exposed potato plants exhibited slower disease development after infection with the highly pathogenic genotype of
(EU-13-A2) over time. Qualitative assessment showed that the exposed, infected plants possessed significantly lower sporulation intensity and disease severity compared to the control plants. Hypersensitive response (HR)-like symptoms were observed on the treated leaves when inoculated with different pathogen genotypes. No HR-like lesions were detected on the untreated leaves after infection. It was shown that the transcript levels of several defense-related genes, especially those that are involved in reactive oxygen species (ROS) production pathways were significantly expressed in plants at 48 and 72 h postexposure to the Z-3-HAC. The current work provides evidence on the role of Z-3-HAC in the increased protection of potato plants against late blight through plant immunity and offers new opportunities for the sustainable control of potato diseases.
Agricultural landscapes usually provide higher quantities of single-source food, which are noticeably lacking in diversity and might thus have low nutrient value for bumble bee colony development. ...Here, in this study, we analysed the pollen foraging preferences over a large territory of a heterogeneous agricultural landscape: southern Estonia. We aimed to assess the botanical diversity of bumble bee food plants in the spring time there. We looked for preferences for some food plants or signs of food shortage that could be associated with any particular landscape features. For this purpose, we took Bombus terrestris commercial hives to the landscape, performed microscopy analyses and improved the results with the innovative DNA metabarcoding technique to determine the botanical origin of bumble bee-collected pollen. We found high variability of forage plants with no strong relationship with any particular landscape features. Based on the low number of plant species in single flights, we deduce that the availability of main forage plants is sufficient indicating rich forage availabilities. Despite specific limitations, we saw strong correlations between microscopy and DNA metabarcoding data usable for quantification analyses. As a conclusion, we saw that the spring-time vegetation in southern Estonia can support bumble bee colony development regardless of the detailed landscape structure. The absence of clearly dominating food preference by the tested generalist bumble bee species B. terrestris makes us suggest that other bumble bee species, at least food generalists, should also find plenty of forage in their early development phase.
Late blight caused by the oomycete Phytophthora infestans is considered the biggest threat to potato farming worldwide. For susceptible cultivars, the disease is often managed by frequent ...applications of fungicides to reduce yield loss. The use of bio-based compounds that interfere with biologically active systems is an innovative strategy for improving disease management. In the present work, the control of P. infestans infection on potatoes by potassium phosphite (KPhi) combined with recommended and reduced doses of active ingredients (Ais) from different fungicides was evaluated. The protective effects of different combinations were initially assessed in vivo and subsequently compared with a greenhouse screening. The active ingredients cyazofamid (CFD) and mancozeb (MCB), used at recommended and reduced doses, were less effective at reducing P. infestans infections than when combined with KPhi. In greenhouse trials, CFD, mandipropamid (MPD) and MCB at recommended doses were the most effective treatments when combined with KPhi; meanwhile, the combination of KPhi with azoxystrobin (AZ), benthiavalicarb-isopropyl/mancozeb (ISO/MCB), and CFD at reduced doses exhibited strong protective activity compared to other similar combinations. This decreased the severity of infection by P. infestans up to ~89%. Greenhouse experiments also demonstrated that a combination of KPhi and CFD at both doses caused the highest reduction in disease severity (up to ~90%) within 35 days of infection. In microplot experiments, KPhi delayed the progression of late blight in susceptible potato varieties; therefore, in the combined treatments AUDPC values were significantly lower than those obtained after applications with CFD doses, providing sufficient protection against late blight. Our data suggest that optimizing the formulation with addition of KPhi could result in a lower recommended dose. This would result in a reduction of the active compounds of the fungicides in potato farming. Furthermore, the impact of KPhi on late blight development makes it a potential component for incorporation into an integrated pest management system.
Environmental thermal conditions play a major role at all levels of biological organization; however, there is little information on noxious high temperature sensation crucial in behavioral ...thermoregulation and survival of small ectothermic animals such as insects. So far, a capability to unambiguously encode heat has been demonstrated only for the sensory triad of the spike bursting thermo- and two bimodal hygro-thermoreceptor neurons located in the antennal dome-shaped sensilla (DSS) in a carabid beetle. We used extracellular single sensillum recording in the range of 20-45°C to demonstrate that a similar sensory triad in the elaterid
also produces high temperature-induced bursty spike trains. Several parameters of the bursts are temperature dependent, allowing the neurons in a certain order to encode different, but partly overlapping ranges of heat up to lethal levels in a graded manner. ISI in a burst is the most useful parameter out of six. Our findings consider spike bursting as a general, fundamental quality of the classical sensory triad of antennal thermo- and hygro-thermoreceptor neurons widespread in many insect groups, being a flexible and reliable mode of coding unfavorably high temperatures. The possible involvement of spike bursting in behavioral thermoregulation of the beetles is discussed. By contrast, the mean firing rate of the neurons in regular and bursty spike trains combined does not carry useful thermal information at the high end of noxious heat.
Terminal investment hypothesis is a longstanding theoretical idea that organisms should increase their reproductive effort as their prospects for survival and reproduction decline. However, numerous ...attempts to test the terminal investment in reproduction have yielded contradictory results. This study reports an experimental confirmation of the terminal investment hypothesis. It was predicted that immune-challenged yellow mealworm beetles (Tenebrio molitor) are more likely to follow terminal investment strategy when their food resources are limited. Our results suggest the key role of food resources while making decisions to follow a terminal investment strategy. We found that male individuals invested in their sexual attractiveness at the expense of immune response and survival when food was not available. In contrast, the beetles did not decrease their lifespan and did not invest in the attractiveness of their sex odours under conditions of food ad libitum. Our results show the importance of food availability and quality in understanding the evolution of reproductive strategies.
Significant between-individual variation in resting metabolic rate (RMR) of animals is a widespread phenomenon that may have important implications for our understanding of variation in behavior and ...animal personality. By using wild caught mealworm beetles,
Tenebrio molitor
, we examined the relationships among survival rate under predator tests, individual response latency time to become immobile under the risk of predation, duration of immobility time, and RMR. Individuals with higher levels of RMR were bold, and bold individuals were found to be more exposed to the risk of bird predation. We found that RMR was positively correlated with the latency of immobility response and negatively correlated with the total duration of immobility. The correlation between behavioral responses suggests a behavioral syndrome in the anti-predator behavior of
T. molitor
. The results indicate that energy metabolism may be part of a syndrome that involves behavior and life history traits in animals.
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