Prevailing abiotic conditions may positively or negatively impact insects at both the individual and population levels. For example while moderate rainfall and wind velocity may provide conditions ...that favour development, as well as movement within and between habitats, high winds and heavy rains can significantly decrease life expectancy. There is some evidence that insects adjust their behaviours associated with flight, mating and foraging in response to changes in barometric pressure. We studied changes in different mating behaviours of three taxonomically unrelated insects, the curcurbit beetle, Diabrotica speciosa (Coleoptera), the true armyworm moth, Pseudaletia unipuncta (Lepidoptera) and the potato aphid, Macrosiphum euphorbiae (Hemiptera), when subjected to natural or experimentally manipulated changes in atmospheric pressure. In response to decreasing barometric pressure, male beetles exhibited decreased locomotory activity in a Y-tube olfactometer with female pheromone extracts. However, when placed in close proximity to females, they exhibited reduced courtship sequences and the precopulatory period. Under the same situations, females of the true armyworm and the potato aphid exhibited significantly reduced calling behaviour. Neither the movement of male beetles nor the calling of armyworm females differed between stable and increasing atmospheric pressure conditions. However, in the case of the armyworm there was a significant decrease in the incidence of mating under rising atmospheric conditions, suggesting an effect on male behaviour. When atmospheric pressure rose, very few M. euphorbiae oviparae called. This was similar to the situation observed under decreasing conditions, and consequently very little mating was observed in this species except under stable conditions. All species exhibited behavioural modifications, but there were interspecific differences related to size-related flight ability and the diel periodicity of mating activity. We postulate that the observed behavioral modifications, especially under decreasing barometric pressure would reduce the probability of injury or death under adverse weather conditions.
The need for basic information on tropical crop pollinators remains a key priority. Here, we used a dataset on Brazilian bee-crop interactions to determine important bee species for crop pollination ...and discuss their management in Brazilian croplands. We developed an analytical approach to select key bee species and genera from datasets based on different criteria, selecting only interactions reported as effective pollination events. Data on pollination included 261 records of unique crop-pollinator interaction, 144 bee species, and 23 crops. Despite the importance of social species, solitary bees accounted for 56% of the observed interactions. Of the 14 most important species, eight are solitary and six are social. A few of the selected species are already reared in Brazil, e.g., honeybees and some stingless bees, but practical knowledge on their management for crop pollination is poorly disseminated among farmers, hindering such an application.
Co-infestations by herbivores, a common situation found in natural settings, can distinctly affect induced plant defenses compared to single infestations. Related tritrophic interactions might be ...affected through the emission of changed blends of herbivore-induced plant volatiles (HIPVs). In a previous study, we observed that the infestation by red spider mite (
Oligonychus ilicis
) on coffee plants facilitated the infestation by white mealybug (
Planococcus minor
), whereas the reverse sequence of infestation did not occur. Here, we examined the involvement of the jasmonate and salicylate pathways in the plant-mediated asymmetrical facilitation between red spider mites and white mealybugs as well as the effect of multiple herbivory on attractiveness to the predatory mite
Euseius concordis
and the ladybug
Cryptolaemus montrouzieri
. Both mite and mealybug herbivory led to the accumulation of JA-Ile, JA, and
cis
-OPDA in plants, although the catabolic reactions of JA-Ile were specifically regulated by each herbivore. Infestation by mites or mealybugs induced the release of novel volatiles by coffee plants, which selectively attracted their respective predators. Even though the co-infestation by mites and mealybugs resulted in a stronger accumulation of JA-Ile, JA and SA than the single infestation treatments, the volatile emission was similar to that of mite-infested or mealybug-infested plants. However, multiple infestation had a negative impact on the attractiveness of HIPVs to the predators, making them less attractive to the predatory mite and a repellent to the ladybug. We discuss the potential underlying mechanisms of the susceptibility induced by mites, and the effect of multiple infestation on each predator.
Citrus insect pests has grown worldwide, concerning entomologists and farmers especially because of the high demand for food that makes it to our tables. The use of pesticides brought several issues, ...such as the negative impacts on the human health, pollution, and insect resistance. In this context, more environmentally-friendly strategies have been demanded by governments and consumers. In this review, we present three remarkable examples of pest management in Brazil that involved many researchers from different expertise areas to develop more sustainable strategies to reduce the damages to citrus production. The case studies consisted of high-quality research funded by the Brazilian government and private institutions. In the first case, we report on the monitoring of the citrus fruit borer with sex pheromones, which significantly improved the control of this insect pest. Based on behavioral studies, it was recommended that delta traps containing pheromone attractant be installed on the upper third part of the plant. A recent study indicates the promising use of the egg parasitoid
Trichogramma atopovirilia
for biological control. In the second case, the biocontrol of the leafminer using
Ageniaspis citricola
is discussed. The insect pest was introduced into Brazil in 1996, causing losses of up to 60 kg of fruit per tree. The solution for this problem was the introduction of the parasitoid
Ageniaspis citricola
, originally from Asia. The pest was successfully controlled by the parasitoid, which was able to adapt to different citrus-producing regions in Brazil. Finally, the most emblematic successful case in Brazil is the biological control of the Asian citrus psyllid (ACP),
Diaphorina citri
, using
Tamarixia radiata
. ACP is the most important citrus pest because it causes indirect damage by transmitting the gram-negative bacteria that cause HLB (huanglongbing) in citrus areas. HLB is a vicious disease that has no cure: after being infected, the plants present chlorosis of the leaves, production of yellow shoots, and die within 2–3 years. The combination of laboratory tests, insect monitoring and computational modeling showed the efficacy of
T. radiata
against
D. citri
, which reduces the number of infected trees.
The guava weevil, Conotrachelus psidii is an aggressive pest of guava (Psidium guajava L.) that causes irreparable damages inside the fruit. The volatile compounds of male and female insects were ...separately collected by headspace solid-phase microextraction or with dynamic headspace collection on a polymer sorbent, and comparatively analyzed by GC-MS. (1R,2S,6R)-2-Hydroxymethyl-2,6-dimethyl-3-oxabicyclo4.2.0octane (papayanol), and (1R,2S,6R)-2,6-dimethyl-3-oxabicyclo4.2.0octane-2-carbaldehyde (papayanal) were identified (ratio of 9:1, respectively) as male-specific guava weevil volatiles. Papayanal structure was confirmed by comparison of spectroscopic (EIMS) and chromatographic (retention time) data with those of the synthetic pure compound. The behavioral response of the above-mentioned compounds was studied in a Y-tube olfactometer bioassay, and their role as aggregation pheromone candidate components was suggested in this species.
Diabrotica speciosa (Germar) and Diabrotica viridula F. (Coleoptera: Chrysomelidae) are the two most abundant species of the genus in South America, and belong to the fucata and virgifera groups, ...respectively. Here, we characterize the dimorphism of the setae present on the basitarsi of males and females of these species. Dimorphism was confirmed in both species, and it was related to the presence of adhesive setae exclusively in males, which possess these structures on the basal tarsomeres of the pro- and mesothoracic legs.
The garden fleahopper, Microtechnites bractatus (Say) (Hemiptera: Miridae), is associated with several cultivated plant species and, despite its economic importance, little is known about its ...development and performance in such hosts. We described here, the morphology of immature stages, and evaluated the biology of M. bractatus in beans, potatoes, white clover, alfalfa, and wheat. The bioassays were carried out in the laboratory under controlled temperature (25±2ºC), humidity (UR70±15%), and photoperiod (12L:12D). The eggs of M. bractatus are elongated and slightly curved, without respiratory projections and light yellow in color, becoming dark at the end of the incubation period. Nymphs present an oval-shaped body, a reddish color that intensifies along with the development and dimorphic wing pads in the fifth instar. In the bioassays, the host plants influenced the biological aspects of M. bractatus, both in the immature and adult stages. Nymph survival was higher in clover and alfalfa, while in wheat, it was lower. Clover-fed insects had the longest longevity. The fecundity parameters and egg viability were favored in insects that fed on clover and alfalfa. The fertility life table showed that feeding M. bractatus with clover provides a higher net reproduction rate (R0) and a higher finite ratio of population increase (λ). This study contributes to bioecological and behavioral studies on M. bractatus and provides data for the recognition and characterization of individuals in the immature stage.
Summary
The beneficial features of Bacillus thuringiensis (Bt) are not limited to its role as an insecticide; it is also able to promote plant growth interacting with plants and other plant ...growth‐promoting rhizobacterium (PGPR). The PGPR Bt strain RZ2MS9 is a multi‐trait maize growth promoter. We obtained a stable mutant of RZ2MS9 labelled with green fluorescent protein (RZ2MS9‐GFP). We demonstrated that the Bt RZ2MS9‐GFP successfully colonizes maize's roots and leaves endophytically. We evaluated whether RZ2MS9 has an additive effect on plant growth promotion when co‐inoculated with Azospirillum brasilense Ab‐V5. The two strains combined enhanced maize's roots and shoots dry weight around 50% and 80%, respectively, when compared to the non‐inoculated control. However, non‐differences were observed comparing RZ2MS9 alone and when co‐inoculated with Ab‐V5, In addition, we used co‐inoculation experiments in glass chambers to analyse the plant's volatile organic compounds (VOCs) production during the maize‐RZ2MS9 and maize‐RZ2MS9‐Ab‐V5 interaction. We found that the single and co‐inoculation altered maize's VOCs emission profile, with an increase in the production of indoles in the co‐inoculation. Collectively, these results increase our knowledge about the interaction between the Bt and maize, and provide a new possibility of combined application with the commercial inoculant A. brasilense Ab‐V5.
According to the theory of optimal foraging and preference–performance hypothesis, herbivores usually select plant hosts that benefit themselves or their offspring. We investigated the hypothesis ...that gravid females of the cucurbit beetle
Diabrotica speciosa
use volatiles derived from non-infested maize plants and herbivore-infested plants under attack by their conspecific immatures and adults in selecting a host for oviposition. The response of
D. speciosa
females to volatiles was quantified for the following treatments: (i) non-infested plants; (ii) plants infested by larvae (root-infested); (iii) plants infested by adults (leaf-infested); and (iv) plants infested by larvae and adults (leaf + root-infested). We also assessed if females were able to identify conditions of competition and host adequacy for offspring by means of chemical cues emitted by these plants. The results indicated that the presence of
D. speciosa
conspecifics on maize plants triggered the emission of volatiles, which influenced host selection for oviposition. Gravid females avoided both plants infested by larvae and plants infested by larvae and adults. Leaf-infested plants did not affect the host-selection behavior of females. Weight gain was higher in larvae kept on non-infested and leaf-infested plants than on root-infested or root + leaf-infested plants, indicating that female preference is related to its offspring performance.
Graphical Abstract
Synthesis of the effects of volatile organic compounds (VOCs) produced by uninfested, leaf-infested, root-infested and leaf+root-infested corn plants on the host-choice behavior of adults and performance of
Diabrotica speciosa
larvae
Liogenys fusca is a rizophagous insect pest in various crops of economic importance in Brazil. Here we investigated the morphology of immature stages and mating behavior of this species. The ...redescription of the 3rd instar larvae of L. fusca in this work allows identification and registration of occurrence independently of adults, which occur sporadically in a certain period of the year. Male and female of L. fusca remained confined in the soil during the day and exited between 19:00 and 23:30h. The copulations occurred between 19:30 and 21:00h, and were characterized by a typical behavioral sequence. Copulation durations in L. fusca lasted on average 512.23s. Adults were observed feeding before the copulations on leaves and inflorescences of plant species belonging to the family Anacardiaceae, Myracrodruon urundeuva, Schinus terebinthifolius, Astronium fraxinifolium and Anacardium occidentale.
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