Wellington G. Campos

The management of bee communities by intercropping with flowering basil (Ocimum basilicum) enhances pollination and yield of bell pepper (Capsicum annuum)

Enhancements of floral resources in surrounding landscape and in local crop fields are expected to mitigate adverse human impacts on pollinator diversity and pollination services. We evaluated whether intercropping with flowering basil (Ocimum basilicum) increases the local abundance and richness of bees and improves fruit and seed production of bell pepper (Capsicum annuum). Fields of bell pepper were divided into intercropping (basil mixed with pepper) and single-cropping plots (only pepper). We also grew bell peppers in protected greenhouse in the presence and absence of beehives. The richness and abundance of visiting bees to pepper flowers were greater in the intercropped plots than the single-cropping plots. The increase in the number of bees visiting the peppers was due to the stronger attraction of Paratrigona lineata, Apis mellifera and Tetragonisca angustula to basil in the intercropping plots. The pepper fruits produced in the intercropping were wider, longer, and heavier and developed more seeds than the fruits produced by single-cropping. The same differences were observed between the fruits grown in greenhouse with and without beehives of P. lineata. We demonstrate that agricultural systems designed to attract and retain pollinators are more productive than growing pure stands. Our results also highlight the role of provisioning floral resources to enhance bee conservation and management in anthropogenic ecosystems.

Does the age of the host plant modulate migratory activity of Plutella xylostella

Ephemeral plants and most tropical crops are available to herbivore insects as irregular and unpredictable patches of resources. Insects that exploit patched habitats usually have well‐developed migratory ability, and migration is a fundamental process in the cycle of colonization and extinction of the local populations. We ask here whether Plutella xylostella (Lepidoptera: Yponomeutidae) uses the aging process of the host plant to modulate its migratory activity. The insect was reared in the laboratory on the leaves from the middle estratum (fourth expanded leaves) of cabbage (Brassica oleraceae var. capitata) of various ages, and on leaves from three strata of the mature plant. Females that spent their larval phase in young and tender plants lived for a shorter period of time and laid eggs immediately after metamorphosis. In contrast, mature plants, particularly the new leaves from the superior stratum, favored the development of adult phenotypic traits that occur in migratory forms, such as reduced body size, increased longevity and delayed reproductive activity. We suggest that the lesser nutritional quality and the short temporal persistence of mature plants are selective forces favoring individuals that are better prepared to abandon their habitat soon after emergence. Plutella xylostella may use the predictable ontogenetic changes of the ephemeral host plant to modulate its physiological and behavioral migratory ability.

Induced response against herbivory by chemical information transfer between plants

Plantas respondem ao ataque de herbivoros e patogenos com liberacao de compostos orgânicos volateis. Essas moleculas funcionam como defesas indiretas quando atraem inimigos naturais dos herbivoros e assim beneficiam a planta emissora. Uma questao controversa e se plantas vizinhas nao-atacadas captam esses volateis e respondem aumentando suas barreiras defensivas contra um ataque iminente. Apesar do seu forte apelo popular e da Talking Trees Hypothesis estar completando 25 anos, so recentemente os mais ceticos estao sendo convencidos. Tem-se aceitado que respostas induzidas pela trasnferencia de informacao entre plantas ocorrem em pelo menos dois sistemas planta-herbivoro. No entanto, o grau de generalizacao do fenomeno e a dimensao da sua importância ecologica e evolutiva permanecem desconhecidos. Uma recente abordagem multidisciplinar, integrando Biologia Molecular, Bioquimica e Fisiologia a Ecologia, acena com novas e mais poderosas ferramentas metodologicas para esclarecer os processos de biossintese, emissao, transporte e recepcao dos sinais pelas plantas. Essa abordagem tem fornecido o suporte mecanicista adicional as evidencias ecologicas da defesa induzida da planta, manifestada e mensurada mediante respostas ecofisiologicas e comportamentais dos insetos herbivoros.

Prospection and Fungal Virulence Associated with Mahanarva spectabilis (Hemiptera: Cercopidae) in an Amazon Silvopastoral System

Abstract In Brazil, pastures of Brachiaria grasses are often attacked by the spittlebug Mahanarva spectabilis (Distant) (Hemiptera: Cercopidae). Biological control of this pest insect is rarely used, in part because of a lack of diversity in commercialized pathogens effective against such pests. However, fungal infection of M. spectabilis has been noted in some tropical silvopastoral systems, which rarely have problems with pest insects. This study surveyed the fungi found in association with M. spectabilis in a silvopastoral system in Brazil and made a preliminary assessment of their virulence. Infected spittlebugs were collected in a silvopastoral system in Brazil, from which 5 types of fungi were isolated and identified by morphological analysis. Conidia of each wild fungus and a commercial strain of Metarhizum anisopliae (Metschn.) Sorokin (Clavicipitaceae) were diluted in a 1% NaCl solution at a concentration of 1×104 conidia per mL. In the laboratory, eggs and nymphs of M. spectabilis were placed in acrylic boxes within a climate-controlled chamber at 25 °C. In a non-acclimatized greenhouse, eggs and nymphs were placed on potted Brachiaria decumbens Stapf (Poaceae). Solutions of the 6 fungi and a control (pure saline) were applied to M. spectabilis in both conditions (acrylic box in laboratory and potted Brachiaria in a greenhouse). The most virulent fungi (UFMG 11443 and 11444) caused more than 90% of unviable eggs and mortality of nymphs. Other fungi tested (UFMG 11440, 11441, and 11442) were equally or more effective than the commercial M. anisopliae, causing over 50% unviable eggs or nymph mortality. All isolated fungi showed potential for use as biological control agents against M. spectabilis.

Does mechanical damage on soybean induces the production of flavonoids

The response of plants to grazing includes the production of chemical defense compounds such as proteases inhibitors and secondary metabolites as flavonoids, which makes them less palatable to feeding and negatively affecting the physiology of insects. The aim of this study was to evaluate the phytochemical response of soybean cultivars (Glycine max (L.) Merrill) resistant (IAC-17, IAC-24) and susceptible (IAC-P1) to insects after mechanical damage. These cultivars were mechanically injured, and after 24 hours samples of these plants were analyzed by HPLC to identify and quantify flavonoids. The flavonoids daidzein, quercetin, and rutin were quantified, with the highest concentration of daidzin in soybean cultivars after mechanical damage. Rutin was biosynthesized by IAC-24. The cultivars IAC-PL1, IAC-17, and IAC-24 did not show a flavonoid response to mechanical damage. The soybean cultivars are not dependent on mechanical damage to produce flavonoids.

Protease inhibitory, insecticidal and deterrent effects of the trypsin-inhibitor benzamidine on the velvetbean caterpillar in soybean

The recognition of protease inhibitors with insecticidal activity is important as a basis for the development of mimetic peptides with potential use as biorational insecticides. We sprayed benzamidine on soybean plants and assessed whether this potent synthetic trypsin-inhibitor has protease inhibitory, insecticidal and deterrent effects on the velvetbean caterpillar Anticarsia gemmatalis Hübner (Lepidoptera: Erebidae). Activity of trypsin inhibition in soybean leaves was increased and total proteolytic activity in the midgut extract from larvae fed on these leaves was reduced by benzamidine. Different concentrations of benzamidine sprayed on the plant caused approximately 50 % of larval mortality, and larval choice and moth preference and oviposition were all negatively affected. Low concentrations of benzamidine increased mortality and hindered insect choice and oviposition as well as higher doses. Since many synthetic protease inhibitors are usually expensive, small doses of benzamidine may be effective to protect soybean against A. gemmatalis attack. Our results highlight the potential of synthetic protease inhibitors for insecticidal and deterrent purposes in insect pest management.

Silicon-mediated resistance against specialist insects in sap-sucking and leaf-chewing guilds in the Si non-accumulator collard

Soil amendment with Silicon (Si) can increase plant resistance against insect herbivores, but the underlying mechanisms remain unclear. The mechanical resistance hypothesis (MRH) states that Si accumulated in epidermal cells directly and passively protects against herbivores by creating a mechanical barrier. The physiological resistance hypothesis (PRH) states that Si enhances resistance by activating plant biochemical and physiological processes. We tested both hypotheses by manipulating Si fertilization of the Si non‐accumulator collard, Brassica oleracea L. cv. acephala (Brassicaceae). Then, we assessed functional and ultrastructural plant responses and the developmental and reproductive performance of the leaf‐chewing larvae of the diamondback moth, Plutella xylostella L. (Lepidoptera: Plutellidae), and the sap‐sucking cabbage aphid, Brevicoryne brassicae L. (Hemiptera: Aphididae). There was a 20% increase in leaf Si content. Silicon deposition in epidermal cells was identified by confocal microscopy and directly coincided with lower performance of P. xylostella, but did not affect B. brassicae. On the other hand, we found no unequivocal evidence that Si‐mediated changes in primary and secondary metabolism improved plant resistance against the insects. Negative mechanical effects of Si on the insects may have masked beneficial effects of increased water, nitrogen, and mineral contents in Si‐treated collards. Silicon did not change leaf contents of hemicellulose, cellulose, and lignin. Although Si‐mediated increases in leaf glucosinolates (GLS) correlated with lower larval performance and higher oviposition preference of P. xylostella, both P. xylostella and B. brassicae are highly specialized in overcoming such secondary metabolites. Thus, mechanical resistance may have impaired P. xylostella, rather than the Si‐mediated increase in GLS. We suggest that the PRH may depend on the degree of insect feeding specialization, so that toxic Si‐mediated defenses may be more efficient against unadapted polyphagous herbivores. For them, a toxic barrier may be added to the mechanical resistance.

Purification and characterization of trypsin produced by gut bacteria from Anticarsia gemmatalis

Purification of active trypsin in the digestive process of insects is essential for the development of potent protease inhibitors (PIs) as an emerging pest control technology and research into insect adaptations to dietary PIs. An important aspect is the presence of proteolytic microorganisms, which contribute to host nutrition. Here, we purified trypsins produced by bacteria Bacillus cereus, Enterococcus mundtii, Enterococcus gallinarum, and Staphylococcus xylosus isolated from the midgut of Anticarsia gemmatalis. The trypsins had a molecular mass of approximately 25 kDa. The enzymes showed increased activity at 40°C, and they were active at pH values 7.5-10. Aprotinin, bis-benzamidine, and soybean Kunitz inhibitor (SKTI) significantly inhibited trypsin activity. The l-1-tosyl-amido-2-phenylethylchloromethyl ketone (TPCK), pepstatin A, E-64, ethylenediamine tetraacetic acid, and calcium ions did not affect the enzyme activity at the concentrations tested. We infer the purified trypsins do not require calcium ions, by which they differ from the trypsins of other microorganisms and the soluble and insoluble trypsins characterized from A. gemmatalis. These data suggest the existence of different isoforms of trypsin in the velvetbean caterpillar midguts.