Profile of Terpenoid Compounds Mediating a Plant-Herbivore Interaction: Screening by Static Headspace Solid-Phase Microextraction-Gas Chromatography/Q-ToF Mass Spectrometry.

Conotrachelus dimidiatus (Coleoptera: Curculionidae) interacts with immature guava fruits (Psidium guajava L.) for feed, sleep, mate and oviposit. Determination of the volatile organic compounds (VOCs) emitted by the insect and immature fruits can help improve understanding of plant-insect and intraspecific insect interactions between females and males of C. dimidiatus. Daytime fruit setting emissions of immature guava consist mainly of limonene, caryophyllene, and aromadendrene. In addition to the host's volatiles, the aim of this study was to assess the VOCs released by the insect. Static headspace-solid phase microextraction (SHS-SPME), combined with gas chromatography/quadrupole time of flight mass spectrometry (GC/Q-ToF-MS), allowed the identification of the C10 terpenoids: grandlure I, II, II, IV, grandisoic acid, papayanol and papayanal bioactive compounds released by female and male C. dimidiatus under laboratory conditions. These chemical compounds are candidates for the preparation of a lure formulation.

Behavioral and Electroantennographic Responses of Adults of Guava Weevil, Conotrachelus dimidiatus (Coleoptera: Curculionidae), to Synthetic Host-Associated and Conspecific Volatiles.

Immature guava fruits (Psidium guajava L.) of commercial orchards in Mexico are affected by adults of Conotrachelus dimidiatus (Champion) causing economic losses to producers. The aim of this study was to assess the behavioral and electrophysiological responses of the weevil to selected semiochemicals emitted by the host plant fruit and to conspecifics. Volatile organic compounds isolated from host plant as ß-caryophyllene, (S)-(-)-limonene, hexanal, and nonanal significantly attracted adults of both sexes in behavioral bioassays. Electroantennogram recordings showed largest responses to papayanal and grandlure III + IV released by C. dimidiatus and C. nenuphar, respectively. Our results indicate that behavioral and electroantennographic assays using synthetic compounds from host plant volatiles and insect volatile pheromones produce olfactometry and electroantennographic responses in C. dimidiatus. This is the first report of intraspecific chemical communication in this weevil. We discuss the significance of these responses for the natural behavior in guava orchards and their potential use in a pest management strategy.

Aggregation pheromone of Metamasius spinolae (Coleoptera: Curculionidae): chemical analysis and field test.

Male Metamasius spinolae (Gylh.) produce several volatile compounds that are likely constituents of its aggregation pheromone. These compounds were identified by volatile collections and gas chromatography (GC), followed by coupled gas chromatography-mass spectrometry (GC-MS), as 2-methyl-4-heptanone [1], 6-methyl-2hepten-4-one [2], and 2-hydroxy-2-methyl-4-heptanone [3]. Preliminary field experiments using synthetic racemates of these compounds showed that significantly more adult cactus weevils were caught in traps baited with the major single compound three or the 2 + 3 binary combination than in unbaited control traps. However, highest trap efficacy occurred with the 1 + 2 binary combination and a blend of all three synthetic compounds plus prickly pear. Potential uses for the cactus weevil pheromone and possible ways to increase trap captures are discussed.

Sunlight transmitted by colored shade nets on photosynthesis and yield of cucumber / Luz solar transmitida por malhas coloridas sobre fotossíntese e rendimento de pepino

ABSTRACT: Black shading nets are widely used in the protected cultivation of vegetables as a technique for controlling light and temperature, while the colored shading nets, with special optical properties to improve the use of solar radiation, appeared recently in the agricultural plastics market. Light quality transmitted by gray, aluminized, pearl, blue, red and black (control) nets with 30% shade was evaluated, as well as its effects on photosynthetic properties and fruits production of cucumber plants. Treatments (shade nets) were established under a randomized complete block design with four repetitions. The red net transmitted 23.7 and 40.3% more photosynthetic photon flux density (400 to 700nm) and red light (600 to 700nm) and the blue net transmitted 36% more blue light (400 to 500nm) in comparison with the respective transmissions of black net. All nets increased the photosynthetic responses: transpiration, stomatal conductance and CO2 assimilation, observed in plants grown under black net. Leaf greenness (41.6 SPAD units) and foliar area (90dm2) increased 22.8 and 38.9% with the red net, while the dry weight of leaf (52.5g) increased 21.9% with pearl net. Pearl, red, aluminized and blue nets showed to be viable alternatives because the production of fruit increased in 71, 48, 46 and 46%, respectively, in comparison with the conventional black net (52t ha-1).

RESUMO: As malhas de sombreamento preto são amplamente utilizadas no cultivo protegido de hortaliças como uma técnica para controlar a luz e a temperatura; enquanto as malhas de sombreamento coloridas, com propriedades ópticas especiais para melhorar o uso da radiação solar, apareceram recentemente no mercado de plásticos agrícolas. A qualidade de luz transmitida por malhas cinza, aluminizada, pérola, azul, vermelha e preta (controle) com 30% de sombreamento foi avaliada, assim como seus efeitos nas propriedades fotossintéticas e na produção de frutos de plantas de pepino. Os tratamentos (malhas de sombreamento) foram estabelecidos sob o desenho de blocos completos casualizados, com quatro repetições. A malha vermelha transmitiu 23,7 e 40,3% mais densidade de fluxo de fótons fotossintéticos (400 a 700nm) e luz vermelha (600 a 700nm) e a malha azul transmitiu 36% mais luz azul (400 a 500nm) em comparação com as respectivas transmissões de malha preta. Todas as malhas aumentaram as respostas fotossintéticas: transpiração, condutância estomática e assimilação de CO2, observadas em plantas cultivadas sob malha preta. O verde da folha (41,6 unidades SPAD) e a área foliar (90dm2) aumentaram 22,8 e 38,9% com a malha vermelha, enquanto o peso seco da folha (52,5g) aumentou 21,9% com a malha pérola. As malhas pérola, vermelha, aluminizada e azul mostraram-se como alternativas viáveis, pois a produção de frutos aumentou em 71, 48, 46 e 46%, respectivamente, em comparação à malha convencional preta (52t ha-1).