The male-produced sex pheromone from the Brazilian rice stalk stink bug Tibraca limbativentris is reported. Olfactometer bioassays with sexually mature males and females showed that males attracted females, which suggests that males release a sex pheromone. Males were not attracted to either sex, nor were females attractive to conspecific females. Attraction of the females to males was highest at night. The headspace volatiles collected from male and female bugs were analyzed by gas chromatography (GC) and GC-mass spectrometry. Two male-specific compounds were identified as isomers of 1'S-zingiberenol, whereas a series of defensive compounds were identified in extracts from both sexes. Zingiberenol has three chiral centers, and the nonselective syntheses used produced two groups of isomers, zingiberenol I containing four isomers, namely (1RS,4RS,1'R)-4-(1',5'-dimethylhex-4'-enyl)-1-methylcyclohex-2-en-1-ol, and zingiberenol II containing the other four isomers, namely (1RS,4RS,1'S)-4-(1',5'-dimethylhex-4'-enyl)-1-methylcyclohex-2-en-1-ol. Both groups of stereoisomers were more attractive than hexane controls. The absolute configuration of the insect-produced pheromonal components remains to be elucidated, but the 1'S stereochemistry was established for at least one of the isomers.

Based on previous photosynthesis studies, adult Mexican bean beetles, Epilachna varivestis Mulsant, produce a different physiological response to injury in soybean than other insect defoliators. In 1993 and 1994, we conducted experiments to determine the nature and extent of photosynthetic rate reductions in soybean, Glycine max (L.) Merrill, and dry bean, Phaseolus vulgaris L. We used a randomized complete block design for all experiments. In most experiments, treatments were an uncaged, uninjured leaflet; a caged, uninjured leaflet; and a caged, injured leaflet. Treatments were replicated >5 times. Experimental units were individual trifoliolate leaflets. Four to 8 larvae or adults were placed in each leaflet cage and allowed to feed for 6-18 h. After feeding, the insects and leaf cages were removed and gas exchange properties were determined. Both adults and larvae reduced photosynthetic rates of the remaining tissue of the injured leaflet on both soybean and dry bean. A significant linear relationship between photosynthetic rate and percentage injury was observed for both adult and larval injury. Injury reduced photosynthetic rates in an 6 soybean and dry bean cultivars used in the experiments. There was no recovery of photosynthetic rates after injury of an individual leaflet. Stomatal conductance rates were not consistently different between injured and uninjured leaflets. Intercellular CO 2 concentrations were similar or higher in injured leaflets. Consequently, reductions in photosynthesis do not seem to be attributable to stomatal limitations. Quantum efficiency was not affected by injury, indicating that light-harvesting structures were not peJ1urbed. Therefore, our results suggest that the limitations to photosynthesis are attributable to the utilization of CO2 or the supply or utilization of phosphate. Our findings suggest that the limitation is associated with RuBPcase, RuBP regeneration, or phosphate utilization.

The toxicological impact of chemical pesticides on fungal entomopathogens and their use in tank-mixing can be directly measured through in vitro compatibility tests. This study reports the in vitro toxicity of eight insecticides, four fungicides and five herbicides in the conidial germination, vegetative growth and conidiation of Metarhizium anisopliae (strain CG 168). A conidial suspension containing the pesticide at recommended field dosage was subjected to constant agitation in a rotary shaker for 3h to simulate a tank mixing. Then, aliquots of each suspension were used to determine conidial germination, vegetative growth and conidiation on potato dextrose agar (PDA). The fungicides difenoconazole (69 mL ha -1 ), propiconazole (75 mL ha -1 ), trifloxystrobin (313 g ha -1 ) and azoxystrobin (56 mL ha -1 ) were the most harmful products to all biological stages of M. anisopliae and they should not be applied together with this fungus in tank mixing. The insecticides exhibited the least degree of toxicity to this fungal pathogen, whereas the herbicides had the greatest impact on mycelial growth. The agrochemicals compatible with M. anisopliae were the insecticides methyl parathion (240 mL ha -1 ), thiamethoxam (31 g ha -1 ), and lambda-cyhalothrin (6.3 mL ha -1 ) and the herbicides glyphosate (1560 mL ha -1 ), bentazon (720 mL ha -1 ), and imazapic+ imazapyr (84 g ha -1 ). The compatible pesticides could be simultaneously used with this bio-control agent for integrated pest management in rice production systems.

Tibraca limbativentris (rice stem bug) is an insect highly injurious to the rice crop in Brazil. The aim of this research was to define the spatial distribution of the T. limbativentris and improve the sampling process by means of geostatistical application techniques and construction of prediction maps in a flooded rice field located in the "Planalto da Campanha" Region, Rio Grande do Sul (RS), Brazil. The experiments were conducted in rice crop in the municipality of Itaqui - RS, in the crop years of 2009/10, 2010/11 and 2011/12, counting fortnightly the number of nymphs and adults in a georeferenced grid with points spaced at 50m in the first year and in 10m in the another years. It was performed a geostatistical analysis by means adjusting semivariogram and interpolation of numeric data by kriging to verify the spatial dependence and the subsequent mapping population. The results obtained indicated that the rice stem bug, T. limbativentris, has a strong spatial dependence. The prediction maps allow estimating population density of the pest and visualization of the spatial distribution in flooded rice fields, enabling the improvement of the traditional method of sampling for rice stem bug

Natural Egg Parasitism of Tibraca limbativentris Stal (Hemiptera: Pentatomidae)

Bioassays using an olfactometer showed that Oebalus poecilus males produce the sexual pheromone, and the chemical analysis demonstrated that this compound is zingiberenol. Two groups of isomers, each containing four diastereoisomers, (1RS,4RS,1'S)- and (1RS,4RS,1'R)-zingiberenol, were prepared. These diastereoisomers were not separated on a chiral GC column. Therefore, to determine the absolute configuration of the carbon 1, 4, and 1' of zingiberenol produced by males, the following strategies were conducted. The extract containing males volatiles was submitted to dehydration microchemistry to produce zingiberene, in which the isomers are separated by chiral GC analysis, and by comparison with the natural zingiberene from ginger oil, the absolute stereochemistry of the carbons 4 and 1' was determined to be R and S, respectively, and the carbon 1 was determined as R from the (13)C NMR spectra of quercivorol. Finally, the bioassays showed that O. poecilus females responded to racemic mixture and to (1RS,4RS,1'S)-zingiberenol.

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