Spatial Distribution and Coexisting Patterns of Adults and Nymphs of Tibraca limbativentris (Hemiptera: Pentatomidae) in Paddy Rice Fields

Illustrated guide to Pentatominae (Hemiptera: Pentatomidae) species associated with the four main grain crops in Rio Grande do Sul state, Brazil

Several stink bugs in the subfamily Pentatominae are crop pests or have the potential to damage plants of economic importance. In the Brazilian state of Rio Grande do Sul, where agriculture plays a major role in the economy, the knowledge about pest stink bugs is fragmented and, in some instances, outdated. This work provides a summary of Pentatominae species recorded in Rio Grande do Sul feeding on the four most important grain crops for the state, i.e. soybean, rice, maize, and wheat, plus canola, an emerging crop. This survey is enhanced with new records from scientific collections, a short diagnosis for each species, distribution maps, an identification key, and carefully illustrated to allow for species recognition in the field. With this work, we aim to reunite the scattered knowledge of the group in one single revision, and provide a useful tool for identifying the pest stink bugs of Rio Grande do Sul.

Predicting Rice Stem Stink Bug Population Dynamics Based on GAMLSS Models

The rice stem stink bug, Tibraca limbativentris Stål (Hemiptera: Pentatomidae), is one of the most harmful insects for Brazilian rice fields. Aiming to define the most appropriate time and place for pest management measures in commercial paddy fields, we adjusted regression models (Poisson, Zero Inflated Poisson, reparametrized Zero Inflated Poisson, Negative Binomial and Zero Inflated Negative Binomial) for modeling the population variation of T. limbativentris along the phenological cycle of the flooded rice cultivation. We hypothesize that the rice stem stink bug population's size is influenced by the rice cycle (time) and geographical positions within the crop. It was possible to predict the occurrence of the rice stem stink bug in the commercial flooded rice crop. The population of the rice stem stink bug increased significantly with the time or phenological evolution of rice. Our results indicated that the start of T. limbativentris monitoring should occur up to 45 d After Plant Emergence (DAE), from the regions along the edges of the rice paddies, which are the points of entry and higher concentration of the insect. In addition, 45 and 60 DAE were considered the crucial times for T. limbativentris control decision making in flooded rice paddies.

Resistance of rice genotypes to Tibraca limbativentris (Hemiptera: Pentatomidae)

The Tibraca limbativentris is a pest that causes rice crop damage and may lead to grain yield reductions of up to 90%. The most commonly used tactic for T. limbativentris control is chemical, which causes adverse effects on the environment. This study was conducted to identify sources of antixenosis and antibiosis resistance to T. limbativentris mediated by the hardness and diameter of the stem of the rice plant. Antibiosis and antixenosis tests were carried out with 22 rice genotypes of Brazilian and Asian origin. The Canela de Ferro, BRS Esmeralda, and Desconhecido Branco genotypes had the lowest proportions of stems showing symptoms of the damage caused by T. limbativentris. Canela de Ferro, Primavera, and IR 22 genotypes had the lowest nymphs survivorship and the genotypes Marabá Branco, Marabá, Skirivimankoti, Pepita, BR IRGA 409, Curinga, IR 40, Bonança, Desconhecido Branco, Bico Ganga, Primavera, and BRS Esmeralda were the least attractive to the insects. The genotypes BRS Esmeralda, Primavera, Desconhecido Branco, and Canela de Ferro were resistant to the rice stalk stink bug by antibiosis and/or antixenosis. These genotypes can be used directly by rice farmers for T. limbativentris management. Molecular biology studies should be conducted to identify and characterize resistance genes in these genotypes so that they can be used in breeding programs.

Biology, Thermal Requirements, and Estimation of the Number of Generations of Hypothenemus hampei (Ferrari, 1867) (Coleoptera: Curculionidae) in the State of São Paulo, Brazil

Coffee culture, one of the main agricultural activities in Brazil, has undergone recent negative impacts due to unfavorable climate conditions, with a subnormal rainy period and increased temperatures during the second half of 2015. The coffee berry borer Hypothenemus hampei (Ferrari, 1867) (Coleoptera: Curculionidae) is one of the main insect pests of coffee crops worldwide. The present research aimed to determine the climate zones for coffee berry borer in the state of São Paulo, based on its thermal requirements. The results showed that the mean biological development time of H. hampei was affected by temperature, completing its life cycle more rapidly in increased temperatures until the 30°C threshold temperature, and more slowly above this temperature. Development time (egg-adult) was inversely related to temperature in the range between 18 and 32°C. The temperature threshold (Tt) was 13.9°C and the thermal constant (K) was 299 degree-days. These laboratory estimates of thermal requirements and the Geographic Information System (GIS) were used to generate insect life span distribution maps for São Paulo. In this state, the coffee berry borer can produce 5.09-10.53 generations annually. Higher pest incidences should coincide with both temperature increases and the availability of coffee fruit for infestation. The data obtained can be used to estimate the monthly and yearly number of generations of this pest, for use in integrated pest management programs.

Economic Injury Levels and Economic Thresholds for Tibraca limbativentris (Hemiptera: Pentatomidae) on Paddy Rice Based on Insect-Days

The rice stalk stink bug Tibraca limbativentris Stal, 1860 (Hemiptera: Pentatomidae) is an important pest of paddy rice (Oryza sativa L.) in South America. Current records of economic injury levels (EILs) and economic thresholds (ETs) for this insect are scarce. In this study, we determined EILs and ETs through cumulative insect-days of T. limbativentris adults in two phenological stages of paddy rice. Five field trials were established for the 2015/16 and 2016/17 crop season. To evaluate the relationship between insect-day and yield, rice plants were infested at V4 and R2 with adult male-female pairs of T. limbativentris. Mixed linear models were fitted utilizing the year and block as random factors to estimate the damage to plant, irrespective of the interference of environmental factors. The yield loss per insect-day was then used to calculate EILs using current market values and control costs. Rice grain yields were reduced by 5.91 kg/ha for each insect-day/m2 when infested during V4 stage, with EILs ranging from 3.88 to 11.61 insect-days/m2, while infestation during R2 stage resulted in a yield reduction of 3.16 kg/ha, with EILs ranging from 8.05 to 21.72 insect-days/m2. The results indicate that yield losses of paddy rice due to T. limbativentris infestation vary according to plant phenological stages and management should consider control cost and market value of rice. These EILs and ETs based on insect-days may be an efficient strategy for decision-making in the management of T. limbativentris on paddy rice.