First Record of Teratopactus nodicollis (Coleoptera: Curculionidae) in Dry Bean (Phaseolus vulgaris)

Observations on the bioecology and damage of Teratopactus nodicollis Boheman on Phaseolus vulgaris were carried out on field samples by assessing the number of larvae and root damage in 40?ha of a dry bean field from the Federal District, Brazil (16°4??28.41???W; 47°30??21.13???S). Larvae caused the greatest damage at the stage of germination, emergence, and primary leaves, producing 50?% stand reduction. Most larvae pupated in August and September, and adult emergence occurred in middle October. Some larvae were infected with the fungus Metarhizium spp., a biological agent that would be naturally controlling this insect.     

Natural egg parasitism of Tibraca limbativentris Stal (Hemiptera: Pentatomidae) in rice crop in the State of Maranhão, Brazil

The rice stem bug, Tibraca limbativentris Stal, is an important pest of rice in Brazil. This work evaluated the occurrence of parasitoids in eggs of T.limbativentris egg parasitism in rice crops in the Maranh?o State. The eggs collected exhibited an average parasitism of 32%. The parasitoids collected were Telenomus podisi (Ashmead), Trissolcus urichi (Crawford) (Hymenoptera: Scelionidae) and Oencyrtus submetallicus (Howard) (Hymenoptera: Encyrtidae).     

Mapping of spatiotemporal distribution of Tibraca limbativentris Stal (Hem.: Pentatomidae) in flooded rice crop in Southern Brazil

The rice stem bug, Tibraca limbativentris Stal (Hem.: Pentatomidae), is one of the main insect pests in Brazilian rice crops. Knowledge of its spatiotemporal distribution can support the development of an effective sampling system and improve IPM strategies. This study aimed to map the spatiotemporal distribution of rice stem bug in flooded rice crop in Southern Brazil. Flooded rice crop was scouted for two seasons to estimate insect densities. Four occurrence categories were observed: no insect, only adults, only nymphs, and both phases. The relationship between phenological stages and insect categories was established. Interpolation (mapping) of occurrence categories of T. limbativentris was performed by multiquadric equations. In two seasons during the rice cycle, the results indicate that rice stem bug “adults” were the most abundant category until the mid-vegetative phase of the rice; “nymphs” were the most abundant from the end of vegetative phase; “adults + nymphs” occurred from the beginning of reproductive phase; there were no rice stem bugs in more than 66% of the area, as they were most concentrated near the edge of the crop. The information presented here provides further knowledge about T. limbativentris spatiotemporal dynamics that can be applied to improve IPM strategies, such as developing sampling plans and localized control measures at the edge of rice fields.     

Life Cycle of Glyphepomis spinosa Campos & Grazia (Hemiptera: Pentatomidae): a New Pest of Rice in Brazil

Nymph and adult biology of Glyphepomis spinosa Campos & Grazia (Hemiptera: Pentatomidae) was studied on rice plants under laboratory and greenhouse conditions. The full life cycle of G. spinosa lasted 50.1?day. Nymph development ranged from 2.7?days for the first instar up to 11.9?days for the fifth instar. The egg stage showed the highest per capita rate of mortality (0.16). Nearly 13% of all eggs were laid on the same day. The sex ratio was 0.5. The average hatching rate was 58.0%. Pre-oviposition, oviposition, and post-oviposition periods took 12.9, 34.4, and 6.2?days, respectively.     

Economic injury levels and sequential sampling plans for Mexican bean beetle (Coleoptera: Coccinellidae) on dry beans

Field studies were conducted during the growing seasons of 1995 and 1996, in Scotts-bluff, Nebraska, to determine yield-loss relationships for Mexican bean beetle (Epilachna varivestis Mulsant) on dry bean (Phaseolus vulgaris L.). Results of those experiments were combined with data from other studies previously conducted to develop economic injury levels (EILs), economic thresholds (ETs), and a sequential sampling program for Mexican bean beetle. Yield loss was regressed against larvae/row-m, and the slope of the linear regression (113 kg/ha per larvae/row-m) was used as the DI (yield loss/insect density) variable in EIL calculations. The EILs calculated in larvae/row-m were converted to egg masses/row-m and adjusted to reflect average survivorship to the adult stage. An example EIL for esfenvalerate at 0.509 (formulation) liter/ha (0.0453 gal/a) and crop value of 0.44 dollars/kg (20 dollars/100 lbs) was 17.78 larvae/row-m. The corresponding ET is 1.04 egg masses/row-m, which reflects an average of 54.6 eggs/egg mass and 33% survival rate from egg to injurious stages. Sequential sampling plans were calculated based on a negative binomial distribution using parameter k estimated from previous research. Because sampling is based on egg masses, growers can make management decisions and take management actions before significant injury occurs. Also, ETs can be adjusted to include the occurrence of natural mortality in the egg and early instars. Analyses demonstrated that relatively minor variation in ETs has substantial impact on sequential sampling plans, including parameters such as average sample number. An interactive spreadsheet was developed that allows users to input economic and other data specific to their situation to calculate Mexican bean beetle EILs, ETs, and sequential sampling plans.     

Age Influence on Sexual Behavior of the Lesser Cornstalk Borer, <Emphasis Type="Italic">Elasmopalpus lignosellus</Emphasis> (Zeller) (Lepidoptera: Pyralidae)

The objective of this work was to evaluate the reproductive behavior and response of Elasmopalpus lignosellus (Zeller) males to calling females. Frequency of mating was recorded in couples during the first 7 days of the adult stage. Calling behavior of females was observed during the first 4 days of the adult stage and responses of males, in the same age intervals, to calling females were recorded in wind tunnel bioassays. The maximum number of matings occurred when the couple was between 24 and 48 h old. The scotophase period significantly influenced mating behavior, which peaked between 6 and 8 h of darkness and the mean mating duration was 93.9 ± 4.2 min. Calling females, when evaluated in a wind tunnel, attracted significantly more males than in bioassays with clean air (control). The number of individuals in calling behavior was significantly lower for females that were between 0 to 24 h old compared to the other females evaluated, but this did not influence male response. A lower proportion of males between 48 to 72 h old responded to calling females and these responses were delayed in comparison with males of other ages (0 to 24, 24 to 48, and 72 to 96 h old). These results indicate that the age of E. lignosellus males influences the response to conspecific calling females.     

Differential induction of volatiles in rice plants by two stink bug species influence behaviour of conspecifics and their natural enemy Telenomus podisi

Tritrophic interactions mediated by semiochemicals have been intensively studied from the viewpoint of ecological relationships with Nearctic tritrophic organisms. However, there are few studies involving interactions with different herbivores on the same host plant in Neotropical systems. The objective of the current study was to investigate the effects of herbivory by two species of stink bugs (Heteroptera: Pentatomidae) with the same feeding habit – Tibraca limbativentris Stål and Glyphepomis spinosa Campos & Grazia – on indirect and direct defence strategies of rice plants. The responses of each stink bug species (virgin and mated females) and of their main natural enemy, the egg parasitoid Telenomus podisi Ashmead (Hymenoptera: Platygastridae; mated females), to volatiles from undamaged and herbivore-damaged rice plants were evaluated using a Y-tube olfactometer. The results showed that rice plants responded differently to T. limbativentris or G. spinosa herbivory, enhancing the production of a different blend of volatile compounds, which reduced the attraction for conspecific stink bugs and elicited the foraging behaviour of T. podisi.