Amarildo Pasini

Earthworm ecotoxicological assessments of pesticides used to treat seeds under tropical conditions

Ecotoxicological laboratory tests (lower-tier tests) are fundamental tools for assessing the toxicity of pesticides to soil organisms. In this study, using these tests under tropical conditions, we quantified the impact of the insecticides imidacloprid, fipronil, and thiametoxam, and the fungicides captan and carboxin+thiram, all of which are used in the chemical treatment of crop seeds, on the survival, reproduction, and behavior of Eisenia andrei (Oligochaeta). With the exception of imidacloprid, none of the pesticides tested caused mortality in E. andrei in artificial soils. The LC(50) of imidacloprid was estimated as 25.53 mg active ingredient kg(-1) of dry soil. Earthworm reproduction rates were reduced by imidacloprid (EC(50)=4.07 mgkg(-1)), fipronil (EC(20)=23.16 mgkg(-1)), carboxin+thiram (EC(50)=56.38 mgkg(-1)), captan (EC(50)=334.84 mgkg(-1)), and thiametoxam (EC(50)=791.99 mgkg(-1)). Avoidance behavior was observed in the presence of imidacloprid (AC(50)=0.11 mgkg(-1)), captan (AC(50)=33.54 mgkg(-1)), carboxin+thiram (AC(50)=60.32 mgkg(-1)), and thiametoxam (AC(50)=>20 mgkg(-1)). Earthworms showed a preference for soils with the insecticide fipronil. Imidacloprid was the most toxic of the substances tested for E. andrei. The avoidance test was the most sensitive test for most pesticides studied, but results varied between pesticides. These results offer new insights on the toxicity of pesticides used to treat seeds in tropical regions. However, they should be complemented with higher-tier tests in order to reduce the uncertainties in risk assessment.

No-tillage greatly increases earthworm populations in Paraná state, Brazil

Summary No-tillage (NT) agroecosystems now occupy >18 million ha in Brazil, of which 5 million are in the state of Parana, where NT began in the early 1970’s. The first NT farmers created an association to promote their practices, the ‘Clube da Minhoca’ (Earthworm Club), thus named because of the observed increase in earthworm numbers in their fields after adopting NT. However, little data were available on the topic until 1996, when more intensive studies began near Londrina, in N Parana. Earthworms were sampled by hand-sorting soil monoliths (25 × 25 cm square, 30‐40 cm depth) at 8 sites, comprising various natural and agricultural land-use and management systems. Data from the literature were collected from a further 6 sites for comparative purposes. The results for N Parana confirm the presence of higher earthworm populations under NT (46‐116 indiv., 0.49-1.06 g f.wt. m-2; mean values in dry-wet seasons, respectively), minimum tillage (42‐179 indiv., 0.68‐1.05 g f.wt. m -2 ), pastures (48‐182 indiv. m -2 ) and native forests (16‐42 indiv., 1.56‐0.83 g f.wt. m -2 ) than under conventional tillage (13‐22 indiv. and 0.13‐0.02 g f.wt. m-2). Soil disturbance thus had a negative impact on earthworm populations, and significant positive relationships were observed between earthworm abundance and age of NT systems, as well as with soil % C. In the Londrina area, some species present in the primary forests were absent in NT, where most earthworms were small-sized endogeic or epi-endogeic species. These results contrasted greatly with those from the cooler region in E Parana, where the exotic epi-endogeic Amynthas spp. dominated, reaching high densities (up to >100 indiv. m-2) and biomass (up to >30 g f.wt. m-2), especially under NT. Given the high abundance of worms under NT, further work should focus on estimating their potential contributions to soil processes, fertility and plant production in these systems.

Seed dressing pesticides on springtails in two ecotoxicological laboratory tests

Terrestrial ecotoxicological tests are powerful tools for assessing the ecological risks that pesticides pose to soil invertebrates, but they are rarely used to evaluate seed dressing pesticides. This study investigated the effects of seed dressing pesticides on survival and reproduction of Folsomia candida (Collembola), using standardized ecotoxicological tests (after ISO guidelines with few adaptations for tropical conditions). Commercial formulations of five seed dressing pesticides were tested individually in Tropical Artificial Soil (TAS): the insecticides imidacloprid, fipronil, thiametoxam, and the fungicides captan and carboxin+thiram. Thiametoxam, captan, and carboxin+thiram were only lethal to F. candida at the highest concentration tested (1000mg of active ingredient kg(-1) of dry soil). Imidacloprid and fipronil were lethal at lower concentrations (100 and 10mg a.i. kg(-1) soil d.w, respectively), however, these concentrations were much higher than those predicted (PEC) for soil. Imidacloprid and fipronil were the most toxic pesticides in both tests, reducing significantly collembolan reproduction (EC20=0.02 and 0.12mga.i.kg(-1) soil d.w, respectively). Further studies under more realistic conditions are needed, since imidacloprid and fipronil reduced collembolan reproduction at concentrations below or close to their respective PECs.

Predação de pupas de Alabama argillacea (Hübner) (Lepidoptera: Noctuidae) por larvas e adultos de Calosoma granulatum Perty (Coleoptera: Carabidae) em laboratório

The predation capacity of larvae and adults of Calosoma granulatum Perty on Alabama argillacea (Hubner) pupae was studied under laboratory conditions. In the first experiment, each larva of C. granulatum (n=18) was provided with five pupae of A. argillacea per day; in the second experiment, five pupae per day were given to each C. granulatum adult (n= five males and five females). Their predation rate was 1.8 pupae per day. The highest level of predation occurred from the end of the second instar to the beginning of the third instar. Their predation rate for adults was 1.5 and 1.7 larvae per day, for males and females, respectively. There was no significant difference between male and female predation capacity in all evaluations. These results indicate that C. granulatum larvae and adults may prey on relatively high numbers of A. argillacea pupae, and therefore, the preservation of this predator on cultivated areas is essential to reduce the number of insecticide sprays and, consequently, the cost of production per hectare.

No impact of Bt soybean that express Cry1Ac protein on biological traits of Euschistus heros (Hemiptera, Pentatomidae) and its egg parasitoid Telenomus podisi (Hymenoptera, Platygastridae)

No impact of Bt soybean that express Cry1Ac protein on biological traits of Euschistus heros (Hemiptera, Pentatomidae) and its egg parasitoid Telenomus podisi (Hymenoptera, Platygastridae). Biological traits of the stink bug Euschistus heros and its main biological control agent Telenomus podisi were evaluated under controlled environmental conditions (25 ± 2oC; 60 ± 10% RH; and 14/10 h photoperiod) by placing first instar nymphs into Petri dishes with pods originating from two soybean isolines (Bt-soybean MON 87701 × MON 89788, which expresses the Cry1Ac protein, and its near non-Bt isoline A5547) where they remained until the adult stage. Due to gregarious behavior exhibited by first instar nymphs, they were individualized only when at the second instar. Adults were separated by sex and weighed, and pronotum width of each individual was subsequently measured. They were placed into plastic boxes containing soybean grains of the same soybean isoline as food source. Egg viability and female fecundity were assessed in adult individuals. Adult females of T. podisi (up to 24h old) were placed with eggs of E. heros from mothers reared on both soybean isolines. Nymphal development time, insect weight, pronotum width, sex ratio, female fecundity, and egg viability (% emergence) of Euschistus heros did not differ between treatments. Eggto-adult development time, female longevity, sex ratio, and percentage of parasitized eggs were not impacted by the Bt-soybean (expressing Cry1Ac protein). Results indicate that the Bt-soybean, MON 87701 × MON 89788, has no direct significant impact on the two studied species.

Dieta artificial para criação de Doru luteipes (Scudder) (Dermaptera: Forficulidae), predador da lagarta-do-cartucho do milho, Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae)

A new technique involving an artificial diet and an artificial substrate for oviposition for the rearing of the predator Doru luteipes (Scudder) is suggested. Both adults and nymphs were maintained in petri dishes containing a transparent piece of soda straw filled with moistened cotton and the corresponding food for the biossays. The following treatments were tested: eggs of Spodoptera frugiperda (J.E. Smith), Diatraea saccharalis Fabricius (Lepidoptera: Pyralidae) and Anagasta kuehniella Zeller (Lepidoptera: Pyralidae); insect pupae meal (FPI); Apis mellifera L. (Hymenoptera: Apidae) commercial pollen (PC); FPI + PC, and FPI + cattail pollen [Typha angustifolia L. (Thyphaceae)]. Each treatment had 50 replicates, and food was offered in excess. Treatments consisting of insect pupae meal (FPI), FPI + commercial pollen (PC), and FPI + cattail pollen resulted in nymphal development of 32, 29, and 29 days, with 83, 90 and 100% survival, respectively, and were superior to the PC treatment, with values of 37 days and 67% survival observed for insects reared on commercial pollen. Treatments that included insect pupae flour, either alone or mixed with pollens, were similar to control (S. frugiperda eggs). We conclude that the artificial diets tested and rearing technique are suitable for the artificial rearing of D. luteipes in laboratory conditions.

Biologia e preferência da lagarta do girassol, Chlosyne lacinia saundersii (Lepidoptera: Nymphalidae) na planta daninha losna branca, Parthenium hysterophorus (Asteraceae)

O objetivo deste trabalho foi estudar a biologia de Chlosyne lacinia saundersii Doubleday, sobre losna branca, Parthenium hysterophorus (Asteraceae), bem como avaliar sua preferencia em relacao ao girassol e a planta daninha. Os ovos foram coletados no campo sobre plantas de P. hysterophorus. A criacao das lagartas foi realizada sob condicoes controladas de temperatura (25 ± 2oC) e fotoperiodo (12 h L:12h E). A duracao media da fase de ovo foi de sete dias; da fase larval de 18,9 dias, com 75% de sobrevivencia e da fase pupal de 6,1 dias, com 65% de sobrevivencia. C. lacinia saundersii preferiu alimentar-se de girassol, comparativamente a losna branca. A planta daninha P. hysterophorus constitui hospedeiro alternativo para a lagarta do girassol, permitindo que a mesma complete o ciclo biologico naquela planta.

Earthworm communities in organic and conventional coffee cultivation

The objective of this work was to evaluate the effect of organic and conventional coffee crops on biomass, population density and diversity of earthworms, in Lerroville, district of Londrina County, Parana state, Brazil. Earthworm communities were sampled in three areas with organic coffee cultivation (CO1, CO2 and CO3), two with conventional coffee (CC1 and CC2), and a native forest fragment (MT). The soil of the areas CO1, CC1, and MT was classifi ed as Nitossolo Vermelho (Rhodic Kandiudox), while CO2, CO3, and CC2 were on Latossolo Vermelho (Rhodic Hapludox). Eight samples were taken in each area on two occasions, winter and summer, using the Tropical Soil Biology and Fertility (TSBF) method in the 0-20 cm soil layer. The earthworms were handsorted and preserved in 4% formaldehyde, and were later weighed, counted and identifi ed. The highest earthworm biomass, both in winter and summer, occurred in the CO3 area. For population density, the higher numbers of individuals were found in CO1 and CO3. The highest number of species was identifi ed in the organic cultivation. The adoption of organic practices in coffee cultivation favored the diversity, density and biomass of earthworm communities.

Biologia e preferência alimentar de Ascia monuste orseis (Latreille) (Lepidoptera: Pieridae) na planta invasora Raphanus raphanistrum L.

Foi estudada a biologia e preferencia alimentar do curuquere-da-couve, Ascia monuste orseis (Latreille) na planta invasora R. raphanistrum L. Ovos de A. monuste orseis foram coletados nas plantas de couve manteiga da fazenda da Universidade Estadual de Londrina (UEL), PR. As lagartas foram individualizadas, recebendo folhas de nabica diariamente, observando-se os instares e registrando-se a mortalidade. A duracao media da fase larval foi de 12,9 (± 0,08) dias, com mortalidade de 42,0%; a duracao media da fase pupal foi 6,7 (±0,13) dias e a mortalidade de 38,4%. O curuquere preferiu alimentar-se de nabica, comparativamente com a couve manteiga, Brassica oleracea var. acephala.

Association of the soil bug Atarsocoris sp. (Hemiptera: Cydnidae) with the weed Senecio brasiliensis Less

Os percevejos da familia Cydnidae, entre eles Atarsocoris sp., sao insetos-praga com ocorrencia em varias culturas, acarretando perdas significativas em areas com grande infestacao do inseto; sendo tambem muito comuns associados a plantas daninhas. A ocorrencia de Atarsocoris sp. foi observada em areas de pastagens degradadas, nas raizes da planta maria-mole (Senecio brasiliensis Less). Mediante essa observacao, foi levantada a hipotese da correlacao entre a planta invasora e o inseto. O experimento foi realizado em solos de arenito (Latossolo Vermelho), em areas de pastagem com a presenca da maria-mole e sem a planta, totalizando tres tratamentos e 10 repeticoes. Houve correlacao positiva entre a planta invasora maria-mole e o percevejo (Atarsocoris sp.), sendo esta considerada uma hospedeira alternativa do inseto nas condicoes encontradas naquela area de estudo, ou seja, pastagens degradadas e solo arenoso. A correlacao detectada permite sugerir a inclusao da maria-mole como bioindicadora do referido inseto nestas areas.