Edson Hirose

Compatibility of entomopathogenic fungi with neonicotinoid insecticides

The in vitro fungitoxic effect of the neonicotinoid insecticides acetamiprid (Saurus 200 SP), imidacloprid (Confidor 700 WDGr) and thiamethoxam (Actara 250 WG) in three concentrations (AR= average field recommendation; 0.7 AR and 1.3 AR) to the entomopathogenic fungi Beauveria bassiana, Metarhizium anisopliae and Paecilomyces sp. was studied. The effect of the insecticides on conidia germination, vegetative growth and conidiogenesis was compared. The insecticides had no effect on conidia germination, except under the highest concentration (1.3 AR) of acetamiprid, in which significant inhibition of M. anisopliae occurred. Vegetative growth of B. bassiana and M. anisopliae was significantly inhibited only by the three concentrations of acetamiprid treatment. Thiamethoxam treatment, in the AR and 1.3 AR concentrations, was significantly lower for B. bassiana vegetative growth. Paecilomyces sp. vegetative growth was higher than the control in the following treatments: 0.7 AR and AR of acetamiprid; all concentrations of imidacloprid; and in the two smallest concentrations, 0.7 AR and AR, of thiamethoxam. Conidia production was significantly smaller for Paecilomyces sp. and M. anisopliae, in the highest concentration (1.3 AR) of acetamiprid treatment and, for Paecilomyces sp., in the highest concentration (1.3 AR) of imidacloprid. Thiamethoxam significantly inhibited M. anisopliae conidia production, only in the smallest concentration (0.7 AR).Significant increase in the conidia production of Paecilomyces sp. fungus was observed in the following treatments: two concentrations, 0.7 AR and AR of acetamiprid; and in the two highest concentrations, AR and 1.3 AR, of thiamethoxam treatments. The use of insecticides, in the recommended formulations and other concentrations tested, in most cases, had no negative effect on conidia germination, conidia production and vegetative growth of B. bassiana, M. anisopliae and Paecilomyces sp. Consequently, these products, in the formulations and concentrations tested, may be used in IPM programs in which the entomopathogens are important pest regulators.

Bacteria in the Gut of Southern Green Stink Bug (Heteroptera: Pentatomidae)

Abstract Laboratory studies with the southern green stink bug, Nezara viridula (L.), indicated the presence of bacteria Klebsiella pneumoniae (Schroeter) and Enterococcus faecalis (Andrewes & Horder) in the crop/stomach (ventriculus 1–3; V1–V3), and possibly Pantoea sp. in the gastric caeca (ventriculus 4; V4). Culturable bacteria were most abundant in V1–V3, and their abundance was drastically reduced in V4. The variable pH in the gut did not affect the presence of bacteria. Elimination of bacteria from the gut, by using the antibiotic kanamicin, did not affect nymphal developmental time or cause mortality, but it did cause reduced weight at adult emergence.

Seasonal body weight, lipid content, and impact of starvation and water stress on adult survivorship and longevity of Nezara viridula and Euschistus heros

Fresh and dry body weights (FW, DW) were greater for adult southern green stink bug, Nezara viridula (L.) than for the brown stink bug, Euschistus heros F. throughout the year in southern Brazil. Females N. viridula significantly increased FW and DW in late summer‐early autumn, and during mid‐spring; female E. heros did not show the same rates of increase in FW and DW. Female N. viridula were heavier than males, particularly during summer; however, female and male E. heros were generally similar in weight. E. heros contained significantly greater amounts of lipid than N. viridula, during mid‐autumn to early‐spring (April‐September). Survivorship (%) and total longevity of E. heros adults provided water only was greater (34.6–24.6 days, for females and males) than that for N. viridula (14.8–13.0 days); without water and food, longevity was drastically reduced (<7 days) for both species.

Seleção de isolados de Beauveria bassiana para o controle biológico da broca-do-café, Hypothenemus hampei (Ferrari) (Coleoptera: Scolytidae)

Hypothenemus hampei (Ferrari) (Coffee Berry Borer) is one of the most important coffee pests. Its control is carried out mainly using synthetic chemical products, which contaminate the environment, food and farmers. The entomopathogenic fungus Beauveria bassiana is a natural enemy of coffee berry borer and presents potential for biological control. With the objective to select strains of B. bassiana for the management of H. hampei, the virulence of 61 strains, from diverse hosts and geographic regions, were tested. The selection was carried out in two phases: in the first phase 11 strains, with confirmed mortality above 60%, were selected. In the second phase, for the 11 preselected strains, we determined: LC50, sporulation rate (confirmed mortality/total mortality) and conidia production on H. hampei cadavers. The CG425 strain presented the greater total and confirmed mortality, highest sporulation rate and CL50 = 2.5 x 106 conidia/ml and CB102 strain, presented highest conidia production on insects, 11.6 x 106 conidia/insect. These isolates present height potential to be used in biological control programs of coffee berry borer with B. bassiana.

Effect of relative humidity on emergence and on dispersal and regrouping of first instar Nezara viridula (L.) (Hemiptera: Pentatomidae)

Laboratory studies with 1st instar of southern green stink bug, Nezara viridula (L.) indicated that relative humidity (RH) greatly affected nymph emergence and survivorship up to the 2nd instar, reaching the maximum value (approximately 90%) with RH of > 80%. At 60% RH, 60% of the nymphs emerged and survived, while with 0% RH only approximately 15% of eggs hatched, and most nymphs died. Emerged nymphs from egg masses placed in plastic boxes with a gradient of humidity remained on egg shells for ca. one day. After this period, they dispersed and regrouped on top of shells 6.8 +/- 0.67 times, until they abandoned the shells toward the source of humidity, avoiding the water-saturated areas. Duration taken for each rearrangement (dispersal + regroup) increased with time, with a range of approximately 26 min to 44 min. The mean duration of the grouping behavior on egg shells after each rearrangement decreased from approximately 102 min (1st) to 24 min (6th and last grouping). The rearrangement behavior of 1st instars on top of egg shells apparently compensates for the water loss of nymphs.

Genetic differentiation among Brazilian populations of Euschistus heros (Fabricius) (Heteroptera: Pentatomidae) based on RAPD analysis

The Neotropical Brown Stink Bug (NBSB), Euschistus heros (Fabricius), has a wide distribution in Brazilian soybean fields, being more important in the central region of the country. The species is the main target of insecticide applications for stink bug pest control. We determined the variability among and within populations of the NBSB by random amplification of polymorphic DNA (RAPD) analysis. Samples of NBSB were collected in soybean fields from Ubirata (PR), Londrina (PR), Centenario do Sul (PR), Cândido Mota (SP), Ponta Pora (MS) and Sapezal (MT). Genomic DNA was extracted from the head to minimize DNA contamination by endoparasites. DNA was amplified with 10 mer primers. Fifteen primers produced 246 bands. The genetic similarity matrix was obtained, based on RAPD allele frequencies, using Neis 1972 genetic distance. NSBS collected from the same geographical region clustered together. The populations from Londrina and Centenario do Sul were genetically closer than the others and stink bugs collected in Cândido Mota were closer to Ponta Pora population. The Sapezal geographical population was the most divergent from the others. Females and males clustered separately inside each geographical population, implying that RAPD permits gender discrimination. We did not observe individuals from one region clustering together with stink bugs from another region. The number of polymorphic loci from the different populations ranged between 40.6% and 52.1%. The gene flow indexes (overall Nm = 0.8307) were lower than that observed for Anticarsia gemmatalis Hubner and Helicoverpa armigera (Hubner) suggesting that in stink bug populations gene flow is lower than in the noctuid moths.

Potential use of antibiotic to improve performance of laboratory-reared Nezara viridula (L.) (Heteroptera: Pentatomidae)

The antibiotic streptomycin added to the drinking water at a concentration of 125 mg/ l during nymphal development of Nezara viridula (L.) (Heteroptera: Pentatomidae)accelerated the development in ca. 2 days, increased survivorship, and doubled adult longevity; nymph survivorship and adult body weight were not affected when compared to control insects. Streptomycin has potential in rearing N. viridula, especially in improving quality of field-collected adults, by mitigating the introduction of pathogenic bacteria, and improving the quality of the population.

Competition between the phytophagous stink bugs Euschistus heros and Piezodorus guildinii in soybeans

BACKGROUND The abundance and contribution of the neotropical brown stink bug, Euschistus heros (F.), and the redbanded stink bug, Piezodorus guildinii (West.), to the composition of insect pests of soybean, Glycine max (L.), fields have changed both spatially and temporally in neotropical soybean production areas. Therefore, we assessed the competitiveness of each species in direct competition experiments following an additive series. We performed mixed (adult) insect infestations in soybean plants and evaluated the fitness of each species and the soybean yield. RESULTS While the competitive ability of E. heros was significantly compromised by increments in conspecifics and heterospecifics (i.e. P. guildinii), the competitive ability of P. guildinii was compromised by the presence of heterospecifics (i.e. E. heros). The reproductive output of P. guildinii remained unaffected by increments in E. heros or of P. guildinii. Intriguingly, despite the fact that P. guildinii apparently lost the competition with E. heros, almost no pod production was observed in any plant colonised by the former. CONCLUSIONS The higher abundance of E. heros in neotropical soybean fields seems to result from higher competitive ability than its heterospecific competitor P. guildinii, which may prevent the higher losses caused by P. guildinii.

Biology and Descriptions of Nymphal and Adult Jadera choprai (Hemiptera: Rhopalidae)

Abstract The biology of nymphs and adults of the Neotropical scentless bug Jadera choprai Göllner-Scheiding feeding on mature seeds of the balloon vine, Cardiospermum halicacabum (L.) (Sapindaceae), was studied in the laboratory. Most nymphs (>75%) successfully reached adulthood when feeding on this food. Nymphs reared individually had lower mortality (14.0%) and shorter developmental times (35.7 d) than did bugs reared in groups (23.3% and 39.9 d). All adult females oviposited when fed on seeds of balloon vine. Mean adult longevity was 86.0 d for males and 47.7 for females. Mean fecundity was ≈147 eggs per female, and ≈85% of the eggs hatched. Fresh body weight of females increased significantly during the first week of adult life; males, however, lost weight significantly during this period. Females lost weight during their second week posteclosion, but they regained the weight subsequently. However, males did not. Nymphs and adults (macropterous and brachypterous forms) of J. choprai are described and illustrated, as are their setal patterns.

Seed-carrying and feeding behavior of Jadera choprai Göllner-Scheiding (Heteroptera: Rhopalidae)

During February-March 2001, the seed-carrying and feeeding behavior on Cardiospermum halicacabum (L.) (Sapindaceae) by Jadera choprai Gollner-Scheiding was studied. Field observations indicated that the bugs feed on seeds found on the ground. Laboratory studies indicated that J. choprai may carry seeds 200 cm from where they were found. Several individuals were observed feeding on one seed, with the occurrence of cannibalism. Apparently, this is the first record on the association of J. choprai with C. halicacabum, and on seed-carrying by this rhopalid.