Crébio José Ávila

DANOS CAUSADOS POR LARVAS E ADULTOS DE DIABROTICA SPECIOSA (COLEOPTERA: CHRYSOMELIDAE) EM MILHO

A especie Diabrotica speciosa (Germar, 1824) e, tradicionalmente, na fase adulta, uma praga polifaga, embora apresente certa preferencia por folhas do feijoeiro e soja. Entretanto, nos ultimos anos, a fase de larva deste crisomelideo adquiriu o status de praga, a semelhanca de outras especies do mesmo genero nos EUA, causando consideraveis danos ao sistema radicular do milho. O objetivo da pesquisa foi avaliar os danos causados por diferentes niveis populacionais de larvas de D. speciosa as raizes de milho, e, pelos adultos as folhas de milho, soja, feijoeiro e arroz. Desde as menores densidades populacionais de larvas, houve reducao significativa no peso seco das raizes do milho, peso seco da parte aerea e na altura das plantas em relacao a testemunha. Constatou-se que o nivel de controle esta aquem de 40 larvas por planta. Os adultos tiveram significativa preferencia por folhas do feijoeiro e soja, sendo o milho e o arroz menos consumidos.

Desenvolvimento de Diabrotica speciosa (Germar) (Coleoptera: Chrysomelidae) em diferentes hospedeiros

SUMMARY The aim of this work was to determine the influence of the host plant, as food, on the larval and adult phases of D. speciosa. Larvae of this insect were reared on seedlings of bean, corn, soybean, as well as on potato tubers kept in wet vermiculite. The following biological parameters were evaluated: duration and viability of the larva-adult period and the weight of newly emerged insects (males and females). The fecundity of D. speciosa was also evaluated offering to the adults leaves of bean, soybean, corn and potato. The host plant offered as food on the larval phase influenced significantly the weight of the insects (males and females) as well as the duration and viability of the larva-adult period. The development time of the immature phases (larva + pupa) on potato (36.5 days) was longer than that on corn (25.1 days). The viability values (larva + pupa) were higher on potato (84.1%) and corn (75.9%) while on soybean and bean the viability was low (30.1% and 9.4%, respectively), characterizing these plants as inadequate hosts for the larval development of the insect. Adults of

Comparação de técnicas para criação de Diabrotica speciosa (Germar) (Coleoptera: Chrysomelidae) em dietas natural e artificial

Studies viewing the improvement of the rearing methodology of Diabrotica speciosa (Germar) (Coleoptera: Chrysomelidae) in laboratory were carried out. Larval development was compared in three rearing methods, two of which with natural diet using corn seedlings kept on vermiculite or on germination paper sheets and a third system using artificial diet. The following biological parameters were evaluated: duration and viability of the larva-adult period; weight of newly emerged adults (male and female); duration of pre-oviposition and oviposition periods; male and female longevity and fecundity. The development of the insect under different larval densities (100, 200, 400 and 600 larvae), using the same amount of natural diet, (corn seedlings) was also evaluated. When the insects were reared on corn kept in wet vermiculite the viability of the larva-adult period was higher than when corn was kept on wet paper sheet; the opposite was observed with the length of the developmental period. Females reared in artificial diet had lesser pre-oviposition and oviposition periods and laid less eggs than those reared in natural diet. The increase in the larval density extended the duration of the immature phases, decreased the viability of the larva-adult period and reduced the weight of adults. The rearing technique of D. speciosa using natural diet in vermiculite provided a large amount of insects, with a significant reduction in labor and laboratory space.

Aspectos Biológicos e Comportamentais de Liogenys suturalis Blanchard (Coleoptera: Melolonthidae) no Mato Grosso do Sul

Liogenys suturalis Blanchard is one of the main soil pests associated to corn, wheat and oat crops in the Southern Mato Grosso do Sul State. This work aimed to investigate the bioecological and behavioral aspects of this pest. The study was carried out in several municipalities of Mato Grosso do Sul State under field and laboratory conditions from August 2004 to December 2006. In the laboratory, we studied the incubation period and egg viability, the number of instars, and pupal and adult sex-related traits. The insect distribution was determined yearly, as well as the period of insect flying and some behavioral aspects during mating. Egg viability averaged 81.7%, with an incubation period of 22.8 ± 4.32 days. Liogenys suturalis took the whole year to complete its life cycle, developing through three different instars. The highest larval feeding activity and development occurred in February and June, and adult flight activities were between the second fortnight of September and December. Sex dimorphism was observed in both pupae and adults. Flights were concentrated from 7:00 to 8:00 PM. The average time for mating was 9.82 min. The observed adult sex ratio was 0.63.

Efeito do regulador de crescimento lufenuron na reprodução de Diabrotica speciosa (Germar) (Coleoptera: Chrysomelidae)

The effect of lufenuron (Match CE), an insect growth regulator, on the fecundity and egg hatchability of Diabrotica speciosa (Germar) (Coleoptera: Chrysomelidae) was evaluated under controlled conditions. Newly-emerged adults from a stock culture were sexed and transferred to acrylic cages (1 couple/cage). Fifteen couples were fed on lufenuron-treated bean (Phaseolus vulgaris, L.) leaves during 13 d after emergence. Thereafter, they were fed on untreated bean leaves. The same number of couples were fed on untreated bean leaves during all period of observation. Adult fecundity and egg hatchability were evaluated until the 34 d after emergence. The mean number of eggs laid/female (177.5) and the egg hatchability (19.8 %) were lower when insects were fed on lufenuron-treated leaves compared to 375.4 eggs and 68.7 % of hatchability when insects were fed on untreated leaves, respectively. Lufenuron seems to affect the embryonic development of D. speciosa by means of a transovarian action, thus avoiding larval eclosion. Results show the possibility of applying lufenuron to reduce the offspring production of D. speciosa when adults are fed on treated plants.

Consumo e utilização de alimento por Diatraea saccharalis (Fabr.) (Lepidoptera: Pyralidae), Heliothis virescens (Fabr.) e Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae) em duas temperaturas

The goal of this work was to determine the most suitable temperature for rearing Spodoptera frugiperda (J.E. Smith), Diatraea saccharalis (Fabr.) and Heliothis virescens (Fabr.) in artificial diet, by means of measures of food intake and utilization between 25 and 30oC. Fifty worms per species, individualized and kept in 8.5 cm long and 2.5 cm diameter glass containers were studied at the temperatures mentioned, 60±10% RH, and 14 hour photophase. Based on dry matter, one determined worm weight at maximum development, food consumed and feces eliminated at both conditions (25 and 30oC) and the nutritional ratios: relative consumption ratio (RCR), relative growth ratio (RGR), relative metabolic ratio (RMR), approximate digestibility (AD), efficiency of conversion of ingested food (ECI) and efficiency of conversion of digested food (ECD). The most suitable temperature for S. frugiperda was 30oC since it provided higher weight at the maximum development, higher weight gain, higher growth ratio, higher ECI, higher ECD, and lower metabolic cost. On the other hand, no differences regarding nutritional rates were observed for either H. virescens or D. saccharalis evaluated at both thermal conditions. Thus, for one generation and based on nutritional rates, the highest temperature (30oC) is recommended for laboratory maintenance of S. frugiperda. As for the other species, rearing at 25 or 30oC is indifferent.

Leaf consumption by Diabrotica speciosa (Coleoptera: Chrysomelidade) adults on difFerent host plants

Studies related to the feeding behavior of pest insects provide information that will aid the development of control tactics. Leaf consumption by Diabrotica speciosa adults fed on bean, corn, potato and soybean was determined in the laboratory under free-choice (multiple or double-choice) and no-choice (confinement) conditions. In the multiple-choice tests leaf circles were randomly arranged in a circular pattern (arena) inside Petri dishes. The degree of preference for the hosts was determined under double-choice conditions, where common bean was considered the standard host and the remaining plants (soybean, potato and corn) as test hosts. In all trials, two Diabrotica speciosa couples were released and maintained within the dish for 24 hours; the leaf area consumed by the insects was determined after this feeding period. Food type (host) influenced leaf area consumption by D. speciosa adults both in free-choice and in no-choice tests (P 0.05). As to the no-choice test, the consumption was higher for corn than for potato, probably to compensate the low nutritional quality of the first host.

Patogenicidade de isolados de Metarhizium anisopliae (Metsch.) Sorokin e de Beauveria bassiana (Bals.) Vuillemin a Scaptocoris carvalhoi Becker (Hemiptera, Cydnidae)

Pathogenicity of the fungi Metarhizium anisopliae (Metsch.) Sorokin and Beauveria bassiana (Bals.) Vuillemin to stinkbug Scaptocoris carvalhoi Becker, 1967 was evaluated under laboratory and greenhouse conditions. Experiments were carried out at Embrapa Agropecuaria Oeste, Dourados, Mato Grosso do Sul State, Brazil, in 2003. Ten M. anisopliae and eleven B. bassiana isolates were evaluated in laboratory using a completely randomized experimental design with five replicates (10 adults and 5 nymphs/plot). The pathogenicity of M. anisopliae isolate (Ma69) was also separately evaluated against nymphs and adults in laboratory and greenhouse. The stinkbug mortality levels were higher for M. anisopliae isolates (between 73.3% and 94.7% than for B. bassiana isolates (between 10.7% and 78.7%). In greenhouse, stinkbug mortality due to the M. anisopliae isolate (Ma69) was 57.3%, and there was no difference of mortality for nymphs and adults of stinkbug in laboratory. However, in greenhouse, mortality levels were significantly higher (p<0,05) for nymphs (38,4%) than for adults (16,2%). From these data, we conclude that M. anisopliae isolate Ma69 was efficient to control S. carvalhoi in laboratory and in greenhouse, thus being a promising choice for use as a microbial insecticide under field conditions.

Biology and fertility life table of Helicoverpa armigera (Lepidoptera: Noctuidae) in different hosts

In 2013, the presence of Helicoverpa armigera (Hübner) was reported in cotton, soybean, corn and weeds in diverse regions of Brazil. We studied the biology and the fertility life table of this pest when reared on cotton (293 cv. CNPA RF), soybean (cv. Brasmax Power), corn (cv. BRS 1010), wheat (cv. BR 18) and on an artificial diet. Caterpillars were reared using the vegetative and reproductive structures of the hosts, under laboratory conditions (temperature 25 ± 1°C; relative humidity (RH) 70 ± 10%; photoperiod =14 h). The experimental design was completely randomized, with five treatments (four host plants and artificial diet) and 17 replications. Significant effects were verified for the different types of hosts tested on the growth of the insect as well as on fecundity and laying rate. The results showed that cotton and soybean had higher viability at the stages of growth, higher rate of survival of adult females in the reproductive period than the other host crops, and similar values for insects reared on an artificial diet, which reveals that cotton and soybean can be appropriate for rearing H. armigera on a natural diet. Corn and wheat showed high larval and pupal mortality and low biotic potential.

Flutuação populacional da cigarrinha-do-milho em duas localidades do Mato Grosso do Sul

The leafhopper of corn, Dalbulus maidis (DeLong & Wolcott, 1923) (Hemiptera: Cicadelidae), is considered one of the main corn pest due to its damage of sap suction and disease transmission to plants. This work had the aim to get information about population fluctuation of D. maidis in the Southern region of Mato Grosso do Sul State. Yellow stick cards of double side (7 by 12cm) were installed fortnightly on a wood frame of 0.5m and 1.5 above soil surface within areas cultivated with corn in Dourados and Ponta Pora, MS and stayed in the area for seven days. The same kind of traps was also installed in a grass-plot of Dourados, MS without corn crop nearby. Two peaks of leafhopper were observed being one during the dry period (the period without corn in the field - between July and September) and the other during summer (between December and January). Stick traps installed at 0.5m above soil surface did capture significantly more leafhopper than the ones installed at 1.5m if we consider all sampling carried out during the two years of study.