Reginaldo Barros

Population dynamics of Aceria guerreronis Keifer (Acari: Eriophyidae) and associated predators on coconut fruits in Northeastern Brazil

Aceria guerreronis Keifer can cause severe damage to coconuts in several countries around the world. Rare studies have been conducted to determine the predatory mites associated with A. guerreronis in Brazil. The study evaluated the prevalence of A. guerreronis and associated predators on the bracts and on the surface of the fruits underneath the bracts, for 12 months, on coconut palms grown along the coast of the States of Alagoas, Paraíba and Pernambuco, Northeastern Brazil. Mites of 10 families were found, but by far the most abundant species was A. guerreronis, corresponding to 99.5% of the mites collected. The prevailing species amongst the predators were the Phytoseiidae mites Neoseiulus baraki (Athias-Henriot) and Neoseiulus paspalivorus (De Leon). These are flat mites that have short limbs, characteristics that allow them to invade the main habitat occupied by A. guerreronis. Other predators were found, but in low numbers, due mainly to their difficulty in reaching the fruit areas most inhabited by A. guerreronis. However, these mites could prey on that pest when it leaves its preferred habitat to disperse. No significant correlations were observed between the levels of abiotic factors and the population levels of A. guerreronis or of the phytoseiids associated with it. This probably occurred due to the simultaneous and conflicting effects of those factors on the mites in the field, or to significant differences between the climatic factors measured in the environment and those prevailing in the habitat occupied by A. guerreronis.

Efeito de extratos aquosos de plantas no desenvolvimento de Plutella xylostella (L. ) (Lepidoptera: Plutellidae)

The effects of aqueous extracts of different plant species on the development of Plutella xylostella (L.) were studied. Leaf discs of kale cultivar Portuguesa, Brassica oleracea var. acephala, were dipped in each plant extract per 30 seconds. Twelve neonate P. xylostela larvae (<12h) were fed on treated leaf discs and kept in petri dishes. The leaf discs were replaced at two-day intervals by fresh leaf discs treated with the plant extracts. Larvae of P. xylostella which fed on leaf discs treated with Melia. azedarach L. and Cissampelos aff. glaberrima St. Hil. delayed their development by 3.5 and 1.7 days, respectively. However, the other plant extracts studied did not affect larva development. Extracts of Aspidosperma pyrifolium Mart., Azadirachta indica A. Juss., and A. indica oil formulation caused 100% mortality of P. xylostella larvae, while, the extracts of M. azedarach, C. aff.glaberrima, Laurus nobillis L., Prosopis juliflora DC, Croton sp. and Eugenia uniflora L. caused larval mortality of 96.7, 93.3, 83.3, 66.7, 63.3 and 60%, respectively. The other studied extracts did not cause significant larval mortality. Duration of pupae stage was not affected by the studied plant extracts, however, the extracts of M. azedarach, L. nobillis, C. aff. Glaberrima and Croton sp. caused 100, 90, 66.7 and 65% of pupae mortality, respectively.

Efeito de extratos aquosos de Azadirachta indica, Melia azedarach e Aspidosperma pyrifolium no desenvolvimento e oviposição de Plutella xylostella

Foram avaliados a CL50 e o efeito de extratos aquosos de plantas na biologia, oviposicao e periodo embrionario de Plutella xylostella L. (Lepidoptera: Plutellidae). Para determinacao da CL50 foram utilizadas concentracoes entre 0,03 e 0,8 % para amendoas de Azadirachta indica (A. Juss.) 0,5 e 7,0 % para casca de Aspidosperma pyrifolium (Mart.) e 0,5 e 12,5 % para frutos de Melia azedarach (L.), obtendo-se as CL50 de 0,06; 2,17 e 2,90%, respectivamente. Verificou-se que os extratos aquosos de todas as especies vegetais afetaram o desenvolvimento do inseto, principalmente na fase larval. Na fase de pupa, os extratos reduziram a massa e a viabilidade. Houve deformacao de adultos para os extratos de A. pyrifolium e M. azedarach e o de A. indica causou maior porcentagem. Todos os extratos possuem efeito toxico para ovos de P. xylostella, sendo dependente do aumento da concentracao. Nos extratos da casca de A. pyrifolium, do fruto de M. azedarach e da amendoa de A. indica observa-se acao ovicida quando usados na concentracao letal de lagartas de primeiro instar da praga. Em observacoes do ovo de P. xylostella com auxilio de um microscopio eletronico de varredura, verificou-se a existencia de microporos onde pode ocorrer a penetracao do produto ovicida, alem da constatacao da textura rugosa da casca do ovo que pode reter ou fixar os extratos.

Superparasitism and host size effects in Oomyzus sokolowskii, a parasitoid of diamondback moth.

Many aspects of a parasitoid’s biology may be affected by its host. Host size, for example, could affect parasitoid fitness, especially in gregarious parasitoids, in which the resource is used by multiple siblings. Oomyzus sokolowskii (Kurdjumov) (Hymenoptera: Eulophidae) is a gregarious larval–pupal endoparasitoid of the diamondback moth, Plutella xylostella L. (Lepidoptera: Plutellidae), a major pest of crucifers worldwide, and is able to superparasitize the host. This study focuses on the hypothesis that because resource availability is higher in larger hosts, parasitoids developing in larger hosts will fare better. However, superparasitized hosts are expected to yield larger numbers of parasitoid offspring of smaller body size. Results showed that superparasitism increased the number of parasitoid offspring produced per host and increased offspring longevity, but decreased offspring body size. However, developmental time and sex ratio of parasitoid offspring was similar among hosts parasitized once, twice, or three times. Regardless of superparasitism, parasitoids emerging from larger hosts that were fed honey solution lived longer than similarly fed progeny from smaller hosts (36.4 vs. 22.1 days). The results partially support the hypothesis that Oomyzus gained fitness from an increase in host size; moreover, superparasitism seems advantageous for Oomyzus due to increased offspring numbers and longevity.

Efeito das plantas do algodoeiro e do tomateiro, como complemento alimentar, no desenvolvimento e na reprodução do predador Podisus nigrispinus (Dallas) (Heteroptera: Pentatomidae)

The occasional feeding on plants by Podisus nigrispinus (Dallas) has produced different responses on its biology according to the plant species available. This study was undertaken to determine the development and reproduction of P. nigrispinus when confined on Gossypium hirsutum cv. Precocious CNPA1 and processing tomato Lycopersicum esculentum cv. IPA5 plants, using Tenebrio molitor (L.) pupa as prey. Nymphs and adults of P. nigrispinus were provided with prey and plants of cotton, prey and plant of tomato, prey and water, and only the prey. The predator could access the plants by caging nymphs and prey on plant leaves cultivated in pots. Nymphs caged on cotton or tomato plants with prey showed shorter duration of second and fifth instars. However, the shortest development period was observed for nymphs caged on cotton plants with prey. Nymphs fed on prey alone had lower survival within each instar and for the whole stage when compared to nymphs accessing plant, prey and water. The availability of cotton plants to nymphs produced heavier individuals compared to tomato plants, prey and water, and only prey. The adult weight at emergence was similar between plants and prey plus water, and superior to the treatment with prey alone. However, females of P. nigrispinus with access to the prey and cotton plant and prey and water showed significant body weight increase at the beginning of the reproductive activity, while females confined on tomato plants and only on prey did not range their weight during their lives. The availability of cotton and tomato plants to P. nigrispinus increased the number of eggs produced and adult longevity; moreover the former plant promoted higher oviposition frequency. Based on the results on net reproduction rate, intrinsic rate of increase and generation time, calculated for P. nigrispinus, the populations improved according to the plant species available and showed better response when confined with prey on cotton plants, followed by tomato plants. Also, insects fed on water plus prey developed better than those fed only on the prey.

Chemical composition and acaricidal activity of the leaf and fruit essential oils of Protium heptaphyllum (Aubl.) Marchand (Burseraceae)

Essential oils from leaves and fruits of Protiumheptaphyllum collected in Tamandare beach Pernambuco/Brazil were analysed by GC/MS and tested for toxicity and repellent effect against the two spotted spider mite (Tetranychus urticae). The major constituent identified in the fruits was a-terpinene (47.6 %) whereas oil from leaf contained mainly sesquiterpenes such as 9-epi-caryophyllene (21.4 %), trans-isolongifolanone (10.7 %) and 14-hydroxi-9-epi-caryophyllene (16.7 %). The fruit oil was found to be more effective against the mite when compared to the leaf oil. Both showed mortality properties and oviposition deterrence in higher concentration (10 µl.l-1 air), but only the essential oil from fruits induced repellence on T. urticae.

Biologia e exigências térmicas de Trichogramma pretiosum Riley e T. exiguum Pinto & Platner (Hymenoptera: Trichogrammatidae) criados em ovos de Plutella xylostella (L.) (Lepidoptera: Plutellidae)

This biology of Trichogramma pretiosum Riley and T. exiguum Pinto & Platner in Plutella xylostella (L.) eggs was studied at seven constant temperatures, and the thermal requirements and number of generations of both parasitoids was determined for some crucifers producers of the states of Espirito Santo and Pernambuco. Eggs of P. xylostella were submitted to parasitism by T. pretiosum and T. exiguum for 5h, and transferred to climatic chambers regulated to 18, 20, 22, 25, 28, 30 and 32oC. The developmental time was influenced by the temperature varying from 6.8 to 23.1 days for T. pretiosum and 6.9 to 22.0 days for T. exiguum at 32 and 18°C, respectively. The percentage of emergence was higher at 28oC, reaching 86% for both species. The sex ratio was always 1 for T. pretiosum and varied from 0.6 to 0.9 for T. exiguum. The thermal constant (K) and base temperature (Tb) were higher for T. exiguum (129.99 days degrees and 13.13oC) when compared with T. pretiosum (123.03 days degrees and 12.52oC). The estimated number of annual generations of T. pretiosum and T. exiguum for Gravata district was 36.9 and 36.7 generations respectively. The same number, however for Muniz Freire, ES, was 24.1 and 24.5, and for Alegre, ES, 26.7 and 27.0 generations for T. pretiosum and T. exiguum respectively.

Exigências térmicas e estimativa do número de gerações de Oomyzus sokolowskii (Kurdjumov) (Hymenoptera: Eulophidae), para regiões produtoras de crucíferas em Pernambuco

This research was carried out to determine the thermal requirements of Oomyzus sokolowskii (Kurdjumov) reared on the diamond back moth (DBM), Plutella xylostella (L.), and to estimate the number of generations under laboratory conditions in crucifers growing in Pernambuco State, Brazil. Fourth instar DBM larvae were exposed to parasitism by O. sokolowskii for 24h and maintained at the following temperatures: 15, 18, 22, 25, 28, 30, and 33oC. Duration of O. sokolowskii immature phase (egg-larvae-pupae) was temperature dependent, ranging from 12.9 to 31.6 days, at 28oC and 18oC, respectively. Survival of O. sokolowskii immature phase was also influenced by temperature, being higher (77.2%) at 28oC. Temperatures below 22oC and above 28oC were shown inadequate to rear the parasitoid. The number of adults emerged from DBM pupae was not affected by temperature and ranged from 7.3 to 12.0. The sexual ratio ranged from 0.86 to 0.91 and did not present difference among the temperatures. The lower threshold temperature (Tb) and the thermal requirements (K) for immature phase of O. sokolowskii were 11.6oC and 211.8 degree-days, respectively. Comparison of these results to P. xylostella thermal requirements (Tb = 8,85oC and K = 299,67 GD) denotes that along the year, the number of generations of O. sokolowskii is always higher than that of P. xylostella, evidencing that O. soklowskii could develop up to 24 generations an year, while DBM could reach 20 annual generations.

New records of natural enemies of Plutella xylostella (L.) (Lepidoptera: Plutellidae) in Pernambuco, Brazil

We report the occurrence of natural enemies of Plutella xylostela (L.) in organically farmed kale in Pernambuco, Brazil. Seven natural enemies were observed parasitizing or preying on larvae and pupae of P. xylostella--three parasitoids: Cotesia plutellae Kurdjumov (Hym.: Braconidae), Conura pseudofulvovariegata (Becker) (Hym.: Chalcididae) and Tetrastichus howardi (Olliff) (Hym.: Eulophidae), and four predators: Cheiracanthium inclusum (Hentz) (Araneae: Miturgidae), Pheidole sp.Westwood (Hym.: Formicidae), nymphs and adults of Podisus nigrispinus (Dallas) (Hem.: Pentatomidae), and one unidentified species of solitary wasp. Beyond recording these natural enemies, data on predation of P. xylostella larvae in the field and laboratory by C. inclusum are presented.

Suscetibilidade de Plutella xylostella (L.) (Lepidoptera: Plutellidae) aos fungos Beauveria bassiana (Bals.) Vuill. e Metarhizium anisopliae (Metsch.) Sorok

An initial screening was undertaken using the isolates ESALQ 447, ESALQ 760, ESALQ 900, ESALQ 634, IPA-205 and ESALQ 760 of B. bassiana, and ESALQ E9, IPA-207, ESALQ 860, IPA-204 and UFPE 3027 of M. anisopliae at the concentration of 108 conidia/ml for the diamondback moth (DBM) second instar. All isolates tested caused DBM larval mortality ranging from 70% to 96%, except the M. anisopliae isolate UFPE 3027, which resulted in a mortality of 26%. Based on this survey the isolates ESALQ 634 and ESALQ 447 of B. bassiana and IPA-207 and ESALQ E9 of M. anisopliae were chosen and assessed at the concentrations 105, 106, 107 and 108 conidia/ml for DBM second instar. These selected isolates at concentrations higher than 106 conidia/ml caused DBM larval mortality ranging from 58% to 96%. The mean lethal time (LT50) for DBM second instar were 1.1 and 4.3 days, and 0.7 and 5.8 days for B. bassiana isolates ESALQ 634 and ESALQ 447 and M. anisopliae isolates IPA-207 and ESALQ E9, respectively. Based on the lethal concentrations (LC50) the isolates IPA-207 and ESALQ E9 were seven times more virulent to DBM second instar than B. bassiana isolates ESALQ 634 and ESALQ 447. These results showed that DBM larvae were more susceptible to M. anisopliae than to B. bassiana and that M. anisopliae isolates IPA-207 and ESALQ E9 may be a valuable component for the integrated management of DBM larvae.