Hugo Bolsoni Zago

Ocorrência de Trichogramma pretiosum em áreas comerciais de tomate, no Espírito Santo, em regiões de diferentes altitudes

Foram instalados sete campos experimentais em altitudes entre 200 e 1050 metros, nos municipios de Afonso Claudio e Venda Nova do Imigrante no Espirito Santo, para desenvolvimento de avaliacoes pre-introdutorias de Trichogramma. Visou-se determinar as especies nativas e conhecer o indice de parasitismo natural, para utilizacao em programas de manejo integrado da traca-do-tomateiro. Em todos os campos comerciais de tomateiros foram coletados apenas Trichogramma pretiosum Riley. No primeiro ano de coleta, o numero medio de amostras de cartelas com parasitismo, bem como o numero medio de ovos parasitados, apresentaram uma relacao inversa, quando comparado com as regioes de altitudes entre 200 e 850 metros. Em regioes de menor altitude (200, 380 e 450 metros), foram observadas presenca constante desses parasitoides de ovos em todas as areas amostradas. No segundo ano de coleta nao foi observado o mesmo comportamento em relacao ao primeiro, tendo os valores medios dos parâmetros sido inferiores, com o numero medio de ovos parasitados por cartela reduzido pela metade. Os resultados de dois anos de coleta mostraram que a agressividade das linhagens de T. pretiosum foi diferenciada em funcao das areas.

Capacidade de parasitismo de Trichogramma pratissolii Querino & Zucchi (Hymenoptera: Trichogrammatidae) em hospedeiros alternativos, sob diferentes temperaturas

The successful use of Trichogramma as biocontrol agent depends on its mass production in laboratory, a fundamental step for any biological control program among other factors. This work investigated the parasitism capacity of Trichogramma pratissolii Querino & Zuchi (Hymenoptera: Trichogrammatidae), a new recorded Trichogramma species, parasitizing eggs of Anagasta kuehniella (Zeller) and Corcyra cephalonica (Stainton) (Lepidoptera: Pyralidae) under the temperatures of 15, 18, 21, 24, 27, 30 and 33 degree Celsius. Eggs of these hosts were offered to newly emerged females during 24h. This procedure was repeated daily for each female and each temperature up to female death, in order to estimate daily and accumulated parasitism, and female longevity. On both hosts, the daily parasitism decreased as function of the female age. Under all temperatures studied and both hosts the highest rate of parasitism was observed during the first 24h of host exposure, and reached 80% of total parasitism in the 4th and 3rd days when parasitizing A. kuehniella and C. cephalonica, respectively. On both hosts, the highest parasitism rate was observed under temperatures from 21 degree Celsius to 27 degree Celsius. Average longevities of T. pratissolii females deprived of food emerging from A. kuehniella and C. cephalonica lived for 1.0 and 8.9 days when reared at 15 degree Celsius e 33 degree Celsius, respectively. The results indicate that eggs of A. kuehniella and C. cephalonica and temperatures from 21 degree Celsius to 27 degree Celsius were appropriate to rear T. pratissolii.

Biologia e exigências térmicas de Trichogramma pratissolii Querino & Zucchi (Hymenoptera: Trichogrammatidae) em hospedeiros alternativos

The objective of this work was to study the biology and determine the thermal requirements of Trichogramma pratissolii Querino & Zucchi reared on Anagasta kuehniella Zeller (Lepidoptera: Pyralidae) and Corcyra cephalonica Stainton (Lepidoptera: Pyralidae) at 15, 18, 21, 24, 27, 30 and 33 masculineC. The highest percentage of emergence of T. pratissolii was obtained at 27 masculineC on A. kuehniella and from 24 masculineC to 30 masculineC on C. cephalonica. The lower threshold temperature (Tb) and the thermal requirement (K) of T. pratissolii were 12.59 masculineC (Tb) and 122.85 degree-days (K) when reared on A. kuehniella and 11.73 masculineC (Tb) and 139.80 degree-days (K) on C. cephalonica. These results indicate that both A. kuehniella and C. cephalonica are suitable hosts for T. pratissolii mass rearing. The optimal temperature for the immature development and emergence of T. pratissolii on A. kuehniella was 27 masculineC and 24 masculineC to 30 masculineC on C. cephalonica.

Egg distribution of Plutella xylostella (L.) (Lepidoptera: Plutellidae) and the parasitism by Trichogramma pretiosum Riley (Hymenoptera: Trichogrammatidae)

Oviposition site preference of Plutella xylostella (L.) and the parasitism by Trichogramma pretiosum Riley on cabbage plants at pre- and post-head formation were investigated in commercial cabbage field. Groups of six plants were randomly caged. In each cage three pairs of 24h-old P. xylostella moths were released, followed by 1,200 T. pretiosum females released 12h later. After 48 h from parasitoid release, plants were harvested and fully inspected with the oviposition mapped according to the leaf position and their parts (basal, median and border) and upper and bellow leaf surfaces. Moth oviposition and egg parasitism were equally distributed across the plant leaves at the pre-head formation stage. At this stage, the basal part and the upper leaf surface were the preferred places for oviposition and egg parasitism, respectively. Cabbage plants at the post-head formation stage exhibited greater oviposition and egg parasitism in the inner leaf attached to the head. At this stage, the leaf border and the upper leaf surface were the preferred places for oviposition and egg parasitism, respectively. The infestation of P. xylostella on cabbage can be determined by egg counting at the pre- and post-head formation stages at the basal part of the leaves or at the border of the leaf attached to the head, respectively. And, in both plant stages parasitized eggs by T. pretiosum are more likely to be found at the upper leaf surface.

Efeito da disponibilidade de hospedeiro e de alimento nas características biológicas de Trichogramma galloi Zucchi (Hymenoptera, Trichogrammatidae)

Biological characteristics of Trichogramma galloi Zucchi, 1988 were evaluated in laboratory where these parasitoids were reared on eggs of Diatraea saccharalis (Lepidoptera, Pyralidae) with or without honey, and exposed to eggs of the host after 0, 6, 12, 24, 36, 48, 60, 72 and 84 hours of emergence. The parasitism rate and viability showed higher for individuals that received food. The sex ratio was not influenced by food. The number of individuals per egg only showed difference for those adults that did not receive food and stayed six hours without the host eggs. Checking the effect of the availability of eggs, only the sex ratio, with or without honey, did not show differences. The results show that T. galloi needs a carbohydrate supply and the time can influence the reproductive capacity.

CARACTERIZAÇÃO QUÍMICA E TOXICIDADE DE ÓLEOS ESSENCIAIS CÍTRICOS SOBRE Dysmicoccus brevipes (HEMIPTERA: PSEUDOCOCCIDAE)

The insect Dysmicoccus brevipes (Hemiptera: Pseudococcidae) has been reported as an important pest for several crops, especially coffee. The citrus essential oils can be obtained as by-products of the citrus-processing industry and have been tested as an alternative to control different insect groups. Therefore, the objective of this work was to determine the chemical composition and evaluate the toxicity of commercial sweet orange (Citrus sinensis), bitter orange (Citrus aurantium) and Sicilian lemon (Citrus limon) essential oils and pure monoterpene D-limonene on D. brevipes. The essential oils were analyzed by gas chromatography. Two bioassays were conducted; the first assessing the insect mortality in all oils and the second assessing the lethal concentrations (LC50 and LC95) of the most effective oils. The main components of the oils were D-limonene (83.33%) and Linalool (8.91%) (sweet orange); D-limonene (78.53%) and γ-terpinene (12.65%) (bitter orange); D-limonene (59.78%), beta-pinene (14.71%) and γ-terpinene (10.19%) (Sicilian lemon) and the compound D-limonene had 97% of purity. The highest mortalities were found with the use of the Sicilian lemon (98.68%) and sweet orange (94.11%)oils. The sweet orange oil presented lethal concentrations at 2.21% (LC50) and 3.55% (LC95), and the Sicilian lemon oil at 0.72% (LC50) and 2.91% (LC95). The main component of the sweet orange and Sicilian lemon essential oils was the D-limonene, and the Sicilian lemon oil was most effective oil to control D. brevipes.