João Paulo Pereira Paes

Trichogramma pretiosum (Hymenoptera: Trichogrammatidae) Parasitism of Trichoplusia ni (Lepidoptera: Noctuidae) Eggs Under Different Temperatures

ABSTRACT A study of the biological characteristics and thermal requirements of the parasitoid Trichogramma pretiosum Riley, 1879 (Hymenoptera: Trichogrammatidae) on eggs of Trichoplusia ni (Hübner, 1802) (Lepidoptera: Noctuidae) at several different temperatures was performed in this work. Eggs of T. ni were exposed to T. pretiosum strain Tspd parasitism for 5 hr and then transferred to environmentally controlled growth chambers set at the temperatures of 18, 21, 24, 27, 30, and 33 ± 1°C. The duration of the T. pretiosum egg-to-adult period was affected by temperature, varying from 6 to 18 d over the range of the studied temperatures. The number of individuals emerged per egg and the sex ratio also were affected by temperature variations, but regression analysis did not find correlation between the increase of temperature and the observed variation of these biological parameters. Similarly, parasitism viability (percentage) was influenced by temperature variation, but always exceeded 80% at all tested temperatures. The thermal lower limit of development (Tbase) and the thermal constant (K) for T. pretiosum were 11.84°C and 128.37 DD, respectively. These results here reported indicate that T. pretiosum was impacted by the temperature, however, this parasitoid had a satisfactory performance on T. ni eggs at all studied temperature (from 18 to 33°C), showing potential to be used successfully as a biological control agent of this pest in different regions that fit in this tested temperature range. Also, the rearing temperature of this parasitoid might be changed from 18 to 33°C, according to commercial demands for accelerating or retarding mass production for field releases without damages to the parasitoid development.

Seleção de isolados de Beauveria bassiana potenciais para o controle da traça-das-crucíferas

Diamondback moth (DBM), Plutella xylostella (Lepidoptera: Plutellidae), is considered the most important pest of brassicas worldwide and the use of insecticides is the most used method to control this pest. Thus, the objective of this research was to select isolates of Beauveria bassiana with viability to control DBM. Seventeen isolates and one commercial product of B. bassiana were tested. DBM 2nd instar larvae were treated with conidial suspension at concentration of 107 conidia mL-1. For lethal concentration (LC) bioassay seven concentrations spaced on logarithmic scale were tested. The isolates CCA/UFES-4, 18, 31 and 35 were selected for LC bioassay because they caused over 90% confirmed mortality. The standard isolate ESALQ-447 and the commercial product had similar results and were also selected for LC bioassay. Based on the values estimated for LC50, the isolates CCA/UFES-4, 18, 31, ESALQ-447 and the commercial product can be selected for use in DBM control.

Does mating interfere in the biological characteristics of a population of Trichogramma pretiosum

Trichogramma spp. are parasitoids used in the regulation of insect populations that can cause economic damage. In order to ensure good performance, understanding some of their biological characteristics is essential. The objective of this study is to evaluate whether mating interferes with the biological characteristics of a population of Trichogramma pretiosum collected in the field. In all experiments, groups of mated and unmated females were used. We also verified any interference from mating on the biological characteristics of the offspring. We found that mating can alter the parasitism and longevity of genitor females, in addition to changing longevity among the descendants, but once parasitized, the eggs develop normally, showing similar emergence percentage and number of offspring as those from unmated females. In addition, we verified that the population of T. pretiosum collected in the field presented individuals with reproductive thelytokous and arrhenotokous characteristics. This fact highlights the importance of careful investigation on the reproduction mode of populations collected in the field, thus avoiding problems in the effective management of insect populations.

Thermal requirements, development and number of generations of Duponchelia fovealis (Zeller) (Lepidoptera: Crambidae)

In this study, the effect of temperature on the growth of the European pepper moth, Duponchelia fovealis (Zeller), was assessed at five constant temperatures (18, 21, 24, 27 and 30 °C). The European pepper moth was observed to complete its developmental stages (from egg to adult) at all the temperatures evaluated. From the results, it was evident that temperature affected the rate and development time of all the growth stages, to a significant degree. The length in time of the embryonic, larval, pupal and total (egg-adult) stages was observed to drop as the temperature rose from 18 to 24 °C, but remained constant between 27 and 30 °C. The developmental time in the pre-pupal stage dropped between 18 and 30 °C. The European pepper moth takes 454 degree-days to complete development at 11.7 °C temperature threshold. The D. fovealis survival was thus inversely proportional to temperature over range of 18 to 30 °C. On assessing the number of annual generations for the five largest strawberry-producing municipalities in Espírito Santo State, an average of 5.5 generations per year was estimated. This is a first report of temperature on D. fovealis development.

CARACTERIZAÇÃO QUÍMICA E EFEITO DO ÓLEO ESSENCIAL DE ERVA-DE-SANTA-MARIA SOBRE O ÁCARO-RAJADO DE MORANGUEIRO

The twospotted spider mite, Tetranychus urticae Koch (1836)(Acari: Tetranychidae), is the major pest in strawberry. The objective of this study was the chemical characterization of the essential oil of Chenopodium ambrosioides L. and the evaluation of their effects on twospotted spider mite. The compounds of the essential oil were identified by GC/FID and GC/MS analysis. The mortality and oviposition were evaluated after spraying the oil (2.5, 5.0, 7.5 and 10.0% v v-1) on twospotted spider mite females. The yield of the essential oil was of 0.3% and the compounds identified were (Z)-ascaridol (87%), (E)-ascaridol (5.04%), p-cymeno (4.83%), a-terpinene (1.24%) and piperitone (0.7%). The highest values for mortality and reduction of oviposition observed were 85% and 69%, respectively. C. ambrosioides essential oil is a promising option for the management of twospotted spider mite.