Thermal requirements, life table and estimate of number of Trichogramma galloi in eggs of Neoleucinodes elegantalis

The Neoleucinodes elegantalis is considered one of the main tomato pests, as it directly damages the fruit. The use of the parasitoid Trichogramma galloi in the management of N. elegantalis requires studies for knowledge of parasitoid behavior regarding the pest to be managed. The objective of this research was to evaluate the behavior of T. galloi for the management of N. elegantalis, through thermal requirements and of life table. According to the results, the fetal develop of T. galloi starts when the temperature remains above 8.02 ± 0.2°C and the heat buildup for complete development is of 159.74 ± 3.88°C degree days (DD). The number of generations of T. galloi was estimated to the five largest municipalities from the Espírito Santo state (Venda Nova do Imigrante, Domingos Martins, Conceição do Castelo, Vargem Alta and Santa Maria do Jetibá), checking that T. galloi may have 24.72 to 35.37 generations per year according to the temperatures reached in each region studied. Keywords— biological control, parasitoid, pest management, small fruit borer, tomato.


I. INTRODUCTION
The small fruit borer, Neoleucinodes elegantalis (Guenée) (Lepidoptera: Crambidae) is considered one of the main tomato pests, as it directly damages the fruit, making them unfit for consumption and industrial processing, with lossy that vary of 20 to 90% (Picanço et al., 2007;Moraes & Foerster, 2015;Silva et al., 2017). This species occurs, mainly, in the neotropical area, reaching the Central America and the South America (Querino, 2002;Moraes & Foerster, 2015;Silva et al., 2017).
In addition to causing serious damage to tomato fruit, this pest still has other host plants like solanaceae (scarlet eggplant, bell pepper and eggplant), besides weeds like joa and the jurubeba (Fornazier et al., 2010;Pratissoli, 2015).
There are few studies to indicate alternative tactics for the management of N. elegantalis, because caterpillars penetrate the newly hatched fruit and remain inside the fruit until the pupal phase. This fact induces the producer to make constant pesticide applications (Plaza et al., 1992;Oliveira et al., 2017).
The Phytosanitary Pest Management is the establishment of control strategies that involve all the knowledge related to the biological cycle of culture, insect pest and of environmental factors. This kind of pest management involves pest control methods aimed at reducing producer costs over time, optimize production and reduce environmental impacts, mainly through lower use of chemical insecticides França et al., 2015).
Currently, the biological control assumes great importance in the pest management context, especially in the face of discussions for more sustainable agriculture, with less aggression to the environment and human health. A viable option, for the management of this pest, is the use of the egg parasitoid of the genre Trichogramma because the control of N. elegantalis is performed in the egg phase (Querino, 2002;Diaz & Brochero, 2012Zucchi et al., 2015.
The use of this parasitoid in the management of N.

II. MATERIAL AND METHODS
The laboratory creation of Neoleucinodes elegantalis occurred in air conditioned room (25 ± 2 ºC, 70 ± 10% of relative humidity (RH) and 12 h of photophase). The adults N elegantalis were kept in acrylic cages and fed with honey solution at 10%. The tomato fruits were packed in oviposition cages. Daily, the fruits of tomatoes were removed and the eggs of N elegantalis were distributed in fruits of Scarlet eggplant (on average five eggs/fruit) that remained in plastic trays, covered with non woven fabric, for pupation.
In the creation of Trichogramma galloi, eggs of Anagasta kuehniella Zeller (Lepidoptera: Pyralidae) were made unfeasible in germicidal lamp for 50 minutes and set in rectangles of blue cardstock (cartouches of 8.0 x 2.0 cm), with gum arabic at 20%. The cartouches were inserted in glass tubes (8.5 x 2.4 cm), with newly emerged adult parasitoids. Posteriorly, the tubes were sealed with plastic film of polyvinyl chloride, in order to prevent parasitoids from escaping. The cartouches were kept in the tubes for 24 h. Posteriorly, the cards were stored in clean glass tubes (9 x 3 cm) in air-conditioned room with temperature of 25 ± 1ºC, 70 ± 10% RH and 14h of photophase.

Thermal requirements and life table of Trichogramma galloi in eggs of Neoleucinodes elegantalis
The eggs of N. elegantalis were grouped into 10 eggs per female Trichogramma galloi. Three females T. galloi were used by repetition. The eggs of N. elegantalis were exposed to parasitism for 5 h, in order to prevent the occurrence of superparasitism. The eggs of N. elegantalis were transferred daily to blue cardstock (0.5 x 2.0 cm). These were inserted into eppendorf tubes (2 mL) along with the parasitoids (age 0 -12 h) and a honey droplet for food. The tubes were sealed with the container lid, and packed in Climatic chamber at 25 ± 1°C, 70 ± 10% RH and 14 h of photophase. After 5 h, the female parasitoids were killed with the aid of a brush; and the parasitized eggs were transferred to climate chambers at temperatures of 18, 21, 24, 27 e 30 ºC ± 1 °C, 70 ± 10% RH and 14 h of photophase. These temperatures correspond to the optimal range (24°C and 27°C) and the extreme (18, 21 e 30 ºC) for parasitoid development (Melo et al., 2007).
From the emergence of the adult T. galloi, 15 females (age 0 -6 h), from each temperature (18; 21; 24; 27 and 30 ± 1ºC), were individualized in Eppendorf tubes (2.0 mL) and returned to their respective temperatures. The cartouches of blue cardstock (0.5 x 2.0 cm) with 20 eggs of N. elegantalis (age 0 -24 h) were offered daily, until the death of female T. galloi. The cartouches with parasitized eggs, from each treatment, were packed in plastic bags (23.0 x 4.0 cm) and kept under the same conditions.
For the assessment of thermal requirements, the calculation of base temperature (bT) and thermal constant (K), were obtained by the hyperbole method (Haddad et al., 1999)

Estimated number of Trichogramma galloi to be released
The experiment was conducted in a greenhouse. The tomato seedlings were transferred for 20 Kg plastic buckets with prepared substrate in proportion to 1:1:1 (soil: sand: tanned manure). After 60 days of transplanting, tomato fruits were offered to females N. elegantalis. 200, 400, 800, 1600, 3200, 6400, 12800 and 25600 females T. galloi were released. Parasitism occurred for 24 h. Posteriorly, the fruits were taken to the laboratory, arranged in a climate chamber (25 ± 2 ºC, 70 ± 10% RH and 14 h of photophase). The experiment was repeated six times, in a completely randomized experimental design. The results were submitted to analysis of variance and regression in order to determine the optimal number of T. galloi to be released in the field. The percentage of parasitized eggs in each proportion was the evaluated parameter.

III. RESULTS AND DISCUSSION 3.1 Thermal requirements and fertility life table
The embryonic development of Trichogramma galloi in eggs of Neoleucinodes elegantalis started from the temperature 8.02 ± 0.2 °C. The heat buildup for the complete development of T. galloi was of 159.74 ± 3.88 °C degree days (DD) (Figure 1).   Table 2). The net reproductive rate (Ro), which indicates the number of times that population multiplied by generation, ranged from 11.37 to 66.58 depending on temperature, with the maximum increase of the population in the temperature of 24 ºC and lowest net reproduction rate at temperatures of 30 and 27 ºC, with 11.37 and 28.28, respectively. The infinitesimal rate of increase (rm) of T. galloi increased in the range of 18 to 24ºC (0.22 to 0.35). The finite ratio of increase (λ), which indicates the number of females T. galloi added to population by females parasitoid per day was greater at 24 ºC and smaller at 18 ºC, with 1.42 and 1.25 females / females / day, respectively.

Estimate Number of T. galloi per egg of N. elegantalis
In the analysis of the number of parasitized eggs, the behavior of T. galloi followed a quadratic function, which demonstrated a relationship between parasitism and the number of parasitoids released. The estimated 82 individuals of T. galloi per egg of N. elegantalis reached a parasitism peak of about 200 parasitized eggs (Figure 3).
The variables analyzed in the present study may present different values in other species of Trichogramma, since these are individual parameters related to adaptive capacities to various hosts and room temperature (Dias et. al Therefore, the success in pest control, with the use of the parasitoid Trichogramma, is related to the correct choice of the species to be used. This because although it is classified as a generalist parasitoid, research results show that species may have affinity for certain hosts. This affinity can occur by stimulus-driven search behavior, of the nutritional and morphological characteristics of the egg. Abiotic factors, as weather conditions, also can affect other parameters as: the duration of development, sexual rate, parasitism and adult longevity (