Effects of temperature on the immature development and emergence of five species of <Emphasis Type="Italic">Trichogramma</Emphasis> |
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Authors: | Marion R Foerster Luís A Foerster |
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Institution: | (1) Universidade Federal do Paraná, Setor Escola Técnica, Curitiba, Brazil;(2) Depto. de Zoologia, Universidade Federal do Paraná, Curitiba, Brazil |
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Abstract: | Five constant temperatures between 14 and 30°C were used to evaluate their effect on the development time and adult emergence
of five Trichogramma species found parasitizing eggs of the velvetbean caterpillar Anticarsia gemmatalis Hübner (Lepidoptera: Noctuidae) on soybeans in subtropical Southern Brazil. Host eggs were parasitized at 20°C and then transferred
to the study temperatures to follow development and emergence of parasitoids. All five species were able to develop and emerge
within the range of temperatures evaluated, and the effect of temperature on development rates could be described by linear
regression. Trichogramma acacioi Brun, Moraes & Soares and T. rojasi Nagaraja & Nagarkatti were the most cold-tolerant species, with lower threshold temperatures of 8.1 ± 0.16°C and 9.2 ± 0.16°C,
respectively. Trichogramma atopovirilia Oatman & Platner was the least cold-adapted species, with a lower threshold of 10.2 ± 0.13°C. Degree-day accumulation ranged
from 153.8 DD for T. atopovirilia to 190.7 DD for T. acacioi. Adult emergence was higher than 90% for T. atopovirilia and T. pretiosum at all temperatures, whereas T. lasallei Pinto emergence dropped to 71.3% at 14°C and to 58.3% at 26°C, both significantly lower than the emergence of T. pretiosum and T. atopovirilia. Significantly less T. acacioi adults emerged at 30°C than either T. pretiosum or T. atopovirilia. The sex-ratio was not affected within the range of temperatures studied, and varied from 0.65 to 0.88 (female/(male + female)).
Differences among Trichogramma spp. densities in the field can be attributed to slower development rates and/or reduced emergence of adults, both at low
and high temperatures.
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Keywords: | Anticarsia gemmatalis Biological control Developmental thresholds Egg parasitoids Soybeans Trichogrammatidae |
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