Temperatura no potencial de Aphidius platensis (Brèthes) (Hymenoptera: Braconidae, Aphidiinae) para o controle biológico de Melanaphis sorghi (Theobald) (Hemiptera: Aphididae)

Abstract

Melanaphis sorghi (Theobald) is an invasive species in the American continent, reported for the first time in 2019 in Brazil, causing great loss in the sorghum culture. The survey of natural enemies can be helpful to establish a more efficient integrated management of this pest. The potential of aphid parasitoids (Braconidae: Aphidiinae) as natural enemies tend to be more affected at higher temperatures than the population growth potential of its aphid hosts. The objective of this research was to evaluate the occurrence of parasitoids that use M. sorghi as host and study the potential of these as natural enemies of the aphid in different temperatures. In the surveys carried out in the cities of Uberlândia and Sete Lagoas, Minas Gerais, Brazil, during 2021, the primary parasitoid Aphidius platensis (Brèthes) (Hymenoptera: Braconidae, Aphidiinae), a previously introduced species, was found emerging from mummies of M. sorghi. The potential of this species to the biological control of M. sorghi was evaluated comparing the biological characteristics and fertility life table parameters of the parasitoid with those of the aphid at temperatures in (23°C) and above (29°C) the optimal range for the development of the parasitoid. The tests were performed in Petri dishes (5 cm) containing leaf discs of sorghum, in B.O.D. (Bio-oxygen demand) climatic chambers. The temperatures influenced the potential of A. platensis as an natural enemy, resulting in higher values of emergence (74,9±4,54%), potential fecundity (120,2±5,41 eggs per female), estimated total fecundity (363,2±16,34 eggs per female) and longevity (10,72±0,51 days) at 23±1°C when compared with 29±1°C (respectively, 57,2±5,47%, 95,9±7,28 eggs, 289,9±21,99 eggs and 2,55±0,20 days), showing that its development was favored in the lower evaluated temperature. Despite a higher liquid reproductive rate (Ro) at 23±1°C (96,4±4,33) compared with 29±1°C (58,8±4,46), A. platensis didn’t show difference for the rate of population increase (rm) in these two temperatures (0,30±0,006 and 0,29±0,006, respectively). The aphid M. sorghi developed well in both temperatures, but had a greater rm at 29±1°C (0,54±0,01) than at 23±1°C (0,41±0,01). Aphidius platensis was the only parasitoid species found parasitizing M. sorghi and had lower values of rm than its host in both evaluated temperatures, which suggests that it has a lower growth potential and may not regulate the population of this pest in field conditions.