Abstract
This paper examines some biological aspects and the predatory capacity of Chrysoperla externa fed nymphs of Sipha flava and reared at different temperatures. Recently hatched larvae were placed individually in Petri dishes, fed ad libitum with S. flava and reared at either 12, 16, 20, 24, 28 or 32 ± 1°C, a RH of 70 ± 10% and a 12-h photophase. The experiment was fully randomized with 30 replicates of each treatment. The duration and survival in each instar, and larval and pupal stages (pre-pupa + pupa) were analyzed. To determine the predatory capacity of larvae they were each provided daily with three-day-old nymphs of the aphid, in a number greater than they could consume. Ninety C. externa larvae were kept individually in Petri dishes at 24 ± 1°C, and their daily consumption recorded during development. Temperature influenced the rate of larval and pupal development. There was a decrease in the duration of development with increase in temperature. Regression analyses, based on quadratic equations, were used to describe the effect of temperature on the duration of development in the different instars of C. externa. This revealed that the base temperature increased as the larvae developed towards the adult phase. The survival of larvae in the first and second instars was similar at 12, 16, 20, 24, 28 and 32°C but none of the third instar larvae completed their development at 12°C and 32°C. The average daily and total consumption of aphids by third instar larvae was about 48 times greater than that of first instar larvae. The larvae ate an average of 10, 37 and 479 aphids in the first, second and third instars, respectively.
Highlights
Many species of aphids are serious pests of various crops, among them Sipha flava (Forbes) (Hemiptera: Aphididae), known as the “pulgão-amarelo” in Portuguese and yellow sugarcane aphid in English
C. externa larvae that had recently hatched from eggs laid by adults from a culture that had been maintained in the laboratory for several generations were individually placed in 5-cm diameter Petri dishes containing a piece of a blade of elephant grass, Pennissetum purpureum Schum, placed on a layer of Agar (1%) and covered with filter paper that had been perforated with a pin for aeration
Cardoso & Lazzari (2003), studying the development of the larvae of this lacewing from the region of Curitiba in the southern state of Paraná, fed on Cinara spp. (Hemiptera: Aphididae), record an average larval duration of 59.5 days at 15°C, twice the duration recorded in the present study at nearly the same temperature (16°C and 29.4 days on average)
Summary
Many species of aphids are serious pests of various crops, among them Sipha flava (Forbes) (Hemiptera: Aphididae), known as the “pulgão-amarelo” in Portuguese and yellow sugarcane aphid in English. In addition to sugarcane it is recorded from a number of cereal crops (Blackman & Eastop, 2000) and other grasses (MedinaGaud et al, 1965; Kindler & Dalrymple, 1999; Blackman & Eastop, 2000). It mainly attacks the leaves (Holman, 1974), where the damage is shown by red spots (Webster, 1990; Costa-Arbulú et al, 2001). Because S. flava it is an emerging pest, in greenhouses, more research is needed to reduce the losses caused by this aphid. In Brazil, one of the most-studied species is Chrysoperla externa (Hagen), because of its widespread occurrence on various crops and its ability to feed on a wide range of prey species
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