Abstract
Host stage preference, functional response and, mutual interference ofPraon volucre(Haliday) (Hym.: Braconidae) parasitizing the grain aphid,Sitobion avenae(Fabricius) (Hem.: Aphididae), were investigated under laboratory conditions. Host stage preference was evaluated at25±1°C,60±5% relative humidity and a photoperiod of 16:8 h (L : D), under choice and no-choice tests. Functional response was done under five constant temperatures (10, 15, 20, 25, and 30°C),60±5% relative humidity and a photoperiod of 16:8 h. (L : D).Praon volucreparasitized all nymphal instars and adults of the grain aphid but strongly preferred to oviposit into second-instar nymphs in both choice and no-choice conditions. Results of logistic regression revealed a type II functional response for all temperatures tested. The handling time (Th) and searching efficiency (a) were estimated using the Rogers equation. The maximum estimate of searching efficiency occurred at 15°C and 20°C (both0.05±0.01 h-1) and decreased to0.01±0.01 h-1at30±1°C. The minimum estimate of handling time was1.02±0.11 h at 25°C and increased to5.31±0.82 h at30±1°C. The maximum rate of parasitism was 23.52 aphids/female/day at 25°C. With parasitoid density increasing from 1 to 8, the per capita searching efficiency decreased from 0.12 h-1to 0.06 h-1. The results suggested thatP. voluvrehas the potential to be a biocontrol agent ofS. avenae. However, evaluation of foraging behavior warrants further investigation under field conditions.
Highlights
The grain aphid, Sitobion avenae (Fabricius), is a cosmopolitan species [1]
Parasitoids are important in biological control of cereal aphids [4], and several attempts have been made in introduction [5] and augmentative release of cereal aphid parasitoids
The colony of aphid parasitoid was reared on S. avenae colonies for 3-4 generations before the parasitoids were used in the experiments
Summary
The grain aphid, Sitobion avenae (Fabricius), is a cosmopolitan species [1]. This aphid causes direct damage by sucking plant sap and indirect damage by either excretion of honeydew or the transmission of viruses. It is found on many different species of Poaceae [2]. Parasitoids are important in biological control of cereal aphids [4], and several attempts have been made in introduction [5] and augmentative release of cereal aphid parasitoids [6]. Parasitoids are considered to be especially important in suppressing aphid populations earlier in the season because their appearances precede those of predators [7]
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