Abstract
The possibility of storing natural enemies at low temperatures is important for the mass production of biological control agents. We evaluated the effect of different periods of cold storage on immature mortality, mummy body mass, lifespan, reproduction and flight capacity of the parasitoid Praon volucre (Haliday). One-day-old mummies of the aphid Macrosiphum euphorbiae (Thomas) containing pre-pupae of P. volucre were stored in a climatic chamber at 5°C and 70 ± 10% RH in the dark for different periods of time (5, 10, 15 and 20 days). The control consisted of mummies kept at 22 ± 1°C, 70 ± 10% RH and a 12 h photophase. Percentage adult emergence, mummy body mass, flight capacity and number of eggs in the ovarioles of P. volucre females decreased with increase in the period of storage, while the longevity of females was only slightly affected. Fat content of mummies, percentage of parasitized aphids and survival of progeny to emergence decreased with increase in the period of storage. Storage of P. volucre pre-pupae for up to 5 days at 5°C did not affect any of the above mentioned parameters. The fact that P. volucre pre-pupae can be stored for 5 days without loss of quality and for 10 days with only a slight loss facilitates the planning of mass production and shipment.
Highlights
Insect storage at low temperatures can be an important and valuable tool in the mass production of entomophagous biological control agents
The longer the mummies of P. volucre were stored at 5°C the fewer adults that emerged ( 2 = 143.72; df = 4; P < 0.0001) and those that did were of a lower quality
An increase in storage period led to a linear decrease in mass loss (F = 3.80; df = 3; P = 0.0314) (Fig. 2) and a linear decrease in fat content (F = 5.18; df = 4; P = 0.0050) (Fig. 3)
Summary
Insect storage at low temperatures can be an important and valuable tool in the mass production of entomophagous biological control agents (van Lenteren & Tommasini, 2003). Low temperature storage allows greater flexibility in the production and shipment, and facilitates the synchronization of the production in the laboratory with the timing of release in the field (Leopold, 1998; Colinet & Boivin, 2011). Most studies show that the optimum temperature for storage of parasitoids is between 0° and 7°C (e.g. Hofsvang & Hågvar, 1977; Singh & Srivastava, 1988; Rodrigues et al, 2003; Colinet et al, 2006, 2007). Storage at low temperatures seems an attractive option, the results are often disappointing (van Lenteren & Tommasini, 2003). Low temperature storage can directly influence important biological parameters of insects (Denlinger & Lee, 1998). In the specific case of aphid parasitoids, prolonged storage at low temperatures are associated with poor immature survival
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