INSECTICIDAL ACTIVITY OF EXTRACTS FROM SCROPHULARIA CANINA L. AGAINST ADULT SITOPHILUS GRANARIUS (L.) (COLEOPTERA, CURCULIONIDAE) In the present study the insecticidal activity of Scrophularia canina L. plant extracts towards adult Sitophilus granarius (L.) (Coleoptera, Curculionidae) was evaluated. Aerial parts of S. canina were collected during the flowering stage, dried (45° C for 5 days), powdered and sieved (≤ 1 mm Ø). Aliquots (100 g) of material obtained were immersed in a known volume (300 mL) of individual solvents with different polarities (hexane, methanol). After 24 h, mixtures were centrifuged (14000 rpm for 20 min), filtered (Whatman No. 1), dried and stored (-20° C). Toxicity tests were performed by topical application (0.5 µl) of extract solutions on pronotum of adult weevils and by ingestion providing adult S. granarius with flour disks treated with 5 µl of different extract concentrations (15.62 - 250.00 µg/µl). In the dose range tested, both extracts showed contact toxicity to S. granarius adults. The highest mortality percentages induced by the hexane extract were 65 and 80% respectively after 24 and 48 h treatment while the methanolic extract provoked a 50% mortality both after 24 and 48 h. The lowest values of 24 and 48 h LD50 were obtained for the hexane extract (75.216 and 38.924 µg/adult, respectively) and were about the half of the LD50 values calculated for the methanolic one (133.27 and 81.019 µg/adult). Flour disk bioassays showed that both extracts did not have ingestion toxicity against granary weevil adults. Nutritional indices were not significantly affected by different concentrations of the hexane extract which also showed low levels of feeding deterrence; on the contrary, nutritional indices were significant affected by some doses of methanolic extract (0.6250 and 0.3125 mg/disk) that elicited high percentages of feeding deterrence (81-83%). The results indicate that in S. canina extracts are present various compounds which are biologically active against S. granarius adults that could be isolated and identified for their use to control stored-product insect pests.
Nel presente lavoro è stata valutata l’attività insetticida di estratti di Scrophularia canina L. verso adulti di Sitophilus granarius (L.) (Coleoptera, Curculionidae). Organi epigei della pianta sono stati raccolti nel periodo della fioritura, essiccati (45°C per 5 gg), triturati e setacciati (Ø ≤ 1 mm). Aliquote (100 g) del materiale ottenuto sono state immerse in un volume noto (300 mL) di due solventi a diversa polarità (metanolo, esano). Dopo 24 h, le miscele sono state centrifugate (14000 rpm per 20 min), filtrate (Whatman N°1), portate a secco e conservate (-20°C). Saggi di tossicità sono stati condotti per contatto, applicando 0,5µl di miscela (dosi 7,81 - 125 g/adulto) sul torace degli adulti, e per ingestione, somministrando agli adulti di S. granarius dischi di farina su cui erano stati applicati 5 µl delle diverse miscele (0,0781 - 1,250 mg/dischetto). Entrambi gli estratti, alle dosi utilizzate, hanno mostrato tossicità per contatto verso gli adulti di S. granarius. La massima percentuale di mortalità osservata per l’estratto esanico è stata del 65 e 80%, rispettivamente a 24 e 48 h dal trattamento, mentre per l’estratto metanolico è stata del 50% sia a 24 che a 48 h. I valori più bassi di DL50 , dopo 24 e 48 h, sono stati osservati per l’estratto in esano (75,216 e 38,924 µg/adulto) e sono risultati circa la metà di quelli ottenuti con alcol metilico (133,27 e 81,019 µg/adulto). I saggi hanno evidenziato che entrambi gli estratti non hanno attività tossica per ingestione verso gli adulti di S. granarius. Gli indici nutrizionali non sono stati influenzati sensibilmente dalle diverse concentrazioni dell’estratto esanico cui sono corrisposti bassi livelli di deterrenza; tali parametri, invece, sono stati significativamente condizionati da alcune dosi dell’estratto alcolico (0,6250 e 0,3125 mg/disco) che hanno indotto elevate percentuali di deterrenza (81-83%). I risultati indicano che negli estratti di S. canina sono presenti interessanti sostanze a diversa attività biologica sugli adulti di S. granarius che potrebbero essere isolate e identificate per una loro applicazione nel controllo di insetti dannosi alle derrate.
Attività insetticida di estratti di Scrophularia canina L. verso adulti di Sitophilus granarius (L.) (Coleoptera, Curculionidae)
PAVENTI G;GERMINARA GS
2013-01-01
Abstract
INSECTICIDAL ACTIVITY OF EXTRACTS FROM SCROPHULARIA CANINA L. AGAINST ADULT SITOPHILUS GRANARIUS (L.) (COLEOPTERA, CURCULIONIDAE) In the present study the insecticidal activity of Scrophularia canina L. plant extracts towards adult Sitophilus granarius (L.) (Coleoptera, Curculionidae) was evaluated. Aerial parts of S. canina were collected during the flowering stage, dried (45° C for 5 days), powdered and sieved (≤ 1 mm Ø). Aliquots (100 g) of material obtained were immersed in a known volume (300 mL) of individual solvents with different polarities (hexane, methanol). After 24 h, mixtures were centrifuged (14000 rpm for 20 min), filtered (Whatman No. 1), dried and stored (-20° C). Toxicity tests were performed by topical application (0.5 µl) of extract solutions on pronotum of adult weevils and by ingestion providing adult S. granarius with flour disks treated with 5 µl of different extract concentrations (15.62 - 250.00 µg/µl). In the dose range tested, both extracts showed contact toxicity to S. granarius adults. The highest mortality percentages induced by the hexane extract were 65 and 80% respectively after 24 and 48 h treatment while the methanolic extract provoked a 50% mortality both after 24 and 48 h. The lowest values of 24 and 48 h LD50 were obtained for the hexane extract (75.216 and 38.924 µg/adult, respectively) and were about the half of the LD50 values calculated for the methanolic one (133.27 and 81.019 µg/adult). Flour disk bioassays showed that both extracts did not have ingestion toxicity against granary weevil adults. Nutritional indices were not significantly affected by different concentrations of the hexane extract which also showed low levels of feeding deterrence; on the contrary, nutritional indices were significant affected by some doses of methanolic extract (0.6250 and 0.3125 mg/disk) that elicited high percentages of feeding deterrence (81-83%). The results indicate that in S. canina extracts are present various compounds which are biologically active against S. granarius adults that could be isolated and identified for their use to control stored-product insect pests.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
