Effect of Some Local Plants Extracts on Control of the African Bollworm, Helicoverpa armigera (Noctuidae) in Tomatos

Abstract

These studies were conducted in White Nile State on one of the important field pests of tomato, African bollworm Helicoverpa armigera Hubner. The studies included a field survey to determine the presence and distribution of African bollworm in the White Nile State and a laboratory studies to calculate morphmetrics measurement s of insect stages , to study some biological activities of the insect and to evaluate the efficacy of leaves and stem ethanol and aqueous extracts of Lantana camara (Verbenaceae), Ocimum basilcum (Lamiaceae), Lupinus termis (Leguminaceae), Solenostemma argel (Asclepiadaceae) and Nicotiana rustica (Solanaceae). The evaluated efficacy parameters included mortality, repellency and antifeeding effects on Helicoverpa armigera larvae. The study showed that the pest was present and distributed along the state in all studied area (Elsoufi, Eltawiella and Elmogamaat) with high rate of infestation in December. The results showed that at an average temperature range of ( 27± 1.1 0C - 30 ± 2.9 0C) and relative humidity of (35.2 ± 3% - 40.7± 2.8% ), the morphometrics and the development duration of insect stages were as follows: The morphometrics study of insect stages revealed that the egg size was (0.5±0.07 and 0.44±0.04 ) mm in length and width respectively; with yellowish white colour. The 1st , 2nd , 3rd , 4th and 5th larval instars size were (1.42 ± 0± 0.1) , (4.2 ± 0.19 and 1.1± 0.2 ), (8.27 ± 0.7 and 2.3 ± 0.2 ), (10.1 ± 0.9 and 2.7 ± 0.2 ) and (17.1 ± 3.8 and 3.3 ± 0.2 ) mm in length and width respectively and they exhibited variations in colour. The pupa was 18.6 ± 1.4 and 4.9 ± 0.33 mm in length and width respectively; the colour started as green then turned brown. The adult male wing span and body length were 27.6 ± 2.1 and 16 ± 1 mm respectively , the female wing span and body length were 35.8 ± 2.3 and 19.2 ± 2.4 mm respectively, the colour ranged from grey to brown with markings on wings. The incubation period of eggs was 3.9±0.9 days. Where as the larval periods were 2.4 ± 0.5, 2.7 ± 0.8, 2.9 ± 1.1, 3.2 ± 0.9 and 3.4 ± 0.5 days for the 1st , 2ed , 3rd , 4th and 5th instars respectively. Prepupa and pupa periods were 3.1±1.2 and 9.6±1.5 days respectively. The percentage of eggs hatching, pupation and adult emergence were 66.9 ± 7.1, 74.6 ± 4.6 and 83.1 ± 5.8% respectively. During the period preoviposition ( 2.2 ± 0.44) days, oviposition (10 ± 0.4 ) days and postovipositon (3.2 ± 0.45) days, The female laid a total number of 469.4 ± 90.9 eggs. Generally ethanol extracts were more effective than aqueous extracts. The significant effects on mortality were observed after 72 hours, the effects were dose and time dependent. The LC50 of Lantana camara was 2.76 followed by solenostemma argel 6.35 , Ocimum basilicum 16.19 , Lupinus termis 17.05 and Nicotiana rustica 50 . The different extracts induced significant feeding ratio (FR) except L.termis and the effects were dose dependent. The lowest (FR) 0.0054 was caused by Ocimum basilicum followed by Lantana camara 0.0084, Solenostemma argel 0.012 and 0.013 for both Nicotiana rustica and Lupinus termis, while the Dimethoate and the control showed (FR) of 0.0148 and 0.019 respectively. The highest percent repellence was shown in the first hour post application and caused by Ocimum basilicum 66.7% followed by Lantana camara 33.3%, Nicotiana rustica 0%, Lupinus termis -13.4% while solenostemma argel -26.%, and the effects were decreased by increasing the time. The Preliminary phytochemical screeningof Lantana camara, solenostemma argel and Ocimum basilicum indicated the presence of alkaloids, sterols, triterpenes ,flavonoids, tannins and saponins compounds in addition to the presence of cyanogenic glycosides in S,argel .