AFPP-SEVENTH INTERNATIONAL CONFERENCE ON PESTS IN AGRICULTURE, MONTPELLIER, FRANCE 26TH-27TH OCTOBER, 2005. COMPARATIVE EVALUATION OF THE EFFICACY OF THREE BOTANICAL AND SYNTHETIC INSECTICIDES AGAINST THE SPIRALING WHITEFLY, Aleurodicus dispersus Russell ON PEPPERS. M.M.DEGRI*; T.LIBNA** &H.B.K.JOSEPH* *Pest Control Unit, Gombe State ADP, PMB 0046 Gombe, Gombe State, Nigeria. **School of Agriculture,ATBU PMB 0248 Bauchi, Nigeria Abstract Field experiments were conducted at the Dadin-Kowa irrigation dam during 2003- 2004 dry seasons to compare the effectiveness of neem seed oil, tobacco leaf garlic bulb and imidacloprid (Confidor) insecticides in the control of spiraling whitefly, Aleurodicus dispersus Russell on peppers (Capsicum spp.).The treatments were replicated four times in a randomized complete block design. The botanical and synthetic insecticides application was done at 7days intervals and at 10% and 0.5 ml/litre of water, respectively.Results of the study showed that all the three botanicals were as effective as the synthetic insecticide in controlling the pest in the field.Confidor significantly ( P< 0.05) reduced the infestation of spiraling whitefly than the three botanical insecticides. However neem oil, garlic and tobacco sprayed peppers had significantly (P< 0.005) lower infestations and improved the fruit yields than control treatment. Neem oil, garlic and tobacco extracts are therefore recommended for controlling A.dispersus on peppers. Keywords: botanical, synthetic, insecticide, spiraling, whitefly, pepper INTRODUCTION Aleurodicus dispersus Russell (Homoptera:Aleyrodidae) is a highly polyphagous pest. It is known to attack many host plants like vegetables, fruits, ornamentals, shade trees (DAVID &REGU,1995;SRINIVASA,2000; GEETHA &SWAMIAPPA,2001).The major host plants of economic importance in Nigeria are banana,guava,pawpaw tomato,peppers, eggplant,mango,cassava, cowpea, potatoes and amaranthus (NEUENSCHWANDER,1994;PITAN et al. 2002).The pest feed on the plant by piercing through their needle-like mouthparts and sucking of sap from leaves mainly by the nymphs and adults and when population is high can cause premature leaf drop, reduce plant vigor and yields but rarely cause death of the plant (PITAN et al.2002). PITMAN & OLUFEMI (2003) reported that about 40-60 adults can be found per leaf and 50-70 % of the total number of leaves per plant can be infested depending on the plant species. The sticky liquid called honeydew excreted by the adults and nymphs on the lower leaf surfaces encourages the development of other organisms like sooty mould fungi on leaf surfaces which interferes with photosynthetic capacity and market value of the crop (AKINLOSOTU et al.1993).The copious white, waxy, flocculent material secreted by all the stages of spiraling whitefly are readily spread by wind, creating nuisance to human and animals (RAMANI et al.2002). GEETHA,(2000) reported that heavy incidence of the pest caused yield reduction to an extent of 53.10 % in tapioca. WEN et al.;(1995) reported a loss in fruit yield of 80 % in guava attacked by the pest for four months consecutively in Taiwan. Yield losses of 20-100 % can occur depending upon the crop, season and prevalence of the pest among other factors (RONALD et al.; 2003) The control of spiraling whitefly was reported in several countries using insecticides (WIJESEKERA &KUDAGAMAGE, 1990; WEN et al. 1995; ALAM et al.1998) but broad spectrum insecticides are not recommended because of their harmful effects on natural enemies (RONALD et al.; 2002).In India, tobacco, neem oil, fish oil, rosin soap and detergent solution in addition to several insecticides have been found effective (RANJITH et al.1996; MARIAM, 1999 & GEETHA, 2000). Chemical control is both uneconomic and impractical because of the pest’s wide host range, widespread distribution and presence in areas with high human and animal inhabitation (KAJITA et al.(1991).Sprayed dilute aqueous solution of detergent to reduce infestations and use of light traps covered with Vaseline coating to trap adults have been effective (MARIAM,1999). As spiraling whitefly is an exotic pest in most countries, biological control through introduction of natural enemies from the area of origin of the pest is considered the best method for a sustainable control (LOPEZ et al.1997).The introduction of aphelinid parasitoids Encarsia spp.into many countries like India, Taiwan, Nigeria, Benin, Hawaii, Maldives, Togo, Ghana, Malaysia, and the Philippines have shown that there has been a perceptible reduction in the population of the pest (NEUENSCHWANDER,1996,D’ALMEIDA et al.1998). This study tried to evaluate the efficacy of botanical insecticides in comparison with a synthetic insecticide imidacloprid in controlling A.dispersus on pepper. MATERIALS AND METHODS Field experiments were conducted at the Dadin-kowa irrigation dam during 2003 and 2004 dry seasons. Neem (Azadirachta indica A.Juss) seed oil, tobacco (Nicotiana tabacum L.), garlic (Allium sativum L.) bulb and imidacloprid (Confidor) were used. Five treatments were demarcated in a randomized complete block design replicated four times. Each plot was 4.5 m long by 3.0 m wide with 1.5 m interspaces between adjacent plots of replication. Clean seeds of pepper were purchased from Gombe State Agricultural Supply Company and planted in nursery for four weeks prior to transplanting. The seedlings were transplanted during cool evening in the prepared fields at a plant spacing of 60 cm by 50 cm.After transplanting, the plants were irrigated twice daily and gap filling was done one week after transplanting to maintain the plant population in the experimental plots. Fresh garlic bulbs and tobacco leaves were obtained; sun dried and milled to powder with blender.400 g of each product powder was boiled separately in 20 litres of water to obtain a paste. The paste were allowed to stay for 12 hours and filtered through double fold muslin cloth to obtain extract. The fresh seeds of neem were collected from neem trees, sun dried, decorticated; sun dried the kernel, milled to powder by using blender. 400 g of the powder was mixed with 20 litres of hot water to form paste. Oil extraction was done by pressing and squeezing the paste put in a muslin cloth to bring out the oil. The extracted oil and supernatant from the various plant products were left for one hour to cool and were put separately in 4 litre gallons. The neem oil, garlic, tobacco extracts and imidacloprid were carefully sprayed to cover the underside and surface of the crops using knapsack sprayer. After the application of each product, the sprayer was washed thoroughly with clean water before introducing the next product in the sprayer. The botanical insecticides were sprayed at 10 % concentration while imidacloprid at 0.5 ml/l of water at 7 days interval. The first application was done as soon as the pest was sighted on some few crops. Assessment of the products was done by visually counting the number of infested plant/plot and the number of leaves with spiraling whitefly from randomly tagged plants. Harvested fruits were weighed and recorded. Data collected from infested plants, leaves and fruits were subjected analysis of variance (ANOVA) and their means were compared and separated. RESULTS AND DISCUSSION The infestation of peppers by A.dispersus was low in imidacloprid, A.indica, A.sativum and N.tabacum and high in the untreated control treatments for the two years (Table 1 ). The three botanical insecticides have been found to be effective against the pest but were not as effective as the synthetic insecticide used in the experiment. There was significant difference (P< 0.05) between imidacloprid and the three botanical insecticides. The low number of pepper plants and leaves infested by A.dispersus in imidacloprid was due to its capability to protect the plant from the pest. And this could be because imidacloprid is a systemic insecticide with a very good contact and stomach poison effects when used as foliar spray on the plants. The three botanical insecticides also protected the pepper plants from the pest when compared with the untreated treatments. This could be because neem, garlic and tobacco have insecticidal properties which serve as antifeedant, repellant and also disrupt the insect moulting by antagonizing ecdysone processes (STOLL, 1996). In the control treatment, there was steady increase in the population of the pest instead of decrease. This was because there was nothing to disrupt the breeding and feeding activities of the pest (RANJITH et al.; 1996 & MURALIKRISHNA, 1999). Table 2 showed that imidacloprid was significantly (P<0.05%) more effective than the botanical insecticides in controlling the pest on pepper. The number of pepper leaves infested in 2003 and 2004 were low in imidacloprid treatment, moderate in A.indica,A.sativum and N.tabacum and high in untreated treatments. The superioty and effectiveness of synthetic insecticides like the one exhibited by imidacloprid over the three botanical insecticides were reported by MARIAM(1999) and GEETHA(2000). Figure 3:Effect of botanicals and Confidor on fruit yields/ha in 2003-2004 D 30 25 20 2003 15 (t/ha) 2004 10 5 MEAN FRUITYIEL MEAN 0 A. indica A. sativum Control Treatment Table 3 indicated that imidacloprid, A.indica, A.sativum and N.tabacum treatments produced better fruit yields in 2003 and 2004 than the untreated treatment.Imidacloprid treatment fruit yield was significantly (P<0.05) higher than the fruit yields obtained from the three botanical insecticides. The mean pepper fruit yields obtained from the three botanical insecticides. This conformed with the report given by ALAM, et al.,(1998),WIJESEKERA & KUDAGAMAGE(1990). The significant higher mean fruit yields obtained from imidacloprid, A.indica, A.sativum and N.tabacum was because they prevented A.dispersus from feeding which would have caused reduction in photosynthetic activity, premature leaf drop and weakening of the pepper plants (PITMAN &OLUFEMI, 2003).