Vol.12_No.2 - Pesticide Alternatives Lab - Michigan State University

Spring 2003 Resistant Pest Management Newsletter Vol. 12, No.2mahua oil (Madhuca indica), PSKE, pungum oil(Pomgamia pinata), neem oil, azadirachtin, and NSKE.The maximum resurgence was observed with mahuaoil, and the maximum negative resurgence wasobserved with dicofol (18.5 E.C.) in both sprays.Botanical pesticides had some resurgence but could beused as safe pesticides on vegetables, while also beingecologically friendly.KEY WORDS: Resurgence, spider mite, acaricides,botanical pesticides.INTRODUCTION In recent years spider mite, Tetranychusludeni Zacher, has been observed as a serious pest tovegetable crops, especially on cowpea, a commonvegetable of summer months in India. This hasattracted the attention of growers and acarologists inIndia's Varanasi region. Heavy populations of mitesand their profuse webs cover the plants. The regularmonoculture of cowpea without crop rotation hasaggravated the problem. It has been reported thatregular use of dimethoate (Singh et.al 1989) has alsoresulted in outbreaks of this mite. It had been earlierreported that phosphamidon, fluvalinate, fenvalerate,and dimethoate showed resurgence of this mite (Kumarand Singh, 1999). For the economic harvest of thecowpea crop, the current effective treatment is to useacaricides that can manage this mite pest.MATERALS and METHODS Field experiments wereconducted to find out the resurgence of this mite pestagainst some acaricides and botanical pesticides at theirrecommended doses on cowpea crops. The trials werereplicated four times at vegetable grower fields duringsummer months in RBD. The plot size was 3x5m androw-to-row spacing was maintained at 50 cm apart.Twelve formulations of acaricides and botanicalpesticides were taken in this trial (Tables 1 and 2). Thecontrol was treated with water + sandovit spray. Theamount of proprietary ingredient required wascalculated by using the following formula:The observations were taken from five randomlyselected tagged and numbered plants from each plot.Five leaves were plucked from the upper, middle, andlower portions of each plant and a total number oftwenty-five leaves were collected from each plot forobservation. The mite population was counted on thebasis of 2cm squared leaf areas at four spots per leaf.The mortality of spider mite was observed in differentintervals at pre-spray and at 1, 3, 7, and 14 days after.The fourteenth day observation of the first spray wastreated as the pre-spray observation of the 2nd spray,with the rest of the observations taken similarly. Thepercent mortality was calculated by using followingformula:The corrected percent mortality was calculated throughAbbot's formula (1925), which is as follows:Where:P = percent corrected mortality,P1 = percent observed mortalityC = percent mortality in control.The percent resurgence of mite population wascalculated by Henderson and Tilton's formula asfollows:Where:Ts = Number of live mite in posttreatment countTF = Number of live mite in pretreatment countCs = Number of mite in untreatedcheck (Post-treatment)CF = Number of mite in untreatedcheck (Pre-treatment)RESULTS and DISCUSSION The results indicate that somebotanical pesticides showed maximum positiveresurgence viz. mahua oil (+ 38.68 %), neem oil (+12.26 %), PSKE (+ 10.36 %), NSKE (+ 5.22 %), andpongamia oil (+ 4.68 %) (Table 1). Some acaricidesviz. sulphure (+ 6.22 %), ethion (+ 3.72 %), andbotanical pesticides i.e. azadirachtin (+ 4.66 %) hadencouraging performances but showed someresurgence, whereas resurgence was not noticed withdicofol 18.5% EC (- 26.28 %), dicofol 5 % WP (-14.22 %), abamectin (- 12.22 %), and phosalone (-10.68 %) in the first spray (Table 1). In the secondspray, the trend of maximum resurgence of somebotanical pesticides was changed, including mahua oil(+ 88.64 %), pongamia oil (+ 32.66 %), P.S.K.E. (+25.00 %), neem oil (+ 18.43 %), azadirachtin (+ 14.09%), and NSKE (+ 8.32 %) (Kumar & Singh (1998) andRai et al. (1993) supported these findings). There wasno observed change in the trend of the encouragingperformance of acaricides viz., sulphur (+ 8.32 %), andethion (+ 7.99 %) (Table 2). The same trend wasfollowed in the second spray. No resurgence wasshown with some acaricides like dicofol 18.5%EC (-74.30 %), dicofol 5% WP (- 21.65 %), abamectin (-18.02 %), and phosalone (- 12.75 %) (Table 2).Zhang and Sanderson (1990) earlier reported therelative toxicity of abamectin to Phytoseiuluspersimilis Anthias-Henriot and the spider mite33