Akaricidni i subletalni efekti biopesticida na Tetranychus urticae Koch (Acari: Tetranychydae)

Abstract

Akaricidni i subletalni efekti komercijalnih preparata biopesticida na bazi oksimatrina, azadirahtina, spinosada i entomopatogene gljive Beauveria bassiana na običnu grinju-paučinara Tetranychus urticae Koch (Acari: Tetranychidae) ispitivani su u laboratorijskim biotestovima, u cilju kompletiranja profila njihove biološke aktivnosti kao osnove za definisanje održive strategije primene. Biotestovi su izvedeni na temperaturi 27±2°C i relativnoj vlažnosti 50-70% uz fotoperiod svetlo/tama 16h/8h. Biopesticidi su aplicirani prskanjem lisnih isečaka (prečnika 30 mm) ili celih primarnih listova pasulja, postavljenih adaksijalno u Petri sudove, pomoću aparata Potter Tower (2 ml tečnosti, pritisak 100 kPa, vodeni depozit 2,7 mg/cm2). Toksičnost biopesticida za životne stadijume T. urticae ocenjena je izvođenjem biotestova u kojima su jaja, juvenilni stadijumi (larve, protonimfe, ženke deutonimfe) ili odrasle preovipozicione ženke tretirane serijom simetrično raspoređenih koncentracija, a dobijeni podaci obrađeni postupkom probit-analize. Nijedan od ispitivanih biopesticida nije uzrokovao značajnu ovicidnost, već je akaricidni efekat nastao usled rezidualnog delovanja biopesticida na larve ispiljene iz tretiranih jaja. U svim biotestovima direktno tretirane larve bile su najosetljiviji životni stadijum. Direktno tretiranje preovipozicionih ženki preparatima na bazi azadirahtina i B. bassiana uzrokovaloje RO-efekat („run-off“-efekat: napuštanje tretirane površine) kao dominantan u odnosu na smrtnost. Vrednosti LC90 za preparat na bazi oksimatrina bile su znatno niže od koncentracije preporučene za primenu (2 ml/l), dok su kod spinosada bile više od preporučenih koncentracija (60-300 mg/l). Vrednosti LC90 za azadirahtin bile su niže a vrednosti EC90 za RO-efekat ovog biopesticida viša od preporučene koncentracije (50 mg/l a.m.). U biotestovima sa preparatom na bazi B. bassiana sve LC/EC90 vrednosti (osim za LC90 za larve) bile su više od preporučene koncentracije (3 ml/l). Repelentnost i ovipoziciona deterentnost biopesticida ocenjena je izvođenjem biotesta sa mogućnošću izbora u kojem su preovipozicione ženke postavljane na centralni nerv lista čija je samo jedna polovina tretirana; broj ženki i broj položenih jaja utvrđivani su posebno na tretiranoj i netretiranoj polovini lista posle 24, 48 i 72 h. Značajne repelentne i deterentne efekte (posle 24 h i kumulativno za ceo period) uzrokovale su serije koncentracija preparata na bazi oksimatrina (0,5-2 ml/l), azadirahtina (1,56-50 mg/l a.m.) i B. bassiana (0,82-7 ml/l). Efekti biopesticida na životne parametre i populacioni rast T. urticae ocenjeni su izvođenjem dve varijante biotesta u kojima su ženke koje su preživele tretiranje u stadijumu jajeta starosti do 24 h i izloženost reziduama tokom juvenilnog razvića (prva varijanta) ili preovipozicionom periodu (druga varijanta) prebačene na netretiranu površinu na kojoj su tokom perioda od sedam dana dnevno utvrđivani broj položenih jaja i broj živih ženki.Preparat na bazi oksimatrina (0,025-0,1ml/l) značajno je redukovao fekunditet, dužinu života ženki i trenutnu stopu rasta (ri), posebno u drugoj varijanti gde je zabeležena negativna rivrednost. Značajna redukcija ovih parametara zabeležena je i u biotestovima sa preparatima azadirahtina (prva varijanta: 3,75-15 mg/l a.m; druga varijanta: 17,5-70 mg/l a.m.), spinosada (60-240 mg/l a.m.) i B. bassiana (1,5-6 ml/l). Efekti biopesticida na prirodnu stopu rasta (rm) i druge demografske parametre T. urticae ocenjeni su formiranjem tabela života sa podacima o uzrasno-specifičnim stopama preživljavanja i fertiliteta (produkciji ženkog potomstva) ženki preživelih tretiranje u stadijumu jajeta starosti do 24 h (prva varijanta) ili preovipozicionom periodu (druga varijanta). Demografski biotestovi sa preparatima oksimatrina (0,05 ml/l), azadirahtina (prva varijanta: 7,5 mg/l a.m; druga varijanta: 35 mg/l a.m.) pokazali su da ovi biopesticidi redukuju populacioni rast redukujući fertilitet i stope preživljavanja, ali i usporavajući juvenilno razviće jedinki ispiljenih iz tretiranih jaja. Značajna redukcija demografskih parametara zabeležena je i u obe varijante biotesta sa preparatom na bazi B. bassiana (3 ml/l). Preparat spinosada (120 mg/l a.m.) takođe je značajno redukovao demografske parametre nakon tretiranja u preovipozicionom periodu, dok je tretiranje u stadijumu jajeta povećalo rm vrednost preživelih jedinki, zahvaljujući većem fertilitetu na početku perioda reprodukcije tretiranih ženki. Dobijeni rezultati razmatrani su u kontekstu populacione strukture i dinamike T. urticae kao kolonizirajuće vrste i heterogene distribucije aktivne materije u uslovima praktične primene.

Acaricide and sublethal effects of several commercial biopesticide products based on oxymatrine, azadirachtin, spinosad and the entomopathogenic fungus Beauveria bassiana on the two-spotted spider mite Tetranychus urticae Koch (Acari: Tetranychidae) were examined in laboratory bioassays in order to round off a profile of their biological activity as a basis for defining a sustainable application strategy. Bioassays were performed at 27±2°C temperature, 50-70% relative humidity and 16h/8h light/dark photoperiod. The biopesticides were sprayed on bean leaf discs (30 mm in diameter) or intact leaves positioned adaxially in Petri dishes using a Potter Tower device (2 ml liquid, 100 kPa pressure, 2.7 mg/cm2 water deposit). Toxicity of the biopesticides to different stages of T. urticae mites was assessed in bioassays in which eggs, juvenile stages (larvae, protonymphs, female deutonymphs) or adult preovipositing females were treated with a series of symmetrical concentrations, and the data were processed by probit analysis. None of the investigated biopesticides caused a significant ovicide effect, while acaricide effects resulted from their residual effects on larvae hatched from the treated eggs. In all bioassays, directly treated larvae were found the most sensitive life stage. Direct treatment of preovipositing females with azadirachtin and B. bassiana products caused a run-off effect which was dominant compared to mortality. The LC90 values of the oxymatrine product were significantly lower than its recommended concentration (2 ml/l), while those of spinosad were higher than the recommended concentration (60-300 mg/l). Azadirachtin LC90 values were lower and those of its RO-effect higher than the recommended concentration (50 mg/l a.i.). In B. bassiana bioassays, all LC/EC90 values (except LC90 for larvae) were higher than the recommended concentration (3 ml/l). Repellence and ovipositional deterrence of the biopesticides were assessed in bioassays in which preovipositing females were offered a choice by releasing them onto the central nerve dividing each leaf into a treated and untreated half; and the number of females and eggs were counted on each half after 24, 48 and 72 h. Significant repellent and deterrent effects (after 24 h and cumulative over the entire period) were caused by oxymatrine (0.5-2 ml/l), azadirachtin (1.56-50 mg/l a.i.) and B. bassiana (0.82-7 ml/l) concentration series. Biopesticide effects on the life-table parameters and population growth of T. urticae were evaluated by conducting two variants of bioassay in which females that survived treatment at the 24h-old egg stage and were exposed to residues over their entire juvenile development (first variant) or during preovipositing period (second variant) were transferred to untreated surface on which the number of eggs they laid and live females were counted daily for seven days. The oxymatrine product (0.025-0.1ml/l) significantly reduced fecundity, life span and instantaneous rate of increase (ri), particularly in the second variant, in which a negative ri was found. Significant reduction in these parameters was also detected in bioassays testing azadirachtin (first variant: 3.75-15 mg/l a.i; second variant: 17.5-70 mg/l a.i.), spinosad (60-240 mg/l a.i.) and B. bassiana (1.5-6 ml/l). The effects of the biopesticides on intrinsic rate of increase (rm) and other demographic parameters of T. urticae were assessed by constructing life-tables that included age-specific survival and fertility rates (female offspring production) of females that survived treatment at the egg stage of up to 24 h (first variant) or during preoviposition (second variant). Demographic bioassays with oxymatrine (0.05 ml/l) and azadirachtin (first variant: 7.5 mg/l a.i; second variant: 35 mg/l a.i.) showed that these two biopesticides reduced population growth by suppressing fertility and survival rates, but also by slowing down the juvenile development of mites hatched from treated eggs. Both bioassay variants testing B. bassiana (3 ml/l) also showed significant reductions in demographic parameters. Spinosad (120 mg/l a.i.) also significantly reduced those parameters after treatment at the preovipositing period, while treatment at the egg stage increased the rm values of the surviving mites, owing to the higher fertility of treated females at the beginning of reproduction. The results were discussed in terms of population structure and dynamic of T. urticae as a colonizing species and the heterogenous distribution of active ingredients under practical conditions.