Effectiveness of azadirachtin (NeemAzal-T/S) in controlling pear psylla (Cacopsylla pyri) and European red mite (Panonychus ulmi)

Abstract

Here we present the results of field trials conducted in Serbia to evaluate the effectiveness of a neem-based product, NeemAzal-T/S (containing azadirachtin-A as its active ingredient in the form of an emulsifiable concentrate) against pear psylla (Cacopsylla pyri) and European red mite (Panonychus ulmi). Efficacy evaluation against C. pyri was carried out in a commercial pear orchard of the Williams pear cultivar, located at Borkovac (Ruma). The insecticides were applied at BBCH 09 pear growth stage, several days before the beginning of hatching of the first generation larvae. The efficacy of azadirachtin was compared to that of mineral oil, abamectin and diflubenzuron. Efficacy evaluation 18 DAT showed total termination of egg laying by C. pyri after treatments with azadirachtin and abamectin, while some new (white) eggs were found after treatment with mineral oil. Diflubenzuron treatment failed to fully stop egg laying, but the number of white eggs was significantly lower than it was in the control. Azadirachtin and abamectin achieved 100% efficacy, while the effectiveness of mineral oil was 97.4%, and that of diflubenzuron a mere 59%. All four insecticides significantly reduced the number of older (yellow) eggs and larvae, the efficacy being 80.5-92.6% (yellow eggs), 69.8-79.3% (larvae I-III instar) and 94.3-100% (larvae IV-V instar). In evaluation 38 DAT, azadirachtin, abamectin and mineral oil achieved 100% efficacy against white and yellow eggs, while diflubenzuron achieved 93% and 86.9% efficacy. All four insecticides were found to demonstrate high efficacy against I-III instar larvae (99.2-100%), but mineral oil treatment alone achieved high efficacy against IV-V instar larvae (92.4%) as well. Efficacy evaluation against P. ulmi was carried out in a commercial orchard of the Red Chief apple cultivar located at Morovic (Sid). Azadirachtin efficacy in controlling a summer population of European red mite was compared to a mineral oil, clofentezine and spirodiclofen. The acaricides were applied when the number of P. ulmi motile forms was below the orientational damage threshold of 3 motile forms per leaf. Azadirachtin reduced significantly the number of motile forms, leaving it well below damage threshold by the end of the trial. Good control efficacy was achieved (77.2-90.4%), the highest level of efficacy being recorded at the end of the trial 38 DAT. In mineral oil treatment 7 DAT, efficacy was 92.4%; 14 DAT and 21 DAT it was 75.2% and 78.9%, and it dropped to below 60% at the end of the trial. The efficacy of clofentezine (39.4-68.2%) was unsatisfactory, which is probably the result of a resistance developing under high selection pressure of these compounds in the Morovic locality in preceding years, while the newly introduced acaricide spirodiclofen showed high and long-lasting efficacy (97.2%, 38 DAT). The results of the trials are discussed in terms of improving management of the populations of European red mite and pear psylla.Prikazani su rezultati poljskih ogleda realizovanih u Srbiji u cilju ocene efektivnosti nimderivata NeemAzal-T/S (koji sadrzi azadirahtin-A kao aktivnu materiju u formi koncentrata za emulziju) u suzbijanju kruskine buve (Cacopsylla pyri) i crvene vocne grinje (Panonychus ulmi). Ogled ocene efektivnosti suzbijanja C. pyri izveden je u komercijalnom zasadu kruske sorte Viljamovka u Borkovcu (Ruma). Insekticidi su primenjeni u fenofazi BBCH 09, nekoliko dana pre pocetka piljenja larvi prve generacije. Efikasnost azadirahtina uporedjena je sa efikasnoscu mineralnog ulja, abamektina i duflubenzurona. Ocena efekata 18 DPT pokazala je da je polaganje jaja C. pyri potpuno zaustavljeno u tretmanima azadirahtinom i abamectinom, dok je u tretmanu mineralnim uljem ipak registrovan izvestan broj novih (belih) jaja. U tretmanu diflubenzuronom polaganje jaja nije zaustavljeno, ali je broj belih jaja bio znacajno nizi u poredjenju sa kontrolom. Efikasnost azadirahtina i abamektina iznosila je 100% a efikasnost mineralnog ulja 97,4%, dok je efikasnost diflubenzurona bila svega 59%. Sva cetiri insekticida znacajno su redukovala broj starijih, zutih jaja i larvi, a efikasnost je iznosila 80,5-92,6% (zuta jaja), 69,8-79,3% (larve I-III stupnja) i 94,3-100% (larve IV-V stupnja). U oceni 38 DPT u tretmanima azadirahtinom, abamektinom i mineralnim uljem zabelezena je 100% efikasnost redukcije broja belih i zutih jaja, dok je diflubenzuron ostvario efikasnost od 93% i 86,9%. Sva cetiri insekticida ispoljila su visoku efikasnost u suzbijanju larvi I-III stupnja (99,2- 100%), ali je samo u tretmanu mineralnim uljem zabelezena visoka efikasnost i protiv larvi IV-V instar stupnja (92,4%). Ogled ocene efektivnosti suzbijanja P. ulmi izveden je u komercijalnom zasadu jabuke sorte Red Chief u Morovicu (Sid). Efikasnost azadirahtina u suzbijanju letnje populacije crvene vocne grinje uporedjena je sa efikasnoscu mineralnog ulja, klofentezina i spirodiklofena. Akaricidi su primenjeni u vreme kad je brojnost P. ulmi bila ispod orijentacionog praga stetnosti od 3 pokretne forme po listu. Azadirahtin je znacajno redukovao broj pokretnih formi, koji je do kraja ogleda ostao znatno ispod praga stetnosti. Postignuta je dobra efikasnost suzbijanja (77,2-90,4%), s tim da je najvisi nivo efikasnosti registrovan na kraju ogleda, 38 DPT. U tretmanu mineralnim uljem, 7 DPT ostvarena je efikasnost 92,4%; 14 DPT and 21 DPT efikasnost je bila 75,2% i 78,9%, da bi na kraju ogleda pala ispod 60%. Efikasnost klofentezina (39,4-68,2%) bila je nezadovoljavajuca, sto je verovanto rezultat rezistentnosti nastale pod snaznim selekcionim pritiskom ovim akaricidom prethodnih godina, dok je efikasnost novog akaricida spirodiklofena bila visoka i dugotrajna (97,2%, 38 DPT). Ostvareni rezultati razmatrani su u kontekstu unapredjenja suzbijanja populacija ove dve stetne vrste.