Combinations of several insecticides used for integrated control of Colorado potato beetle (Leptinotarsa decemlineata, Say., Coleoptera: Chrysomelidae)

Abstract

The Colorado potato beetle (Leptinotarsa decemlineata Say.) (CPB) is the main potato pest in Croatia. The main problems in CPB control are related to a number of treatments and resistance development. In order to investigate the efficacy of combinations a reduced dose of spinosad (33% of the full doses) with the reduced doses (33% of full doses) of B.t.t., neem and pyrethrin against CPB larvae, 3-year field trials and one laboratory trial were conducted. Joint actions of the insecticides in combinations were analyzed. The CPB attack on experimental fields in all 3 years of investigation was high to moderate. In 2001 the maximum number of larvae on untreated plots was 11.7 larvae per plant, while in 2002 and 2003 it was lower, 5.5 and 6.1 larvae/ plant, respectively. The efficacy obtained with a full dose of B.t.t. reached 75% in the field, and 78% in the laboratory trial. The residual efficacy of a full dose of B.t.t. lasted 7-10 days. The application of both, full and reduced doses of B.t.t., did not result in a significant yield increase. The results indicate that only one treatment with B.t.t. insecticide alone is not enough for efficient protection of potato against the attack of CPB larvae. The application of neem resulted in an efficacy of between 54 and 87.9%. The residual activity of neem was too short to ensure significant yield increase in 2 out of 3 years of the investigation. The application of a full dose of pyrethrin ensured an efficacy of between 86 and 89% with residual activity of 7-10 days. Only in the trial in 2003 significant yield increase (40% higher than untreated control) after the application of a full dose of pyrethin was recorded. The application of both, full and reduced doses of spinosad resulted in very high efficacy (over 90%), with residual activity between 10 and 20 days. The application of spinosad resulted in a significant yield increase in 2003, both in full and reduced doses, and in 2001 in the full dose (the reduced dose was not tested alone in 2001). High efficacy of the reduced dose of spinosad indicated its high biological activity and possibility for the reduction of the recommended dose. However, applications of combinations of insecticides in reduced doses (spinosad with B.t.t., neem and pyrethrin) resulted in efficacies of over 97% with residual activity of up to 21 days. Significant yield increase was noted after the application of the combinations of spinosad with B.t.t. and pyrethrin. The results of the laboratory trial confirmed the results of field trials. The joint action of insecticides was mainly described as independent synergism. It can be concluded that applied combinations are suitable in IPM in potato.

Biological efficacy of some biorational and conventional insecticides in the control of different stages of the Colorado potato beetle, Leptinotarsa decemlineata (Say) (Coleoptera: Chrysomelidae)

“…However, Fitoverm showed the shortest residual activity as compared to Actara, Spinosad, and Mectin. Similarly, Barčić et al (2006) reported a high efficacy of Spinosad against L. decemlineata with a residual activity between 10 and 20 days after treatment. Mandour et al (2008) reported a longer residual activity of Spinosad against Palpita unionalis larvae with a LT 50 of 27.7 days.…”

“…Fortunately, biological control using biorational insecticides has become the most efficient means in potato pest management programs because their use reduce pollution and delay the development of resistance to other classical insecticides (Barčić et al 2006). Several biopesticide products based on the bacterium Bacillus thuringiensis (Bt) and on the fungal agent Beauveria bassiana have received considerable attention as a potential biological control agent over the last three decades against CPB (Lacey et al 1999).…”

“…Juss.) that has low or moderate efficacy against CPB larvae (Barčić et al 2006). Azadirachtin, a complex tetranortriterpenoid limonoid from the neem seeds, is the main component responsible for the toxic effects in insects.…”

Efficacy of Selected Insecticides and Natural Preparations Against Leptinotarsa decemlineata

“…Although the level of potato yields on the plants protected by Neem extract, B. bassiana and I. fumosorosea biopreparations was lower than on the chemically protected plants, the differences were not statistically significant, which points to a considerable yield protective role of these preparations in potato cultivation. In contrast, a rather low yield protective efficiency of various combinations of bioinsecticides was demonstrated by Barčcić et al (2006). Assimilation area is a decisive factor for plant productivity and its size depends among others on genetic traits of the species and variety, stage of plant development, plant healthiness and on the climatic conditions (Lepiarczyk et al 2005, Kulig et al 2010, Zarzyńska and Pietraszko 2015.…”

Comparative efficacy of classical and biorational insecticides on sugar beet weevil, Bothynoderes punctiventris Germar (Coleoptera: Curculionidae)

“…The applied doses in the first trial are doses used for the control of CPB. Igrc Barčić et al (2006) proved that even a reduced dose of spinosad resulted in significant efficacy on CPB larvae. The control of CPB is mainly targeting larvae.…”