HELICOVERPA ARMIGERA-PEST ON TOBACCO PLANTS

Abstract

Helicoverpa armigera Hubner is а migratory, cosmopolitan and polycyclic species. The pest is known as tobacco bollworm or budworm. The species is polyphagous and is an economically important agricultural pest. The studies were conducted on tobacco plants in the Experimental Field of the Scientific Tobacco Institute - Prilep during 2017/2018. Monitoring of population dynamics of H. armigera was performed during tobacco vegetation in a 10 -day period, using the method of examining 100 tobacco plants, with Zig-Zag review of pest scouting. The collected larvae were additionally fed and grown in a laboratory according to the standard laboratory methodology. Field and laboratory trials were carried out for control of H. armigera, with five insecticides/ active ingredients: Spinetoram (a.i. 250 g/kg)- 0.3 kg/ha, Indoxacarb (a.i. 150 g/L)- 0.3 L/ha, Metaflumizone (a.i 240 g/L)- 1 L/ha; Emamectin (a.i. 9.5 g/kg)- 2 kg/ha and Flubendiamide (a.i. 480g/L)- 250 g/ha. Larvae of tobacco budworm damage flowers, seed capsules and top tobacco leaves. The population dynamics of H. armigera showed that the species was present on tobacco from the beginning of July (when plants produce flowers) until the end of tobacco vegetation. The population was the most numerous in August and reached its highest level of density on 20th August in both years. In field trials, were determined five predatory species that fed with young larvae of H. armigеrа: Chrysopa formosa (Neuroptera, Chrysopidae), Chrysopa perla (Neuroptera, Chrysopidae), Chrysopa carnea (Neuroptera, Chrysopidae), Coccinella septempunctata (Coleoptera, Coccinellidae) and Adonia variegata (Coleoptera, Coccinellidae). In the beginning of October on tobacco plants we found parasitized larvae of H. armigera. In laboratory conditions parasitized larvae ate less and ceased developing at their 4th stage- L4. In each parasitized larva was developed one parasite species of Hyposoter didymator (Hymenoptera, Ichneumonidae). H. didymator is endoparasitoid wasp, and it lives on host tissues. According to field and laboratory trials during 2017/2018, all applied insecticides showed high efficacy in H. armigera control. The highest average mortality of 100% was caused by insecticides: Spinetoram, Indoxacarb and Emamectin. Flubendiamide had 97.5% efficiency in control of this pest, and the insecticide Metaflumizone 95.0%. This pest represents a significant challenge to tobacco filed and it produces high economic losses of tobacco seed each year. For the control of H. armigera, it is required constant monitoring of the lifecycle of the pest. One part of management strategy is to study parasitoids, predators and microorganisms and use them against H. armigera. Chemical control is still the most reliable and economic way of protecting tobacco crop from tobacco bollworm.