Development of a densovirus-based bioinsecticide for use in the control of the darkling beetle, tenebrio molitor (coleoptera: Tenebrionidae) (linnaeus, 1758)

The mealworm beetle, Tenebrio molitor, is a harmful insect belonging to the Coleoptera order that causes serious damage to stored products worldwide. Although chemical methods are primarily used to combat this insect, the negative effects and high cost of chemicals have made it imperative to develop biological control methods against harmful insects. It is known that densoviruses, which are one type of insect virus, have high potential for use in biological control. In this thesis study, a densovirus was identified from T. molitor for the first time in Turkey by our team and was entered into the ICTV database under the name TmDNV-TR. A TEM image was taken of the isolated and purified TmDNV isolate, and its size was found to be 28.95 nm. After a complete genome analysis, the genome size was found to be 5467 bç. REN and amino acid variation studies revealed amino acid variations in all gene regions. Subsequently, a maximum likelihood phylogenetic tree and Kimura-2 matrix were constructed. The Kimura matrix result determined the genetic distance value between TmDNV-TR and other TmDNVs in the database to be 0.023. Subsequently, a dose response test of the virus on T. molitor was performed, and statistical data analysis revealed that at the end of day 8, LD50: 1.091 x 105 copies/mL-1, LT50: 5 days, LD95: 8.94 x 107 copies/mL-1, and LT95: 7 days. After the lethality of the densovirus on insects was proven, a formulation called Tenebriokillers was prepared using this virus. The dose response test results of the prepared formulation also showed that five doses of the formulation were pathogenic to T. molitor larvae. In the final step, the formulation stability test experiments showed that at the end of the 14th day, the mortality rate of the fresh formulation (0 months) was 100%, while at 4°C, the mortality rate at the end of 3 and 6 months was 100%, and at 25°C, the mortality rate at the end of 3 and 6 months was 98% and 95%, respectively. With the preparation of this densovirus-based bioinsecticide, which we named Tenebriokiller, a significant contribution has been made to the control of T. molitor.