Laboratory and field studies about effectiveness of some systemic insecticides against date palm tree borers (Rhinoceros beetle), oryctes sp. (Coleoptera: Scarabaeidae)

The purpose of this study was to find out how well three second-generation neuro-active insecticides from the Neonicotinoids class work at getting rid of pests that are palm rhinoceroses (genus Oryctes) and what the best way is to use them. Three neuro-active insecticides from the class Neonoctoniods were selected: Mospilan (Acetamiprid 20%), Tiam WG (25%), and Radical (Imidacloprid 20%). Laboratory tests were carried out in the laboratories of the Al-Nahrain University/Faculty of Biotechnology, and field tests were carried out in the palm groves south of Baghdad during 2021 and 2022. Laboratory tests were carried out in two ways, one of which was direct spraying of the larvae, and the second was larval-food treatment. As for the field tests, they were implemented in three diverse ways. The first is direct spraying on the top of the palm tree, injecting it into the trunk, and watering through the soil. The laboratory tests involved the combination of pesticides with water at different concentrations. Specifically, Mospilan was mixed at concentrations of 0.5 g/liter and 1 g/liter of water. Tiam was mixed at concentrations of 0.3 g/liter and 0.6 g/liter of water. Lastly, Radical was mixed at concentrations of 0.38 ml/liter and 0.76 ml/liter of water for direct spraying of larvae and larval-food treatment, respectively. In field tests, the following concentrations were used: Mospilan, two treatments for direct spraying on the palm tree (one with a lower concentration and the other with a higher concentration): five liters of solution per palm tree with a concentration of 0.5 g/liter (lower concentration) and 1 g/liter (higher concentration). Tiam: 0.3 g/L and 0.6 g/L; Radical: 0.38 ml/L and 0.76 ml/L. As for the tree trunk injection experiments, the following concentrations and quantities were used: Mospilan, 20 ml of solution with a concentration of 1 g/ 2 ml of water per palm tree, and 20 ml of solution with a concentration of 1 g/ 3 ml of water per palm tree. For Radical, 20 ml of solution was used for every tree with a concentration of 1 ml/1.5 ml of water. For watering-through soil experiments, the following concentrations were used: Mospilan 50 liters per palm tree with a concentration of 1 g/L water; Tiam 50 liters per palm tree with a concentration of 1 ml/3.8 L water. In laboratory experiments, only the number of dead larvae was counted. But for field experiments, both dead and alive larvae were counted. Lab results showed that all three pesticides tested were effective when used either by direct spraying on larvae or when treating food, with an effectiveness range of 96%–100% for both lower and higher concentrations. However, a significant difference was observed in the duration it took for the larvae to start dying when treated with different concentrations, where the death of larvae treated with lower concentrations of pesticides started after 12 days compared to only 2 days for larvae treated with higher concentrations of pesticides. When used in direct spraying on top of palm trees in field experiments, pesticides demonstrated no efficacy because the proportion of dead and alive larvae was similar across all treatments, including the comparison treatment. No discernible impact on the insect was seen when larger doses of pesticides were employed, resembling the results obtained with lower concentrations and control treatments. The corrected killing values for Radical, Tiam, and Mospilan were 0.34%, 3.7%, and 5.2% respectively.. When higher concentrations were used, the corrected killing values were 3.7%, 4.6%, and 8.5%, respectively. As for trunk injection and soil watering experiments, both Mospilan and Tiam showed high efficiency in killing the larvae in trunk injection experiments, with a corrected value of 91.7% and 100%, respectively. And a corrected value of 90.1% and 100% in soil watering experiments for Mospilan and Tiam, respectively. Radical showed low efficiency when compared to the other two pesticides in both injection treatments and soil watering treatments, with an effectiveness of 64% and 65.4%, respectively.