Efficacy of chemical repellents to reduce bird damage rate to oilseed rape plants

Oilseed rape (Brassica napus) is considered as a strategic crop by the Ministry of Jihad-e Agriculture. Birds are important pests of this crop that cause severe damage to the oilseed rape plant every year. Bird damage to oilseed rape was noticed because of edible oil import and the importance of self-sufficient production in Iran. Bird damage occurs in the early stages of oilseed rape cultivation by larks. If they gather on oilseed rape fields, they would cause significant and economic damage extents. As using pesticides is generally forbidden for bird damage control around the world, the use of chemical repellents is recommended. Chemical repellent compounds affect sight, smell and taste organs of birds to deter them. 

We implemented an experiment using a Completely Randomized Block Design with three repellents (Methyl Anthranilate, Cinnamic Acid and Ammonium Aluminium Sulphate) in field conditions. Experiments were implemented in Ilam and Mazandaran provinces in 1000-m2 plots. Treatments were applied with the following doses: 1. Methyl Anthranilate 3400g/hec, 2. Cinnamic Acid 2000g/hec, 3. Ammonium Aluminium Sulphate 50g/lit and 25kg/hec, and 4. Control. In every sampling time, ten quadrats of 1*1 m2 were randomly applied in each treatment. The total number of damaged and undamaged plants were registered and the percentage of damaged plants was calculated accordingly. Results were analyzed using SPSS 17.0 software.

Based on the results, all three treatments had significant differences from control. In Ilam, Cinnamic Acid had a lower damage rate (1.58%) in 2017, and Methyl Anthranilate showed a lower damage rate (13.7%) in 2018. In Mazandaran, Ammonium-Aluminium Sulfate showed a lower bird damage rate (23.0%) compared to control (49.2%). In both regions and years, bird damage was significantly different among weeks. Also, independent and composed effects of treatments and weeks were significant in both regions and years. Regarding the mode of action of the treatments, Cinnamic acid with unpleasant taste and white color was the most effective treatment, oily Methyl Anthranilate also made an unpleasant smell. Ammonium-Aluminium sulfate has also reduced bird damage with salty and bitter tastes simultaneously. Cinnamic acid and Methyl Anthranilate should be imported, while Ammonium-Aluminium sulfate can be produced inside the country.

All the treatments made less bird damage rate and among them, Cinamic acid had multiple effects. The results of this study raised hopes for making new national and cheaper compounds that have multiple effects on the sight, smell and taste organs of birds.