Researches Concerning Sunflower Seeds Treatment against Tanymecus Dilaticollis, in Green House Conditions

Abstract

Abstract In the last years sunflower become one of the most important crops in Romania. The most of the surface cultivated with sunflower from our country is located in south and south-east and, in many cases, sunflower is cultivated after maize. As result the attack of the maize leaf weevil (Tanymecus dilaticollis Gyll) at sunflower plants has increasing. The attack is dangerous when sunflower plants are in first vegetation stages (BBCH 10-BBCH 14). Similar with maize crop, sunflower seeds treatment with neonicotinoids were generalized after 2007. As result of the EU directive 485/2013, no active ingredients remain available for sunflower seeds treatment, against T. dilaticollis, in Romania. The researches from the last years were orientated for finding of the possible alternatives for seed treatments, in eventuality of permanent ban of neonicotinoid insecticides, after 2018. Because of the variability of climatic conditions from the field, during spring period, researches concerning effectiveness testing of sunflower seed treatments, in green house conditions, using high pest pressure is a good method to evaluate influence of the different active ingredients to control T. dilaticollis adults. In this experiment it has tested three doses of cyantraniliprole active ingredient (7.5, 10.0 and 12.5 l/to) and three neonicothinoid active ingredients (imidacloprid, clothianidin, thiamethoxam). Sunflower seeds were placed in plastic pots. After plants emergence the insects were added in pots. At each pot it has added 20 adult insects, collected from the field. Each day, it has recorded insect mortality. At 8 days from the start of the experiment, it has assessed attack intensity of the adult insects on sunflower plants. The attack was evaluated using a scale from 1 (plant not attacked) to 9 (plant complete destroyed). In conditions of high pest pressure (4 insects/plant) the attack intensity of T. dilaticollis at sunflower plants was ranged from 3.35 in case of variant treated with clothianidin and 8.50 in case of untreated plants. Lower attack intensity of the pest at sunflower plants it has registered in case of variants treated with imidacloprid and thiamethoxam (I=3.58 and 3.50). Plants emerged from the untreated seeds were destroyed by the insects, at 8 days from the start of the experiment.