Insect repellent and chemical agronomic treatments to reduce seed numberin'Afourer'mandarin. Effect on yield and fruit diameter

Obtaining citrus fruits without seeds is a recurrent objective for farmers as it is one of the most valued char-acteristics, especially in mandarins.'Afourer'tangor is a highly valuable well-established mandarin, and a highpercentage of seeded fruits are produced under cross-pollination conditions. Several agronomic techniques havebeen suggested to control presence of seeds, such as covering with nets and copper sulfate (CuSO4) and gib-berellic acid (GA3) treatments. Natural bee repellents are also proposed to reduce the number of seeds per fruit.In this study, we aimed to compare the effect of several agronomic treatments to reduce the seed number in'Afourer' mandarin. To this end, we assessed the effect of chemical and bee repellent treatments on the seednumber per fruit and the side effect on yield and fruit diameter. Under these experimental conditions the two beerepellents, one based on zinc and one based onCapsicum annuum, were not useful for reducing the seed numberper fruit in'Afourer'mandarin. The copper sulfate + GA3treatment reduced the seed number per fruit by only35%, and this efficiency was clearly not enough to reduce the seed number for commercial purposes. The mosteffective method to reduce the seed number per fruit was covering with nets, but this technique led to markedlyreduced yields. Yield data was highly variable. Fruit diameter correlated positively with the seed number, but itwas a weak relationship as the seed number explained only 15% of fruit size variability (R2= 0,15)