Nematicidal effect of chestnut tannin solutions on the carrot cyst nematode Heterodera carotae Jones

The effectivenes of chestnut tannin aqueous solutions was tested against the carrot cyst nematode Heterodera carotae in a field experiment at Zapponeta (province of Foggia) in Apulia region (Italy). A sandy soil infested by the cyst nematode was deeply ploughed, rotavated and subdivided in 2 m x 3 m plots distributed in a randomized block design with five replications per each treatment. Chestnut aquoeus solution treatments were: a) 25 g/m2 in 4 l water/m2 applied in pre-emergence, b) 25 g/m2 in 4 l water/m2 applied in pre-emergence and 30 days after carrot emergence, c) 45 g/m2 in 4 l water/m2 applied in pre-emergence, d) 45 g/m2 in 4 l water/m2 applied in pre-emergence and 30 days after carrot emergence. Untreated soil and and the nematicide fenamiphos (60 l c.p./ha) were used as controls.At harvest, number and weight of marketable tap-roots from the central square metre of each plot were recorded. Soil samples, each a composite of 20 cores, were collected in the same central area of each plot. Cysts from a 100 g dried sub sample were extracted with a Fenwich can and crushed to count eggs and juveniles. All data were statistically analysed and means compared by LSD’s test. Treatments with tannin solutions at 45 g/m2 applied in pre or in pre and post carrot emergence significantly increased carrot marketable yield in comparison to untreated control. All treatments significantly increased the average weight of carrots, with the exception of the lowest dose of tannin applied before emergence, in comparison to untreated control. No significant differences were observed in the number of cysts/100 g soil among the different treatments including the fenamiphos and the untreated controls. The final nematode population density observed in the untreated control was significantly higher than those observed in all other treatments in which no differences were observed. On the base of results, the use of tannin should be favourably considered for plant protection against phytoparasitic nematodes although some aspects remain to be investigated.