Bunch-zone leaf removal to prevent damage by Lobesia botrana and grey mould.

Bunch-zone leaf removal in vineyards has been reported as an effective cultural practice to prevent damage by Lobesia botrana (Denis et Schiffermuller) (Lepidoptera Tortricidae) or Botrytis cinerea Pers. Fr. L. botrana larval activity is well known as a factor favouring the spread of B. cinerea. In 2007-2014, trials were carried out in a number of vineyards in north-eastern Italy to study the effects of leaf removal on the two carpophagous generations of the moth and on grey mould, simultaneously, and on the spatial distribution in relation to sunlight exposure of L. botrana larval nests within the grapevine canopy and eggs on bunches. Bunch-zone leaf removal applied at the pea-sized berry stage or a little later, during the L. botrana second-flight, reduced the infestation of both carpophagous generations by about 50% as well as B. cinerea infection at harvest time. This latter effect was partially due to moth control. In one of the two vineyards where distribution of larval infestation was studied, bunches not covered by leaves were significantly less infested than those covered. Females confined on bunches facing south and exposed to sunlight preferred to lay eggs on the sun-exposed side of the bunch. The lower L. botrana infestation observed both on plots subjected to bunch-zone leaf removal and on bunches facing south could be due to a higher egg/larval mortality caused by the very high temperatures reported for berries exposed to sunlight.