Grass grub damage and mycorrhizal colonisation of grapevine rootstocks

Abstract

Field observations and a grower survey during 2002/2003 indicated that grass grub larvae might be responsible for the death of young grape vines In November 2003 a pot trial was established to determine whether grass grab larvae feeding caused sufficient root damage to account for observed vine deaths The experiments also evaluated whether arbuscular mycorrhizal fungi (AMF) colonisation of grape vine roots was affected by grass grub feeding Grass grub damage was found on the belowground portion of the trunk and was proportional to the numbers of grubs present However root and shoot weight and shoot length were not affected by grub density when measured two months after grubs were introduced AMF colonization varied between the four rootstocks in the trial and was higher where grass grubs had been introduced Further research is required to elucidate the causes of young vine decline in Marlborough