The text books refer to diseases and there are very few that affect lavender in New Zealand. The major worry is Alfalfa Mosaic Virus (AMV). Bright yellow patches develop on the leaves in the spring and the young shoots may be twisted.
The disease appears on Lucerne, Clover and many other garden plants and weeds. The virus is spread by aphids and also any cutting tool which has been used on an affected plant. The only remedy is to remove the lavender plant and burn it and disinfect any tools used in connection with the infected plant.
Rabbits are a major pest in certain regions and suitable fencing will be required around lavender plantations as they like to dig up young plants that have been newly planted out. Planting into weed mat has proven to be an effective method of deterring rabbits from digging up the small plants.
Spittle bug is often found on lavenders in early summer and although the frothy blobs of spittle look unsightly, they cause no significant damage to a crop that is grown for oil production.
Garden weevil has become quite a pest in certain regions of the North Island. They chew the stems of mature flower heads and this results in the heads falling off or becoming withered causing significant loss of oil production and/or dried rubbings. Research being carried out by LGA members will ascertain the most eco-friendly type system of achieving pest control, as the garden weevil is extremely difficult to manage without some form of contact insecticide.