Early Detection and GIS

The Phylloxera and Grape Industry Board have conducted a phylloxera detection program in South Australia since 2001. The program involves collecting infrared aerial imagery of vineyards, analysing it to identify vines with phylloxera-like symptoms and inspection of these ‘suspect’ vines. To date, no phylloxera has been found.

Why a phylloxera detection program for South Australia?

Phylloxera has never been found in South Australia. Given the large area, high density of vineyards and the large number of vines not grafted to phylloxera-tolerant rootstocks, if phylloxera was to ever reach the state, there is a high risk that it will spread rapidly with significant economic impact. Early detection of phylloxera is critical to to restrict the insect’s spread and minimise the impact of an infestation.

Even if phylloxera is not found in South Australia, the program will reinforce South Australia's status as a state free from Phylloxera.

A three step program

STEP 1: Collection of infrared aerial imagery

Each year, high resolution infrared aerial imagery is collected, by a camera mounted to a light aircraft, of vineyards within a given area of South Australia.

Imagery is collected during summer, between grape veraison and harvest, when vine canopies are fully developed and phylloxera infested vines will be most distinguishable from non-infested vines.

STEP 2: Identification of phylloxera 'suspect' sites

The aerial imagery is analysed to identify vines that display canopy symptoms typical of phylloxera infested vines. These symptoms include reduced canopy, shoot growth and bunch size and yellowing of leaves. Patches of infested vines will usually be seen in the imagery as an ‘oval shaped’ patch of low vigour.

Imagery of this King Valley vineyard (Victoria, Australia) highlights sites of phylloxera infestation (arrowed).

STEP 3: Field inspections of suspect sites

Of course phylloxera is not the only cause of low vigour. Shallow soils, rock outcrops, faulty irrigation, uncontrolled weeds, viruses and other diseases all affect vigour. Inspecting the vines is the only way to determine the cause. Out in the vineyard, fine feeder roots are inspected for the yellow hook-shaped galls that are symptomatic of phylloxera.

A partnership with grapegrowers

Each grapegrower receives a copy the aerial imagery of their vineyard. They receive a ‘true colour’ image, and a Normalised Differentiation Vigour Index (NDVI) image. NDVI is a process that highlights variation in vigour within a selected area. Growers are also able to purchase digital copies of their vineyard at a small cost. Permission is always sought from grapegrowers before inspecting any vineyards and hygiene protocols are strictly enforced to prevent an inspector transferring pests, diseases or weeds between sites.

Reference

Links to more information

Some Precision Viticulture links