PESTS AND DISEASES OF FORESTRY IN NEW ZEALAND
Lupin blight in New Zealand
Forest Pathology in New Zealand No. 22
Lupin blight
Based on M. Williams (1993)
Causal organism
Colletotrichum gloeosporioides Penzig
Colletotrichum gloeosporioides is a species complex with morphologically identical strains
restricted to a particular host plant or group of plants. This strain of C. gloeosporioides appears
to be restricted to Lupinus spp.
Type of injury
Infects stems, branches, leaves, petioles, and seedpods causing leaf loss, dieback, shoot
distortion, and mortality of whole plant.
Diagnostic features
• Branches and stems twisted or crooked.
• Withering of leaves and petioles followed by premature casting of foliage.
• Elongated, lens-shaped, and slightly sunken, stem and branch cankers.
• Basal cankers distorted and swollen with cracks and internal brown staining.
• Seed pods flattened and necrotic.
• Salmon-pink spore masses on necrotic tissue.
• Branch and stem breakage at cankers.
Hosts
Lupinus angustifolius, Lupinus arboreus, Lupinus cosentinii, Lupinus pubescens.
Distribution
Throughout New Zealand.
Disease development
The fungus overwinters in plant debris on the ground and spores are aerially dispersed. Spore
infection occurs after a period of warm wet weather.
The fungus attacks plants of all ages, and all aboveground plant parts are susceptible to infection.
Infected leaves and petioles wither and much of the foliage is cast. After infection a crooking of
succulent stems and branches occurs, which in the early stage is not associated with visible
lesions. Lens-shaped lesions up to 3 cm long develop on branches and stems, particularly at
branch axils. Salmon-pink spore masses develop on the lesions when the weather is warm and
wet. Older plants with a woody stem often develop cankers at ground level. These cankers
appear as a distorted swollen area with external cracks and internal brown staining. When there
is substantial dieback and/or severe basal cankers, plants will die. Death of plants infected while
in the cotyledon stage or when only the first few leaflets have developed is inevitable and rapid.
The fungus also attacks seed pods which become flattened and necrotic, with the pink fruiting
bodies visible on the outside. Seed production is markedly reduced.
Economic importance
The yellow tree lupin Lupinus arboreus has been utilised in New Zealand for its nitrogen- fixing
capabilities for many years. Lupin has been vital for the growth and continued health of Pinus
radiata in sand dune forestry. Lupin regenerates naturally after each thinning and harvesting
operation, and until the advent of the disease it was self-sustaining once it had become
established in an area.
In coastal areas where programmes of sand dune stabilisation took place, lupin seed was sown
between rows of the sand-binding marram grass Ammophila arenaria. Not only did the lupin
supply nitrogen by the symbiotic bacterial fixation of atmospheric nitrogen, but also it had the
ability to survive and do well in the harsh environment of a windblown sand dune and it was not
palatable to browsing animals.
Although the disease was first recognised in 1989, anecdotal evidence suggests that it was
present for at least 2 years prior to that. A national survey of lupin populations conducted in
early 1990 estimated that previously-established lupin had been reduced by 90-95% in the North
Island and the northern half of the South Island, and in other parts of the South Island 60-65% of
lupins had died. To some small degree there has been a recovery of the lupin population
throughout the country but nowhere has it attained its previous vigour. In the northern sand dune
forests monitoring has shown infection levels in years subsequent to 1989 to be quite high, and
mortality as a result of the disease is still in the region of 80% per annum.
Loss of lupin from the 60 000 ha of exotic forests planted on sand dunes threatens the
productivity of those forests. With a substantial reduction in the supply of nitrogen, the prospects
for these forests are stagnation of tree growth in older stands, failure of young stands to become
productive, and a risk of reversion to drifting sand dunes in exposed areas.
Control
On an experimental scale the fungicide chlorothalonil gave good control of lupin blight when
applied at a rate of 1.5 kg/ha at fortnightly intervals. The logistics of aerial spray applications to
control lupin blight would be difficult, the cost high, and where lupins are growing amongst
trees, or other tall vegetation, spray deposition on lupin would be much reduced. Emphasis is
now being placed on selecting a range of alternative nitrogen-fixing plants, with different
species being targeted for each site, to supplement the surviving lupin.
Bibliography
Beets, P.N.; Madgwick, H.A.I. 1988: Above-ground dry matter and nutrient content of Pinus
radiata as affected by lupin, fertiliser, thinning, and stand age. New Zealand Journal of
Forestry Science 18: 43-64.
Jackson, D.S.; Gifford, H.H.; Graham, J.D. 1983: Lupin, fertiiiser, and thinning effects on early
productivity of Pinus radiata growing on deep Pinaki sands. New Zealand Journal of
Forestry Science 13:159-182.
Williams, M. 1993: Lupin blight. New Zealand Forest Research Institute, Forest Pathology in
New Zealand No. 22.
Compiled: 1993
