Photo 1. Upper leaf surface showing typical yellowing of leaves at late stage of infection by Puccinia arachidis. The leaves dry up but remain attached.
Photo 2. Same leaf as in Photo 1, with the underside showing numerous orange-brown pustules where millions of spores of Puccinia arachidis are produced.
Photo 3. Close up of the underside of peanut leaf with orange-brown spots of the rust, Puccinia arachidis.
Worldwide. Asia, Africa, North, South and Central America, the Caribbean, Oceania. It is recorded from Australia, Fiji, Palau, Papua New Guinea, Samoa, Solomon Islands, Tonga, and Vanuatu.
Peanuts, and other plants belonging to the genus Arachis.
The rust infects leaves, petioles, pegs (the shoots that grow into the ground) and stems (Photo 1). On the leaves, the spots are at first yellow, rapidly turning orange and then red-brown as masses of spores develop and break through the leaf surface. The lower surface produces the most spores (Photos 2&3).
The spread of rust depends on wind to disperse the spores, and humidity to provide conditions for infection at the leaf surface.
Infection causes leaves to turn yellow (Photo 1), dry, curl and wither. It is not known what losses occurs in Pacific island countries, but it is likely that yields are reduced by 50%, probably much more. Infected plants mature 2-3 weeks earlier than those that remain healthy.
Once infections occur, rust develops very rapidly, faster than early and late leaf spot diseases (see Fact Sheet No. 36 ).
Inspect plants regularly, at least twice a week, looking for leaves that are turning yellow before their time, with red-orange spots on the underside.
Cultural control is important, but note that rusts only survive in living plants; they do not survive in crop remains or in the soil. Spores are spread in moist, warm air, and periods of cloudy wet weather favour outbreaks of the disease. Conditions in most Pacific island countries are ideal for this disease. The following should be done:
There are breeding programs at ICRISAT, the International Crops Research Institute for the Semi-Arid Tropics, the USA and Australia, to produce varieties with tolerance to rust and late leaf spot. One such variety from Australia is Sutherland. On this variety, the appearance of rust pustules is delayed, they are smaller and produce fewer spores. Several varieties have been imported by Papua New Guinea and Solomon Islands in recent years. Enquire whether these new varieties are available in your country.
AUTHORS Helen Tsatsia & Grahame Jackson
Photo 4 McKenzie E (2013) Puccinia arachidis PaDIL - (http://www.padil.gov.au).
Produced with support from the Australian Centre for International Agricultural Research under project PC/2010/090: Strengthening integrated crop management research in the Pacific Islands in support of sustainable intensification of high-value crop production, implemented by the University of Queensland and the Secretariat of the Pacific Community.
This fact sheet is a part of the app Pacific Pests and Pathogens
The mobile application is available from the Google Play Store and Apple iTunes.