Incidence and pathogenicity of plant-parasitic nematodes on coffee in Australia and the potential of organic amendments as a management tactic

Abstract

Coffee is the world’s most traded commodity and a source of employment for millions of people, but one of the many challenges facing those who grow coffee is to minimise the yield losses caused by plant-parasitic nematodes which are estimated to reduce yields by 10 - 20 %. The findings of our surveys showed that there were six nematode genera (Pratylenchus, Meloidogyne, Rotylenchulus, Helicotylenchus, Paratylenchus and Xiphinema) found to be associated with coffee in Australia, and three species (M. hapla, P. brachyurus and R. reniformis) were genetically determined as the main species parasitic on coffee. Although P. coffeae and R. similis were not found on coffee, they were isolated from banana roots in north Queensland and caused severe damage to seedlings of Coffea arabica cv. K7 in a pathogenicity test. Moreover, the findings of this experiment indicated that coffee did not host P. zeae. Thus, Australian isolates of M. hapla, P. brachyurus, R. reniformis, P. coffeae, and R. similis can now be added to a recently compiled global list of nematodes that cause damage to coffee, while P. zeae can be removed from that list. Amending soil with organic materials, including sugarcane trash, cow manure, lucerne hay and chicken manure at a rate equivalent to 20 t/ha (i.e. 10 g organic amendment/kg soil) produced positive changes in soil chemical and biological properties and stimulated the growth of coffee plants for up to 12 months. Evidence was obtained to indicate that amending soil with these materials increased numbers of nematode-trapping fungi (e.g. Arthrobotrys musiformis and Arthrobotrys oligospora) and nematode predators (Mononchus papillatus), and this in turn enhanced natural mechanisms of suppression and reduced the population of P. coffeae. Sugarcane trash reduced the population of P. coffeae by 91% and was more effective than lucerne hay (84%), cow manure (82%) and chicken manure (74%) amendments.