The lifecycle and epidemiology of the tomato/potato psyllid (Bactericera cockerelli) on three traditional Māori food sources : a thesis in partial fulfilment for the degree of Master of Science in Plant Protection at Massey University, Palmerston North, New Zealand

Abstract

The tomato/potato psyllid (Bactericera cockerelli (Sulc), TPP) is a species of Psylloidea first detected in New Zealand in 2006. Since its incursion the TPP has proved to be a major insect pest of solanaceous crops, particularly potatoes (Solanum tuberosum), tomatoes (Lycopersicon esculentum) and capsicums (Capsicum L.). The TPP is a vector of Zebra Chip Disease or liberibacter (Candidatus Liberibacter solanacearum syn. psyllaurous), a lethal plant disease related to Citrus greening disease (Candidatus Liberibacter asiaticus). Successive annual population outbreaks coupled with widespread liberibacter infection continues to challenge New Zealand‘s horticulture sector. Three traditional Maori food sources, namely taewa (Solanaceae, Solanum tuberosum L. ssp. andigena and ssp. tuberosum), kumara (Convolvulaceae, Ipomoea batatas (l.) Lam.) and poroporo (Solanaceae, Solanum aviculare G. Forst syn. S. Laciniatum (LINN.), are known to be susceptible to TPP infestation. Kumara and taewa are annual summer plants present during the peak TPP development and population growth period. Poroporo flowers and fruits year-round and is therefore theoretically susceptible to infestation throughout the year and may serve as a potential overwintering host and food source for TPP. Poroporo was assessed as an overwintering host of the TPP and the lifecycle progression of TPP was also compared on the three host plant species; taewa, kumara and poroporo. The role of these three host plants in the annual lifecycle of this insect pest in the New Zealand environment. The results showed that poroporo was not an important overwintering host of the TPP in the Manawatu/Rangitikei region; rather it can be viewed as an alternative or refuge host in the absence of the primary solanaceous host species and other volunteer weed host plants. The results indicated that taewa is a more suitable host of the TPP than poroporo and kumara. In the same vein, poroporo is clearly more suitable as a host than kumara. The relationship seen in this study in terms of host suitability can be pictorially represented as; Taewa> Poroporo> Kumara This study showed that all three host species are capable of supporting TPP and therefore each of the host species should be managed with a view to minimise the impact of TPP across seasons.