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    Assessing the effect of plant surface on the predatory ability of Orius vicinus : a potential biological control agent of the tomato-potato psyllid (Bactericera cockerelli) : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Zoology at Massey University, Palmerston North, New Zealand
    (Massey University, 2019) Gamarra Landa, Abel
    The tomato-potato psyllid (TPP), Bactericera cockerelli (Sulc), is a pest to solanaceous crops (e.g. potato, tomato, peppers, and eggplant) and is associated with economically important plant diseases. Subsequently, chemical control is the preferred management option. However, chemical reliance is associated with a host of issues. The development of biological control methods is vital to implementing Integrated Pest Management (IPM) programs as an alternative to broad-spectrum insecticide usage. The predatory bug Orius vicinus (Ribaut) is a potential biological control agent that is capable of consuming all nymphal life stages of TPP. In order to be a commercially viable management option, potential biological control agents of TPP have to cope with the different morphological plant features of the pest’s wide range of host plants. Tomato and capsicum plant surfaces were selected as the experimental surfaces for my thesis because they differ significantly in their substrate morphology. Tomato plant surfaces can be a hostile environment for potential biological control agents due to the negative effect tomato trichomes have on their foraging performance. Alternatively, because capsicum plant surfaces are virtually void of trichomes they appear to be more suitable for effective biological control agent deployment. I exposed the predatory bug to a variety of TPP nymph densities (10, 20, 30 and 40 individuals) in order to determine the functional response of O. vicinus. Furthermore, the predatory bug was exposed to all five TPP nymphal stages simultaneously. The predatory performance of O. vicinus was also assessed on experimental arenas varying in complexity (leaflet vs. small plant environments). The functional response was determined to be Type II on both plant surfaces. Nymph consumption at higher prey densities (30 and 40 nymphs) was significantly greater on capsicum than on tomato. Nymph consumption at lower prey densities (10 and 20 nymphs) was only significantly greater on capsicum when the complexity of the experimental arena increased from leaflet to small plant. The influence of O. vicinus in nymph dispersal was also assessed. My results revealed that the presence of O. vicinus increased the dispersal of nymphs to lower leaf surfaces and that nymph dispersal was significantly greater on capsicum than on tomato. TPP nymph size preference by O. vicinus was determined in my study. I established that the predatory bug is capable of killing all nymphal stages. My study strongly indicated that the predatory bug is more likely to target and consume medium (3rd instars) and large nymphs (4th and 5th instars) over small nymphs (1st and 2nd instars). I investigated the behaviour of O. vicinus adults and TPP nymphs during their interactions via video recordings. The predatory bug spent a significantly greater amount of time investigating TPP nymphs on capsicum than on tomato. There was significantly higher number of attacks recorded on capsicum. The greater killing percentage on tomato suggests that the defensive capabilities of TPP nymphs appear to have been negatively affected by the tomato substrate. The results from my study indicate that augmentative releases of O. vicinus, in the presence of smaller TPP nymphs, could be a viable biological control option on capsicum plants. However, the predatory bug will likely struggle if deployed on tomato plants. Future studies should be conducted in settings such as open field or glasshouses using multiple predatory bugs in the presence of susceptible life stages to assess augmentative release efficiency.
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    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
    (Massey University, 2011) Puketapu, Aleise
    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.