In Central and North America, Australia and New Zealand, potato (Solanum tuberosum) crops are attacked by Bactericera cockerelli, the tomato potato psyllid (TPP). ‘Mesh crop covers’ which are used in Europe and Israel to protect crops from insect pests, have been used experimentally in New Zealand for TPP control. While the covers have been effective for TPP management, the green peach aphid (GPA, Myzus persicae) has been found in large numbers under the mesh crop covers. This study investigated the ability of the GPA to penetrate different mesh hole sizes. Experiments using four sizes (0.15 × 0.15, 0.15 × 0.35, 0.3 × 0.3 and 0.6 × 0.6 mm) were carried out under laboratory conditions to investigate: (i) which mesh hole size provided the most effective barrier to GPA; (ii) which morph of adult aphids (apterous or alate) and/or their progeny could breach the mesh crop cover; (iii) would leaves touching the underside of the cover, as opposed to having a gap between leaf and the mesh, increase the number of aphids breaching the mesh; and (iv) could adults feed on leaves touching the cover by putting only their heads and/or stylets through it? No adult aphids, either alate or apterous, penetrated the mesh crop cover; only nymphs did this, the majority being the progeny of alate adults. Nymphs of the smaller alatae aphids penetrated the three coarsest mesh sizes; nymphs of the larger apterae penetrated the two coarsest sizes, but no nymphs penetrated the smallest mesh size. There was no statistical difference in the number of aphids breaching the mesh crop cover when the leaflets touched its underside compared to when there was a gap between leaf and mesh crop cover. Adults did not feed through the mesh crop cover, though they may have been able to sense the potato leaflet using visual and/or olfactory cues and produce nymphs as a result. As these covers are highly effective for managing TPP on field potatoes, modifications of this protocol are required to make it effective against aphids as well as TPP.

No abstract

An insect’s fitness varies on different host plant species, and can be affected by previous host feeding experience. In New Zealand, Bactericera cockerelli (the tomato potato psyllid (TPP)) overwinter on various host species, and later migrate to annually grown crop host plants. How changing host plant species affects the insect’s fitness is unknown. This study evaluated if transferring adult TPP from non-crop to crop host species impacts the development and survival of their progeny. TPP were reared on non-crop host species, boxthorn, poroporo, and crop host species, potato and tomato. Adults were transferred from non-crop to the crop host species and allowed to oviposit for 48 hours before being removed. The eggs and nymphs were monitored every 24 hours for the development and survival of each life stage. The incubation period of eggs from adults transferred from poroporo to tomato was 6.9 days, and for boxthorn to tomato was 7.2 days, and was less than for eggs of adults moved from tomato to tomato (9.0 days) and potato to potato (9.2 days) (P < 0.05). Nymph developmental time was similar for all treatments. Total development time (egg to adult) was shorter for the progeny of adults from poroporo transferred to tomato (20.5 days) than those from tomato to tomato (23.2). The survival of eggs did not differ across treatments. Fewer nymphs survived when adults were transferred from tomato to tomato (50.4%) than those from poroporo to tomato (92.1%) (P < 0.05). Total survival (egg to adult) was higher for progeny of adults transferred from poroporo to tomato (80.0%) compared to boxthorn to potato (35.3%), boxthorn to boxthorn (40.7%), poroporo to potato (33.9%) and tomato to tomato (37.6%) (P < 0.05). The implications of this shift in fitness are discussed in relation to TPP management.

Two field trials were undertaken in a fallow field adjacent to citrus trees at Agricultural Operations at the University of California, Riverside (CA), USA to examine the efficacy of 14 chemical lures for attracting western flower thrips (WFT) Frankliniella occidentalis (Pergande) and onion thrips (OT) Thrips tabaci Lindeman to yellow sticky traps over 24 hours. Air temperatures during the two trials ranged from 16 to 36 o C. In both trials traps with methyl isonicotinate caught significantly more (x2.8 and x3.4 respectively) female WFT than traps without lures. No other chemical lure tested caught as many WFT as the methyl isonicotinate-baited traps. In trial 1, traps with ethyl isonicotinate (not included in bioassay 2) caught significantly more female OT (x4.0) than traps without lures. No other chemical lure tested caught as many OT as the ethyl isonicotinate-baited traps. Because of the close proximity of the traps (10 m between traps), control traps were expected to have been influenced by odour from baited traps, thereby reducing the apparent efficacy of the baited traps.Some thrips species (Thysanoptera) are important pests of crops in New Zealand, and are vectors of several important plant tospoviruses. 'Lure and kill' could provide an alternative or complementary control to the current practice that relies on the unsustainable use of insecticides. The efficacy of a lure and kill device was tested on thrips in a grass field. The thrips olfactory lure used was methyl isonicotinate, the visual cue was yellow and the kill component in the trap was an organophosphate insecticide applied to an absorbent material. The control device was yellow, but did not contain the lure or insecticide. The device allowed thrips to freely enter and leave, but limited the access of non-target organisms. The devices were left out for three days. The ratio of dead thrips in the control devices relative to those with insecticide was 1:34.4. Addition of the olfactory lure to the insecticide devices increased the ratio to 1:47.5. The results highlight the need for an effective olfactory lure component to ensure the insects enter and explore the trap, to be exposed to a lethal dose of the kill component. Results are discussed in relation to thrips pest management.