Field evaluation of the effectiveness of mesh crop covers for the protection of potatoes from tomato potato psyllid

Abstract

Tomato potato psyllid (TPP; Bactericera cockerelli) is a serious pest of solanaceous crops in New Zealand. Control of TPP is currently dominated by synthetic biocides, although this method is curative and does not always prevent transmission of TPP-vectored plant diseases. This study evaluated mesh crop covers as non-chemical alternatives for controlling TPP in potato crops. Over two growing seasons in Canterbury, New Zealand, potatoes growing under mesh covers were found to have reduced numbers of TPP nymphs and adults, increased tuber size, increased overall yield and enhanced storage potential compared with uncovered plots. There was also a slight reduction in potato blight spores under mesh, and the actual occurrence of blight was slightly reduced in one trial. The results of this study indicate that mesh crop covers could provide a viable option for potato growers who wish to protect their crops from TPP without using chemical insecticides.

The ability of the green peach aphid (Myzus persicae) to penetrate mesh crop covers used to protect potato crops against tomato potato psyllid (Bactericera cockerelli)

“…That adults did not penetrate mesh, but newly hatched nymphs did, suggesting a means by which aphids entered all mesh covered plots in the field trial of Merfield (2017) : adult aphids that alighted on the upper surface of the mesh, produced nymphs, which are small enough to penetrate the mesh, and once through that they can reproduce on the potato crop. This result needs to be verified under field conditions.…”

“…Talekar, Su & Lin (2003) and Licciardi et al (2007) reported that adult female moths of the armyworm ( Spodoptera littoralis (Boisduval 1833)) laid eggs on the top of a hooped screen, and the newly hatched larvae were sufficiently small to penetrate the mesh and drop onto the crop below. Merfield (2017) found a large number of lacewings ( Micromus tasmaniae (Walker 1860)) in plots of potatoes under mesh, following aphid outbreaks under the mesh. Lacewing adults are much too large to penetrate mesh, and the mesh was dug into the soil preventing entry from the edges, so it was hypothesised that the lacewings laid eggs on the mesh, and then the neonate larvae penetrated the mesh.…”

“…Mesh crop covers with hole sizes 0.15 × 0.15 mm and 0.15 × 0.35 mm were supplied by AB Ludvig Svensson ( http://www.ludvigsvensson.com ) as ECONET 1515 and ECONET 1535. Those measuring 0.3 × 0.3 mm and 0.6 × 0.6 mm were supplied by Crop Solutions Ltd. ( http://www.cropsolutions.co.uk ) and were custom-made for an earlier field trial ( Merfield, 2017 ). To test the accuracy of the measurement for each mesh crop cover hole size used in this experiment, ten random samples of each type were selected and 10 holes of each sample were measured under a Nikon SMZ25 microscope (magnification range 0.63–15.75×).…”

“…In New Zealand, however, such covers have only recently been investigated experimentally. Mesh crop covers with a hole size up to 0.6 mm were completely impermeable to TPP in laboratory tests, and were able to reduce TPP populations in field trials to very low levels, even outperforming insecticides ( Merfield, 2017 ; Merfield et al, 2015a ; Merfield, Hale & Hodge, 2015b ; Merfield et al, 2019 ).…”

“…Despite the promising results obtained with mesh crop covers for control of TPP, an unexpected result was that aphids, believed to be mostly the green peach aphid (GPA, Myzus persicae (Sulzer, 1776) (Hemiptera: Aphididae)) appeared in large numbers under the mesh crop covers, particularly in the 2016–17 field trials where their populations were significantly higher than uncovered controls, even though the edges of the mesh crop covers were dug into the soil, creating a complete seal ( Merfield, 2017 ; Merfield et al, 2019 ).…”