Agroecological management of a soil-dwelling orthopteran pest in vineyards

The efficacy of different combinations of undervine and inter-row treatments for managing a soil-dwelling orthopteran pest, weta (Hemiandrus sp.), in vineyards was investigated over 2 seasons. This insect damages vine buds, thus reducing subsequent grape yield. The undervine treatments comprised pea straw mulch, mussel shells, tick beans [Vicia faba Linn. var minor (Fab)], plastic sleeves on vine trunks (treated control) and control (no intervention), while inter-rows contained either the existing vegetation or tick beans. Treatments were arranged in a randomized complete block design with 10 replicates. Data were collected on weta densities, damage to beans and components of yield. The latter were numbers of bud laid down per vine, shoots per bud, clusters per shoot, grape bunches per vine, bunch weight and yield. The undervine treatments significantly affected all variables except the number of shoots per bud. In contrast, none of the variables was significantly affected by the inter-row treatments or their interaction with undervine treatments, apart from weta density. At the end of the experiment, weta density in the shell treatment was about 58% lower than in the control. As a result, there was about 39% significant yield increase in that treatment compared to the control. Although the undervine beans and sleeves treatments increased yield, there were no reductions in weta density. With undervine beans, the insect fed on the bean plants instead of vine buds. Thus, yield in that treatment was approximately 28% higher than in the control. These results demonstrate that simple agroecological management approaches can reduce above-ground damage by soil-dwelling insects

Identifying plant DNA in the faeces of a generalist insect pest to inform trap cropping strategy

Monocropping elevates many insects to the status of economic pests. In these agroecosystems, non-crop habitats are sometimes deployed as trap crops to reduce pest damage. This environmentally friendly alternative to pesticides can be particularly fitting when dealing with native invaders that may be afforded legal protection or enjoy public sympathy as is the case for the ground wētā Hemiandrus sp. ‘promontorius’ (Orthoptera) in New Zealand. However, this approach requires knowledge of the insects’ diet to select the most appropriate plant species for trap cropping. Here, ingested plant DNA in the faeces of wētā was analysed to help develop strategies for mitigating its damage in New Zealand vineyards. DNA was extracted from faeces of wētā collected from six different vineyards over four seasons. Using a DNA metabarcoding approach, we amplified the rbcL gene region and sequenced the amplicons on an Illumina MiSeq platform. The identity of plants in the diet of this insect was determined by comparing the sequences generated with those available in the GenBank database and cross-checking the results with a database of plants known to be present in New Zealand. A total of 47 plant families and 79 genera were detected. Of the genera identified, Vitis, Poa, Festuca, Anthoxanthum, Anagallis, Camelina, Epilobium, Menyanthes, Pedicularis, Urtica, Garrya, Pinus and Tilia were the major ones (i.e. they were present in more than 50% of the faecal samples). The composition of the above plant taxa in faecal materials was significantly different between collection sites or dates, except for Menyanthes. The occurrence of the latter was significantly different between collection sites. These results indicate that effectively mitigating wētā damage to vines requires the use of a diverse mix of plant species for trap cropping as wētā seem to be highly generalist in their feeding behaviour even when plant diversity is relatively low

Ground wētā in vines of the Awatere Valley, Marlborough: Biology, density and distribution

The endemic New Zealand ground wētā (Hemiandrus sp. ‘promontorius’) has a Naturally Uncommon conservation status. This is because of the paucity of information on its density and distribution. Here, the biology, density and distribution of a population of this wētā found in and around vineyards in the Awatere Valley, Marlborough was studied. Wētā density was assessed in vineyards, paddocks and shrublands in this valley. Soil moisture, penetration resistance, pH and organic matter were recorded at locations with and without wētā. Wētā density in vineyards was significantly higher than in either paddocks or shrub habitats. In vineyards, the density of this insect was significantly higher under-vines than in the inter-rows. Higher numbers of this wētā were found in moist soils that required lower force to burrow. Females laid an average of 55 eggs between March and April, which hatched in September. These findings highlight the intersection between agriculture and conservation.This study was funded largely by the New Zealand Government’s Callaghan Innovations PhD Research and Development Fellowship Grant (Project no. CONB1201), in partnership with Constellation Brands New Zealand