Search

Tuta absoluta is one of the most damaging pests of tomato crops worldwide. Damage due to larvae may cause up to 100% loss of tomato production. Use of natural enemies to control the pest, notably predatory mirids such as Nesidiocoris tenuis and Macrolophus pygmaeus, is increasingly being promoted. However, considering the potential damage caused to tomatoes by these omnivorous predators in the absence of T. absoluta, an alternative solution could be required to reduce tomato damage and improve the predators' performance. The use of companion plants can be an innovative solution to cope with these issues. The present study aimed to determine the influence of companion plants and alternative preys on the predators' performance in controlling T. absoluta and protecting tomato plants. We evaluated the effect of predators (alone or combined) and a companion plant (sesame (Sesamum indicum)) on T. absoluta egg predation and crop damage caused by N. tenuis. The influence of an alternative prey (Ephestia kuehniella eggs) on the spatial distribution of predators was also evaluated by caging them in the prey presence or absence, either on tomato or sesame plants or on both. We found that the presence of sesame did not reduce the efficacy of N. tenuis or M. pygmaeus in consuming T. absoluta eggs; hatched egg proportion decreased when N. tenuis, M. pygmaeus, or both predators were present. More specifically, this proportion was more strongly reduced when both predators were combined. Sesame presence also reduced necrotic rings caused by N. tenuis on tomato plants. Nesidiocoris tenuis preferred sesame over tomato plants (except when food was provided only on the tomato plant) and the upper part of the plants, whereas M. pygmaeus preferred tomato to sesame plants (except when food was provided only on the sesame plant) and had no preference for a plant part. Combination of predators N. tenuis and M. pygmaeus allows for better coverage of cultivated plants in terms of occupation of different plant parts and better regulation of T. absoluta populations. Sesamum indicum is a potential companion plant that can be used to significantly reduce N. tenuis damage to tomatoes., Competing Interests: The authors have declared that no competing interests exist.

Movement of insect pests between spatially subdivided populations can allow them to recolonize areas where local extinction has occurred, increasing pest persistence. Populations of woolly apple aphid (Eriosoma lanigerum [Hausmann]; Hemiptera: Aphididae), a worldwide pest of apple (Malus domestica [Borkhausen]), occur both below- and aboveground. These spatially subdivided subpopulations encounter different abiotic conditions, natural enemies, and control tactics. Restricting movement between them might be an effective management tactic to decrease woolly apple aphid persistence and abundance. We examined this possibility in the field, using sticky barriers to restrict upward woolly apple aphid movement to tree canopies, and in the greenhouse, using mulches and sand amendments to restrict downward movement to roots. In the field, blocking aphid movement up tree trunks did not decrease the number of colonies in tree canopies. Instead, sticky-banded apple trees had higher aphid colony counts late in the study. Earwigs, which are woolly apple aphid predators, were excluded from tree canopies by sticky bands. In the greenhouse, fewer root galls (indicative of aphid feeding) occurred on trees in sandy potting media and on those with mulch (wood chips or paper slurry). Our results suggest that upward movement is less important than other factors that affect aboveground aerial woolly apple aphid population dynamics. In addition, apple orchards planted in sandier soils or with mulches may be partially protected from woolly apple aphid root feeding., Competing Interests: The authors have declared that no competing interests exist.

The emissions of BVOCs from oilseed rape (Brassica napus), both when the plant is exposed to clean air and when it is fumigated with ozone at environmentally-relevant mixing ratios (ca. 135 ppbv), were measured under controlled laboratory conditions. Emissions of BVOCs were recorded from combined leaf and root chambers using a recently developed Selective Reagent Ionisation-Time of Flight-Mass Spectrometer (SRI-ToF-MS) enabling BVOC detection with high time and mass resolution, together with the ability to identify certain molecular functionality. Emissions of BVOCs from below-ground were found to be dominated by sulfur compounds including methanethiol, dimethyl disulfide and dimethyl sulfide, and these emissions did not change following fumigation of the plant with ozone. Emissions from above-ground plant organs exposed to clean air were dominated by methanol, monoterpenes, 4-oxopentanal and methanethiol. Ozone fumigation of the plants caused a rapid decrease in monoterpene and sesquiterpene concentrations in the leaf chamber and increased concentrations of ca. 20 oxygenated species, almost doubling the total carbon lost by the plant leaves as volatiles. The drop in sesquiterpenes concentrations was attributed to ozonolysis occurring to a major extent on the leaf surface. The drop in monoterpene concentrations was attributed to gas phase reactions with OH radicals deriving from ozonolysis reactions. As plant-emitted terpenoids have been shown to play a role in plant-plant and plant-insect signalling, the rapid loss of these species in the air surrounding the plants during photochemical pollution episodes may have a significant impact on plant-plant and plant-insect communications., Competing Interests: WJFA was in receipt of a Biotechnology and Biological Sciences Research Council (https://bbsrc.ukri.org/)/Ionicon Analytik GmbH (https://www.ionicon.com/) Industrial CASE studentship. Award number BB/I015442/1. This does not alter our adherence to PLOS ONE policies on sharing data and materials.