The risk of exotic and native plants as hosts for four pest thrips (Thysanoptera: Thripinae)

Pre-Sowing Treatments Improve Germinability of South Texas Native Plant Seeds

The incorporation of native plant species is central to restoration efforts, but this is often limited by both the availability of seeds and the relatively low viability and germination rates of commercially available seeds. Although pre-sowing treatments are commonly used to improve germination rates of seeds, the efficacy of these treatments is found to vary across species. In this study, we tested how four pre-sow treatments (physical scarification, acid scarification, cold stratification, and aerated hydropriming) affected the viability and seed germination rates of 12 commercially available plant species native to south Texas and commonly used in restoration efforts. Our results show that the viability of the seeds have a wide range, from 78% to 1.25%. Similarly, the total germination rate ranged from 62% to 0%. We found that pre-sowing treatments accelerated the germination rate in 9 of 12 plant species tested, but the effect varied by treatment. Collectively, our results identify various methods to achieve the best germination rates for native plants of south Texas, to help improve restoration efforts across the region.

Effect of Different Plants on the Growth and Reproduction of Thrips flavus (Thysanoptera: Thripidae)

Simple Summary

Thrips flavus Schrank (Thysanoptera: Thripidae) is a worldwide phytophagous pest in Palearctic Asian and European countries. T. flavus feeds on a wide spectrum of host plants. Thus, understanding its host plant preferences is important for pest control. We tested the development duration, population parameters, and population growth of T. flavus on five species of plants. The intrinsic rate of increase and fecundity was the highest on Cucumis sativus, followed by Glycine max and Capsicum annuum. However, Solanum melongena and Brassica rapa var. glabra were not suitable host plants. These results help to improve our understanding of the population dynamics of T. flavus and should lead to positive measures to control thrips in the field.

Abstract

Host plants play an important role in affecting insect development and reproduction. Understanding the host plant preferences is important for pest control. Thrips flavus Schrank (Thysanoptera: Thripidae) is a worldwide phytophagous pest in Palearctic Asian and European countries. We used a life table analysis to study the development duration, population parameters, and population growth of T. flavus on five plant species, including Solanum melongena (Solanaceae), Capsicum annuum (Solanaceae), Glycine max (Leguminosae), Brassica rapa var. glabra (Cruciferae), and Cucumis sativus (Cucurbitaceae). The results showed that T. flavus can survive and reproduce on Cu. sativus and G. max, which were two potentially suitable host plants. T. flavus preferred to oviposit on Cu. sativus with a shorter duration of development (17.8 days) at 25 °C. Therefore, the host plant was an important factor influencing the development and fecundity of T. flavus populations. These results will improve our understanding of the population dynamics of T. flavus and facilitate the development of more scientific and efficient measures to control thrips.

Selecting native perennial plants for ecological intensification in Mediterranean greenhouse horticulture

Natural control by predators and parasitoids provides an important and often unnoticed ecosystem service to agricultural landscapes by reducing pest populations in crops. The current model of horticultural intensification in south-eastern Spain produces high yields but has also resulted in a landscape almost completely covered by plastic. Promoting natural areas among greenhouses could enhance biodiversity, by being beneficial insects, and reduce pest pressure outdoors. The first step is to ascertain how pests and their natural enemies (NEs) use Mediterranean vegetation for selecting the best plants for pest suppression outdoors. The abundance of the two major horticultural pests, the tobacco whitefly, Bemisia tabaci, and the western flower thrips, Frankliniella occidentalis, together with their NEs, were assayed in 22 flowering perennial plants, which were newly planted in an experimental field surrounded by greenhouses. Eight plant species were identified as the most critical species for sustaining pest populations outdoors. A set of five plant species supported a medium level of pests, and another set of ten plant species supported the lowest level of both pests. Tobacco whitefly occurred in a few plants species, whereas western flower thrips occurred on almost all the plant species studied, and was favoured by the presence of flowers in perennial plants. The results suggest that plant diversity may provide relatively few acceptable host plants for tobacco whitefly than for western flower thrips. NEs were generally collected in plants that also supported abundance of pests, indicating that host/prey availability, more than food resources from flowers, was a stronger predictor of NE abundance in perennial plants. Field trials using the plants with the lowest host acceptance by pests are needed in order to ascertain whether pest abundance outdoors is reduced.

Connecting scales: achieving in-field pest control from areawide and landscape ecology studies

Areawide management has a long history of achieving solutions that target pests, however, there has been little focus on the areawide management of arthropod natural enemies. Landscape ecology studies that show a positive relationship between natural enemy abundance and habitat diversity demonstrate landscape-dependent pest suppression, but have not yet clearly linked their findings to pest management or to the suite of pests associated with crops that require control. Instead the focus has often been on model systems of single pest species and their natural enemies. We suggest that management actions to capture pest control from natural enemies may be forth coming if: (i) the suite of response and predictor variables focus on pest complexes and specific management actions; (ii) the contribution of "the landscape" is identified by assessing the timing and numbers of natural enemies immigrating and emigrating to and from the target crop, as well as pests; and (iii) pest control thresholds aligned with crop development stages are the benchmark to measure impact of natural enemies on pests, in turn allowing for comparison between study regions, and generalizations. To achieve pest control we will need to incorporate what has been learned from an ecological understanding of model pest and natural enemy systems and integrate areawide landscape management with in-field pest management.