Soil Solarization to Eradicate Soilborne Phytophthora spp. in Container Nurseries with Surface Gravel1

To describe the effect of soil solarization in the presence of a gravel layer on the soil surface of container nurseries, we investigated belowground temperatures and soil water potential during solarization with different thicknesses of a surface gravel layer (2.5 cm, 7.5 cm, or no gravel) (1 in, 3 in, or no gravel) in relation to survival of soilborne Phytophthora spp. inoculum. In field trials conducted for 4 weeks with Phytophthora ramorum Werres and Phytophthora pini Leonian in San Rafael, California and with P. pini in Corvallis, Oregon, infested rhododendron leaf inoculum was placed on the surface, and at 5 cm (2 in) and 15 cm (6 in) below the surface. In solarized plots with thicker layers of gravel, inoculum buried in the soil layer was killed in shorter treatment periods by higher elevated temperatures. Inoculum at the surface and within the gravel layer was also killed, but showed greater tolerance to heat under the lower water potential conditions as compared to the soil layer. P. pini has a significantly longer survival in heat than P. ramorum, allowing it to serve as a conservative surrogate for P. ramorum in testing solarization outside the quarantine facility. This study demonstrates how presence of a gravel layer influences soil solarization effectiveness in reducing Phytophthora inoculum survival. Index words: Phytophthora ramorum, Phytophthora pini, soil disinfestation, disease management, soil temperature, soil water potential, ornamentals. Species used in this study: Phytophthora ramorum Werres, de Cock & Man in't Veld, Phytophthora pini Leonian.

Watering Station Best Management Practices for Container Nurseries

Watering stations are specialized irrigation structures where plants are watered immediately after transplanting. Water not retained by the container substrate as well as water falling between containers becomes runoff. This runoff can contain sediment and nutrients, such as nitrogen and phosphorus, that can impact natural waters if not managed according to Best Management Practices (BMPs). The purpose of this new 3-page fact sheet is to provide examples of how runoff from watering stations at two nurseries was managed after implementation of the BMP. Written by Tom Yeager and published by the UF/IFAS Environmental Horticulture Department.https://edis.ifas.ufl.edu/ep590

Biology and Management of Galinsoga (Galinsoga quadriradiata) in Ornamental Crop Production

Galinsoga (Galinsoga quadriradiata) is an erect (upright), herbaceous, short-lived warm-season annual weed in Florida landscapes, container nurseries, and other agricultural production systems. In nurseries and landscapes, galinsoga can be a troublesome weed, but it has been utilized by some cultures for food or medicinal purposes. This new 5-page article is written for green-industry professionals and others to aid in the identification and management of galinsoga in and around ornamental plants. Written by Thomas Smith, Chris Marble, Shawn Steed, and Nathan Boyd, and published by the UF/IFAS Environmental Horticulture Department. https://edis.ifas.ufl.edu/ep593

Biology and Management of Garden Spurge (Euphorbia hirta) in Ornamental Crop Production

Garden spurge is a prostrate (low-growing), herbaceous, short-lived, warm-season annual weed commonly found growing in Florida landscapes, container nurseries, and other agricultural production areas. This article is written for green industry professionals and others to aid in the identification and management of garden spurge in and around ornamental plants.

A Review of Common Liverwort Control Practices in Container Nurseries and Greenhouse Operations

Common liverwort (Marchantia polymorpha) is a primitive, spore-bearing bryophyte that thrives in containerized ornamental crop propagation and production environments. It is one of the major weed problems in container nurseries and greenhouses because it competes with ornamental plants for soil/growing medium, nutrients, water, space, and oxygen within the container. As a result, its presence can reduce the overall quality and market value of the ornamental crop. Once established in nurseries and greenhouses, it spreads rapidly because of its ability to propagate both asexually and sexually. Currently, no effective methods of controlling common liverwort in container production systems are available because a significant knowledge gap exists. Therefore, research is needed to determine whether organic mulches (types, depths, moisture holding capacity, and particle size), biopesticides, and strategic placement of fertilizers within containers suppress or inhibit common liverwort growth and development. In addition, newer chemicals (both synthetic and organic) and combinations need to be tested on different growth stages of common liverwort. The objective of this review was to summarize previous and current research related to common liverwort control in container production, and to identify areas where additional research is needed either to improve current control methods or to develop new ones.

Hazard Analysis for Phytophthora Species in Container Nurseries: Three Case Studies

Phytophthora species cause crop losses and reduce the quality of greenhouse and nursery plants. Phytophthora species can also be moved long distances by the plant trade, potentially spreading diseases to new hosts and habitats. Phytosanitary approaches based on quarantines and endpoint inspections have reduced, but not eliminated, the spread of Phytophthora species from nurseries. It is therefore important for plant production facilities to identify potential sources of contamination and to take corrective measures to prevent disease. We applied a systems approach to identify sources of contamination in three container nurseries in Oregon, California, and South Carolina. Surface water sources and recaptured runoff water were contaminated with plant pathogenic species at all three nurseries, but one nursery implemented an effective disinfestation treatment for recycled irrigation water. Other sources of contamination included cull piles and compost that were incorporated into potting media, infested soil and gravel beds, used containers, and plant returns. Management recommendations include preventing contact between containers and contaminated ground, improving drainage, pasteurizing potting media ingredients, steaming used containers, and quarantine and testing of incoming plants for Phytophthora species. These case studies illustrate how recycled irrigation water can contribute to the spread of waterborne pathogens and highlight the need to implement nursery management practices to reduce disease risk.

On-farm Evaluations of Wood-derived, Waste Paper, and Plastic Mulch Materials for Weed Control in Florida Container Nurseries

Mulches have been evaluated extensively as a weed management tool in container plant production, but most research has focused on loose-fill wood-derived mulch materials, such as pine bark or wood chips. In this experiment, pine (mixed Pinus sp.) bark (PB), shredded hardwood (HW), and pine sawdust were evaluated for weed control and crop response both alone and in combination with a guar gum tackifier alongside a plastic film mulch, a paper slurry mulch, and the paper slurry mulch + PB and compared with a nonmulched, nontreated control and a single application of preemergence herbicide (oxyfluorfen + pendimethalin). Mulch materials were applied to nursery containers ranging from 7 to 25 gal at two different nurseries and at two research centers in central Florida in 2017 and 2018. Results showed that the plastic mulch provided more than a 90% reduction in hand weeding time and weed weight over a 6-month period, and similar control was achieved with PB, paper slurry + PB, and the HW treatment (64% to 91% reduction in weeding time and weed weight). No growth differences were observed with any mulch treatment in any species evaluated including ligustrum (Ligustrum japonicum), Chinese elm (Ulmus parvifolia), or podocarpus (Podocarpus macrophyllum).

Biology and Management of Common Chickweed (Stellaria media) in Ornamental Crop Production

Chickweed is a common cool-season annual weed in Florida landscapes, container nurseries, home gardens, and other agricultural production systems. This new 5-page article is written for green industry professionals and others to aid in the identification and management of chickweed in and around ornamental plants. Written by Yuvraj Khamare, Chris Marble, Nathan Boyd, and Shawn Steed and published by the UF/IFAS Environmental Horticulture Department. https://edis.ifas.ufl.edu/ep577

Biology and Management of Doveweed (Murdannia nudiflora) in Ornamental Crop Production

Doveweed is a common warm-season annual weed in Florida landscapes, container nurseries, and other agricultural production systems. This new 5-page article is written for green industry professionals and others to aid in the identification and management of doveweed in and around ornamental plants. Preemergence and postemergence herbicides are covered, as well as basic information on doveweed biology and growth. Written by Yuvraj Khamare, Chris Marble, Nathan Boyd, and Shawn Steed, and published by the UF/IFAS Environmental Horticulture Department. https://edis.ifas.ufl.edu/ep576

Biology and Management of Spanish Needles (Bidens spp.) in Ornamental Crop Production

All eight species of Bidens in Florida are commonly referred to as Spanish needles or beggar-ticks. This document focuses on Bidens alba and B. pilosa, which are common weeds in container nurseries and landscapes in Florida. This 6-page EDIS publication, written by Yuvraj Khamare, Chris Marble, Shawn Steed, and Nathan Boyd and published by the UF/IFAS Environmental Horticulture Department, is designed for landowners, gardeners, horticulturalists, and consumers hoping to learn more about Spanish needle classification and management. http://edis.ifas.ufl.edu/ep572