Amblyseius swirksii Athias-Henriot for Control of Arthropod Pests in Woody Ornamental Propagation

View the project final report

Commodities

• Additional Plants: ornamentals

Practices

• Crop Production: biological inoculants
• Education and Training: extension, on-farm/ranch research
• Pest Management: biological control

Clean product is paramount at the propagation stage of woody ornamental production. Since pest problems in propagation can follow the plants through subsequent stages of production, propagators selling infested stock can easily lose customers who will look elsewhere for high quality material. Therefore, an opening exists to gain more widespread acceptance of biological control management techniques in the woody ornamental nursery industry by targeting propagators. We propose a series of experiments to evaluate the efficacy of Amblyseius swirskii Athias-Henriot for sustainable pest management in greenhouse and outdoor woody ornamental propagation. Amblyseius swirskii is a predatory mite that does well in hot, humid climates found in the southeast (Lee and Gillespie 2011, Hewitt et al. 2015). It is a generalist mite that can feed on thrips, whitefly, spider, eriophyid and broad mites (Calvo et al. 2015). In addition to its broad range of arthropod hosts, A. swirskii can survive and reproduce on pollen resources, which can aid in maintaining populations in plant stock when pest pressure is low (Goleva and Zebitz 2013). It can establish on mock orange, Murraya paniculata (L.) Jack (Juan-Blasco et al. 2012) and citrus (Palevsky et al. 2003), suggesting it may be an effective option in other woody ornamental trees and shrubs. These attributes make A. swirskii a promising biological control agent in woody ornamental nurseries, a production system which can be complicated to manage owing to its diversity of crops and grower resistance to non-traditional pest management approaches.

We will compare a biological control program using A. swirskii to our conventional scouting/pesticide rotation. We will evaluate the effectiveness A. swirskii introduction/establishment methods as well as the cost involved for biological control and conventional methods in resources and time. This project will produce data on the efficacy of A. swirskii in woody ornamental propagation and inform future research studies and extension programs to optimize the integration of biological control into container and field nursery production in the southeast. In addition to directly serving the needs of woody ornamental producers the SSARE region, this research has a potential to impact woody ornamental production systems across the United States.

We will evaluate the following uses of A. swirskii in the summer of 2016 and 2017.

1. Efficacy of A. swirskii on propagated cuttings of Hydrangea cultivars with different leaf trichome densities. The goal of this objective is to determine whether A. swirskii application in propagated cuttings performs equally well on plants with different leaf trichome densities. Hydrangea spp. cultivars with trichome densities ranging from none to > 100 per 0.5 in2 have been identified by the Alexander lab. This trial will work to aid in our prediction of which plants on which A. swirskii will perform best.
2.  Comparison of banker plants, predator refuges and supplemental feeding in greenhouse propagation. The goal of this objective is to determine whether the use of banker plants, refuge plants and/or supplemental feeding improves the efficacy of A. swirskii in woody ornamental propagation. Two methods of applying predatory mites include broadcast spreading across the crop or introduction of populations on banker plants, which allow the predators to naturally disperse across the crop. In the first treatment, A. swirskii will be applied across the flats at a rate of 5 mites/sq foot and a pest-free flowering ornamental pepper (Capsicum annuum 'Explosive Ember') will be placed in the center of the plot as an alternative pollen producing host (1 plot = 4 flats and one pepper). In a second treatment, a banker plant of flowering pepper will be placed in the center of the flats with 5 female A. swirskii applied to the plant 2 weeks in advance to initiate colony development. Two additional treatments will include: a plot with 5 mites/sq ft applied but no pepper plant to act as a refuge or banker and an equivalent plot with a pollen supplement (Nutrimite, BioBest USA Inc. or other suitable pollen alternative).
3. Optimal method for incorporating A. swirskii into outdoor woody propagation beds. This experiment will be performed in outdoor propagation beds at Herd Farms Nursery, Belvidere, TN. Propagation beds will be divided into treatment units: (1) conventional production (2+ miticide treatments per season) (2) beds with 5 predatory mites/sq ft applied directly to cuttings and (3) beds with 5 predatory mites/sq ft applied directly to cuttings with supplemental pollen feeding to aid in population establishment.
4. Pre-treatment of stock plants with A. swirskii. Predatory mites will be applied to red maple stock plants at Herd Nursery Farms at a rate of 5 mites/square foot of canopy two weeks prior to propagation. Prior to sticking, 10 cuttings from each predator inoculated and control stock plants will be evaluated for the presence of predatory mites and pests. Plant material will be propagated using standard methods. The results of this study will determine whether inoculating stock plants with predators will carry the population over into propagation and through the misting process. It will also determine whether such a method can provide pest control at a lower cost than broadcast applications directly onto the beds.

   Evaluations. Predator and pest insect counts (broad mite, thrips, spider mite, whitefly) will be made at 2 week intervals in all trials. At the end of the evaluations, new growth of plants will be measured on 50 randomly selected rooted cuttings in all experimental beds. Growth measurements will be analyzed by analysis of variance. Count data for predators and prey will be analyzed with a generalized linear model with a log link and negative binomial distribution.