This scouting session for our day-neutral organic strawberry project at the West Madison Agricultural Research Station (WMARS) was conducted Friday, August 25th in the afternoon. Field conditions during collections were warm, cloudy, and humid.
This project aims to evaluate the effects of four different film-based mulches (black, white, and reflective plastic mulches, and paper mulch) on strawberry production in an annual, day-neutral system. This system-wide field trial is evaluating yield, fruit quality, pest pressure, and economic feasibility of this regionally novel system for strawberry production. Our field was planted on the 8th of May, and plants are still developing with flowers and runners removed as they appear, with runner removal continuing indefinitely and flower removal having ceased the week of July 3rd. Routine harvests began the week of July 24, and have continued through the season. We are irrigating for short intervals several times a week, with fertigation occurring once weekly at the rate of 5 lbs N per acre.
Sampling Methods: 160 plants (40 plants per mulch treatment) were randomly selected and assessed for insect pest and disease presence and respective pressure using the University of Wisconsin Extension BioIPM Strawberry Workbook. At each sampling point, two leaves per plant were tapped into a white tray, and any thrips or tarnished plant bugs were counted. Since 07/07/2023, thrips and tarnished plant bugs have been sampled by tapping one flower cluster per sampled plant into a tray. Mites were assessed on an incidence-basis: plants were evaluated for mite presence on older foliage and crowns. Each plant was also inspected for foliar disease symptoms. Declining or dead plants are removed and assessed in the laboratory for biotic causal agents.
Table 1. The incidence and average number of insects observed per plant in day-neutral strawberries during weekly sampling.
|Date||Mites (Incidence)||Thrips (Average per two leaves* or one flower cluster)||Tarnished Plant Bug Adults (Average per two leaves* or one flower cluster)||Tarnished Plant Bug Nymphs (Average per two leaves* or one flower cluster)||Spotted- wing Drosophila (Incidence)||Flea Beetle (Average per plant)|
|6/9/2023||0.21 ± 0.06||0.07 ± 0.07 *||0.03 ± 0.03 *||0||0||0|
|6/15/2023||0.21 ± 0.06||0.13 ± 0.1 *||0.01 ± 0.01 *||0||0||0|
|6/26/2023||0.51 ± 0.08||0.09 ± 0.07 *||0.20 ± 0.07 *||0||0||0|
|6/30/2023||0.52 ± 0.08||0.17 ± 0.10 *||0.06 ± 0.04 *||0||0||0|
|7/07/2023||0.52 ± 0.08||0.05 ± 0.05 *||0.03 ± 0.03 *||0||0||0.09 ± 0.05|
|7/14/2023||0.35 ± 0.08||0.04 ± 0.05||0.21 ± 0.09||1.09 ± 0.15||0||0.09 ± 0.04|
|7/21/2023||0.14 ± 0.08||0||0.10 ± 0.05||0.29 ± 0.09||0||0.04 ± 0.03|
|7/28/2023||0.03 ± 0.02||0.01 ± 0.01||0.14 ± 0.07||0.28 ± 0.09||0||0.05 ± 0.04|
|8/04/2023||0||0.02 ± 0.02||0.19 ± 0.07||0.04 ± 0.03||0||0.01 ± 0.01|
|8/11/2023||0||0.01 ± 0.02||0.26 ± 0.08||0.11 ± 0.06||0||0.01 ± 0.02|
|8/18/2023||0||0.01 ± 0.01||0.13 ± 0.05||0.39 ± 0.09||0||0.01 ± 0.01|
|8/25/2023||0||0.09 ± 0.05||0.14 ± 0.06||0.44 ± 0.12||0||0.02 ± 0.02|
Tarnished plant bugs: This week, the number of tarnished plant nymphs rose slightly again to 44% of flower clusters, while adults stabilized at roughly 1 in 10 flower clusters. This follows alfalfa harvest on the research station earlier this week. Most nymphs still appear to be just-hatched following egg-laying over the past two weeks. This week’s abundance of nymphs is again well above the economic threshold of 1 in 4 flower clusters.
This season, we have sprayed Pyganic 1.4 EC on 7/17/23, 7/25/23, 7/31/23, 8/16/23, and 8/21/23. For more information on our decision to spray and methods, please refer to this past article. We sprayed again on the evening of 8/31/23, and suspect that this is the last influx of TPB in the field.
This week, two-spotted spider mites were not observed in the field. There was a notable increase in thrips, which were found on roughly 1 in 10 flower clusters. This follows a two-month downward trend in their abundance, and could indicate a late-season surge in their numbers. Flea beetles were noted on only 2% of flower clusters this week.
This week, we have continued to observe many pollinators in the field, especially bumblebees. We have anecdotally noted a decrease in the amount of syrphid flies following Pyganic sprays, though their numbers do return within a few days.
Predatory Mites were not present on the 10 randomly selected plants this week. A lady beetle adult was observed on 1 of 10 plants, and the number of Orius bugs this week was increased to 4 of 10 sampled plants.
Table 2. The incidence of diseases observed per plant in day-neutral strawberries during weekly sampling.
|Date||Common Leaf Spot||Phomopsis Leaf Blight||Verticillium Wilt||Anthracnose||Leaf Scorch||Neopest- alotiopsis|
|6/30/2023||0||0.01 ± 0.02||0||0||0||0|
|7/07/2023||0.01 ± 0.02||0.08 ± 0.04||0||0||0||0|
|7/14/2023||0.01 ± 0.01||0.06 ± 0.04||0||0||0||0|
|7/21/2023||0.01 ± 0.01||0.07 ± 0.04||0||0||0||0|
|7/28/2023||0||0.08 ± 0.04||0||0||0||0|
|8/04/2023||0||0.06 ± 0.04||0||0||0||0|
|8/11/2023||0||0.08 ± 0.04||0||0||0||0|
|8/18/2023||0||0.09 ± 0.05||0||0||0||0|
|8/25/2023||0.02 ± 0.02||0.09 ± 0.04||0||0||0||0|
Phomopsis leaf blight (Phomopsis obscurans): The observed incidence of Phomopsis leaf blight stabilized at 9% of sampled plants this week with persistently minor symptoms. Berries with Anthracnose (Colletotrichum fragariae) lesions continue to appear on harvested fruit (Fig 1), though we did note a decrease in rotten fruit this week.
This week, there was a very slight increase in the number of plants with the foliar symptoms of common leaf spot (Mycospharella fragariae) (Fig 2), which was first noted in July. We have not yet seen another fruit with Botrytis gray mold this week. More information about fruit rots of strawberry can be found in this article, while fungal foliar diseases can be found here.
This past week, we gathered tissue samples from collapsed strawberry leaves, runners, fruit, crowns, and roots for signs of disease. We also sent a collapsed plant to the UW Plant Diagnostic Clinic for simultaneous testing. The diagnostic clinic confirmed the presence of both Pythium and Rhizoctonia species, which make up the pathogen complex that causes Black root rot (Fig 3)in strawberry systems. Symptoms can include the collapse of older leaves, with new leaves appearing stunted. Plants may have small, seedy fruit, and produce few runners. Roots will appear black and decay over time.
Funding for this project was provided by USDA-NIFA ORG award # 2021-51106-35490.This article was posted in Berries and tagged Ariana Abbrescia, Christelle Guédot, day-neutral strawberry, DNS, DNS Organic, Jarret Miles-Kroening, Leslie Holland, Organic Day-Neutral Strawberry Production, organic strawberries.