This scouting session for our day-neutral organic strawberry project at the West Madison Agricultural Research Station (WMARS) was conducted Wednesday, August 30th in the afternoon. Field conditions during collections were warm and sunny.
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|
|8/30/2023||0||0.02 ± 0.02||0.16 ± 0.07||0.57 ± 0.12||0||0|
Tarnished plant bugs: This week, the number of tarnished plant nymphs (Fig 1) rose sharply to 57% of flower clusters, while adults again stabilized at roughly 1 in 10 flower clusters. This week’s abundance of nymphs is again well above the economic threshold of 1 in 4 flower clusters. This most recent influx of TPB, which began the week of 8/18/2023, did result in a sharp increase in catfaced fruit during harvest this week.
This season, we have sprayed Pyganic 1.4 EC on 7/17/23, 7/25/23, 7/31/23, 8/16/23, 8/21/23, and 8/31/23. For more information on our decision to spray and methods, please refer to this past article. We scouted early this week, which prompted the Pyganic spray on the evening of 8/31/23. We will evaluate TPB abundance again on Friday 9/8/2023, and suspect that this is their last influx in the field.
This week, two-spotted spider mites were not observed in the field. The number of thrips decreased again, perhaps following our repeated Pyganic sprays. Flea beetles were not noted this week.
Orius bugs were found on 2 of 10 sampled plants this week. Predatory Mites and lady beetles were not present on the 10 randomly selected plants, though several lady beetle adults were observed during normal scouting and field walkthroughs.
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||Black Root Rot|
|6/30/2023||0||0.01 ± 0.02||0||0||0||0||0|
|7/07/2023||0.01 ± 0.02||0.08 ± 0.04||0||0||0||0||0|
|7/14/2023||0.01 ± 0.01||0.06 ± 0.04||0||0||0||0||0|
|7/21/2023||0.01 ± 0.01||0.07 ± 0.04||0||0||0||0||0|
|7/28/2023||0||0.08 ± 0.04||0||0||0||0||0|
|8/04/2023||0||0.06 ± 0.04||0||0||0||0||0|
|8/11/2023||0||0.08 ± 0.04||0||0||0||0||0|
|8/18/2023||0||0.09 ± 0.05||0||0||0||0||0|
|8/25/2023||0.02 ± 0.02||0.09 ± 0.04||0||0||0||0||0|
|8/30/2023||0.02 ± 0.02||0.04 ± 0.03||0||0||0||0||0.06 ± 0.04|
Last week, the diagnostic clinic confirmed the presence of both Pythium and Rhizoctonia species on our collapsed plant sample. These two species belong to the pathogen complex that causes Black root rot (Fig 2) in strawberry systems. While we traditionally see this disease in wetter seasons, we hypothesize that the pathogens came in on planting material and under the drought and heat stress this season, plants weakened by these pathogens began to collapse. The symptoms that we have observed in the field include the collapse of older leaves, stunted new leaves, and small, seedy fruit. Plants often display black root lesions and decay when impacted by black root rot, though we have not yet observed this in our field.
The observed incidence of Phomopsis leaf blight (Phomopsis obscurans) decreased this week to 4% of sampled plants. Symptoms continue to be minor, and notably often appear on the older leaves of collapsing plants. Common leaf spot (Mycospharella fragariae) was again found on 2% of sampled plants this week, with symptoms also appearing on the older leaves of weakened plants.
Berries with Anthracnose (Colletotrichum fragariae) and Botrytis gray mold (Botrytis cinerea) were again more rare during harvest this week, perhaps due to the dry weather conditions. More information about fruit rots of strawberry can be found in this article, while fungal foliar diseases can be found here.
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.