This scouting session for our day-neutral organic strawberry project at the West Madison Agricultural Research Station (WMARS) was conducted Friday, August 18th in the afternoon. Field conditions during collections were sunny, cool, 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. Berries are developing steadily, with routine harvests beginning the week of July 24. 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|
Tarnished plant bugs: This week, the number of tarnished plant bug adults fell to roughly 1 in 10 flower clusters. The number of nymphs, however, rose sharply to over 1 in 3 flower clusters. These nymphs were quite small (Fig 1, far left), and were likely the result of egg-laying during last week’s notable influx of TPB adults in the field. This week’s abundance of nymphs is 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, and 8/16/23. For more information on our decision to spray and methods, please refer to this past article. Due to this week’s influx of nymphs, as well as the setting of vulnerable young fruit, we sprayed Pyganic again on the evening of Monday 8/21/23. We suspect that as the season progresses, TPB pressure will start to decrease naturally.
This week, two-spotted spider mites were not observed in the field. Thrips and flea beetles were noted on only 1% of flower clusters this week.
This week, we have noted a significant increase in the amount of pollinators in the field. Many bumblebees and syrphid flies can be seen visiting strawberry flowers and nearby smartweed plants (Fig 2).
Predatory Mites were not present on the 10 randomly selected plants this week. A lady beetle adult was observed on 1 of 10 plants; they seem to be more present throughout the field this week on plants and nearby weeds. The number of Orius bugs this week decreased slightly to 2 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|
Phomopsis leaf blight (Phomopsis obscurans): The observed incidence of Phomopsis leaf blight very slightly increased to 9% of sampled plants this week. Diseased plants still do not appear to be in serious decline. We are continuing to see more Anthracnose (Colletotrichum fragariae) lesions on harvested fruit (Fig 3A). We harvest the entire field on Mondays and Thursdays, which does not leave mature fruit to be sampled during our Friday scouting sessions. For this reason, we have not noted Anthracnose fruit lesions in our scouting data collection. During harvest, we also noted our first strawberry with what appears to be Botrytis gray mold (Fig 3B). This is characterized by gray, fuzzy mold growth on strawberry fruits. More information about fruit rots of strawberry can be found in this article.
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.
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.