This scouting session for our day-neutral organic strawberry project at the West Madison Agricultural Research Station (WMARS) was conducted Friday, August 11th in the afternoon. Field conditions during collections were sunny, hot, and windy.
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||0.11 ± 0.06||0.26 ± 0.08||0||0.01 ± 0.02|
Tarnished plant bugs: This week, we decided to trial a new method of reducing TPB numbers in our field. In several strawberry operations, modified vacuums have been used to successfully remove TPB from strawberry plants without the need for spraying1-2. We modified a bug vacuum (Fig 1) by attaching a funnel to the tip of the vacuum, and used this attachment to vacuum whole flower clusters and plants throughout the field. We vacuumed the whole field in the late afternoon on Friday 8/11 prior to scouting. It took around one hour to vacuum the field, which is roughly the amount of time it takes to spray Pyganic. Each block of four rows yielded ~40 TPB adults, which translates to roughly 1 TPB adult per 4-8 flower clusters. Surprisingly, no pollinators were captured using this method, perhaps due to the strong winds. We did notice that the strawberry petals did frequently clog the filter on our vacuum, which may have reduced suction and the amount of captured TPB.
Despite these efforts to reduce TPB in the field, the abundance of tarnished plant bug adults significantly increased this week to above the economic threshold of 1 in 4 flower clusters, while the number of nymphs was slightly reduced to 1 in 10 flower clusters. Following three whole-patch sprays of Pyganic 1.4 EC on 7/17/23, 7/25/23, and 7/31/23, we decided not to spray last week. Given this increase in adult numbers, as well as the development of vulnerable new fruit, we have decided to spray Pyganic again on the evening of 8/16/23. For more information on Pyganic and our methods of management, please refer to last week’s article.
Two-spotted spider mites: Again, no two-spotted spider mites were observed during scouting this week. We suspect that splashback from heavy storms earlier this month, the previous abundance of predatory mites, as well as the successive Pyganic applications likely contributed to this reduction in mite incidence.
Similarly, thrips were noted on only 1% of flower clusters this week. Flea beetles and Japanese beetles were again not prevalent.
Despite the lack of Pyganic spraying this past week, the number of beneficial insects and pollinators have not yet rebounded to pre-spray numbers. In addition to the sprays, it could also be that at this time, some species may start to decline naturally. We did notice a sharp increase in pollinator abundance in the late afternoons this week. Visitors included butterflies, honey bees, bumblebees, and syrphid flies (Fig 1). Accordingly, we will move our pollinator observations from the early morning to late afternoon this upcoming week to assess any changes in the composition or number of visiting pollinators.
Both Predatory Mites and Lady beetles were not present on the 10 randomly selected plants this week, though lady beetle adults continue to be observed on and around strawberry plants and weeds, and on sticky traps in the field. The number of Orius bugs this week was stable at 3 of 10 sampled plants. Pollinator counts were quite low this week, perhaps again due to wind, cooler temperatures, or the early time of day.
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|
Phomopsis leaf blight (Phomopsis obscurans): The observed incidence of Phomopsis leaf blight very slightly increased to 8% of sampled plants this week. Diseased plants do not appear to be in serious decline, with only a few foliar lesions on older leaves. We did not observe signs of Common leaf spot (Mycospharella fragariae) or fruit with Anthracnose (Colletotrichum fragariae) in our sampled plants this week, though we again noted a few anthracnose-like lesions during harvest (Fig 2). This week, we’ve noted the collapse of a few more plants. Lab tests so far have not pointed towards a specific pathogenic culprit, but we will continue to sample and monitor as symptoms appear.
Funding for this project was provided by USDA-NIFA ORG award # 2021-51106-35490.
(1) Swezey, Sean L., Diego J. Nieto, James R. Hagler, Charles H. Pickett, Janet A. Bryer, and Scott A. Machtley. 2013. “Dispersion, Distribution, and Movement of Lygus Spp. (Hemiptera: Miridae) in Trap-Cropped Organic Strawberries.” Environmental Entomology 42 (4): 770–78. https://doi.org/10.1603/EN12353.
(2) Vincent, Charles, and Roger Chagnon. 2000. “Vacuuming Tarnished Plant Bug on Strawberry: A Bench Study of Operational Parameters versus Insect Behavior.” Entomologia Experimentalis et Applicata 97 (3): 347–54. https://doi.org/10.1046/j.1570-7458.2000.00749.x.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, Strawberries.