This scouting session for our day-neutral organic strawberry project at the West Madison Agricultural Research Station (WMARS) was conducted Friday, August 4th in the morning. Field conditions during collections were sunny, windy, and warm.
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|
Tarnished plant bugs: This week, the abundance of tarnished plant bug adults and nymphs was significantly reduced. Nymphs were found on only 1 in 25 flower clusters, and adults were found on just under 20% of flower clusters. This is following three whole-patch sprays of Pyganic 1.4 EC at a rate of 50 fl. oz/acre by backpack sprayer on the evenings of 7/17/23, 7/25/23, and 7/31/23. For more information on Pyganic and our methods of management, please refer to last week’s article. Given the effective reduction in TPB amounts, the improved condition of ripening berries, and the observed reduction in beneficial and pollinator counts, we will refrain from spraying Pyganic this week, and will rely on the next scouting report and field observations to inform future management decisions.
Two-spotted spider mites: No two-spotted spider mites were observed during scouting this week. We suspect that splashback from last week’s heavy rainfall, 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 2% of flower clusters this week. Flea beetles and Japanese beetles were few and far between, and did not seem to be actively feeding on leaves.
Following last week’s third application of Pyganic, the number of both pests and beneficial insects appear to be significantly reduced. In organic production, the decision to spray must weigh both the role of beneficial insects in providing biological control and the need to spray insecticides for pest insects that reach an established economic threshold. In this case, because TPB is a serious pest of day-neutral strawberry, we made the hard decision to spray Pyganic a total of three times to reduce TPB populations, knowing that we would likely see a reduction in beneficial insects such as predatory mites, lady beetles, and minute pirate bugs (Orius bugs).
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 reduced to 3 of 10 sampled plants. We did, however, notice an abundance of Goldenrod soldier beetles (Fig 1) on both leaves and flowers. These beneficial insects are known to pollinate various flowers, and also are predators of some pests. Pollinator observations also yielded low counts, with an especially notable reduction in syrphid fly abundance. This may, however, have also been due to windy conditions during both sampling dates this week. We have noted that solitary bees, which have comprised the majority of our observed pollinators this year, do not seem to mind the wind, but syrphid flies are less present on windy days in our field.
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|
Phomopsis leaf blight (Phomopsis obscurans): The observed incidence of Phomopsis leaf blight is still stable at 6% of sampled plants this week. Diseased plants show slight enlargement of lesions, but do not appear to be in serious decline. We did not observe signs of Common leaf spot (Mycospharella fragariae) or fruit with Anthracnose (Colletotrichum fragariae) in our sampled plants this week. We did note, however, that several fruit harvested this week displayed firm, sunken, tan-to-brown lesions consistent with anthracnose (Fig 2). We will continue to monitor rotten fruit during twice-weekly harvests, as well as during scouting and field walkthroughs.
Incubated samples of collapsed plants are still being processed. We have noted, however, that some collapsed plants show poor root establishment, as they were planted too shallow (i.e. the entire crown was above the soil line). This may have contributed to decline as these plants endured hot and dry conditions last week, during the critical stage of fruit development.
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, Strawberries.