This scouting session for our day-neutral organic strawberry project at the West Madison Agricultural Research Station (WMARS) was conducted Friday, July 28th in the morning. Field conditions during collections were sunny, hot, and breezy. Strong storms moved through the area during the previous night, and the field was still wet.
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 ± 0.01||0.14 ± 0.07||0.28 ± 0.09||0||0.05 ± 0.04|
Tarnished plant bugs: For the past 2 weeks, TPB numbers have been at or above the economic spray threshold. To date, we have sprayed Pyganic 1.4 EC at a rate of 50 fl. oz/acre by backpack sprayer to cover the entire patch on 7/17/23 and 7/25/23. We applied the product in the late evening to avoid pollinators. As a result, the number of adults and nymphs decreased by 50% and 75%, respectively, after the first spray. Observed counts have since stabilized at 1 adult per 10 flower clusters and 1 nymph per 4 clusters. The number of nymphs is still just at the threshold for chemical management, so we sprayed Pyganic for a third time on the evening of Monday 7/31/23.
Pyganic: We spray Pyganic in the evening to avoid pollinators, as well as to maximize efficiency of the spray, as the active ingredients in Pyganic are degraded by UV light. Pyganic contains a mixture extracted from the flowers of Tanacetum cinerariifolium (Chrysanthemum) which contains six naturally occurring metabolites of insecticidal quality (cumulatively called pyrethrins). Pyganic is in the IRAC group 3A, which contains pyrethrins and the non-OMRI pyrethroids which are synthetic compounds that are very similar in structure to the pyrethrins. Pyganic should not be used more than ten times in a season with a minimum interval between applications of 3 days except in cases of extreme pest pressure (see the label for more info). The PHI (Pre-harvest interval) is 0 day and the REI (restricted entry interval) is 12 hours. The insecticide works quickly and effectively by disrupting insect nervous system function, but is of minor toxicity to mammals due to differences in physiology and metabolism. As with many organic insecticides, Pyganic is a broad spectrum insecticide, and will kill any arthropods in the canopy at the time of application including pests, pollinators, and beneficials. As part of our IPM regimen, we must weigh the potential benefits of spraying for TPB with the potential harm of killing lady beetle, Orius and predatory mite populations as well. In organic production, Pyganic is recommended for TPB management as well as other insecticides including Azadirachtin, which has shown control in some studies. In conventional farming, Brigade and Danitol for pyrethroids and Actara and Assail for neonicotinoids have shown good/excellent efficacy against Tarnished Plant Bug.
Two-spotted spider mites: The number of mites this week dropped again sharply, with only 3% of plants harboring these pests. Splash-back from heavy rainfall the night before scouting, as well as Pyganic applications likely contributed to the reduction in mite incidence.
Thrips: The amount of thrips was again low this week, with just one thrip observed on the 160 sampled flower clusters. Similar to the two-spotted spider mites, heavy rainfall and Pyganic applications likely reduced their numbers.
Flea beetles: The number of flea beetles remains relatively constant with little-to-no signs of damage.
Japanese beetles presence seems to have decreased with the more rigorous management of smartweed and other nearby host weeds, as well as Pyganic applications.
This week, the number of some pests and beneficial insects again may have been impacted by our decision to spray Pyganic on 7/25/23. 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 insect pests 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).
Predatory Mites: Predatory mites were not observed this week, which is likely due to the applications of Pyganic and the very low numbers of two-spotted spider mites that they feed on. More information on these mites can be found in this article.
Lady beetles: No lady beetle larvae or adults were found on our ten sampled plants this week. We believe that the large amount of larvae observed earlier in the season pupated and became more mobile prior to our decision to spray Pyganic, but adult numbers may have been impacted by the Pyganic spray. During field walkthroughs, some adult lady beetles have been observed on our plants, including the native pink spotted lady beetle (Fig 1).
Orius bugs: The abundance of Orius bugs this week was even higher than last week, with individuals on 6 of 10 sampled plants and many of the tapped flower clusters. More information on these insects can be found in last week’s report.
Pollinator Observations: Pollinators continue to move through our field, with several small green bees and small dark bees (Fig 2) and syrphid flies being counted during our observation sessions.
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|
Phomopsis leaf blight (Phomopsis obscurans): The observed incidence of Phomopsis leaf blight again remained relatively constant at 8% of sampled plants this week, with infection still in early stages. We did not observe signs of Common leaf spot (Mycospharella fragariae) or fruit with Anthracnose (Colletotrichum fragariae) in our sampled plants this week.
During field walkthroughs, we have observed a few more plants in varying stages of collapse (Fig 3). We plan to sample these plants again next week for possible crown and root pathogens, and will provide updates 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, Strawberries.