This scouting session for our day-neutral organic strawberry project at the West Madison Agricultural Research Station (WMARS) was conducted Friday, July 14th in the morning. Field conditions during collections were sunny, windy, cool, and wet from early morning storms.

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 beginning to develop, with harvest anticipated to begin within two weeks of publication. . 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.

Insect Pests:

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

Two-spotted spider mites: The incidence of mites this week decreased significantly from 52% to 35% of scouted plants. One possible explanation is the early morning heavy rain showers, which could have washed mites from the undersides of leaves from rainfall or bounce-back from mulch. Another explanation is the presence of predatory mites (see below) that feed on TSSM. 

Tarnished plant bugs: This marks the first week after halting flower cluster removals, and the first week of flower cluster tapping to assess TPB and thrip presence. The average amount of tarnished plant bugs adults increased significantly to 1 adult per 5 flower clusters. Most notably, the amount of TPB nymphs, which were not noted at all during last week’s scouting, increased dramatically to over 1 nymph per flower cluster. This is well over the recommended 1 TPB per 4 flower cluster threshold for chemical management. The few berries that have begun to ripen do show signs of catfacing, which is caused by TPB damage (Fig 1). Thus we sprayed Pyganic 1.4 EC at a rate of 50 fl. oz/acre using a backpack sprayer to cover the entire patch on the evening of 7/17/23. We will do this in the evening to avoid pollinators, as well as to maximize efficiency of the spray, as the active ingredients in Pyganic are destroyed by UV light. Pyganic contains a mixture extracted from the flowers of Tanacetum cinerariifolium (Chrysanthemum)which contains six naturally occurring metabolites (cumulatively called pyrethrins). Pyganic is in the IRAC group 3A insecticide that contains pyrethrins and pyrethroids and 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. 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.

Thrips: Unlike tarnished plant bugs, thrip observations slightly decreased this week. We have noted before that windy conditions may have negatively affected their presence in the field. Thus far the numbers remain low and below the economic threshold of 2-10 thrips per blossom or small berry. For more information about thrips, please refer to this previous article.

Flea Beetles: Flea beetle averages remained constant from last week, and no additional damage was observed.

Japanese Beetles: Japanese beetle damage remains inconsistent and low but still present throughout the field, and their presence again seems correlated with the location of nearby smartweed leaves.

Beneficial Insects:

Predatory Mites: Again, 6 of 10 sampled plants had predatory mites. These mites can be more difficult to identify than our other scouted insects, and are characterized by their longer legs, lack of spots, and faster movement than the two-spotted spider mites that they feed on. Predatory mites can provide good biological control of two-spotted spider mites if left untreated. A good way to see if you have enough predatory mites to control the two-spotted spider mites is to count the number you see on leaves. A ratio of one predatory to 10 two-spotted spider mite would indicate that you should obtain adequate control. Because of the lack of injury from two-spotted spider mites and the presence of predatory mites on 60% of the plants, we are not anticipating spraying two-spotted spider mites this week.

Lady beetles: Only 3 of 10 sampled plants harbored lady beetle larvae and/or adults this week. Lady beetles are beneficial insects and should be conserved in agroecosystems to allow them to prey on pest insects such as aphids. For more information on lady beetles, please see this article.

Orius bugs: This week, Orius bugs were very common throughout the field – they were present on nearly every tapped flower cluster. 8 of 10 sampled plants had Orius bugs, many of which were insidious flower bugs (Orius insidiosus). Orius bugs are also known as minute pirate bugs and they are biological control agents that feed as immatures (nymphs) and adults on pest insects such as aphids, leafhoppper nymphs, thrips, spider mites, insect eggs and small caterpillars. Orius will insert its beak inside the host body, while immobilizing its prey with its front legs, and suck on the insect insides until it is dried up.

Pollinator Observations: Lots of small green bees!

During scouting, we noted that many of our observed flower clusters (up to 20%) had a small green bee visiting (Fig 2). These bees are members of the family Halictidae, and are also known as sweat bees. You can learn more about these little pollinators in this article.

Diseases:

Date	Common Leaf Spot	Phomopsis Leaf Blight	Verticillium Wilt	Anthracnose	Leaf Scorch	Neopest- alotiopsis
6/9/2023	0	0	0	0	0	0
6/15/2023	0	0	0	0	0	0
6/26/2023	0	0	0	0	0	0
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

Phomopsis leaf blight (Phomopsis obscurans): The observed incidence of Phomopsis leaf blight slightly decreased from 8% to 6% of sampled plants this week. During field walk-throughs, the estimated incidence of disease appears to be the same as last week. Infected plants still are in early stages of infection, with 1-2 total lesions per plant. Phomopsis obscurans is a fungal pathogen of strawberry plants that primarily affects the leaves, but can also cause lesions on stems and fruit. This pathogen is often introduced on transplants or nearby susceptible plants and spreads via splashing water. As such, wet conditions often favor pathogen development and spread. We only observed one Common leaf spot (Mycospharella fragariae) lesion (Fig 3) on our sampled plants. With the recent heavy rainfall passing through the research station, we will closely monitor any symptom development and movement of pathogens.

 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.