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Does a native fungus control spider mites on strawberries?
University of Cauca researchers in Colombia tested seven native fungal isolates against the two-spotted spider mite on strawberry. The strongest, HF234 (identified as Metarhizium anisopliae), gave 84.3 ± 8.9% corrected mortality in the lab and significantly reduced eggs, larvae, nymphs and adults on greenhouse plants compared with an untreated control.
A strawberry plant can look perfectly healthy and still be carrying spider mites. A team from the University of Cauca found the mite on all eight farms it surveyed in Cauca, Colombia, including on apparently healthy plants, and tested native fungi against it (Mosquera Noriega et al., 2026). The work so far is lab and greenhouse only, and the authors are clear it still needs testing in the field.
The two-spotted spider mite, Tetranychus urticae, is a major constraint in strawberry production, and the authors note that managing it still relies heavily on acaricides. Intensive, repeated use of those chemicals has selected for resistant mite populations.
What did the team do?
The researchers, from the Agroindustrial Biotechnology Center (CBA) in the Faculty of Agricultural Sciences at the University of Cauca, worked in three stages.
- A farm survey. Between February and September 2024 they sampled eight strawberry farms in the municipalities of Silvia and Sotará, in Cauca, at 2,465 to 3,132 metres above sea level. On each farm they took 250 trifoliate leaves from 50 plants showing mite symptoms and 250 from 50 apparently healthy plants, then checked every leaf under a stereomicroscope.
- Lab bioassays. Seven fungal isolates, originally collected from soil and roots in local strawberry crops, were sprayed with an airbrush onto strawberry leaves carrying ten adult female mites each. Four isolates were Paecilomyces and three were Metarhizium. Mortality was checked 240 hours later and corrected for natural deaths in the untreated control using Abbott’s formula (that is what “corrected mortality” means here). The best isolate then went head to head with a commercial abamectin acaricide.
- A greenhouse trial. Strawberry plants (cultivar Frontera) at the Faculty of Agricultural Sciences were each given 20 adult female mites, left five days for the mites to establish, then sprayed with HF234, abamectin or a control solution. Thirteen days after spraying, the team counted eggs, larvae, nymphs and adults on nine leaflets per plant.
Entomopathogenic fungi such as Metarhizium and Paecilomyces can infect plant-feeding mites, the authors explain, by sticking to the mite’s cuticle, germinating, penetrating it and colonising the mite internally.
What did they find?
- Healthy-looking plants weren’t mite-free. The mite was found on every farm. On symptomatic plants, 40% to 100% of trifoliate leaves were infested. On apparently healthy plants the figure was generally lower but still ranged from 10% to 100%. One farm (Cacique Alto, in Silvia) hit 100% in both groups. The authors point out the farms were chosen because they had a history of the pest, so finding it was expected; what they call particularly noteworthy is that it was also on plants with no visible damage.
- Isolates varied a lot. Corrected mortality ranged from 10.1 ± 1.0% (HF437) to 84.3 ± 8.9% (HF234). HF234, HF188 (74.2 ± 3.5%) and HF232 (73.7 ± 5.8%) all topped 70%, and HF234 did not differ significantly from the other two. It was taken forward because it had the highest average.
- Against abamectin in the lab. In the direct comparison, HF234 produced significantly higher corrected mortality than abamectin: 84.31 ± 2.06% versus 68.14 ± 2.98%.
- In the greenhouse. HF234 significantly reduced eggs, larvae, nymphs and adults compared with the untreated control. It also left significantly fewer eggs, larvae and nymphs than abamectin. Adult numbers did not differ significantly between HF234 and abamectin.
- Confirmed identity. DNA sequencing of the ITS region identified HF234 as Metarhizium anisopliae, with 99.81% identity to reference sequences.
The greenhouse counts, as mean individuals per plant (± standard deviation):
- Eggs: control 336.00 ± 4.47, abamectin 192.60 ± 4.62, HF234 78.40 ± 4.16.
- Larvae: control 117.60 ± 4.93, abamectin 23.00 ± 1.48, HF234 4.60 ± 0.55.
- Nymphs: control 128.75 ± 2.59, abamectin 69.08 ± 0.90, HF234 11.50 ± 0.87.
- Adults: control 73.00 ± 2.55, abamectin 26.20 ± 1.64, HF234 24.80 ± 1.48.
The authors make the point that knocking back eggs, larvae and nymphs matters in a pest with overlapping generations, because that is where the next wave of mites comes from.
What could it mean for growers?
The authors conclude that their results support early monitoring for the mite, and that HF234 is a candidate for further evaluation as a biological control agent against T. urticae in strawberry production. They describe its efficacy as comparable to, and for some response variables greater than, that of abamectin, and they see its different mode of action as adding to its potential value in integrated pest management (IPM) programs aimed at reducing chemical dependence. They also say further studies under field conditions are required before it could be integrated into IPM programs.
For strawberry growers, the authors say their results support checking trifoliate leaves from apparently healthy plants, inspecting the abaxial leaf surface, and surveillance before chlorosis or stippling becomes clearly visible. The fungus itself is not at that stage yet: the authors say field studies are required before it could be integrated into IPM programs.
What were the limitations?
- The study was limited to laboratory and greenhouse conditions, and how HF234 performs under commercial field conditions is unknown.
- The authors say field efficacy and persistence, formulation stability, application rate and frequency, compatibility with other IPM components, and potential effects on non-target organisms all still need to be worked out.
- In the lab screen, HF234 did not differ statistically from HF188 and HF232; it was chosen for its higher average.
- The farms were selected because they had previous infestations of the mite.
- The authors caution that comparing their mortality figures with other studies should allow for differences in fungal isolate, mite species, conidial concentration, exposure method and evaluation time.
Trial details
- Where: Colombia. Farm survey on eight strawberry farms in the municipalities of Silvia and Sotará, Cauca Department, at 2,465 to 3,132 metres above sea level (m a.s.l.). Lab work at the Agroindustrial Biotechnology Center (CBA), University of Cauca. Greenhouse trial at the Faculty of Agricultural Sciences, University of Cauca (Las Guacas village, Popayán, Cauca), at approximately 1,735 m a.s.l. with an average temperature of 19 °C.
- Crop: strawberry (Fragaria × ananassa). Surveyed farms grew established crops of cultivars Sabrina, Ventana and Frontera. Greenhouse plants were cv. Frontera, obtained from mother plants and selected for a comparable vegetative stage. Lab bioassays used leaves from healthy greenhouse-grown plants.
- Pest: two-spotted spider mite, Tetranychus urticae, two-day-old adult females in the bioassays and greenhouse infestation. Mites were kept in a colony on strawberry leaves at 23 ± 3 °C, 55 ± 5% relative humidity and a 12:12 hour light:dark photoperiod.
- Fungi: seven native isolates from soil and root samples from strawberry crops in Sotará and Silvia: HF177, HF197, HF232 and HF437 (Paecilomyces spp.) and HF152, HF188 and HF234 (Metarhizium). Grown on YGC medium at 28 °C in darkness for 10 days; suspensions in 0.02% (v/v) Tween 80, adjusted to 1 × 108 conidia per millilitre (1 × 108 conidia mL-1). HF234 was identified as M. anisopliae by ITS sequencing (99.81% identity; GenBank accession PZ694451).
- How long: farm sampling February to September 2024. Lab mortality assessed 240 hours after application. Greenhouse counts 18 days after initial infestation (13 days after treatment).
- Lab conditions: leaves on moistened cotton in closed plastic containers with perforated lids; 17 to 22 °C, relative humidity above 60%, 12:12 hour light:dark photoperiod.
- Treatments: screening of seven isolates plus a negative control (0.02% Tween 80), 300 microlitres per experimental unit by airbrush. Comparison of HF234 with Abafed (AGROZ S.A., Ibagué, Colombia; abamectin 18 grams per litre) at the manufacturer’s recommended rate of 10 microlitres per 10 millilitres of water, plus the negative control. Greenhouse: HF234, abamectin and negative control, 4 millilitres per plant onto the central trifoliate leaves, with emphasis on the abaxial surface.
- Design: completely randomised designs. Screening: five replicates per treatment, ten adult females per unit. Comparison: seven replicates per treatment, ten adult females per unit. Greenhouse: five plants per treatment (each plant one unit), 20 adult females released per plant onto three central trifoliate leaves, nine leaflets counted per plant. Farm survey: 500 trifoliate leaves from 100 plants per farm.
- Statistics: one-way ANOVA with Tukey’s HSD at α = 0.05; residuals checked with Anderson-Darling and Levene’s tests. Screening: F6,28 = 623.98, p < 0.001. HF234 versus abamectin: F1,12 = 139.35, p < 0.001. Greenhouse: eggs F2,12 = 4264.68, larvae F2,12 = 2054.69, nymphs F2,12 = 6251.93, adults F2,12 = 990.23, all p < 0.001.
- Results: survey infestation 40% to 100% (symptomatic plants) and 10% to 100% (apparently healthy plants). Corrected mortality (% ± SD): HF234 84.3 ± 8.9, HF188 74.2 ± 3.5, HF232 73.7 ± 5.8, HF197 61.2 ± 6.4, HF152 21.7 ± 0.6, HF177 20.8 ± 0.5, HF437 10.1 ± 1.0. HF234 84.31 ± 2.06% versus abamectin 68.14 ± 2.98%. Greenhouse counts per plant as listed above.
- Funding: Colombian General Royalties System (Sistema General de Regalías, SGR), through the project “Research and Development for Strengthening the Strawberry Production Chain in the Department of Cauca” (BPIN 2018000100185), implemented by the University of Cauca with the support of the Government of Cauca.
- Conflicts of interest: the authors declare none.
- Publication: Frontiers in Agronomy, volume 8, article 1940106, published 26 October 2026 (peer reviewed), https://doi.org/10.3389/fagro.2026.1940106. Licence: CC BY 4.0.
- Not reported in the paper: substrate and growing system; greenhouse lighting (source, PPFD, DLI, photoperiod, spectrum) and lab light source and intensity; greenhouse day and night temperatures, relative humidity and CO2; CO2 in the lab; nutrition (solution, EC, pH); dates of the lab and greenhouse trials; and plant age or growth stage beyond “comparable vegetative stage”.
Links
- The study: Native entomopathogenic fungi as potential biocontrol agents against Tetranychus urticae in strawberry cultivation
- The institution: Faculty of Agricultural Sciences (Facultad de Ciencias Agrarias), University of Cauca
References
- Mosquera Noriega, N. R., Sanchez-Trujillo, S., Hoyos Concha, J. L., & Paz Narvaez, I. E. (2026). Native entomopathogenic fungi as potential biocontrol agents against Tetranychus urticae in strawberry cultivation. Frontiers in Agronomy, 8, 1940106. https://doi.org/10.3389/fagro.2026.1940106