Susquehanna University Scholarly Commons Senior Scholars Day Apr 28th, 12:00 AM - 12:00 AM Effects of Chronic Exposure to the Herbicide, Mesotrione, on Spiders Maya Khanna Susquehanna University Joseph Evans Susquehanna University Matthew Persons Susquehanna University Follow this and additional works at: https://scholarlycommons.susqu.edu/ssd Khanna, Maya; Evans, Joseph; and Persons, Matthew, "Effects of Chronic Exposure to the Herbicide, Mesotrione, on Spiders" (2020). Senior Scholars Day. 34. https://scholarlycommons.susqu.edu/ssd/2020/posters/34 This Event is brought to you for free and open access by Scholarly Commons. It has been accepted for inclusion in Senior Scholars Day by an authorized administrator of Scholarly Commons. For more information, please contact [email protected]. Effects of Chronic Exposure to the Herbicide, Mesotrione on Spiders Maya Khanna, Joseph Evans, and Matthew Persons Department of Biology, Susquehanna University, PA 17870 Tigrosa helluo Trochosa ruricola Mecaphesa asperata Frontinella pyramitela Tetragnatha laboriosa Hogna lenta Pisaurina mira Abstract Methods All spiders were collected on Table 1. The predicted lethality of mesotrione on each spider species based upon soil association levels and species size. Toxicity is predicted to increase with smaller size and Mesotrione is a widely used agricultural herbicide and is frequently used alone or as an adjuvant for the Susquehanna University’s campus. Each spider was housed in a 473 ml (16oz) greater soil contact. Sample sizes for each species are indicated to the left. A total of 615 herbicides glyphosate and atrazine. The effects of mesotrione are largely untested on beneficial non-target spiders were used in this study. species such as spiders. Different spider species may be differentially susceptible due to size differences, container with two plastic coffee stirrers microhabitat, and levels of exposure to this herbicide via soil contact. We tested mortality differences of serving as stem-like support structures. Genus Common Name Microhabitat Size Predicted lethality seven species of spider when exposed to field-relevant concentrations of mesotrione-treated soil over a 55- All collected spiders were randomly and day period. We tested the web-building spiders Frontinella pyramitela and Tetragnatha laboriosa. We also evenly split by sex across herbicide and Frontinella Bowl and doily Suspension Very small Low n= 130 pyramitela spider web-builder tested the stem and leaf-dwelling ambush spiders Mecaphesa asperata and Pisaurina mira and three species control treatments. Each container was Tetragnatha Long-jawed orb of ground-dwelling wolf spiders that vary in their burrowing propensities: Hogna lenta (infrequent sprayed with either water (control) or n= 74 Web-builder Small Moderate/ laboriosa weaver & vegetation Low burrower), Tigrosa helluo (facultative burrower) and a habitually burrowing wolf spider Trochosa ruricola. All recommended field dosage of tenacity Crab spider (mesotrione) prior to introducing a n= 38 Mecaphesa Vegetation Small Moderate seven of these species commonly occur in mesotrione-treated agricultural systems. We found that the web- asperata building spider Frontinella but not Tetragnatha showed increased mortality compared to control treatments. single test subject. Each spider was then observed daily for mortality over a 55 Pisaurina Nurseryweb Vegetation & Moderate Moderate Mecaphesa, Pisaurina, Trochosa, and Tigrosa all showed large significant increases in mortality under chronic n= 70 spider day period. Spiders were fed ad libitum mira soil surface exposure to mesotrione-treated soil whereas the wolf spider Hogna lenta was unaffected. We also found Hogna lenta Wolf spider Soil surface Large High sex-specific mortality effects in Pisaurina with males having higher mortality. Several species showed once weekly appropriately sized n= 71 crickets. Spider position in the container significant shifts in space use when exposed to mesotrione and we found significant interaction between Tigrosa Wolf spider n= 156 Soil surface Large High spider weight gain and herbicide treatment. In general, mesotrione is an unsafe herbicide for some species was noted daily and spiders were helluo and burrow weighed every 12 days and/or until the of spiders. Alternative herbicides to mesotrione should be considered to minimize the negative biocontrol n= 76 Trochosa Wolf spider Soil surface Moderate Very High impact on beneficial spiders within integrated pest management systems. day they died. ruricola and burrow Introduction Herbicide use has drastically increased in the United States since the 1960s. In recent years corn has been the most dosed crop, with 98% of agriculture crop dosed with herbicides. Results Summary (2014. Fernandez-Cornejo, et al.) Mesotrione is a widely used herbicide in crop systems and 60 residential lawns. It is a relatively new herbicide, officially registered in 2001 * * * • Chronic exposure to field-relevant concentrations of 9Mesotrione.2001). The lethal and sublethal effects of mesotrione on non-target species 50 mesotrione adversely affects spiders but not all * * have been poorly tested and largely restricted to bacteria, earthworms, and aquatic animals 40 species were equally impacted. (Zhang et al. 2019; Carles et al. 2017; EFSA, 2016). Although spiders are significant biocontrol Control 30 Mesotrione agents in agricultural systems, possible negative effects of mesotrione residue on • Mesotrione shortened the lifespan of Frontinella, Mecaphesa, chronically-exposed spiders has not been measured. 20 Pisaurina, Tigrosa, and Trochosa but not Tetragnatha or Hogna. 10 Mortality was different for spiders of similar size that occupy similar Days alive after exposure after alive Days microhabitats (i.e. Tigrosa and Hogna for ground-dwellers and We tested seven different spider species commonly found in agricultural systems. These 0 Mecaphesa Pisaurina Hogna Tigrosa Trochosa Frontinella and Tetragnatha for web-builders). This suggests that species comprise five families and prefer different microhabitats within crop systems. One Frontinella Tetragnatha W W/V V V/G G G G spider contact with soil alone or feeding modality is not a good species, the small bowl-and-doily spider, Frontinella pyramitela, spends nearly all of its time Figure 1. Mean number of days alive (±SE) since mesotrione herbicide application of soil for seven species of spider that vary in their predictor of toxicity. suspended in a horizontal web with almost no vegetation or soil contact. Another species is microhabitat use. W= web-builders, V= vegetation-dwelling, and G=ground dwelling. Asterisks = significant differences between • We found no significant sex difference in mesotrione-induced the long-jawed orb-weaver, Tetragnatha laboriosa, which feeds from a horizontal web but herbicide and control pairs. Two-way ANOVA, Species effect: F6,601=30.05, p<0.0001; Mesotrione effect: F1,601=93.86, p<0.0001; mortality among wolf spiders however we did find that male nursery- Species*Mesotrione: F6,601=7.26, p<0.0001. Spiders observed on the side of the container web spiders, Pisaurina, had significantly higher mortality than females also spends time walking on vegetation. Two other species include the crab spider, Spider Weight Gain over 12 Days * 120 10 and Pisaurina spent significantly more time on the sides of the Mecaphesa asperata, and nursery-web spider, Pisaurina mira. These species do not build Control * Control 9 container in the mesotrione treatment. We also found significant shifts 100 Mesotrione webs and spend most of their time hunting on vertical surfaces of the vegetation. The Mesotrione 8 in spatial position for other spider species except those that were 7 remaining spiders include three ground-dwelling wolf spiders, Trochosa ruricola, Tigrosa 80 ground-dwelling, suggesting that non-wolf spiders may be able to * 6 helluo, and Hogna lenta. These species live on the ground surface although Tigrosa helluo 60 5 behaviorally mitigate the effects of mesotrione through avoidance. and Hogna lenta spend some time in low vegetation while Trochosa ruricola spends most of 4 There were significant weight gain differences by species and 40 * 3 their time within excavated burrows during the day. Tigrosa helluo, the largest of the three 12 (mg) 1 to day herbicide treatment with Hogna and Trochosa gaining significantly Observations on side Observations 2 Mean weight gain from from gain weight Mean 20 more weight in the mesotrione treatment while the opposite was true species, also shows the greatest sexual size dimorphism with females being four to ten times 1 Tigrosa. 0 0 for heavier than males. Hogna Pisaurina Tigrosa Trochosa lenta mira helluo ruricola Hogna Tigrosa Conclusions Trochosa Figure 2. Mean weight gain between start of experiment and day 12 (±SE). Pisaurina Frontinella Mecaphesa We examined how species differences in spatial preferences, size, and feeding ecology may Asterisks = significant differences in weight between control and mesotrione Tetragnatha The herbicide, mesotrione, has large and significant lethal effects treatments within that species. Two-way ANOVA, Species effect: F =13.8, Figure 3. Mean number of observations on side of container over a contribute to differences in toxicological sensitivity to the herbicide mesotrione. To prevent 3,352 twenty day period (±SE). Asterisks = significant differences between on a variety of agriculturally-important spider species, but spider p<0.0001; Herbicide effect: F1,352=0.535,