Reduce fertilizer, pesticide or herbicide use generally
Overall effectiveness category Evidence not assessed
Number of studies: 11
Background information and definitions
In conventional farming or plantation management, a wide range of chemicals are commonly applied for pest control or fertilization, but these can have lethal or sub-lethal effects on other wildlife, including butterflies and moths (Russell & Schultz 2010, Schultz et al. 2016). Therefore, reducing the extent, amount or frequency of chemical application may benefit butterfly and moth populations.
This action includes studies where there has been a general reduction in the use of multiple or unnamed chemicals, either without complete cessation or over a small area. For studies on the reduction or cessation in use of a specific, named chemical, see “Restrict certain pesticides or other agricultural chemicals”. For studies on restricting chemical applications on field edges, see “Leave headlands in fields unsprayed (conservation headlands)”. For studies on the complete cessation of chemical applications across an entire farm, see “Convert to organic farming”. For studies on the reduction of chemical application as part of a general reduction in grassland management intensity, see “Agriculture and aquaculture – Reduce management intensity on permanent grasslands (several interventions at once)”.
Russell C. & Schultz C.B. (2010) Effects of grass-specific herbicides on butterflies: an experimental investigation to advance conservation efforts. Journal of Insect Conservation, 14, 53–63.
Schultz C.B., Zemaitis J.L., Thomas C.C., Bowers M.D. & Crone E.E. (2016) Non-target effects of grass-specific herbicides differ among species, chemicals and host plants in Euphydryas butterflies. Journal of Insect Conservation, 20, 867–877.
Supporting evidence from individual studies
A controlled study in 1984–1988 in three orchards in West Virginia, USA (Brown & Welker 1992) found that orchards managed without pesticides or fertilizer, and with fewer or no herbicides, had more leaf-eating arthropod species, including caterpillars, and greater diversity, than a conventionally managed orchard. Three to five years after establishment, the number of species and diversity of leaf-eating arthropods (e.g. insects and mites) in an unmanaged (23–27 species) and a partially managed (21–33 species) orchard were higher than in a conventionally managed orchard (7–11 species, see paper for diversity data). Over five years, the diversity increased in the reduced management orchards, but in the conventionally managed orchard diversity decreased in the third year and remained low (see paper for details). In spring 1984, three orchards (0.30–0.35 ha) were planted with young trees (1–2 cm diameter). Two reduced management orchards had five apple cultivars at 5 × 4-m spacing. One conventional orchard had one apple cultivar at 5 × 7.5-m spacing. The unmanaged orchard was mown three times/year in 1984–1985, but unmanaged thereafter. The partially managed orchard was pruned commercially, with four annual herbicide applications and monthly mowing. The conventionally managed orchard was pruned and fertilized, mown every 3–4 weeks, and received regular herbicide and pesticide applications, which increased in the third year. From April–September 1984–1988, all leaf-eating arthropods were recorded on 5–10 randomly selected trees/orchard, 4–5 times/year.Study and other actions tested
A replicated, randomized, site comparison study in 1991 at a farmland and grassland site in Cambridgeshire, UK (Sparks & Parish, 1995) found that there was higher butterfly abundance and species richness in areas that had been treated less frequently with herbicide in the previous three years, but abundance and species richness were not affected by the number of pesticide applications in the surveying year itself. Butterfly abundance and species richness increased with a decrease in the number of times that the adjacent fields had been treated with herbicide in the previous three years (data presented as statistical results). Peacock butterfly Inachis io abundance particularly increased with decreased herbicide applications (data presented as statistical results). However, neither overall butterfly abundance nor richness was affected by the number of pesticide applications in the surveying year itself (1991). See paper for details of the effects on individual butterfly species. From May–September 1991, butterflies were surveyed up to once/month in fine weather on twenty-six 200 m transects along margins between fields of any combination of arable farmland and grassland. Each transect was surveyed 2–4 times in both years. The researchers obtained data on the total number of applications of herbicide in 1989–1991 and pesticide in 1991 in the fields adjacent to the surveyed margins.Study and other actions tested
A systematic review of 23 controlled studies (Frampton & Dorne 2007) found that restricting pesticide inputs on crop edges tended to increase moth and butterfly abundance. In six out of 11 studies, moth or butterfly adult or caterpillar abundance was higher where pesticide use was restricted than under normal application (data presented as model results). When both pesticide and herbicide were restricted, both the abundance and species richness of adult moths and butterflies doubled (data presented as model results). In most (9 out of 11) studies, the effect of reducing different pesticides (fungicide, herbicide, insecticide) or the effect of reducing pesticide or fertilizer inputs could not be distinguished from one another. Only controlled studies, comparing areas with higher (or normal) and lower (reduced or no) pesticide input were included. All studies came from Europe.Study and other actions tested
A replicated, randomized, controlled study in 2002–2006 on four lowland farms in Devon and Somerset, UK (Potts et al. 2009) found that unfertilized grassland plots had a similar abundance and species richness of butterflies, and abundance of caterpillars, to fertilized plots. On unfertilized plots, the abundance (1–4 individuals/transect) and species richness (1–2 species/transect) of butterflies, and the abundance of caterpillars (0–4 caterpillars/transect) were not significantly different from fertilized plots (butterfly abundance: 0–2 individuals/transect; richness: 0–1 species/transect; caterpillar abundance: 0–4 caterpillars/transect). In April 2002, six experimental plots (50 × 10 m) were established on permanent pastures (>5-years-old) on four farms. All plots were cut to 5 cm twice/year in May and July, and grazed in September. Three plots/farm were fertilized (225 kg nitrogen/ha, 22 kg phosphorus/ha, 55 kg potassium/ha) and three were not fertilized. From June–September 2003–2006, butterflies were surveyed once/month on a 50-m transect through the centre of each plot. In April, June, July and September 2003–2006, caterpillars were counted (but not identified) on two 10-m transects/plot using a sweep net (20 sweeps/transect).Study and other actions tested
A replicated, paired, site comparison study in 2008 on 36 farms in central Scotland, UK (Fuentes-Montemayor et al. 2011) reported that farms managed with reduced chemical inputs (alongside other agri-environment scheme (AES) options) had a greater abundance and species richness of moths than conventionally-managed farms. Results were not tested for statistical significance. On farms managed with reduced chemical input under AES, 390 individuals of 51 species of micro-moth were recorded, compared to 199 individuals of 43 species on conventionally-managed farms. On AES farms, 1,377 individuals of 71 species of all macro-moths, and 159 individuals of 13 species of declining macro-moths, were recorded, compared to conventional farms where 917 individuals of 61 species of all macro-moths and 111 individuals of 17 species of declining macro-moth were recorded. In 2004, eighteen farms enrolled in AES, and were paired with 18 similar but conventionally managed farms, <8 km away. Each AES farm had at least three of four features (hedgerows, sown grass field margins or banks, sown species-rich grassland, >3-m-wide waterway margins) all with reduced chemical inputs and relaxed cutting and grazing regimes compared to similar habitat features on the conventional farms. From June–September 2008, moths were collected for four hours, on one night/farm, using 6 W heath light traps located next to each habitat type (3–4 traps/farm, ≥100 m apart). Paired farms were surveyed on the same night.Study and other actions tested
A replicated, randomized, paired, controlled study in 2010–2011 in an extensively managed hay meadow in Landau, Germany (Hahn et al 2015) found that plots without insecticide applied had higher caterpillar abundance than plots with insecticide, but the application of herbicide did not alter caterpillar abundance, and plots without fertilizer had lower caterpillar abundance in one of two sampling sessions. In plots not treated with insecticide, caterpillar abundance (1–2 individuals/plot) was higher than in plots with insecticide applied (0 individuals/plot). However, caterpillar abundance was lower in plots not treated with fertilizer (1–2 individuals/plot) than in plots with fertilizer applied in one of two samples (2–3 individuals/plot). Caterpillar abundance was similar in plots without (1–2 individuals/plot) and with (2 individuals/plot) herbicide applied. The results were mostly due to differences in the numbers of two moth groups (Geometridae and Noctuidae). In 2010, sixty-four plots (8 × 8 m) were assigned to one of eight treatments: no pesticide, herbicide or fertilizer, insecticide-, herbicide- or fertilizer-only, or each combination of two or three chemicals applied. Fertilizer was applied twice/year in April, with a granular nitrate/phosphorus/potassium fertilizer and a calcium carbonate/ammonium nitrate fertilizer two weeks apart. Herbicide (Atlantis WG) was applied once/year in April. Insecticide (Karate Zeon) was applied once/year in late May or early June. On 30 May and 27 June 2011, caterpillars were sampled using sweep nets (80 and 100 sweeps/plot).Study and other actions tested
A replicated, site comparison study in 2014 in 26 grasslands in Germany (Mangels et al. 2017) found that unfertilized grasslands had a similar abundance, species richness and diversity of moths to fertilized grasslands. Unfertilized grasslands had a similar abundance, species richness and diversity of moths to fertilized grasslands (data presented as model results). However, unfertilized grasslands did support more specialist moth species than fertilized grasslands (data presented as model results). Of 58 individual species monitored, seven preferred unfertilized or lightly fertilized grasslands, and 12 preferred more heavily fertilized grasslands (see paper for individual species data). From 2006, across three regions, eleven grasslands were fertilized with 1–138 kg nitrogen/ha, and 15 were unfertilized. Moths were collected once/month from nine grasslands in each of two regions (May–August 2014), and from eight grasslands in one region (June–July 2014). Each night, a 12 V actinic and black-light trap were placed in the centre of each of three grasslands for 138–317 minutes/night. Moths were classified as specialists based on the number of food plants eaten by their caterpillars.Study and other actions tested
A replicated, site comparison study in 2013–2014 in 20 vineyards in Catalonia, Spain (Puig-Montserrat et al. 2017) found that vineyards managed with fewer chemicals had more butterfly species than conventional vineyards, but a similar number of moth species. There were more species of butterfly in vineyards managed with fewer chemicals (30–33 species) than conventionally managed vineyards (22–32 species), but the number of moth species was similar (reduced: 193 species; conventional: 190 species). Ten vineyards were managed with fewer insecticide and herbicide (Glyphosate) applications/year than 10 conventionally-managed vineyards. From April–August 2013–2014, butterflies were surveyed four times/year on two 100-m transects/vineyard in nine vineyards/year. One transect was along crop lines, and the other was along grass strips between crop lines. From April–September 2013–2014, moths were sampled for 3–4 hours after sunset using two light traps, one each on a reduced and conventional farm. The number of nights is not specified, but 18 farms were sampled in 2013 and 20 in 2014.Study and other actions tested
A replicated, randomized, paired, controlled study in 2011–2013 in eight forests in Oregon, USA (Root et al. 2017) found that replanted stands with limited or no herbicide applications had a higher species richness, but similar abundance, of moths to stands with more herbicide applied. In forest stands with limited or no herbicide treatment, the species richness of moths (42 species/stand) was higher than in stands with moderate or intensive herbicide treatments (38 species/stand). However, the abundance of moths was not significantly different between stands with different herbicide applications (none: 144–148; limited: 180–195; moderate: 132–138; intensive: 161–172 individuals/stand). In winter 2009–2010, four 10–19-ha stands within each of eight forest blocks were clearcut, and replanted with Douglas fir Pseudotsuga menziesii in spring 2011. Within each block, one stand received each of four herbicide treatments: no herbicide; limited herbicide treatment for herbaceous plants in year two and woody vegetation in year three; moderate treatment prior to planting and for woody vegetation control in years three and four; intensive treatment with the moderate applications plus herbaceous control in years two and three. The moderate treatment reflected standard management practice. From May–August 2012–2013, moths were sampled overnight once/month using three 22 W universal black-light traps/stand. Stands within a block were sampled on the same night.Study and other actions tested
A site comparison study in 2016 in five coffee plantations in Veracruz, Mexico (Sosa-Aranda et al. 2018) found that coffee plantations managed less intensively, including with fewer chemical inputs, supported more caterpillars than more intensively managed plantations. On the least intensively managed plantation, both the abundance (212 individuals) and species richness (129 species) of caterpillars was higher than on the most intensively managed plantation (abundance: 47 individuals; richness: 46 species). Both abundance and species richness on the other three plantations were intermediate. In addition, the amount of damage found on coffee leaves was not related to either caterpillar abundance or species richness (data not presented). The management intensity of five coffee plantations was measured based on 10 vegetation characteristics (including canopy cover, epiphyte cover, area of shade trees and presence of herbs) and the frequency of six external inputs (fertilizers, insecticides, herbicides, fungicides, irrigation and ploughing). In July, September and December 2016, all caterpillars were collected by hand from all plants along three 30 × 2-m transects in the centre of each plantation, and reared to adults for species identification.Study and other actions tested
A replicated, site comparison study in 2010–2014 in 50 agricultural areas in the Swiss Plateau, Switzerland (Zingg et al. 2018) found that landscapes with more semi-natural habitat managed without pesticide and fertilizer had more butterflies than landscapes with less semi-natural habitat managed without chemicals. Agricultural areas with more than 20% of the land managed as semi-natural habitat without chemicals had a higher abundance and species richness of all butterflies than areas with less than 10% semi-natural habitat with no chemicals. The abundance of farmland butterflies, and the species richness of threatened butterflies, was higher in landscapes with more chemical-free semi-natural habitat than in landscapes with less chemical-free semi-natural habitat (all data presented as model results). Fifty mixed farming areas (1 km2) were selected where 2.5–32.2% of agricultural land was managed under agri-environment schemes (primarily extensive meadows cut or grazed once/year with no fertilizers or pesticides). Butterflies were surveyed seven times along a 2.5-km transect through each 1-km2 area in one of five years (2010–2014). Species were classified as “farmland species” if they occur in open habitat, and “threatened” species if they were listed as Near Threatened, Vulnerable or Critically Endangered on the Swiss RedList.Study and other actions tested