Impact of insecticides on the performance natural biocontrol
The two years following the invasion of FAW in Togo showed higher numbers of egg masses collected per farm than the next several years. Although there were high numbers of egg masses those first two years, none were found to be parasitized. However, the low numbers of egg masses collected since 2018 showed parasitism rates increasing from 14.72% in 2018 to 45.38% in 2022 (Table 1). The same trend was shown with larvae as higher numbers were collected per farm in 2016 and 2017 than the following years. Correlation analysis between collected egg masses and larvae showed no relationship (r = 0.0002, P = 0.869). Larval parasitism rates were very low in 2016 (1.32%) and 2017 (2.53%), but increased to 15.96% in 2018 and 42.23% in 2022 (Table 1).
Table 1
Numbers and parasitism rates of egg masses and larvae across years of collections
Year | Farm | Egg mass | Larvae |
n | P | Per farm | Pr (%) | n | P | Per farm | Pr (%) |
2016 | 61 | 103 | 0 | 1.67 ± 0.23b | 0a | 1025 | 15 | 17.02 ± 1.36b | 1.32 ± 0.36a |
2017 | 37 | 42 | 0 | 1.14 ± 0.41b | 0a | 692 | 17 | 18.53 ± 3.05b | 2.53 ± 0.34a |
2018 | 27 | 13 | 2 | 0.46 ± 0.32a | 14.72 ± 2.03b | 139 | 23 | 4.82 ± 1.23a | 15.96 ± 1.35b |
2019 | 79 | 35 | 9 | 0.44 ± 0.11a | 23.63 ± 1.35b | 425 | 123 | 5.07 ± 0.31a | 28.72 ± 1.82bc |
2020 | 71 | 29 | 11 | 0.42 ± 0.21a | 36.28 ± 2.41bc | 296 | 93 | 4.11 ± 1.51a | 31.37 ± 2.35bc |
2021 | 28 | 9 | 4 | 0.31 ± 0.18a | 42.76 ± 3.85c | 108 | 46 | 3.76 ± 1.65a | 41.85 ± 3.61c |
2022 | 45 | 11 | 5 | 0.22 ± 0.14a | 45.38 ± 1.69c | 153 | 65 | 3.36 ± 0.86a | 42.23 ± 2.54c |
df | | | | 6, 347 | 6, 91 | | | 6, 347 | 6, 269 |
F | | | | 4.65 | 12.26 | | | 8.69 | 6.82 |
P | | | | 0.032 | < 0.001 | | | 0.009 | 0.018 |
n = total number, P = number of parasitized individuals, Pr = parasitism rate. |
Means (± SE) followed by the same letter in the column are not statistically different |
During the survey, farmers were interviewed regarding the insecticide applications and depending on the year, between 52.1–74.1% responded. The percentage of sprayed farms were very high in 2017 (91.38% of farms inspected) and 2016 (73.25%), compared with the range of 23.52–11.08% obtained between 2018 and 2022. Higher egg and larval parasitism rates were recorded in unsprayed farms than sprayed farms every year of the seven-year study (Fig. 2).
Entomopathogenic organisms associated with FAW
Entomopathogenic agents associated with FAW larvae included a nematode, Ovomermis sinensis (Nematoda: Mermithidae), unidentified species in the bacteria family of Enterobacteriaceae and Enterococcus species, unidentified viruses belonging to Ascoviruses and Baculoviruses, and fungal species Isaria spp. (Hypocreales: Clavicipitaceae) and Metarhizium rileyi (Hypocreales: Cordycipitaceae). The nematode, O. sinensis had low infection rates, relative abundance and indice of dispersion until 2018, compared to the following years (Table 2). The infection rate of bacteria species belonging to Enterobacteriaceae were not constant during the period of collections, but its relative abundances were high in 2016 and 2017. The indexes of dispersion were constant over the study period. Infection rates of Enterococcus species increased from 2018 onward, while its relative abundance decreased, and its indexes of dispersion remained constant along the study (Table 2). Larvae infected by Ascovirus were collected from 2018 and Baculovirus was collected in 2017. However, the two virus and fungal groups had constant infection rates, relative abundance, and indice of dispersion throughout the study (Table 2).. Although the spatial distribution of entomopathogens yearly increased (Fig. 3), the population densities of each species are similar.
Table 2
Entomopathogenic associated with FAW from 2016 to 2022 in Togo and their infection rates, relative abundances, and index of dispersions
Species | | 2016 | 2017 | 2018 | 2019 | 2020 | 2021 | 2022 | df | F | P |
Entomopathogenic nematode |
O. sinensis | Ir (%) | 0.29 ± 1.02a | 0.29 ± 1.01a | 2.16 ± 1.05a | 12.94 ± 2.31b | 16.55 ± 2.51b | 17.59 ± 2.63bc | 20.92 ± 1.03c | 6, 347 | 7.32 | 0.011 |
pd | 0.03 ± 0.01a | 0.01 ± 0.05a | 0.02 ± 0.03a | 0.02 ± 0.01a | 0.01 ± 0.06a | 0.01 ± 0.03a | 0.01 ± 0.4a | 6, 347 | 0.23 | 0.362 |
RA (%) | 20 ± 3.56b | 11.76 ± 2.23a | 13.04 ± 2.32a | 44.72 ± 3.05c | 52.69 ± 2.12d | 41.30 ± 3.03c | 49.23 ± 2.02d | 6, 347 | 11.82 | < 0.001 |
iD | 0.02 ± 0.02a | 0.06 ± 0.03a | 0.07 ± 0.03a | 0.39 ± 0.02b | 0.51 ± 0.06c | 0.54 ± 0.04c | 0.56 ± 0.05c | 6, 347 | 13.59 | < 0.001 |
Entomopathogenic bacteria |
Enterobacteriaceae | Ir (%) | 0.20 ± 0.12a | 0.29 ± 0.14a | 0.72 ± 0.23b | 0.71 ± 0.22b | 0.34 ± 0.15a | 0.93 ± 0.2bc | 0.65 ± 0.2b | 6, 347 | 6.23 | 0.014 |
pd | 0.02 ± 0.03a | 0.02 ± 0.03a | 0.01 ± 0.02a | 0.02 ± 0.04a | 0.01 ± 0.02a | 0.01 ± 0.03a | 0.01 ± 0.3a | 6, 347 | 0.15 | 0.315 |
RA (%) | 13.33 ± 0.65b | 11.76 ± 0.32b | 4.3s5 ± 0.18a | 2.44 ± 0.09a | 1.08 ± 0.33a | 2.17 ± 0.11a | 1.54 ± 0.06a | 6, 347 | 4.23 | 0.024 |
iD | 0.02 ± 0.1a | 0.03 ± 0.06a | 0.04 ± 0.02a | 0.03 ± 0.05a | 0.01 ± 0.03a | 0.04 ± 0.04a | 0.02 ± 0.03a | 6, 347 | 1.23 | 0.117 |
Enterococcus | Ir (%) | 0.29 ± 0.23a | 0.29 ± 0.05a | 0.72 ± 0.04b | 0.94 ± 0.35bc | 1.01 ± 0.51c | 0.93 ± 0.12bc | 1.31 ± 0.34c | 6, 347 | 12.03 | < 0.001 |
pd | 0.02 ± 0.02a | 0.02 ± 0.03a | 0.01 ± 0.04a | 0.02 ± 0.02a | 0.03 ± 0.02a | 0.01 ± 0.02a | 0.02 ± 0.03 | 6, 347 | 0.423 | 0.412 |
RA (%) | 20 ± 3.21bc | 11.76 ± 1.23b | 4.35 ± 0.57a | 3.23 ± 0.33a | 3.23 ± 0.13a | 2.17 ± 0.31a | 3.08 ± 0.21a | 6, 347 | 5.58 | 0.035 |
iD | 0.03 ± 0.2a | 0.03 ± 0.12a | 0.04 ± 0.13a | 0.03 ± 0.02a | 0.01 ± 0.01a | 0.04 ± 0.12a | 0.02 ± 0.10 | 6, 347 | 0.98 | 0.095 |
Entomopathogenic virus |
Ascoviruses | Ir (%) | * | * | 0.72 ± 0.021a | 2.35 ± 0.71a | 2.03 ± 0.58a | 1.85 ± 0.085a | 1.96 ± 0.75a | 4, 249 | 1.63 | 0.069 |
pd | * | * | 0.01 ± 0.02a | 0.03 ± 0.04a | 0.05 ± 0.02a | 0.03 ± 0.2a | 0.3 ± 0.03a | 4, 249 | 0.37 | 0.428 |
RA (%) | * | * | 4.35 ± 1.02a | 8.13 ± 1.15a | 6.45 ± 1.19a | 4.35 ± 1.35a | 4.62 ± 0.86a | 4, 249 | 0.85 | 0.112 |
iD | * | * | 0.04 ± 0.1a | 0.04 ± 0.09a | 0.04 ± 0.12a | 0.04 ± 0.11a | 0.02 ± 0.05a | 4, 249 | 0.68 | 0.231 |
Baculoviruses | Ir (%) | * | 0.14 ± 0.23a | 0.72 ± 0.12a | 3.06 ± 0.56a | 3.04 ± 0.81a | 2.78 ± 0.69a | 3.27 ± 1.05a | 5, 286 | 1.09 | 0.183 |
pd | * | 0.01 ± 0.02a | 0.01 ± 0.02a | 0.03 ± 0.05a | 0.02 ± 0.01a | 0.02 ± 0.02a | 0.03 ± 0.01a | 5, 286 | 1.07 | 0.065 |
RA (%) | * | 5.88 ± 1.02a | 4.35 ± 1.15a | 10.57 ± 2.03a | 9.68 ± 1.85a | 6.52 ± 1.35a | 7.69 ± 2.31a | 5, 286 | 0.85 | 0.076 |
iD | * | 0.03 ± 0.02a | 0.04 ± 0.10a | 0.05 ± 0.12a | 0.03 ± 0.21a | 0.04 ± 0.12a | 0.04 ± 0.09a | 5, 286 | 1.21 | 0.097 |
Entomopathogenic fungi |
Isaria spp. | Ir (%) | * | * | 0.72 ± 0.25a | 0.47 ± 0.12a | 0.34 ± 0.32a | 0.93 ± 0.25a | 0.65 ± 0.16a | 4, 249 | 1.02 | 0.135 |
pd | * | * | 0.01 ± 0.03a | 0.02 ± 0.01a | 0.01 ± 0.03a | 0.01 ± 0.02a | 0.01 ± 0.05a | 4, 249 | 0.36 | 0.512 |
RA (%) | * | * | 4.35 ± 0.38a | 1.63 ± 0.25a | 1.08 ± 0.68a | 2.17 ± 0.62a | 1.54 ± 0.23a | 4, 249 | 1.36 | 0.125 |
iD | * | * | 0.04 ± 0.11a | 0.01 ± 0.09a | 0.01 ± 0.02a | 0.04 ± 0.05a | 0.02 ± 0.06a | 4, 249 | 0.96 | 0.139 |
M. rileyi | Ir (%) | * | 0.14 ± 0.05a | 0.72 ± 0.08a | * | 0.68 ± 0.12a | 0.93 ± 0.31a | 0.65 ± 0.08a | 4, 207 | 1.32 | 0.067 |
pd | * | 0.01 ± 0.02a | 0.01 ± 0.01a | * | 0.02 ± 0.03a | 0.01 ± 0.02a | 0.01 ± 0.02a | 4, 207 | 0.34 | 0.623 |
RA (%) | * | 5.88 ± 1.02a | 4.35 ± 1.06a | * | 2.15 ± 0.81a | 2.17 ± 0.09a | 1.540.12a | 4, 207 | 1.23 | 0.098 |
iD | * | 0.03 ± 0.21a | 0.04 ± 0.05a | * | 0.01 ± 0.06a | 0.04 ± 0.05a | 0.02 ± 0.05a | 4, 207 | 0.52 | 0.238 |
*no collection, iD-index of dispersion, Ir-infection rate, pd-population density, RA-relative abundance; means (± SE) in the same row with same letter are not statistically different |
Complex Of Parasitoids
During this study, 11 species of parasitoids were collected and identified. The egg parasitoid Telenomus remus (Hymenoptera: Platygastridae) was consistently collected from 2018 with increasing parasitism rates from 15.38–45.44% in 2022 and equally dispersed during the collection period (Table 3). One species of egg-larva parasitoid, Chelonus bifoveolatus (Hymenoptera: Braconidae), was also collected with low parasitism rates that increased from 0.39% in 2016 to 3.70% in 2021. This species had an increasing index of dispersion and decreasing relative abundance during the study (Table 3). The larval parasitoids included three dipteran species, Anatrichus erinaceus (Chloropidae), Archytas spp. and Lespesia spp. (Tachinidae), six hymenopteran species including Bracon sp., Coccygidium luteum, Cotesia icipe and Meteoridea testacea (Braconidae), and Campoletis grioti and Ophion spp. (Ichneumonidae). The parasitism rate of A. erinaceus was low but increased slightly in 2020; the index of dispersion was consistent throughout the study and the relative abundance increased in 2016 and 2017. The indexs of dispersion of Archytas spp. and Lespesia spp. were the same across all years of collection, with small variations found among the parasitism rates and relative abundances (Table 3). Parasitism rates of all the other larval parasitoids increased moderately from 2018 onward, with low variation in relative abundance and index of dispersion (Table 3). Although the spatial distribution of parasitoids yearly increased (Fig. 4), the population densities of each species are similar.
Table 3
Egg, egg-larval and larval parasitoids with annually parasitism rates, population densities, relative abundance and index of dispersion
Species | | 2016 | 2017 | 2018 | 2019 | 2020 | 2021 | 2022 | df | F | P |
Egg Parasitoid |
T. remus | Pr (%) | * | * | 15.38 ± 2.31a | 25.71 ± 3.25b | 37.93 ± 3.65bc | 44.44 ± 4.23c | 45.46 ± 3.95c | 4, 249 | 6.85 | 0.025 |
pd | * | * | 0.01 ± 0.02a | 0.02 ± 0.01a | 0.02 ± 0.03a | 0.01 ± 0.03a | 0.01 ± 0.02a | 4, 249 | 0.35 | 0.324 |
RA (%) | * | * | 100 | 100 | 100 | 100 | 100 | 4, 249 | * | * |
iD | * | * | 0.07 ± 0.12ab | 0.05 ± 0.08a | 0.07 ± 0.10ab | 0.11 ± 0.14b | 0.09 ± 0.11b | 4, 249 | 4.38 | 0.046 |
Egg-larval Parasitoids |
C. bifoveolatus | Pr (%) | 0.39 ± 0.06a | 0.29 ± 0.12a | 2.16 ± 0.21b | 2.12 ± 0.18b | 2.03 ± 0.18b | 3.70 ± 0.28b | 2.61 ± 0.22b | 6, 347 | 6.31 | 0.033 |
pd | 0.01 ± 0.03a | 0.02 ± 0.04a | 0.02 ± 0.02a | 0.02 ± 0.03a | 0.01 ± 0.01a | 0.01 ± 0.03a | 0.01 ± 0.02a | 6, 347 | 0.32 | 0.624 |
RA (%) | 26.67 ± 1.35b | 11.76 ± 1.12ab | 13.04 ± 1.23ab | 7.32 ± 1.06a | 6.45 ± 0.95a | 8.70 ± 1.25a | 6.15 ± 0.79a | 6, 347 | 4.35 | 0.042 |
iD | 0.05 ± 0.02a | 0.03 ± 0.11a | 0.07 ± 0.12ab | 0.08 ± 0.06ab | 0.07 ± 0.06ab | 0.11 ± 0.21b | 0.09 ± 0.18b | 6, 347 | 3.58 | 0.048 |
Larval Parasitoids |
A. erinaceus | Pr (%) | * | 0.14 ± 0.17a | 0.72 ± 0.35ab | 0.71 ± 0.23ab | 0.34 ± 0.12a | 0,93 ± 0.21bc | 1.31 ± 0.58c | 5, 286 | 5.64 | 0.017 |
pd | * | 0.01 ± 0.01a | 0.01 ± 0.03a | 0.02 ± 0.02a | 0.01 ± 0.01a | 0.02 ± 0.01a | 0.02 ± 0.03a | 5, 286 | 0.09 | 0.853 |
RA (%) | * | 5.88 ± 1.33b | 4.35 ± 1.35b | 2.44 ± 0.58a | 1.08 ± 0.35a | 2.17 ± 0.48a | 3.08 ± 0.25ab | 5, 286 | 6.25 | 0.036 |
iD | * | 0.03 ± 0.08a | 0.04 ± 0.05a | 0.03 ± 0.12a | 0.01 ± 0.08a | 0.04 ± 0.05a | 0.02 ± 0.03a | 5, 286 | 1.58 | 0.359 |
Archytas spp. | Pr (%) | * | 0.14 ± 0.06a | 0.72 ± 0.12ab | 0.47 ± 0.35a | 0.34 ± 0.18a | 0.93 ± 0.32ab | 1.31 ± 0.68b | 5, 286 | 3.85 | 0.043 |
pd | * | 0.01 ± 0.03a | 0.01 ± 0.03a | 0.02 ± 0.02a | 0.01 ± 0.02a | 0.01 ± 0.02a | 0.02 ± 0.01a | 5, 286 | 0.36 | 0.647 |
RA (%) | * | 5.88 ± 1.68b | 4.35 ± 1.23ab | 1.63 ± 0.58a | 1.08 ± 0.65a | 2.17 ± 0.66a | 3.08 ± 1.02a | 5, 286 | 4.05 | 0.048 |
iD | * | 0.03 ± 0.08a | 0.04 ± 0.02a | 0.01 ± 0.01a | 0.01 ± 0.03a | 0.04 ± 0.05a | 0.04 ± 0.03a | 5, 286 | 1.58 | 0.235 |
Bracon sp. | Pr (%) | 0.20 ± 0.2a | 0.14 ± 0.32a | 1.44 ± 0.57bc | 0.47 ± 0.35ab | 1.01 ± 0.28b | 1.85 ± 0.25c | 1.96 ± 0.38c | 6, 347 | 8.32 | 0.023 |
pd | 0.01 ± 0.03a | 0.01 ± 0.01a | 0.02 ± 0.03a | 0.01 ± 0.02a | 0.01 ± 0.01a | 0.01 ± 0.03a | 0.01 ± 0.02a | 6, 347 | 0.52 | 0.634 |
RA (%) | 13.33 ± 2.35b | 5.88 ± 1.38a | 8.70 ± 2.03ab | 1.63 ± 0.85a | 3.23 ± 0.38a | 4.35 ± 1.08a | 4.62 ± 1.12a | 6, 347 | 5.02 | 0.031 |
iD | 0.03 ± 0.12a | 0.03 ± 0.15a | 0.03 ± 0.18a | 0.01 ± 0.06a | 0.04 ± 0.08a | 0.07 ± 0.12b | 0.07 ± 0.18b | 6, 347 | 4.68 | 0.028 |
C. grioti | Pr (%) | * | 0.14 ± 0.35a | 0.72 ± 0.03a | 0.71 ± 0.09a | 1.01 ± 0.12b | 1.85 ± 0.65bc | 2.61 ± 0.35c | 5, 286 | 7.23 | 0.019 |
pd | * | 0.01 ± 0.02a | 0.01 ± 0.02a | 0.02 ± 0.01a | 0.01 ± 0.02a | 0.02 ± 0.02a | 0.01 ± 0.03a | 5, 286 | 0.95 | 0.324 |
RA (%) | * | 5.88 ± 0.123a | 4.35 ± 1.09a | 2.44 ± 0.68a | 3.23 ± 1.05a | 4.35 ± 1.09a | 6.15 ± 1.52a | 5, 286 | 1.23 | 0.135 |
iD | * | 0.03 ± 0.13a | 0.04 ± 0.11a | 0.03 ± 0.09a | 0.04 ± 0.14a | 0.04 ± 0.08a | 0.07 ± 0.08b | 5, 286 | 3.68 | 0.041 |
C. luteum | Pr (%) | * | 0.14 ± 0.15a | 0.72 ± 0.24bc | 0.47 ± 0.15b | 0.68 ± 0.19bc | 0.93 ± 0.26c | * | 4, 241 | 7.38 | 0.023 |
pd | * | 0.01 ± 0.02a | 0.01 ± 0.02a | 0.02 ± 0.02a | 0.01 ± 0.01a | 0.01 ± 0.02a | * | 4, 241 | 0.035 | 0.852 |
RA (%) | * | 5.88 ± 1.37a | 4.35 ± 1.29a | 1.63 ± 0.65a | 2.15 ± 0.54a | 2.17 ± 0.51a | * | 4, 241 | 2.08 | 0.118 |
iD | * | 0.03 ± 0.12a | 0.04 ± 0.28a | 0.01 ± 0.19a | 0.03 ± 0.26a | 0.04 ± 0.32a | * | 4, 241 | 1.95 | 0.109 |
C. icipe | Pr (%) | * | 0.14 ± 0.23a | 0.72 ± 0.35b | 0.71 ± 0.28b | 0.68 ± 0.25b | 1.85 ± 0.05c | 0.65 ± 0.14b | 5, 286 | 8.35 | 0.011 |
pd | * | 0.01 ± 0.01a | 0.01 ± 0.02a | 0.02 ± 0.02a | 0.02 ± 0.01a | 0.02 ± 0.01a | 0.01 ± 0.02a | 5, 286 | 0.032 | 0.625 |
RA (%) | * | 5.88 ± 1.09a | 4.35 ± 0.96a | 2.44 ± 0.51a | 2.15 ± 0.23a | 4.35 ± 0.32a | 1.54 ± 0.22a | 5, 286 | 2.09 | 0.075 |
iD | * | 0.03 ± 0.01a | 0.04 ± 0.05a | 0.04 ± 0.03a | 0.01 ± 0.12a | 0.04 ± 0.10a | 0.02 ± 0.09a | 5, 286 | 1.95 | 0.102 |
Lespesia spp. | Pr (%) | 0.10 | 0.14 ± 0.08a | 0.72 ± 0.07ab | 0.24 ± 0.07a | 0.34 ± 0.05a | 1.85 ± 0.59bc | 1.31 ± 0.18b | 6, 347 | 4.82 | 0.038 |
pd | 0.01 ± 0.01a | 0.01 ± 0.01a | 0.01 ± 0.02a | 0.01 ± 0.01a | 0.01 ± 0.03a | 0.02 ± 0.01a | 0.01 ± 0.03a | 6, 347 | 0.86 | 0.215 |
RA (%) | 6.67 | 5.88 ± 1.32b | 4.35 ± 0.28ab | 0.81 ± 0.05a | 1.08 ± 0.15a | 4.35 ± 0.51ab | 3.08 ± 0.28ab | 6, 347 | 4.36 | 0.041 |
iD | 0.02 | 0.03 ± 0.01a | 0.04 ± 0.01a | 0.01 ± 0.12a | 0.01 ± 0.05a | 0.04 ± 0.023a | 0.04± | 6, 347 | 1.03 | 0.247 |
M. testacea | Pr (%) | * | * | 1.44 ± 0.21a | 0.47 ± 0.21a | 0.34 ± 0.12a | 0.93 ± 0.31a | 0.65 ± 0.22a | 4, 249 | 0.68 | 0.234 |
pd | * | * | 0.01 ± 0.02a | 0.02 ± 0.02a | 0.1 ± 0.01a | 0.01 ± 0.01a | 0.01 ± 0.02a | 4, 249 | 0.026 | 0.567 |
RA (%) | * | * | 8.70 ± 1.69b | 1.63 ± 0.35a | 1.08 ± 0.41a | 2.17 ± 0.68a | 1.54 ± 0.65a | 4, 249 | 4.95 | 0.035 |
iD | * | * | 0.07 ± 0.23b | 0.01 ± 0.25a | 0.01 ± 0.31a | 0.04 ± 0.036a | 0.02 ± 0.23a | 4, 249 | 4.65 | 0.037 |
Ophion spp. | Pr (%) | * | * | 0.72 ± 0.35a | 0.47 ± 0.29a | 0.34 ± 0.09a | 0.93 ± 0.34a | 0.65 ± 0.19a | 4, 249 | 0.63 | 0.238 |
pd | * | * | 0.01 ± 0.02a | 0.02 ± 0.01a | 0.01 ± 0.02a | 0.01 ± 0.03a | 0.01 ± 0.02a | 4, 249 | 0.56 | 0.538 |
RA (%) | * | * | 4.35 ± 1.08a | 1.63 ± 0.85a | 1.08 ± 0.65a | 2.17 ± 0.57a | 1.54 ± 0.87a | 4, 249 | 0.68 | 0.215 |
iD | * | * | 0.04 ± 0.08a | 0.01 ± 0.06a | 0.01 ± 0.03a | 0.04 ± 0.02a | 0.02 ± 0.02a | 4, 249 | 0.95 | 0.312 |
*no collection, iD-index of distribution, pd-population density, Pr-parasitism rate, RA-relative abundance; means in the same row with the same letter are not statistically different |
Species Diversity Of Faw Predator
A total of 16 species of FAW arthropod predators were collected during this study. These were five heteropterans, Orius insidiosus (Anthocoridae), and Haematochares obscuripennis, Peprius nodulipes, Rhynocoris sp. and Zelus renardii (Reduviidae); four beetles, Calleida sp. (Carabidae), Cheilomenes sulphurea, Coccinella septempunctata and Cycloneda sanguinea (Coccinellidae); three earwigs, Euborellia annulipes, Forficula auricularia and Forficula senegalensis (Forficulidae); two ants, Pheidole megacephala and Polyrhachis lamellidens (Formicidae); one lacewing, Chrysoperla carnea (Chrysopidae); and one mantid, Mantis religiosa (Mantidae).
Except for O. insidiosus and Z. renardii, all the heteropteran species were collected from 2018 and had similar relative abundances and indices of dispersion during the collection years (Table 4). The beetle species were collected from 2017 and had similar relative abundance across the years of collection with slight increasing index of dispersion (Table 4). Except for E. annulipes, the earwig species were collected from the on-set of the FAW invasion with a slight increase of relative abundances and dispersion in the following years (Table 4). Ants collected were social Formicidae that increased in their locations found during the study. The lacewing C. carnea and mantid M. religiosa were collected in higher numbers during the first years of the FAW invasion in Togo, and their dispersion increased during the study (Table 4). Although the spatial distribution of predators annually increased (Fig. 5), the population densities of each species are similar.
Table 4
The predator species collected from 2016 to 2022 in Togo with their relative abundances and index of dispersions
Species | | 2016 | 2017 | 2018 | 2019 | 2020 | 2021 | 2022 | df | F | P |
H. obscuripennis | RA (%) | * | * | 3.80 ± 1.02a | 5.86 ± 1.25a | 3.96 ± 0.89a | 7.41 ± 1.58a | 5.29 ± 1.24a | 4, 249 | 0.85 | 0.253 |
pd | * | * | 0.02 ± 0.03a | 0.02 ± 0.01a | 0.01 ± 0.03a | 0.01 ± 0.02a | 0.01 ± 0.02a | 4, 249 | 0.68 | 0.694 |
iD | * | * | 0.07 ± 0.08a | 0.10 ± 0.02a | 0.11 ± 0.07a | 0.25 ± 0.06a | 0.2 ± 0.15a | 4, 249 | 0.67 | 0.152 |
P. nodulipes | RA (%) | * | * | 3.80 ± 1.05a | 4.39 ± 1.09a | 4.85 ± 1.09a | 5.93 ± 1.15a | 4.71 ± 1.22a | 4, 249 | 1.38 | 0.358 |
pd | * | * | 0.02 ± 0.02a | 0.01 ± 0.02a | 0.02 ± 0.02a | 0.02 ± 0.03a | 0.01 ± 0.02a | 4, 249 | 0.68 | 0.523 |
iD | * | * | 0.07 ± 0.08a | 0.10 ± 0.05a | 0.08 ± 0.15a | 0.18 ± 0.11a | 0.16 ± 0.08a | 4, 249 | 0.94 | 0.125 |
Rhynocoris sp | RA (%) | * | * | 5.06 ± 0.11a | 5.37 ± 0.08a | 3.96 ± 0.12a | 4.44 ± 0.09a | 4.71 ± 0.08a | 4, 249 | 0.28 | 0.358 |
pd | * | * | 0.01 ± 0.03a | 0.02 ± 0.02a | 0.02 ± 0.03a | 0.02 ± 0.01a | 0.01 ± 0.02a | 4, 249 | 0.32 | 0.428 |
iD | * | * | 0.11 ± 0.02a | 0.08 ± 0.08a | 0.07 ± 0.12a | 0.14 ± 0.07a | 0.13 ± 0.06a | 4, 249 | 1.08 | 0.240 |
Orius insidiosus | RA (%) | * | 5.88 ± 2.08b | 2.53 ± 1.08a | 2.44 ± 1.03a | * | 2.22 ± 1.03a | 2.94 ± 0.09a | 4, 215 | 3.95 | 0.045 |
pd | * | 0.02 ± 0.01a | 0.01 ± 0.03a | 0.02 ± 0.01a | * | 0.01 ± 0.02a | 0.01 ± 0.01a | 4, 215 | 0.32 | 0.726 |
iD | * | 0.03 ± 0.02a | 0.07 ± 0.08a | 0.04 ± 0.02a | * | 0.11 ± 0.12b | 0.09 ± 0.08ab | 4, 215 | 3.56 | 0.048 |
Z. renardii | RA (%) | * | 5.88 ± 2.04b | * | 1.46 ± 0.85a | 2.64 ± 0.65a | 2.22 ± 0.56a | 2.94 ± 0.68a | 4, 259 | 3.89 | 0.042 |
pd | * | 0.01 ± 0.02a | * | 0.02 ± 0.02a | 0.02 ± 0.01a | 0.01 ± 0.03a | 0.01 ± 0.02a | 4, 259 | 0.35 | 0.591 |
iD | * | 0.05 ± 0.05a | * | 0.03 ± 0.01a | 0.06 ± 0.08a | 0.11 ± 0.06a | 0.09 ± 0.09a | 4, 259 | 1.35 | 0.158 |
Calleida sp | RA (%) | * | * | * | 2.44 ± 1.34a | 3.52 ± 1.05a | 4.44 ± 1.63a | 4.71 ± 1.38a | 3, 222 | 1.86 | 0.354 |
pd | * | * | * | 0.01 ± 0.01a | 0.02 ± 0.02a | 0.02 ± 0.01a | 0.02 ± 0.02a | 3, 222 | 0.29 | 0.635 |
iD | * | * | * | 0.06 ± 0.08a | 0.06 ± 0.17a | 0.10 ± 0.09a | 0.11 ± 0.03a | 3, 222 | 0.96 | 0.358 |
C. sulphurea | RA (%) | * | 8.82 ± 2.38a | 8.86 ± 2.98a | * | 4.85 ± 1.54a | 9.63 ± 2.86a | 7.65 ± 2.34a | 4, 207 | 1.13 | 0.125 |
pd | * | 0.02 ± 0.03a | 0.02 ± 0.01a | * | 0.01 ± 0.04a | 0.02 ± 0.01a | 0.01 ± 0.03a | 4, 207 | 0.35 | 0.436 |
iD | * | 0.05 ± 0.21a | 0.15 ± 0.15ab | * | 0.11 ± 0.08ab | 0.25 ± 0.19b | 0.24 ± 0.13b | 4, 207 | 4.65 | 0.032 |
C. septempunctata | RA (%) | * | * | 15.19 ± 3.28a | 12.68 ± 3.02a | 15.86 ± 3.15a | 21.48 ± 3.58a | 18.24 ± 2.95a | 4, 249 | 1.61 | 0.325 |
pd | * | * | 0.02 ± 0.2a | 0.02 ± 0.01a | 0.02 ± 0.01a | 0.02 ± 0.02a | 0.02 ± 0.03a | 4, 249 | 0.09 | 0.832 |
iD | * | * | 0.19 ± 0.12a | 0.20 ± 0.08a | 0.24 ± 0.24a | 0.46 ± 0.15b | 0.36 ± 0.13b | 4, 249 | 5.14 | 0.036 |
C. sanguinea | RA (%) | * | 8.82 ± 2.05a | 10.13 ± 2.31a | 11.71 ± 2.57a | 10.13 ± 2.85a | 16.30 ± 3.21a | 15.29 ± 3.52a | 5, 286 | 1.59 | 0.085 |
pd | * | 0.02 ± 0.1a | 0.03 ± 0.03a | 0.02 ± 0.01a | 0.02 ± 0.03a | 0.02 ± 0.01a | 0.01 ± 0.03a | 5, 286 | 0.87 | 0.791 |
iD | * | 0.05 ± 0.05a | 0.11 ± 0.08a | 0.16 ± 0.15a | 0.20 ± 0.34ab | 0.40 ± 0.04b | 0.42 ± 0.09b | 5, 286 | 5.34 | 0.041 |
E. annulipes | RA (%) | * | * | 3.80 ± 1.02a | 6.34 ± 2.21a | 4.85 ± 1.05a | 6.67 ± 1.91a | 9.41 ± 0.34a | 4, 249 | 1.58 | 0.086 |
pd | * | * | 0.03 ± 0.02a | 0.02 ± 0.02a | 0.02 ± 0.01a | 0.03 ± 0.04a | 0.02 ± 0.01a | 4, 249 | 1.12 | 0.062 |
iD | * | * | 0.04 ± 0.02a | 0.10 ± 0.07a | 0.10 ± 0.02a | 0.11 ± 0.12a | 0.2 ± 0.05a | 4, 249 | 0.58 | 0.124 |
F. auricularia | RA (%) | 15 ± 3.28b | 5.88 ± 0.23a | 7.59 ± 0.15a | 10.24 ± 2.04ab | 11.45 ± 1.58ab | 9.63 ± 2.58ab | 11.18 ± 2.65ab | 6, 347 | 4.31 | 0.042 |
pd | 0.02 ± 0.03a | 0.02 ± 0.02a | 0.02 ± 0.01a | 0.03 ± 0.02a | 0.02 ± 0.01a | 0.02 ± 0.04a | 0.01 ± 0.01a | 6, 347 | 0.89 | 0.085 |
iD | 0.03 ± 0.08a | 0.03 ± 0.017a | 0.15 ± 0.06ab | 0.10 ± 0.22ab | 0.15 ± 0.21ab | 0.29 ± 0.05b | 0.29 ± 0.09b | 6, 347 | 5.35 | 0.035 |
F. senegalensis | RA (%) | 25 ± 3.25b | 8.82 ± 2.13a | 16.46 ± 2.18ab | 15.12 ± 3.28ab | 18.50 ± 2.96ab | 17.04 ± 3.08ab | 18.24 ± 3.85ab | 6, 347 | 4.35 | 0.047 |
pd | 0.02 ± 0.01a | 0.02 ± 0.03a | 0.02 ± 0.02a | 0.03 ± 0.02a | 0.02 ± 0.01a | 0.02 ± 0.03a | 0.01 ± 0.01a | 6, 347 | 0.93 | 0.075 |
iD | 0.05 ± 0.12a | 0.05 ± 0.17 | 0.15 ± 0.21ab | 0.19 ± 0.24ab | 0.25 ± 0.19b | 0.36 ± 0.09b | 0.29 ± 0.31b | 6, 347 | 4.85 | 0.039 |
P. megacephala | RA (%) | * | Social | Social | Social | Social | Social | Social | * | * | * |
pd | * | Social | Social | Social | Social | Social | Social | * | * | * |
iD | * | 0.08 ± 0.07a | 0.22 ± 0.14ab | 0.20 ± 0.12ab | 0.18 ± 0.08ab | 0.40 ± 0.15c | 0.31 ± 0.07b | 5, 286 | 7.25 | 0.015 |
P.s lamellidens | RA (%) | Social | Social | Social | Social | Social | Social | Social | * | * | * |
pd | Social | Social | Social | Social | Social | Social | Social | * | * | * |
iD | 0.08 ± 0.04a | 0.22 ± 0.16b | 0.15 ± 0.08ab | 0.30 ± 0.05bc | 0.30 ± 0.16bc | 0.43 ± 0.31c | 0.42 ± 0.24c | 6, 347 | 6.28 | 0.028 |
C. carnea | RA (%) | 60 ± 8.35c | 47.06 ± 5.22b | 22.79 ± 4.32a | 21.95 ± 4.62a | 15.42 ± 3.75a | 18.52 ± 4.35a | 18.82 ± 3.29a | 6, 347 | 12.42 | < 0.001 |
pd | 0.01 ± 0.02a | 0.02 ± 0.01a | 0.03 ± 0.01a | 0.02 ± 0.03a | 0.02 ± 0.03a | 0.03 ± 0.4a | 0.02 ± 0.01a | 6, 347 | 1.02 | 0.071 |
iD | 0.15 ± 0.24a | 0.22 ± 0.32a | 0.15 ± 0.28a | 0.32 ± 0.15b | 0.32 ± 0.19b | 0.36 ± 0.28b | 0.38 ± 0.024b | 6, 347 | 6.35 | 0.031 |
M. religiosa | RA (%) | 30 ± 3.65b | 26.47± | 15.19 ± 2.38ab | 13.17 ± 2.85ab | 10.13 ± 3.52a | 9.63 ± 2.69a | 11.18 ± 3.50a | 6, 347 | 5.36 | 0.044 |
pd | 0.02 ± 0.02a | 0.01 ± 0.02a | 0.02 ± 0.01a | 0.01 ± 0.03a | 0.01 ± 0.02a | 0.01 ± 0.02a | 0.02 ± 0.01a | 6, 347 | 0.42 | 0.534 |
iD | 0.05 ± 0.08a | 0.22 ± 0.08b | 0.44 ± 0.12c | 0.29 ± 0.24b | 0.30 ± 0.06b | 0.36 ± 0.16bc | 0.29 ± 0.17b | 6, 347 | 8.12 | 0.026 |
*no collection, iD-index of distribution, pd-population density, RA-relative abundance; means in the same row with same letter are not statistically different |