Damage by Limicolaria species on maize, environmental factors influencing their population dynamics and potential strategies for their management in Cameroon

Introduction

Maize (Zea mays L) known as corn in the United States and Canada, is the third most important cereal grain worldwide after wheat and rice (Golob, et al., 2004) [1] . It is referred to as the cereal of the future due to its nutritional value and utilization of its products and by-products (Suleiman, 2013). It is the most commonly produced staple food crop in Sub-Saharan Africa (SSA), providing food and livelihood for around 208 million people (Parihar et al., 2011; Macauley, 2015) [2,3] and accounting for 73% of calorific intake (Shiferaw et al., 2011) [4] . It is a major source of income for many farmers in sub Saharan Africa (Achancho, 2013) [5] . Globally, maize is multipurpose crop with about 67% of it used for livestock feed, 25% for human consumption and industrial purposes and 5% for seed purposes for the next crop (Pardey et al., 2014) [6] . Maize is grown in varied soil types across a wide range of agro-ecological zones from wet to hot semi-arid lands. In Cameroon, maize is widely grown in all the regions and serves as the primary source of food for the majority of the population who consume it the roasted, baked, fried, pounded or fermented forms (Agbato, 2003; Giller et al., 2021) [7,8] . It is also used in many traditional dishes (koki corn, corn chaff, corn fufu and pap) as well as drinks (corn beer and sha). Maize is also a major source of livestock feed and fodder, food staple and source of livelihood in many parts of the world. Despite the importance of maize, its production suffers from a number of constraints which include poor soil fertility, environmental degradation, diseases, several insect pests (Kamara et al., 2014) [9] and molluscs such as slugs and snails. In Cameroon, the Limicolaria species of the family Achatinidae (Floyd et al., 2007) [10] , have emerged as the most important molluscs pest of maize and other food crops most probably due to favorable environmental conditions particularly the long rainy season that runs from Mid-March to mid-November. These snails have conical shells which typically exhibit a range of colours from brown to gray, often adorned with darker bands or stripes; they often grow to around 5-7 centimeters in length and possess a muscular foot that aids in their locomotion (Odafe-Shalome et al., 2020) [11] . Several factors affect the ecology and seasonal distribution of Limicolaria snails including geo-physical factors such as rainfall, temperature, light and hygrometry of the atmosphere, chemical factors like ion concentration in the soil as well as biological factors such as availability of food, competition and predator-prey interactions (Ofoezie, 1999; Owojori et al., 2006) [12, 13] . Limicolaria species are predominantly polyphagous phytophagous snails known to occur in abundance in forest edges and modified habitats such as plantations and farms (Raut & Barker, 2002) [14] . A majority of these snails are non-host specific and can consume at least 500 different types of plants, including cassava, cocoa, papaya, peanut, banana, beans, okra, cucumber, melon, and cereals like maize, and sorghum (Venette and Larson, 2004) [15] . Members of this genus have been reported to damage palm fruits and leguminous cover crops in Cameroon and may even be a greater pest than Achacatina fulica and A. marginata, (Mead A.R and Palcy L., 1996; Okolle et al., 2019) [16,17] . Limicolaria snail species are highly adaptive to a wide range of environmental conditions and are capable of modifying their life cycle to suit local conditions. These snails inhabit damp, shady sites and swamps and hence their populations may significantly increase during the rainy season. They usually live in holes, beneath leaf litter or under pebbles and rocks from where they come out to feed at nights (Manyangadze et al., 2021) [18] . Limicolaria snail activities differ from one species to another and the activity is influenced by external factors such as temperature, humidity, light intensity, soil conditions and food supply (Tan & Clements, 2011) [19] . Moisture also influences the activity of Limicolaria snails. They remain in their hides during the day and often after dusk they emerge to go in search of food. A decrease in light intensity with a fall in temperature below 21ºC and a rise in humidity through dew fall at dusk cause them to move on to vegetation, while in the morning and during the day the snails return to the upper soil or between the earth clods where it is cool and shady (Venette and Larson 2004) [20] . Since nails prefer moist and humid environments, the humid rainforest ecosystem with its characteristics long and extremely moist rainy season therefore offers suitable conditions for the survival and proliferation of diverse Limicolaria snail species. However, the lack of research attention paid to these Limicolaria species in the face of climate variability and change has allowed these mollusks to emerge as serious pests of many crops including maize particularly at its extremely vulnerable seedling and early vegetative stages. The present study therefore aimed at assessing The Limicolaria snail species abundance and diversity in maize fields planted during the first and second cropping seasons in the humid rainforest ecological zone of Cameroon as a first step to developing sustainable management methods for this pest. The ultimate objective of this study was to identify the different Limicolaria snail species attacking maize and to assess their monthly and seasonal population dynamics as well as determine the climatic factors influencing these variations.

Materials and Methods

Study area

This ecological studies were carried out from January 2020 to December 2023 in the Teaching and Research Farm of the Faculty of Agriculture and Veterinary Medicine, University of Buea, Cameroon. Buea is located at the foot of Mount Cameroon at an altitude of 870 m above sea level between latitudes 4 0 3 " N and 4 0 12"N and longitudes 9 0 12 " E and 9 0 20 " E and has rich volcanic, rocky soils. The temperature range is 20 0 C -32 0 C and an annual rainfall of 1800-3090 mm with an average relative humidity of 86% (John, et al., 2007) [21] . Buea is in the rainforest ecological zone that has an equatorial-tropical rainforest climate with a rainy season from mid-March to mid-November and a dry season from mid-November to mid-March. The site is in a mountainous region with varied topography of gentle slopes, hills and valleys which plays a role in water drainage, soil erosion and microclimatic conditions. The vegetation types include rainforests, agricultural fields and plantations that provide habitat for various animal species. Agriculture is a major economic activity in Buea especially in the Teaching and Research Farm of the Faculty of Agriculture and Veterinary Medicine where varied crops like maize, beans cassava, plantains and vegetables are cultivated annually.

Land preparation and planting of maize

The land for the study was prepared for the first time from late January to early February 2020. A 380 m 2 piece of land subdivided into 20 experimental units of 3m by 4m each separated from each other by 1m alley was used for the study. The land was cleared and allowed for two weeks for the emergence of new weeds, before it was it sprayed with a systemic herbicide Glyphader ® (active ingredient, glyphosate) as first application using 100 mL/16 L of water in a knapsack sprayer and maize planted with minimal tillage. Maize was planted during the first (March) and second (September) cropping seasons in 2020 and 2021. One kg of certified seeds of the medium maturing maize variety UBNMS001 from the University of Buea were planted at a planting distance of 75 × 50 cm inter and intra row spacing respectively at 5 cm depth. Three seeds were sown per stand and seedlings later thinned to two per stand at one week after germination. Granular inorganic fertilizer NPK (20:10:10) was applied at 10 g per plant on all experimental at two weeks after germination. Chemical weeding with the contact herbicide-Gramazone (active ingredient, Paraquat) as second application was done at 50 days after planting using 75 mL/16L knapsack sprayer and supplemented by manual weeding using a hoe when needed.

Sampling of Limicolaria snail species through trapping

Quadrat-litter and baited pitfall traps were used in each experimental plot as described by Southwood et al., (2000) [22] . For the quadrat method, 2.5 kg dry grass (straw) were used to cover the ground surface of each 3 m x 4 m rectangular plot to a thickness of 3 cm which served as the litter trap placed in the 20 experimental units. The distance of one trap from another was 50 cm apart. Once each week, the straw was carefully lifted at the four angles and the center of each plot and the Limicolaria snails found bet beneath were hand-picked, counted and then destroyed; this was done for two consecutive years. For the pitfall baited traps, a repurposed 1.5 L plastic bottle was cut into halves of 12 cm high and the bottom half used as a trap. Two opposite holes of 2 cm diameter each were created on two sides at 1cm below the brim to prevent overflow if and whenever it rained. Forty of these plastic halves were used in total. Two of these traps were buried one at the center and the other at the edge of each 3 m x 4 m experimental units such that the brims flushed with the ground surface. Each of the traps was half-filled with 150 mL of fermented maize chyme (Sha) that served as bait to attract the Limicolaria snails. These traps were serviced twice each week and the baits replaced to ensure its effectiveness throughout the production cycle. During servicing, the content of each trap was carefully drained through a sieve and the Limicolaria snails then counted and recorded weekly. The number snails caught in the litter and pitfall traps was then summed up to give the total number of snails in the field. All observations of the traps were done from 7.00 -8.00 am when it was cooler and the soil still wet enhancing easy capturing of the snails since they were still active during the morning period just from dawn. Sampling of the snails began one week after germination till the crop maturity stage at twelve weeks after germination. All trapped snails were collected from the traps by hand picking once every week, destroyed and discarded after laboratory identification. Sampling was done twice weekly throughout the rainy and dry seasons and the data then cumulated on a monthly from January to December of 2020 and 2021. On the other hand, monthly temperature, rainfall and relative humidity data for Buea were also collected from the National Observatory on Climate Change Center of Buea (NOCC, 2021) [23] for the two years.

Identification of Limicolaria species

After trapping and collection of the snails from the field, they were taken to the laboratory for identification and differentiation to the various species based on diagnostic features such as; shell shape, colouration, shell strands pattern, height and width according to the guides of Emberton, 2010; Tan and Low, 2011 [24, 25] .

Relative abundance of Limicolaria species in maize fields

During the population dynamics study, the relative abundance of the four different species were determined whereby the total number of individual Limicolaria species caught was divided by the total number of the four different Limicolaria species and multiplied by 100.

Statistical analysis

Limicolaria species population dynamics data for each of the traps were reported using line graphs. Correlation graphs were also drawn using Microsoft excel 2016 and Pearson's Correlation Coefficient calculated using SPSS software version 16 and Excel 2016 to determine the relationship between the population abundance and the different climatic factors. All data were tested at 5% probability level.

Results

Description of Limicolaria species damage on maize

Limicolaria species are a serious yearly problem on maize and cause considerable damage on maize plants. These snails damage mostly the leaves, stems, ears, fruits (kernel) and dead plant parts of the maize crop from the seedling to the mature stage. They damage maize by chewing irregular longitudinal or horizontal, translucent/window-like holes on the leaves through scraping with their rasp-like tongues (Fig. 1 a andb). They mostly feed from the underside of the leaves and often leave behind a silvery gray shiny slimy mucus trail, which is often a clear indication of the snail activity, even if when they are not seen on the plants. The snails also leave unusual droppings, feaces or frass near the damage areas (Fig. 1 b). They are primarily active at night, and the fresh damage is often noticed in the morning when the snails have retreated into their hiding places till when it is foggy or dark. Their feeding is distinctive from those other pests in that, they eat from the middle of the maize leaves whereas caterpillars often eat from the edges.

Limicolaria numidica

L. numidica (Reeve, 1848) snail attained a height of 65 mm and a width of 28 mm, with 9-9.5 whorls at maturity. The shell is smooth, dull, oblong-ovate and displays faint brownish colour bands/strands on the shell (Fig. 2 c).

Limicolaria aurora

L. aurora (Jay 1889) snail generally attained a height of 60 mm and a width of 28 mm, with 9-9.5 whorls at maturity. The shell is also smooth, creamish-white, oblong-ovate and displays no colour bands/strands on the shell (Fig. 2 d). Among these four, the following three species of L. zebra, L. flammea and L. numidica were more prominent and abundant in the fields as compared to L. aurora which was least abundant.

Relative abundance of Limicolaria species in the maize fields in Buea

Irrespective of the maize growing season, the most abundant snail species was Limicolaria zebra (47%); its population was always doubled that of any other species in the research field. The next abundant species was L. flammea (21%) which was not very significantly different from L. numidica (20%) then L. aurora (12%) which was the least (Fig. 3).

Population dynamics of Limicolaria snail species

Generally, the annual population abundance of the snails, in 2020 and 2021 of the different Limicolaria species had a domebell shaped (Fig. 3). Though the trends of the total numbers caught both in years were the same, slightly higher numbers were caught in 2020. There were two population troughs for both years, the first trough around January/February and another one around November/December. There was a major peak in July and August each year. From January, the population increased steadily with corresponding rainfall, then peaks in July and August from when the population gradually dropped to zero in December to February, which corresponded to the period of the dry season (Fig. 4).

Discussion

A total of 20734 Limicolaria snails were collected in 2020 and 2021 belonging to the following four species, L. zebra, L. flammea, L. numidica, and L. aurora. This shows that these snails are well adapted to living and reproducing in the humid rainforest ecological zone of Cameroon. This area has a tropical equatorial climate with a long rainy season from mid-November to mid-March which favours the lush growth of different plant species to sustain this diverse and abundant snail populations. Some of the Limicolaria species that were abound in humid forest agro-ecological zone of Cameroon correspond with some which have been identified and reported elsewhere in the neighboring Nigeria (Odafe-Shalome et al., 2020) [26] . This is a further proof that these snails are well adapted to surviving and reproducing in the humid rainforest areas of West and Central Africa. The abundant rainfall and diverse vegetation cover in the humid rainforest provides appropriate moisture levels and shelter for the snails to thrive. Ahmed and El-Wakei, (2012) [27] stated that snails preferred habitats rich in vegetation and moisture because such environments contain soil salts, nutrient and food supply such as calcium carbonate, which help in the formation of solid shells. Irrespective of the maize growing season, the most abundant snail species was Limicolaria zebra whose population was always doubled that of any other species followed by L. flammea, which was not very significantly different from L. numidica and the lowest was L. aurora. The population densities of these species may vary with geographical location, soil types and other environmental conditions both biotic and abiotic. For example, Ebenso et al., (2006) [28] identified Limicolaria flammea as one of the least abundant species in Nigeria because of the species poor adaptive nature. The very high populations of L. zebra in the maize fields maybe due its relatively high reproductive and/or survival rate, which have contributed to it being a dominant species in the maize fields. Due to the relative high populations of this dominant species in the fields, it is likely that most of the damage observed on the maize plants is inflicted by this species. Since the Limicolaria species are native to West Africa (Tan and Clements, 2011) [19] , their current high feeding on maize to constitute pest problems may have been due to the reduction/elimination of some of their natural host plants in favor of the current abundant maize crops in this agroecological zone. Host plant abundance is known to induce host preference in insects (Ntonifor et al., 1996) [29] which might have also been the case with these snails. These maize plants and/or plant debris provide shelter while the maize shoots, leaves and ears serve as appropriate food for the snails.

During the rainy season, the numbers of snails increased gradually to a peak around July and August which coincides with the peak of the rainy season because land snails in general thrive best in humid environments with abundant food sources which corroborates the observations of Ahmed and El-Wakei (2012) [27] that snails like other animals tend to prefer habitats with abundant food supply. The long rainy and moist rainy season with abundant food supply most likely led to increased reproduction and hence higher snail populations in accordance with the findings of Silva and Omena (2014) [30] and Mohan et al., 2015 [31] . These findings corroborate those of kumari et al., (2007) [32] and Justin et al., (2008) [33] who reported that the rainy season was most favorable for snail activity amongst all factors. The litter traps caught higher numbers of snails compared to the baited pitfall traps presumably because the litter served as suitable sheltered microhabitats with high humidity where land snails thrive best. Though higher numbers of snails were collected from under the litter traps, the fermented cornmeal chyme (Sha) lures used in the pitfall traps showed good prospects that it can be used as a locally produced attractants that can be used to lure the snails to a particular spot of the field for targeted killing and/or easy collection for destruction as a component of integrated management of the snails in farms. This is in line with Linda et al., (2019) [34] and Godlove et al., (2023) [35] who reported that regular capture and destruction of snails is an effective control measure in snail population reduction from reaching damaging thresholds. Farmers can therefore be sensitized and trained to adopt such an effective, economical and environmentally friendly snail control method rather than using different synthetic molluscicides to control Limicolaria species as reported by Okolle et al., (2019) [36] . The highest numbers of snails were caught in July and August, which is the peak of the rainy season. This is consistent with the positive correlation between the numbers of snails and the amount of rainfall as well as relative humidity. During the rainy season, there is increased plant growth and diversity thus offering abundant varied food sources for the snails to feed on, grow and reproduce thereby leading to a rapid population buildup. Often, the higher the amount of rainfall, the higher the environmental humidity which is an additional favorable factor for the survival of snails. In contrast, from December to February corresponding to the peak of the dry season with increased dryness and environmental temperatures, the snails go into aestivation underneath the soil, stones and debris in agreement with the studies of Okolle et al., (2019) [36] and Limunga et al., (2020) [37] . This underscores why there was a negative correlation between the number of snails and environmental temperatures, which corroborate the findings of Stensgaard et al., (2006) [38] . This study has generated vital basic ecological information that can be exploited to develop sustainable management strategies for Limicolaria species in maize and other crop fields. For example, Litter and baited pitfall traps were suitable methods for quantifying the population of these pests and hence can be used to monitor or sample and control these snails in maize fields. The environmental factors of temperature, rainfall and relative humidity can be used to predict periods of their high and low populations. This can be exploited in a cultural practice of altering the maize planting dates to avoid the early more susceptible early growth stages of the crop coinciding with the peak population periods of the snails as a component of the integrated management of these polyphagous pests. The usual planting periods in the humid forest agro-ecological zone is March/April for the first planting and August/September for the second planting. It would therefore be ideal to plant the first season maize in March at the onset of the rainy season when the snail population is very so that the more susceptible early vegetative stages of the maize are passed before the snail population begins to increase significantly during the later stages of the rainy season. In contrast, the second planting period is around when the snail populations are highest (July and August). Therefore, it would be more sensible to plant in early September when the snail populations start declining. Furthermore, prior to planting during this second season, it will be ideal to also establish pitfall and litter traps in the farms to continuously trap and further decrease these snail populations in the farms during the early vegetative stages of the crop.

Conclusion

Four different Limicolaria species namely: L. zebra with a population almost double that of L. flammea >, L. numidica > L. aurora were identified in maize fields highlighting that the Limicolaria species are emerged perennial pests in maize fields. Their populations were significantly influenced by climatic variabilities of temperature, rainfall and relative humidity. There was a negative relationship between mean annual temperature and total number of the snail but a positive association between rainfall and relative humidity and the total number of Limicolaria. Litter and baited pitfall traps were suitable methods for quantifying the population of this pest and hence can be used to monitor or sample and control these snails in maize fields. The environmental factors of temperature, rainfall and relative humidity can be used to predict periods of their high and low populations. This can be exploited to alter maize planting dates to avoid the early more susceptible growth stages of the crop coinciding with the peak population periods of the snails as a component of the integrated management of these pests.

Acknowledgement

AcknowledgmentsThe authors acknowledge educational and material assistance from the Faculty of Agriculture and Veterinary Medicine, University of Buea.

References

1. Golob P, Kutukwa N, Devereau A, Bartosik RE, Rodriguez JC, Hodges R, et al. Crop post-harvest: science and technology. Blackwell Science Ltd; 2004. 2(1).
2. Parihar CM, Jat SL, Singh AK, Sai Kumar R, Hooda KS, Chikkappa GK, et al. Maize production technologies in India. DMR Technical Bulletin. Directorate of Maize Research, Pusa Campus, New Delhi; 2011. 30(1):110-112.
3. Macauley H. Cereal crops: rice, maize, millet, sorghum, wheat. Background paper -An action plan for African agricultural transformation. Feeding Africa Conference, Dakar, Senegal; 2015 Oct 21-23. United Nations Economic Commission for Africa.
4. Shiferaw B, Prasanna B, Hellin J, Bänziger M. Feeding a hungry world: past successes and future challenges to global food security in maize. Food Security. 2011;3:307-327.
5. Achancho V. Review and analysis of national investment strategies and agricultural policies in Central Africa: the case of Cameroun. In: Elbehri A, editor. Rebuilding West Africa's food potential. FAO/IFAD; 2013.
6. Pardey PG, Andrade RS, Hurley TM, Xudong R, Liebenberg FG. Returns to food and agricultural R&D investments in sub-Saharan Africa, 1975-2014. Food Policy. 2016;65:1-8. https://doi.org/10.1016/j.foodpol.2016.09.009
7. Agbato SO. Principles and practices of crop production. Oyo: Odumatt Press Publisher; 2003. p. 57-62.
8. Giller KE, et al. Small farms and development in subSaharan Africa: farming for food, for income or for lack of better options? Food Secur. 2021;13:1-24.
9. Kamara AY, Ewansiha SU, Menkir A. Assessment of nitrogen uptake and utilization in drought-tolerant and Striga-resistant tropical maize varieties. Arch Agron Soil Sci. 2014;60:195-207. doi:10.1080/03650340.2013.783204
10. Floyd J, Roda A, Robinson DG. New pest response guidelines: giant African snails (Achatinidae). USDAAPHIS-PPQ-Emergency and Domestic Programs; 2007. p. 3-13.
11. Odafe-Shalome GIO, Omoyakhi JM. Inventory and characteristics of the small African land snail (SALS) spp in Benin metropolis, Edo State. Niger J Anim Prod. 2020;47(5):66-76.
12. Ofoezie IE. Distribution of freshwater snails in the manmade Oyan Reservoir, Ogun State, Nigeria. Hydrobiologia. 1999;416:181-191.
13. Owojori OJ, Asaolu SO, Ofoezie IE. Ecology of freshwater snails in Opa Reservoir and Research Farm Ponds at Obafemi Awolowo University Ile-Ife, Nigeria. J Appl Sci. 2006;6(15):3004-3015.
14. Raut SK, Barker GM. Achatina fulica Bowdich and other Achatinidae as pests in tropical agriculture. In: Barker GM, editor. Molluscs as crop pests. Hamilton, NZ: CABI Publishing; 2002. p. 55-114.
15. Venette RC, Larson M. Mini risk assessment of giant African snail, Achatina fulica (Gastropoda: Achatinidae). Dept. of Entomology, Univ. of Minnesota, St. Paul; 2004. p. 1-30.
16. Mead AR, Palcy L. Two giant African land snail species spread to Martinique, French West Indies. Veliger. 1992;35(1):74-77.
17. Okolle NJ, Bernadette TCL, Yawa ME, Mercy NAD, Mathias MA. Spatial distribution and seasonal variation of Limicolaria spp. infesting banana plantations in South West, Cameroon. World J Adv Res Rev. 2019;3(2):36-45.
18. Manyangadze T, Chimbari MJ, Rubaba O, Soko W, Mukaratirwa S. Spatial and seasonal distribution of Bulinus globosus and Biomphalaria pfeifferi in Ingwavuma, KwaZulu-Natal, South Africa. Parasit Vectors. 2021;14:1-9.
19. Tan SK, Clements GR. Limicolaria flammea (Müller, 1774): another potentially invasive African land snail in tropical Asia. Trop Conserv. 2011;4(1):97-102.
20. Venette RC, Larson M. Mini risk assessment: giant African snail, Achatina fulica (Gastropoda: Achatinidae). Dept. of Entomology, Univ. of Minnesota, St. Paul; 2004. p. 1-30.
21. John P, Ian DE, Robert WP, Laszlo N. Zonation of forest vegetation and soils of Mount Cameroon, West Africa. Plant Ecol. 2007;192:251-269.
22. Southwood TRE, Henderson PA. Ecological methods. 3rd ed. Oxford: Blackwell Science; 2000.
23. NOCC. National Observatory on Climate Change Cameroon-Buea. https://onacc.cm. 2020.
24. Emberton KC, Rakotondrazafy JA. Rhytidoidea land snails collected in 2007 at 21 sites in northern Madagascar with descriptions of 13 new species. Basteria. 2020;84(4-6):170209.
25. Tan SK, Martyn L. Update on Limicolaria flammea (Müller, 1774) in Singapore and its distinction from Achatina fulica Bowdich, 1822. Natl Univ Singapore. 2011;4:311-317.
26. Odafe-Shalome GIO, Omoyakhi JM. Inventory and characteristics of small African land snail (SALS) spp in Benin. Niger J Anim Prod. 2020;47(5):66-76. doi:1280ArticleText-2139-1-10-20201228-1
27. Ahmed S, El-Wakeil N. Biological and ecological studies on land snails and their control. In: Integrated pest management and pest control. 2012. p. 413-444.
28. Ebenso I, Ita B, Umoren E, Ita M, Binang W, Edet G, et al. Effect of carbamate molluscicide on African giant land snail Limicolaria aurora. J Appl Sci Environ Manage. 2005;9(1):99-102.
29. Ntonifor NN, Jackai LEN, Ewete FK. Influence of host plant abundance and insect diet on host selection by Maruca testulalis and Riptortus dentipes. Agric Ecosyst Environ. 1996;60:71-78.
30. Silva ECD, Omena EP. Population dynamics and reproductive biology of Achatina fulica in Salvador-Bahia. Biota Neotrop. 2014;14(3). https://doi.org/10.1590/16760603000414
31. Mohan L, Agarwal M, Kumari P, Kumar N. Population dynamics of Achatina fulica and correlation with weather parameters. Entomology Dept, RAU, Pusa (Samastipur); 2015. 10(4):1489-1492.
32. Kumari P, Agarwal ML, Kumar N. Population dynamics of Achatina fulica and correlation with weather parameters. Bioscan. 2015;10(4):1489-1492.
33. Justin CGL, Leelamati M, Johnson SBN, Thangaselvabai T. Seasonal incidence and management of Achatina fulica on vanilla. Pest Manag Econ Zool. 2008;16(2):235-238.
34. Amoah LAO, Anyan WK, Aboagye-Antwi F, Abonie S, Tettey MD, Bosompem KM. Environmental factors and seasonal variations of schistosomiasis snail hosts in Weija Lake, Ghana. 2019.
35. Bunda WG, Peters MK, Green AE, Daniel BET, Kenko DNB, Fairo FD, et al. Seasonal and environmental dynamics of freshwater habitats and Bulinus snails in Tiko, Mount Cameroon. 2023;18(10):112-21.
36. Okolle JN, Lum NMC, Ngosong C, Tatanah NL, Tanyi C, Sakwe NP, et al. Efficacy of four plant emulsions against long tail mealybug (Pseudococcus longispinus) in Cameroon. J Zool Entomol Stud. 2018;6:837-843.
37. Limunga TBC, Ekwa YM, Afui MM, Okolle NJ. Molluscicidal action of metaldehyde, oxamyl, potassium nitrate and botanicals against Limicolaria spp. Int J Sustain Agric Res. 2020;7(3):143-153.
38. Stensgaard AS, Jorgensen A, Kabatereine NB, Rahbek C, Kristensen TK. Modeling freshwater snail habitat suitability and disease transmission in Uganda. Geospat Health. 2006;1:93-104.