Food Insecurity and Metal Type Experiments on Crops

Abstract

The rise in food insecurity and toxicity of pesticide have created a demand for home grown organic produce. Alternative to pesticides like penny barriers have been used as snail deterrents who forge on crops. The experiment was designed to study how different metal types affects whether snails will cross a surface or barrier. We hypothesized that metal type affects whether snails will crawl across a surface and predicted that the number of snails that crawled over the penny barrier would be lower compared to the number that crawled over the aluminum barrier and the no barrier. Snails were collected and placed in petri dishes with 3 types of barriers; 3 mm of aluminum, pennies and a no barrier. The average number of snails that crossed the aluminum barrier, the no barrier and the penny barrier was 2.4, 1.8 and 0.0 respectively. Pennies are made of 2.6% copper and when molluscs crawl over them it creates elevated amounts of copper and creates a toxicological interaction.

Introduction

Large farming companies use chemical pesticides to deter pests from damaging produce, leading to inevitable chemical pesticide residue in final produce presented to consumers. Chemical residue has been shown to create serious health problems and environmental contamination (Ecobichon, 2001) which has caused food insecurity in consumers. This insecurity is partially remedied by consumer knowledge of where their food came from and how it was grown thus, creating a demand for locally grown and organic produce.

One of the states experiencing a large demand for locally grown and organic produce is California. In California many people have created community gardens and grow a small amount of produce in home gardens (Gray, 2014.) However, they face the same problems large farming companies face when growing produce. That problem is damage to produce caused by unwanted pests. One of the main pests are snails. Snails chew holes in plants and feed on fruits and vegetables leaving them inedible (Waki 2017.) Snails more specifically terrestrial snails are part of phylum mollusca and flourish in damp places with moist soil, making underneath plants perfect spots for them. They secrete mucus that helps them adhere to surfaces, making it easier for them to adhere to plants while they eat them (Newar et al. 2015). In order to address this problem without the use of pesticides, home garden communities have opted for alternative methods of snail deterrents. A popular deterrent or barrier used to control snails are pennies, since snails have been observed to avoid crawling on them (Long, 1996).

This experiment was designed to study how different metal types affects whether snails will cross a surface or barrier. We hypothesized that metal type affects whether snails will crawl across a surface. We also predicted that if metal types affects whether snails will crawl across a surface then the number of snails that crossed the penny barrier will be lower than the number of snails that cross the aluminum barrier and the no barrier.

Methods and Materials

A total of 19 snails were collected for the experiment. Three treatments were created to determine the number of snails that crawled over different metal type surfaces. Three petri dishes lined with a thin 3mm strip of metal down the middle were used to simulate the barrier. One petri dish had an aluminum barrier, another a penny barrier and one with no barrier. Snails were chosen at random and a single snail was placed inside the petri dish on one side of the barrier. On the opposite side of the barrier five leaf disks were placed as bait. After 1 hour leaf disks were counted to determine whether the snail had crossed the barrier. The experiment was replicated five times. Constant variable during the experiment included: room temperature, randomized snail, number of leaf disks, and a 1-hour window for snail movement. The independent variable was metal surface barriers and the dependent variable was the number of snails that crossed the barrier. A comparison of means during the experiment was analyzed to determine a statistical difference and 95% CI.

Results

The average number of snails that crossed the aluminum barrier, the no barrier and the penny barrier was 2.4, 1.8 and 0.0 respectively (Table 1.) There was a significant difference (P

Figure1. Mean number of snails that crawled over different types of metal barriers over a time of 60 minutes. The central horizontal lines represent the means and the error bars represent the 95% confidence interval (n=5/treatment).

Table 1. Number of snails that crawled over different metal type barriers; Aluminum, No barrier and Penny. (n=5/treatment) LCL and UCL are lower and upper confidence limits for the 95% CI.

95% Cl	No Barrier	Penny
means	2.4	0.0
SE	1.8	0.00
LCL	1.82	0.000
UCL	1.10	0.000
Aluminum	0.812	0.00
	0.490
	0.775
	0.820
	4.02

Discussion

The data indicated a significant difference between the number of snails that crossed the aluminum barrier and the no barrier compared to the penny barrier. The data matches the prediction thus, the hypothesis was supported. Similarly, other studies suggest that the brown slug and the two-striped slug which are also in the phylum Mollusca were repelled by physical barriers composed of copper (Hata et al. 1997). Molluscs require copper as an important trace element however an excessive amount of copper can become toxic (Dallinger et al. 2005). Since pennies are made of 2.6% copper, when the snails tried to crawl over the penny barrier their mucus provided a path for copper ions concentration to increase in their bodies. Thus, creating toxicological interaction. This can explain the observed significant difference between the number of snails that crossed over the aluminum and no barrier compared to the barrier compose of pennies.

Literature Cited

1. Leslie Gray, Patricia Guzman, Kathryn Michelle Glowa & Ann G. Drevno (2014) Can home
2. gardens scale up into movements for social change? The role of home gardens in providing food security and community change in San Jose, California, Local Environment, 19:2, 187-203.
3. Donald J.Ecobichon, 2001. Pesticide use in developing countries. Toxicology
4. Volume 160, Issues 1–3, Pages 27-33
5. TsukasaWaki Diversity of terrestrial mollusks and their helminths in artificial environments in
6. Yoyogi Park, Tokyo, Japan Journal of Asia-Pacific Biodiversity Volume 10, Issue 2, 1 June 2017, Pages 254-256
7. Meester, Steven (2006) 'The Economic Implications of Price Rounding,' Major Themes in
8. Economics, 8, 1-9.
9. Studies on the Adhesive Property of Snail Adhesive Mucus Janu Newar and Archana Ghatak
10. Langmuir 2015 31 (44), 12155-12160
11. ' Coping with slugs and snails ', Journal of Pesticide Reform, 1996 Vol. 16, No. 1, pp. 22-23
12. Copper in Helix pomatia (Gastropoda) is regulated by one single cell type: differently responsive metal pools in rhogocytes
13. Reinhard Dallinger, Monika Chabicovsky, Elisabeth Hödl, Caroline Prem, Peter Hunziker, and Claudia Manzl
14. American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 2005 289:4
15. Cited
16. https://www.cabdirect.org/cabdirect/abstract/19562900716
17. https://patents.google.com/patent/US4756116A/en
18. http://manoa.hawaii.edu/ctahr/farmfoodsafety/wp-content/uploads/2011/01/Hata_1997_Crop-Protection.pdf
19. https://www.huffingtonpost.com/quora/why-are-snails-and-slugs_b_3155291.html
20. https://setac.onlinelibrary.wiley.com/doi/pdf/10.1002/etc.5620050905

Combining molluscicides with slug barriers would reduce slugs foraging onto benches thus decreasing dependency on the barrier alone. For example, under ideal conditions our tests indicated that an effective molluscicide, such as Deadline Granules, is about 80% effective. After combining molluscicides and copper barriers, the number out of 100 slugs actually passing the copper barrier would be less than one, or 0.6 slug per bench leg: 20 (% survivors of molluscicides) x 0.03 (proportion of K cubensis passing barrier) = 0.6. Although molluscitides are highly effective under wet conditions when slugs are actively foraging, our study indicates that molluscicide persistence is reduced under these wet conditions. The efficacy of copper barriers is also reduced when wet (Godan, 1983). Therefore, the addition of a fiberglass barrier below the copper barrier will provide added security under wet conditions. 

Cite this page