Nets can be used to cover crops and provide a barrier for wildlife access. Ten different articles, each presenting 1-3 sub studies, have evaluated different types of netting to prevent wildlife damage to crops. In most cases, the wildlife was represented by different types of birds, but bats, deer and primates were also among the species for which netting was implemented to prevent damage.
One study from India (Arora et al. 2023) found that poly netting prevented bird damage on guava during the rainy season at the crop development stage (RR = 0.02) and ripening stage (RR = 0.05), as well as during the winter season at the crop development stage (RR = 0.02) and ripening stage (RR = 0.03) in comparison to a control. Another Indian study (Dar et al. 2022) implemented netting to prevent damage from rose-ringed parakeet (Psittacula krameria) on sunflower seeds and found that the intervention prevented all damage in two treatment sites (RR = 0) in comparison to control fields. A third Indian study (Kler 2007) found that netting reduced rose-ringed parakeet losses of safflower capsules (n = 7) in treatment blocks in comparison to the control (n = 41). Netting has also been shown (Patyal and Rana 2005) to reduce bird damage on grapes in India (RR = 0.02). Furthermore, Plastic Xironets and Fishnets effectively protected fields at eight trial sites in five African countries from bird damage, reducing the risk of damage (RR = 0.04 – 0.16) and resulting in increased yield weights (Bruggers and Ruelle 1982).
However, netting should likely be applied with care to avoid damage from the net to the crop. In a fifth Indian study (Swaminathan and Verma 2000) the use of a green nylon net (19 mm mesh) reduced the number of damaged date fruits per palm tree slightly in comparison to the control palms. When a 2mm mesh wire gauge netting was used the damage increased by 94 fruits per palm, and a black nylon net (8 mm mesh) caused the number of damaged fruits to more than double in the treatment palms in comparison to the control (+ 179 damaged fruits/palm).
Netting is also used to prevent damage from mammalian wildlife. Tollington et al. (2019) observed that nylon netting reduced lychee fruit loss to Mauritius fruit bats (Pteropus niger) in comparison to the control (R = 0.12) in their Mauritian study. A study from Sumatra (Campbell-Smith et al. 2012), Indonesia, implemented a 5 x5 cm square mesh stitching nylon tree netting to prevent damage by orangutans (Pongo abelii) which increased the average jangol yield by 107 kg, while the mean jangol yield in the control decreased by 17.6 kg. In contrast, a study from South Africa (Linden et al. 2019) concluded that nylon mesh netting Macadamia nut trees to prevent damage from monkeys and birds, but at nighttime also preventing access of bats, reduced the yield of nuts in human made and natural habitats, when netting was undertaken 24 hours and during the night. The reason for the reduced yield was due to insect damage which would otherwise be prevented by the fenced wildlife. Only when netting of trees was undertaken in a natural setting during daytime only (when bats were inactive) was the yield greater in the treatment than in the control setting.
