Information for primary producers in South Australia
Grey-headed Flying-foxes will take cultivated fruits, including banana, grapefruit, guava, lychee, mandarin, mango, mulberry, persimmon, pome fruit (apple, pear) and stone fruit (nectarine, apricot, plum and cherry).
Grapes in commercial vineyards do not appear to be targeted; as the low stature of vines may discourage bats from foraging on them. Pruning fruit trees to maintain low stature may also deter bats.
Signs of flying fox damage include broken branches, fruits punctured with teeth or claws, soiled fruits and fruit remains under trees.
Just like managing bird damage to crops, the use of fixed nets covering entire crops is the most effective means for preventing bat damage. Netting individual trees or fruits is also effective.
Netting excludes bats, other mammals (including possums) and birds (e.g. parrots), and reduces hail and sun damage and insect damage. A mesh size of 48 mm allows access to crops by insect pollinators.
Establishing and maintaining crop netting may not be economically feasible for some growers, such as for smallholdings and growers in areas where damage is infrequent. However as larger orchards have netting installed, pressure on un-netted smaller orchards may increase and be exasperated by other factors, including drought or habitat destruction elsewhere.
A cost-benefit calculator for installing permanent netting is available for growers in the Adelaide Hills. This tool was developed by the Apple and Pear Growers Association of South Australia, with support from the Adelaide and Mount Lofty Ranges Natural Resources Management Board, to aid growers to assess the financial viability of orchard nets.
It may be possible for Grey-headed Flying-foxes to become entangled in netting when trying to access fruit. It is important that extreme care needs to be taken to ensure landholders do not get bitten or scratched when trying to untangle animals. As a result, we suggest that land managers contact Fauna Rescue to carry out this work.
Bats may be deterred from fruits with strong smells, such as rotting fish or smoke, loud noise such as gas-operated bird scare guns, and flashing or rotating lights. However, the effect of these techniques may only be temporary and they do not necessarily deter bats from returning later.
In the Adelaide Hills some growers have succeeded in scaring bats away from crops. They used light and noise deterrents during the first four hours after sunset, when bats first arrived, and sustained these measures for five consecutive evenings.
Why culling is ineffective
Culling bat populations is not a practical tool for reducing crop damage. Great mobility means that the effects of culling are spread thinly across the entire bat population. Effects are also only temporary, because flying foxes easily and rapidly re-occupy control areas.
Culling also goes against international and national conservation priorities. Shooting bats is considered unacceptable because they are often wounded rather than destroyed instantly, contravening the Animal Welfare Act 1985. Dependent young at the camp also starve if lactating females are targeted in controls.
Destruction permits are not available to control Grey-headed Flying-foxes in South Australia.