This story originally appeared in the February 2017 edition of Grapegrower & Winemaker.
Most assessments of viticultural pests don’t take into account, other than birds, anything bigger than a Light Brown Apple Moth, but for those in the path of larger animals the damage can be devastating.
There are about 80 introduced animal species that have established significant wild populations across mainland Australia, and many of them have become pests to farmers. Vineyards have not been spared from damage caused by introduced species, and growers have turned to the only solution available – significant fencing infrastructure.
Keeping them out
“The losses have gotten so bad here we’ve had to take drastic action. On the western side of the freeway most people have had to put up deer fences,” said Warren Smith from Pyramid Wines in Queensland’s Granite Belt.
Not only is this an expensive solution, it also impacts the views of open, rolling vineyards which have been important for building tourism appeal and increasing visitor numbers.
Jeff Harden from Bungawarra Wines (another Granite Belt property) is now setting up electric fencing along his boundaries, even though he was initially reluctant because it affects the aesthetics.
“The deer here are a very destructive pest. It is only reluctantly that I’m fencing the vineyard, it is inconvenient and spoils the open nature of the place, but it has become increasingly necessary. I have been told that it is effective, but I’ll find out,” Harden said.
“Shooting is not a good way to manage them, if a deer’s in scrub you could walk 10 meters past it and not see it.”
Harden is still not convinced he’s found the complete fix for his problem; even after four hot wires, metre-and-a-half high posts and an earth.
Invasive animals like deer and wild pigs have been a consistent issue, but recently it became impossible to ignore.
“They just got into my block of Traminer, it was a prized block and I lost a quarter of it. They had been in other blocks but then they discovered the Traminer. It ripens earlier and they just destroyed the crop,” he said.
Harden had avoided netting, which he considered an ineffective solution which could be damaged easily by the deer’s antlers; but as the deer numbers rose and losses grew he reassessed his position.
“It was a visibly attractive place, I’ve tried to get the most aesthetic fencing I could; but the openness was the attraction,” he said.
While native animals have been known to cause some damage in vineyards; introduced species, such as wild deer and pigs, can be highly destructive.
“Deer go through and strip where the shoots are between seven to 25cm. They cut everything back to about half an inch and we pretty much lose everything,” said Franco D’Anna, from Hoddles Creek Estate in Victoria’s Yarra Valley.
Deer species have followed a familiar invasive species pattern; with small initial infestations extending in geographic range and in population density, followed by new outlying populations becoming established then growing until eventually all suitable habitat is infested with large numbers.
In the Yarra Valley the deer target the vines early in the season and eat the young shoots, then return in February and March as the grapes are ripening. Initially outer rows and edges are most susceptible.
“Finally the local council have realised there’s an issue and have applied to the State Government for help,” D’Anna said.
State authorities work with landholders to ensure any funds applied to manage pest animals are used as effectively as possible, but long-term answer will hopefully be delivered by the federal authorities who have additional resources to foster innovation in this field.
“Deer go through and strip everything back to about half an inch and we pretty much lose everything.”
There are a growing number of products and services to better manage pest animals available to land managers; such as sentinel devices that can recognise pest species or species of interest on one way gateways within exclusion fencing or to alert land managers to the presence of pest animals on their properties.
While new lethal (chemical) and non-lethal (fertility control) population management tools are being researched in collaboration with Australian and International organisations.
Management of invasive species
“We had to fence our whole lot, because they give you the shits, you close the gate on a block at night and come back and half the blocks eaten. It doesn’t look that pretty but at least deer fence keeps them out,” D’Anna said.
“We deer fenced 60 acres, as soon as we had some time we would go and do a bit, over three years we did the whole block. It’s expensive but once you’re done it’s there, doesn’t cost you anything else except for maintenance.”
For deer, fencing is the only reliable solution until other control programs start to make an impact. Exclusion fencing is effective at three-to-six foot high, if it includes electric fencing; otherwise the non-electric options are 12-foot high barriers.
Poison baiting is another option, though many growers don’t find it useful; noise deterrents are often quickly adjusted to and ignored; while taste deterrents that can be applied to vines only last for short periods.
Targeted shooting does reduce populations and scares away animals but it is not always a practical solution for growers – and does require an additional skill set.
“Hunting is hard, there’s a real skill to it. There’s lots of scrubby grass, only get them when there in the open,” Smith said.
“I’ve got motion sensor cameras. It’s a good way to get to know where they are, I give that data to hunters. You can get mobs of 50 west of highway.”
Management of the estimated 200,000 wild deer in Australia is a contentious issue, due to their pluralistic status as a protected game resource in Victoria and introduced pest.
There has been little research into home-range sizes and seasonal movements in Australia, but modelling suggests all deer species currently occupy a fraction of their potential distribution in Australia and have great capacity to expand.
The four main species of feral deer in Australia are Sambar, Red, Fallow and Hog Deer. Each follows a daily pattern of behaviour, spending the daylight hours in, or close to, thick cover but emerging at dusk to feed and returning to cover at or soon after dawn.
“Shooting is not a good way to manage them, if a deer’s in scrub you could walk 10 meters past it and not see it. They’re all hiding in bush so you never find them,” D’Anna said.
Recreational hunting is not an effective means of controlling invasive animals
“I don’t want protection gone because you get rouge shooters shooting off the road who don’t know where the houses are.”
Recreational hunting is not an effective means of controlling invasive animals, however, the Invasive Animals Cooperative Research Centre said the use of skilled volunteer shooters, recruited and inducted through community hunting organisations under government management, can be one effective tool in an integrated pest control program.
Smith is also highly cautious about who is shooting around his property, only allowing the son of the former owner to hunt.
“He knows the property and where to hunt, sometimes we end up with some Venison in the freezer. Probably shoot two or three a year off our property, and I get a couple, and we shot five pigs last month. Others have a much bigger issue,” Smith said.
It can be hard to know what attracts the pests in the first place, deer and pigs are averse to tannins so damage to grape bunches tends to be concentrated in the lead up to vintage, it also appears to not be the same deer returning with a taste for grapes.
“Only two or three do damage, but two or three in each block means we could have six all up. Even if you shoot one there always a replacement, so I don’t think it’s the same ones who have gotten a taste,” D’Anna said.