Natural Predators in the Vineyard Webinar

RVF webinar, hosted by Programme Director Becky Sykes, in association with the Porto Protocol, with:

• Dr Tom Croghan, the Vineyards at Dodon, Maryland, USA
• João Raposeira, Tapada de Coelheiros, Alentejo, Portugal
• Eleanor MacDonald, Cal Poly Humboldt, California, USA

This webinar from April 2025 is an excellent resource for anyone interested in learning how to encourage natural predators to control pest populations.

Most importantly…

1. Avoid monocultures… retain or introduce as many different elements of green infrastructure as possible to balance your ecosystem
2. Go for the win-wins… provide habitats for raptors, bats, songbirds and beneficial predatory insects to keep the rodents, moths and other pests in check

Tom Croghan on working with nature to balance your ecosystem:

1. Avoid monocultures (yes, we know we said this above but it is definitely worth repeating)… avoid monocultures. If the only thing growing is grapes, then all the pests will eat your grapes!
2. Work out what your pests’ natural habitat is and try removing it. Tom was struggling with Pierce’s disease and found that removing the sycamore trees reduced the presence of the leafhopper vectors. Replacing with aromatic plants, elder and willow provides natural habitat for their predators
3. Work out what will eat your pests and encourage them to do so. The spotted lantern fly was becoming a local threat and he found out that they weren’t being eaten by their natural predators. By collaborating with a local university he found out that the non-native flies were feeding off non-native ailanthus trees which were making them taste “like hydrogen sulphide on steroids”. So by removing those trees, the flies “feed off alternative hosts making them delectable to the birds”.
4. Encourage avian diversity: songbird boxes help reduce insect populations; bat boxes originally brought in to reduce mosquitos for visitors also help reduce cicadella species too; kestrel boxes initially to disrupt the flights of starlings which peck fruit at harvest also help reduce the rodent population.
5. Pigs to diversify the understorey
6. You never ‘win’. It’s a continuously evolving balance of pests and predators…

João Raposeira:

1. Avoid monocultures (starting to become a mantra now, but worth repeating)… avoid monocultures. Build your trophic levels…
2. Introduce bird and bat boxes as bioindicators so that you can monitor the species present. Your landscape should be providing plenty of habitat – rebuild green infrastructures to provide conditions for birds, bats and insects to make shelters, balancing the ecosystem
3. Include cover crops with different flowering cycles to attract beneficial insects
4. Plant indigenous trees, bushes and plants in the middle of the vineyard with the same flowering period as the vine cycle to attract different species of insects which will predate main pests like cicadella
5. Provide water sources for insect, birds and mammals. At last count Coelheiros had 93 different species of birds and aiming to reach 100 at the next count…
6. Check out the webinar for João’s matrix of birds, when they are present, what they eat and what part of the estate they are on.

Eleanor MacDonald is researching song birds in vineyards and is part of the team at Humboldt who are also researching barn owls.

On song birds:

1. Song birds eat vineyard pests: yes, they’ve done fecal analysis and they’ve found several species of leafhoppers and mealybugs
2. You can put song bird nest boxes in even the most homogenous landscape and the birds will inhabit them, often in just one year
3. They prefer freestanding north-facing boxes, with predator guards, at least 25m away from wooded areas
4. Maintaining cover crops in the vineyard provides foraging habitat
5. There doesn’t seem to be an increase in damage to grapes from the birds

Next stage of songbird research:

1. Investigating the effect of different vineyard management practices – with the caveat that these are hard to tease apart in dynamic working landscapes
2. Analysing diets to find out if they’re eating beneficial species of insects too

On barn owls:

1. A family of barn owls will eat 3,000 to 4,000 rodents per year: gopher activity decreased by 14%, vole and mouse activity decreased by 26%
2. Barn owls hunt 30-40% of the time on your vineyards, the rest of the time in other parts of the landscape – you will be doing your local community a service by putting up nest boxes
3. They prefer tall, wooden nest boxes in an open area that are cleaned out every autumn when they’re not actively nesting

Worried that regen practices give hiding places to rodents? Well maybe you shouldn’t be… hot off the press study… found that maintaining cover crops favours acoustically-attuned predators due to the rustling sounds of rodents – the most important thing is timing of mowing.