Inside the World’s Most Diverse Garden

Inside the World’s Most Diverse Garden

September 7, 2016

Visited by more than a million tourists each year the Kew Royal Botanical Gardens are one of London’s top attractions with the world’s largest and most diverse collection of living plants. Sara Redstone, plant health and quarantine officer at Kew, discusses the importance of plant science tools, such as crop protection products and Integrated Pest Management, to keep the garden in good condition as well as safeguard rare and endangered plants.

What plant science tools does Kew use to maintain the gardens?

We use a large portfolio of biological control agents (for example, we produce our own beneficial predatory beetles called Atheta to combat sciarid flies and thrips and use wasps to eat pests) as well as traditional plant protection products. We try to minimize the use of chemical products through Integrated Pest Management but it’s our duty to make sure we protect and conserve our plant collections in the most appropriate way and this sometimes includes judicious use of chemicals. Our collections are at risk otherwise.

Our tree manager, for example, uses a range of tools from pruning to ultrasound technology to monitor and maximize the health of our trees – making them more resilient to pests and diseases. We must understand tree growth and aging; ultrasound allows us to look at vital signs. But sometimes, plant protection products are necessary, especially with ecologically or economically important species.

Last year, our oak trees got infested with a Lepidoptera pest. We have a massive collection of oak trees and this pest likes oak. Fortunately, due to reports of nearby infestations, we received early warning and prepared for the pest. We combatted it with a plant protection product, which was very effective. About 500-700 other species depend on oak in the U.K. so it’s an important tree in our ecosystems.

What is the process that new plants undergo for garden introduction?

We aim to inspect everything new coming into the gardens, which must undergo quarantine for an extended period of time. Just because something looks healthy doesn’t mean it’s clean. Orchids sent from Asia, for example, were quarantined for six months before a weevil appeared. In this case, we destroyed the plants because they were too high risk to our collection. Even though a phytosanitary certificate was issued before these plants left their country, a pest infected them along the way.

Because of the risk of such traveling pests, all material destined for living collections is thoroughly checked regardless of phytosanitary certificates and subject to plant protection products. Infestations of aphids are continuously emerging, for instance, so we often have to spray for them.

We also manage a number of plants on behalf of customs. Plants protected by the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) are sometimes collected by people from the wild illegally, seized by customs officers and then sent to us for analysis. They often arrive in a poor state. For example, a recent CITES plant we received had to be treated with a fungicide and an insecticide to revive it.

Since plants are introduced to Kew Gardens in good condition, are pest infestations rare?

No, unfortunately. Just like schools and hospitals are at greater risk for germs, public gardens such as Kew can be put at risk as unseen plant pests or disease-causing organisms can be introduced unintentionally by visitors (Kew has 1.6 million a year!). It’s inevitable that we will get problems in spite of the stringent control measures that we have in place. We do our best to manage them responsibly.

Also, the climate is changing so pests are changing as well. Some insect pests are changing their distribution, or becoming more aggressive as a result. Kew has a huge amount of biodiversity – some of it is intentional and beneficial, but some is not.

To what extent are plant protection products used at Kew?

We use a number of plant protection products on a regular basis. If we did not have them, the breadth of our collections, plant quality and our capacity to deliver conservation and research would suffer. It is not possible to effectively manage a botanic garden such as Kew organically. We are trying to grow healthy plants and chemicals are part of that process. For instance, we have outbreaks of ants on occasion. We rely a lot on biologicals to control them but if they fail, we turn to plant protection products. We must have as comprehensive a toolbox as possible.

How do you manage potential resistance to plant protection products?

With all pesticides, we look at chemical families and choose ones with the least risk of resistance. But we will consider higher risk chemicals in case of emergency such as with cigarette beetles in rare palm species from Florida that were highly resistant to a wide range of insecticides. We also time our use of chemicals wisely.

Our challenge is trying to manage emerging threats as our pool of chemicals shrinks because of tightened regulations driven in part by public concern. Unfortunately, the public doesn’t fully understand our need for plant protection products. People think the only way to manage plants is to not use these products at all. But some plants wouldn’t survive without them. We must have the right tools available to use in the right place at the right time – wisely and appropriately.

What else does Kew Gardens do to protect biodiversity?

We have a range of science- and conservation-based activities around the world, such as in Madagascar, to conserve local biodiversity. We assess what is there and determine how to manage plants. For example, we look after the health of pollinators and use natural products, such as plant extracts and other plants, to protect harvested food stuffs. We also have a conservation biotechnology unit that works with endangered species, plus one of the largest seed banks in world. Kew is a big organism!

Can you tell me about the seed bank?

Called the Millennium Seed Bank Partnership, we work with partners (governments, agencies, communities, individuals and NGOs) worldwide to save seeds as insurance against their risk of extinction in their native habitat. We also hold material for other seed banks and help other countries develop seed banks. Our goal is to conserve as many plant species as possible, especially endangered, endemic and economically important ones. Working with partners in 80 countries, we have banked over 13 percent of the world’s wild plant species and we hope to increase that to 25 percent by 2020.

One in five plants face threat of extinction per Kew’s 2016 State of the World’s Plants report. Why?

There are many factors involved – the main ones being changes in land use and the impact of invasive species. Others include illegal trade, pollution, global warming, pests and diseases. Some species find it hard to adapt to changing conditions – just like some of us, some plants don’t cope well with change.

What are the findings of Kew’s 2016 report related to agricultural plants?

The implications for agriculture is that we need to be more aware of our source materials and how we manage resources like water. For example, we should stop trying to grow things that require a lot of water in drought areas. Instead, we should grow things in the right place. Also, we focus on a dozen crops as our main food sources when there are about 5,500 edible plants available. It would seem sensible if we looked at other crops and what’s most appropriate for our climactic conditions.  Kew scientists are actively researching these “crop wild relatives.”

What can individuals do to help?

First, do not bring back plants from holidays, especially not in the name of conservation – unless you have all the necessary permits and resources to manage it! There is a risk of introducing new insect pests and diseases.

Also, garden. Develop sustainable landscapes. If you see a neglected space, see if you can help develop it. Mix exotic plants with indigenous species to encourage beneficial insects and pollinators. Increasing plant biodiversity improves pest control.

We all need to be environmentally responsible – both collectively and individually. There is no Planet B. This is the only one we have and we need to look after it. We rely on plants. Why is it so hard for us to see them? Society seem to have plant blindness. It’s bewildering that people don’t appreciate plants more. We’re happier and healthier when we’re close to green surroundings. We need to cherish our greenery.