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Ecosystem Services Case Study: Alyssum

Case studies provide narratives or stories through which teachers can create connections between learning, scientific research, the socio-scientific issues that scientists are working to understand and address, and the lives of young people and their families.

Alyssum: Delivering an ecosystem service

alyssum ecosystem services

Flower Power: Alyssum

Alyssum or Sweet Alyssum is an easy to grow plant that creates a carpet of flowers low to the ground. The botanical name for Alyssum is Lobularia maritima. 

Known for its properties as a beneficial insect plant, it is often planted in home gardens, but more importantly is used extensively to provide ecosystem services, increasing biodiversity in agricultural ecosystems.    

Alyssum provides food (nectar and pollen) for natural predators such as wasps and hover flys, helping them to thrive and reproduce so that they can kill the pests that could damage the crops. 


A floral fight against green terrorists: Flower-power fights pests in the Waikato    


Alyssum: Protecting Grapevines from the leafrollers


Leafrollers are one of the major pests of grapevines in New Zealand and Australia. Leafroller refers to the larval or caterpillar stage  of a number of moth species. The larvae feed on grapes, flowers and stalks causing a reduction in yield. More importantly the damage caused by the larvae encourages the spread of a fungal disease, Botrytis cinerea or grey mould. This reduces grape yield but also affects the flavour and ageing of the wine. 

Traditional control of leafrollers is through frequent spraying of insecticides. Sprays are applied when more than 5% of the bunches of grapes have one or more caterpillars. There are three problems with this approach.

  • Firstly notice how the caterpillar rolls the leaf edges together and joins them with a web. This structure makes it very difficult for pesticide sprays to come in contact with the pest. 
  • The second problem is that spraying results in pesticide residues in the grapes. Society is increasingly demanding fewer pesticide residues in food, which requires a different approach to controlling the caterpillars.  
  • Finally, the pesticide will kill natural enemies within the ecosystem. 

To understand how natural predators such as parasitic wasps and hoverflies control pests like leafrollers we need to be familiar with the typical insect life cycle. This life cycle is for an insect showing complete metamorphosis. Some insects like aphids undergo incomplete metamorphosis, where the eggs hatch into nymphs, which then mature into adults.
The adult (the flying stage) feeds only on nectar and pollen. Nectar contains carbohydrate, which provides energy for the adults. Pollen provides protein, which is necessary for egg production. Together they increase the life span and the number of offspring produced by the parasitic wasps and hoverflies. Hence it is important to ensure that there is a good supply of nectar and pollen producing plants for the adult.
The eggs of parasitic wasps and hoverflies are laid inside the body of the host—in this case the leafroller caterpillars. When the eggs hatch the larvae consume the caterpillar from the inside out, eventually causing it to die. By this time the larvae is ready to change into a cocoon and then emerge as an adult to continue the cycle.


The main natural predator of leafroller is the parasitic wasp Dolichogendea tasmanica. Technically D. tasmanica is an endoparasitoid—meaning that lives inside its host.  

Agricultural ecosystems tend to be low in biodiversity, with simplified food webs. Ecosystems in this state lack the food resources, such as nectar and pollen needed by the adult stage of the parasitoids that are important in controlling pests like leafroller. Parasitoids need access to sufficient and appropriate food to ensure survival and gain maximum reproduction (fecundity). In order to ensure that natural biological control agents are as effective as possible we need to understand how increasing biodiversity improves the efficacy of the agent. This has been the focus of much of the research carried out at the Bio-Protection Research Centre. One study looked at the specific effects of providing alyssum flowers as a food source for the parasitoid D. tasmanica on its longevity and fecundity. 

Alyssum results

These results showed that providing D. tasmanica with access to alyssum flowers increased the lifespan and fecundity (reproductive capacity) of the parasitoid. An increase in longevity allows the parasitoids more time to attack their hosts, the leafrollers, therefore making them a more efficient biological control agent. 

The other interesting finding to come out of this research was, that in the absence of floral resources, the sex ratio of D. tasmanica became very male-biased. However, in the presence of alyssum flowers the sex ratio was closer to the ideal of 1:1. These results again show how the lack of appropriate floral resources in an agricultural ecosystem can affect the population dynamics and potentially the efficacy of natural predators.


Berndt, L. A., & Wratten, S. D. (2005). Effects of alyssum flowers on the longevity, fecundity, and sex ratio of the leafroller parasitoid Dolichogenidea tasmanica. Biological Control, 32(1), 65-69.