Contributed to by Daniel Dynan
As discussed in our last greenhouse management article (A New Age of Greenhouse Management: The onset of Earthship greenhouses and their necessity as a household utility), it was explained that the greenhouses in Earthships require a different level of participation than that of traditional greenhouse management. The planters function to provide the Earthship’s inhabitants with food but also cleans the water that cycles through. The planters serve as the household’s utilities. While there is a heightened level of involvement within the greenhouse, there are still challenges. Host insects are an obstacle that we have experienced in our Earthship’s greenhouses. The plants in the greenhouse are subject to various different host insects that can cause damage or kill plants if the state is serious enough.
Daniel Dynan has been working with Earthship Biotecture for about 2 years now. As part of our staff, he spends much of his time working with the greenhouses in various buildings at our headquarters, including our Visitor Center. Dan is working on projects here that involve the integration of natural pests to help curb the populations and effects of host insects on the plants in our greenhouses.
We have experienced different host insects such as mealy bug, scale, white flies, aphids and spider mites– just to name a few. In order to help prevent or diminish these populations in the greenhouse we use beneficial predatory insects that naturally help to cure the plants.
Recently, there was an issue at the Education Facility involving a banana plant infested with scale (this particular species of scale is the European fruit lecanium). The insect that was introduced into this situation was the small golden wasp known as Aphytis melinus, which is a parasite of different species of scale. The scale secretes a honeydew sap and is harvested, and spread by ants that are patrolling the plant. For the ants, this is a good resource for them in their colony. Unfortunately, we have not found a natural predator for the ants to help further reduce the spreading of the scale.
The following insect war took place within a time period of 5-10 minutes. The video recorded and edited by Dan, takes place in the greenhouse at the Earthship Visitor Center on a banana tree leaf. You are watching as the wasps are introduced and are laying their eggs in the scale and the reaction from the ants.
You can purchase these Aphytis melinus (wasps) that can and do lay their eggs in scale. The issue is that there is a third party that is involved in this which are the ants in the greenhouse because they use harvest and eat the honeydew that is secreted out of the scale on the plants. When the wasps show up, the ants are militant – disciplined, highly focused and trained. The speed, accuracy and force that they have is instinctual. Within 30 seconds of the wasps being released on the plant, the ants were already maiming them and calling for reinforcements. They started to thin their numbers first by crippling the wasps – once their numbers were crippled and not as much as a threat anymore, the ants came in and started to eat them to clear their highway. Any wasp that went beyond a certain point was attacked. Damage control was then done to the scale the ants checked to see if the scale was still alive.
Unfortunately for the plant, the wasps’ numbers were depleted by ants that were protecting their food source. Not all the wasps were wiped out by this battle but it shows how the relationships within these insects and the plants and the greenhouse plants are carried out.
Maintenance of your greenhouse should be done organically because of the idea of food production. By using chemicals in the greenhouse like insecticides, you are basically rendering your greenhouse useless by subjecting the food production to synthetic products. The pests are a natural form of management and wont harm the crops or generate any kind of negative effects in the greenhouse. Depending on the type of insect that is introduced, it could also benefit by acting as a pollinator.
The older and more established the greenhouse is, the more conducive it is for those host insects to show up and it could all start from one plant. This particular greenhouse, which is around two years old, did not show any signs of host insects until more recently. We are constantly experimenting with different natural forms of pest management to determine what remedy will work the best and where.
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