Kaolin clay dust
The olive fruit fly (Bactrocera oleae)
Let’s talk about the olive fruit fly a bit before talking about our counter-actions. Because for us, this is a ‘special’ insect and pest… For pretty much any other pests out there on our property we simply try to be patient and let mother nature figure it out. A predator might be sent in (birds, wasps, etc.) to balance things out. Or it might be a message to us that something is off with the soil or that the plant we are trying to grow is just not meant for our climate and situation.
With the olive fruit fly this approach is nonsense though for our setup. It is like cancelling all of our olive harvest or being OK with very low quality olive oil.
This fly punctures the olives and lays their eggs into the olives. In the following stage, the larvae feed on the fruit of olive trees. Once the olives have been punctured, there is no remedy to save the harvest.
Damaging of the olives
Wikipedia summarizes the damages very nicely (source: https://en.wikipedia.org/wiki/Olive_fruit_fly) “The damages caused by the olive fruit fly are of two types: quantitative and qualitative. From a quantitative point of view, the damage is caused by larvae of second and especially third stages, by the removal of a significant proportion of the pulp which as a consequence results in reduction in the yield of olives. Part of the production is also lost due to premature falling of the attacked fruit. Olive bites and holes dug by the larvae in the initial phase do not have a significant impact on the yield. In table olives, however, the damage extends to the sterile punctures, which cause the variation in production. A qualitative aspect to be considered is the significant deterioration in the quality of the oil extracted from olives with a high percentage of attacks by larvae of the third stage. The oil obtained from infected olives has a high acidity level (expressed as oleic acid, from 2% to 10% depending on the percentage of the infestation) and a lower shelf life as it has a higher peroxide value. Secondarily qualitative impairments of varying severity derive from the olive fruit fly attacks due to the arrival of mold through the eclosions. This deterioration in quality is evident in significantly flawed oils obtained from olives harvested from the ground or stored for several days before pressing.”
Preventive actions – Kaolin Clay
Needless to see that there is tons of pesticides against the olive fruit fly out on the market. But this is not for us. So instead we are using traps and caolin clay.
Surround sign – looks like we are doing something dangerous here But they are just trying to educate & promote…
Olive fruit fly trap
We use the traps mainly as a measurement tool so that we are applying the kaolin clay at about the right time, when populations and "pest pressure" start to increase.
So what is this stuff? Clay, just clay. As the name suggests. However, it is so finely pulverized that together with a sticking agent (a vegetable oil) it will dust and cover all of the trees’ surfaces, not only the olives but also leaves, stem and branches.
This fine powder is highly irritating for insects, including the olive fruit fly and if coverage is good they will leave the trees alone and search for less protected fruit. That’s what we want
Application of the kaolin clayBut even more than that: because of the clay being white, the covered leaves are reflecting the sunlight and the heat pressure for our trees is reduces as well! And thanks to lower temperatures, the leaves can photosynthesise for many more hours during the day than under heat stress.
Studies point to even more advantages of applying kaolin clay to olive orchards, but I will leave it with this. Fingers crossed we will have a harvest without damaged olives!
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