The use of chromotropic traps is a very simple agronomic technique but also very effective. It has a double objective, first of all to monitor the presence of harmful insects inside the garden or orchard. Secondly, mass trapping. It becomes immediately clear how this particular prevention strategy can become an excellent ally for the biological care of the fields.
There are different colors available, depending on the insect to be targeted. The effectiveness of this system depends on several factors, the most relevant of which is the intensity of field placement.
We understand, therefore, in this article, how these traps work, how many variations there are and how to place them. Finally, let’s see how to set them, without too much difficulty.
What are chromotropic traps?
In organic farming the use of chromotropic traps has been widespread and established for a long time. Very simply they are special sheets or panels, usually plasticised, on which a special adhesive is applied. The colored sheet attracts the harmful insect and the adhesive captures it, making it stick to the surface of the panel itself.
The objective of this type of trap is twofold:
The monitoring of harmful insects in the field. This is done through direct and periodic observation of the colored panel. Thanks to this ploy, we can realize which insects are present in our field, what stage of development they have, how much they are numerically present, and then what is the best way to intervene
The mass capture of insects. If the traps are used with a certain intensity in the field, i.e. putting many of them at a short distance, in addition to the important monitoring function, we will capture a very high number of insects. The obvious consequences will be: a reduction in their presence and a reduction in the damage caused to crops.
In general, this type of trap has a very low environmental impact, as long as the panels are disposed of ecologically.
It also avoids the introduction of toxic substances into the environment and the vegetation of the plants we are going to protect. The adhesives used, in fact, are specially designed for agriculture and are designed so as not to dissolve with the sun and not to drain on the ground.
They do not affect the use of other products allowed in organic farming, such as natural macerates (nettle, garlic, horsetail, fern), bacillus thuringiensis, Marseille soap, neem oil. On the contrary, using chromotropic traps together with other organic remedies increases the effectiveness of both in a synergistic way.
The colors of chromotropic traps
In nature it is easy to observe how insects are more or less attracted to some shades of color than others.
Field experiments have shown that the best colors for chromotropic traps are yellow and blue.
Yellow traps attract most of the harmful insects that threaten crops, in particular:
- The white fly;
- The oil fly;
- La tuta absoluta del pomodoro;
- The cherry fly;
- Flies in general;
- The buzzers;
- Foliar miners;
- Some species of cochineal.
The bugs in the neanid stadiums
Blue chromotropic traps, on the other hand, are mainly used for monitoring and mass capture of thrips. In particular, it attracts the harmful thrips Frankiniella Occidentalis, insect vector of the terrible tomato virosis
At the following link you can find effective chromotropic traps, offered at an affordable price. They are already ready to use, with directions for use and specifications for the particular insects we are going to capture.
Pheromones for insects
To improve the effectiveness of chromotropic traps, especially when intensive cultivation is practised, a synthetic pheromone is added.
In simple terms, it is a particular odorous substance, naturally emitted by insects in nature, to attract individuals of the opposite sex. Usually, it is the female specimen emitting the pheromone. This is then synthesized and reproduced in order to simulate this signal and attract more individuals into traps.
Usually, the pheromones are utilized in special traps, but, as said before, they are often added to the colored trap.
A series of pheromones and traps with this specific function can be found here.
The placement of chromotropic traps
Let us now see how and with what intensity to place the chromotropic traps in the garden, for the functions we have just described.
Yellow traps and blue traps
Let’s start with the yellow chromotropic traps. In the open field, in the vegetable garden or in the domestic garden, if you want to proceed only to the monitoring, you have to respect the following distances: 6 traps per hectare for the cultivation of olive trees and orchards, 4 traps per hectare for the vineyard, 2 traps every 100 square meters for the vegetable gardens.
For the massive capture, however, you must have 1 to 4 traps per plant for olive trees and orchards, this depending on the size of the land and the degree of infestation detected. For the capture of mass in vegetable crops, the intensity increases to 2 traps every 10 square meters.
It should be noted that the traps are harmless for bees. Unlike what you might think, in fact, the simple yellow color does not attract them. To attract them, instead, it is necessary the presence of pollen and nectar that bees can recognize very well.
In the vegetables cultivated in greenhouse, the indications are to be increased of the 25-30%, as the presence of harmful insects is more massive.
The traps are to be placed always close to the vegetative apices and raised accordingly as the plant grows.
For this purpose you can use hanging wires, wooden poles or bamboo canes such as those found here.
The blue chromotropic traps are for thrips control.
For monitoring, they should be set at a ratio of 10-12 per 100 square meters in the pre-flowering phase. Afterwards, it is necessary to check if the thrips population has a tendency to increase. If so, additional traps should be set according to the degree of infestation.
Also in this case, the traps must be set at the height of the highest flower boxes or shoots.
This time, too, of course, the traps should be raised progressively in line with the growth of the plants.
The handmade chromotropic traps
If you want to make your own chromotropic traps, just use simple coloured plastic plates. These will need to be passed through with transparent glue, like the glue generally used for paper.
The advantage of do-it-yourself is certainly represented by the economic savings, however there is the big unknown of the instability of the glue used. If used in excess or if exposed to high temperatures, in fact, this can dissolve and leak easily into the soil, introducing harmful substances.