Popillia japonica is a beetle that arrived in Italy only a few years ago, but it is spreading in an increasingly massive and uncontrolled manner, causing serious problems for agriculture and gardens.
It is an exotic insect, and just like the Asian bedbug and Drosophila suzukii, this Japanese beetle is capable of doing immense damage to many cultivated plant species. Popilia is in fact considered among the quarantine pests and the most affected regions are actively working to keep it under control.
The production of private gardens and orchards is certainly not spared, so it is important to know the insect and understand, at least as far as possible, the eco-friendly means with which it is possible to intervene to limit its damage.
Characteristics of the Japanese beetle
Popilia japonica is a beetle of Japanese origin, also present in the United States for some time and absent in Europe until 2014, with the exception of the Azores islands (Portugal). In the summer of that year, its first discovery took place in some municipalities of the Ticino Valley. Its spread therefore began in northern Italy, starting with Lombardy and Piedmont.
The adult of Popilia has an average length of about 1 centimeter and has metallic green color with bronze reflections on the back. What sets it apart from other similar insects, such as the common beetle (Phylloperta horticola) is the presence of 12 tufts of white hair (5 on each side of the abdomen and 2 wider on the terminal part).
Life cycle in Italy
The insect in northern Italy does one generation a year, with adults coming out of the ground between the end of May and the beginning of June. We can find it mainly in large groups to feed on plants and during the month of July there is the peak of its maximum presence.
Damage and species attacked by popillia
The Japanese beetle operates two types of damage:
- Larvae of Popillia Japonica they move in the ground and feed on the roots of plants.
- The adults of Popillia Japonica they are polyphagous and this is the big problem, as many cultivated species can be attacked.
Popillia attacks open field crops, ornamental trees and bushes and fruit plants and vegetables, for a total of about 300 species, and is therefore able to give problems both to the vegetable garden and to the garden.
The most serious damages are however borne by a limited group of species including peach, cherry, plum, apricot, stone, vine and blueberry among the fruit trees e green beans among the vegetables.
There are no doubts about its recognition as its presence in these cases is numerous on the leaves, which appear largely pierced or completely eaten.
How to combat popillia japonica
The fight against popillia is not left to the individual grower: coordinated actions are underway by the regional phytosanitary services of the affected areas, including through special traps.
Here is what can be done in summary to fight the Japanese beetle with biological methods, we will then go into detail point by point:
- Presence monitoring and reporting in case of sighting.
- Limit irrigation in the event of the presence of the insect, to damage the larvae in the summer.
- Harvesting manually, even with the help of hens.
- Use insect nets.
- Use neem oil as an insecticide.
- Introduce natural antagonists.
Traps for popillia japonica and monitoring
Insect monitoring is a fundamental practice and takes place at a regional level by the Phytosanitary Service.
In addition to the visual checks, special traps with specific attractants are used.
In particular, the phytosanitary services of Lombardy and Piedmont use two types of traps:
- The yellow and green jar with special wings suitable for capture.
- The tripod covered with insecticide-covered mesh.
Both types of traps work well, they have been approved by the Ministries of Health and Agriculture, but they can only be used by authorized personnel.
The flaw with these tools is that their attractive power is greater than their ability to capture, with the consequence that they attract many specimens even at a distance of hundreds of meters. The result is an increase in damage to the vegetation present in the vicinity of the trap itself. Furthermore, these traps assume that all citizens respect them and do not tamper with them.
What to do in case of sighting of Popillia Japonica
If we happen to spot specimens of Popillia it is important to report it. Here's what to do:
- Check that it is precisely this beetle (check for tufts of white hair on the sides of the abdomen)
- Photograph and eliminate insects immediately after doing it.
- Make a note of the affected plants.
- Make a report to the regional phytosanitary services (for example for the Lombardy region: [email protected] for the Ticino park: [email protected]).
Beware of irrigation
The eggs and young larvae of the Popilia are very sensitive to dehydration and the hot and dry summers are a brake on their development.
Consequently it is worthwhile limit irrigation to what is necessary, avoiding to moisten the soil too much, which instead favors the development of eggs.
Help from hens and manual harvesting
Who has hens or chickens he can turn to them for help in the defense of Popilila: it seems that the poultry are greedy. In this case, all you have to do is collect all the specimens that are on the plants and take them to the chicken coop.
Regardless of whether or not there are hens or chickens, manual harvesting is a practice of great positive impact on the containment of this insect.
Even if it requires perseverance and a little time, at least at the level of a vegetable garden or private garden, it can therefore be practiced with good results.
A really effective means of controlling this dreaded pest is the use of insect nets, to cover the rows or individual plants to be treated, after the fruit set.
It can be a bit challenging and burdensome, but it is a valid mechanical obstacle to the Popillia, as well as the Asian bedbug and other harmful insects, and it is also totally eco-friendly, making it suitable for organic farming.
Biological insecticide treatments
Against Popilia japonica it is possible to do treatments based on Azadirachtin (neem oil) as also recommended by the Ticino Park Authority, for an insect repellent action.
Products based on natural pyrethrum are not fully registered against Popilia, but if you use this product against other harmful insects, it is possible at the same time to see results against Popilia. For non-professional use, there are no problems in use and a license is not required, but the rule is always to read the product label carefully and respect all the instructions.
Antagonistic organisms for biological defense
The Japanese beetle in Italy is having an uncontrolled spread because it does not find sufficient antagonists in nature. As an external element to our ecosystem, it has no particularly effective pathogens or predators. To counteract it with natural methods, it was therefore decided to insert natural antagonists of this species.
The natural limiters of Popillia are essentially the entomopathogenic nematode Heterorabditis bacteriophora and the entomopathogenic fungus Metarizhium anisopliae, which have been introduced into the environment specifically since 2016.
In the space of a few years, the effect should be visible and the damages of Popillia Japonica it is hoped that they will be more limited, like the other native parasites or in any case set in our country for some time now.