The European Tarnished Plant Bug Lygus rugulipennis Poppius (Rhynchota Miridae) is the most common pest within this family in Italy. This polyphagous bug is reported to attack more than 400 species of plants and is a dangerous pest to numerous vegetables, such as eggplant, strawberries and lettuce. On lettuce, especially var. Romana, L. rugulipennis is particularly harmful in August and September. At that time of year, adults may be found between leaves of the maturing crop and their feeding provokes necrotic stripes on the leaves that cause aesthetic damage to the crop. Because of its high polyphagy, great mobility, high population densities and because of the low damage threshold in this crop, biocontrol is generally difficult. Therefore, the current control of L. rugulipennis relies on the application of insecticides, especially pyrethroids (Ferrari et al., 2002). The use of this broad spectrum insecticide has a negative impact on the conservative biological control of another economic pest of lettuce: Liriomyza huidobrensis (Blanchard) (Diptera Agromyzidae). Indeed, if pyrethroids are not used, this pest is normally kept under the economic threshold by several natural parasitoid species belonging to Hymenoptera, (Burgio et al., 2000). Moreover, in greenhouses, biological control of this pest could be achieved with the seasonal inoculative release of Diphlyus isaea (Walker) (Hymenoptera Eulophidae) and Dacnusa sibirica Telenga (Hymenoptera Braconidae). The release of these parasitoids is not effective if the control of L. rugulipennis relies in chemicals.

Trap cropping is an agroecological approach in the management of many pests, including herbivorous Miridis. In own research in Cesena (Northern Italy) this technique has been carried out with success for the management of L. rugulipennis on lettuce. The principle of this strategy relies on the fact that Mirids, even if they have high polyphagy, show a distinct preference to certain plant species. To exploit this behavior, a host preferred plant species is planted adjacent to the target crop, to keep the pests out. The trap crops, to be effective, have to be more attractive to the pest than the main crop. This is achieved by the use of a more preferred plant and, ideally, when it is at the most attractive stage for the pest. The success of trap crops could be improved through various manipulations, including the use of sex or aggregation pheromones or insecticides. In the case of insecticides used, the pests are attracted to a small area (trap crop) where the management is easier. In this way the chemically treated area is notably reduced; moreover, the insecticide is not sprayed on the crop, resulting in a decrease level of environmental impact.
On contrary using chemicals on the trap crops causes the loss of numerous beneficials. Indeed alfalfa is an optimum habitat also for those beneficial insects. In order to avoid this problem and to keep the population of L. rugulipennis under the economic threshold different experiments are carrying out. In particular, the release of L. rugulipennis eggs parasitoids, only in the trap crops, instead of chemicals, should be the technique more effective. The parasitoids should be able to reduce the number of L. rugulipennis and the use of insecticides could be avoided preserving the whole beneficial entomophauna.

The use of trap crops can drastically reduce the quantity of pyrethroids sprayed in the environment. This broad spectrum insecticide is used only in a small area and not on the crop.

The reduction of the use of insecticides enhances beneficial insects in the agroecosystem. It allows the natural control of other important pests of lettuce such as Liriomyza huidobrensis.

By not applying insecticides directly on the target crop, there is a reduction in the amount of insecticides used, which greatly benefits human and environmental health.

 
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Lygus rugulipennis

Damage caused by Lygus rugulipennis