Macrolophus pygmaeus predatory bug

New publication shows how Macrolophus pygmaeus can reduce whitefly damage in plants

In a new paper published in the Insects journal, VIRTIGATION partner University of Catania (UNICT) shows how the Macrolophus pygmaeus predatory bug, a natural enemy of the Bemisia tabaci whitefly, can reduce its damage on plants.

Current research on whitefly & Macrolophus pygmaeus

The Bemisia tabaci whitefly is a major threat to many crops worldwide, including tomatoes and cucurbits. It causes extensive damage to plants by directly piercing leaves, sucking sap and producing honeydew on which sooty molds develops. This plant pest also transmits devastating, emerging plant viruses such as the begomovirus ToLCNDV. As a result, the Bemisia tabaci causes significant yield and quality losses in crops, especially in those grown in greenhouses. 

Considering the need to reduce the application of harmful chemical pesticides while fighting these plant pests, integrated pest management (IPM) methods based on biological control are on the rise. One promising method in this regard is the use of natural enemies of plant pests to protect crops from damage. However, the impact of these natural enemies on plant performance, as well as their behaviour vis-à-vis plant pests, is not always well understood. By better understanding the relationships between plant pests, their natural enemies and the plants, the actors of the horticultural value chain aim to reduce pest infestations and their negative effects in an ecologically safe and effective manner.

The Macrolophus pygmaeus, a predatory bug in the family Miridae, is one of the main natural enemies of the Bemisia tabaci whitefly. It is already widely used for its control. However, it can sometimes behave as a plant pest itself, causing damage to crops. So while it feeds on both insect prey and plant tissue, its overall effect on plant performance is not yet well understood. A previous study by Spanish researchers in 2018 in tomato crops found that Macrolophus pygmaeus acted as an efficient biocontrol agent of key pests in tomatoes, but also fed on the tomatoes’ reproductive organs, thereby reducing yield.

Macrolophus pygmaeus’s nymph
Macrolophus pygmaeus’s nymph © 2023 Farina et al., UNICT
Macrolophus pygmaeus's adult © 2023 Farina et al., UNICT

Experimental study of impact on potted eggplants

In order to bridge the current knowledge gap on the interactions between the Macrolophus pygmaeus, whiteflies and plants, entomologists from VIRTIGATION partner UNICT conducted a study on the impact of this predatory bug on the morphological and physiological traits of potted eggplants in the presence of the Bemisia tabaci whitefly. The scientists first collected a colony of Bemisia tabaci from an eggplant crop grown under greenhouse conditions in southeast Sicily. They then transferred the specimens onto potted eggplant plants in the laboratory under controlled environmental conditions. Macrolophus pygmaeus came from commercial sources and were maintained in the laboratory under the same conditions.

In their experiment, UNICT researchers assessed the impact of the Bemisia tabaci and Macrolophus pygmaeus on 36 potted eggplant plants with 6 fully expanded leaves. Their trial involved a completely randomized design with 12 replicates, under which each of the following three evaluated conditions were assessed: noninfested control plants; plants infested by Bemisia tabaci (PIB); and plants infested by Bemisia tabaci where Macrolophus pygmaeus was also released. The UNICT entomologists then analysed the response of the potted eggplant plants to these three conditions. 

Macrolophus pygmaeus helps plants against whiteflies

The outcome of UNICT experiments showed no statistical differences between the heights of plants infested by the Bemisia tabaci whitefly or by both insects, compared with noninfested control plants. However, indirect chlorophyll content, photosynthetic performance, leaf area, and shoot dry weight were all greatly reduced in plants infested only by Bemisia tabaci, compared with those infested by both pest and the Macrolophus pygmaeus predator, or with noninfested control plants. Contrarily, root area and dry weight values were more reduced in plants exposed to both of the insect species, compared with those infested only by the whitefly or compared with noninfested control plants, where the latter showed the highest values.

These results by UNICT researchers show how the Macrolophus pygmaeus predatory bug can significantly reduce the negative effects of Bemisia tabaci whitefly infestation, thus limiting the damage it causes to host plants through the example of potted eggplants. However, the effect of this bug on the underground parts of the eggplant still remains unclear and requires further research.

The UNICT findings help better understand the role that Macrolophus pygmaeus plays in plant growth, as well as for the development of IPM strategies to successfully control infestations by the Bemisia tabaci whitefly in crops, especially in those grown in greenhouses. They also help to clarify the relationships between plant, plant pest and their natural enemies, thus potentially enabling the prediction of plant development in the presence of both the plant pest and its predator. 

More info about VIRTIGATION partner UNICT's research

The full version of UNICT’s scientific publication in the Insects journal titled “Can Macrolophus pygmaeus (Hemiptera: Miridae) Mitigate the Damage Caused to Plants by Bemisia tabaci (Hemiptera: Aleyrodidae)?” is available online here since 8 February 2023. The dataset underlying UNICT’s peer-reviewed, open access publication is available in the VIRTIGATION Zenodo community. Find out more about VIRTIGATION’s scientific publications on our website here.