The red bug is an insect belonging to the large family of Pentatomids. The species in question is scientifically named Eurydema ventralis. Its study is alongside that of more well-known species, namely the green bug (Nezara viridula), the Asian bug (Halyomorpha halys), and the bed bug (Cimex lectularius). Although being less harmful than the others, the red bug can also cause serious damage to crops. This is even more true if not properly controlled.
Let’s better understand this insect and its behavior. We’ll see which crops are affected by its activity, the damages it causes, and strategies for the plants’ biological defense.
The Red Bugs
Eurydema ventralis
Eurydema ventralis is an insect that reaches about 10 mm in size as an adult. It’s easily recognizable due to its red color marked with several regular-shaped black spots. This gives rise to its common name. However, some specimens of related species can be yellow or orange in color. The body is flattened, with a rounded head and small, narrow cheeks. The dark spots concentrate on the elytra and scutellum, forming a distinctive pattern. The larvae are initially dark, almost black, and then assume the final color as they molt.
The biological cycle of the red bug unfolds as follows. With the onset of early autumn cold, the adults overwinter in winter shelters, consisting of plant debris or small crevices. From the beginning of the month of April, they emerge from their shelters and resume their trophic activity on plants. They prefer to target the remains of cauliflowers or other brassicaceae that are ready to flower (siliques). After a while, the mating phase begins, after which the females start laying eggs in small groups under the lower side of the leaves. The eggs have an embryonic development that lasts about 15 days. Around mid-May, the nymphs hatch, reaching full maturity in June (first generation of adults).
The nymph molts 4 or 5 times, becoming an adult in about 6 weeks.
The cycle repeats similarly in the summer months, with the appearance of second generation adults in August. These specimens, as mentioned, will overwinter with the arrival of the first cold weather. Thus, the red bug completes two generations per year.
Plants damaged by the red bug
As mentioned, the species Eurydema ventralis is known as the cabbage bug. From this, it’s easy to understand that cauliflowers and other brassicaceae like broccoli, savoy cabbage, etc, are the crops on which this bug feeds.
Less frequent are attacks on other plants such as Gramineae or potatoes. On the other hand, tomatoes and other Solanaceae are safe from this insect.
The red bug feeds on the sap of leaves and young shoots, causing rapid deterioration. The feeding punctures create areas with reduced chlorophyll, which dry up quickly, leaving only the green leaf veins. If the plants have been transplanted recently and are in the early stages of development, the attack can be fatal. The resulting damage includes wilting, leaf necrosis, and ultimately the death of the crop.
In the spring months, when the red bug emerges from its shelters, its attack on siliques can lead to the abortion of seeds.
Agronomic Defense
To limit the damage of the red bug, a good agronomic practice is proper crop rotation. If there have been cabbage bug attacks in a season, the next planting should avoid cultivating the plant in the same soil.
Without this precaution, we inadvertently assist in the development and proliferation of the bug.
Another useful agronomic technique is the application of natural mulch. During the day, this bug remains in the upper layers of the soil, but in the cool evening hours, it climbs onto the plant to feed.
Mulching mechanically limits this type of activity.
Biological Remedies
Defending against the bug with good agronomic practices leads us to discuss how to eliminate cabbage bugs with biological remedies. The first and most immediate one is manual removal.
The bugs tend to cluster and attack plant leaves in the evening hours. Therefore, shaking the plant and manually collecting adult specimens is easy.
Once collected in a bucket, they can be eliminated by drowning them in water and soap.
If we have an ongoing cultivation, it’s good to frequently monitor the plants. This way, we will collect as many bugs as possible and prevent them from causing damage.
Another bio remedy is the use of natural macerates. This bug species, compared to others, is more sensitive to the action of natural preparations. Thus, these can be used to repel them from crops. Nettle macerates, garlic macerates, and macerates of tomato leaves and female flowers are excellent remedies against the red bug.
The last type of biological defense targets young specimens and can be carried out in two ways. If their presence is limited, we recommend using water and Marseille soap. If the population is quite large, it’s advisable to use azadirachtin, the active ingredient from the neem tree. However, we reiterate that these remedies are effective on young specimens, not on adults with a strong exoskeleton.
Further Reading
- Ukrainian Journal of Ecology, 2021: “Harmfulness of cruciferous bugs” – This article discusses the harmfulness of various cruciferous bugs, including Eurydema ventralis, and their impact on crops.
- Scientific Reports, 2023: “Field attraction of Eurydema ornata (Hemiptera: Pentatomidae) to allyl isothiocyanate” – The study investigates the field attraction of Eurydema species, including Eurydema ventralis, to specific chemical compounds.
