Macrolophus pygmaeus is a species of predatory mirid bug, recognized for its beneficial role in agricultural and horticultural settings. Growers often introduce Macrolophus pygmaeus as part of an integrated pest management strategy, aiming to reduce reliance on chemical interventions. Its effectiveness stems from its predatory nature, offering a biological alternative to conventional pest control methods.
Identification and Lifecycle
Adult Macrolophus pygmaeus are slender insects, typically measuring between 2.9 to 3.6 millimeters in length, with females being slightly larger than males. Their bodies are predominantly green, featuring long legs and antennae. The forewings are transparent and soft green, with a small black spot, and they possess large, brown, hemispherical compound eyes.
The lifecycle begins when female bugs deposit their eggs into the plant tissue, usually within stems or leaf veins. After hatching, the nymphs emerge, appearing yellowish-green in their initial stages and becoming bright green as they mature. These nymphs undergo five developmental stages, or instars, before reaching adulthood, and they are also active predators.
Development from egg to adult is influenced by temperature, taking approximately 18 to 30 days under ideal conditions around 25°C to 30°C. At lower temperatures, such as 15°C, the developmental period can extend significantly to 58 days. Adult females can live for about 40 days at 25°C, laying between 100 to 250 eggs throughout their lifespan, depending on temperature and available food.
Role as a Biological Control Agent
Macrolophus pygmaeus functions as a generalist predator, actively searching for prey throughout crops. It employs piercing-sucking mouthparts to penetrate its prey and extract their bodily fluids. This voracious hunting behavior makes it a valuable asset in managing various agricultural pests.
The primary target for Macrolophus pygmaeus is whiteflies. It is highly effective against all life stages of these pests, consuming their eggs, nymphs, and even adults. Its consistent predation on whiteflies makes it a preferred biological control agent in many integrated pest management programs, particularly in tomato cultivation.
Beyond whiteflies, Macrolophus pygmaeus also preys on a range of other common greenhouse pests. These include spider mites, various aphid species, thrips, and the eggs of moths. While whiteflies are its preferred food, the bug’s ability to consume these secondary pests contributes to broader pest suppression.
Optimal Conditions for Establishment
The successful establishment of Macrolophus pygmaeus populations in a crop depends on environmental conditions. Optimal temperatures for its development and activity are between 20°C and 30°C. Lower temperatures can substantially slow down its development and population growth.
This predatory bug requires a significant amount of time, often several weeks, to establish a robust population after introduction. Preventative releases early in the crop cycle are often recommended to ensure a sufficient number of predators are present before pest populations become problematic. Early introduction allows the Macrolophus pygmaeus population to grow steadily, preparing it to combat emerging pest infestations.
Supplemental feeding is a common practice to support the establishment and population growth of Macrolophus pygmaeus, especially when pest densities are low. Sterile moth eggs are frequently used as a high-quality protein source. Providing this extra food ensures the bugs have a consistent nutritional supply, which is necessary for strong population development and female egg-laying, as plant sap alone is insufficient for full population growth.
Another strategy to aid establishment involves the use of “banker plants,” such as mullein (Verbascum thapsus) or even tobacco (Nicotiana tabacum). These plants can host the predator and sometimes alternative prey, providing a stable refuge and a continuous food source, thereby helping to sustain the Macrolophus pygmaeus population within or near the protected crop. This approach can enable the bug population to persist even between crop cycles.
Potential for Crop Feeding
Macrolophus pygmaeus is considered a zoophytophagous insect, meaning it can feed on both animal prey and plant material. This plant feeding, known as phytophagy, typically occurs when the availability of insect prey is very low or absent. The bug will consume plant sap to obtain moisture and nutrients, which helps it survive during periods of prey scarcity.
While generally considered minor, plant feeding can occasionally lead to visible damage, especially in sensitive crops like tomatoes and sweet peppers. In tomatoes, this may manifest as fruit deformations during setting or necrotic rings on stems. Damage to reproductive organs, such as flower drop or malformed fruit trusses, has been observed in some instances, potentially reducing yield. In gerbera, misshapen flowers can appear.
Maintaining a consistent, albeit low, level of pest prey or providing supplemental food sources, such as sterile moth eggs, can help mitigate significant plant damage. This practice ensures the Macrolophus pygmaeus population has sufficient animal protein, reducing its reliance on plant sap for survival and reproduction. By balancing prey availability with supplemental feeding, growers can encourage the bug’s predatory behavior while minimizing potential phytotoxic effects.