Pine gall midge

The pine gall midge (lat. Cecidomyia pini) belongs to the order Diptera and the family Cecidomyiidae. It is a tiny insect that, in its larval stage, leads a hidden lifestyle inside plant tissues.

Adult specimens resemble miniature mosquitoes with slender legs and transparent wings. Their life cycle is closely linked to the condition of coniferous plantations during a specific growing season.

The main danger to the tree comes from the larvae, which develop inside the pine needles, forming specific swellings called galls. These structures provide the pest with protection and nutrition for an extended period.

Visually identifying the adult insects is extremely difficult due to their small size and short lifespan in the adult stage. Therefore, diagnosis is based on identifying structural changes in the needles.

The pest's biology involves one or more generations per year, which directly depends on the region's climatic conditions and the quality of the food supply in forest nurseries.

The primary host is the Scots pine, as well as some other conifer species. The pest typically targets the weakest specimens or young plantations.

The larvae damage young needles by sucking sap from the tissues, which leads to a disruption of the normal photosynthesis process. Gradually, the needles begin to yellow and lose their functionality.

Mass reproduction of the pest can lead to a significant decrease in wood growth. In forest nursery conditions, this can cause a significant portion of seedlings to be rejected.

Damaged branches become more vulnerable to secondary infections, including fungal diseases that enter through the injured needle tissues.

Heavy infestation over several seasons can lead to partial crown drying and weakened immunity of the entire root system of the tree.

Adult insect activity begins during the period of mass regrowth of young needles, which usually occurs in May or early June. During this time, eggs are laid on the surface of the needles.

Larvae appear shortly after and begin the process of penetrating the needle tissue, provoking the appearance of galls. Active feeding continues throughout the summer.

By the end of summer and autumn, the larvae complete their development. They overwinter in various phases, depending on regional climatic features, often remaining in the galls on the branches.

The emergence of the next generation of adults is closely linked to the soil and air temperature. The spring warming acts as a signal for pupation and subsequent emergence of the midges.

Monitoring for the pest should be conducted during the active needle growth phase, as this is the best time to notice the initial stages of damage on the tree.

The main sign of infestation is the characteristic swellings or thickenings on the needles, known as galls. These are clearly visible during a thorough inspection of the branches.

Gradually, the damaged needles change their natural green color to yellowish or brown. In severe cases, mass yellowing and premature needle shedding are observed.

Dissecting a gall reveals the larvae, which have a characteristic shape and color. This is the primary method for confirming the presence of this specific midge species.

The crown of the tree takes on a "thinned" appearance due to the uneven distribution of damaged needles along the branches. This is noticeable even with a small increase in the pest population.

• Yellowing of needles in the spring-summer period.
• Presence of knot-like thickenings on individual needles.
• Needle shedding earlier than the normal season.
• Stunted shoot growth in young trees.

An effective protection method is the use of systemic insecticides, which penetrate the plant tissues and affect the concealed larvae.

An important agronomic practice is the timely pruning and destruction of infested branches where galls are located. This significantly reduces the population for the following year.

It is necessary to maintain high standards of nursery management, providing trees with optimal growth conditions and immunity, making them less attractive to gall midges.

Monitoring using pheromone or sticky color traps is recommended to determine the exact timing for insecticide applications in the spring.

In natural conditions, the population of the pine gall midge is controlled by entomophages, so it is advisable to avoid excessive use of broad-spectrum pesticides when planning control measures.