Almond seed wasp

The almond seed wasp, Eurytoma amygdali, is a hymenopteran insect belonging to the family Eurytomidae. Adult wasps are small, dark-colored, and typically reach a length of 4 to 6 mm.

The larvae are legless, white in color, and develop exclusively within the almond nut. This cryptic lifestyle makes early detection of an infestation very difficult for orchard owners.

Females possess a specialized ovipositor that allows them to pierce the soft shell of young almonds and lay eggs directly inside the developing kernel. This behavior is highly synchronized with the host plant's phenology.

The insect overwinters as a larva inside the mummified fruits that remain on the trees or fall to the ground. As spring arrives, the larva pupates and eventually emerges as an adult wasp to restart the cycle.

The life cycle is closely tied to the growth stages of the almond tree. Emergence of adults typically peaks during the fruit-set phase, when the shells are still tender enough for the female to penetrate.

The primary host for this pest is the almond tree (Prunus dulcis). The wasp causes severe economic damage by feeding on the kernel, effectively destroying the marketable product.

Although it primarily targets almonds, the pest can occasionally infest other stone fruits like peaches or plums. If left unmanaged, infestation rates in an almond orchard can quickly reach epidemic proportions.

Damaged fruits often drop prematurely from the tree. However, many infested nuts remain on the branches until the harvest, often appearing normal from the outside, which leads to hidden losses.

Beyond direct destruction of the seed, the pest's presence creates entry points for secondary pathogens, such as molds and fungi, which can spoil the quality of the remaining harvest.

The almond seed wasp is considered a significant quarantine pest in many regions. Trade of infested almonds is a primary pathway for the spread of this insect to new, previously uninfested areas.

The most reliable sign of an infestation is the presence of small, circular exit holes on the surface of the nuts. These holes are created by the adults as they emerge from the fruit.

Premature yellowing and fruit drop are common during the spring and early summer. When opened, these dropped nuts typically show a hollow interior or remnants of the kernel along with the larvae.

During the harvest, infested nuts may appear lighter in weight or have a slightly misshapen shell. Experienced growers can often distinguish them during the sorting process by checking for the exit holes.

Mummified fruits left hanging in the canopy throughout the winter are a hallmark of an infestation. These fruits serve as the primary source of the next season's population if they are not cleared.

General tree decline and reduced yield are long-term indicators of a recurring pest problem, often caused by failure to implement rigorous sanitation measures in previous years.

The cornerstone of control is orchard sanitation. Collecting and destroying all fallen and mummified nuts is essential to remove the overwintering population before the new generation emerges.

Deep cultivation of the soil under the tree canopy during the dormant season helps bury the pupae, preventing the adult wasps from successfully emerging and reaching the trees.

Chemical control involves targeting adult wasps with insecticides during their emergence period. Timing is critical, as sprays must be applied when the fruit is vulnerable to oviposition.

Biological control through the preservation of natural predators and parasitoids is recommended for integrated pest management programs to reduce the need for chemical interventions.

• Rigorous removal of mummified fruit.
• Deep plowing of soil under trees.
• Monitoring adult flight periods.
• Selective insecticide applications.