Bugging Fruit Trees: Ambrosia Beetle Invasion!

Fruit trees provide us with a bountiful harvest and a source of joy in our gardens. However, lurking within the bark is a tiny pest known as the ambrosia beetle. While it may be small (2-3 mm), the ambrosia beetle can significantly affect fruit trees, leaving growers concerned about their impact.

The ambrosia beetle (Xylosandrus crassiusculus) belongs to a group of small beetles in the family Curculionidae, attracted to the scent of trees and sap to attack both healthy and injured or stressed trees and shrubs. These insects have a unique symbiotic relationship with a fungus known as the ambrosia fungus. When a female ambrosia beetle finds a suitable host tree, it burrows into the bark and creates tunnels called galleries. As it tunnels, the beetle introduces spores of the ambrosia fungus, which grow and serve as a source of food for the beetle.

Ambrosia beetle (Xylosandrus crassiusculus) kills landscape and fruit trees. The tunneling activity of these insects disrupts the tree’s vascular system, impairing nutrient uptake and water flow. This can lead to reduced tree health, stunted growth, and weakened immune responses against other pests and diseases. Because of the damaged health, we can also say that the tunneling influences fruit quality and yield. In fact, this activity can create entry points for pathogens, resulting in fruit rot or blemishes. Additionally, stressed trees may produce smaller or malformed fruits with lower quality and reduced yield. Finally, ambrosia beetles are the perfect individuals to carry and transmit diseases. Some of these diseases, such as Fusarium dieback or laurel wilt, can devastate fruit trees, lead to tree decline, or even death.

Controlling ambrosia beetles and reducing their threats on fruit trees require a comprehensive approach:

Monitoring plays a crucial role in early detection. Regularly monitoring tree health, carefully examining signs of infestation such as entry points, and observing beetle activity can help identify the presence of ambrosia beetles at the earliest stages. This enables timely intervention and prevents the infestation from spreading. Ambrosia beetle (Xylosandrus crassiusculus) can be trapped using an ethyl alcohol bait trap.

Cultural practices are essential for promoting tree vigor and resilience. By implementing proper irrigation techniques, appropriate fertilization, and regular pruning, growers can enhance the tree’s overall health and fortify its natural defenses. Healthy and robust trees are better equipped to withstand beetle attacks and are less prone to stress-related vulnerabilities.

In cases of severe infestations, targeted insecticide applications such as Pyrethroids may be necessary, to control adults and should be applied prior to the closing of the galleries with frass

Vantex:

• Active Ingredient: GAMMA CYHALOTHRIN 6%,
• Rate of Use : 70 ml/200L,

Decis Expert:

• Active Ingredient : DELTAMETHRIN 10 %
• Rate of Use : 50 ml/200L

However, it is crucial to exercise caution and adhere to recommended guidelines. Careful consideration should be given to the potential impact on beneficial insects and the environment to ensure sustainable pest management practices.

An example would be Entomopathogenic fungi (EPF) like Beauveria bassiana,  Metarhizium brunneum, or Isaria fumosorosea . These fungi have been used in biocontrol, which has mostly targeted insects. To simultaneously overcome the Ambrosia beetle (Xylosandrus crassiusculus) and its fungal symbionts, current investigations have combined EPF with mycoparasitic fungi such as Trichoderma spp.

Reference: Spore Acquisition and Survival of Ambrosia Beetles Associated with the Laurel Wilt Pathogen in Avocados after Exposure to Entomopathogenic Fungi – PMC (nih.gov)

The tiny ambrosia beetle may be inconspicuous, but its impact on fruit trees, should not be underestimated. By understanding their behavior, effects on tree health, fruit quality, and disease transmission, growers can develop effective management strategies to minimize the damage caused by these pests. Vigilance, early detection, and a holistic approach to pest management are key to protecting our cherished fruit trees from the clutches of the ambrosia beetle.