Understanding Spider Mites
Spider mites are tiny arachnids that thrive in warm, dry conditions, making almond orchards an ideal habitat. These pests feed on the leaves of almond trees, causing stippling, yellowing, and eventually leaf drop. Severe infestations can lead to reduced photosynthesis, weakened trees, and lower yields. Therefore, it is essential to keep a close eye on spider mite populations and take timely action to prevent economic losses.
The Role of Beneficial Insects
One of the most effective natural treatments for spider mites is the use of beneficial insects, such as six-spotted thrips. These tiny predators feed on spider mites and can significantly reduce their populations. David Haviland, a University of California Cooperative Extension (UCCE) entomology farm advisor, emphasizes the importance of relying on six-spotted thrips for mite management. These thrips are highly adaptable, reproduce quickly, and provide numerous operational benefits. They occur naturally, are free, and do not leave residues, pre-harvest intervals, or worker safety issues to worry about.
In addition to six-spotted thrips, other natural enemies of spider mites include predatory mites and lady beetles. These beneficial insects can help maintain a balance in the orchard ecosystem, reducing the need for chemical interventions. However, it is crucial to monitor the populations of both spider mites and their natural enemies to make informed decisions about pest management.
Effective Monitoring Techniques
Monitoring for spider mites involves regular inspections of the orchard, particularly in dusty or water-stressed areas where mites are most likely to thrive. Checking on the underside of leaves for the presence of spider mites is the most effective way to identify them in the orchard. According to the University of California Agriculture and Natural Resources (UC ANR) Integrated Pest Management (IPM) Program, growers should check for spider mites at least weekly during the warmer months. Presence-absence leaf sampling is a useful tool for determining whether treatment is necessary. If there are 1.4 mites per leaf or 38% of leaves are infested, it is time to consider intervention to prevent the population from reaching damaging levels.
To-Do List for Growers
- Seasonal Monitoring: From March to early May, monitor orchards for both predators and spider mites at least once every two weeks. Increase monitoring frequency to at least once a week from June to September when mite populations can rapidly increase.
- Weekly Inspections: Regularly inspect your orchard, especially in dusty or water-stressed areas, to check for spider mites. Use a hand lens to detect mite eggs, hatched spider mites, and predators.
- Presence-Absence Leaf Sampling: Use this method to determine if treatment is necessary. If there are 1.4 mites per leaf or 38% of leaves are infested, take action.
- Monitor Beneficial Insects: Assess the populations of natural enemies like six-spotted thrips, predatory mites, and lady beetles to ensure they are sufficient to control spider mites.
- Consider Selective Miticides: If natural predators are not enough, consider using selective miticides that are less harmful to beneficial insects.
- Follow ABC Guidelines: Utilize resources and guidelines provided by the Almond Board of California (ABC) for effective mite management.
For more detailed information on monitoring spider mites, growers can refer to the guidelines provided by the UC ANR IPM Program here.
Spider mites could pose a significant threat to almond orchards, but effective monitoring and the use of beneficial insects can help manage these pests without increasing inputs. By relying on natural predators like six-spotted thrips and other beneficial insects, growers can reduce the need for chemical interventions, lower costs and promote a healthier orchard ecosystem.
