California Ag Network

Tag: Spider Mites

  • How to Protect Your Almonds from Navel Orangeworm and Other Pests

    With spring weather arriving earlier, almond growers in California can expect an earlier influx of pests in their orchards — and to get started sooner on preventing them from harming their nut crops. According to UCCE Sacramento Valley Integrated Pest Management Supervisor Sudan Gyawaly, now is the time to watch out for things like navel orangeworm (NOW), peach twig borers, leaf-footed bugs and spider mites.

    Navel Orangeworm (NOW)

    Navel orangeworms (Amyelois transitella) are the most prominent pests in almond orchards. These moths lay their eggs on the shells after hull split, and the larvae burrow inside the shell, eating the nuts and sheltering inside. Signs of a NOW infestation in an orchard include:

    ·      Small, flat, oval-shaped eggs outside of almond hulls

    ·      Pinhole-sized holes in almond hulls

    ·      Hulls that are oily in appearance

    ·      Fungal infections of nuts

    ·      Extensive webbing inside the hulls

    ·      Partially eaten nuts

    ·      Larvae that are white to pink in color, with crescent marks behind the head

    Navel orangeworm damage to an almond. Photo by Matthew Malcolm

    To manage NOW in your orchards, be sure to continuously monitor male flight activity by using pheromone traps. Also continue to monitor NOW egg traps to establish a spring biofix (the first spring flight, which acts as the starting date for calculating growing degree days), to help you predict the timing of their later flights. The first flight usually occurs from late March through April, but earlier times are possible, depending on the weather.

    According to UC IPM, prevention is key to avoiding infestation. This includes removing all mummy nuts by the start of February. To eliminate existing NOW populations:

    ·      Establish a biofix

    ·      Hang pheromone dispensers in the trees to disrupt mating

    ·      Assess trap activity and begin spraying at hull split.  Apply pesticides at night and early morning for optimal results

    ·      Harvest and clean up as early as possible

    ·      Remove mummy nuts by March 15 of the next year.  Mow or disk mummies on the ground.

    Peach Twig Borer

    While less of a concern in mature orchards, peach twig borer — also a moth — can still be a menace for almond growers in younger fields by causing primary scaffold damage. Begin monitoring pheromone traps in April to establish a biofix and decide if a spray is necessary in May.  Consult with your pest control adviser if you are unsure.

    Leaf-Footed Bugs

    Stink bugs and leaf-footed bugs are especially troublesome after a warm winter. Leaf-footed bugs can be trickier to spot.  UC IPM lists the tell-tale signs of an infestation in your orchard as:

    ·      Gummy nuts — nuts with exudates on the outside of the hull — a signature warning

    ·      Nuts that have dropped prematurely

    ·      Black spots on kernels and wrinkled, misshapen nutmeat from adult feeding

    ·      Withered and aborted shells from bugs feeding on premature nuts

    Leaf-footed bug

    Stink bugs cause similar damage, but this is usually around May or June. Leaf-footed bug management can vary from orchard to orchard, depending on history and severity. Gyawaly advises basing spray decisions on this history plus on damage risk associated with seasonal conditions. Consult with your pest control adviser if you are unsure.

    Spider Mites

    Typically found in the lower parts of the canopy, spider mites may also come out earlier and in greater numbers with warmer weather. Their presence should be monitored once every two weeks.  For this pest, beneficial arthropods that prey on spider mites may be one of your orchard’s best friends. These species include:

    ·      Western predatory mites

    ·      Spider mite destroyers

    ·      Sixspotted thrips

    ·      Pirate bugs

    By monitoring and addressing mite and insect pests in the spring, the pest populations can be kept under control to ensure a large, high-quality almond harvest.

  • Spider Mite Management Methods

    Spider mites can be a difficult pest for date growers, especially with how high up in the trees the fruit is. However, new methods of spider mite management are being studied at UC Riverside, including the use of predatory mites. Entomology specialist Bodil Cass spoke with Matthew Malcolm from Malcolm Media Ag Publishing at the World Ag Expo to discuss their findings. Watch this quick video and read more in California Fruit & Vegetable Magazine.

    Please thank this video’s sponsor Simplot for their industry support.

  • Monitoring Spider Mites in Almond Orchards

    Almond growers are all too familiar with the challenges posed by pests in their orchards. Despite not being on the top of a grower’s concern list, spider mites can inflict serious damage to an almond orchard, and rather quickly if populations get out of control. However, effective monitoring and the use of beneficial insects can play a crucial role in managing these pests and ensuring a healthy almond harvest.

    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

    1. 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.
    2. 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.
    3. 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.
    4. 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.
    5. Consider Selective Miticides: If natural predators are not enough, consider using selective miticides that are less harmful to beneficial insects.
    6. 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. — By the Almond Board of California