A high-quality peach harvest requires proactive management, and spraying is a necessary component to control insects and diseases. The term “worms” typically refers to the larval stage of several different insect pests that bore into the fruit, shoots, or trunk of the tree. A successful spray program relies on timing applications precisely to interrupt the life cycle of these damaging insects. Understanding the annual schedule and the pest’s behavior is the foundation for protecting the fruit crop.
Identifying the Primary Peach Pests
The most common and destructive peach pests are the larvae of moths and beetles.
The Plum Curculio is a small, mottled brown snout beetle whose female adults create a characteristic crescent-shaped cut on the developing fruit to lay their eggs. The resulting legless, yellowish-white larvae tunnel inside the fruit, often causing small peaches to drop prematurely.
The Oriental Fruit Moth is a grayish-brown moth whose larvae bore into tender new shoots in the spring, causing them to wilt and die, a symptom known as “flagging.” Later generations of larvae bore into the fruit near the stem end, feeding around the pit and often leaving no visible external damage.
The Peach Tree Borer larvae target the trunk of the tree near the soil line. They feed on the inner bark, causing gum mixed with sawdust-like material (frass) to exude from the entry site. The control timing for this pest is unique because the application must target the trunk directly rather than the fruit or foliage.
Dormant Season Preventive Spraying
The first phase of the annual spray regimen occurs during the dormant season, in late winter or very early spring, before the buds begin to swell. This timing is intended to address overwintering pests and diseases before the tree’s active growth period begins.
Applying a horticultural dormant oil at this stage smothers the eggs and larvae of pests like mites, scale insects, and aphids that hide in bark crevices. Dormant oil is a preventative measure that works by physical contact, reducing the initial pest population. Apply the oil when temperatures are above freezing and not expected to drop below 35°F for 24 hours to prevent bark damage.
Timing the Critical Growing Season Applications
Effective control requires precise timing linked to the tree’s development, known as phenological stages, to target emerging pests.
The first application must occur at petal fall, when 90% of the flower petals have dropped from the tree. Spraying at this stage is crucial because it avoids harming pollinators and immediately targets the first wave of adult Plum Curculio beetles.
The second critical application happens at shuck-split, occurring about seven to ten days after petal fall, when the developing fruit sheds the dried flower remnants (the shuck). This stage is the primary window for controlling the Plum Curculio before female beetles lay eggs inside the newly exposed fruit. Failure to apply an insecticide at shuck-split often results in severe curculio damage.
Following these initial applications, a series of cover sprays is necessary to manage subsequent generations of Oriental Fruit Moth and other late-season pests. These sprays are typically applied every 7 to 14 days, using the shorter interval during heavy rain or high pest pressure. The final application must respect the Pre-Harvest Interval (PHI), which is the minimum number of days required between the last spray and harvest.
Peach Tree Borer Control
Control for the Peach Tree Borer is scheduled separately, generally beginning in mid-summer (around June or July) when the adult moths begin laying their eggs. The insecticide is applied directly to the lower trunk, from the scaffold limbs down to the ground. This targets newly hatched larvae as they attempt to bore into the bark. This localized treatment is repeated according to product instructions to maintain a protective barrier throughout the moth’s egg-laying period.
Selecting Effective Insecticides for Larval Control
The selection of an insecticide depends on the target pest and the desired approach, which can be conventional or organic.
Pyrethroids, such as permethrin or gamma-cyhalothrin, are common synthetic options that provide broad-spectrum control against Plum Curculio and Oriental Fruit Moth. These synthetic materials offer an extended period of protection, often lasting up to 14 days.
Organic options include Spinosad and Bacillus thuringiensis (Bt), which are derived from naturally occurring bacteria. Spinosad is effective against moth larvae like the Oriental Fruit Moth and Peach Twig Borer, but it provides shorter residual control, sometimes requiring application every seven days. Bt is specifically used for caterpillars, but its effectiveness against deep-boring pests like Plum Curculio is limited because the larvae must ingest the toxin from the surface of the fruit.
To prevent pests from developing resistance, alternate between different chemical classes throughout the season. All insecticides must be applied thoroughly to ensure good coverage, and the product label must always be consulted to confirm the target pest, the correct application rate, and the specific Pre-Harvest Interval.