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Why Is the Fruit Development Period Important in an IPM Program?

The fruit development period is important for ensuring that controls applied during the dormant and bloom seasons were effective. Pests that are especially important during the fruit development period are oriental fruit moth, peach twig borer, mites, western flower thrips, omnivorous leafroller, adult katydids, fruit rot, rust, and powdery mildew.

Rust, powdery mildew, scab, and mites aren’t present every year, so it is important to monitor for them to detect a problem as soon as it appears. Catching a pest problem early increases the possibility that it can be controlled with “soft” insecticides (such as oil for mites or sulfur for rust), thus avoiding the conventional insecticides and miticides (organophosphates or pyrethroids) that destroy beneficial insects and mites and can impair water quality.

Nectarine fruit go through three developmental stages:

  • The first begins after pollination and fertilization and is a period of rapid growth that lasts about 30 days. By the end of this stage, nearly all the cells of the fruit have been formed and the pit begins to harden.
  • Pit hardening marks the beginning of the second stage, during which fruit size increases more slowly.
  • The final stage, which usually begins 4 to 6 weeks before harvest, is a period of rapid growth of the skin (exocarp) and flesh (mesocarp) of the fruit.

Fruit and flower drop may occur at any time during the season in response to environmental or physiological conditions. Many flowers and fruitlets may drop shortly after bloom if their ovules were not fertilized. Sometimes a drop of young fruit, often called “June drop,” occurs in April or May. This is a normal process that is probably the result of competition among fruit for nutrients.

Statewide IPM Program, Agriculture and Natural Resources, University of California
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Agriculture and Natural Resources, University of California

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