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Plum

Why Is the Bloom Season Important in an IPM Program?

Bloom season, which extends from the green-tip stage to petal fall, is the best time to manage several plum pests. Since foliage is sparse at this time, you can get good spray coverage more easily than later in the season. You can avoid water quality problems associated with dormant-season sprays for peach twig borer by treating with low-toxicity insecticides at this time. Also, monitoring for many pests, including installation of pheromone traps, begins at bloom.

Time some actions based on an estimate of when a certain proportion of the flower buds are fully open. For example, 5% bloom and 10% bloom are estimates of when the first 5% or 10% of flower buds reach full bloom. For pest management, the term "full bloom" is the point at which the majority of flowers in the orchard are fully open; by this time, some will be past full bloom, while others will be at earlier stages. The proportion of flowers that are fully open when the orchard is at full bloom can vary substantially depending on winter chilling. In years with high chilling, as many as 80% of the blossoms may reach full bloom at the same time. In low chilling years, the proportion may be below 50%.

Bloom stages
Dormant bud stage of plum bloom.
Dormant bud
Bud swell stage of plum bloom.
Bud swell
Green tip stage of plum bloom.
Green tip
Popcorn stage of plum bloom.
Popcorn
Full bloom stage of plum bloom.
Full bloom
Petal fall stage of plum bloom.
Petal fall
Jacket stage of plum bloom.
Jacket
Jacket split stage of plum bloom.
Jacket split


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