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Unfruitfulness Causes

Explanation of Categories of Unfruitfulness

Between budbreak and about bloom, as each new bud forms, it develops either a primordial bunch or tendril.  Lack of a bunch is called “failed inflorescence”.  This is usually related to low carbohydrates from causes such as low storage, cool temperatures, or overcast weather.  NPK balance may also contribute to inflorescence.  We rate these buds 0 for zero.

During a couple of months after bloom some of the new buds may die.  This “primary bud necrosis” (PBN) is presumably mediated by plant hormones and can be identified by an abscission layer where the primary bud tears away from its base.  Secondary buds usually survive and may have primordial fruit, usually small.  PBN is usually related to low carbohydrates from causes such as shading, crop overload, or excessive vegetative growth which can be caused by too much water or fertilizer.  Too much gibberellin may also lead to PBN.  PBN buds are rated B for burnt.

Throughout the year environmental conditions may kill or sicken buds.  We think the cause is usually pathogens.  We have informally classified about seven disease syndromes.  Two of these have been loosely associated with Eutypa and Botryosphaeria.  Frost or fire may also damage buds. Sick buds could possibly result from other stressful events such as extreme hot spells, lack of water, or heavy mite infestations.  If the damage is occurring when we inspect, the bud is rated S for sick.  If the damage is old, the bud is rated D for dead.

In some areas on some varieties bud mites may be present.  The level of damage varies.  If we observe any mites the bud is infested.  If the mites are on the bunch causing slight to moderate damage, we rate it damaged.  The bud is rated as fruitful.  These bunches may survive but have fewer berries than normal.  We report the number damaged as a percentage of total bunches.  If the mites damage all or most of the bunch, we rate it destroyed.  The vegetative portion of the bud may survive, but the bud is rated Dead. We report the number destroyed as a percentage of total bunches including those destroyed.  Sometimes the mites are so bad that the entire bud is killed and we cannot tell whether it ever had a bunch.  We rate these as M for mite-killed.

Sometimes a node has no bud.  Either none developed, or it fell off.  We rate this A for absent.

If we lose a bud during processing, or if a sample is cut so that a node is missing, we leave the entry blank, and it is not included in the analysis.