Growth Regulators (PGRs) - Timing Critical Trees
Plant growth regulators (PGRs) can be very effective tools in apples for several
different uses. Here are some of the PGRs used through the spring season:
- Promalin or Perlan (contains benzyladenine
and gibberellins) are used to improve the shape of Red Delicious apples through
elongation of the fruit and development of more prominent calyx lobes.
(contains prohexadione-calcium) reduces terminal shoot growth by inhibiting the
synthesis of gibberellins, which cause cell elongation. Treated trees have the
same number of shoots, but they are thicker with shorter internodes.
Apogee can also reduce fire blight infections, not by affecting the bacteria,
but by reducing growth and infection sites.
(contains NAD (naphthaleneacetamide)) is a hormone-type thinner used at petal
fall. Absorbed by foliage where it induces formation of the abscission layer between
the spur and the fruitlet.
- Maxcel or Cilis Plus
(contains 6-benzyladenine (or 6-BA)) is used for both fruit thinning
and improving fruit size. Applications shortly after flowering will increase fruit
cell division, early in fruit development, and increase potential fruit size.
Higher rates will also cause fruit thinning.
- NAA or Fruitone-N
(contains naphthaleneacetic acid) is a hormone-type thinner used up to 12 days
after petal fall. NAA affects auxin activity, and interferes with photosynthesis
and proper fruit development. Affected fruitlets usually drop within 10-14 days
(contains carbaryl) is an insecticide that also thins fruit after petal fall.
The presence of carbaryl in the vascular system of the fruitlet interferes with
biochemical processes. Certain important fruit growth processes cease and the
It is very important to apply plant growth regulators
at the correct time, according to the stage of development of your trees. Note
that this timing can vary by days or hours, depending on your orchard location
and by cultivar.
Here is the upcoming spring "schedule" in the
- Full bloom: Promalin or Perlan for fruit
- Late bloom (shoots @ 2.5-5 cm): Apogee, first
- King bloom petal fall: Amid-thin
mm fruit: thinning with Maxcel or Cilis Plus, NAA or Fruitone-N, Sevin
days after 1st Apogee spray: 2nd Apogee application, if needed
days after bloom: final timing for Sevin, if needed
days after 1st Apogee: 3rd Apogee, if needed
- 42-49 days
after 1st Apogee: 4th Apogee, if needed
ReTain and Ethrel
are PGRs that are useful in harvest management and applied in late summer.
For more information:
Toll Free: 1-877-424-1300