Timing of Hull-Split Spray - IGRs v/s Pyrethroids

There have been a few questions about the timing of hull-split sprays with the various products available. Our suggested timing for the spray depends on the product planned to be used.Insect growth regulators (IGR) (i.e. Intrepid, Success, Altacor, Belt, etc) should be applied at the onset of hull-split - just as the suture becomes defined and the nut pops open when force is applied. This is about the same time that the blanks begin to split in the tops of the trees on the outside rows. This timing is in contrast to the application of pyrethroids. These products (i.e. Asana, Pounce, Warrior, etc.) should be applied later than an IGR, around 2-5% hull split.The timing difference is due to the differences in activity and persistence of the products. IGRs tend to be more effective in controlling eggs, neonatal and developing larvae, while pyrethroids do a better job in knocking down adults moth populations. The activity of the IGRs also tends to persist longer in the field. Since the IGR has longer persistence and tends to target the developing larvae, it has to be present on the almond surface before the egg hatches/larvae continues to develop.Since these sprays are going out earlier than in the past, bracket sprays may be needed within areas with high NOW pressure. This is an important consideration if dealing with later harvesting varieties which will be exposed to the later flights of NOW.