Stone fruit trees should therefor be fully irrigated during these periods. Nut growth is generally less sensitive to tress than tree fruit growth. However, other nut crop yield factors, such as full split in almonds, shell splitting in pistachios, and kernel sunburn in walnuts are affected by water deficits. Stress does not affect the case of harvest of mechanically shaken tree fruit, but may reduce the harvestability of nut crops, especially pistachios. The rule of thumb is that as long as the trees do not defoliate, the stress can be tolerated with little impact on production in the following years.
Notable exceptions are almonds and apricots, as noted below.
Drought Strategies for Specific Fruit and Nut Tree Specialist Peach, Nectarine, Plum . Early season varieties should receive full irrigation through harvest. Apple, Pear . They then require full irrigation to achieve near-normal fruit size. Research in Washington state indicates that a 15 percent reduction in apple growth early in the season because of water deficits is followed by accelerated fruit growth after full irrigation is reintroduced, resulting in normal size fruit at harvest.