The protective barriers may be internal, as in the case of Orbit, or external, as with TPTH and other pecan fungicides. This is the period of most active leaf growth. A 14 to 21 day interval is suggested from pollination until shell hardening. This schedule will need adjustment depending on season, varieties, etc. For most older groves, bud break should be considered as the stage when green tissue is readily visible on the dominant variety.
Most growers modify the standard program to best fill their individual needs.
The fungicides commonly used to control scab and most other diseases do not control powdery mildew or zonate leafspot. These diseases occur occasionally and require special control measures. Regular scouting can aid a grower in knowing if and when these measures are needed. Pecan varieties vary greatly in their susceptibility to scab. Historically, the general trend has been for varieties regarded as scab resistant to become susceptible with the passage of time.