In this CRI Podcast episode, we speak with Dr. Jan vanNiekerk, CRI Soilborne Disease Researcher and Portfolio Manager for Disease Management Research, about the disease challenges citrus growers and packhousesface following severe flooding and prolonged wet conditions.
The discussion focuses on how saturated soils and waterlogged orchards create ideal conditions for Phytophthora root rot, one of the most serious soilborne disease threats in citrus production. Jan explains how flooding removes oxygen from the soil, causing root stress and root death, which in turn creates favourable conditions for disease development. Flooding also increases the risk of fruit decay, especially Phytophthora brown rot andsour rot, which can have serious implications for fruit intended for export.
The episode also explores the practical management decisions growers need to make after flooding events, including:
· improving orchard drainage and removing standing water
· strict orchard sanitation through removal of rotten fruit from trees and orchard floors
· careful handling of sensitive fruit from flooded and waterlogged orchards
· more frequent changing of sanitiser and fungicide baths in the pack house
· understanding the role and risks of phosphonate applications
· managing the increased risk of Phytophthora brown rot, sour rot and postharvest decay on flood-affected fruit
A key theme throughout the discussion is that fruit from stressed trees require more careful handling than under normal conditions. Even small handling injuries can increase the risk of postharvest disease development later in the supply chain. This is especially important where fruit mayalready have been exposed to floodwater, mud or high disease pressure before reaching the pack house.
The conversation also highlights the importance of patienceafter flooding events. Entering saturated orchards too early can cause additional damage, while long-term root disease management strategies remain critical well beyond the initial flooding period.
The key takeaway for growers and packhouses is clear: flooddamage is not only a short-term event - it creates long term risks of Phytophthora root rot development, as well as increased risk of fruit decay such as Phytophthora brown rot and sour rot, which must be carefully considered before fruit is packed and exported.
This podcast was recorded in May 2026.
CRI Members should also read Cutting Edge No. 440 for moreinformation.
About the CRI Podcast
The CRI Podcast features interviews with expert researchersand area extension managers from Citrus Research International, highlighting the science and field innovation that keep Southern Africa’s citrus industry competitive and sustainable.