No forecasting methods have been developed for Phytophthora fruit rot. However, the risk of rotting in store due to Phytophthora can be assessed pre-harvest based on orchard rot history, the amount of bare ground in the orchard, % crop <½ metre (knee height) from the ground and the accumulated rainfall in the 15 days prior to harvest.
- Identify orchards at risk from Phytophthora rot in July so that rot management strategies can be formulated.
- At risk orchards can be identified based on orchard rot history, amount of bare ground and likely incidence of low hanging fruit.
- Reassess these factors nearer harvest in August / September.
- Estimate the bare ground under trees, taking into account mulch and weed cover:
100% bare ground (overall herbicide) = high risk.
0% bare ground (overall grass or mulch or weed cover) = low risk.
20% or >bare ground (herbicide strip) = moderate-high risk.
- Multi-row bed orchards are most at risk.
- Select 20 trees at random and assess the percentage of the crop <½ metre (knee height) from the ground:
15% or >of crop = risk.
- Monitor rainfall in the 15 days before harvest:
20 mm or >accumulated rain = risk.