Evaluate the effect of drape nets on the overall fruit quality of plums.

Plum producers sometimes suffer financial losses due to sunburn and wind marks resulting in lower pack-out percentages. This project is important because it will enable the industry to determine the effectiveness of drape nets to reduce sunburn and wind rub marks, as well as avoiding possible pit burn and external/internal heat damage that might be initiated during plum fruit development.

Drape nets were installed in one Laetitia and one African Delight orchard, after hand thinning and then subsequently removed at harvest. Branches were tagged and the length measured before the drape nets were installed and again after they were removed to ascertain vegetative growth. External fruit quality were assessed just prior to harvest. Yield and fruit quality was assessed at harvest. In addition, fruit quality was assessed after six weeks of cold storage and after a subsequent five-day shelf life.

2023

The difference in temperature between the untreated control trees (UTC) and the drape net tree canopies was between 1 °C and 6 °C warmer under the drape net during the day for the two (Laetitia and African Delight) orchards.

With Laetitia, drape nets decreased the sunburn and pitburn at the pre-harvest and harvest assessments, while sun pitting and rub marks were reduced after cold storage and shelf life.

With African Delight, sunburn, rub marks and insect damage were reduced at the pre-harvest and harvest assessments, by using drape nets. Rub marks and insect damage were less after cold storage and shelf-life by using drape nets.

2024

The difference in temperature between the UTC and the drape net tree canopies were between 0.25 °C and 1.0 °C warmer under the drape net during the day for the Laetitia and African Delight orchards.

With Laetitia, drape nets decreased the rub marks, insect damage and sunburn at the pre-harvest and harvest assessments. There was a reduction in sunpitting and rub marks for the drape net trees after cold storage and shelf life.

With African Delight, sunburn and rub marks were reduced by using drape net as ascertained at the pre-harvest assessments. The shrivel and sunpitting levels were significantly reduced by using drape nets, while internal heat damage increased on this population of fruit.

2025

In 2025, the canopy temperature under drape net was slightly cooler on average during the hottest part of the day (1 pm to 6 pm) compared to UTC trees for the Laetitia plums, while the temperature was similar for the African Delight between the two treatments for the same period of the day. Drape nets decreased the rub marks for the Laetitia plums, while rub marks and sunburn were reduced using drape nets on the African Delight plums.

Overall, over the three seasons of drape net research on plums the possible negative effects determined were: top shoots growing horizontally due to restriction by the net and rub mark friction on fruit if contact with the net itself.

2023

This study indicated no insurmountable negative effects when using drape nets on the two plum cultivars. With Laetitia, low levels of rub marks on fruit were caused by contact with drape nets and this was ascribed to tree architecture in the specific orchard.

The benefit of using drape nets was a decrease in sunburn, sun pitting, pitburn, rub marks and insect damage on fruit.

2024

With the exception of internal heat damage in African Delight plums after shelf life, no other negative effects occurred when using drape nets on the two plum cultivars. Laetitia exhibited lower levels of sunpitting, sunburn and rub marks on fruit under drape nets, as well as lower internal browning after shelf-life.

The benefit of using drape nets on African Delight was a decrease in sunburn and rub marks at harvest, while gel breakdown and sun pitting were lower for fruit after shelf-life.

2025

Drape nets reduced the levels of rub marks and sunburn in both cultivars. Sunpitting, which forms due to orchard heat, was evident in both treatments, with no significant differences. Drape nets did not affect the sugar and acid levels at any evaluation stage for both cultivars. There was also no negative effect on internal fruit quality due to the use of drape nets. However, there were higher levels of overripness after shelf-life for the 2025 season with the use of drape nets, but the reason for this is unclear since sugar and acid levels were similar for both treatments at this time.

The use of drape nets can be very beneficial with plum orchards and cultivars prone to rub marks and sunburn. The new bullhorn technology that was recently developed by DrapeNet^®, makes it possible to install the drape net more permanently and get cover sooner to reduce rub marks that develop early on the fruit. This has been used successfully overseas in peach orchards to reduce rub marks. Data from this project indicates that drape nets can decrease insect damage, by blocking them from reaching fruit if the trees are correctly covered.Cost benefit calculations must be done on a per case basis.