What impact does shade netting have on avocado production and fruit quality?

Losses in fruit for export resulting from wind and sunburn can be as high as 28% and 27% respectively. The shading provided by netting over a crop modulates the microclimate, allowing the environment to be more favourable for fruit production and for the reduction of quality defects.

A study conducted by the South African Avocado Growers Association raised several questions related to the netting growing technique, such as:

• What is the impact on flower development, pollinators and pollination?
• What is the expected return on investment?

Experimental plots were implemented in Mooketsi and Everdon (South Africa), with the aim to study the behaviour of honey bees under shading structures and compare them with the behaviour in the open air, as well as to study the influence of these nets on fruit yield and quality.

The netting used in the test was:

 

The graph below demonstrates yield under shade netting versus open field from 2014 to 2016 at Everdon Farm (South Africa).

^{Yield of the shade net vs. open field ochard, 2014 – 2016 Everdon, Howick.}

Its analysis shows that Class 1 fruit production under the shade netting was higher, compared to the open field orchard, with the following results in successive years of the test:

• 2014 – 23% more fruit (2.8 tonnes)
• 2015 – 42% more fruit (5 tonnes)
• 2016 – 13% more fruit (3.6 tonnes)

The total yield under netting was also higher for three consecutive years.

The study also analysed the economic feasibility of this production technique, considering total yield, yield of Class 1 fruit, production costs under netting and in the open field.

Simple calculations showed that production under shade netting increased the amount of Class 1 fruit by > 10%, leading to an average of between €1710 and €5700 (equivalent to R30 000 and R100 000, based on 2020 prices) of profit over the 3-year period.

Finally, the study finds that avocado production under netting is economically profitable, allows for a higher overall production of Class 1 fruit of good quality, as it reduces damage caused by wind, sunburn, hail, etc. And it does not interfere with bee activity, thus allowing the bees to work more efficiently.

Our proposal for this type of crop is the use of netting made flat with high-density virgin polyethylene yarns, with shading values around those specified in the test:

• Shade 20%
  
  • 40 Mesh – 16×10 yarns x cm2, clear
  • 25 Mesh – 10×8 yarns x cm2, clear
  • 17 Mesh – 7×5.5 yarns x cm2, clear
  • 13 Mesh – 5×4 yarns x cm2, white pearl and white

• Shade 30%
  • 25 mesh – 10×8 yarns x cm2, white
  • 13 mesh – 5×4 yarns x cm2, black and red
  • 17 mesh – 7×5.5 yarns x cm2, grey

• Shade 40%
  • 40 mesh – 16×10 yarns x cm2, red
  • 25 mesh – 10×8 yarns x cm2, red

 

_{Source: Growing avocados under shade netting. WA Stones, Z van Rooyen and JS Köhne. SOUTH AFRICAN AVOCADO GROWERS’ ASSOCIATION YEARBOOK 40, 2017.}