Avo Tech Tip 10/06/2021

Dear Trevelyans avocado grower,

Three important winter topics are: 

  • Pruning/ canopy management
  • Six spotted mite management
  • Regenerative planting if you are interested in soil regeneration

Six Spotted mites

Every winter and spring for a period stretching up to six or seven months six spotted mite levels rise.  Spray options become limited after August as we enter the export harvest season.  In addition levels can persist into flowering and the double impact of flowering stress coupled with six spotted mite feeding can cause severe and widespread leaf fall.  Mite affected canopies are also very prone to chilling and frost damage.

Figure above shows mite trends from the most recent 24 months including the peaks in winter.

Experience has shown that mites are best dealt with early in the winter period.  They should not be allowed to build up to damaging numbers.  The normal predators such as Stethorus are not active during winter and only build up in number that are capable of controlling the mite in late spring when temperatures are warm enough.  It is very important to consider predator insects as part of any mite control management plan.  

Based on mite pressure we encourage/ recommend growers to:

  • Use their Paramite spray in the mid-June to end of July period either alone or in combination with Abermectin.  Remember you can only use Paramite or Etoxamite once a year!  
  • Regular monitoring is essential to understand mite population movements.  
  • Mit-E-Mec is an option during late winter and early spring  and as an Ovicide will kill eggs.
  • Abermectin is most effective on soft new season so once the spring flush has fully extended.  You are only allowed three Abermectin sprays a year so use them wisely.

Our experience is that if growers lose control of this pest they struggle to regain control before significant canopy damage occurs.  

It’s a matter of regular monitoring and then when the time is right, dealing with the pest hard and early.

Winter Canopy

Maintaining a healthy winter canopy is very important in avocado.  As the avocado is a tropical/subtropical tree, it can struggle with canopy condition when temperatures drop in winter and the leaves suffer as a result of frosting events. 

Some issues we see with canopy this time of the year:

  • Photo-oxidation and autumn flowering

 

  • Light Frost damage
  • Boron toxicity
  • Potassium deficiency

Note – images are from The Avocado Problem Solver Field Guide

Fortunately, there are a number of options for maintaining canopy condition through winter including:

  • Running slightly elevated leaf nitrogen levels through autumn and winter.
  • Applying foliar nitrogen in the form of urea and magnesium in the form of magnesium sulphate in combination with abiotic (environmental)  stress reducers such as Stimplex.
  • Making sure your fertiliser programme is based on leaf and soil tests and addresses deficiencies and avoids toxicity.
  • Pruning off heavy autumn/ winter flowering shoots before too much surrounding leaf nitrogen is drained from leaves to support the flower development.  This should happen in the late April to end of June window before leaves yellow due to photo-oxidation and nutrient withdrawal by flowers.
  • Managing fertiliser timings to avoid/ reduce autumn flushing.
  • Having Phytophthora root rot under control.
  • Avoid late summer pruning and having too much new soft flush going into winter.

Regenerative seed mixes

Growers who want to plant regenerative mixes are encouraged to use seed mixes that generate different beneficial outcomes from nitrogen fixing, to carbon elevation, to soil compaction reversal to beneficial insect sanctuary….. to name a few.  Each site will have specific needs and growers can tailor their seed mix accordingly.  A key principle of regenerative farming is biological diversity in orchard floor sward so a seed “mix” is required.  Typically growers can consider using mixes/ combinations of the following:

  • Chicory
  • Hercules Plantain
  • Phacelia
  • Beans
  • Crimson Clover
  • White Clover
  • Strawberry Clover
  • Carrot
  • Yarrow
  • Allysium
  • Chard
  • Oats
  • Ryecorn
  • Cornflower
  • Radish
  • Blue Lupin
  • Sunflower
  • Borage 
  • Peas
  • Buckwheat 
  • Vetch
  • Linseed
  • Poppy
  • Cosmos
  • Marigold
  • Creeping Red Fescue

It is best to get regenerative seed mixes from seed companies that specialise in this area such as Pastural Improvements Limited https://www.pastoralimprovements.co.nz or for smaller trial pack Kings Seeds https://www.kingsseeds.co.nz/shop/Field+Selection/Green+Manure+%26+Cover+Crops.html

If you require more information or would like to talk over any of the issues covered in this Tech Tip please contact myself  (0279733513), or anyone in the Avocado Grower Services Team Daniel (0274866969), Katherine (0272119181)or  Anne (0276126636) (0279733513).

 

Kind regards

Jonathan