Irrigation Strawberry dry-down

Irrigation in strawberries seems to be one of the hardest issues. If i ask growers i work with 90% of them will mention this as so.

In my last post on LinkedIn, i had a poll about the dry down for strawberries overnight. Interesting to see 640 impressions, but just 16 votes. An indication for the fact that good irrigation is hard working?

But first, what is dry down? Dry down is the difference in moisture content between the frist irrigation in the morning and the last one of the previous day. In the schedule aboveyou can see the level at the irrigation of the previous day and the level at irrigation of the current day (between the red lines in the graph above).

Interesting to see the answers also: no one voted for 4-6%. Although i didn’t mention the substrate in this poll. I ment to ask for organic substrates like coir or peat.

Most of the answers where on the 9-11%. For Rockwool where dry down is a known concept, i do think 9-11% makes sense. For coir i see 4-6% as the optimum. Reasons:
– Rockwool 9-11%:
* Strawberry is a plant that really likes air / oxygen in the rooting zone. The best soils are still the coarse sandy soils. The best substrates those with a lot of oxygen/air in the rooting zone. The oxygen content in Rockwool is essential lower as in most coir i see. A period with more oxygen in the rooting zone is essential for good root growth. A higher dry down can help therefore.
– Coir / Organic substrates 4-6%:
* Several items are directly related to this percentage:
** Tip burn (or calcium deficiency in the young leafs / flowers)
about more then 90% of the tip-burn i see is not related to fertilizer recipe but to climate. Calcium is passiv taken up by the plant with the sap flow (xylem). This means, Calcium is transported to those places where evaporation is taken place. Only in case of rootpressure it gets everywhere.
Low moisturecontent in the evening means low root pressure and thus higher risk on tip-burn.

** Root health and fluctuation in moisture content. Strawberry generally grow better if the fluctuation in moisture content is not too big. Periods with relative wett substrate seems to influence both rooting as well as browning of the roots, probably because of oxygen deficiency.
** EC / drainage. Strawberry have an optimum EC range from about 1,3-2,0. In case of low drain percentages the EC increases causing mainly yield and quality issues. In case of high dry-down more irrigation water is needed for remoisturing and less time on the day remains for drainage. This can be seen in quite strong increase of drain EC in case of high dry down levels.

LAI = Leaf Area Index

Those experiences bring me to the following numbers:
– optimum drip EC: 1,3-2,0
– optimum drain EC: 1,5-2,0
– optimum dry down:
– coir: 4-6%
– rockwool: 9-11%
-optimum drain percentages:

Important to know, that these numbes are quite general, but differ for individual situations. Irrigation is not easy, it is subject for at least a days discussion if not for a week.

One of the most important basics is, that strawberries don’t handle big fluctuations very well. Both in EC as in Moisture content. They almost always lead to quality issues and sometimes to growth issues.

This means very practicle, that if i have a too high EC, i don’t advice to flush it suddenly, but decrease it steadily, slowely. The same for moisture content, if it is too low, don’t suddenly increase the moisture content.

Bugs wk 38 Beauty

Again several beauties together.

White fly predators: interesting to see the black larvea in stead of greenish colored larvea. 2 growers stopped using insecticides and those predators turned up naturaly.

Interesting: outdoor screening in order to keep the heat out. Works fine so far.


Image 1 of 11

Bugs this week (30)

This time a nice sery of pictures, especially about the lacewing. The adventures of a young lacewing larva entering the big bad world (although – who is bad?).

But also: lacewing larve eating quite a lot more as aphids: spidermites, spidermites eggs, and thrips (in the flower).

I have seen lots of lacewing eggs last 2 week. Essential in all those cases is: no insecticides. One grower with quite a lot of nature around the plot: lots of lacewing, hoverfly, feltiella, andersoni etc all just from the surrounding nature.

Beauty in all its complexity

Bugs this week (wk 26)

This week again a nice couple of good bugs. Especially lots of feltiella showing up in strawberries within some spots with spidermites.
Between these spidermites also a sofar unidentified help.
Especially the Feltiella and the Hoverflies can consume huge populations of Spidermites / Aphids.

The interesting thing in those predators on the picture, is that most of them are native and grew in that crop by themselves. I see more and more, that the area around the strawberries is very important for the development of a natural population of predators.

Below pictures of:
– Feltiella egg. Feltiella is a great consumer of spidermites. It may delete complete colonies of spidermites on leafs.
– Feltiella Larva 2x
– Feltiella pupa
– Hoverfly larva (huge aphid consumer)
– Lacewing egg
– Ladybug pupa
– Ladybug larva
– A type of ladybug: Stethorus punctillum (with thank to Markus Hofmann)

Measuring growth – key to development

One of the biggest issues of growing strawberries is, that you may only experience the yield if you are in the last part of the growth. That doesn’t satisfy me. After 100 days of sub-optimal photosynthesis, we talk about quite a lot of growth thus money.
We love to bring that back to 1 day, or if possible even hours.

Below a system for measuring the growth of Runners. In the picture below you see the system.

On the left the gutter with container where the strawberry plants are growing. you see the runners from the container growing to the right. The tube there is weighing the runners. This tube is connected with electronic measuring cells.

The results are shown in the graph below:

Strawberry growth graph

– left hand ax: weight in kg/10 meter (including pipes etc)
– bottom ax: date
– green line: graph for weight
– reddish: EC
– blue: moisture (scale based)
– yellow: radiation
– Bottom bar graph:
– blue: amount of irrigation (per 2 linear meter)
– red: amount of drain


In the graph above you see the first results:
– Left ax: Radiation in joule and growth (gram/1000 joule)
– Right ax: Weight just before sunrise
– Orange: Radiation (Joule/day)
– Green: Growth in gram/10 meter/1000 Joule
– Blue: Weight just before sunrise

Interesting to see is the differences from day to day. Just these are the reason for measuring: why are the differences there and how can we use them for optimizing the growth and thus the results.

Bugs this week (wk 25) – cryptobug

Several bugs this week: from Hoverfly, to Aphids, Larva of Aphidoletes, Birds, Larva of Lady bug, and some plant reaction of chemicals.
The beauty this week was the Cryptobug. A volunteer, just got in that greenhouse. A little shy, but nice to see.

Bugs this week: 2023 – 22

Or bugs? Quite some different issues i ran in this week.

The first to mention is herbicide damage. Every year i see about 10 cases of herbicide damage. Especially from Roundup. It seems so easy to use, but in my view Roundup and strawberries just don’t combine. Just a little wind, a little movement in the air and there is yellowing and consequences for the crop.
On this picture you only see the consequences for the fruits / flowers. But there was also a slight yellowing of the leafs.

Aphids can be seen this year. But good to see the predators as well. On the pictures you see Aphidius (predated aphid), Aphidoletes at work, Hoverfly adult and Hoverfly egg. The Aphidoletes used to work very fine, at least if they are not combined with a bit more agressive predatory mites.

Mildew and Botrytis
Every year an issue. So far although we had quite some rain the botrytis levels are still very acceptable. In the picture below the very first sign of Botrytis: the red spot on the Sepal.
Mildew: this time the consequences for the fruit: an uneven coloring.

Bugs and substrate wk 21

Visiting strawberry growers brings always some nice surprices.

This time several predators (one of aphids) and 3 pictures of rooting in different conditions.

– An aphid
– Aphidius on the leafs of lemon (a grower who has lemon in a greenhouse next to his strawberries)
-Aphidoletes just finished its meal
-Egg of a hoverfly
-Egg of a lacewing
-Predatory mite. I sometimes see huge amounts. Especially where the climate is a bit tempered they may develop very nice.

Last weeks i have also seen huge numbers of Feltiella. Sometimes diminishing huge colonies of spider mites. Especially the native feltiella used to develop very good.

Nr 1: an example of very dry growing. Consequence: roots for 90% in the bottom 5 cm of the substrate. No buffer, in case of changing weather this directly influences the quality of the strawberries:
– if it gets wet, roots may get water soaked and suffer oxygen deficiency, causing yellowing of leafs and soft fruits
– if it gets dry, the buffer of water is too low, so plants will suffer water deficiency
Nr 2: A bit dry growing, with below the drippers good rooting, but between them not enough roots
Nr 3: clearly better rooting, but a bit more water would be better (you can see the huge amount of roots on the bottom of the substrate)

Cyclamen – strawberry mite

“If they would be as big as an elephant, it wouldn’t be an issue. “

Because they are so small, hardly to see, they can cause big damage in the strawberries. Every year again there are issues.

This year i have seen already several crops with problems with strawberry mites.

Below some pictures, you can see the misshapen leafs and flower buds.
It is important to know that not all misshapen leafs and flower buds are the results of strawberry mites. Other sources are:
– growing circumstances (cold / fast growth / frost)
– aphids
If you want to know if it is from strawberry mites, a check of the young leafs under a microscope is needed in order to determine the mites.

If you want to see them, you need a microscope with a magnification of at least 20 X.

The best place to spot them is between the very young not yet unfolded leafs. The eggs look like sand, larvae don’t have much color, adults are a kind of yellow/brownish.

There are several chemicals that might work, just if we could get them in place. Because they are hidden in the hard of the plant max 70-80% of the mites can be reached.

The best results are achieved with a mix of chemical and biological:
1- treatment with abamectine + wetting agent, with quite a lot of water. Goal is to reach the hard of the plant. (spray abamectine always during low radiation (evening), as it breaks down quite fast under high UV circumstances)
2- repeat after 7 days
3- after 10 days place predators (loose, not in sachets): Amblyseius Cucumeris 100-200 pcs/lm and or Andersoni 50-100 pcs/lm
4- after 7 days place predators (loose, not in sachets): Amblyseius Cucumeris 100-200 pcs/lm and or Andersoni 50-100 pcs/lm

Prevention propagation
Strawberry mites cannot handle high temperatures and low humidity. In Hungary we have very good experience with high temperature treatment right after sticking the runners. Right after sticking the runners 100% humidity is needed for the runners to root. In that time of frequent misting in the first week, if the temperatures go up till 50oC there are no strawberry mites, as well as spider mites, aphids etc left.

Normally it is a goal to reach that temperature of 50oC with 100% humidity, in order to have completely clean plant material. Recent research even showed that viruses seem to be killed at those temperatures.
Take care, following items are important:
– 100% humidity (normal misting: 1 minute + 5-10 minutes pause)
– temperature goal 0,5-1 hour/day: 50oC
– radiation max 400-500 watt (shading needed)

Roots rooting

We all know roots are essential for plant development. Problems with roots always effect production: or the amount or the quality.

Below several types of rooting: from dry deep growing till balanced roots all over the substrate.
Good roots
– have oxygen in the rooting zone (air between the particles)
– are everywhere in the substrate (from top till bottom)
– are white

If you see these pictures, just think in terms of how much water and fertilizer the plants may take up.