Author: Klaas Plas

Visiting strawberry growers brings always some nice surprices.

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

Bugs:
– 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.

Rooting:
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)

“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.

Treatment.
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)

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.

Most growers i know experience good irrigation as one of the hardest jobs in growing strawberries. A small optimum of the moisture content, a fast reaction on changes in recipes makes it the feeling of a balancing act without rod.

The only way to change this is, to act and check and correct and check and correct and…. Good strawberry growing is really top sport. Performing without loosing attention. Set priorities within your company.

I see it frequently in the values i measure and problems growers face:
– start often quite dry, with low EC’s
– during the season EC’s going up too high, substrates getting dry
– wet substrates, with leaf yellowing
– shelf life issues, or sensitive skins
– tipburn

Below you have some ways to improve irrigation. But before this one main rule: no sudden changes!
Plants adapt to situations, an example: A plant may grow under too dry circumstances, this means roots go down to the moisture, less stomata in order to prevent evaporation, thicker wax layer etc. Sudden changing to more irrigation will lead to oxygen deficiency in the rooting zone of maybe 80% of the roots. This surely will lead to soft strawberries, to leaf yellowing, maybe even root diseases.

In the meantime there are quite some possibilities to get a stable and quite good moisture content. It is just following the rules, but to keep it good, we have to follow them steadily:
1- set irrigation based on radiation. The correlation between evaporation and radiation is very high. If irrigation is based on radiation, irrigation will be more frequent in case of a lot of sun. In case of cloudy weather, it will be less frequent
2- Normal start at about 2 hours after sunrise. Or as i like better: about 25-80 joules (depending on climate) after sunrise.
3- Check what you are doing:
a- if possible follow the following items:
drip: amount, EC, pH
drain: amount, EC, pH
climate: radiation
b- calculation:
% of drain water – goal: depending on weather conditions and LAI: 5-40%
sum EC (total of drip + drain) – goal: 3,0-4,0
irrigation: amount/radsum:
evaporation: drip amount ((ml/m2 ) – drain amount (ml/m2)) / (radsum/cm2)
4- Register this, and act based on this information.

Above 2 pictures. The first one with balance irrigation: roots from top till bottom. The second one of dry growing: roots at the bottom of the container.

There is a lot we don’t see, and yet is there.

Take this strawberry root in coir. Beautifull isn’t she? Normally we don’t see her, but she is there in all her beauty and functionality. If she is missing, we will surely notice.

Look the plants in the spring developing. Beautiful, it seems – out of nothing. A few months ago, soil was hard frozen and seamed dead, now: flowers pouring out of the soil. Life in stead of death.

Eastern – a place where our life’s come together: misery, diseases, death and life. Sadness changes into happiness. Barren soil changes into oceans of flowers.

Life has a future, because God gave it a future.

I wish everyone blessed Eastern

These pictures you get if a grower gets enthusiast about predators, system thinking.

Spiders
Predated aphids on clover below the table-tops
Natural hover fly early in the spring
Natural Feltiella early in the spring

And to be honest, it is unbelievable how predators populations develop. So early in the season (March in Norther Germany is still Cold): Aphidius, Feltiella, Hoverfly, next to lots of other insects. Beautiful to see.

The relation of temperature with radiation is very important in plant development. It is one of the first subjects in plant architecture.
– If temperatures are low related to radiation, plants grow compact: more vegetative
– Relative high temperatures give long stretched plants: more generative

Below a table with the optimum relation between radiation (both radsum as well as Watthours) in the languages Dutch – Hungarian – English.

The temperatures shown here are the 24 hour averages. It would be nice if we could use these for the current day. With some corrections during the day that might be possible, but it is not necessary for the current day. Goal is that the 3 day average temperature and radiation agree, so not necessary for every single day.

Example today we have 1150 Joule, goal for 24 hour temperature is for standard growth 16,1 oC. If you want an eary crop, and you the LAI is good enough you can also raise your temperatures and use the “fast growing” column, thus with 1150 Joule go for 18oC temperature.

Calculation of radiation from your LEDS:
capacity of LED in umol/m2/sec x 0,0036 = PAR mol/m2/hour
Example: capacity LED 200 umol/m2/s –> 200 x 0,0036 = 0,72 mol/m2/hour PAR
10 hours light from LED = 7,2 mol/m2/day PAR

A time to think back and look forward.
Thinking back, you may see the pictures in this post. All a beauty in itselve i think. For me every picture shows the huge complexity around strawberry. A very small part of creation, where from strawberries not even 1% is discovered or known of what is good to know.
I see:
– growers working as good as they can to grow beautifull and dilicious strawberries
– propagators, using all their time and energy to have excellent plants
– breeders investing all their knowledge for better varieties
How many man-years would it take a breeder to breed a new variety: 10 man-years?
And what about whole new strawberry plants? How many man-years would it take to breed or produce 1 strawberry plant out of nothing. In all its complexity: evaporation, stomata, roots, energy production, hormons, photosynthesis, pollination, plant reaction to: humidity, temperature, insects, fungi etc.

Looking forward, take your time to enjoy the crop you are working with. In all its beauty, complexity, excellent taste etc.
For me to see all this complexity and the work we do to keep them as good and beautiful as possible, also means, it didn’t pop up just out of the nothing. A great Infinite Designer made them for our joy.
Christmas means for me: after this year, a new one is waiting. After this life, a new one is waiting, because Christ made it possible.

Wish: blessings in Christmas, blessings for the new year and joy in your life.

Just for who is interested: a video of one of my clients cutting runners from strawberries on elevated beds.

The end of season is approaching, so predators are more seldom. Therefore some other pictures that might be interesting.

The one i love the most is the young lacewing larva, eating its way through a colony of spider mites. They were really doing a good job there.

The effect of an wetting agent is also good to sea.

And the the differences in the air in the substrate. In this case the coir with lots of air and the peat with only a little air.

The leaf wasp is a very active insect. The larva can cause lots of damage and are very hard to control. They look like a caterpillar, but don’t react on the same treatments unfortunately.

lacewing-larva

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