The vast majority of crops started with good quality plant material. For a few growers, the plants were insufficiently protected from the cold during transport. The resulting shocks in plant temperature and evaporation can significantly slow growth at the start of cultivation. At several growers, with various segments, we observed aerial roots that were sometimes already taking root. This appears to be mainly caused by the plants receiving excessive (LED) light during propagation. These aerial roots have now mostly been removed.

Partly due to the relatively high radiation in December and early January, we're generally having a smooth start to the crop. The somewhat darker and cooler weather of recent weeks is now causing a slight delay. For cherry tomatoes, fruit set is now well underway, with production of approximately 25 to 35 fruits per m² per week. We're seeing somewhat fuller crops where the extra tops were removed in one go. These extra suckers produce more vegetation and moisture in the first two weeks. The risk of retaining these extra suckers (too) early is that the temperature will have to be lowered further later if the light levels are lower. We therefore often see that fruit set is somewhat more difficult under these conditions. To allow the plant load to grow in line with the expected radiation, fruit set on the last extra sucker in week 11 to 12 is optimal (based on the light levels in Belgium and the Netherlands).

Current situation of our varieties (unlit cultivation)

Prodelle and Duelle 
Quite a few earlier plantings have already doubled by the end of January, reaching their final spacing. We recommend removing a leaf from the head at that time. In the earliest plantings of Prodelle and Duelle, clusters 2-3 are now in full bloom. The first cluster is often single, after which almost all clusters are double, even with three branches. These "multi-branching" varieties are seen slightly more often in Prodelle than in Duelle. We recommend pruning these clusters and/or retaining a maximum of two branches. Especially with the current, somewhat darker and cooler weather, we are seeing quite a few open flowers; more than 3-4 open flowers per branch indicates that setting will be delayed. Monitor the flowering period and, if necessary, introduce additional bumblebees and steer the crop more generatively (increasing the day/night difference).

With later plantings, with the increasing light, it is especially important to steer generatively and with a sufficiently high daily temperature. Due to the lack of sufficient plant load, these varieties can more easily start to grow vegetatively. Sufficient generative management ultimately benefits plant balance, production and fruit quality.

Prodelle and Duelle continue to produce splitting bunches easily throughout the year. Pruning will generally not be necessary for the time being. As previously mentioned, crops with many three- or four-stemmed plants will require pruning to prevent the plant load from increasing too quickly. We recommend a final spacing of 4.5–4.7 heads/m².

Bonelle and Sweetelle
The plant material of the ToBRFV-resistant Bonelle (TIAM24-5016) and Sweetelle was very good. The crops are now generally well-balanced, with beautiful, strong bunches. Bonelle also shows very rapid bunch formation and set. As always, we see slightly fewer double bunches on the first bunch (often <40%), while on bunch 2 this is generally 50% or more. If more than 3 to 4 flowers bloom per stem, action must be taken (see advice for Prodelle and Duelle).

When cluster 4 is in bloom, you can start removing the second blooms on cluster 1. We recommend tipping (removing the second blooms) at least to cluster 4-5. Sweetelle will need more generative management until about cluster 5-6, after which it can be steered more towards vigor and growth. Bonelle will easily continue to grow more vigorously, while maintaining good flower production and set.

As a final distance for Sweetelle, we recommend 4.4 heads/m2 in a slightly older greenhouse, up to 4.7 - 5.0 heads/m2 in a (very) new greenhouse with diffuse glass and plenty of available CO2.

Adorelle
Adorelle is now reasonably well-balanced, but it does require considerably more generative guidance. The first cluster often produced two stems, the second cluster was more single, and then again, mostly multi-stemmed. This variety is characterized by its very strong growth. Depending on the crop's condition, don't start the slab too early. If the crop is too vegetative, you can wait until the third cluster sets. Of course, also pay attention to the available water volume in the block.

For this variety, we recommend a substantial day/night difference for sufficient trusses. In vegetative growth, feel free to aim for a DIF of 8-10°C. In the case of an excess of assimilates, extending the day is a good way to steer the plant generatively while maintaining an optimal growth rate. Keep the crop sufficiently open by removing a leaf from the head of each truss for the time being. Pruning is generally not necessary for Adorelle.

As a final distance, 4.4 – 4.7 heads will be sufficient in growing areas with a maritime climate.

Our other cherry tomato colors: Tatoo, Baldomero and Ivorelle
The Tatoo and Baldomero varieties are similar in plant type and are now slightly open, with generatively strong (split) bunches and rapid fruit set. Both varieties easily achieve balance. With these varieties, it's only necessary to consider removing a leaf from the head at the start of cultivation.

The three-stemmed varieties can be reduced to two. As the plant load increases (from approximately clusters 5-6), it will need to be regulated more through pruning. Our new variety Ivorelle (TIAM24-5008) produces beautiful, light yellow fruits with high Brix. This variety's crop type is more vegetative. Therefore, it requires sufficient generative management year-round for optimal quality and productivity. Feel free to take a leaf from the head throughout the year. Pruning is generally not necessary year-round.
With these three varieties, we recommend using sulfur vaporisers (if permitted) as a preventative measure to suppress powdery mildew. If sulfur is sprayed against russet mites, this will not be necessary.

Romidoro and Romindo
With our new ToBRFV resistant plum tomato varieties Romidoro (TIAM23-4633) and Romanto (TIAM23-4621) we have a nice addition to our range.

Romidoro is a vigorous, generative variety with a remarkably high truss production. In unlit cultivation, this variety can easily produce 34 to 36 trusses. The first truss is usually pruned to 5 (in earlier plantings), and sometimes to 6 later. Romidoro produces flowers readily throughout the year, setting them quickly. We recommend pruning off the last one or two flowers for the most uniform fruit size possible and optimal production. We also recommend pruning or removing the trusses until around March 15th. As a summer spacing, we recommend 3.75 to slightly more than 4 heads per m², depending on the greenhouse type and desired fruit weight.

Romanto is a slightly more vigorous variety with larger fruits. This variety is also very suitable for bunch harvesting. For Romanto, remove a leaf from the head for the time being and encourage sufficient generative growth. For this variety, too, we recommend pruning the last one or two flowers per bunch for the most uniform fruit size possible and optimal production. Romanto has a slightly longer bunch stem; we recommend continuing to brace or pluck for a little longer than usual to encourage good fruit development. For Romanto, we recommend a slightly lower final spacing: approximately 3.5 to a maximum of 3.75 heads per m².

Both varieties have a slightly higher potassium requirement initially. Therefore, monitor the potassium level closely and adjust upwards in a timely manner. Later in the cultivation period (from approximately early to mid-April, when evaporation exceeds approximately 5 liters/m²/day), it is important to aim for a higher calcium dose and reduce the potassium dose slightly. Also, be cautious about using ammonium nitrate to control pH. We'll discuss this further in the upcoming cultivation information.

Macrolophus appears to develop easily on both varieties. Be careful not to let the macrolophus population get too high (no more than approximately 8-12 individuals per plant).
 

Advice on climate control (temperatures, window positions, humidity, pipes) for the next 6-8 weeks

How can we best utilize the increasing irradiance?
Insolation will normally increase significantly over the next 6-8 weeks, with cool nights remaining for the time being, allowing us to achieve the desired 24-hour period. To maintain good plant balance in the aforementioned situation, first optimise the daytime climate. The maximum daytime temperature with high irradiance depends on the crop's condition; this will vary between 23-27°C.

Overly vigorous crop and assimilate surplus
For a crop with an assimilate surplus, we recommend maintaining the daytime temperature longer and moving the pre-midnight period later. This is a good, and relatively inexpensive, way to achieve and/or maintain crop balance. For a crop with an energy surplus, plant balance is much more important than the light blocked by the energy screen during the last hours of the day. Therefore, we recommend maintaining the midday temperature in such a case by closing the screen, if necessary, from approximately 3-4 hours before sunset. Also, pay attention to the expected irradiance. At high irradiance (in clear weather), the screen can slowly close at an irradiance of around 250 W. Excess moisture can be vented (very carefully) above the screen.                                            

How to deal with insufficient light
If the light sum is insufficient for the plant load, control should be based as much as possible on the (limited) available light. On dark days, a short peak daytime temperature of 21-22°C between 1 and 3 PM is sufficient. This activates the crop and stimulates flower quality and fruit set. A higher or longer peak daytime temperature is undesirable because it increases dissimilation.

Depending on the achieved daytime temperature, we should use the nighttime temperature to control for the desired 24-hour period. For the next two months, keep the 24-hour period between 16°C (very dark weather, high plant load) and 20°C with prolonged sunny weather for an under-stressed plant. Higher 24-hour periods are undesirable because they result in excessive dissimilation; this costs unnecessary energy and ultimately reduces production.

If the daytime temperature is easily achieved and the humidity is low, the minimum tube can be gradually reduced between 200-500 W of irradiance. Otherwise, unnecessary moisture, energy, and CO2 will be removed. If the crop is still too vegetative, it can still be decided to keep a minimum tube in place for additional activation. However, try to avoid "blowing open" the vents with the minimum tube (especially under an open screen). This will be counterproductive.

For weak, stretched bunch stems, a morning dip is a good way to increase bunch strength. However, don't set the temperature too low (<14°C), as this will hinder the plant's development too much.
 
Using energy screens / humidity control
General: When outdoor temperatures start to rise again, use a screen primarily at night and always monitor the humidity. Do not allow the humidity to drop below 1.5 g/m³ for extended periods to ensure healthy crops.

If the humidity in the greenhouse remains too high, you can ventilate above the screen, followed by a minimum duct of 30-35°C to remove moisture. This, of course, only applies if it is not too cold outside.

What are the focus points for the next 6 to 8 weeks?

Plant Balance – Extra Lifts
Getting and keeping the plant balanced is important. A good balance between the plant load and the available light sum is crucial for the coming months. It may sound a bit early now, but the plant will start producing new growth after the first harvest, and it's important to anticipate or respond well to this.

As mentioned earlier, the crop can still be quite full, especially if the final spacing is approached early. We recommend removing leaves from the heads to maintain the balance of the crop. If flowering occurs on more than three trusses (in the case of snack tomatoes), the flowering stem from the lowest truss can always be removed, except for varieties where otherwise indicated. This will not affect production and will increase yield standards.

Watering strategy
When the plants are established at approximately cluster 4-5, they should be in balance. The fruits will now continue to swell, and the moisture content in the rockwool slab can gradually be increased back to 70-80%. From that point on, aim for a minimum EC of 4.5-6.0 mS in the slab. As the plant load increases further, the drip EC can be reduced to 3.0-3.5 mS. For larger fruit types, this may be slightly lower. Try to drip between 2 hours after sunrise and 3-4 hours before sunset to achieve the desired watering. Be cautious with evening or night irrigation at low greenhouse temperatures or low moisture content. An unnecessary night irrigation can quickly make the crop too vegetative.

Fertilisation Schedule
For unlit crops that started with a generative (low) nitrogen schedule, it's important to increase the nitrogen content to at least 15 mmol/l starting around flowering cluster 4-5. This is absolutely necessary to maintain sufficient fruit and crop growth in spring!
During periods of high irradiance and vigorous growth, monitor the pH. A pH that is too high (> 6.5) can hinder the uptake of nutrients. However, be mindful of the use of ammonium nitrate in the irrigation water to regulate the pH. Excessively high levels in the irrigation water and/or mat can significantly lower the pH around the roots.
 

Diseases and Pests
In crops where a weak strain of Pepino was introduced, we noticed some signs of rot. This has since subsided. Generally, pest and insect pressure is still very low in the greenhouses. Apart from a few (lit) crops with gall mites, there are no other problems.

The next crop information is expected at the end of March.