Viper summer newsletter, 2010

Topics: Setting and fruit load during hot summer period. Powdery mildew Fruit quality and EC levels during summer

Setting and fruit load during hot summer period

By early July we normally are getting into the hot and humid weather. Days and night are more less even in temperature and humidity, and difficult weather conditions (as severe thunderstorms and tornados...) can make climate control a big challenge. Viper is a variety which normally sets well also under hot conditions, there is a couple of key tools the growers should consider using; picking twice a week to unload the plant fast. It is important to keep between 35 and 38 fruits pr plant, higher will create lower fruit size, and lower number can create a vegetative plant there will have difficulties setting later on again. Flagleafes should have been made already back in April to create a larger leaf surface for the plant to work with during the hot period. It is still important to keep Flagleafes on Viper during July and august. Some grower choose to leave 2 leafs on the sucker, depending on your greenhouse construction and planting density, it should be something you already have considered. Do not leave any fruits on side shoots, again this will create too high fruit count pr m2 and lower your fruit average size.

Powdery mildew

The last couple of years we have seen more and more powdery mildew around, and some of the fungicides are not working well against the powdery mildew anymore. When you first have got powdery mildew in the crop it hard to control without spray applications. Every time you spray the crop it will eventually cost production, so take all the precautions you possibly can. Check your vents, are all opening and closing as they should? Do the vents need calibration? Do you have any ripped poly? Try to avoid drafting; you might have to set you maximum vent position different from day to day to get a fast reaction on you climate control. Make sure overhead doors and man doors to greenhouse are kept closed. It is also still important to keep you climate active, especially during the early morning you should still be working with a minimum pipe. Sulphur burners are one of the most effective preventative tools you can use, you can also apply sulphur directly on your heating pipe, just make sure you apply it at a time where you actually are having a minimum of 40 Celsius on the pipe to get the effect of the sulphur. Sulphur can be hard on you biological balance, so keep a good eye on the balance.

Fruit quality and EC levels during summer

In order to keep the quality good you will need to maintain a good level of EC in the slab, I suggest keeping EC around 3, 5 to 3, 9 in the slab (taken out of the slab in the morning before watering start). Also keep you feed EC up to around 2, 5 as the lowest feed. When you start in the morning a slightly higher EC will help you prevent cracking and split on shoulders on fruits. The last shoots during late afternoon should also be given at a slightly higher level, around 2, 8 as well. During the hottest time of the day you can afford to lower Ec to around 2,5 to help the plant uptake the water easier, but it is very important to get the Ec back up later in the day. Most growers are working with recycling water as well, I suggest to take water samples from your slab and feed frequent when using recycling, this is the only way for you to know the levels of the different nutrients. Keep a good eye on the balance between N-Ca-K. Again, picking often gets the fruits off the plant as soon as they are ready, the longer the fruit stays on the plant the bigger risk for fruit quality issues.