Gerbera & Roses growing article July 2006
 

Insects;

In the coming weeks I would advice growers to have a good look at the insects in their crops and take action to reduce these insects. This is to make sure that the insects are under control before the temperatures get higher and everyone gets busy on their farms with harvesting the spring flush.

A weekly monitoring program is advised for the early detection of insects and to evaluate the effectiveness of your spraying. Yellow sticky cards can be placed in the greenhouse to see which insects are in the greenhouse (rate of one per 500 M2). Keep records of population on the yellow sticky cards to find out if the number of insects are increasing or decreasing.

To get the best result with spraying it's a good to know what the life cycle is of insects (higher temperature in the greenhouse means a faster life cycle) and which chemical you have to use to get the best result.

Botrytis;

Over the last few months quite a few growers have contact me about botrytis in their flowers, hereby a few general tips to prevent botrytis;

Make sure that the temperature in the greenhouse is the same every where, if not use circulation fans to circulate the air in the greenhouse.

Try to collect the drain water so the ground stays dry, when there is no water on the ground the chance to get botrytis is less.

Remove all the old and brown leaves before the botrytis season start (early autumn / winter); make sure that the crop is open so the airflow is good around the plant.

After removing leaves a lot of botrytis spores are coming into the air, it's a good idea to spray the foliage with Rovrall or Scala to kill these spores after removing leaves.

It doesn't matter where you grow gerbera in Australia, but the use of heating pipes is the best way to reduce the chance of botrytis. Quick temperature rises in the morning or high humidity on dark days are the main course of getting botrytis.

A light spray / misting with Rovrall over the flowers could help to prevent botrytis, but make sure you try this first on a small area to see if you get spray damage.

Spraying for botrytis helps, but the most important thing is to find the cause why you have botrytis in your flowers. At the moment there are a few new chemicals on the market for botrytis, ask your supplier for information about these new chemicals.

Planting gerberas;

Planting should be done in uniformly moistened potting mix. Place the gerbera plant into the potting mix so the top of the jiffy pot is 2-3 cm higher than the potting mix. If planted too high, the plants might break at harvest. While planting too deep increases the risk of disease (crown rot). Prevent root damage by carefully pressing the potting mix against the pot. Under conditions with high daytime temperatures in the greenhouse (> 30°C) and too much sunlight, it is recommended to plant early in the morning or in the evening when the temperature and sunlight are less extreme. To allow a good contact between pot and soil, it is recommended hand water very soon after planting.

In the initial period after planting, when light is a minor growing factor shading of the greenhouse is recommended.

Prevent direct wind. In the initial period after planting, keep the humidity as high as possible.

Moistening of the plants after 2-3 weeks is not advisable, so wet leaf should be avoided.

As the plants are developing, the light intensity and ventilation of the glasshouse may increase. The plants themselves will have a major influence on the glasshouse climate by now (microclimate).

***Although we trust that this information could be of considerable help to the success of the crop, we cannot accept any liability for the results of your crop. All the information in this growing newsletter is without committing ourselves.

This article is written by Job Roskam of Roskam Young Plants Pty Ltd. and also published in the Australian flower industry magazine.