The weather is playing havoc with gardens and plants throughout New Zealand.
Too much rain and then not enough, too much wind and temperature fluctuations. Not ideal gardening conditions and plants suffer as a result.
I have had a number of people contact me in regards to three main things that have been happening to their tomato plants so let’s look at them and suggest what can be done to help or prevent the problems.
1. Temperature fluctuations can cause both Early and Late types of blight in tomatoes and the prevention and control is the same for both.
Early blight: finding small spots turning to a dark mould on older leaves will indicate the presence of this problem. It occurs in warm wet weather, but plants can be protected with a monthly spray of Perkfection Supa. If you know the disease recurs in your garden, give additional sprays of Liquid Copper and Raingard every 10 to 14 days.
Late blight: Here, you will notice brown, irregular patches on the plant’s stem and leaves. This problem is particularly bad in cool humid weather, and it can be controlled using the same methods as for controlling early blight. If you have not applied Perkfection Supa and the disease strikes, spray the affected plants immediately with Perkfection Supa at 7ml per litre of water. Add to this 3.5ml of Liquid Copper per litre, with 1ml of Raingard per litre, and spray the plants for total coverage of the foliage. Two weeks later, reapply just the Liquid Copper and Raingard, then after another fortnight, apply the same again with Perkfection at 4ml per litre. That programme will normally be sufficient to see the problem off, but if either blight returns, re-start the spray programme. Late blight is common later in the season, but under the right conditions will strike in the spring.
Potatoes and pepinos are also affected by this disease, but you can give them a similar level of protection using the same sprays as outlined here.
2. Next we have the dreaded collar or stem rot disease where we watch a mature plant with lots of green fruit slowly collapse over a period of a few days.
The disease will make itself apparent with the development of a darker area on the trunk – that is where the rot will be happening, blocking the flow of moisture and nutrients from the roots. Little bumps of aerial roots will often appear just above the rot area. If there is foliage below the part where the rot starts, particularly if it is producing laterals, then you can cut the top off and allow the good part to continue growing. The chances are you will avoid this disease completely if you don’t remove any laterals, and if the plant succeeds in avoiding any damage arising from being rubbed on a stake or something similar. One of the ways to prevent any problems is to remove the laterals when they are very small, which means checking the plant every day or two. Remove them only on warm days when there is low humidity, and spray the cut area immediately afterwards with Liquid Copper. You can make up a solution of this product in a 250ml trigger spray bottle, and it will keep for some time. Just remember to shake the bottle before spraying.
Removing older leaves might also make the plant vulnerable to disease. This is another job which should be done only in conditions of low humidity, and always remember to spray to protect.
Humidity levels will often be much higher in a glasshouse, which means special care must be taken to open up the greenhouse and remove some of the air moisture before taking off the laterals. I have heard that if the rot on the trunk is not too far advanced then painting undiluted Liquid Copper onto that area may save the plant.
3. Finally the unpredictable growing conditions may cause damage to leaves especially the lower ones which may twist, curl and be spotted, wither and brown off. Two aspects here – one is that a lot of tomato strains have a virus which does cause distorted leaves in maturing plants, there is very little that can be done about it other than removing those leaves when they are obviously not gathering further energy from the sun. Weather damage can be reduced by giving the plants more protection by spraying with Vaporgard, erecting windbreak cloth, adding more stakes for support and applying potash once a month.
Another problem a couple of gardeners have mentioned is blotchy ripening fruit which additional potash is needed. If you are using my Secret Tomato food and this happens then it would likely be the weather causing lock ups in the soil. Ensure that you have applied Organi-Bor to the area in the last 3 years (for Boron) and then drench the soil with Magic Botanic Liquid (MBL). Sprays of MBL over foliage every two weeks will make for stronger plants with less health problems.
Neem Tree Oil can be added to the MBL which will then give further disease protection as well as a control for the insect pests such as white fly and the dreaded psyllid.
Talking about insect pests, this morning I was out inspecting what damage the wind had done to the plants and whether the plants in the glasshouses needed a drink or not. On the cucumbers which are coming away nicely I noticed a few small aphids on the fruit that was forming. A closer inspection and the turning over a few leaves I found hundreds of aphid pests on the underside of several leaves, not good, so tonight they will have a bath in Neem Oil and Key Pyrethrum spray. I had the same problem last year on zuchini and because the pests are under the leaves and not readily seen nothing was done till the plants actually started to die off prematurely.
A spray of the Neem and Pyrethrum knocked them back and the plants started to recover.
So with your cubit plants which also includes melons and pumpkins check under the leaves now and then for pests.
Leaf hoppers (the young are called fluffy bums) vegetable beetles, psyllid and other pests must be controlled on plants now otherwise you will have a real battle in weeks to come. Sprays of Neem Tree Oil with Raingard added can be applied late in the day, just before dusk to great advantage in keeping diseases and pests at bay. If you do not add the Pyrethrum you will not harm beneficial insects and only add the pyrethrum when you have a out break of pests on a plant/s so the spray is focussed on the pests. Not a broadcast spray which will affect both good and bad insects.
That’s another of the problems with all the chemical insecticides: they take out all beneficial insects and with some of them they don’t even harm the pest ones, which have now gained resistance to the poisons. Waste of time and money not to say anything about your health aspects.
On the other hand Neem Oil is not a poison and it does not kill anything unless the oil smothers a few pests such as scale and thrips. Instead it either shuts off the insects ability to feed or grow and when that happens they will die after a few days.