I need some help guys, I have been seeing red leaves in my new shiraz block. I have attached photos.
There are several problems that will turn vines red like the one shown above. Redness is a sign of restriction. There are four possibilities;
1- String restriction. Young vines can be ring-barked by the string used to tie them. Also wind damage can damage the young vine, cracking it and turning the leaves red or yellow.
2- Nematodes. On light, sandy soils nematodes can attack the roots of young vines restricting growth and causing stunted growth and red leaves.
3- Cutworm or African Black Beetle. These insects live under the soil and ring-bark vines under the ground. They both also damage leaves. They are best seen at night when they are active above ground, otherwise search the soil.
4- Graft failure. For grafted vines check the union between the scion and the rootstock. If this is damaged or has failed it will cause red vines as shown above.
Healthy vines like the ones below are have now been topped and the grower is waiting for lateral growth to wrap down on the wire. Watch for Powdery Mildew building up on young vines as it can limit shoot growth and lead to disease issues in future seasons. Good control now makes control easier next season.
|Healthy vines. Good leaf colour.|