Ask-a-Dave's-Gardener: TOMATO HELP...yellowing leaves spreading fast, 3 by vlkgarden

vlkgarden wrote:
Briefly...I have 4 raised beds planted with assorted veggies. I use an drip irrigation system so all beds receive the same water amounts. I interplanted this year- wanted to try planting different things together instead of all of one kind in one bed mostly because of past insect problems. One of my tomato plants began developing yellow leaves a couple of weeks ago. I googled pictures of the leaves and found conflicting info - too much or too little water, different mineral issues, but I couldn\'t find an exact match of any photos to my leaves. I gave up until now...the yellow leaves are on several plants in different beds. It has rained a lot so I turned off my irrigation system. I\'ve added some Sulfate of Potash Magnesia and a little alfalfa meal thinking they may help. I\'ve also sprayed with neem oil in case it was fungal. Unfortunately things have gotten worse! I noticed that some leaves have green veins and yellow around them while others are purely yellow. The green veins are new - it started with purely yellow leaves with no brown spots. I\'m posting photos - anyone know what the problem might be? If not for saving the plants this year, I want to know and understand how to prevent/help correct the problem going forward. Thanks in advance!!