Answer: If your plants are developing yellow leaves and you find webbing in the plants, the likely cause is a tiny insect called a spider mite. These little pests love hot, dry conditions. They feed on the stems and undersides of the leaves and cause the leaves to yellow and eventually die. A really huge population will be difficult to control so if your plants are really in bad shape, you may want to toss them all and start over with healthy new plants. If you want to try and save the plants, there are insecticides in the garden section of your favorite nursery that you can use to spray your plants. Spider mites love hot, dry places so hosing your plants off every few days will help deter the pests. As for watering, it's difficult to predict. Containerized plants in full sunshine will require lots of water. If your drip system is inadequate, you may want to redesign it, splitting the system, or putting on a second system so the water pressure is high enough to water the planters at the far end of the deck. Or, you may want to hand water your plants, which will give you an opportunity to sprinkle the leaves and stems to ward off spider mites.
Best wishes with your planter boxes!
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