Q: I think our avocado tree has black streak disease and I need to know how bad it is and what to do. Is there anyone you would recommend to come and take a good look? I am in Oakland.
A: Avocado Black Streak symptoms include dark, streaky discoloration on the trunk and underside of larger branches of avocado trees. These streaks are sometimes accompanied by cankers that ooze sap. The sap will dry into a white or brownish powder that washes off easily with water. The trunk discoloration can be just in a few small areas, or it can cover large portions of the trunk.
If you scrape the dark part of the trunk, you’ll find reddish-brown diseased tissue just under the bark. This tissue can be scraped away, revealing seemingly healthy plant tissue underneath. Don’t be fooled, though. A tree can succumb with only a few lesions visible. This indicates that the lesions are only a symptom of a more systemic disease rather than the immediate cause of the tree’s decline.
Black streak was previously thought to be caused by a virus, but recent studies suggest that it’s caused by one or more fungal infections. The disease appears in trees that are stressed, specifically water stress or excess salts in the soil. It is more common in Guatemalan varieties that are grown in California. Affected trees can decline either very quickly or very slowly. If you’re lucky, the tree can recover if the source of stress is addressed and corrected.
If you need expert advice that is specific to your area, I recommend contacting the cooperative extension office for your county.
Q: I feed the stray cats and other critters that come by. My problem are the rats. They eat my hanging plants and they eat the top of other plants. I can’t set poison out. I’ve set traps and caught a few. I’m at my wits end. My creeping Charlie and my Pothos both were eaten last night. Got any tips?
A: Leaving food out for extended periods of time can attract some undesirable customers. If you only want to feed the cats, I suggest leaving the food out for only a limited time sometime before dark. If you put it out at the same time every day, the cats will quickly learn when dinnertime is and will make an appearance. Once they’ve eaten, remove any leftover food and/or empty dishes. If you want the cats to take care of your rat problem, feed them enough to keep them around, but not so much that they become overfed and lazy.
Related Articles
Master Gardener: What you can expect when planting fruit trees
Houseplant care during the winter months: What to do
What to do if squirrels are raiding your garden fruit trees
Want to remove your lawn? Here are low-water groundcover alternatives
Rats are notoriously smart, so trapping them can be a challenge. Snap traps are humane and environmentally friendly, but they will learn to avoid them after a while. Electrocution traps are a bit more expensive, but they are humane and quite effective.