Q: The bottom leaves of my tomato plants are getting a dappled yellowish color. Is this a disease? They are in a small greenhouse and I am liquid feeding them. I did spray them with a broad spectrum fungicide. I am seeing some on some outside plants as well.
A: It appeared to me a nutritional issue, as you indicated was uniform across all the plants with some variation between varieties. The yellow spots weren't developing into brown dead spots or patches. To make sure I asked our greenhouse expert at MU Extension, Dave Trinklein, for his opinion. His response was: "Based on the size of the leaflets, the plants look hungry. I think nitrogen definitely is involved; magnesium could be also. The typical liquid plant foods quite often are low in analysis so they can boast a low salt index. I think this often results in nitrogen starvation for heavy feeders like tomato."
Given you have ground fabric down, your only solution is to really up your game on liquid feeding. Do so with every watering until you see some improvement, following the products instructions. Rotate between products that (while feeding nitrogen) also provide potassium, magnesium and calcium. A soil test could be helpful if you haven't done one previously. Also make sure you are irrigating enough during this hot weather. Moisture stressed plants also develop yellowish leaves.
Q: I have a grassy weed that has a purple base and grows faster after mowing than my tall turf-type fescue I seeded last year. I did have problems with yellow nutsedge last year but controlled that. Someone told me this was the same, but I think it looks different. How can I control it?
A: Good job, it is not yellow nutsedge. Common barnyard grass is about the only warm season grass that has a purple base. It would out grow your cool season grass in this heat. Two relatively known post emergence products that can control it are Tenacity and Dimension. Be sure to read the label carefully; applying when we have heat and humidity can require careful timing. If you have irrigation it should be helpful, as your cool season grass would not be moisture stressed.
Q: I have some blackberries that have a lot of discolored spots, both white and brown. Much of the fruit looks OK. Are they safe to eat or still edible? Can I do something so other fruit is better?
A: Unfortunately, I have some experience with this. The berries are edible. I would suggest you juice them or something where you make product out of the juice. The color from the whole fruit in jam won't be that pretty. Cooked in a pie might be OK, but with those discolored parts, the flavor can carry with the whole fruit.
This is typical symptoms to heat and moisture stress, but it can also occur with stinkbug feeding. I would water more if you can, especially as we head into yet another hot and dry week. You will have to continue watering for as long as you have flowers and developing fruit. That would be through the end of July and possibly into August. Another symptom of moisture stress is when developing, immature fruit just kind of fizzle. If that has happened, you are really set back, as new flowers will have form and set fruit. Using a soaker hose or similar will make this task much easier.
Q: Could you please advise me what to do with a magnolia tree? It has these white things on it and is getting all this black mildew like substance on the leaves. A professional yard care company sprayed it with an insecticide and I don't think it did any good.
A: I think this is the dreaded magnolia scale; I get one or two calls on them every year and they are often misdiagnosed. They have this white crawler stage mid-summer where they look more like big mealy bugs. These harden into a scale. As with mealybugs, scale and wooly aphids, their coating repels most insecticides. One needs to smother them with oil or use a systemic insecticide.
I recommend to first apply a summer horticultural oil. Carefully follow its directions; if applied on a hot and sunny day, it can burn the leaves. Apply a drench of the insecticide with the active ingredient imidacloprid and follow the label instructions, which should include to follow up with a good watering. It will take about two weeks to have noticeable effect.