Question: My zucchini plants are healthy and producing many blossoms and fruit now. Last year many squash plants in my garden were infested with the squash borer but I can’t remember when I first noticed them. When does the squash borer typically show up in our Tucson gardens and what can be done to keep their damage to our plants to a minimum?
Answer: The squash vine borer (Melittia cucurbitae) is something you should be looking out for as soon as your plants are in the ground. The temperatures are warm enough in Southern Arizona to accumulate their required 100-degree days early in the year, and this allows the adults to start flying as early as late February. You can calculate degree days for your specific microclimate to be more precise or you can use one of the calculators on the internet. I like the visualization tool from the National Phenology Network that allows you to choose specific dates and locations to track the temperature accumulation (www.usanpn.org/data/visualizations). The adult moth looks a bit like a wasp, has an orange body with black wings, and will lay eggs near the base of the plant. The eggs can be removed by hand if you find them. They are very small, these reddish-brown circular eggs, and you must get close to the ground and lift some leaves to see them. Once they hatch and the larvae enter the stem, they are mostly protected by the plant. Where the young larvae bore into the plant there will be a small hole with frass (insect poop+debris) near the port of entry. Some people will turn into plant doctors and do minor surgery on the stem to remove the larvae once the signs are apparent. This is a test of your dedication to the zucchini.
Question: We have 22 oleander bushes lining both sides of the property line and the alley side. They are all about eight to ten feet high and healthy, but in the last two years, two of the white flowered bushes have not produced flowers. We planted them about seven or eight years ago, but have never had this problem. All oleanders have produced flowers of different colors yearly except the two I have mentioned, for the last two years; they will produce new ‘’chutes”, which are obvious, and they will grow, but will not bloom with the white flowers. All the other 20 bushes do produce the flowers. We have white, red, and pink oleanders. All oleander bushes were planted about four to five feet apart.
We also have a healthy rose bush that produces really nice and big yellow roses, but within two or three days they shrivel up and fall. Another healthy rose bush would produce a light purple flower, but the bulbs are there, without opening. What can we do?
Answer: Oleanders bloom on new growth so it is curious that yours are showing new growth but no flowers. You might try light pruning to encourage more branching and potentially more flowering. The other factors that could be considered are amount of light (they do well in full sun), occasional slow release nitrogen fertilizer, and of course, proper irrigation. The yellow rose could be a variety that only blooms once a year. If you have more information about the plant or photos of the flowers, we might be able to puzzle that out. The rose with buds not opening is likely due to environmental stress. Occasionally we have weather that affects the growth and some buds don’t open.
Question: What’s going on with my cauliflower?
Answer: Your cauliflower bolted. This is early flowering in response to warm weather. Ideally, cauliflower can be planted from September through February but in some years spring temperatures are warmer earlier in the year. This year we saw spring temperatures three weeks earlier than the average so plants are reacting accordingly and blooming earlier than we may have planned.
Question: The apricot tree that I planted last year died this spring of crown gall. We don’t know how the tree got it. The location on the east side of my house is dug into a basin that receives the grey water from my washer and roof run-off. I removed the apricot and a lot of soil and all the root we could find. I was advised not to plant a stone fruit there for at least one year and possibly three years. Is there anything I can do to the ground to plant another apricot? If not, I would like to know if there is any other fruit tree that I could plant now or this fall since it is set up to receive so much water. I just planted a mandarin orange in the front and already have a large fig tree and pomegranate, so I’m not interested in more of those.
Answer: Crown gall is a disease caused by bacterium called Agrobacterium tumefaciens and introduced to plants through wounds. The wounds can be from pruning or cracks in the bark or roots so it’s wise to be careful with planting and to clean your tools between pruning cuts. Many different woody plants are susceptible and the bacterium is common in many soils. The best way to treat the soil is with heat. You can solarize the area with plastic but the temperature needs to reach 140 degrees for an hour so this is the time of year to try this method. When replanting into a previously infested area, it is best to wait a couple years and/or use plants that are either immune or resistant to the bacteria. These don’t include any fruit trees but maybe you can be happy with a redbud or a pine.