Gardening season is in full swing, and you may have questions. To ask one, simply go to the OSU Extension website, type it in and include the county where you live. A photo is very helpful.
Q: What is tunneling into my Asian lily stalks? I saw what looked like a bee (yellow and black stripes) carrying a small purple petal into the hole? Will this cause permanent damage to lilies? – Benton County
A: You have sharp eyes to notice such a small entrance hole. Most likely what you saw is a leaf cutter bee. Here’s a link to “A Guide to Common Pollinators in the Willamette Valley in Western Oregon.” It is unlikely to cause permanent damage to your lily. They are good pollinators and should be quiet neighbors.
You must have an inviting space to be able to attract leaf cutter bees. Enjoy watching them this summer. – Anna Ashby, OSU Extension Master Gardener
HydrangeaOSU Extension Service
Q: I transplanted a hydrangea to a shadier area in spring and as the flowers have started to bloom, I’ve noticed a weblike covering on about half of the flower bunches. The flower bunches that have a web covering on them are also brown and shriveled, but the half that don’t have the web covering are fine.
Do you know what might be going on? – Clackamas County
A: It looks like you have a problem with two-spotted spider mites. These tiny half millimeter arachnids suck the juice out of the leaves, obviously make webs around the flowers and can severely damage the plant.
Lady beetle adults and larvae, lacewing larvae, thrips, and minute pirate bugs are all predators of these mites, but the shady area might not lure them in.
Cut off the webbed heads and put them in a plastic bag in the garbage so you don’t spread the problem. Wash mites from the plant with a strong stream of water. This dislodges dust and dirt that favor an increase in mite numbers.
Water your hydrangea properly, as drought-stressed plants are more susceptible mite damage.
Avoid excessive nitrogen applications, as this encourages mites. Since mites thrive under hot, dry conditions, increasing humidity with periodic short bursts of water to the foliage may help.
If you want to use a pesticide, chose from these ingredients to control the outbreak:
- acephate
- azadirachtin O
- esfenvalerate
- fluvalinate
- horticultural oils O
- imidacloprid S
- insecticidal soap O
- kaolin clay O
- malathion
- pyrethrins
- pyrethroids P
The O means it is organic, the S means it will go into the whole system of the plant and the P means it will kill a wide spectrum of insects, the good and the bad ones. Be sure to follow the directions on spray very carefully. — Rhonda Frick-Wright, OSU Extension Master Gardener
AcanthusOSU Extension Service
Q: I would love any advice on what’s going on with my acanthus mollis. These are in relative shade of a witch hazel tree and receive morning sun and ample water. We planted them in early May. And yet, the leaves are browning – the lighter-colored ones in particular are affected. What should I do? – Multnomah County
A: Leaf browning is most commonly an indication that there is a water problem — either too much or too little. You don’t indicate how much water it receives, and the very fine mulch you have around it may prevent water from reaching the roots.
I suggest that you remove the bark so close to the plant, and either leave it off or replace with large bark chips. Measuring soil moisture would remove guessing; you can get a soil water tester for under $10. Here is a general article about this species. — Kris LaMar, OSU Extension Master Gardener
Q: I am growing sweet corn and blue corn, and I want to prevent corn ear worms without using chemicals, Any suggestions? – Lane County
A: Timing is critical. If you wait too long, the damage will be great. Below are two tested methods for maximum, but not absolute control.
Manual control
If there’s just an occasional cornworm on your plants, you might get it under control by cutting off the tips of the affected ears.
Killing the eggs or just hatched larvae
Apply mineral oil on the silks five to seven days after the silk emerges. Using a pipette or a dropper, apply five drops (about ¼ teaspoon) of mineral oil at the tip of each corn ear.
You can also mix Bacillus thuringiensis (Bt) with mineral oil in a ratio of 1:20. For example, to treat 40 corn plants, mix ½ teaspoon BT with 10 teaspoons mineral oil and apply it with a pipette the same way as described above. Bt is listed for organic growing also. – Pat Patterson, OSU Extension horticulturist, retired
These grubs won’t survive in a jar.OSU Extension Service
Q: Can you identify this big grub?
Are they native in Oregon or in California?
We are going on a vacation in a few days. I am keeping them in a jar with air-holes. Will they emerge as adult insects in four days or so? Otherwise, I have to take him along on our trip.
A: Long-Horned beetles is the common name for Cerambycidae family. The common name of this long-horned beetle is hairy pine borer, Tragosoma depsarium. They are found in the Pacific Northwest from May-September. The adults come out later.
The larva will not live in the jar. I would suggest you put them back in the rotten wood where you found them and hope they survive. Do not take him on your trip. – Richard Little, OSU Extension Master Gardener
Can poop from a koi pond be used as fertilizer? File photo.
Q: I have a 12,000-plus koi pond, the best that I can measure. Every few weeks I dump 2,000-3,000 gallons of water and then put the same back in. My koi are fed with high-quality food, mostly from Japan.
So, I figure they have to have good quality poop.
When I lower the water, I scrape up a good amount of green poop, and let it dry or not. My question is can this be used for a person’s flower and vegetable gardens without any issues for them? – Benton County
A: I don’t think this will be a problem as long as you are not using any medications or chemicals in your pond, and you don’t have any ongoing infectious disease issues. – Dr. Tim Miller-Morgan, DVM, Carlson College of Veterinary School, OSU
