Gardening season is wrapping up but you may still have questions. For answers, turn to Ask an Expert, an online question-and-answer tool from Oregon State University’s Extension Service. OSU Extension faculty and Master Gardeners reply to queries within two business days, usually less. To ask a question, simply go to the OSU Extension website, type it in and the county where you live. Here are some questions asked by other gardeners. What’s yours?

Q: I just bought a new home in Clackamas County with a large, mature boxelder. Unfortunately, we discovered a boxelder beetle infestation since the house has been vacant for more than six months. In order for the house sale to go through, we had to bring in pest control. I would like to know what I can do in the future that is more Earth-friendly to either reduce the number of beetles or get rid of the beetles once they hatch. – Clackamas County

A: The western boxelder bug, Boisea rubrolineata, is the species we have out here. Large numbers of these bugs are usually found only in the vicinity of their host plants, which are big leaf maple trees and boxelder trees. They feed on the flowers, young seeds and sometimes on foliage, on sap seeping from wounds on branches/trunks, and on fallen seeds.

Even though they can be really numerous, they don’t do any appreciable host plant damage. In addition, they don’t bite people or pets, or damage buildings or possessions. However, because of their sheer numbers, western boxelder bugs can be considered nuisance pests. They also try to enter buildings in the fall to seek protected places to overwinter and that’s when they can be especially annoying to homeowners. Unless you are willing to cut down and replace your boxelder tree with a non-host species, it is unlikely you will substantially reduce the numbers of boxelder bugs nearby outside your home in the long term.

However, you can work to prevent them from entering your home. The PNW Insect Management Handbook suggests the following: “Prevent bug entry by repairing screens and caulking around windows and doors, screen soffit, corner trim and attic vents, etc. Sealing is best done during the summer months when the bugs are not present.

Any boxelder bugs that do manage to get indoors can be vacuumed up or captured and released outdoors.

If you find that these steps are not sufficient and you don’t want to remove your mature boxelder tree, here are the options that make use of pesticides: “Residual sprays (by a pest control operator) where bugs congregate on building sides and near the foundation may reduce entry indoors but will not eliminate the insects. A professional tree service may treat infested trees near the structure to reduce the local outdoor numbers of these bugs.”

– William Gerth, OSU Extension Master Gardener

Are inorganic compounds OK to use in my vegetable garden?

Q: Can inorganic compounds used in my vegetable garden compost pass into my produce? Two examples that I question:

• Paper products
• Mowed green grass lawn clippings from a lawn treated with weed control chemicals and inorganic fertilizer

– Wasco County

A: I would be far more concerned about the grass clippings exposed to herbicides than I would about paper. I compost a great deal of shredded office paper. One thing I value about it is its ability to absorb water and release it slowly.

A well-managed lawn is mown to remove 1/3 of the leaf blade with every mowing. Thus, you should avoid composting clippings from the first three mowings following a chemical application. But after that, there should be no problem.

As to whether fertilizers that would not be approved for organically certified products are taken up by plants, yes, they are. The reality is that of the 16 essential plant nutrients, plant roots can recognize only a single molecular form of each. The exception is nitrogen, of which roots can recognize two molecular forms.

All of this depends on the goals you have defined for your garden, and the reason that you compost. We have an extensive vegetable garden and expect to find something to eat from it every month of the year (less variety in January, more in July, of course). While we do manage the garden with minimal chemical inputs, I’m also aware that life in the 21st century means that I have plenty of chemical exposures from the environment generally. So, I’ve made peace with the idea that my body is not pristine. I just don’t go overboard with chemical exposures that I could readily avoid.

My reason for composting is to reduce the investment of gasoline into things that I want to get rid of – be they food waste, yard debris, or shredded paper.

These are personal choices. You are wise to seek science-based information as you make yours. – Linda Brewer, OSU Extension soil specialist

What are these rust stains on my birch tree?

Q: I just noticed these rust-colored stains on the bark of one of my white birch trees. The birch next to it is not discolored. Both trees are around 30 years old. Fallen leaves do not appear diseased. Can I save it? – Marion County

A: One likely cause of this discoloration is the presence of bronze birch borer in your tree. Here is a link to a guide on this insect pest.

This guide will help you know what to look for to determine if your tree has bronze birch borer and what to do about it. – Nicole Sanchez, OSU Extension horticulturist

Is there help for this wilting basil plant?

Q: We have purchased several basil plants and they all dry up. We don’t know if we are giving them too much or not enough water. They get wilted within a few days. – Deschutes County

A: The soil appears to be dry, but you can only measure water content by poking your finger in it, or getting an inexpensive water probe that will tell you. The soil needs to drain well, but be kept moist.

The other problem may be inadequate light. Here’s an Extension article on this plant. – Kris LaMar, OSU Extension Master Gardener

Tips for low-growing hedge-type plants

Q: What is a good low-growing, easy-maintenance plant or bush for a border in the front lawn along a busy road? I had arborvitae but they obstructed the view of the road, making it dangerous to get out of the driveway. – Marion County

A: I am uncertain how tall a shrub your area can safely handle, but suggest you consider one or more of the small to medium shrubs pictured in this native plant guide. – Kris LaMar, OSU Extension Master Gardener

Will slug bait kill earthworms?

Q: I recently heard that iron phosphate-based baits will kill earthworms. Is this something that you have heard about or have any information on? – Yamhill County

A: There have been some published studies about molluscicides, including Sluggo, being harmful to earthworms. They can cause loss of weight and potentially mortality when they are consumed. The article below discusses additional means of managing slugs and some suggestions for applying chemicals more safely. – Heather Stoven, OSU Extension horticulturist

Bark chips recommended for patio containers

Q: I’m a renter with a large patio. I have a variety of native shrubs growing in large cloth pots in part shade. They are pebble mulched for now but I was wondering if I should plant some ground cover with them. I’ve got fringe cup seeds, but that might be too big? Maybe a wild strawberry? Oxalis maybe? – Washington County

A: It would be helpful to know how much surface area and volume of soil is available in the containers before making recommendations. Oxalis might be a good choice (but can become a weed if not contained).

As a side note, pebble mulching does little to help plants since, unlike organic mulches, it provides no nutrient return to the plants, and only adds weight (and aesthetic appeal). You might want to consider large bark chips instead, or kill two birds (without stones) by planting a legume such as crimson clover over the winter (next year; it’s too late this year). In the spring, change it out for annuals such as violas. Here and here are more resources. – Kris LaMar, OSU Extension Master Gardener