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Insect-devouring nematodes can be used to control grubs

Q: Why isn’t milky spore bacterium recommended here for grub control? I thought we had Japanese beetles and they were the same as all the other June beetles and grubs eating the roots of our plants. I am trying to formulate a better program so that I’m not just shooting chemicals every time I have a problem.

A: I don’t believe we have Japanese beetles (Popillia japonica) in Nevada. The last time I asked the Nevada Department of Agriculture, we didn’t have any in the state. Call the NDA Las Vegas number and ask if there are any in the state as of this year.

If we have Japanese beetles here, milky spore products would be effective in controlling them. Otherwise, I tell people not to waste their money in applying this product to our soils if it only controls one type of insect.

There are other natural products that you can apply for controlling grubs of June beetles, including insect-devouring (but plant-friendly) nematodes from places like Arbico Organics on the internet. These nematodes are living so they must be refrigerated and applied to cool wet soils in the spring or they won’t survive.

All soil grubs are not the same. We have several different kinds in Southern Nevada that mature into other kinds of June-type beetles like the green metallica June beetle (Continus nitida), ten-lined June beetle (Polyphylla decemlimineata), grubs in lawns that mature into a June beetle and the common June beetle (Phyllophaga hirtiventris). I know they are here because I have experienced each of them.

Many of these so-called natural controls are specific to a certain pest or grub. It doesn’t hurt plants or other beneficial insects to apply these nematodes to your landscape if you had grub problems in the past. They won’t hurt anything.

But without a real entomologist identifying your specific grubs, it would be impossible to know which pest it is. A general insect killer, like a store-bought insecticide applied as a soil drench, is usually the answer to total control unless you want to see if a natural pest control product works in your particular situation.

Q: Should I be doing anything to my grapes right now?

A: Yes, all grapes need to be thinned. This is done when the individual grape berries are about the size of peas. This occurs starting in about May or June depending on the kind of grape and when it flowers.

We grow two basic kinds of grapes: those for the table or desert grapes and wine grapes for wine, juice or jelly. We thin grapes just like we thin peaches and for many of the same reasons.

We either remove fruit so the remaining berries get larger (desert grapes), or we remove fruit to improve the flavors in the remaining berries (wine or making juice). In the case of wine or juice grapes, we don’t care about the size of the berries as much because they are crushed for the juice or grape must.

The first step is to remove smaller grape bunches that are not wanted. This can be difficult to do for the tender-hearted who want to keep everything the plant produces. How many of these small bunches are removed depends on how vigorously the plant is growing.

If it’s a very vigorous vine, leave about one large bunch for 8 to 12 inches of production. Basically, you’re spacing the bunches of grapes farther apart and bringing the grape production into balance with its growth to accomplish what you want (bigger versus more flavorful berries).

Soon after the small bunches are removed, each individual bunch is reduced in size by pinching or removing the bottom third of a bunch. This second round of thinning is done to further increase the size of the berries. Pinching is usually not done to wine, juice or jelly grapes.

Pinch with your fingers when the bunches and berries are tiny rather than cutting with shears or scissors. If the individual berries are still too small at harvest time for your liking, then next year be more aggressive in your thinning.

Q: I have a lot of fruit flies swarming in one part of my yard. How do I control them?

A: These are probably not fruit flies but gnats or midges. These adult fliers live about 10 days, so they are continuously reproducing. It takes about two weeks to make the fliers, or the mature sexual stage, so from beginning to end in warm weather they last about four weeks.

They feed on decomposing mulch, grass clippings or anything small and organic that is rotting in the soil. They are attracted to anything rotting so yeasty smells are attractive.

Most of their time is spent in the soil. They breed and grow in soil and mulch that is kept continually wet because of frequent irrigation or shade. This can be the same with fungus gnats and houseplants.

The most traditional and sustainable way to eliminate fungus gnats is to water less often and dry out the area. It’s true they can be repelled by burning citronella and attracted to anything decomposing.

To get rid of them, dry out the area and remove their food source. Citronella candles can be used to repel them if they are a nuisance. If this doesn’t work, then just about any insecticide kills them, but they will be back unless the area dries out, the food is gone or it turns cold.

Q: I am trying to grow an African bird of paradise plant on my patio. It likes it there and produces a lot of leaves but no flowers. I really like this plant’s colorful flowers, but it burns up in the sun. I decided this bird of paradise must be a male and that’s why it doesn’t produce any flowers. Any help is appreciated.

A: First off, please recognize this is a tropical plant and not a desert plant. Growing it in the Mojave Desert has its own set of climate-related problems.

This plant will not like the high temperatures of the Mojave Desert, its low humidity and intense sunlight, strong winds and cold winter temperatures. You must really love this plant to grow it here and spend a lot of time caring for it.

Tropical plants, in general, prefer to grow in organic soils more than soils without organics, and they grow best in soils low in alkalinity. Also, recognize that all flowering plants need at least six hours of strong sunlight to produce flowers.

If flowering plants do not get enough light intensity for a long enough period of time, they won’t produce flowers. At lower light intensities they can produce wonderful leaves but no flowers.

African bird of paradise is monoecious, which means there are no boy or girl plants. Each plant is a mixture of both, so flowering doesn’t depend on the sex of the plant.

But flowering is triggered by the amount of light it gets and its quality. It’s best if it can get about six hours of full sunlight starting early in the morning for as long as possible. Six hours of full sun is about the minimum needed for this plant to flower. My guess is that your patio does not allow enough light for flowering.

Find or construct a space that provides early morning sun for as long as possible and shade when it gets hot, use soil with about 30 percent compost in it, and the plant will start flowering. But it needs more sunlight than it’s getting on your patio.

Q: Several of my younger barrel cacti I moved three years ago from Yucca Valley are looking sick. The green skin under the thorns is now turning brown. A small one I purchased died due to too much watering. So I bought two more and they looked good until the past few months. I did have a tree that provided them shade until I had to cut it down.

A: Barrel cactuses are native to North and South America, so they are desert plants. As in most desert plants, they develop rotting diseases when watered too often. If they are watered frequently their roots must dry out or there will be internal rotting spreading from the roots and basal crown.

In the middle of summer, I water native cactuses not more often than every three weeks if the soil drains water and I want to push new growth. I water once a month to every six weeks if I want to maintain their size.

Enough water is applied to wet the soil to a depth of about 12 to 18 inches, then the soil is allowed to dry until the next irrigation. The cactus will visibly swell with the water it contains. It uses this water and decreases in size when the soil is dry.

After digging them in the spring or taking them from the soil, allow the roots to dry for about three days in the shade before planting. Plant them in soil amended with manure or compost — about 10 percent (one shovel full for nine of soil).

Plant them the same depth as they were growing before. No deeper or they will rot.

What causes them to rot is not allowing the roots to heal after they are dug and watering too often.

Bob Morris is a horticulture expert and professor emeritus of UNLV. Visit his blog at xtremehorticulture.blogspot.com. Send questions to Extremehort@aol.com.

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