The Yellow Farmhouse Garden

August 3, 2017

Beneficial insects in our garden

As mentioned in an earlier post on this blog, I planted a fairly large plot of buckwheat adjacent to our vegetable garden this spring. The main idea behind planting buckwheat was to provide forage primarily for honeybees and for any other pollinators that might be around to take advantage of it.

As it turns out honeybees are in the minority. When surveying the buckwheat plot, I noticed for every one honeybee I saw there were ten or twenty other pollinators. They included butterflies, small wild bees, small wasps, many kinds of beetles, flies and hoverflies.

Hoverflies are especially good to have in the garden. The adult hoverfly is a very agile flyer able to hover in one spot then zoom away, stop on a dime and hover in place again — they can even fly backwards.  They don’t have teeth or mandibles so they can’t chew or tear into things. Their mouth parts are spongy and are designed to soak up nectar and other liquids as well as picking up small particles such as pollen. That is why they’re so attracted to the buckwheat flowers.

Hoverflies have a superficial resemblance to bees.

Hoverflies have a superficial resemblance to bees.

Hoverfly larvae on the other hand are insectivores that eat small soft-bodied insects. In the garden that means mostly aphids, thrips, leafhoppers and scale. All four of these common garden pests have a stage in their lifecycle when they are soft-bodied.

After mating the adult female hoverfly buzzes around looking for a likely spot to lay her eggs, someplace where her young will have easy access to food. How does she know where the best spot is? Aphids and those other insects get all their nutrition from plant juices. They can only use part of the sugar in plant sap so they excrete the unneeded sugar as a syrupy liquid called “honeydew”. It’s the honeydew that attracts the female hoverfly: where there’s honeydew, there are insects for her young to feed on.

During the larval stage, each individual hoverfly will eat up to 400 aphids and other insects giving it the needed protein to go on to further development.

Since they are such good flyers, it’s very easy for female hoverflies to fly from the buckwheat to our vegetable garden and back again. The habitat that buckwheat provides enables the hoverfly population to grow much larger than it would otherwise. That is a good lesson about the advantages of encouraging beneficial insects instead of trying to maintain a garden in the middle of a sterile environment like a mowed lawn.

Bob

July 12, 2017

Rose sawfly emergence

If you ever grew roses you probably have seen those ugly, slug-like rose sawfly larvae eating leaves on your roses, or at least the damage they do. That’s the way we usually see them, as larvae. Rarely are the adult insects ever seen by gardeners.

Rose slugs feed on one side or the other of the leaves, usually it’s the underside. When they first hatch from the eggs and while they’re growing, the slugs are very small so they have very small mouth parts. That means they can’t take very big bites and only able to eat the softer leaf parts leaving the tough veins of the leaf.  And they only eat one surface of a leaf leaving the other side intact. This results in a characteristic “windowpane” feeding pattern. Later as the leaf parts dry, the windowpanes turn brown and fall out. It’s not unusual for an entire rose bush to be defoliated like this.

Last week, on some ‘Knock Out’ roses, I witnessed a surprising phenomenon, a swarm of rose sawfly adults. It was a frenzy of activity, hundreds of them flying in and out the the rose branches stopping only briefly to mate. They would swam all over one bush then move on to the next until they visited all nine rose bushes. The way they were flying really looked a swarm of bees or wasps. That should not be too surprising since they are are members of the insect order Hymenoptera which includes bees, ants and wasps among others.

Unfortunately, I wasn’t able to capture a video for you but I got a few photos.

The adult sawflies do not chew on buds.

The adult sawflies do not chew on buds.

 

 

Sawflies were on every part of the plant.

Sawflies were on every part of the plant.

Closeup of adult sawfly.Closeup of adult sawfly.

The entire event lasted about two hours, then they were gone, with just a few stragglers left behind. I assume they laid eggs on the rose plants during all that activity. I’m expecting a huge outbreak of rose slug larvae from them.

When all that was going on, I was thinking that I had two choices: I could spray all of those sawfly adults as they were buzzing around and destroy them right then and there; or just leave them alone to see what eventually happens. Actually, since I didn’t have any insecticide or sprayer at the time, the decision was already made.

This will be an unintended but interesting experiment. I’ll let you know how it turns out.

Bob

 

 

 

 

 

 

 

 

July 11, 2017

Cucumber seeds fail to come up

Filed under: Insects,Vegetables — bob @ 8:17 am

A couple of gardeners I know asked me why their cucumbers didn’t come up this year. Others have mentioned that their beans didn’t come up either. Was there something wrong with the seeds this year?

After inspecting a few gardens, it became apparent to me what was going on. In each case, there was a heavy infestation of striped cucumber beetles. They are voracious feeders and are always on the lookout for their preferred food, cucumber vines and related plants such as melons and other vine crops.

In those gardens, the beetles ate every plant they could find that tasted like a cucumber. The sprouts just emerging from the soil were particularly vulnerable which is why it appeared that the cucumbers didn’t come up — they ate every last bit of the tiny cucumber sprouts before the gardener knew what happened. And larger, young transplanted cucumber plants were well on their way of disappearing down the gullets of the beetles. When the vine crops were all gone, they moved over to the bean sprouts and ate those down to the ground. Even older bean plants had lots of holes in their leaves from the beetles.

Striped cucumber beetle.

Striped cucumber beetle.

Striped cucumber beetles are about a quarter of an inch long. They have bright yellow bodies with distinct black stripes running the length of their wings.

This was just the first wave of cucumber beetles, we can expect one or two more generations of beetles to show up later this season.  This generation of beetles will lay its eggs at the base of the plants in the garden. Later they will hatch, feed on plant roots for a while then pupate and emerge as adults later in the season. The next generation of beetles will feed on the underside of the leaves and even chew gouges in the fruits.

Even more important, cucumber beetles carry and will spread bacterial wilt, a serious disease of vine crops. Infected plants wilt and never recover. There is no cure for bacterial wilt once it infects a plant. It’s very disheartening to see your cucumber vines grow and begin to flower only to lose them to wilt. So it’s a good idea take care of cucumber beetles as soon as you find them. Hand picking doesn’t work because they can get away too fast. Instead, apply an insecticide labeled for cucumber beetles, most garden insecticides are effective against them.

Bob

 

 

June 18, 2017

Pruning milkweeds to attract monarch butterflies

I saw my first Monarch butterfly several days ago. I know they were here much earlier because I found a caterpillar on my milkweed plants. That means there had to be a female butterfly around before that.

It didn't take long for this caterpillar to disappear into a chrysalis.

It didn’t take long for this caterpillar to disappear into a chrysalis.

It takes around four days for a Monarch egg to hatch. The caterpillar stage lasts around a week and a half to two weeks. Since my caterpillar was almost fully grown, the female Monarch that laid his eggs arrived nearly two weeks ago. How did she sneak into the yard without me seeing her?

Most of my milkweed plants are on the verge of blooming. The plants are maturing and the leaves and stems are beginning to stiffen and get tougher in order to hold up the flowers and seed pods. Although female Monarchs will lay eggs on any milkweed, they prefer the more tender leaves toward the top of the plant.

Make your cut just above a set of leaves to stimulate secondary leaf buds to grow.

Make your cut just above a set of leaves to stimulate secondary leaf buds to grow.

A gardener I know suggested that I cut back my some of my milkweed plants to stimulate new growth and leaves. Theoretically, those new leaves would make my plants more attractive to the butteries than others in the area. I just snipped off the plant just above the existing leaves. That caused some milkweed sap to ooze out of the cut. That sap is poisonous and irritating so make sure you don’t in your eye.

This is the first time I’ve tried this with milkweeds. I’ll let you know how it turns out.

Bob

January 5, 2017

Ways insecticides work

Filed under: Insects,Pesticides — bob @ 10:42 am

Winter is a time of planning for gardeners. I decided during the deep, dark days of the dead of winter to take inventory of my fertilizers and pesticides. That got me thinking about some of the different insecticides and how they work.

Chemical insecticides have been around a long time. Fortunately, modern chemistry has eliminated the need for most of the nastiest chemicals we used to use in food products. The lead-based and arsenic-based materials used in the nineteenth and early twentieth century  were made obsolete by more sophisticated chemicals introduced into the marketplace after world war two. Take for example the organophosphates, they were the by-product of chemical warfare research done in Germany during WWII. I remember using some of those products from time to time during heavy insect outbreaks in order to save a crop. I’ll tell you one thing, they sure did the job. Unfortunately, many gardeners used them constantly and on everything. I guess they thought if it was legal and on the market it was fine to use it like that. Sometimes they even eyeballed the amount to use instead of carefully measuring it before mixing. While a few organophosphates are still on the market, most of the harsher ones are no longer available for use in the home garden.

Different insecticides work by different means. For example, the contact insecticides kill when the insect comes in contact with it, either by being directly coated by it or walking across an area on the plant that has been treated.

Stomach poisons work when an insect consumes the material and it enters into the insect’s digestive system. The biological insecticide Bacillus thuringenses  is a stomach poison. It’s commonly use in organic gardening.

Bacillus thuringiensis  was the first bacterial insecticide approve for use in home gardens.

Bacillus thuringiensis was the first bacterial insecticide approve for use in home gardens.

Some insecticides are absorbed by plants and are moved to all parts of the plant and remain inside the plant for a relatively long time. These are the systemic insecticides. They are often used on ornamental plants that are not intended to be eaten. I used systemic insecticides many years ago when I had over two hundred roses bushes to care for. The systemics work great for controlling rose pests.

The translaminar insecticides insecticides move just a short distance into the leaves and are not carried through the entire plant. Think of a leaf being constructed of a number of different layers, like a piece of  laminated plywood. A translaminar insecticide only moves into the first or second layer of the leaf. The organic pesticide spinosad is a translaminar material.

Some insecticides work by a combination of two or more of the these modes of action. Often manufactures combine insecticides in order to gain the advantage of multiple modes.

Because an insecticide can act differently on various types of plants, it’s important to closely follow the printed label and not try to extrapolate other uses on your own. This holds true for both conventional and organic insecticides.

Of course we’re not applying insecticides to our gardens right now but it’s not too early to remind ourselves of these things well before the gardening season.

Bob

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