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Sunday, April 16, 2017

Aphids Versus Soap and Water: a Never Ending Battle

Q. First year with my apricot and I spray with soapy water to control aphids. Every day I check leaves but they never stop. Is this good to spray to use?
Adult aphid. These are about the size of a large grain of salt. There are about 200 different aphid types and most of them only prefer a specific plant. A few of them are general feeders but most are very specific to what they like to eat.

A. Soap sprays are good to make an immediate kill of an insect and don't expect them to reestablish themselves after you're finished. The problem with aphids this time of year is that they will come back, usually in just a few days, after soap sprays have been applied.

Aphid feeding on plum leaves can cause the leaves to curl over time, thus protecting them from sprays.

Dr. Bronner'sOrganic Castile Liquid Soap Almond
I am not a big fan of soap and water sprays for insect control
but if you decide to make your own please use a
Castile type soap free of any scents or lotions.

Use a decent soap

The good thing about soap sprays is that they are very safe for humans, pets and other large animals. The bad thing about soap sprays is they do not discriminate between good bugs and bad bugs. If it's a bug and you spray it, it will die, good or bad.

Soap and water is a killer

            The second negative about soap sprays is they have no residual. That means that soap sprays leave nothing behind to kill bugs after the spraying is done. They have no residual. You are the residual. Soap sprays rely on you, the applicator, re-spraying when needed.
            You must be knowledgeable enough to spray the bad bugs but not the good bugs. It also requires that you find most, or all of the bad bugs when you spray. If you don't, they reestablish in a few days and you must spray them again, and continue to spray them as long as you need to, over and over, until the problem is gone.

More about aphids

            Aphids began infesting new growth, making more babies, as soon as the leaves popped out. Females that survived and made it through the winter on landscape plants had wings. They flew to the soft, succulent, sugary new growth and started laying eggs as soon as it came out and as fast as they could. What a good mother!
Ladybird beetle with aphid

            Mature female aphids that make it through the winter have wings. They can fly short distances to the new growth. These mother aphids never need a male aphid to produce their young and they produce young very rapidly.
Aphids on developing pomegranate fruit. The fruit tissue is pretty hard for them to feed through but they will certainly like the much softer leaves and flower petals

            It just so happens that many ants like the sugary residue that aphids leave behind when they are feeding. Those ants which use sugar for raising their young absolutely love aphids and move them to different locations on plants so that they can "farm" them. Controlling ants colonies also helps to control aphid populations.

Chemical controls

            Moving up the line of toxicity to aphids and comparing it to the toxicity toward humans and the environment, next try some of the oils such as neem oil, rosemary oil, mint etc. next moved to the so-called "organic" or "natural" sprays like pyrethrins.

            Pyrethrins are made from a type of chrysanthemum. If you feel safe with pyrethrins, you may choose to move to the synthetic pyrethrins which are everywhere in garden stores but are not considered "natural" or organic. They leave behind a residual and continue to kill insects after they have been sprayed.

Getting Rid of Annual Bluegrass or Poa

Q. So how do we eradicate poa Anna?
Annual bluegrass in a hybrid bermudagrass home lawn. Notice the discoloration by the Poa when the bermudagrass is actively growing.
A. Poa annua or annual bluegrass is easy to control in landscapes but extremely difficult to control in most lawns. If this is in a lawn such as a cool season grass like tall fescue, Kentucky bluegrass or perennial ryegrass it is very difficult to control. This is the worst situation. If it is growing in 100% Bermuda grass it is much easier to control. If it is growing in a landscape, around trees and shrubs, it is easy to control with mulch.
Annual bluegrass persisting in hybrid bermudagrass on a golf course during the winter months. Annual bluegrass stays green during the winter in colder climates while the bermudagrass becomes dormant, dies, or turns brown.

Annual bluegrass has evolved. 

This grass is very different from what it used to be 50 years ago in many locations. In the old weed control manuals 30, 40 and 50 years ago they all said the same thing. It is a winter annual, the seed germinating toward the end of summer, flowering or producing seed heads during the fall and winter months and the seed laying dormant or sleeping through the summer. It repeats this cycle over and over. Annual bluegrass is a very poor competitor with mulch but it is an excellent competitor when it grows among other grasses. When I went to school, this is what I learned annual bluegrass was.
Annual bluegrass seedhead.
Annual bluegrass has evolved in certain landscapes and climates where it now persists as a perennial in warm climates and will produce seed at different times of the fall and winter months. This is very apparent on many golf courses and a nightmare for golf course superintendents. This grass can be mowed very short, 1/4 inch or less, so mowing it out will not happen. It loves environments where the grass is mowed short and kept wet. It is also very strong in soil environments that are compacted without much airspace between soil particles. I would compare it, from an evolutionary standpoint, to the cockroach.

Controlling it in cool season lawns.

When it grows in cool season lawns, the usual methods of control are pre-emergent weed killers or herbicides. If this is a home lawn, you will have an advantage because you can apply these pre-emergent herbicides several times during the year and that's what you will probably have to do, starting in late summer and through next spring. 

Look at the pre-emergent herbicides available to you and select one that can be applied to a lawn and says that it controls annual bluegrass. Make the first application of pre-emergent herbicide in the middle of late summer. In the hot, southern Nevada climate this would be about mid July or early August. Read the label and it will tell you when to make a second application and how much to apply.

Image result for scotts poa control
In the past, Scotts has made excellent products for weed control in lawns.
Pre-emergent herbicides slowly degrade over time. You want to apply this herbicide a short time after its peak control period. It will tell you on the label how many weeks to wait after this first application before the second one is made. There is some residual from the first application so you will make the second application at some rate less than the first application. I repeat, the label will tell you how much to apply and how long to wait before applying the second application. Continue this cycle of applying, waiting and repeating all winter long (if the label allows it) and into early spring. That should kill most of the seed. If you see some young plants that were missed by the herbicide application (they are usually lighter green and grow faster than the surrounding grass) then pull them by hand. They will pull out easily because they have very shallow roots.

Annual bluegrass biotype producing short rhizomes,
adapting like a cockroach to a changing environment.
If this is a bermudagrass lawn, kill the annual bluegrass during the winter months after the bermudagrass has turned totally brown (dormant). Do not overseed this bermudagrass lawn with a winter lawn this year, and possibly the next year, until you get control of the bluegrass. By the way, this is also an excellent way to control other weeds including tall fescue growing in a bermudagrass lawn. After the bermudagrass lawn has turned all brown, and you have mowed it, spray the lawn and the annual bluegrass in it with Roundup herbicide. The Roundup will kill the annual bluegrass because it stays green during the winter months (cool season grass) but the bermudagrass is dead above ground. The Roundup will have little to no effect on the dormant bermudagrass.

This is a core aerator that punches holes in the lawn.
Management methods that help to suppress annual bluegrass are aeration (punching holes in the lawn with a core aerator) and waiting longer between irrigations during the late summer, fall and winter
months. Aeration helps open the soil which annual bluegrass does not like. As I said before, annual bluegrass likes it wet because it has a very shallow root system. Waiting longer between irrigations helps keep the soil dry and minimizes its invasion.

Preventing annual bluegrass from entering your landscape and lawn should be done in the future. The seed is transported to the landscape on shoes that walk across the seed heads during the fall and winter months. If a landscape has annual bluegrass and people walk across the seed heads and then walk into your landscape, they will transport the seed and that's where it starts. It is also transported to lawns in the same way as well as the lawnmower. If a lawnmower was used on a lawn that had annual bluegrass in it and it was seeding, I guarantee
100% that this seed will be brought into your lawn if it's the next lawn that is mowed. Mowers should be cleaned thoroughly between lawns to slow the spread of weed seeds such as annual bluegrass and diseases.