Got agave problems? It may be this common pest.

The agave is one of my favorite plants. Nothing quite compares to its dramatic form, making it a great choice to add interest in desert landscaping. While both low water use and normally maintenance-free, the agave does succumb to an annoying insect that decimates the entire plant with little notice that there is a problem until it is too late.

The symptom of snout-nosed agave weevil damage almost looks like the plant is wilted from lack of water.

However, this is not the case. What has happened is that the weevil has chewed a hole into the center bud of the plant. While doing so, they excrete an enzyme that softens plant tissue, allowing bacteria, fungi and diseases to take hold. When the female lays her eggs, the white grubs that hatch eat the plant from the inside out. This process takes 2 to 3 months. Once you see the damage, the plant is dead and there is nothing you can do to save it. I’m not a proponent of systemic insecticides, which you may read is an option. I prefer to recommend you avoid the species of agave that is the most susceptible to snout-nose agave weevil attacks: the Century Plant. (Agave Americana, photo)

Proper plant care also reduces susceptibility to insects and diseases. With agaves, less water is more. Over-watering these plants, if it doesn’t cause roots to rot, speeds up their growth, shortening their lives. When an agave reaches maturity, it will flower and die. And despite what you may have heard, cutting off the flower stalk will not make it live longer.

If you want your plant to live a nice, long life, anywhere from 5 to 25 years (depending on the variety), monitor the water schedule carefully. For plants in the ground, water once a week in the summer, and once a month or so in the winter, depending on winter rains. Container plants in full sun will need twice that, usually twice a week in the summer and twice a month in the winter.

Alternative weed control

Yellow cast of one kind of herbicide

With all of the rains we’ve had, weeds are having a ball. Whether you are a homeowner or landscape contractor responsible for commercial landscaping, using chemical weed killers does not have to be your only choice for weed control. It is important to understand why this is important.

Are weed killers safe? In short, no, although some products insist the weed killing chemical in their sprays do not hurt humans or wildlife. Sadly, they aren’t giving you the whole picture. While the jury may still be out on the main ingredient for some, it is most definitely in when it comes to the so-called inert ingredients.

Inert chemicals in weed killing sprays are toxic. According Crystal Gammon in a June 22^nd, 2009 Environmental Health News article, inert chemicals in Roundup, a popular herbicide, are more deadly than the herbicide itself. The additive known as polyethoxylated tallowamine, is particularly poisonous to human embryonic cells. It is also toxic to cells making up the placenta and umbilical cord.

Think about this: Hundreds of thousands of gallons of Round-Up are used every day to spray common areas, roadsides, and yards. Not only does this end up in our groundwater, every time you walk outside, you, and even your pets, have the potential to pick up residual spray on shoes and paws, bringing it into your home. Traces of herbicides can be found on your floors, carpets and furniture. Your pets ingest the stuff when they lick their paws. Scary.

There are at least two products currently available to control weeds that do not harm people, pets and wildlife.

A “weed flamer” is very effective in controlling weeds, and also has the bonus of killing weed seeds before they germinate. The weed flamer works by boiling water in plant cells, causing them to burst. This is the first step to weed killing. While passing the flame over the weed, you also burn weed seeds on the ground. It is important to remember when using this tool to only use it on small, green weeds. Obviously, if you try and burn large, dead weeds you risk setting fires. This is no toy, and requires the utmost care when using, but is highly effective. It is especially useful along edges of driveways, sidewalks and in areas of landscape rock. Red Dragon currently holds the patent for a weed flamer. You can find it on their website, or in some Ace Hardware stores.

Another simple weed killer is vinegar. Although store bought vinegar with 5% acidity will work, you may have to spray more than once. However, with horticultural vinegar coming in at 20% acidity, it works much quicker. Adding a squirt of dish soap helps, too, binding the vinegar to the leaves. Dish soap also acts like tiny magnifying glasses, intensifying the sun’s rays and burning the leaves ever more. Comparing the price of chemical weed killer to a gallon of horticultural vinegar will also sell you on the idea even if you don’t care about toxic chemicals in your yard. Horticultural vinegar is available on Amazon.

Although it sounds very old-fashioned, a stirrup hoe is a very effective way to keep weeds under control. This hoe, shaped like a stirrup, slips under weeds disturbing a minimal amount of soil. This is important so you don’t accidentally plant more seeds to come up later while hoeing. As with any weed control, getting weeds out when they are small is the key to less effort.

Another option is to “solarize” your soil. In late spring, cover a weedy area with CLEAR 5 mil plastic. Secure the edges with weights, or bury edges with dirt. That’s it! Leave the cover there for at least 2 months. This will kill all weeds and weed seeds; however, keep in mind it will also kill beneficial insects, soil microbes…everything. This is important if you are solarizing a garden area.

Some folks swear by pre-emergents, as they are intended to keep weeds from germinating in the first place. Aside from the high price, it is just another chemical added to our groundwater after a heavy rain. An alternative to chemical pre-emergents is corn gluten meal. Non-toxic and safe, corn gluten inhibits weed growth and will not poison your yard in the process. As a side note, it is thought that using pre-emergents are directly related to increase populations of mites. Another good reason to remember how closely everything in the world is related. Kill one thing, affect another. And not necessarily in a good way.

We all have a responsibility to the health of our planet, and if going green is high on your list, put away those poisons and do the right thing when controlling weeds. Your children’s children will thank you.

A primer on biological insect controls

Bt works wonders on the tomato hornworm

There are a number of products on the market that advertise they are biological insect controllers, and it is important to understand how some of these products work. Just because a product is made from natural ingredients, does not mean it is necessarily non-toxic or safe for the environment. 

For an organic garden, you need to keep in mind what your priorities are. If you do not want to use any pesticides what-so-ever, then handpicking bugs and barriers (such as floating row covers) may be your best options. There may come a point when you need some help, and there are products out there that can do that for you.

BACILLUS THURINGIENSIS

I am a big proponent of Bt (Bacillus thuringiensis and its counterparts) as it is totally biodegradable, non-toxic to humans, pets, fish and birds. It affects the digestive system of caterpillars when they eat the treated plant. Although it will also kill caterpillars of butterflies, they rarely feed on your vegetable garden plants. To be safe, don’t spray ornamental flowers that normally attract butterflies. Another reason I consider Bt a really good product is that you can use it as a preventative. It is a “non-contact” insect killer, which means the insects don’t have to be present and you don’t have to spray the actual bug. Bt can be used on products sold as organic.

ROTENONE

Although this insecticide is made from natural ingredients, is biodegradable, but it is not non-toxic. It is a contact insecticide (you have to actually spray the insect to kill it) and is not allowed to be used on produce to be sold as organic.

PYRETHRUM

This too is a synthetic insecticide even though it is made from Chrysanthemums.  It is highly toxic to fish and honey bees. It is a contact insecticide, and considered to have a low toxicity to humans. 

SAFER INSECTICIDAL SOAP

This product is made from natural oils and animal fats and is effective against aphids, scale and other soft bodied insects. It is considered non-toxic to humans and approved for use on organic produce. The downside is if you apply it in really hot weather in a sunny location you could damage your plants. 

Those pesky and destructive whiteflies: what's a gardener to do?

If you see a cloud of white insects flying around your vegetable garden, unfortunately this means you have the dreaded whitefly. They are especially attracted to lettuce, and are a huge problem for Arizona lettuce growers in the winter. They also attack tomatoes, peppers, cabbage and the foliage of carrots, and have a liking to herbs like parsley as well. They are a sucking insect, and can kill the plant within a short amount of time. Since they love dry, dusty conditions, the desert is a perfect climate.

They are dreaded because they multiple incredibly fast and are very difficult to control naturally. Although some experts recommend using beneficial insects for a natural control, this method is not particularly successful in the desert environment because conditions are just not that favorable for many beneficial insects to stick around and do any good. You can try sticky traps, which need replacing as they fill up with insects. Barriers such as floating row covers work, provided you get them on before the whitefly sets eggs on your plants, but this does not work once temperatures rise into the mid to upper 80’s because it just plain gets too hot under there.

Since whiteflies love dry, dusty conditions, your best bet is to hose off plants often. If you have one plant they particularly like, it may be worth it to sacrifice that one plant to reduce infestation of the others.

Alternative weed killers

With all the rains we've had this summer, no doubt weeds are rampant. If your autopilot is on when you go to buy herbicide, turn it off and consider these alternatives instead.

Store bought cider vinegar is amazing stuff. Mix a squirt of dish soap to a gallon of vinegar to help it stick to leaves. This is acid, and will burn the leaves. You may have to spray difficult to kill weeds more than once (like Bermuda grass). There is also a more potent vinegar available. Horticultural Vinegar (at 20% acidity), available at Amazon.com. This usually works with one spray, and will certainly save you money over buying expensive and dangerous chemical herbicides. To apply, spray on small weeds (always best to get ‘em really small no matter what you use). Avoid spraying vinegar where you want plants to grow as it can alter the pH of the soil.

The Weed Dragon (brand name) works great on small GREEN weeds, especially around sidewalks, driveways and patios. It is available online and in some Ace Hardware stores. To kill weeds, you only need to run the flame over the weed until it wilts. The intent is not to actually burn them, just to burst the water in plant cells. The bonus is you will also kill weed seeds on the ground!

And then there is the good old fashioned Hula-ho, which works by slipping under the weed and minimally disturbing the soil. This hoe is better than the standard hoe for this reason, since the more soil you disturb, the more you bury weed seeds.

If you’ve got a particularly stubborn weed infested spot and want to kill off everything, cover the area with heavy duty CLEAR 4 or 5 mil plastic. Secure the edges and leave there for the entire summer. I guarantee nothing will be left by the end of August, including soil borne diseases. However, this will also kill beneficial insects, just so you know.

So before you buy chemical weed killer think about the cost to the environment and your budget. Alternatives are actually less expensive, and safer for you, your family, pets, and the planet.

Just what are biological insect controls, anyway?

There are a number of products on the market that advertise they are biological insect controllers, and it is important to understand how some of these products work. Just because a product is made from natural ingredients does not mean it is necessarily non-toxic or safe for the environment. 

For an organic garden, you need to keep in mind what your priorities are. If you do not want to use any pesticides what-so-ever, then handpicking bugs and barriers (such as floating row covers) may be your main options. There may come a point when you need some help, and there are products out there that can do that for you.

BACILLUS THURINGIENSIS

I am a big proponent of Bt (Bacillus thuringiensis and it’s counterparts) as it is totally biodegradable, non-toxic to humans, pets, fish, birds. It affects the digestive system of caterpillars when they eat the treated plant. Although it will also kill caterpillars of butterflies, they rarely eat the type of vegetable plant of concern. To be safe, don’t spray ornamental flowers that normally attract butterflies. Another reason I consider Bt a really good product is that you spray the plant that is being attacked, not by contact on each individual insect.

ROTENONE

Although this insecticide is made from natural ingredients and is biodegradable, it is not non-toxic. It is a contact insecticide (you have to actually spray the insect itself to work) and is not allowed to be used on produce to be sold as organic.

PYRETHRUM

This too is a synthetic insecticide made from Chrysanthemums. It is highly toxic to fish and honey bees. It is a contact insecticide, and considered to have a low toxicity to humans. 

SAFER INSECTICIDAL SOAP

This product is made from natural oils and animal fats and is effective against aphids, scale and other soft bodied insects. It is considered non-toxic to humans and approved for use on organic produce. The downside is if you apply it in really hot weather in a sunny location you could damage your plants.