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. 

Is your soil sick?

There are two soil born diseases that are a problem in the southwest.  Verticillium wilt and Fusarium wilt both can decimate tomato plants seemingly overnight. These diseases also affect peppers, eggplants and potatoes.

With Verticillium wilt, you will see leaves turn yellow and die without wilting, or drop prematurely with shoot tips wilting slightly during the day. As the disease progresses, the leaves may curl up at the margin but remain alive for a short time. There is no cure, so you must choose resistant varieties. I’ve had decent luck with a preventive soil treatment called “Root Guardian” available from Gardens Alive! It doesn’t always work, as I still may lose a few plants, but it must be doing something because the rest of the plants are doing fine.

Fusarium wilt starts out with leaf yellowing at the bottom of the plant working its way up.  The yellow leaves wilt before they die, followed by the entire plant.  Again there is no cure, but “Root Guardian”, as mentioned above, helps. Fusarium wilt is more common in the southwest than Verticillium.

Keep in mind that these diseases are inevitable and it is important to rotate your crops (do not plant tomatoes in the same place every year, in fact every 3 years is best) and buy varieties that are resistant.

A last resort option is to “solarize” your soil. This only works in hot, sunny climates. In late spring, cover the infected 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 soil diseases, insects and eggs, weeds and weed seeds; however, keep in mind it will also kill beneficial insects, soil microbes…everything. Your soil will be dead, but it will be free of diseases. After you have solarized your soil, you will need to introduce lots of compost and earthworm castings to bring it back to life.

Yes! You can grow tomatoes in the desert

Growing tomatoes in the desert are worth the effort!  They do take a lot of TLC, but it the end results are very gratifying.

The most important thing to keep in mind, aside from good soil, is the variety.  Many species sold in nurseries do not do well in the desert.  I have had excellent success with Early Girl, Celebrity and Heatwave (for slicing tomatoes) and Viva and Roma (for paste tomatoes).  Cherry and grape tomatoes also do well here, as do yellow tomatoes.  Be sure the varieties are disease resistant (against verticillium wilt and fusarium wilt) which will be identified on the plant tag or seed packet.  These are viral soil diseases that affect mainly tomatoes.

I prefer to start my plants from seeds since my plot is quite large.  A smaller plot with room for only a dozen or so plants would not be too expensive if you bought 6 packs or 4” pots.

You aren’t the only one that will enjoy tomatoes-birds think they are just great too, so unless you have a completely caged in enclosure, you will need to cover the plants securely with bird netting.  Birds are pretty tenacious, so make sure the bottom of the netting is secured with rocks, metal pins, or in my case, metal T-posts.  Birds will check the edges regularly, so you will need to as well.

Tomatoes also prefer afternoon shade.  If your garden plot is in full sun, then you will need to provide shade by building a structure to hold shade cloth (minimum 30%) over the plants.  I use my tomato cages to support the shade cloth (placed over bird netting, of course).  Be sure to stake the cages with rebar and wire so they don’t blow over.

Soil diseases are a big problem for tomatoes, but fortunately there are few pests.  The one that will cause you the most trouble is the tomato hornworm.  Once you see one of these, you will do anything to never see another.  They can get quite large if you let them, growing to several inches long and over 1/2” wide.  They are green with ‘horns’ and blend in perfectly with the green leaves of the plants.  You will recognize their damage immediately.  Seemingly overnight there will be leaves missing on the tops of the plants, and tiny brown droppings on the lower leaves.  You can hand pick them, but I prefer to use Bacillus thuringiensis (Bt), a non-toxic bioinsecticide the USDA has designated safe for use on organic produce.

Make sure you don’t plant your seedlings too close together, or you will have fruit that won’t ripen.  One side will be forever green while the other side turns red.  Be prepared for some varieties to get 4’ tall and 3’ wide, especially Roma, Viva, Celebrity and cherry tomatoes.  Allow at least 3’ or more between these varieties.