Category Archives: pest control

Mystery Beetles on Arugula

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Harlequin bug on arugula – telltale brown spots where it is has been feeding

The beetle that has infested this arugula (which is beyond saving, because of the spotting on the leaves), is yellow with dots on its back.  It looks like the harlequin bug, which especially likes the cruciferous crops:  cabbage family, mustard, turnip and radish.  However, it has been known to munch on tomatoes, potatoes, eggplant, okra, and beans.

            As you can see by the picture, there are brown spots on the leaves where the bug has sucked juices, which causes that portion of the leaf to die and turn brown.  The life-cycle of the bug can be as short as 48 days, and so can have a number of generations go from egg to maturity during a growing season. 

            There are several control strategies.  Hand-picking is first, but when there is a prolific infestation, it is difficult to pick all those little critters than can fly.  A trap crop of turnip, mustard, or kale in the late spring or early fall could be used to attract them, but then the trap crop must be destroyed.

            An organic spray can be made from insecticidal soap (which penetrates the hard shells) and neem oil.  However, this is a control that must contact the bug or eggs, and is best applied in the early morning.

            Prevention is perhaps the best method of control.  Strong plants will tend to deter the bugs.  This means encouraging deep roots through thorough watering.  Also, the plants attractive to the harlequin bug are heavy calcium feeders.  So, adding ground eggshells when planting may help prevent infestation.

            Another preventive measure is to use row cover on the crops that don’t need pollination to grow.  That means, the leafy crops like cabbage, arugula, mustard, kale, etc. 

            Companion planting can help too.  Plants like basil, garlic, rosemary and sage, as well as chrysanthemum (with its natural pyrethrins) are strong-scented and mask the odors of the bug-targets. These companions can either be boundary plants or intermixed with the bug-targets.

            Parasitoid wasps (attracted to yarrow, caraway and fennel, as well as other herbs with umbrella-like blooms) can be effective against the harlequin.  If you purchase the wasps, be warned not to choose the braconid or trichogramma wasps, because they prefer soft-bodied pests rather than the hard-shelled harlequin.

References:

harlequin bug – Murgantia histrionica (Hahn) (ufl.edu)

12 Organic Ways to Control Harlequin Bugs – Hobby Farms

Barbara Pleasant, The Gardener’s Bug Book, Storey Publishing, 1994.

Tips and Tricks – Garden Pests

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Following are some things I recommend in my classes.  I like to use non-toxic and easy-to-use solutions to pests.

 Borage planted with tomatoes repels worms

Marigolds planted with tomatoes repels root knot nematodes

Nasturtiums and tansy are reported to deter squash bugs

Some have luck with planting icicle radishes around the squash plants to deter those pesky squash bugs.

Plant lots of rosemary for mosquito control; also yarrow, lavender and mint.

If tomato plants are turning yellow, it may mean lack of magnesium. Dissolve 2 TB epsom salts in a gallon of water, put in a hand sprayer and spray the leaves (top and bottom) of tomatoes – peppers, too. About a week later, if the tomatoes are still not responding, mix the same amount and use to water the tomatoes/peppers.

To repel pests eating plants (e.g., basil, sage, peppers), boil red pepper flakes in water. Strain into a spray bottle and add about 1-2 tsp of dish soap (preferably 7th Generation or Ivory Soap). Shake and spray on the plant leaves.

For fire ants, boil orange peels in water with some whole cloves. Strain into a jar and add the same amount of water.  Pour on the mound. May have to repeat after about a week. It makes the ants go away.

 

Hornworms and Companion Planting in the Garden

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In a gardening class this weekend, the discussion turned to growing tomatoes and the prevalence of the tomato hornworm.  Truth be told, I have not, in the last two decades seen a hornworm on my tomatoes.  Maybe I just don’t see them, but I sure don’t see any leaves eaten either.

Hornworm

Whitney Cranshaw, Colorado State University, Bugwood.org

 

Here’s what I do to avoid them (and other pests).

Borage, a lovely purple flowered herb, can be grown with the tomato plants and keeps hornworms away.  I also plant marigolds in the vicinity (to ward off root knot nematodes that can devastate tomatoes), and basil.  Not only do the tomatoes have company, but I get lovely flowers, cucumber-tasting borage leaves for salads, and fragrant basil.

I also don’t plant tomatoes in the same garden space two years in a row.   In fact, I’m on a 3-4 year rotation.

The practice of companion planting can produce more food for the space than just planting recommended spacing of mono-crops.

I’m a big fan of companion planting over and above any pest control benefits. Companion plants are those that help each other, and sometimes even increase yields for each other.  Friends helping friends.

A good companion planting with strawberries is spinach.  They both like more acidic soil.

Carrots go well, when planted among tomatoes late in the summer/early in the fall, when the tomatoes shade them from the hot sun, yet let them get a start.  The carrots use the under-surface growing horizon and are ready to burst forth when the tomatoes are done for the season.  Two crops from the same space.

Potatoes and beans (particularly bush beans) go well together.  They protect each other from Colorado potato beetle and Mexican bean beetle.

Okra and peppers do well together, especially if the okra is used as a windbreak for the peppers.

And if you’re growing lettuce and have problems with rabbits helping themselves, I’m told that onions planted with the lettuce will repel the rabbits.

[NOTE: A good read for companion planting is Carrots Love Tomatoes.  Look for the full citation under the Resources tab on this website.]

And while I’m on the subject….how about planting lots of rosemary?  It helps repel mosquitoes!  I advocate rosemary plantings around the deck or patio.

Other repellents or remedies include pepper flakes and orange peels.

To repel pests eating plants (e.g., basil, sage, peppers), boil red pepper flakes in water. Strain into a spray bottle and add about 1-2 tsp of dish soap (preferably 7th Generation or Ivory Soap). Shake and spray on the plant leaves.

For fire ants, boil orange peels in water with some whole cloves.  Strain into a jar and add the same amount of water.  Pour on the mound. May have to repeat after about a week. It makes the ants go away.