Hunt County Master GardenersTexas A&M AgriLife Extension Service

Squash Bugs

by

Squash Bugs by Stephanie Suesan Smith, Ph.D.

Squash bugs are some of the most frustrating pests in the home garden.  They feast on a wide array of plants in the curcubit family and can do some pretty serious damage to them.  They pierce the plants and suck out the sap, causing the plants to wilt or even die.  They are also hard to kill.  They can be controlled, though, with a little effort.

To control squash bugs, it helps to understand their life cycle.  Adult squash bugs are tiny, 5/8ths of an inch long, and winged with a grayish brown color.  The edges of the abdomen and the underside of the insect have orange to orange-brown stripes.

Squash bug eggs are really small but are laid in large groups or clusters that are easy to see.  Eggs are reddish in color and are usually laid on the underside of the leaves in the spring.  They hatch out into nymphs in about one to two weeks.  Nymphs are wingless, spiderlike, and often covered by a white powder.  They range in color from mottled white to greenish gray and have black legs.  Later, they begin to turn dark brown and resemble adults.  After molting several times into increasingly larger nymphs, they become adults.  The whole process from egg to adult takes four to six weeks.

An important cultural control is sanitation in the garden.  Remove old curcubit plants as soon as they stop producing and compost them.  Remove garden debris that may allow squash bugs to hide under it, such as boards.  At the end of the gardening season, remove all mulch and compost it or till it under in place to remove overwintering sites for the adult squash bugs. During the gardening season, regularly check under the leaves of curcubits and remove egg masses as soon as they are deposited.

If cultural controls do not suffice to keep squash bugs in check, then you will have to move to chemical controls.  The first line of chemical control is horticultural oils such as neem oil.  You must thoroughly spray the plant, reaching the undersides of each leaf and the crowns of each stem.  The horticultural oils are most effective on nymphs. You can use more toxic chemicals such as permethrin or carbaryl, but these kill beneficial insects and bees and are not really more effective than using the horticultural oils and hand picking the adults off the plants.  When you pick the adults off the plants, drop them in a jar of soapy water to kill them.

Squash Bugs

by

If you have cucumbers, squash, pumpkins, or melons, you have likely encountered squash bugs on your plants.  These flat, large insects are about 5/8 inch long and 1/3 inch wide.  They are usually dark brown to dark gray and have a diamond shaped shield on their shoulders.  Their abdomens protrude and are typically orange and brown striped.

The eggs of the squash bug are oval, small, and yellowish to bronze.  The nymphs, or babies, go through five stages of growth, or instars, and are green when born.  They gradually get darker as they mature.

Squash bugs pierce the leaves of your plants and suck the juice out of them.  This causes yellow spots that eventually die and turn brown.  It also deprives the plant of some of its water and nutrients, which can cause the plant to wilt.  Young plants may die from a heavy infestation of squash bugs.  Older plants are better able to tolerate the damage, but can also die if the infestation is very heavy.

Squash bugs can be controlled with cultural, physical, and insecticidal methods.  Cultural methods refer to keeping your plants as healthy as possible so that they can repel or survive an attack by squash bugs.   Physical refers to removing the nymphs and adults and dropping them in a pan of soapy water.  This kills the bugs.   This is particularly effective if only a few plants are effected or you have only a light infestation.

Placing a piece of cardboard in the rows between squash plants can act as a trap for the squash bugs.  They will hide under the cardboard at night and can be destroyed early in the morning.  Removing plant debris and other items squash bugs can hid in at night will help keep them to a minimum, as well.

Finally, if you cannot get rid of the squash bugs and they are inflicting significant damage on the plants, you can spray to control the bugs.  Squash bugs found early in the spring or summer need to be managed if there are a lot of them.  Squash bugs found late in the summer or fall have finished feeding and do not need to be controlled.

The best time to apply the insecticide is early in the morning or late in the evening, when bees and other beneficial insects are not active.  It is important to cover the undersides of the leaves with the insecticide, as that is where the bugs congregate.

Effective sprays for squash bugs are ones that contain the ingredients carbaryl, permethrin, bifenthrin, or esfenvalerate.  Be sure you read all package labels and only use the insecticide on plants mentioned on the label.

Squash Bugs

by

Squash Bugs by PJ LaRue Smith

A Texas vegetable garden usually contains several types of cucurbits – cucumber, squash/zucchini, cantaloupe, watermelon, pumpkin, and assorted gourds to name but a few.  Often-heard amongst gardeners in late spring/early summer is frustration over the “sudden” death that has befallen their squash plants.  In a row of plants, one will die, seemingly overnight, while the rest will carry on for a week or so before another suffers the same fate.

Many gardeners just attribute this to the hotter, drier weather, lack of rain, or simply a poor choice of variety.  While any of these might be responsible for plant death, the “squash bug” (Anasa tristis) is the likely culprit, especially in plants that seem to be thriving one day and wilted/dying the next. (Squash bugs enjoy munching on all members of the cucurbit family, however, their favorite meal is the squash plant – hence the name.)

Adult squash bugs are brownish gray to dark gray bugs about 5/8 inch long and will be the first of their kind to be seen.  Emerging in the spring, they mate as the plants begin to vine, laying yellowish to bronze-brown eggs in clusters on the underside of leaves, often in vine angles.  (Egg laying is not limited to just their host plant, as eggs can be found on tomatoes and even t-posts.)   When first hatched, nymphs have a green abdomen with crimson head, thorax, legs and antennae, later becoming grayish-white with nearly black legs and antennae.

Squash bug eggs hatch in one to two weeks, with nymphs feeding in clusters on the stems of the plant.  In six to eight weeks, they transform into adults which will continue to feed through the fall. Damage to the plants will show as a rapid wilting of the leaves which will then blacken, become crisp and dry.

Squash bug damage can be particularly detrimental to young, immature plants.  Many entomologists believe this is due to a highly toxic saliva that is secreted into the plant during feeding.  Without question, the amount of damage occurring on a plant is directly proportional to the density of squash bugs. While foliage tends to be the primary focus as a food source for the squash bug, the stems and fruit are also fed heavily upon.  Such intensity of feeding on a given plant can cause an entire plant, or section of plant, to die, while nearby plants remain healthy.

Squash bug adults are unusually difficult to kill with insecticides.  Adult control can be accomplished if the correct material is selected, however, it is more effective to target the nymphs.  A word of caution – cucurbit production requires pollinators, specifically, the honeybee – pesticide application while blooms are present should be done with extreme care.  Apply one that has little residual activity and do so only late in the day when there is minimal honeybee active in the garden.

The tendency of squash bugs to aggregate in sheltered locations can be used to advantage by the home gardener. Placing boards, large cabbage leaves, or other shelter for squash bugs induces them to congregate there during the day, simplifying there removal and disposal.

Eliminating crop debris in a timely manner is also very important. Squash bugs will often be found feeding on old fruit or in abandoned plantings, so clean cultivation is essential to reduce the overwintering population.  Good garden hygiene has been shown to be the easiest, most effective organic means of controlling this pest.