Protecting the Squash Sister

Squash plays a fundamental role in the story of the Americas. Squash historically served as one of three Native American staple crops, along with beans and corn. Together, these three crops are known as the “Three Sisters.”

In addition to its significance to humans, squash plays an important role in North American ecosystems. For example, the North American squash bee exists specifically to pollinate squash crops. Developments in human agriculture are harming native pollinators such as the squash bee, however. In order to control harmful pests commonly called squash bugs, farmers growing squash tend to spray chemical pesticides. Fortunately, alternatives to indiscriminate pesticide use exist for those interested in sustainable squash production.

In order to understand how these alternative pest control options work, it is important to first understand the biology and behavior of the targeted pest. Squash bug eggs take a week to hatch. The first generation is born during late spring through mid-June, and a second generation appears in the late summer and early fall. Before becoming adults, young squash bugs molt several times. They look gray-brown with wings right before reaching the shiny green adult stage, and they often appear in clusters on a plant. Squash bugs feed on the sap of squash plants. They puncture the plant, which causes it to wilt. This feeding behavior is often referred to as “lacerate and flush.” Squash bugs feed on the actual fruit in addition to the plant, which causes rotting and dead spots that reduce fruit quality.

Squash Bug Life Stages. Image Credits: Eva Melady

Squash Bug Life Stages. Image Credits: Eva Melady

The squash bug is the most common pest to affect crops at Skarsgard Farms in Albuquerque, New Mexico, and the farmers combat the problem by “beating them out.” This means the farmers understand the life cycle of the squash bug and plan around it by planting their squash at unusual times. The height of squash bug destruction occurs during the warm days of late spring, for that is when squash bug reproduction takes place (Cranshaw, 2008). The squash bugs target immature squash plants during this time. By the time the squash bugs plan to mate, however, Skarsgard already has mature summer squash plants. These mature squash plants are not ideal mating sites because squash bugs specifically need germinating squash in order to reproduce (Cranshaw, 2008).

Monte Skarsgard. Image Credits: Randy Siner

Monte Skarsgard. Image Credits: Randy Siner

The mature squash plants are also stronger and healthier than they would have been if they were younger during squash bug reproduction. The farmers at Skarsgard note that the healthier a plant is, the more resistant it is to pests. Aside from obvious advantages in terms of pest management, Skarsgard says that having squash available earlier than usual means better prices and a greater diversity of vegetables for their customers. Skarsgard Farms believes in working with nature rather than using pesticides. According to Monte Skarsgard, “Let nature take over, and [the agrarian ecosystem] will reach equilibrium.”

For those not keen on giving up pesticide use completely, a farming technique called perimeter trap-cropping (PTC) significantly reduces the environmental and economic impact of pesticides. This pest control option involves planting a crop that is more attractive to pests in a perimeter around a central crop. Pests will leave the main crop in order to feast on the perimeter crop, and farmers can take advantage of this by exclusively spraying the perimeter crop. Blue Hubbard Squash is an effective perimeter crop that farmers can plant around a main squash crop. Squash bugs generally find it more attractive than other types of squash plant. PTC systems using Blue Hubbard in squash fields can reduce insecticide use by 94%. “Turks’ Turban” squash also works as a perimeter trap crop, but Blue Hubbard works better because it will not die as quickly and it also has better resistance to bacterial infection.

Certain management steps are necessary for PTC.

  • Keep the perimeter crop plant healthy, so don’t neglect it. This will prevent an outbreak of bacterial infection in addition to preventing die-off before the end of the season.
  • Monitor the trap-crop regularly.
  • Spray the trap-crop as soon as the squash bugs start to infest it. This will increase the survival chances of the trap-crop.
  • Do not try PTC if there will be huge gaps in the barrier. Multiple rows of the trap-crop might be necessary.

To learn more about PTC, explore the following articles:

Comparison of Perimeter Trap Crop Varieties: Effects on Herbivory, Pollination, and Yield in Butternut Squash

Demonstrating a Perimeter Trap Crop Approach to Pest Management on Summer Squash in New England

Using Trap Crops for Control of Acalymma vittatum (Coleoptera: Chrysomelidae) Reduces Insecticide Use in Butternut Squash

-Posted by Amy

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