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Insect Communities in the Garden and Landscape: The Power of Observation

Plant diversity creates habitat diversity for insects, spiders, and related arthropods to live and thrive. LayLa Burgess, ©2018 HGIC, Clemson Extension

Plant diversity creates habitat diversity for insects, spiders, and related arthropods to live and thrive.
LayLa Burgess, ©2018 HGIC, Clemson Extension

Many inexperienced gardeners are wary of insects because insect pests are known to cause damage to vegetables, fruits, flowers, or ornamental plants, while others may sting or bite. However, experienced gardeners understand the benefit of insects as pollinators and natural predators. These savvy gardeners may encourage or tolerate the presence of insects in planted spaces.

Understanding the roles of insects in the garden or landscape is essential as issues concerning pollinator protection, the use of beneficial insects as natural pest control, and invertebrate (lacking a backbone) conservation continue. Novice gardeners may find it challenging to determine the various roles of insects and where crossovers may be occurring. Simply observing insect communities in planted areas can provide valuable insight to help gardeners attract pollinators and beneficial insects while implementing effective integrated pest management (IPM) strategy to minimize insect pests. IPM can effectively lead to the best management practices used by the gardener. For more information on IPM, see HGIC 2755, Integrated Pest Management (IPM).

While many individuals are fascinated by insects and spiders, others may find them frightening and repulsive. Surprisingly, however, those uneasy about insects and spiders are still curious about “just what kind of insect or spider is that?” Curiosity is an effective tool.

Background Information

Entomology is the study of insects. However, closely related organisms, such as spiders, daddy long-legs, centipedes, millipedes, scorpions, ticks, and mites, are often included. This group of organisms is classified as arthropods.

What are the similarities and differences between insects and spiders?

Insects have: Spiders have:
an exoskeleton (rigid external covering for the body) an exoskeleton
segmented bodies and appendages segmented bodies and appendages
digestion, excretion, nervous, respiratory, and circulatory systems digestion, excretion, nervous, respiratory, and circulatory systems
3 body regions: head, thorax, abdomen 2 body regions: fused head & thorax, abdomen
3 pairs of legs (6 legs total) 4 pairs of legs (8 legs total)
2 pairs of wings, usually (one pair may be reduced in size) eight eyes (most, but not all) and chelicerae (appendages) with fangs

A leaf-footed bug is an insect and a garden pest. LayLa Burgess, ©2018 HGIC, Clemson Extension

A leaf-footed bug is an insect and a garden pest.
LayLa Burgess, ©2018 HGIC, Clemson Extension

Spiders are distinct from insects by having 2 body parts and 8 legs. Spiders are insect predators. LayLa Burgess, ©2018 HGIC, Clemson Extension

Spiders are distinct from insects by having 2 body parts and 8 legs. Spiders are insect predators.
LayLa Burgess, ©2018 HGIC, Clemson Extension

Entomologists interested in insect and spider identification study taxonomy. Taxonomy is the science of naming, defining, and classifying organisms based on shared characteristics.

There are approximately 1.3 million species of insects and 35,000 species of spiders described worldwide. Like plants and other organisms, many insects and spiders share common names; this can be confusing for identification purposes. To distinguish specific insects or spiders from one another, taxonomists classify each one with a unique scientific name consisting of a genus and species. For example, the scientific name for the Eastern Tiger Swallowtail is Papilio glaucus.

For most usual insect or spider identifications, the common name will suffice. At times, however, it is necessary to know the scientific name of an insect or spider for proper identification and appropriate control methods.

Entomologists investigate water quality by sampling and identifying aquatic insects along streambanks. LayLa Burgess, ©2016 HGIC, Clemson Extension

Entomologists investigate water quality by sampling and identifying aquatic insects along streambanks.
LayLa Burgess, ©2016 HGIC, Clemson Extension

Clemson Cooperative Extension offers a few services for proper identification of insects, spiders, and other related arthropods. Gardeners can send photos of arthropods for identification to the Home and Garden Information Center by email at hgic@clemson.edu. Alternatively, samples can be submitted through the local county Extension office to the Plant and Pest Diagnostic Clinic for fee-based identification if photo identification is not possible. This may be necessary with small insects that are difficult to photograph. For more information, see HGIC 2446, Submitting Insect Samples for Identification.

Tips for submitting photos of insects or spiders for identification include:

  • Get close enough to the organism to capture identifying details, but far enough away to prevent blurring of the photo.
  • Place a coin, ruler, or another object alongside the insect in the photo for scale reference.
  • Include the county, where the insect was found (inside the home or outside in the lawn, landscape, or on a specific plant), and when the photo was taken (date and time of day).

For more information on submitting photos for identification, see How To Take Good Photos For Your Extension Agent.

While insects and spiders exist almost everywhere, their presence is determined by the requirements necessary to complete their life cycle (the transformation from an immature to an adult form). Appropriate habitat and food resources must be present at single or multiple locations to complete the process, including overwintering if necessary.

Insects undergo a lifecycle process called metamorphosis. There are two types of metamorphosis insects experience depending on the insect species: incomplete or complete metamorphosis. Incomplete, also known as simple, metamorphosis includes gradual changes in form from egg to nymph to the adult. During simple metamorphosis, the nymph (immature stage) looks like the adult form with wings, if present, developing externally. Nymphs and adults need similar habitats, and food resources and they are usually controlled with similar methods. Cockroaches, termites, earwigs, silverfish, and crickets are examples of insects that undergo simple or incomplete metamorphosis.

Complete metamorphosis involves more drastic changes in an insect’s form during development. The four distinct stages of complete metamorphosis include the egg, larva, pupa, and the adult with the immature (larva or caterpillar) phase looking dissimilar from the adult phase. When the adult insect has wings, like butterflies, the wings develop internally during the pupal phase. Usually, the immature and adult insects that have complete metamorphosis have different habitats and food resource requirements. Most often, only the immature stage (larva or caterpillar), is damaging. Therefore, if control of the adult is required, the control methods for adult insects versus the immature form are different. Beetles, butterflies, moths, flies, fleas, ant, bees, and many other insects undergo complete metamorphosis.

Understanding the lifecycle requirements of insects can help predict whether each is found inside or outside the home. In addition, if found outside the home, then it may be that plants are involved in their development. Knowing an insect’s lifecycle helps gardeners effectively break a pest insect’s lifecycle to limit them or promote pollinators and beneficial insects to encourage the ecological services each performs in planted spaces.

Using This Knowledge in the Garden or Landscape

The basic needs for growing successful vegetables, fruits, flowers, or ornamental plants include well-drained soil, along with adequate light, water, and plant nutrients available at the planting site. When these basic needs are not met, plant health can decline, thereby making plants more susceptible to insect pest damage. Additionally, plants are more susceptible to insect pest damage when plant nutrients supplied through over-fertilization attract insects to fast-growing, green, lush, plant material.

Flowers provide protein-rich pollen for insect development. Insects cross-pollinate flowers while visiting multiple plants. LayLa Burgess, ©2018 HGIC, Clemson Extension

Flowers provide protein-rich pollen for insect development. Insects cross-pollinate flowers while visiting multiple plants.
LayLa Burgess, ©2018 HGIC, Clemson Extension

Insects are often attracted to specific compounds associated with certain plants through a sense of smell (chemical reception-olfactory) or by the sense of touch with their antennae or hairs located on body parts. Herbivory (consumption of plant material by animals) can result in the release of plant compounds that are detectable by insects. In some instances, the release of chemicals from chewed foliage will help predator insects located insect prey, creating predator-prey relationships associated with plants. This is helpful to the gardener if the predator insect controls the pest insect. Other insect-plant relationships involve the use of plant compounds by adult insects as ques for locating egg-laying sites or for assisting immature insects in locating aggregate feeding sites. Resources of food and habitat must be available for all insects to complete their lifecycle. These resources are present in gardens and landscapes, so often, plant-feeding insect damage may appear as chewed leaves or as stems showing signs of boring insects.

Eggplants are delicious when prepared as food, but the plants can become a magnet for plant feeding insects while growing in the garden. LayLa Burgess, ©2018 HGIC, Clemson Extension

Regardless of the negative or positive impacts on the planted area, the principles governing where insects and spiders are located are based on life cycle biology and behavior. This information can be used as a tool to identify insects or spiders, control insect pests, and encourage the ecosystem services available. Gardeners can better understand insect and spider communities, along with their roles in gardens or landscapes, and use this information to determine the value of these organisms.

Most gardeners are focused on growing healthy, beautiful plants, and often only notice a plant problem once decline or damage is severe. Gardeners may or may not be focused on how insects are participating throughout the growth cycle of plants. Becoming aware of insect communities within a planted area is a means for understanding how insects “fit or function” in a cultivated space along with their impacts on the plants. It also provides a means for spiders to be appreciated as predators that eat insects (a form of natural pest control), rather than something to be feared.

Raised beds can be used to grow a combination of vegetables, flowers, and herbs. LayLa Burgess, ©2018 HGIC, Clemson Extension

Raised beds can be used to grow a combination of vegetables, flowers, and herbs.
LayLa Burgess, ©2018 HGIC, Clemson Extension

If choosing to create a space specifically for the experience of observing insect communities, raised beds can provide a solution to limited space or poor soil conditions. For more information, see HGIC 1257, Raised Beds, and HGIC 1732, Treated Wood in the Landscape.

To encourage, enjoy, and observe pollinators or beneficial insects, design, preparation, and planting the appropriate plants to attract these insects is critical. For more information on both pollinator gardening and beneficial insects, see HGIC1727, Pollinator Gardening, and HGIC 1721, Incorporating Beneficials Into the Gardener’s Toolkit.

To attract butterflies, provide both pollen and nectar resources for the adult butterflies and host plants on which the adult females can lay eggs. Once eggs have hatched, the developing caterpillars will feed on larval food plants extensively. For more information on butterfly gardening, see HGIC 1701, Butterflies in the Garden, HGIC 1724, Urban Wildlife-Butterflies, and HGIC 1735, Butterflies of South Carolina.

Butterflies and moths have plant requirements for development, so plant accordingly.

Butterflies and moths have plant requirements for development, so plant accordingly.
LayLa Burgess, ©2018 HGIC, Clemson Extension

In preparing for the vegetable garden planting season, or enhancing the landscape, perform a soil test as an essential preplant step. A standard soil test analyzes soil pH, macro- and micro-nutrients, content, and provides fertilizer and lime recommendations based on specific plants to be grown. For more information on soil testing, see HGIC 1652, Soil Testing.

Garden design and plant placement require knowledge of light requirements, mature plant height and width, and proper plant spacing. If this information is not included with the seed packets or plants purchased from the nursery or online, visit the Clemson Home and Garden Information Center website or contact your local county Horticulture Extension agent for assistance. Once the garden or landscape plantings are in place, mulch, proper irrigation, and management of nutrient requirements are critical for healthy plant growth.

As the garden or landscape matures, most gardeners want to discourage insects that cause damage. Knowledge of the reasons unwanted insects are attracted to the garden or landscape can help decrease or prevent injury.

Reasons pest insects are often attracted to the garden or landscape:

  • Right plant (or wrong plant), wrong place
  • Planting at an improper time
  • Over-fertilization
  • Over-crowding of plants (improper spacing)
  • Improper pruning (includes improper timing)
  • Excessive irrigation (includes overhead irrigation rather than at ground level, especially in the evening)
  • Proximity to weeds or grasses (these may also be hosts to the insect pests)
  • Poor sanitation practices (leaving diseased plant debris in place)
  • Poor cultural practices (improper soil pH, moisture, soil composition, drainage, compaction issues, and nutrient balance)
  • Planting susceptible varieties, as opposed to resistant varieties
  • No crop rotation (vegetable gardens)

Consider that even unwanted pest insects can provide learning experiences for any type of gardener. Identifying the insects and spiders present, learning which plants insects prefer, and noting the type of insect damage caused is valuable information. These details help with designing and planting a future garden that is less susceptible to garden pests. Scout and monitor the planted area regularly and record this information in a gardening journal. These details will help with implementing an integrated pest management plan if it becomes necessary. Evaluate and set action thresholds for damage caused by pest insects (that is, the amount of damage that can be tolerated before acting). These steps aid in determining how much insect damage can be tolerated and when to implement proper control measures to prevent further damage.

These zinnias were planted close together. Japanese beetles are eating the zinnia leaves and causing extensive damage. Setting an action threshold helps determine the amount of damage that can be tolerated before acting to control the insects.

These zinnias were planted close together. Japanese beetles are eating the zinnia leaves and causing extensive damage. Setting an action threshold helps determine the amount of damage that can be tolerated before acting to control the insects. LayLa Burgess, ©2018 HGIC, Clemson Extension

The Japanese beetles can be handpicked from the zinnias and tossed into a bucket of soapy water located near the garden as a simple form of IPM. This will help reduce the damage to the foliage. LayLa Burgess, ©2018 HGIC, Clemson Extension

The Japanese beetles can be handpicked from the zinnias and tossed into a bucket of soapy water located near the garden as a simple form of IPM. This will help reduce the damage to the foliage.
LayLa Burgess, ©2018 HGIC, Clemson Extension

The Japanese beetles will drown in the soapy water. This form of mechanical IPM reduces the use of insecticides to control the Japanese beetles.

The Japanese beetles will drown in the soapy water. This form of mechanical IPM reduces the use of insecticides to control the Japanese beetles.
LayLa Burgess, ©2018 HGIC, Clemson Extension

Tools for Teaching About Insects and Spiders

farming nectar from the extrafloral nectaries of a luffa flower (Luffa aegyptiaca). LayLa Burgess, ©2018 HGIC, Clemson Extension

Plants and insects have relationships and share complex interactions. These carpenter ants (Camponotus sp.) are farming nectar from the extrafloral nectaries of a luffa flower (Luffa aegyptiaca).
LayLa Burgess, ©2018 HGIC, Clemson Extension

Insect communities within a planted area can be used as a teaching opportunity to engage others in learning more about insects, spiders, and related arthropods. Specific plant types can encourage specific insects. Planting techniques, such as proper spacing, can help encourage or discourage insects. Taking photographs, capture and release of insects through trapping and netting, and the occasional collecting of insects for display can all provide means of identification of insects and spiders.

For more information on how insects and spiders impact education, see the video: Insects in the Garden

Once identified, insect and spider behavior can be observed and studied to gain useful information regarding insect pest control methods or to encourage an appreciation for the various services they provide. Precaution should always be taken when handling any stinging or potentially dangerous insects or spiders. Simple observation, without touching, is a powerful tool.

Insects can be fun! LayLa Burgess, ©2018 HGIC, Clemson Extension

Insects can be fun!
LayLa Burgess, ©2018 HGIC, Clemson Extension

Insects can be fun!

If this document didn’t answer your questions, please contact HGIC at hgic@clemson.edu or 1-888-656-9988.

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