greenhouse insects

Introduction

Presentation on identification of insect and mite pests affecting greenhouse production systems conducted by Raymond A. Cloyd, Kansas State University. The presentation elaborates on various facets of pest management, focusing on the critical aspects of feeding habits, life cycles, behavior, and the extensive range of damage caused by these pests. Understanding these factors is vital for effective pest management in greenhouse horticulture.

Overview of Presentation

The focus is on accurately identifying insect and mite pest problems in greenhouse production, which is essential due to the susceptibility of greenhouse-grown horticultural crops to a variety of pests occurring simultaneously. A keen understanding of symptoms related to pest infestation is critical in diagnosing issues accurately. This includes:

  • Symptomatic Patterns:

    • Random: Symptoms distribute randomly across the plant.

    • Uniform: Symptoms occur uniformly across the plant due to consistent environmental factors or pest behavior.

    • Clumped: Symptoms cluster around specific areas often due to localized infestation.

  • Examination Areas:

    • Important areas to examine include leaves, stems, flowers, fruits, and roots, as pests can affect various plant parts differently.

  • Examples of Symptoms:

    • Biotic: (resulting from living organisms like insects, mites, diseases): commonly exhibit random or clumped patterns.

    • Abiotic: (due to environmental conditions, cultural practices, or chemical injury): generally display uniform patterns.

Major Insect and Mite Pests of Greenhouse Crops

The most common pests affecting greenhouse crops include:

  • Aphids

  • Shore Flies

  • Thrips

  • Leafminers

  • Fungus Gnats

  • Mealybugs

  • Whiteflies

  • Mites

Insect and Mite Feeding Behaviors

Feeding behaviors of pests are categorized as follows:

  • Phloem Feeders:

    • Includes pests like Aphids, Whiteflies, Mealybugs, Leafhoppers, Soft Scales that primarily feed on the nutrient-rich phloem sap of plants.

  • Xylem Feeders:

    • Includes True Bugs and Spittlebugs, which extract water and nutrients from the xylem.

  • Chewers:

    • Chewers such as Beetles and Caterpillars remove various plant tissues including leaves, stems, flowers, and roots, resulting in visible damage.

  • Miners:

    • Leafminers create tunnels and mines in the foliage as they feed.

  • Chlorophyll Feeders:

    • Spider Mites are noted for damaging chlorophyll, leading to stippling on leaves.

  • Fluid-Feeders:

    • Thrips puncture cells to extract fluids, causing damage and potential bacterial infections.

Damage Symptoms Based on Feeding Behavior

Symptoms of damage vary according to feeding behavior:

  • Phloem and Xylem Feeders:

    • Symptoms often include stunting, wilting, leaf distortion, and yellowing, particularly affecting lower leaves.

  • Chewers:

    • Symptoms manifest as removal of significant plant tissues, leading to dieback of leaves, flowers, and stems.

  • Miners:

    • Identification of visible serpentine or blotched mine patterns on leaves is characteristic of miners.

  • Internal Feeders:

    • Symptoms may present as stunted growth with small leaves resembling signs of nutrient deficiencies or viral infections.

Detailed Pest Profiles

Aphids

Feeding behavior involves targeting terminal growth, which leads to high populations congregating in significant numbers. Damage symptoms include:

  • Leaf distortion

  • Stunting and wilting, which stress plants and reduce yield.

Common types of aphids include:

  • Green Peach Aphid (Myzus persicae)

  • Melon/Cotton Aphid (Aphis gossypii)

  • Potato Aphid (Macrosiphum euphorbiae)

  • Foxglove Aphid (Aulacorthum solani)

  • Chrysanthemum Aphid (Macrosiphoniella sanborni)

Direct and Indirect Damage from Aphids

  • Direct Damage: Leaf feeding which leads to overall growth problems.

  • Indirect Damage: The production of honeydew, leading to black sooty mold and attracting ants, which may act as protectors for aphids, complicating management efforts.

Western Flower Thrips (Frankliniella occidentalis)

  • Damage: Direct injury to leaves and flowers leads to distorted growth; also involved in the indirect transmission of tospoviruses (e.g., INSV, TSWV).

  • Life Cycle: Consists of Egg > Larvae > Pupae > Adult stage lasting 18-24 days and is temperature-dependent.

Fungus Gnats

The larvae primarily feed on plant roots which can lead to notable stunting and wilting; they are also vectors for soil-borne pathogens.

  • Life Cycle: Egg > Larva > Pupa > Adult, typically requiring 20-24 days.

Whiteflies

These pests primarily feed on the underside of leaves, leading to leaf distortion and wilting.

  • Life Cycle: Egg > Nymphs > Pupa > Adult, taking approximately 21-26 days.

Shore Flies

Considered a nuisance due to their high populations indicating overwatering or excess algae, their larvae do not feed on roots but may impact plant health indirectly.

Leafminers

These pests cause damage by tunneling through leaf layers, leading to unsightly damage and may thrive in weeds as secondary hosts.

Mealybugs

These pests feed within the vascular system of plants causing damage similar to aphids and produce honeydew, promoting fungal growth.

Mite Types

Common types of mites affecting greenhouse crops include:

  • Twospotted Spider Mite (Tetranychus urticae)

  • Broad Mite (Polyphagotarsonemus latus)

  • Cyclamen Mite (Steneotarsonemus pallidus)

Twospotted Spider Mite

  • Feeding leads to stippling of leaves characterized by small yellow spots and thrives in warm, dry greenhouse conditions.

  • The life cycle can progress from egg to adult in as short as 7-10 days under optimal conditions.

Broad Mite

  • Very small in size, this mite requires high humidity and cooler temperatures for survival. Damage often resembles nutritional deficiencies in crops, leading to significant crop stress.

Cyclamen Mite

  • Similar in size to Broad Mite and also thrives in high humidity environments, causing considerable damage to plant tissues.

Extension Publications on Managing Pests

Various resources and extension publications are available focused on the integrated management of pests, providing guidance specific to notable pests like Aphids, Thrips, Fungus Gnats, Whiteflies, Shore Flies, and Mites. These publications inform best practices, treatments, and prevention strategies to maintain plant health in greenhouse environments.

Conclusion

The importance of identifying and managing insect and mite pests within greenhouse production systems cannot be overstated, as it directly impacts crop health and productivity. Effective pest management strategies are essential in ensuring sustainable greenhouse operations that produce healthy-yielding crops.