Wednesday, May 22, 2024

Squash Vine Borer - Melittia cucurbitae

Introduction


The squash vine borer (Melittia cucurbitae) (SVB)  is an insect pest of plants in the cucurbit family like jack-o'-lanterns pumpkins, summer squash, acorn squash and zucchini. The plants most susceptible to attack by squash vine borers are squash and pumpkins but all cucurbits can be attacked.   Cucumbers and melons are less susceptible.

Natural History

USDA


Life Cycle: The life cycle of the squash vine borer typically begins with adult moths emerging from pupae in the soil or plant debris. These moths are active during the warm months, usually from late spring to early fall, depending on the region.

Adult Moths: The adult moths are approximately 1 inch long with a wingspan of 1 to 1.5 inches. They have clear wings with red-brown markings. After emerging, female moths seek out suitable host plants, particularly plants in the Cucurbitaceae family, such as squash, pumpkins, zucchini, and gourds, to lay their eggs.

Adult squash vine borer, Melittia cucurbitae (Harris). Photographs by Lyle J. Buss, University of Florida.


Egg Laying: Female moths lay eggs near the base of host plant stems or on the undersides of leaves. They typically prefer young, succulent stems for oviposition.

Squash vine borer egg on the left versus squash bug eggs on the right


Larval Stage: Once the eggs hatch, the larvae (caterpillars) bore into the stems of the host plants, where they feed and develop. The larvae have a cream-colored body with a brown head and are legless. As they feed, they create tunnels within the stems, causing wilting, stunting, and eventually plant death.

Squash vine borer and damage to summer squash


Pupal Stage: When larvae are fully grown, they exit the host plant and burrow into the soil or plant debris to pupate. The pupal stage lasts for several weeks, with adult moths emerging from pupae to continue the life cycle.

Overwintering: Squash vine borers overwinter as pupae in the soil or plant debris, emerging as adult moths in the following spring or summer to begin the cycle anew.

Host Plants: While squash vine borer larvae primarily infest plants in the Cucurbitaceae family, they may occasionally feed on other plants, such as sunflowers and some ornamental gourds.

Management Strategies

Managing squash vine borers can be challenging, but there are several strategies that gardeners can employ to minimize damage and protect their squash plants:

  1. Cultural Practices:

    • Crop Rotation: Avoid planting squash, pumpkins, and other susceptible plants in the same area year after year.
    • Early Planting: Plant squash crops early in the season to allow them to mature before squash vine borer populations become significant.
    • Cleanliness: Remove and destroy plant debris at the end of the growing season to reduce overwintering sites for squash vine borer pupae.

  2. Physical Barriers:

    • Row Covers: Cover young plants with floating row covers to prevent adult squash vine borers from laying eggs on the stems.
    • Collars: Place physical barriers such as aluminum foil, pantyhose, or cardboard collars around the base of stems to prevent larvae from burrowing into the plant.

  3. Biological Control:

    • Beneficial Insects: Encourage populations of natural enemies such as parasitic wasps and predatory insects that prey on squash vine borer eggs and larvae.
    • Nematodes: Certain species of beneficial nematodes can help control squash vine borer larvae in the soil.

  4. Chemical Control:

    • Insecticides: Apply insecticides containing active ingredients such as carbaryl, permethrin, or spinosad according to label instructions when adult moths are active or when larvae are young and vulnerable. Always read the label, follow safety precautions and consider using organic options if available.
    • Systemic Insecticides: Soil-applied systemic insecticides can provide protection against squash vine borers by being absorbed by the plant and killing larvae as they feed.

  5. Monitoring and Early Detection:

    • Regularly inspect plants for signs of squash vine borer activity, including wilting, frass (sawdust-like excrement) at the base of stems, and entry holes.
    • Use yellow sticky traps to monitor adult moth activity and determine when to implement control measures.

  6. Hand Removal:

    • If detected early, squash vine borer larvae can be manually removed from infested stems by carefully making a small incision with a knife and extracting the larvae.

Combining multiple management strategies is often the most effective approach to control squash vine borers and protect squash crops from damage. Additionally, maintaining overall plant health through proper watering, fertilization, and disease management can help plants withstand and recover from squash vine borer infestations.

Because of a similarity in names, the squash bug and squash vine borer can easily be confused with one another.  Here are some tips for distinguishing the two insects..



Appearance: 

Squash Bug: These bugs are typically brown or gray in color and are about 1/2 inch long when fully grown. They have a distinctive shield-like shape. 

Squash Vine Borer: The adult squash vine borer belongs to the Sesiidae (clearwing) family and is a moth that resembles a wasp. It has a black body with orange markings and clear wings. The larvae, however, are white with brown heads and can grow up to 1 inch long. 

Adult Squash Vine Borer

Adult Squash Bug

Behavior: 

Squash Bug: Squash bugs primarily feed on the sap of squash plants by piercing the plant with their mouthparts. They can also transmit diseases to the plants. 

Squash Vine Borer: The adult moth lays eggs at the base of squash plants, and the larvae bore into the stems, feeding on the interior tissue. This feeding disrupts the flow of nutrients, causing the plant to wilt and eventually die. 

Damage: 

Squash Bug: Squash bugs cause damage by sucking the sap from leaves, stems, and fruit. This can lead to wilting, yellowing, and stunted growth. They can also transmit bacterial wilt, a disease that can quickly kill plants. 

Squash Vine Borer: The larvae of squash vine borers tunnel into the stems of squash plants, causing wilting, collapse, and death of the affected vines. Infested plants often exhibit sawdust-like frass at the base of the stems, which is a telltale sign of squash vine borer activity.


Posted by at