Fighting insects never stops. Here are three bad bugs you may see in your garden or greenhouse most anytime of the year.
Many thanks to Cyd Brown, Somervell County Master Gardener, for submitting these articles.
Fungus Gnat (Bradysia spp)
IDENTIFICATION AND BIOLOGY
Fungus gnats are one of the most common types of gnats found in Texas. Adults are 1/8 inch long, delicate-looking blackflies with slender legs and thread-like antennae. They are attracted to light and you may see them “dancing” above the soil surface or flying around windows and lights.
Larvae live in the soil and are clear to white, about 2mm (0.08inch) long with shiney black head
capsules.
DAMAGE
Adult fungus gnats are considered a nuisance as they feed on plant liquids. Larvae feed on organic matter by burrowing into the plant or feeding on root hairs causing wilting, even when watering is satisfactory. Extreme infestations of Fungus Gnat larvae can stunt or kill young plants.
MONITORING
The use of sticky traps can aid in monitoring for fungus gnat adults. Best results are obtained by using small pieces of sticky trap laid horizontally on top of the soil. Peeled potato chunks, 1” by ½” will attract larvae when placed on the soil surface. When you see larvae in the potato, sometimes in as little as 4 hours, throw away and replace.
MANAGEMENT
Cleanliness is key when battling Fungus Gnats in the greenhouse. Remove plant, debris, old potting mix diseased plants and other organic trash.
Light infestations may be controlled with the sticky traps and potato chunks. Large infestations may be treated with biological control agents like Steinernema nematodes or Hypoaspis predatory mites. The biological insecticide Bacillus thuringienses subspecies israelensis (Bti) may provide fast-acting, temporary control.
Mealey Bugs (Pseudococcidae spp)
Male (winged) and female Mealy Bugs
IDENTIFICATION AND BIOLOGY
Mature male mealybugs are soft, wax-covered, insects of many genera. Adult females are wingless with oval bodies covered in a white mealy wax. Mealybugs can produce both sexually and asexually, so populations of these insects can rise dramatically in a short period of time. Most species of Mealybugs lay eggs in a white cottony sac.
Mealybugs suck plant sap and may produce sticky honeydew that leads to sooty mold growth on leaves which can impede photosynthesis.
DAMAGE
Mealy bugs can cause a condition called “Soft Scale” – large lumps and white fluff on leaves. Soft Scale is caused by mealy bugs as well as other large sap sucking pests causing stunting, leaf. yellowing and deformation of plant parts.
MONITORING
The best method for monitoring is visual inspection. Mealybugs like to live in protected plant spots, like in the crown, in branch crotches, or on stems near the soil; so, check the plant very carefully. Some mealybugs may be found around the drainage holes of pots. To detect some underground infestations, you may have to remove the root-ball from the pot.
MANAGEMENT
Prevention is always the best. Before purchasing plants, check them over carefully for Mealy Bugs and other pests.
Soaps and oil sprays may provide some control for light infestation. Several applications may be needed. Systemic insecticides like imidacloprid or dinotefuran can be applied as soil drench. Be sure to read the product label and follow all instructions.
Whiteflies (Aleyrodidae spp)
IDENTIFICATION AND BIOLOGY
Whitefly adults are small (approximately 1/16 – 1/8 inch), 4-winged, moth-like, and covered with white, waxy powder. Immatures are flat, oval, glassy to opaque, yellow or green-ish, and may have a fringe of wax filaments.
DAMAGE
Whiteflies feed on leaves, sucking juices from the plant. Damaged leaves become yellow, appear to be dry and may fall from the plant. Like Mealy Bugs, Whiteflies can produce honeydew which leads to Sooty mold fungus.
MONITORING
Check the undersides of plant leaves looking for all stages of whiteflies. A few individuals can produce thousands of young in a very short time, so inspect often. You can also use yellow sticky traps, hung just above the plant leaf canopy.
MANAGEMENT
Before purchase check plants for mealy bugs and other pests. Keep growing areas free of weeds. Cut out infested plant parts. Remove and destroy heavily infested plants. High pressure water sprays to the underside of leaves may dislodge adults and nymphs (once a week for a least three weeks) and will also wash off honeydew and sooty mold. Insecticidal soaps and oil may kill whiteflies on contact but be sure to thoroughly cover the undersides of leaves. Multiple applications may be needed.
Whiteflies have developed resistance to many pesticides. Recommended insecticides for Whiteflies include Azadirachtin, Bifenthrin, and Imidacloprid. Check the product label and follow all instructions.