urban-gro helps maximize the economic yield of new and existing cultivation facilities via our Integrated Pest Management services. Learn how to identify the most common pest pressures we typically see in facilities.
Two spotted spider mite (tetranychus urticae)
Identification
- Oval in shape
- 1/50 inch long
- Greenish-yellow to translucent in color
- Large dark ventral lateral spots are body waste
- 1st larval stage only has 6 legs
Nymphs, adult males, and reproductive adult females are oval and generally yellow or greenish in color and have one or more dark spots on each side of their bodies. Two-spotted spider mite eggs are about 0.14 mm in diameter and are usually laid on the undersides of leaves. They are spherical,

hatch approaches. Two-spotted mites suck cell contents from leaves, initially stippling leaves with a fine pale green mottling. As feeding continues, the stippling increases resulting in the leaves turning yellow with bronzed or brown areas. Undersides of the infected leaves may have several mite exoskeletons. The webbing on flowers and foliage is a sign of a serious infestation. Yield and quality are severely affected when large mite populations are allowed to proliferate unchecked.
Western Flower Thrips (Frankliniella occidentalis)
Identification
- Hemimetabolous Metamorphosis: Egg – Larva I and II – Pupa I and II - Adult
- Fully developed wings
- Less than 2mm in length
- Three color morphs: (1) dark-brown (2) light (3) yellow with a dark longitudinal band along the dorsum of the thorax and the abdomen
Thrips are often found in the flower buds. These flowers may be tapped or lightly shaken over a white sheet of paper (a drop cloth, of sorts) where you will be able to see their slender, small bodies racing around. Each adult is elongated and thin, with two pairs of long wings. The eggs are oval or kidney-shaped, white, and about 0.2 mm long. The larva is

Rice Root Aphid (Rhopalosiphum abdominalis/rufiabdominalis)
Identification
- Hemimetabolous Metamorphosis: Egg – Nymph - Adult
- Apterous (wingless) nymphs are 1.8 mm in length
- Green-bluish body with brown-black head, siphunculi and cauda.
- Alate (winged) adults are black with a blue-green abdomen.
- Alate (winged) adults have a body length of 1.4-2.4 mm.

Fungus Gnat (Bradysia spp.)
Identification
-
Adult fungus gnats are approximately 1/8 inch long.
-
Legs and wings comparatively long with long antennae as well.
-
Small rounded head with moderately prominent eyes that meet above the base of the thread-like antennae.
-
Larvae are white, slender and legless with a black head and smooth semi-transparent skin revealing digestive tract contents.
- Larvae are approximately ¼ inch in length when fully grown.

Powdery Mildew (Sphaerotheca macularis)
Identification
- Powdery Mildew fungi are obligate, biotrophic parasites.
- During the growing season, hyphae are produced on both the dorsal and ventral sides of the leaf surfaces; however, some species are restricted to one leaf surface only.
- Haustoria, also know as specialized absorption cells, extend into the plant epidermal cells to obtain nutrition.
- Conidia, produced on the plant surfaces, either develop singly or in chains and ultimately contribute to the production of new sexual spores.
Powdery mildew is one of the most common pests of cannabis and is one of the easier plant diseases to identify as its symptoms are quite distinctive. Infections occur when powdery mildew spores (conidia) contact a suitable host and environmental conditions are favorable. Initial symptoms are small, circular, powdery, white

Hemp Russet Mite (Aculops cannabicola)
Identification
- Elongate body with pale color.
- All legs extend anteriorly from the front of the head
- Need 15-20x magnification for observation of physical characteristics.
A single russet mite is too tiny to be seen by the human eye without magnification of 14x and higher. Their near invisibility makes these mites a particular threat to become established in your commercial grow before you realize it. Unlike spider mites, these voracious plant pests leave no webbing or other secretions when present. Visible damage to the

Pythium Root Rot (Pythium spp.)
Identification
- Pythium is primarily a seedling disease.
- Root tips are brown and dead.
- Plants yellow and die.
- Brown tissue on the outer portion of the root easily pulls off leaving a strand of vascular tissue exposed.
- The cells of roots contain round, microscopic, thick-walled spores.
Pythium root rot can develop at any time during the growing season if the soil remains saturated, warm, or depleted of oxygen for prolonged periods. Pythium root rot is a persistent problem in areas that are poorly drained or over-irrigated. From a distance, root symptoms can appear orange, yellow, or dark and greasy. Slowed growth and soft plants (low turgor pressure) is often the first sign that will be seen. We recommend lab tests to confirm the species so treatment plans can be tailored. Pythium attacks either juvenile tissues, such as the root tip, or roots damaged by mishandling or invertebrate pest damage. After gaining entrance to the root the fungus may cause a rapid, black rot of the entire primary root and may even move up into the stem tissue. As the substrate dries, new roots may be produced and the plant may recover or never show symptoms of disease. The depth and density of roots will be drastically reduced in affected areas. Under continued anaerobic conditions, more and more roots are killed and the plant may wilt, stop growing, or even collapse and die. This often occurs in the presence of fungus gnats.
Having issues with pest pressures in your facility? Get a compliant IPM program to increase your plant performance with an urban-gro tailored program for your facility. Contact us at ugipm@urban-gro.com or fill out our form here.
urban-gro for Experienced CEA Facility Systems Design
urban-gro, Inc.® (Nasdaq: UGRO) is a global engineering and design services company focused on the commercial horticulture market. With experience in hundreds of Controlled Environment Agriculture (CEA) facilities spanning millions of square feet, we engineer, design, and integrate complex environmental equipment systems into high-performance facilities. Once operational, urban-gro’s gro-care® Managed Services Platform leverages the company's expertise to reduce downtime, provide continuity, and drive facility optimization. Operating as a crop-agnostic solutions provider in both food and cannabis CEA sectors, our crop-focused end-to-end approach provides a single point of accountability across all aspects of growing operations. Visit urban-gro.com to discover how we help you gro plants and gro profits.