See information from UF/IFAS on scouting rust mites and thrips in citrus groves.
We shared information in our last blog on adding pests like rust mites and thrips to your citrus pest management plan. Find information on scouting rust mites and thrips from the 2024–2025 Florida Citrus Production Guide below.
Scouting and Treating Rust Mites and Thrips
The production guide shared the following information on scouting and treating rust mites and thrips:
Citrus Rust Mites: “The citrus rust mite (CRM) and the pink citrus rust mite (PCRM) are found on all citrus varieties throughout Florida. Although they can coexist on the same leaf or fruit, the CRM is usually the prevalent species. PCRM generally develops to greater damaging populations early in the season (April–May). Both rust mites are important pests of fruit grown for the fresh market. On some specialty varieties (such as Sunburst tangerine), damage may be particularly severe on stems and foliage, causing leaf injury and possible abscission. Fruit damage is the main concern with other varieties. Both mites feed on green stems, leaves, and fruit, with the PCRM being potentially more destructive…”
“Egg hatch occurs within approximately 3 days at 81°F. Newly hatched larvae resemble the adult, changing in color from clear to lemon yellow (CRM) or pink (PCRM) after molting to the nymphal stage. After about 2 days at 81°F, molting occurs. The first nymphal stage resembles the larval stage and requires about 2 days to molt to an adult at the above temperature. CRM adults have an elongated, wedge-shaped body about three times longer (0.15 mm) than wide. PCRM are narrower, smaller, and rounded. CRM is usually straw to yellow in color, and PCRM is usually pink, but color is not always an effective or accurate means of separating the two rust mites. Males and females have an average life span of 6 and 14 days, respectively, at 81°F. In the field, females can live nearly 30 days in the winter. Rust mites develop from eggs to adults in 6 days at 81°F.
PCRM populations can begin to increase in April to early May on new foliage, reaching a peak in mid-June to mid-July, although the time of peak density can vary by several weeks depending on geographical location and weather. PCRM are more abundant in drier weather conditions. CRM population densities increase in May–July, then decline in late August, but can increase again in late October or early November. Mite densities in the fall rarely approach those occurring early in the summer. During the summer, CRM are more abundant on fruit and foliage on the outer margins of the tree canopy. The bottom portion of the north side of the tree canopy is generally preferred and supports the highest mite populations. The least favorable conditions for CRM increase are found in the top portion of the south side of the tree canopy.
Visible characteristics of mite injury differ according to variety and fruit maturity when damage occurred. When rust mite injury occurs on fruit during exponential growth, before fruit maturity (April to September), epidermal cells are destroyed, resulting in smaller fruit. These destroyed epidermal cells fracture as the fruit enlarges, causing a rough form of russeting known as “sharkskin.” Damage to mature fruit creates a brown stain but does not destroy epidermal cells or the wax layer, leading to a polished look referred to as “bronzing.” Fruit damage by rust mites affects the appearance and reduces grade initially but may also lead to reduced size, increased water loss, and increased drop under severe infestation.
Leaf injury caused by feeding of CRM exhibits many symptoms on the upper or lower leaf epidermis. When injury is severe, the upper cuticle can lose its glossy character, taking on a dull, bronze-like color or patches of yellowish discoloration where wounded epidermal cells have released ethylene. Damage to lower leaf surfaces results in collapse of spongy mesophyll cells, appearing first as yellow patches and later as necrotic spots. With the exception of upper leaf epidermal injury to some specialty varieties, such as Ambersweet, Fallglo, and Sunburst, defoliation caused by CRM is rarely severe.”
Thrips: “Thrips are small, elongate insects in the order Thysanoptera, varying in size from less than 0.2 mm to over 2.0 mm in length. They are easily overlooked because of their minute size. The life cycle of a thrips species consists of an egg, two larval feeding stages, a nonfeeding prepupal stage, a nonfeeding pupal stage, and feeding adults. About 14–18 days are required to complete development from egg to adult in some Frankliniella species.”
Griffin Fertilizer is committed to helping both growers and ranchers make sound agronomic and economic decisions in order to maximize the health of their grove and pasture. As a full-service custom dry & liquid fertilizer blender and crop protection product distributor, we will continue our mission to further advance Florida agriculture. For questions -or concerns about your farm or pasture, contact us and one of our team will be in touch.
