Honeylocust spider mite adults sometimes overwinter in huge clusters on host plant bark. These overwintering adults are less than 1 mm in length and bright orange in color. They may be found in bud scars or cracks in the bark. The eggs of these spider mites are laid in the spring (early to mid-June in New England) and hatch just following budbreak. Each female may lay up to 70 tiny, white eggs along leaf veins and the crotches of leaf veins. Newly hatched immatures have 6 legs and are transparent until feeding occurs, at which time they develop a green color. An individual honeylocust spider mite can develop from egg to adult in as quickly as 4 days in the summer, and 11 days in cooler weather (Johnson and Lyon, 1991). Development may be influenced by weather conditions, humidity, and food availability and quality. Adult forms in the summer range in color from pale yellow to green. The life stages of the honeylocust spider mite include: egg, 6-legged larva, 8-legged protonymph (1st form), 8-legged deutonymph (2nd form), and 8-legged adult (Witte, 2013). Several generations occur per year. Populations may quickly develop, causing severe host plant injury by midsummer, and then collapse. Following population collapse, new growth of honeylocust may remain green. In light infestations, when viable host plant foliage remains available, honeylocust spider mites may continue to reproduce through the fall until the adult females move to the bark to overwinter. Dispersal is reported to occur on wind currents during periods of overcrowding.
Light infestations cause light, yellow stippling on leaves which may be barely noticeable. Heavy infestations cause distortion of newly emerging foliage and by July, all of the foliage on a severely infested tree may turn brown. Damage is similar to that of honeylocust plantbug. Stippling of infested foliage and canopy bronzing, stunted growth, and premature leaf drop may all occur on heavily infested trees. If damage occurs early enough in the season, the tree may refoliate. Honeylocust spider mite populations may be more severe on dry sites or when drought conditions occur.
Scout for overwintering orange adult mites on host plant twigs near bud scars or in bark cracks and crevices. 10X hand lens may be needed for magnification. Monitor leaves in the early spring and throughout the growing season for increasing stippling or discoloration.
Dry conditions or drought favors most or nearly all spider mites. They feed more under dry conditions, and the lower humidity allows them to evaporate excess water through excretion. Do not plant honeylocust at dry sites if spider mites are a concern. Most spider mite natural enemies require more humid conditions and are stressed by periods of drought. Plants stressed by drought can also change chemically in ways that make them more nutritious to spider mites, thus favoring their populations. Adequate watering of plants during dry conditions can help to limit the impact of drought stress on spider mite outbreaks. Hose plants periodically with a forceful jet of water, which may also physically remove and kill mites, as well as remove dust collecting on foliage that may interfere with the efficacy of mite predators (Cranshaw and Sclar, 2014).
Predatory mites, particularly the phytoseiid mites, usually keep this pest spider mite's population beneath damaging levels. Additional natural enemies of the honeylocust spider mite include lacewing larvae, minute pirate bugs, spiders, predatory thrips, predatory midges, and certain species of lady beetles. An additional predator of honeylocust spider mites includes Zetzellia mali, a predatory mite in the Family Stigmaeidae; however, phytoseiid mites are thought to offer greater management of honeylocust spider mite populations. If chemical management is deemed necessary, select reduced risk options in order to preserve natural enemies and predatory mites to help reduce populations of the honeylocust spider mite. See notes below regarding the potential impact of broad spectrum insecticides on predatory mites.
Abamectin (NL)
Acephate (NL)
Beauveria bassiana (NL)
Bifenthrin (NL)
Chlorpyrifos (N)
Chromobacterium subtsugae (NL)
Cypermethrin (NL)
Etoxazole (N)
Fenazaquin (NL)
Gamma-cyhalothrin (L)
Hexythiazox (NL)
Horticultural oil (L)
Insecticidal soap (NL)
Isaria (paecilomyces) fumosoroseus (NL)
Lambda-cyhalothrin (L)
Malathion (L)
Metarhizium anisopliae (robertii) (NL)
Neem oil (NL)
Spinetoram+sulfoxaflor (N)
Spinosad (NL)
Spiromesifen (L)
Tau-fluvalinate (NL)
Some studies suggest that early season applications of bifenthrin cause outbreaks of honeylocust spider mites due to the impact of bifenthrin on phytoseiid predatory mite populations. By contrast, later season applications of bifenthrin did not cause honeylocust spider mite outbreaks. Pyriproxyfen, an insect growth regulator, was found to preserve predatory mite populations while not causing subsequent honeylocust spider mite outbreaks (Witte, 2013).
Active ingredients that may be applied systemically include: abamectin (injection), acephate (injection), Metarhizium anisopliae (robertii) (soil drench), and neem oil (soil drench).
When used in nurseries, chlorpyrifos is for quarantine use only.
Make insecticide applications after bloom to protect pollinators. Applications at times of the day and temperatures when pollinators are less likely to be active can also reduce the risk of impacting their populations.
Note: Beginning July 1, 2022, neonicotinoid insecticides are classified as state restricted use for use on tree and shrub insect pests in Massachusetts. For more information, visit the MA Department of Agricultural Resources Pesticide Program.
