Injury to Southern Highbush Blueberries by Southern Red Mites and Management Using Various Miticides

Abstract

Reports of severe infestations caused by southern red mites (SRM), Oligonychus ilicis McGregor (Acari: Tetranychidae), have increased in recent years in southern highbush blueberries (SHB). Currently, there is little known about the management of tetranychids in SHB, and only two miticides (fenazaquin and fenpyroximate) have recently been labeled for use in SHB. Oligonychus ilicis has caused up to 80%-100% losses in some blueberry plantings, and growers are looking for management tools for this new pest of blueberries. We report on injury to SHB from O. ilicis and the performance of seven miticides used to manage SRM populations, including spiromesifen, spiromesifen plus surfactant, vegetable oil concentrate, fenazaquin, "proprietary miticide" (referred to as Pro1), bifenazate, and fenpyroximate. Miticide efficacy was rated based on the number of SRM recorded on collected leaves and plant damage ratings using an arbitrary index (from 0 = no bronzing to 4 = 100% bronzing). Characteristic symptoms of leaf injury included purple or bronzed leaf color, leaf dryness and roughening. Fenpyroximate significantly reduced mite numbers three days after application. Additionally, plants treated with fenpyroximate or fenazaquin showed significantly less bronzing compared with the control plants. Overall, fenpyroximate and fenazaquin showed the best performance for the management of O. ilicis on SHB.Insects 2020, 11, 233 2 of 10 mild, dry and humid winters, when populations continue to grow without any diapause. They can complete one generation within two weeks under optimal conditions (25 ± 2 • C) on coffee and holly crops [9][10][11].Southern red mites are now one of the main pest species attacking blueberry plants in the southeastern US. They feed on plant tissues by inserting their chelicerae into the host and removing cell contents, resulting in a net photosynthesis rate decline due to chloroplast destruction [12]. Southern red mites can reproduce on both the upper and lower surfaces of the leaf. Bronzed-colored leaves are the characteristic symptom associated with SRM injury in ornamental crops, and the intensity of the bronzing is proportional to the degree of internal leaf damage [12].Oligonychus ilicis primary hosts include several ornamental plants such as camellias, azaleas, and hollies, whereas only a few fruit plants have been reported as hosts for this spider mite, including coffee, strawberry, and cranberry, the only reported host in the genus Vaccinium [9-13]. This paper reports highbush blueberry as a new host of O. ilicis from north-central Florida. Additionally, the evaluation of various newly registered miticides for the control of SRM in a commercial SHB planting, as well as information regarding leaf injury and plant damage, is included.

Mite Pests of Southern Highbush Blueberry in Florida

“…Bronze-colored leaves are the main symptom associated with southern red mite injury, and the intensity of the bronzing is proportional to the degree of internal leaf damage ( Figure 4). Like most leaf-feeding mites, the southern red mite feeds on plant tissues by inserting their mouthparts into the leaf and removing cell contents, resulting in a photosynthesis rate decline (Lopez and Liburd 2020).…”

“…Several mite species attack southern highbush blueberries (SHB), including the southern red mite (Oligonychus ilicis McGregor (Acari: Tetranychidae)), the false spider mite or flat mite (Brevipalpus yothersi Baker), and the blueberry bud mite (Acalitus vaccinii Keifer). The southern red mite is the most important mite pest attacking blueberry plants in the southeastern US (Lopez and Liburd 2020). The false spider mite is a secondary leaf-feeding mite pest that was reported attacking southern highbush blueberry in 2016 (Akyazi et al 2017).…”

Miticidal Tools for Management of Southern Red Mites Infesting Southern Highbush Blueberries

“…However, in 2016 a major tetranychid outbreak was reported in Florida at a commercial blueberry farm under protected structures [8]. In 2019, Florida and Georgia SHB growers experienced severe losses, estimated between USD 500,000 and USD 750,000, due to outbreaks of spider mites (Tetranychidae) [9]. The southern red mite (SRM), Oligonychus ilicis McGregor (Acari: Tetranychidae), was identified in 2019 as the tetranychid pest causing severe damage characterized by leaf bronzing and stunted plants in various blueberry cultivars across both states [9].…”

Castor Seed Oil: A Promising Biomitecide for Sustainable Management of the Red Coffee Mite (Oligonychus ilicis) (McGregor, 1917) (Prostigmata: Tetranychidae)

“…), being one of the most important pests for the conilon coffee crop in Brazil [2]. Coffee tree red mite attack is favored by prolonged drought periods, affecting the entire crop if not controlled at the beginning of the infestation [3]. Oligonychus ilicis perforate the leaves cells and suck part of the cellular content to feed, causing a photosynthetic area of the leaves reduction, leaving them with a tanned appearance and covered with webs [2,4].…”