Residual effect of commonly used fungicides in strawberries on Amblyseius swirskii, Neoseiulus cucumeris, and Neoseiulus californicus (Mesostigmata: Phytoseiidae).

Florida's strawberry industry is currently valued at $511 million annually but faces challenges from pathogens and arthropod pests especially Tetranychus urticae Koch (twospotted spider mite) and Scirtothrips dorsalis Hood (chilli thrips). Predatory mites, particularly Neoseiulus cucumeris Oudemans, Neoseiulus californicus McGregor, and Amblyseius swirskii Athias-Henriot, play a crucial role in pest management. However, there are concerns regarding how these biological control agents are affected by fungicides used in current pathogen management strategies. This study assessed the residual effects of commonly used fungicides in strawberries on the survival, feeding, and oviposition of these predatory mites. Commercially sourced predatory mites were reared on S. dorsalis larvae, and gravid female predators placed on fungicide treated strawberry leaf discs in a Munger cell for 120 h. Fungicides tested included two formulations of Captan, hydrogen peroxide + peroxyacetic acid, cyprodinil + fludioxonil, tetramethylthiuram disulfide, cyflufenamid and a control. All fungicides tested had an impact on the survival, feeding, and oviposition of the predators. Among the fungicide treatments, the lowest predator survival was observed in the cyprodinil + fludioxonil treatment, while the highest was observed in the hydrogen peroxide + peroxyacetic acid and tetramethylthiuram disulfide treatments. In all treatments, feeding and oviposition greatly varied among predators; specifically, N. cucumeris and A. swirskii had the lowest prey consumption, while N. californicus had the highest. These findings highlight the potential incompatibility between fungicides and predatory mites and demonstrate the need for the development of a fungicide rotation program tailored to the different susceptibilities of predators to fungicides.

Monitoring the susceptibility of Bemisia tabaci Middle East-Asia Minor 1 (Hemiptera: Aleyrodidae) to afidopyropen, cyantraniliprole, dinotefuran, and flupyradifurone in south Florida vegetable fields.

Bemisia tabaci Middle East-Asia Minor 1 (MEAM1) is a significant pest that damages a wide range of high-value vegetable crops in south Florida. This pest has demonstrated the ability to develop resistance to various insecticide groups worldwide. Monitoring the resistance levels of MEAM1 populations and maintaining baseline susceptibility data are crucial for the long-term effectiveness of insecticide management strategies. We conducted serial dilution bioassays on 15 field populations of MEAM1 collected in south Florida to assess their resistance to 4 key insecticides: afidopyropen, cyantraniliprole, dinotefuran, and flupyradifurone. To quantify resistance levels, resistance ratios (RR) were generated by comparing the LC50 values of field populations to those of a known susceptible MEAM1 colony reared in the laboratory. Our findings reveal that all field-collected populations were susceptible to dinotefuran (RR 1-8) and flupyradifurone (RR 2-8). While over 80% of the populations tested were susceptible to afidopyropen (RR 1-9), 2 populations exhibited low (RR 38) and moderate resistance (RR 51), respectively. In contrast, most of the populations (57%) showed low to moderate resistance to cyantraniliprole (RR 21-78), and the remaining populations were susceptible (RR 3-10). The 2 populations with resistance to afidopyropen also exhibited moderate resistance to cyantraniliprole. Further research in this direction can aid in refining insecticide resistance management programs in Florida and other regions where B. tabaci MEAM1 is a major pest. Exploring the implications of these findings will be essential for insecticide use and integrated pest management strategies in south Florida.

Spatial and temporal distribution of Scirtothrips dorsalis (Thysanoptera: Thripidae) and their natural enemies in Florida strawberry fields.

Given the recent invasion of Scirtothrips dorsalis Hood in North America, there is limited information regarding their distribution and population dynamics in cultivated small fruit crops. Therefore, we investigated the spatial and temporal distribution of S. dorsalis and their natural enemies in commercially produced strawberry fields in Florida. During 2 consecutive strawberry production seasons, 4 and 6 geographically separated strawberry fields were sampled and were divided into grids with 30-40 sampling points per field. At each sampling point, 4-5 leaf and flower samples were collected, and sticky traps were deployed. We quantified the occurrence of S. dorsalis as well as potential natural enemies, including Orius spp., Geocoris spp., and other predators such as long-legged flies. During both years, most of the S. dorsalis and natural enemies were found on field borders, and counts progressively diminished further into the interiors of plots and away from field edges. Cluster and outlier analysis revealed that S. dorsalis formed statistically significant clusters and that these "hot spots" remained in the same general locations throughout the season. There was a strong relationship between the occurrence of natural enemies and the presence of S. dorsalis, but the number of natural enemies was generally low compared to S. dorsalis. Our results indicate that targeting field borders for chemical control or planting strawberries away from natural areas containing potential alternative hosts for thrips may be an effective strategy for reducing agricultural inputs; however, future field assessments are needed to determine if these methods could replace the treatment of entire fields.

Delayed spinetoram application is useful in managing Scirtothrips dorsalis Hood (Thysanoptera: Thripidae) in Florida strawberry.

Scirtothrips dorsalis Hood (Thysanoptera: Thripidae) is an invasive, early-season pest of strawberry in Florida, causing feeding injury to young foliage that results in stunted plant growth and yield loss. Spinetoram, an effective insecticide for thrips pests with up to 3 applications per season permitted in strawberry, is often applied repeatedly during the early-season (Oct-Nov) to manage S. dorsalis, leaving few or no applications for flower thrips pests later in the season (Dec-Mar). Therefore, new strategies are needed to manage S. dorsalis with less insecticide, with the hypothesis that the first insecticide application can be delayed because young strawberry plants can compensate for minor feeding injury without compromising strawberry yield. Experiments conducted in strawberry field plots in Balm, FL, during 2018 and 2019 showed that delaying a spinetoram application for 14 days after infesting a plant with zero, 5, 10, or 20 S. dorsalis adults did not reduce the plant vigor and yield compared to spinetoram application after 4 days. Furthermore, young plants recovered from injury (10-30% bronzing injury on leaf veins and petioles) due to 1 or 2 S. dorsalis adults or larvae per trifoliate. A strategy of delaying the first spinetoram application when plants have 4-5 trifoliates should help reduce the number of insecticide applications needed for S. dorsalis management and reserve spinetoram applications for later in the season. Lower input costs in Florida strawberry without compromising yields due to thrips damage will improve the economics and sustainability of production systems.

Habitat and vertical stratification affect capture of stink bugs (Hemiptera: Pentatomidae) and biological control of the invasive brown marmorated stink bug.

Spatiotemporal distribution of stink bugs (Hemiptera: Pentatomidae) and their natural enemies across farmscapes has been studied in more detail recently. However, the impact of plant height on vertical stratification of stink bugs and their natural enemies is rarely addressed across these diverse habitats. In this study, we examined capture of native stink bugs, the invasive brown marmorated stink bug, Halyomorpha halys (Stål)(Hemiptera:Pentatomidae), and a predaceous wasp, Astata occidentalis Cresson (Hymenoptera: Sphecidae) in pheromone-baited traps, in 2 habitats, woodlands of mostly deciduous trees mixed with some conifers and pecan orchards, in addition to their vertical stratification (0-13.7 m) at increasing heights. Furthermore, the effects of canopy height and habitat on H. halys egg mass predation and parasitism were evaluated. Adult H. halys were abundant in both habitats, but more nymphs were captured in pecan orchards. The same pattern was found for adult Euschistus servus (Say) (Hemiptera:Pentatomidae), Thyanta custator McAtee (Hemiptera:Pentatomidae), and A. occidentalis. In contrast, adult E. tristigmus (Say) (Hemiptera:Pentatomidae) and Chinavia hilaris (Say) (Hemiptera:Pentatomidae) were more abundant in woodlands. More nymphal H. halys and adults of E. servus, T. custator, and A. occidentalis were captured in ground traps than canopy traps in pecan. More adult and nymphal H. halys were captured at varying heights in the woodland canopy compared to near the ground as were adult E. tristigmus and C. hilaris. Both parasitism and predation occurred in woodland and pecan canopies. However, in one test we found that parasitism of H. halys egg masses occurred more often in the upper tree canopy, and more parasitism was detected in woodland than orchard habitat. In 2 tests, predation was higher in woodlands than pecan orchards. These results will aid in optimizing conservation biological control tactics in these habitats.

Potential of UV-C for management of two-spotted spider mites and thrips in Florida strawberry.

BACKGROUND: Major pests of Florida strawberry (two-spotted spider mites, Tetranychus urticae Koch; chilli thrips, Scirtothrips dorsalis Hood; and western flower thrips, Frankliniella occidentalis Pergande) are difficult to manage using only conventional chemical control. Previous research has demonstrated high mortality of T. urticae eggs after exposure to ultraviolet B (UV-B) light. Additionally, ultraviolet C (UV-C) light has been shown to suppress powdery mildew in strawberry at doses between 85 and 200 J m-2 with no damage to the plant. Therefore, UV-C may also have the potential to be used as an integrated pest management tool for arthropod pests of strawberry. The objectives of this study were to: (i) determine the effect of UV-C on T. urticae, S. dorsalis, and F. occidentalis natural populations in open-field strawberry; and (ii) determine the effect of UV-C on T. urticae egg hatch after application in open-field strawberry. Field studies were conducted during the 2019-2020 and 2020-2021 strawberry seasons in Florida, USA. Four treatments were compared: (i) foliar application of spinetoram in response to natural pest pressure; (ii) application of UV-C 200 J m-2 twice a week; (iii) application of UV-C 350 J m-2 twice a week; and (iv) a non-treated control. RESULTS: In the field trials, suppression of T. urticae was observed at 350 J m-2 in 2020-2021. In the other field trials, no effect was observed due to low natural infestations. No negative impact on yield was observed from UV-C applications. CONCLUSION: UV-C shows promise as a component of an integrated pest management program for T. urticae in strawberry. © 2022 Society of Chemical Industry.

Host plant resistance, foliar insecticide application and natural enemies play a role in the management of Melanaphis sorghi (Hemiptera: Aphididae) in grain sorghum.

The invasive Melanaphis sorghi (Theobald; =Melanaphis sacchari Zehntner) is a serious pest of sorghum production in the southern USA. Demonstration of technologies that provide effective control is key to management of this pest. Here, we investigated the effect of host plant resistance (resistant cultivar: DKS37-07 and susceptible cultivar: DKS53-53) and a single foliar insecticide (flupyradifurone: Sivanto Prime) application on M. sorghi infestations and the role of natural enemy populations in grain sorghum production across five locations in four states in southeastern USA. Foliar insecticide application significantly suppressed M. sorghi infestations on both the resistant and susceptible sorghum cultivars across all locations. Planting the host plant resistant cultivar (DKS37-07) significantly reduced aphid infestation across all locations. Plant damage ratings did not vary widely, but there was generally a positive association between aphid counts and observed plant damage, suggesting that increasing aphid numbers resulted in corresponding increase in plant damage. Planting a host plant resistant cultivar and foliar insecticide application generally preserved grain yield. Both sorghum hybrids supported an array of different life stages of natural enemies (predators [lady beetle larvae and adults; hoverfly larvae and lacewing larvae] and parasitoids [a braconid and aphelinid]) for both the sprayed and non-sprayed treatments. We found a strong and significant positive relationship between the natural enemies and the M. sorghi infestation. Results suggest that planting a host plant resistant cultivar and the integration of natural enemies with insecticide control methods in the management of M. sorghi is central to the development of an effective pest management strategy against this invasive pest.

Arthropod Pest Management in Strawberry.

The strawberry crop endures economic losses due to feeding injury from a number of phytophagous arthropod pests. A number of invasive pests have posed challenges to crop protection techniques in the strawberry cropping system recently. It is increasingly evident that sole reliance on chemical control options is not sustainable. In this review, current challenges and advances in integrated pest management of various strawberry pests are presented. Key pests discussed include thrips, mites, lygus bug, spotted wing drosophila, seed bug, weevils, aphids, whiteflies, and armyworms. Several integrated pest management techniques that include use of intercropping, resistant cultivars, irradiation with gamma rays, use of spectral sensitivity of pests, biological control agents and natural enemies, and biorational pesticides have recently been reported to be useful in managing the various strawberry pests. With the increase in world production of strawberry, several techniques will be necessary to manage the pest complex of strawberry.

Spatio-Temporal Distribution and Fixed-Precision Sampling Plan of Scirtothrips dorsalis (Thysanoptera: Thripidae) in Florida Blueberry.

Scirtothrips dorsalis Hood is an invasive and foliar pest of Florida blueberry that reduces plant growth by feeding on new leaf growth. A sampling plan is needed to make informed control decisions for S. dorsalis in blueberry. Fourteen blueberry fields in central Florida were surveyed in 2017 and 2018 after summer pruning to determine the spatial and temporal distribution of S. dorsalis and to develop a fixed-precision sampling plan. A sampling unit of ten blueberry shoots (with four to five leaves each) was collected from one blueberry bush at each point along a 40 × 40 m grid. Field counts of S. dorsalis varied largely ranging from zero to 1122 adults and larvae per sampling unit. Scirtothrips dorsalis had aggregated distribution that was consistent within fields and temporally stable between summers, according to Taylor's power law (TPL) (aggregation parameter, b = 1.57), probability distributions (56 out of 70 sampling occasions fit the negative binomial distribution), Lloyd's index (b > 1 in 94% occasions), and Spatial Analysis by Distance IndicEs (31% had significant clusters). The newly developed fixed-precision sampling plan required 167, 42, seven, or three sampling units to estimate a nominal mean density of 20 S. dorsalis per sampling unit with a precision of 5%, 10%, 25%, or 40%, respectively. New knowledge on S. dorsalis distribution will aid in evaluating the timing and effectiveness of control measures.

The Short-Range Movement of Scirtothrips dorsalis (Thysanoptera: Thripidae) and Rate of Spread of Feeding Injury Among Strawberry Plants.

Scirtothrips dorsalis Hood infest strawberry (Fragaria x ananassa Duchesne, Rosaceae) fields from nearby crop fields and surrounding vegetation and cause injury to plants by feeding on young leaf tissues. Greenhouse and field studies were conducted to determine the short-range movement of S. dorsalis to assess the risk of an early S. dorsalis population to spread to adjacent plants. In a greenhouse, 25 potted strawberry plants were arranged in two concentric rows around a central plant, where plants in inner rows were 20 cm, and those in the outer rows were 40 cm from the central plant. In the field, 20 strawberry plants were arranged in two beds (90 cm apart), ten in each bed, and five plants in each row, with plants 30 cm apart. White sticky cards were placed at 60-120 cm from the central plant. Fifty S. dorsalis adults were released on a centrally located plant, and the numbers of S. dorsalis adults and larvae and feeding injury were recorded for 9-17 d on adjacent plants and sticky cards. Results showed that significantly more S. dorsalis adults and larvae remained on the initially infested plant compared to adjacent plants, although few adults were found up to 120 cm on sticky cards. The rate of spread of feeding injury was low with slight bronzing injury (<10% injury) on adjacent plants by 14-17 d. Since most S. dorsalis remained on initially infested plants for at least 2 wk, it is feasible to delay management actions and 'rescue' plants around a plant with minor injury symptoms.

Role of Tillage, Thiamethoxam Seed Treatment, and Foliar Insecticide Application for Management of Thrips (Thysanoptera: Thripidae) in Seedling Cotton.

Thrips are early-season pests of cotton and can cause yield and stand losses if not managed. Strip tillage into a winter cover crop, use of a neonicotinoid seed treatment, and foliar insecticide applications are all reliable pest management tactics, but how these methods interact with each other in a thrip-cotton agroecosystem needs to be further understood. A 2-yr field study was conducted to compare thrip counts and thrip-induced plant injury as a function of tillage practice (conventional vs strip tillage with heavy rolled rye), thiamethoxam seed treatment, and foliar insecticide application for managing thrips in cotton. Adult and nymph density, seedling biomass, true leaf formation, stand count, and lint yield were assessed. Results indicate that heavy rolled rye was effective for mitigating thrips on seedling cotton. On conventionally tilled fields, the neonicotinoid seed treatment and a foliar insecticide application were necessary for maximizing yield. Spinetoram was more efficacious than either acephate or cyantraniliprole for management of immature thrips; however, there were no yield effects attributed to foliar insecticide application. These data suggest that growers can mitigate early-season thrips using both cultural and chemically based management tactics.

Ecology and Management of Kudzu Bug (Hemiptera: Plataspidae) in Southeastern Soybeans.

Kudzu bug, Megacopta cribraria Fabricius (Hemiptera: Plataspidae), is an invasive exotic pest of soybeans that has been present in the southeastern United States since 2009 and has been rapidly spreading through soybean-producing states. Their primary reproductive hosts in the United States are soybean, kudzu, pigeon pea, black eye pea, lima bean, pinto bean, wisteria, white sweet clover, white clover, red clover, alfalfa, perennial peanut, and American joint vetch. In soybeans, the kudzu bug feeds on vascular fluids at the stem, petiole, and nodes, causing yield losses of up to 60%. The current management recommendation for this pest includes spraying of pyrethroids such as bifenthrin, but this method is not environmentally friendly, as this negatively impacts beneficial insect populations. Sustainable management tactics, including the development of economic thresholds for insecticide sprays, assessing the spatial and temporal distribution of this pest, manipulating cultivation practices, use of biological control, and host plant resistance, are currently being explored. We present an overview of the ecology of the kudzu bug in soybeans and available management tactics to assist with the management of this potentially devastating pest of soybeans as it spreads westward.