Search

Tomato chlorotic spot virus (TCSV) is an orthotospovirus that causes a devastating disease in tomato (Lycopersicon esculentum Miller). TCSV emerged recently in South Florida. Studies were conducted in three commercial tomato fields in Miami-Dade County, Florida during the vegetable-growing seasons from October to April in 2015 through 2017. Each year, data were collected at 3, 6, and 9 wk after transplanting at various distances from the edges of each fields. Based on 3 yr total samples, three species of thrips were commonly observed melon thrips, Thrips palmi Karny (62.16 ± 0.79%), being the most abundant species followed by common blossom thrips, Frankliniella schultzei Trybom (21.55 ± 0.66%), and western flower thrips, Frankliniella occidentalis (Pergande) (16.26 ± 0.61%). Abundance of all thrips and TCSV infected plants was high at the edge of a tomato field 3 wk after transplanting with significantly fewer infected plants toward the center of the field. The distribution patterns of thrips and TCSV in various fields were mostly regular and aggregated across the sampling dates during the study period. Abundance of TCSV symptomatic plants and thrips species was high at the edge of the field and increased over time. The number of samples required to accurately determine population density of thrips was calculated by using three precision levels (0.10, 0.20, 0.30) at three predetermined densities of thrips (0.10, 0.20, and 0.40 per sample). This information will provide guidelines to growers, crop protection personnel, agricultural scouts, and researchers to develop a sustainable thrips and tospovirus management program.

Melon thrips, Thrips palmi Karny (Thysanoptera: Thripidae), is a serious pest of vegetable, ornamental, and fruit crops. As a potential component of an integrated pest management (IPM) program, different plastic mulches including white-on-black, black-on-white, black-on-black, two metalized ultraviolet (UV)-reflective mulches, and a no mulch control were evaluated for managing T. palmi on six field-grown vegetable crops (eggplant, cucumber, squash, snap bean, Jalapeno pepper, and tomato) during the Fall of 2015 and 2016. Metalized reflective mulch significantly reduced the number of T. palmi in all vegetable crops compared with the other treatments. The highest numbers of T. palmi were observed on the white-on-black mulch and control treatments. The numbers of adults and larvae were highest on eggplant followed by cucumber, snap bean, squash, and Jalapeno pepper. The lowest numbers of T. palmi were observed on tomato plants. This study indicated that growing vegetable crops on metalized mulch is an effective method of reducing T. palmi populations in vegetable crops and should be considered in IPM programs for this insect species.

Cold tolerance of the palm thrips, Thrips palmi Karny, was investigated to predict its survival in field during winter. Supercooling points of T. palmi were varied among the developmental stages and ranged from -26.4 to -18.4°C. However, the cold injuries occurred above supercooling points in terms of higher mortality. The exposure to subzero temperatures (-5° to -15°C) resulted in significant mortalities to all developmental stages of T. palmi. A preexposure to a low temperature (4°C) for 7 h significantly increased the cold tolerance of all stages of T. palmi with respect to survival at -10°C and supercooling capacity. The rapid cold hardening (RCH) was dependent on the duration of the preexposure period at 4°C in adult stage. Polyol and sugar analysis using an high-performance liquid chromatography analysis showed that 4°C preexposure caused accumulation of glycerol, trehalose, mannitol, and mannose in the adults. The increase in trehalose levels was more significant than the others. This study suggests that all stages of T. palmi are able to become cold-hardy by RCH, in which several polyols and sugars may play crucial roles as cryoprotectants.

Development time and life table parameters of Thrips palmi Karny, a pest new to the continental United States, were measured at 3 temperatures on 4 host plants. Net reproductive rate was the highest because of greatest survival and highest egg production when thrips were reared at 26°C on winter melon, Benincasa hispida (Thunb.) Cogn., eggplant, Solanum melongena L., and cucumber, Cucumis sativus L. , compared with bell pepper. However, because of shorter development time, the intrinsic rates of natural increase for T. palmi were highest when individuals were reared at 32°C on these 3 host plants. Although development times were similar on all 4 hosts at 26°C, survival and reproduction were much lower for thrips reared on bell pepper, Capsicum annuum L. , leaves. At 15 and 32°C, these differences were even greater, with only 40 and 48% of thrips reared on bell pepper surviving at the respective temperatures. T. palmi was able to tolerate the low temperature (56% mortality when held at O°C for 15 h) much better than the high temperature (100% mortality at 40°C for 15 h), which may partially explain why T. palmi populations are high in winter and spring and low in the summer in Florida. This study provides information needed to understand population dynamics of thrips in important vegetable crops, information which will be valuable in developing and evaluating cultural and biological controls for this extremely damaging pest.

After rice, Oryza sativa L., harvest, sowing cowpeas, Vigna unguiculata (L.) Walp., by minimum-tillage methods among standing stubble reduced colonization of bean fly, Ophiomyia phaseoli (Tryon), thrips, Thrips palmi Karny, and leafhopper, Amrasca bigutulla bigutulla (Ishida) during the first 2 weeks of crop growth. Thrips and leafhopper, but not bean fly, were also negatively affected by rice straw mulch covering high-tillage plots with the rice stubble plowed under. We hypothesize that the rice stubble and straw mulch, by covering bare soil, interfered with visual cues used by the migratory thrips and leafhopper to locate a favorable habitat. To explain the negative effect of standing rice stubble on bean fly colonization, we hypothesize that the adults first select the topmost crop canopy—the site of newly formed leaves—and plant host suitability is determined after landing. When the stubble is taller than cowpeas, most bean flies repeatedly alight on the nonhost, leaving the field without coming in contact with the host. This effect reverses after the cowpeas grow to the height of the stubble. Cowpeas established in plow furrows opened between rows of rice stubble 20 to 25 cm tall offered the best combination of insect control and high yield.

Colonization of lettuce and five common weed species by thrips was studied in lettuce fields at Kula, Hawaii. Frankliniella occidentalis (Pergande), a vector of tomato spotted wilt virus, was the most abundant thrips species (82.4%of total) of the twelve species collected. Nonflowering lettuce, Lactuca sativa var. longifolia Lam., was less attractive to thrips than flowering plants of the weed species. Among weeds in flower, Verbesina enceliaides (Cav.) Benth & Hook. ex Gray, Malva parviflora L., and Amaranthus hybridus (L.) Rob. were most attractive to thrips. However, among nonflowering stages, V, encelioides attracted the fewest thrips and only A. hybridus and M. parviflora were more attractive than lettuce. For each weed species, flowering individuals attracted more thrips than plants with flowers removed.