Dakshina R. Seal

DISTRIBUTION OF CHILLI THRIPS, SCIRTOTHRIPS DORSALIS (THYSANOPTERA: THRIPIDAE), IN PEPPER FIELDS AND PEPPER PLANTS ON ST. VINCENT

Abstract Scirtothrips dorsalis Hood is a significant pest of various vegetable, ornamental, and fruit crops. Its biology and management are little known in the agro-ecosystems in western hemisphere. We investigated distribution patterns of S. dorsalis in fields and plants of ‘Scotch Bonnet’ pepper, Capsicum chinense Jacq., on St. Vincent in 2004 and 2005. Scirtothrips dorsalis adults and larvae were abundant on top leaves of the pepper plants followed by middle leaves, lower leaves, flowers and fruits. The spatial distribution of S. dorsalis adults and larvae on pepper was analyzed by using Taylor’s power law and Iwao’s patchiness regression. These results were compared with the Index of Dispersion, Mean Crowding, Green’s Index and Lloyd’s Patchiness Index. In Oct 2004, the distributions of S. dorsalis adults on the top leaves were aggregated in 24- and 48 m2-plots. In the smaller plots adults were distributed in a regular pattern. The distribution of larvae on the top leaves was aggregated irrespective of plot size. In Williams Farms on Mar 2005, the distribution of adults was aggregated in the largest plots (48 m2). In all other plots, the distribution of adults was regular as described by Taylor’s power law and Iwao’s patchiness regression. In Baptist Farms on March 2005, the distribution of adults according to both models was aggregated irrespective of plot size. The optimum number of samples from a 24 m2 plot was 9 with a precision of 40% when there were 0.5 individuals per top leaf of ‘Scotch Bonnet’ pepper. However if the estimated density was 2 individuals per top leaf, 9 samples from a same sized area were sufficient at the 10% precision level. This information is essential to the development of a scouting-based integrated management program for S. dorsalis. Based on this information, incipient infestations of S. dorsalis easily can be detected by examining young top leaves.

Biological Parameters of Scirtothrips dorsalis (Thysanoptera: Thripidae) on Selected Hosts

ABSTRACT Since its establishment in Florida in 2005, Scirtothrips dorsalis Hood, a highly polyphagous species, has become an economically important pest of ornamental plants and a potentially significant pest of vegetable and fruit crops. Fruit and vegetable production in Florida is trending toward significant adoption of organic methods and use of widely dispersed small fields in rapidly urbanizing landscapes. Landscape plants may serve as refugia from which S. dorsalis recruits can disperse to nearby fruit and vegetable plantings. Therefore, information on this pests biology including how it is affected by various host species is needed to develop effective integrated pest management (IPM) programs. In the greenhouse and laboratory condition, we studied the effects of various host plants, development, diel flight activity, oviposition, and demographics of S. dorsalis. The pest preferred Jalapeño pepper and Knockout rose over the other hosts, and it was most active between 1000 and 1600 hours EST. Irrespective of the host species, the duration of each of the immature stadia varied within a narrow range, and their respective sizes were quite similar. Demographic parameters quantified included gross reproduction rate (GRR), net reproductive rate (Ro), intrinsic rate of increase per day (rm), finite rate of increase per day (&lgr;), and mean generation time (T). The pest population may increase by a factor of ≈ 1.09/d, so that it may double in 8 or 9d. The above information should be helpful in the development of sound programs to manage S. dorsalis on various crops and in the formulation of detection strategies by quarantine officers.

ABUNDANCE OF FRANKLINIELLA SCHULTZEI (THYSANOPTERA: THRIPIDAE) IN FLOWERS ON MAJOR VEGETABLE CROPS OF SOUTH FLORIDA

ABSTRACT The flower thrips, Frankliniella schultzei (Trybom), has only recently been recognized as a pest of vegetable crops in south Florida. Little is known about its abundance and impact on vegetable crops in this region. Therefore, a field experiment was conducted comparing F. schultzei abundance in blooms of the 5 key fruiting vegetable crops grown in south Florida, i.e., cucumber, pepper, snap bean, squash and tomato. Mean number of F schultzei larvae was highest in cucumber flowers (78.1 larvae/5 flowers) and lowest in bean flowers (5.1 larvae/5 flowers). However, adults of F schultzei were most numerous in tomato flowers (27.5 adults/5 flowers) and least numerous in snap bean flowers (3.5 adults/ 5 flowers). Neither larvae nor adults of F. schultzei were found in pepper flowers in the present study. The flower samples collected from 5 vegetable crops were also found to be infested with 3 other thrips species. Amongst these, Thrips palmi Karny was the second most abundant thrips species. Frankliniella occidentalis (Pergande) was found in low numbers on all crops except pepper, and Frankliniella fusca (Hinds) was found only on tomato. The above information should be useful in the development of monitoring programs, design of pest management strategies and in the timely application of preventive or suppressive measures in south Florida.

New tropical fruit hosts of Scirtothrips dorsalis (Thysanoptera: Thripidae) and its relative abundance on them in South Florida.

The chilli thrips, Scirtothrips dorsalis Hood, has long been a pernicious pest of cotton and various ornamental, vegetable, and fruit crops including citrus in southern and eastern Asia, Af rica, and Oceania (Amin 1979; Amin et al. 1981; Ananthakrishnan 1993) where it is known to kill newly emerged seedlings, severely distort leaves, scar the surface of fruits of its hosts, and also vec tor a number of major plant pathogens. Scirto thrips dorsalis has an extensive host range, and in recent decades has expanded its distribution from south Asia to Australia, the Middle East, Africa, the Caribbean and the Americas (EPPO/ CAB 2003; Hodges et al. 2005). Worldwide it at tacks more than 200 plant species, belonging to 70 different families (GPDD 2011). In Florida since its establishment in 2005, S. dorsalis has been reported developing on 38 dif ferent ornamental crop species (Klassen et al. 2008; Osborne 2009; Seal & Kumar 2010) and on pepper. In Aug 2010 we discovered this pest infesting 11 different tropical fruit species at a commercial nursery in Homestead, Miami-Dade County, Florida. This is the first report of S. dor salis damaging tropical fruit species on a signifi cant scale in Florida.

Assessing abundance and distribution of an invasive thrips Frankliniella schultzei (Thysanoptera: Thripidae) in south Florida

Within-plant and within-field distribution of larvae and adults of an invasive thrips species, Frankliniella schultzei (Trybom) on cucumber, Cucumis sativus L. was studied in 2008 and 2009 in Homestead, Florida. The majority of thrips were found inhabiting flowers of cucumber plants and little or none was found on the other parts of the plant. Thrips were aggregated in the field, as indicated by the two regression models, Taylors power and Iwaos patchiness regression. Iwaos patchiness regression provided a better fit than Taylors power law. The distribution was clumped during the initial stages of infestation at the edges of the field and became random thereafter. However, with increase in population density, thrips again formed aggregates in the field. Based on the average pest density per flower in a ∼0.25-ha field, minimum sample size (number of flowers) required at the recommended precision level (0.25) was 51. The number of samples required at two levels of predetermined pest density was also calculated, which would help growers in collecting optimum number of samples required to determine the correct threshold level of pest in fields. Results from seasonal abundance indicated that density of thrips peaked during the fifth week of sampling with an average of 25 and 34 adults per ten flowers during autumn 2008 and 2009, respectively. Results from these studies will help growers and extension personnel in understanding the abundance and distribution of F. schultzei in the field, which are important components required in developing a sound management program.

New Report of Chaetopsis massyla (Diptera: Ulidiidae) as a Primary Pest of Corn in Florida

ABSTRACT The picture-winged fly Euxesta stigmatias Loew (Diptera: Ulidiidae) has been a serious pest of sweet corn in Florida since the 1930s and had been considered the only fly infesting Florida corn. In a sweet corn variety trial to evaluate E. stigmatias resistance in 2007, adult Chaetopsis massyla (Walker) (Diptera: Ulidiidae) was reared from the ears. Choice and no-choice trials were conducted in 2007 and 2008 to determine the pest nature of C. massyla on corn. In no choice tests, C. massyla pairs were caged on uninfested corn ears in green house and field trials. In choice tests, field collected corn ears were held for fly emergence. No choice tests showed that C. massyla could infest and complete development in ears that had no previous damage. Chaetopsis massyla emerged from corn ears with and without prior infestation by other insect species in choice tests. Subsequently, C. massyla were reared from corn ears collected from locations throughout the major sweet corn growing region of southern Florida. Therefore, we present what we believe to be the first report of C. massyla as a primary pest of corn ears in Florida and in the United States of America.

Influence of Temperature and Host on Life History Parameters of Catolaccus Hunteri (Hymenoptera: Pteromalidae)

Abstract Catolaccus hunteri Crawford is an external parasitoid of cryptic Coleoptera, particularly of Bruchidae and Curculionidae in flowerbuds, small fruits, and seeds. It is the most common parasitoid of the pepper weevil, Anthonomus eugenii Cano, in the United States, Mexico, and elsewhere, and was introduced from Guatemala to Hawaii for control of this pest. Studies were conducted to assess effects of temperature and host on life history parameters of C. hunteri as a step toward eventual mass rearing and inoculative release for pepper weevil control. Oviposition, postovipostion period and adult longevity were shorter at 30°C than at 20 or 25°C. Mean number of eggs oviposited per female was greater at the lower temperatures than at the highest temperature. Duration of all development stages was shorter at 30°C than at 20 and 25°C. Developmental period of C. hunteri was longer and adult longevity was shorter on boll weevil, Anthonomus grandis Boheman, than any other host. Female wasps laid most eggs on the cowpea weevil, Callosobruchus maculatus (F.), larvae. Transferring of C. hunteri reared on C. maculatus to pepper weevil or boll weevil caused a reduction in the mean number of eggs/female. Age-specific life tables and age-specific fecundity for C. hunteri were analyzed using three constant temperature regimes and five sources of host. These tables were used to calculate the innate capacity of natural increase (rm), the finite rate of increase (λ), the mean generation time (T), the net reproduction rate (Ro), and the gross rate of reproduction. The results indicate that C. hunteri populations are capable of increasing in all of the environmental conditions tested in the current study. The optimum temperature for population increase for C. hunteri is 25°C. With respect to host suitability, greater numbers of C. hunteri female progeny were produced when this parasitoid was reared constantly and invariably on C. maculatus larvae than on any other host.

An Overview of Chilli Thrips, Scirtothrips dorsalis (Thysanoptera: Thripidae) Biology, Distribution and Management

The industrial revolution, globalization and international trade liberalization are some of the important events that have afforded vast opportunities for invasive insect species to establish in new territories [1]. These invasive species, facing no challenge by their natural enemies, thrive well in the new environment [2]. In addition to the disturbance they cause to the biodiversity, pest invasion in any country results in increased pressure on biosecurity, national economy, and human health management systems [1, 3, 4]. Apart from economic loss in managing them, these pests pose a significant detrimental impact on tourism and recreational value of the region, which further adds in indirect economic damage to the nation [5]. Of this large group of invasive pests, thrips are one of the most important members. The invasive status gained by thrips across the globe is due to their high degree of polyphagy, wide host range and easy dispersal that can be anthropogenic or natural (wind-mediated).

Alternative plants for development of picture-wingedfly pests of maize

Eleven species of picture‐winged flies (Diptera: Ulidiidae: Lipsanini) have been reported attacking maize [Zea mays L. (Poaceae)] ears in the Americas. Four of these species are sweet corn pests in America north of Mexico: Chaetopsis massyla (Walker), Euxesta annonae (Fabricius), E. eluta Loew, and E. stigmatias Loew. Adults of these four species appear at the beginning of each season following maize‐free periods, suggesting other plants act as food sources for maintenance and development of these flies. Studies were conducted in Florida, USA, to evaluate the suitability of several crop and non‐crop plants commonly occurring near maize plantings as developmental hosts for these flies. Laboratory trials were conducted using laboratory colonies of C. massyla, E. eluta, and E. stigmatias to determine their developmental rates and pupal survivorship on roots, stems, leaves, or fruits of 14 crop and weed species. All three fly species completed development on all tested crops (Brassica oleracea L., Capsicum chinense Jacquin, Capsicum annum L., Carica papaya L., Persea americana Mill., Raphanus sativus L., Saccharum officinarum L., and Solanum lycopersicum L.) and weed species [Amaranthus spinosus L., Portulaca oleracea L., Sorghum halepense (L.), and Typha spp.], except for Daucus carota L. roots and Solanum tuberosum L. tubers. Findings of the current study suggest that the presence of multiple host crops in areas surrounding maize fields may help explain the occurrence of these maize‐infesting ulidiids immediately after prolonged absences of maize.

Distribution of Picture-Winged Flies (Diptera: Ulidiidae) Infesting Corn in Florida

ABSTRACT The picture-winged fly Euxesta stigmatias Loew (Diptera: Ulidiidae) has been a serious pest of sweet corn (Zea mays L.) in Florida since 1930. Several other species in the family are known to infest corn grown in the Caribbean, Central America, and South America. Surveys were conducted throughout Florida to evaluate species richness and distribution of corn-infesting Ulidiidae. Adults were sampled with sweep nets and reared from fly larvae-infested corn ears collected from representative corn fields in 16 and 27 counties in 2007 and 2008, respectively. Four Ulidiidae species were found in corn fields using both sampling techniques. Euxesta eluta Loew and Chaetopsis massyla (Walker) were found throughout the state on field and sweet corn. Euxesta stigmatias was only found in Martin, Miami-Dade, Okeechobee, Palm Beach, and St. Lucie Counties on field and sweet corn. Euxesta annonae (F.) was found in sweet corn in Miami-Dade, Okeechobee, and Palm Beach Counties, but field corn was not sampled in these counties. Euxesta eluta, E. stigmatias, and C. massyla were collected from corn throughout the corn reproductive stage. Raising adults from fly larvae-infested ears provided the best method for assessing rates of ear infestation and species richness. Sweep netting did not provide reliable information on the presence or species composition of ulidiid species infestation. We report for the first time E. annonae and E. eluta as pests of corn in Florida and the USA.