Garima Kakkar

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.

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).

Temporal Assessment of Molting in Workers of Formosan Subterranean Termites (Isoptera: Rhinotermitidae).

Abstract Molt frequency of workers in laboratory-reared juvenile colonies and foraging population from field colonies of Coptotermes formosanus Shiraki was determined using planar arenas in laboratory. Given that, chitin synthesis inhibitor (CSI)-incorporated baits disrupt the molting process of workers that comprises the major population of a termite colony, temporal assessment of molting frequency in workers can give insights into potential methods of reducing the time to eliminate a CSI-baited colony. In our study the 10-d observation of juvenile colonies of C. formosanus suggested average daily molting incidence of workers in a colony is 1.7 ± 0.3% (mean ± SD). The results from a time lapse study on foraging population of workers showed that on average there is a 44-d intermolt period for second-instar workers molting to third instar and 45 d for third-instar workers molting to fourth instar. At low temperature (21 °C), molting frequency of workers (0.6% per day) was significantly lower than that of workers at 27 °C (2.2% per day). Information from this study suggests that time to molt is an important component of total time for eliminating colonies treated with CSI baits and reduction in time lapse between two consecutive molts may reduce the time required for colony elimination.

Abundance of Adventive Thrips palmi (Thysanoptera: Thripidae) Populations in Florida During the First Sixteen Years §

ABSTRACT Thrips palmi Karny (Thysanoptera: Thripidae), invaded Miami Dade-county in 1990 and caused significant economic damage by defoliating various vegetable crops. It commonly occurs on the abaxial surface of host leaves where eggs are deposited individually inside the leaf tissues. Highest abundance of T. palmi was recorded on bean and eggplant in 1991–1994 in Tropical Research and Education Center research plots and commercial fields in MiamiDade County. Density of T. palmi decreased significantly in subsequent years after the use of spinosad and other effective chemical insecticides. Thrips palmi populations increased in 2008 in spite of use of spinosad and showed increasing pattern causing crops loss at economic level. Orius insidiosus Say population was low in both TREC research fields and commercial fields due to harsh chemical management program, where insecticides belonging to various chemical classes were used alone (TREC fields) or in combination (commercial fields) to control T. palmi and other insect pests. None of the commonly used available insecticides alone or in combination provided satisfactory control of T. palmi in the early stage of invasion. Amongst various insecticides tested spinosad provided significant control of T. palmi on the crops until 2008 after which there was reduced effect of the chemical due to frequent use for managing multiple pests.

Foraging Distance and Population Size of Juvenile Colonies of the Formosan Subterranean Termite (Isoptera: Rhinotermitidae) in Laboratory Extended Arenas

Abstract The relationship between colony size and foraging distance was examined in extended foraging arenas with juvenile colonies of the Formosan subterranean termite, Coptotermes formosanus Shiraki. Our results showed that as long as royal pairs are present, larger colonies foraged at longer distances, and the oldest workers distributed farther away from the central nest. The results agree with the scaling model that predicts a large foraging range for animals of larger body size. An analysis of published data from population survey studies and field trials of bait toxicants showed that field colonies of the eastern subterranean termite, Reticulitermes flavipes (Kollar), follow the scaling model, while C. formosanus colonies were inconsistent with the model prediction. Reasons for the inconsistency with field data of C. formosanus are discussed.

Postecdysis Sclerotization of Mouthparts of the Formosan Subterranean Termites (Isoptera: Rhinotermitidae)

Abstract In termites, it is challenging to recognize the incidence of molting in workers because of their successive stationary molt, asynchronous molting among individuals, cryptic behavior, a soft and poorly sclerotized cuticle, and they immediately consume the shed exuvia of nestmates. This study describes a method in which the degree of sclerotization of the mouthparts in newly molted workers of the Formosan subterranean termite can be quantified and used to determine if an individual has recently molted, within a 36-h time frame. Changes in the tanning of mouthparts over time were used as a measure of the index of sclerotization in workers postmolting. Upon ecdysis, the primary point of articulation of the mandible already initiated sclerotization, which may allow the movement of the mandibles during the shedding of the exuvium. The sclerotization of the secondary point of articulation and the mandibular teeth, and the width of sclerotization of the mandibles, progressively increased until reaching a plateau around 36-h postecdysis, which imply that workers can regain some level of activity as early as 2 d after ecdysis. Our observations allowed for the determination of variables for the sclerotization of the mouthparts to easily identify workers that recently molted, and this method will be useful in future studies that focus on the molting activity of workers over time and space within a termite colony, in the scope of improving current control strategies for termite pests.

Common Blossom Thrips, Frankliniella schultzei (Thysanoptera: Thripidae) Management and Groundnut Ring Spot Virus Prevention on Tomato and Pepper in Southern Florida

Abstract The common blossom thrips, Frankliniella schultzei (Trybom), has been recently reported as an agronomic pest in South Florida. It poses a serious threat to tomato and pepper growers due to its ability to transmit Groundnut ring spot virus (GRSV). In the wake of the current problem 3 trials were undertaken to control F. schultzei using conventional and novel insecticides of different modes of action. Specifically, the efficacies of neonicotinoid, diamides, spirotetramat, spinosyn/spinosad and Chenopodium ambrosioides were evaluated with the aim of controlling F. schultzei and minimizing the transmission of the virus. In the first trial, imidacloprid (IRAC Group 4) applied at planting as a soil drench followed by drip irrigation application of cyazypyr showed some reduction of the F. schultzei population and of the transmission of GRSV on tomato. The change in the method of application of cyazypyr from drip irrigation to direct application on the foliage in the second trial improved both the control of F. schultzei and the reduction of GRSV on tomato. In the third trial, the foliar applications of spirotetramat, spinetoram and Chenopodium ambrosioides did not control F. schultzei populations nor reduce the transmission of GRSV on pepper. Results from this study will help in the development of a management program using imidacloprid and cyazypyr in rotation with spirotetramat, spinetoram and Chenopodium ambrosioides. The development of such a program to suppress F. schultzei populations thrips and prevent transmission of GRSV will be challenging, but an effective IPM program would also serve as a strong insecticide resistance management program for F. schultzei.

Influence of edaphic factors on the mineralization of neem oil coated urea in four Indian soils.

The utility of neem (Azadirachta indica A Juss) oil coated urea as a value-added nitrogenous fertilizer has been now widely accepted by Indian farmers and the fertilizer industry. In the present study, the expeller grade (EG) and hexane-extracted (HE) neem oils, the two most common commercial grades, were used to prepare neem oil coated urea (NOCU) of various oil doses, for which mineralization rates were assessed in four soils at three incubation temperatures (20, 27, and 35 degrees C). Neem oil dose-dependent conservation of ammonium N was observed in NOCU treatments in all of the soils. However, a longer incubation period and a higher soil temperature caused depletion of ammonium N. Overall, the nitrification in NOCU treatment averaged 56.6% against 77.3% for prilled urea in four soils. NOCU prepared from EG neem oil was consistently superior to that derived from hexane-extracted oil. The performance of NOCUs was best in coarse-textured soil and poorest in sodic soil. The nitrification rate (NR) of the NOCUs in the soils followed the order sodic > fine-textured > medium-textured > coarse-textured. The influence of edaphic factors on NR of NOCUs has been highlighted. The utility of the present study in predicting the performance of NOCU in diverse Indian soils was highlighted through the use of algorithms for computation of the optimum neem oil dose that would cause maximum inhibition of nitrification in any soil.