Citrus Canopy Research Articles

Automated Debris Mass Estimation for Citrus Mechanical Harvesting Systems Using Machine Vision

An algorithm for automatically estimating mass of debris in a citrus canopy shake and catch harvester using machine vision was investigated. Debris material consists of non-citrus objects such as leaves, twigs, and branches which are mechanically harvested along with citrus fruit. While harvesting, the amount of debris is surprisingly large even in the cleanest loads. It is mandatory for the juice extraction plants to separate this debris from fruit and this process has a huge economic impact. Current situation with catastrophic diseases such as citrus greening, a bacterial plant disease called Huanglongbing (HLB), and citrus canker infestation in Florida requires citrus growers to dispose of leaves and twigs very carefully in the grove. Although not mandated, the first step to treat such diseased vegetation is to determine how much debris material is generated during harvesting. So an efficient method to estimate debris mass is required to assist debris separation mechanism. A hardware/software system to automatically estimate debris mass was developed for a citrus canopy shake and catch harvester. The idea was to estimate the debris mass from the total pixel area of the debris detected using image processing. An experimental test bench was set-up at a machine shop in the University of Florida, Gainesville, Florida, to train as well as validate the image processing algorithm. This algorithm included steps such as image rectification, overlapped area removal, morphological operations, and removal of undesired debris on the ground using a novel Parse and Add algorithm. The results showed that the coefficient of determination (R2) between the pixel area and debris mass for calibration was 0.946 and R2 between actual and estimated mass for validation set from the test bench was 0.815 with an RMSE of 1.88 kg. For the field experiment, over 27,000 images were acquired from a commercial citrus grove during harvesting in Ft. Basinger, Florida, in 2008. These images were post-processed with the algorithm and the debris objects were identified from a representative set of 180 images. The R2 between the actual and estimated debris mass for individual images was 0.78, and the RMSE was 0.02 kg. The error between total actual and estimated mass for the field experiment was 25.3%. The debris mass estimates were also correlated with GPS data to create a geo-referenced map of the debris gathered. The developed debris mass estimation system could play a crucial role in solving the problem of safe and economical disposal of diseased leaves and twigs.

Spatio-temporal patterns and interactions with honeydew-producing Hemiptera of ants in a Mediterranean citrus orchard

1 The role of ants in the citrus agro-ecosystem is controversial and understanding their ecology may help to clarify their function. The present study determined the daily and seasonal foraging patterns, the spatial distribution, the feeding sources and the associations with honeydew-producing Hemiptera of three ant species that forage in citrus canopies. 2 The dominant ants Pheidole pallidula (Nylander) (Myrmicinae) and Lasius grandis Forel (Formicinae) foraged in mutually exclusive territories within the field, although they both shared their territory with the subordinate Plagiolepis schmitzii Forel (Formicinae), a distribution pattern known as ‘ant mosaic’. 3 The observed mean overlap for the spatial distribution was significantly lower than the generated by null models, providing strong evidence of spatial interspecific competition, especially between the two dominants. 4 Ants ascended to the canopies from April until November. Colony nutritional requirements and temperature probably shape their seasonal foraging patterns. The daily activity pattern of P. schmitzii was strictly diurnal, whereas L. grandis and P. pallidula were active during the entire day. 5 The ants' diet in the canopies consisted principally of hemipteran honeydew, whereas citrus nectar and predation/scavenging did not represent important food sources. More than 60% of the total honeydew sources and 100% of the citrus mealybug Planococcus citri colonies were tended by ants during spring and summer.

Delineating productivity zones in a citrus grove using citrus production, tree growth and temporally stable soil data

The productivity of a citrus grove with variation in tree growth was mapped to delineate zones of productivity based on several indicator properties. These properties were fruit yield, ultrasonically measured tree canopy volume, normalized difference vegetation index (NDVI), elevation and apparent electrical conductivity (ECa). The spatial patterns of soil series, soil color and ECa, and their correspondence with the variation in yield emphasized the importance of variation in the soil in differentiating the productivity of the grove. Citrus fruit yield was positively correlated with canopy volume, NDVI and ECa, and yield was negatively correlated with elevation. Although all the properties were strongly correlated with yield and were able to explain the productivity of the grove, citrus tree canopy volume was most strongly correlated (r = 0.85) with yield, explaining 73% of its variation. Tree canopy volume was used to classify the citrus grove into five productivity zones termed as ‘very poor’, ‘poor’, ‘medium’, ‘good’ and ‘very good’ zones. The study showed that productivity of citrus groves can be mapped using various attributes that directly or indirectly affect citrus production. The productivity zones identified could be used successfully to plan soil sampling and characterize soil variation in new fields.

Efficacy of a micro-encapsulated formulation compared with a sticky barrier for excluding ants from citrus canopies

Inesfly IGR FITO ® is an insecticidal paint containing chlorpyrifos and pyriproxyfen incorporated in a micro-encapsulated formulation that confers the advantage of releasing active ingredients slowly. In this study, a 15-cm band of Inesfly IGR FITO ® was painted around citrus trunks. The efficacy of this paint and a sticky barrier to exclude ants from foraging in citrus trees was evaluated in two citrus orchards during the season in two different ant communities, one dominated by Lasius grandis and the other by Linepithema humile. Field results demonstrated that a single application of Inesfly IGR FITO ® at the beginning of the season was highly effective in excluding ants from canopies throughout the season. Inesfly IGR FITO ® provides an efficient and more economical alternative than current ant exclusion strategies used in many perennial crops. Further studies should be performed to determine the effects of this strategy on other pests and on beneficial arthropods in citrus.

Conservation of natural enemy fauna in citrus canopies by horticultural mineral oil: Comparison with effects of carbaryl and methidathion treatments for control of armored scales

Abstract The disruptive effects of an nC24 horticultural mineral oil (HMO) and two other insecticides (carbaryl and methidathion) on two armored scale insects and natural enemy fauna were evaluated in two citrus orchards. In the first orchard, all three spray treatments and non‐sprayed controls were distributed separately among individual trees in one block, whereas in the second orchard the control, HMO and methidathion treatments were applied at the level of whole blocks. The results in both orchards were similar. All three of the spray treatments had a lethal effect on the red scale insects and the effects of HMO and methidathion tested at the second site lasted for at least 19 weeks and for purple scale, at least 50 weeks. HMO did not have a significant effect on the abundance and species diversity of parasitoids and (for the most part) did not affect coccinellids and predatory mites. Both carbaryl and methidathion caused significant ongoing disruption to the above groups. No treatment resulted in the resurgence of the scale insects or the outbreak of phytophagous mites, even where whole blocks were sprayed.

Effect of Mediterranean Ants (Hymenoptera: Formicidae) on California Red Scale (Hemiptera: Diaspididae) Populations in Citrus Orchards

We conducted an ant-exclusion experiment in a citrus orchard to evaluate the overall impact of three ant species native in the Mediterranean, Pheidole pallidula (Nylander), Plagiolepis schmitzii Forel, and Lasius grandis (Forel), on populations of Aonidiella aurantii Maskell (California red scale). The ant-exclusion was carried out in four experimental plots from March 2007 to November 2008. Another subset of four plots, adjacent to the ant-excluded plots, was used as control. We measured scale densities and percent parasitism on fruits at harvest in 2007 and 2008. Additionally, we sampled the seasonal trend of the scale on twigs and fruits in both treatments during 2008. California red scale densities in the ant-excluded treatment began to be significantly lower than in the ant-allowed control in May (1 mo after ant activity began), and this difference increased until November. Thus, the effect of the ants on California red scale density seems to be accumulative. At harvest, scale densities on fruits were significantly lower in the ant-excluded treatment. However, percent parasitism on fruits was similar between treatments. Finally, scale densities on the fruits of the ant-allowed plots were positively correlated with the number of ants that climbed to the citrus canopy. These results suggest that increases of scale densities induced by Mediterranean ants depend on the intensity of the ant-activity on citrus canopies.

Ant versus bird exclusion effects on the arthropod assemblage of an organic citrus grove

1. Predation‐exclusion experiments have highlighted that top‐down control is pervasive in terrestrial communities, but most of these experiments are simplistic in that they only excluded a single group of predators and the effect of removal was evaluated on a few species from the community. The main goal of our study was to experimentally establish the relative effects of ants and birds on the same arthropod assemblage of canopy trees.2. We conducted 1‐year long manipulative experiments in an organic citrus grove intended to quantify the independent effects of bird and ant predators on the abundance of arthropods. Birds were excluded with plastic nets whereas ants were excluded with sticky barriers on the trunks. The sticky barrier also excluded other ground dwelling insects, like the European earwig Forficula auricularia L.3. Both the exclusion of ants and birds affected the arthropod community of the citrus canopies, but the exclusion of ants was far more important than the exclusion of birds. Indeed, almost all groups of arthropods had higher abundance in ant‐excluded than in control trees, whereas only dermapterans were more abundant in bird‐excluded than in control trees. A more detailed analysis conducted on spiders also showed that the effect of ant exclusion was limited to a few families rather than being widespread over the entire diverse spectrum of spiders.4. Our results suggest that the relative importance of vertebrate and invertebrate predators in regulating arthropod populations largely depends on the nature of the predator–prey system.

Spatial patterns of the red palm weevil and applied entomopathogenic nematode Heterorhabditis bacteriophora

The distribution and abundance of red palm weevil (Rhynchophorus ferrugineus) within palm tree-infected stems at Ismaelia governorate, Egypt, were investigated. Taylor's power law was fit (P ≤ 0.01) to its larvae, pupae and/or adults. The slope value of this power law indicated the clumped distribution of these insect stages. Sample size optimisation needed to achieve a predetermined level of sampling error for the insect stages was calculated. Also, soil samples were taken after uniform application of entomopathogenic nematode Heterorhabditis bacteriophora strain EG1 to the soil under citrus tree canopies at the rate of 104 infective juveniles/400 cm2 plots, and assayed for the nematode using the Galleria bait method. At the first and second sampling dates, the nematode displayed contagious distribution and attained mean insect mortality of 15.3 and 4, respectively. At the third date of sampling, the nematode showed random distribution according to chi-squared test and caused 1.8 mean insect mortality. Evaluation of H. bacteriophora EG1 as a biocontrol measure for the weevil was discussed based on their investigated dispersion indices.

Levantamento populacional de cigarrinhas (Hemiptera: Cicadellidae) associadas à transmissão de Xylella fastidiosa em pomares cítricos do Litoral Norte da Bahia

The causal agent of citrus variegated clorosis, Xylella fastidiosa, is transmitted by leafhoppers of the subfamily Cicadellinae, whose species vary regionally. The goal of this study was to identify potential vectors of this pathogen in citrus groves of Bahia North Coast, Brazil. The survey was done from March/2002 to February/2003 in three seven- to nine-year-old sweet orange (Citrus sinensis, Pêra variety) groves located in Rio Real, BA. Fifteen yellow sticky cards (8.5x11.5 cm) were installed 40 m apart in each grove, hanged at 1.5 m high on the upper north side of citrus canopies, and replaced fortnightly. A sweep net was periodically used to sample leafhoppers on herbaceous weeds inside the groves, by selecting five points at random and performing 30 sweeps in each point. A total of 1,360 specimens of 49 Auchenorrhyncha species were collected in this study, mostly in the family Cicadellidae (90.2%). The subfamily Cicadellinae, which includes the sharpshooter vectors of X. fastidiosa, showed the largest number of species (14) and specimens (84.8%). Acrogonia flagellata Young, A. citrina Marucci & Cavichioli, Homalodisca spottii Takiya, Cavichioli & McKamey and an unidentified Cicadellini (species 1) were the dominant species trapped on citrus canopies, while Hortensia similis (Walker) and Erythrogonia dubia (Medler) were dominant in the weedy vegetation. Among the Cicadellinae species already known as vectors of X. fastidiosa in citrus, only A. citrina, Bucephalogonia xanthophis (Berg) e Ferrariana trivittata (Signoret) were found. The two latter species were accidentally trapped by sweep net in the weedy vegetation.

Magnitude- and Shape-Related Feature Integration in Hyperspectral Mixture Analysis to Monitor Weeds in Citrus Orchards

Traditionally, spectral mixture analysis (SMA) fails to fully account for highly similar ground components or endmembers. The high similarity between weed and crop spectra hampers the implementation of SMA for steering weed control management practices. To address this problem, this paper presents an alternative SMA technique, referred to as Integrated Spectral Unmixing (InSU). InSU combines both magnitude (i.e., reflectance) and shape (i.e., derivative reflectance) related features in an automated waveband selection protocol. Analysis was performed on different simulated mixed pixel spectra sets compiled from in situ-measured weed canopy, Citrus canopy, and soil spectra. Compared to traditional linear SMA, InSU significantly improved weed cover fraction estimations. An average decrease in fraction abundance error (Deltaf) of 0.09 was demonstrated for a signal-to-noise ratio (SNR) of 500 : 1, while for a SNR of 50 : 1, the decrease was 0.06.

Midday depression of photosynthesis and effects of mist spray in citrus

AbstractDiurnal variations of gas exchange, chlorophyll a fluorescence and some related biochemical characteristics in sun‐acclimated mature citrus leaves of mist‐sprayed (treatment) and unsprayed (control) trees were compared on sunny days during summer to identify the environmental and physiological factors limiting carbon gain in citrus tree canopies. At midday, net photosynthesis and maximal photochemical efficiency of photosystem II (Fv/Fm) in citrus leaves decreased significantly under control conditions, but the decrease was mitigated by mist spraying. Although the content of malondialdehyde, hydrogen peroxide and activities of antioxidant enzymes increased at midday in both mist‐sprayed and control leaves, they were much higher in control leaves than in mist‐sprayed leaves. The level of D1 protein decreased significantly in control leaves at midday and then was partly recovered later, while that in treated leaves changed to a much lesser extent because of alleviation of photoinhibition by mist spraying. Both the fast and the slow phases of millisecond‐delayed light emissions in treated citrus leaves were higher than those in control leaves, indicating that mist spraying protects the normal operation of the photosynthetic apparatus in leaves. Mist spraying also reduced leaf temperatures and the ratio of air to leaf vapour pressure deficit (ALVPD), leading to increases in stomatal conductance (gs) and alleviation of photoinhibition at midday. It is concluded that the decline of leaf gs under high‐ALVPD conditions in summer is an important factor contributing to midday depression of photosynthesis in citrus, and mist spraying is effective in alleviating midday depression of photosynthesis in citrus leaves.

A Conceptual Framework for the Simultaneous Extraction of Sub-pixel Spatial Extent and Spectral Characteristics of Crops

The sub-pixel spectral contribution of background soils and shadows hampers the accurate site-specific monitoring of agricultural crop characteristics from aerial or satellite images. To address this problem, the present study combines measured in situ and hyperspectral data in an alternative unmixing algorithm. The proposed algorithm, referred to as Soil Modeling Mixture Analysis (SMMA), incorporates a soil reflectance model in a traditional unmixing algorithm and as such opens up the opportunity to simultaneously extract the sub-pixel spatial extent of crops as well as its pure spectral information. The performance of the algorithm is evaluated using a soil moisture reflectance model, calibrated for an in situ measured Albic Luvisol dataset. Synthetic mixtures, i.e., compiled from in situ measured hyperspectral bare soil and citrus tree canopy spectra, were decomposed and the sub-pixel crop cover fractions (R 2 � 0.94, RMSE � 0.03) and pure vegetation signals (average extraction error 350 to 2,500 nm � 0.017, RMSE � 0.02) were adequately extracted from the mixtures.

A weighted linear spectral mixture analysis approach to address endmember variability in agricultural production systems

The least squares error (LSE) technique is frequently used to estimate abundance fractions in linear spectral mixture analysis (LSMA). The LSE is typically equally weighted for all wavebands, assuming equally important effects. This is, however, not always the case and therefore traditional LSMA often results in suboptimal fraction estimates. This study presents a weighted LSMA approach that prioritises wavebands with minor or no negative effects on fraction estimates. Synthetic mixed pixel spectra compiled from in situ measured spectra of bare soil, citrus tree and weed canopies were used for validation. The results show markedly improved fraction estimates obtained for the weighted approach, with a mean absolute gain of 0.24 in R 2 and a mean absolute reduction in fraction abundance error of 0.06.

Activity-density of Pardosa cribata in Spanish citrus orchards and its predatory capacity on Ceratitis capitata and Myzus persicae

The wolf spider Pardosa cribata Simon is the most abundant ground-dwelling spider inhabiting citrus orchards in eastern Spain. However, little is known about its activity-density and its predatory role in the citrus agrosystem. Here we report on the activity-density of P. cribata monitored by pitfall traps, and on its capacity to prey on two citrus pests that appear both in the citrus canopy and the ground cover, Ceratitis capitata (Wiedemman) and Myzus persicae (Sulzer), respectively. Pardosa cribata was present in citrus orchards throughout the year, with a peak in spring and a higher peak in summer. Pardosa cribata preyed on adults and third-instar larvae but not on pupae of C. capitata. A type II functional response was obtained for teneral-like adults, with an estimated attack rate (a′) of 0.771 ± 0.213 days−1 and a handling time (T h) of 0.051 ± 0.013 days. Pardosa cribata also preyed efficiently on M. persicae, giving a type II functional response with an estimated attack rate and handling time of 2.833 ± 0.578 days−1 and 0.031 ± 0.001 days, respectively. The data reported here indicate that this wolf spider could play an important role in regulating both these pests, and therefore might contribute to developing conservation biological control strategies for citrus pests.

Study on temporal variation in citrus canopy using thermal imaging for citrus fruit detection

This paper presents a study of the thermal temporal variation in citrus canopy as a potential approach for improving fruit detection for harvesting orange. Tree canopy was monitored on 24 h cycles using a thermal infrared camera. Four different trees (4 regions of interest in 4 different tree canopies) were observed on four separate days. Surface temperature of the fruit, ambient temperature and relative humidity (RH) were measured using a portable Dew Point Meter. The acquired thermal images were corrected for fruit emissivity, which was estimated to be 0.90, the ambient temperature, the RH and the reflected temperature. Fruit and canopy temperature profile demonstrated a relatively large temperature gradient, which occurred from afternoon (16:00) until midnight. This was evident from the acquired thermal images of the canopy. In addition, the fruits were successfully segmented in the thermal images using image processing techniques during the time range of the largest temperature difference, which suggest potential application of thermal imaging for improved detection for harvesting.

Water Balance Components in a Mature Citrus Orchard

The low water‐holding capacity of sandy soils, together with spatial and temporal variations of rainfall, require Florida citrus trees to be irrigated for optimal production. Citrus tree root systems are exposed to various hydrologic conditions because of soil temperature and water gradients due to tree canopy shading and under‐tree microirrigation. The main goal of this study was to evaluate water balance components in a mature citrus orchard grown on central Florida ridge soils with special interest in quantifying rainfall interception by a citrus canopy and its effect on effective rainfall estimation. Soil water content was monitored every 30 min at 10‐, 20‐, 40‐, and 80‐cm depths in the root zone both under and outside of citrus tree canopies. Microirrigation, rainfall, and weather data were used to calculate effective rainfall, plant water uptake, and deep drainage. We found that the tree canopy intercepted 35 and 50% of the incoming high (≥5‐mm) and low (<5‐mm) intensity rainfalls, respectively. Effective rainfall calculated without accounting for the canopy interception effect was overestimated by about 30 and 5% for the dry and wet periods, respectively. Citrus crop evapotranspiration was higher under the tree canopy (irrigated area) than outside the tree canopy (unirrigated area) during the dry season because of supplemental irrigation.

Nitrogen Release Patterns of a Mixed Controlled-release Fertilizer and Its Components

Applying water-soluble nitrogen (N) fertilizer to Florida citrus (Citrus spp.) trees on deep sandy soils may lead to poor nutrient use efficiency and possible nitrate contamination of groundwater if rainfall or irrigation is excessive. Controlled-release fertilizer (CRF) is a possible alternative to increase N uptake efficiency and minimize losses to the environment, but current grower acceptance is limited as a result of lack of experience with CRF performance and its high relative cost. The objective of this study was to measure the N release characteristics of a CRF blend (CitriBlen®) designed for mature Florida citrus trees and its three CRF components [Agrocote® Type A, Agrocote® Type C(D), and Agrocote® Poly-S®] under laboratory and field conditions. We first characterized N release from these CRF materials using a 270-day laboratory soil incubation. The quantity of N released was influenced by CRF material used; after 270 days, cumulative leached N recoveries were 90%, 82%, 85%, and 69% of the total N applied as CitriBlen®, Agrocote® Type A, Agrocote® Type C(D), and Agrocote® Poly-S®, respectively. We then measured the N release patterns of the fertilizers in a 1-year field evaluation and developed their N release curves. Studies were simultaneously conducted in central and southwestern Florida. Mesh bags containing 3.5 g of elemental N from each source were placed on the soil surface within the irrigated zone under a citrus tree canopy to estimate N release rates from the fertilizers. Despite differential N release rates between locations, at 1 year, the rank of N release was Type A > CitriBlen® > Poly-S® > Type C(D). CitriBlen® N release patterns matched well with the current University of Florida, Institute of Food and Agricultural Sciences citrus fertilization strategy recommended as a best management practice.

Application of narrow-band TBVI in estimating fruit yield in citrus

Recently, the two-band vegetation index (TBVI) has been developed as an alternative to the conventional normalised difference vegetation index (NDVI) for assessing various agricultural crop characteristics. The potential of the narrow-band TBVI derived from airborne hyperspectral imagery to predict fruit yield in citrus was examined in this paper. Hyperspectral images in 72 visible and near-infrared (NIR) wavelength bands (from 407 to 898 nm) were acquired three times over a citrus orchard in Japan on May 26, June 21 and July 21, 2005 by an airborne imaging spectrometer for applications (AISA) Eagle system. Spectra for individual trees were obtained by averaging reflectance values of all pixels on each citrus canopy that was recognised from the acquired images. Narrow-band TBVI involving all possible two-band combinations of 72 channels was tested in terms of its potential to predict fruit yield on individual citrus trees. Multiple linear regression (MLR) models based on several significant wavelengths were also evaluated. Results indicate that the hyperspectral image obtained on May 26 demonstrated the highest correlation with citrus yield. This suggests that canopy features at the fast vegetation growth stage provide more relevant information on the yield variability among individual trees. Moreover, the TBVI showed a greater potential than the simple combination of several significant wavelengths in providing an indication of fruit yield in citrus. Based on the hyperspectral image obtained on May 26, the TBVIs calculated for the red and NIR regions were significantly correlated with citrus yield, and the “red edge” region showed a higher relevance than the red region in calculating the TBVI that has a higher correlation with citrus yield. The TBVI based on the 823 nm (NIR) and 728 nm (red edge) wavelengths was found to provide optimal citrus yield information ( R 2 =0.5795, RRMSE=0.6636). Due to the significant effect of the alternate bearing mechanism on individual citrus trees, canopy size cannot be used as a single predictor for citrus yield ( R 2 =0.4516, RRMSE=0.8298). However, by incorporating the TBVI and canopy size into the model, the prediction result was greatly improved ( R 2 =0.6913, RRMSE=0.6071). This suggests that the yield on individual trees is determined by the combined effect of the TBVI and canopy size. This study demonstrates the potential of narrow-band TBVI derived from airborne hyperspectral imagery to predict the fruit yield in citrus. Yield estimates can provide valuable information for forecasting yields, planning harvest schedules and generating prescription maps for tree-specific application of alternate bearing control measures and other management practices.

Spatial pattern of black spot incidence within citrus trees related to disease severity and pathogen dispersal

Guignardia citricarpa, the causal agent of citrus black spot, forms airborne ascospores on decomposing citrus leaves and water‐spread conidia on fruits, leaves and twigs. The spatial pattern of diseased fruit in citrus tree canopies was used to assess the importance of ascospores and conidia in citrus black spot epidemics in São Paulo State, Brazil. The aggregation of diseased fruit in the citrus tree canopy was quantified by the binomial dispersion index (D) and the binary form of Taylor's Power Law for 303 trees in six groves. D was significantly greater than 1 in 251 trees. The intercept of the regression line of Taylor's Power Law was significantly greater than 0 and the slope was not different from 1, implying that diseased fruit was aggregated in the canopy independent of disease incidence. Disease incidence (p) and severity (S) were assessed in 2875 citrus trees. The incidence‐severity relationship was described (R2 = 88·7%) by the model ln(S) = ln(a) + bCLL(p) where CLL = complementary log‐log transformation. The high severity at low incidence observed in many cases is also indicative of low distance spread of G. citricarpa spores. For the same level of disease incidence, some trees had most of the diseased fruit with many lesions and high disease severity, whereas other trees had most of the fruit with few lesions and low disease severity. Aggregation of diseased fruit in the trees suggests that splash‐dispersed conidia have an important role in increasing the disease in citrus trees in Brazil.

Thysanoptera (Thrips) Within Citrus Orchards in Florida: Species Distribution, Relative and Seasonal Abundance Within Trees, and Species on Vines and Ground Cover Plants

Seven citrus orchards on reduced to no pesticide spray programs were sampled for Thysanoptera in central and south central Florida. Inner and outer canopy leaves, fruits, twigs, trunk scrapings, vines and ground cover plants were sampled monthly between January 1995 and January 1996. Thirty-six species of thrips were identified from 2,979 specimens collected from within citrus tree canopies and 18,266 specimens from vines and ground cover plants within the seven citrus orchards. The thrips species included seven predators [Aleurodothrips fasciapennis (Franklin), Karnyothrips flavipes (Jones), K. melaleucus (Bagnall), Leptothrips cassiae (Watson), L. macroocellatus (Watson), L. pini (Watson), and Scolothrips sexmaculatus (Pergande)] 21 plant feeding species [Anaphothrips n. sp., Arorathrips mexicanus (Crawford), Aurantothrips orchidaceous (Bagnall), Baileyothrips limbatus (Hood), Chaetanaphothrips orchidii (Moulton), Danothrips trifasciatus (Sakimura), Echinothrips americanus (Morgan), Frankliniella bispinosa (Morgan), F. cephalica (Crawford), F. fusca (Hinds), F. gossypiana (Hood), Frankliniella sp. (runneri group), Haplothrips gowdeyi (Franklin), Heliothrips haemorrhoidalis (Bouché), Leucothrips piercei (Morgan), Microcephalothrips abdominalis (Crawford), Neohydatothrips floridanus (Watson), N. portoricensis (Morgan), Pseudothrips inequalis (Beach), Scirtothrips sp., and Thrips hawaiiensis (Morgan)]; and eight fungivorous feeding species [Adraneothrips decorus (Hood), Hoplandrothrips pergandei (Hinds), Idolothripinae sp., Merothrips floridensis (Watson), M. morgani (Hood), Neurothrips magnafemoralis (Hinds), Stephanothrips occidentalis Hood and Williams, and Symphyothrips sp.]. Only F. bispinosa, C. orchidii, D. trifasciatus, and H. haemorrhoidalis have been considered economic pests on Florida citrus. Scirtothrips sp. and T. hawaiiensis were recovered in low numbers within Florida citrus orchards. Both are potential pest species to citrus and possibly other crops in Florida. The five most abundant thrips species collected within citrus tree canopies were: A. fasciapennis, F. bispinosa, C. orchidii, K. flavipes, and D. trifasciatus. In comparison, the following five thrips species were most abundant on vines or ground cover plants: F. bispinosa, H. gowdeyi, F. cephalica, M. abdominalis, and F. gossypiana. Fifty-eight species of vines or ground cover plants in 26 families were infested with one or more of 27 species of thrips.