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1.  Host Status of Citrus and Citrus Relatives to Tylenchulus graminis 
Journal of Nematology  1989;21(4S):661-665.
Studies were conducted on the host suitability of four citrus rootstocks--rough lemon (Citrus limon), sour orange (C. aurantium), trifoliate orange (Poncirus trifoliata cv. Argentina), and Swingle citrumelo (C. paradisi x P. trifoliata)--to Tylenchulus graminis which was previously considered a "grass" race of T. semipenetrans. In an uncultivated field, sour orange seedlings grown with T. graminis-infected broomsedge (Andropogon virginicus) were not infected with this nematode after 18-month's exposure to T. graminis population densities ranging from < 0.01 to 0.4 second-stage juveniles (J2)/cm³ soil. In a greenhouse test, two T. graminis populations from two Florida locations did not infect sour orange seedlings grown for 2 years in soil naturally infested with 0.3 and 1.3 J2/cm³. Rough lemon, trifoliate orange, and Swingle citrumelo seedlings suppressed T. graminis initial population densities of 7 to final values of < 0.1 J2/cm³ soil. Final values of > 70.0 J2/cm³ occurred in soil with broomsedge. These findings provide conclusive evidence that T. graminis is a specific parasite of grasses and does not infect citrus.
PMCID: PMC2618986  PMID: 19287668
Andropogon virginieus; broomsedge; Citrus aurantium; Citrus limon; citrus nematode; Citrus paradisi x Poncirus trifoliata; host preference; Poncirus trifoliata; rough lemon; sour orange; survival; Swingle citrumelo; trifoliate orange; Tylenchulus graminis; Tylenchulus semipenetrans
2.  Tylenchulus graminis n. sp. and T. palustris n. sp. (Tylenchulidae), from Native Flora of Florida, with Notes on T. semipenetrans and T. furcus 
Journal of Nematology  1988;20(2):266-287.
Tylenchulus graminis n. sp. and T. palustris n. sp. are described and illustrated from broomsedge (Andropogon virginicus L.) and pop ash (Fraxinus caroliniana Mill.), respectively. T. graminis resembles T. furcus in having a distinct anus, but T. graminis second-stage juveniles (J2) do not have a bifid tail. T. semipenetrans does not have a perceptible anus. The mature female of T. graminis has a mucronate pointed terminus while T. semipenetrans has a smooth and round terminus. T. graminis males have wider stylet knobs and basal bulb and a longer tail than T. semipenetrans males. T. graminis J2 have a longer posterior body portion (without large fat globules) than T. semipenetrans J2. T. palustris resembles T. semipenetrans in having an undetectable anus but differs by the short and conoid mature female postvulval section. The male of T. palustris has larger stylet knobs and basal bulb than those of T. semipenetrans and a bluntly rounded tail terminus, which is tapered in T. semipenetrans. T. palustris differs from T. furcus and T. graminis in having an undetectable anus, by the conoid postvulval section of mature females, by the shorter and rounded tail of males, and the shorter J2 posterior body section without large fat globules. T. graminis and T. palustris are parasites of indigenous flora of Florida.
PMCID: PMC2618811  PMID: 19290211
Andropogon virginicus; broomsedge; citrus; Florida; Fraxinus caroliniana; physiological race; pop ash; taxonomy; Tylenchulus furcus; Tylenchulus graminis; Tylenchulus palustris; Tylenchulus semipenetrans; scanning electron microscopy
3.  Vertical Migration of Meloidogyne chitwoodi and M. hapla under Controlled Temperature 
Journal of Nematology  1987;19(2):152-157.
Migratory ability of second-stage juveniles (J2) of two Meloidogyne chitwoodi races and a M. hapla population were compared in soil-filled columns at 12, 18, and 24 C. J2 of all populations migrated farthest at 18 C and least at 12 C. Nematode survival was significantly reduced (P = 0.05) at 24 C.M. chitwoodi J2 migrated further and in greater numbers than M. hapla J2 at all temperatures. A comparison with and without a host plant demonstrated no preferential migration toward the plant. Water percolation through the migration columns stimulated upward migration.
PMCID: PMC2618637  PMID: 19290123
Columbia root-knot nematode; northern root-knot nematode; migration; temperature; soil moisture
4.  Development of Meloidogyne chitwoodi on Wheat 
Journal of Nematology  1985;17(3):322-326.
Postinfection development of Meloidogyne chitwoodi from second-stage juveniles (J2) to mature females and egg deposition on 'Nugaines' winter wheat required 105, 51, 36, and 21 days at 10, 15, 20, and 25 C. At 25 C, the J2 induced cavities and hyperplasia in the cortex and apical meristem of root tips with hypertrophy of cortical and apical meristem cell nuclei, 2 and 5 days after inoculation. Giant cells induced by late J2 were observed in the stele 10 days after inoculation. Clusters of egg-laying females were common on wheat root galls 25 days after inoculation. Juveniles penetrated wheat roots at 4 C and above, but not at 2 C, when inoculum was obtained from cultures grown at 20 C, but no penetration occurred at 4 C when inoculum was stored for 12 hours at 4 C before inoculation. In northern Utah, J2 penetrated Nugaines wheat roots in the field in mid-May, about 5 months after seedling emergence. M. chitwoodi eggs were first observed on wheat roots in mid-July when plants were in blossom. Only 40% of overwintered M. chitwoodi eggs hatched at 25 C.
PMCID: PMC2618458  PMID: 19294100
Columbia root-knot nematode; Triticum aestivum; histopathology; life cycle; postinfection development; root infection; temperature
5.  Occurrence of Biotypes in Radopholus citrophilus 
Journal of Nematology  1985;17(2):158-162.
Two morphologically and karyotypically identical populations of the citrus burrowing nematode, Radopholus citrophilus, differed in their ability to damage and reproduce in roots of citrus rootstocks previously identified as either resistant or tolerant. These populations are considered to be biotypes, and their occurrence may explain the appearance of spreading decline symptoms in plantings of rootstocks previously considered resistant.
PMCID: PMC2618434  PMID: 19294076
burrowing nematode; citrus; control; resistance; taxonomy
6.  Effect of Soil Temperature on Reproduction of Meloidogyne chitwoodi and M. hapla Alone and in Combination on Potato and M. chitwoodi on Rotation Plants 
Journal of Nematology  1984;16(3):309-312.
Meloidogyne chitwoodi developed and reproduced more rapidly than M. hapla in potato roots at 15, 20, or 25 C when both species of nematodes were inoculated simultaneously at 250 or 1,000 juveniles of each. At 30 C significantly more M. hapla than M. chitwoodi females were found at the lower inoculum level after 41 days. More M. chitwoodi than M. hapla juveniles were extracted from soil at 15, 20, and 25 C, but only at the lower inoculum level at 30 C. Potato was considered a more suitable host for M. chitwoodi than M. hapla because of M. chitwoodi's greater reproduction at 15, 20, and 25 C. Corn and wheat cultivars tested supported M. chitwoodi reproduction at temperatures of 10, 15, 20, and 25 C, but fewest eggs were produced on these plants at 20 C. Temperatures of 10 to 25 C had little influence on the low reproduction of M. chitwoodi on four alfalfa cultivars. M. chitwoodi reproduced on the alfalfa entry Mn PL9HF.
PMCID: PMC2618396  PMID: 19294027
Columbia root-knot nematode; northern root-knot nematode; alfalfa; wheat; corn
7.  Influence of Meloidogyne chitwoodi and M. hapla on Wheat Growth 
Journal of Nematology  1984;16(2):162-165.
Meloidogyne chitwoodi reduced the growth of winter wheat 'Nugaines' directly in relation to nematode density in the greenhouse, The relationship between top dry weight and initial nematode density suggests a tolerance limit of Nugaines wheat to M. chitwoodi of between 0.03 and 0.18 eggs/cm³ of soil; the value for relative minimum plant top weight was 0.45 g and 0.75 g, respectively. Growth of wheat in field microplots containing four population densities (0.003, 0.05, 0.75 and 9 eggs/cm³ soil) was not affected significantly at any inoculum level compared to controls during September to July, However, suppression of head weights of 'Fielder' spring wheat grown May-July occurred in microplots initially infested with 0.75 and 9 eggs/cm³ soil. Reproduction (Pf/Pi) was poorer at these two inoculum levels as compared to the lower densities. In another greenhouse experiment, roots of wheat cultivars Fielder, 'Fieldwin,' 'Gaines,' 'Hyslop,' and Nugaines became infected by M. chitwoodi, but not by M. hapla. Reproduction of M. chitwoodi was less on Gaines and Nugaines than on Fielder, Fieldwin, or Hyslop.
PMCID: PMC2618362  PMID: 19295895
Columbia root-knot nematode; northern root-knot nematode; Triticum aestivum; damage threshold
8.  Response of Two Alfalfa Cultivars to Meloidogyne hapla 
Journal of Nematology  1983;15(4):644-646.
PMCID: PMC2618321  PMID: 19295860
reproduction; modeling; tolerance
9.  Incidence and Distinguishing Characteristics of Meloidogyne chitwoodi and M. hapla in Potato from the Northwestern United States 
Journal of Nematology  1982;14(3):347-353.
From September 1980 to June 1981, a survey was conducted in the major potato growing regions of northern California, Idaho, Nevada, Oregon. and Washington to determine the distribution of Meloidogyne chitwoodi and other Meloidogyne spp. Meloidogyne chitwoodi and M. hapla were the only root-knot nematode species detected parasitizing potato in all the states surveyed. Meloidogyne chitwoodi occurred alone in 83% of the samples and M. hapla in 11%, with 6% of all samples containing both species. The greater incidence of M. chitwoodi, as compared to M. hapla, may be due to the cool growing season encountered in 1980 (which favored M. chitwoodi but not M. hapla) and to the increased acreage of small grains (which are good hosts for M. chitwoodi but not M. hapla) planted in rotation with potato. Differentiation between these two species can be determined by a differential host test, perineal patterns of mature females, and shape of the tail tip amt of the tail hypodermal terminus of L₂ juveniles.
PMCID: PMC2618204  PMID: 19295719
Meloidogyne chitwoodi; M. hapla; potato
10.  Effect of Soil Temperature on the Pathogenicity and Reproduction of Meloidogyne chitwoodi and M. hapla on Russet Burbank potato 
Journal of Nematology  1981;13(4):483-486.
Meloidogyne chitwoodi and M. hapla were pathogenic to both roots and tubers of Russet Burbank potato. Both species affected root growth at 15, 20, and 25 C, but not 30 C. Meloidogyne chitwoodi reprotluced best at 15, 20, and 25 C and M. hapla at 25 and 30 C. Reproduction of M. chitwoodi was reduced at 30 C; reproduction of M. hapla was reduced at 15 C and less at 20 C. The reproductive potential of M. chitwoodi was higher than that of M. hapla at 15, 20, and 25 C. M. hapla reproduced better at 30 C than did M. chitwoodi. M. chitwoodi infected potato tubers in higher numbers than did M. hapla.
PMCID: PMC2618119  PMID: 19300793
12.  Influence of Volcanic Ash on Infectivity and Reproduction of Two Species of Meloidogyne 
Journal of Nematology  1981;13(3):409-412.
Mount St. Helens volcanic ash was incorporated into a loamy sand greenhouse soil mix to produce concentrations of 0, 0.5, 1.0, 2.0, 4.0, 8.0, 25, 50 and 100% ash. Chemical and physical properties of the various mixtures were determined. Three experiments were conducted in a greenhouse to determine if volcanic ash had any influence on root-knot nematode survival and infectivity. Tomato, Lycoperscion esculentum, seedlings cv. Columbia, susceptible to Meloidogyne hapla and M. chitwoodi were planted into pots of the soil-ash concentrations and infested with one of the two nematode species. Tomato seedlings were harvested 30, 50 and 60 days later and the roots examined for nematode infection and reproduction. Ash incorporation had no deliterious effect on root-knot nematodes in any of the experiments reported here. Nematode infection and reproduction on tomato were not affected at any ash concentration.
PMCID: PMC2618103  PMID: 19300784
13.  Description and SEM Observations of Meloidogyne chitwoodi n. sp. (Meloidogynidae), a Root-knot Nematode on Potato in the Pacific Northwest 
Journal of Nematology  1980;12(4):319-327.
Meloidogyne chitwoodi n. sp. is described and illustrated from potato (Solanum tuberosum) originally collected from Quincy, Washington, USA. This new species resembles M. hapla, but its perineal pattern is basically round to oval with distinctive and broken, curled, or twisted striae around and above the anal area. The vulva is in a sunken area devoid of striae. Vesicles or vesicle-like structures are present in the median bulb of females. The larva tail, being short and blunt with a hyaline tail terminal having little or no taper to its rounded terminus, is distinctively different from M. hapla. SEM observations revealed the nature of the perineal pattern and details of the head of larvae and males, and showed the spicules to have dentate tips ventrally. Hosts for M. chitwoodi n. sp. include potato, tomato, corn, and wheat but not strawberry, pepper, or peanut. The latter three crops are excellent hosts for M. hapla. The known distribntion of this new root-knot species presently involves certain areas of Idaho, Washington, and Oregon. The common name "Columbia root-knot nematode" is proposed for M. chitwoodi n. sp.
PMCID: PMC2618037  PMID: 19300709
taxonomy; morphology; Meloidogyne; root-knot; new species; SEM ultrastructure; potato; Solarium tuberosum; hosts
14.  A Classification of Tylenchulus semipenetrans Biotypes 
Journal of Nematology  1980;12(4):283-287.
The presence of two biotypes of the citrus nematode (Tylenchulus semipenetrans) in Italian citrus and olive orchards has been confirmed by comparing host specificity. Host reaction to California biotypes C1 and C3 and to three populations from Arizona, Texas, and Florida indicates that of these five United States biotypes, all except C3 consistently fit biotype C1. These findings, and the results of host-range studies in other countries, show that four biotypes of T. semipenetrans are distributed worldwide: the "Poncirus biotype," the "Citrus biotype," the "Mediterranean biotype," and the "Grass biotype."
PMCID: PMC2618030  PMID: 19300704
citrus-root nematode; host specificity; olive tree; Citrus spp.; Poncirus trifoliata
15.  The Response of Citrus limon Seedlings to a Symbiont, Glomus etunicatus, and a Pathogen, Radopholus similis 
Journal of Nematology  1979;11(3):270-275.
The influences of a vesicular-arbuscular mycorrhiza (Glomus etunicatus) and burrowing nematode (Radophohts similis), alone and in combination, on the growth of rough lemon (Citrus limon) seedlings were studied in the greenhouse. Growth of mycorrhizal seedlings was significantly greater than that of nonmycorrhizal seedlings or seedlings inoculated with R. sindlis. Mycorrhizal stimulation of seedling growth was inhibited by nematode infection. When seedlings were inoculated with G. etunicatus arid R. similis, suppression of seedling growth by R. similis was less on VAM seedlings than on nonmycorrhizal seedlings, Nonmycorrhizal seedlings infected with R. similis were significantly smaller than nonmycorrhizal seedlings free of R. similis. Vesicle formation and mycelia growth were less in nematode-infected roots.
PMCID: PMC2617970  PMID: 19300646
Endomycorrhizae; burrowing nematode; rough lemon
16.  The Influence of Glomus mosseae on Tylenchulus semipenetrans-Infected and Uninfected Citrus limon Seedlings 
Journal of Nematology  1979;11(3):247-250.
Greenhouse studies have shown that when rough lemon (Citrus limon) seedlings infected with TyIenchulus semipenetrans were transplanted into soil infested with Glomus mosseae, the mycorrhizal fungus infection increased seedling growth compared to nonntycorrhizal seedlings. Tylenchulus semipenetrans significantly suppressed seedling growth below that of mycorrhizal seedlings. Histological observations of nematode-free mycorrhizal roots showed that hyphae penetrated the epidermis and invaded the cortex, giving rise to arbuscules and vesicles. Nematode infection sites in T. semipenetrans-infected roots grown in soil infested with G. mosseae did not show evidence of vesicle development in the cortex but did show arbuscule development.
PMCID: PMC2617969  PMID: 19300642
mycorrhizae; citrus nematode; rough lemon
17.  Comparison of Five Populations of Tylenchulus semipenetrans to Citrus, Poncirus, and their Hybrids 
Journal of Nematology  1977;9(2):162-165.
The infectivity of five populations of Tylenchulus semipenetrans were compared and differentiated on 10 hosts (5 Citrus spp., 1 Poncirus trifoliata, and 4 hybrids of Citrus spp. X P. trifoliata). Differences in levels of infection and development (P = 0.01) occurred between Citrus spp. and P. trifoliata cv. 'Pomeroy' and their three hybrids, C. paradisi X P. trifoliata cv. 'Swingle' citruntelo and C. sinensis, cv. 'Ruby' orange X P. trifoliata cv. 'Webber Fawcett 14-7', and '15-7'. Poncirus trifoliata cv. Pomeroy was susceptible to a California biotype 3 and highly resistant to the other citrus nematode populations. Low infection levels with California biotype 1, Arizona, and Florida populations on Swingle citrumelo, and the two Ruby orange hybrids indicated inherited resistance. Reproduction of the nematode population from Texas was greatest on the three hybrids, Swingle citrumelo, Ruby orange 14-7, and 15-7, from the California 1, Arizona, and Florida populations, but its comparable densities on P. trifoliata and Citrus spp. were not sufficiently different from these populations to consider it a separate biotype. California biotype 3 was sufficiently different from all other populations to be considered a different biotype, and it was named the "Poncirus biotype."
PMCID: PMC2629655  PMID: 19305585
citrus-root nematode; resistance; population density; biotype
18.  Worldwide Dissemination of Radopholus similis and Its Importance in Crop Production 
Journal of Nematology  1977;9(1):16-25.
The burrowing nematode, Radopholus similis, attacks agronomic and horticultural crops and many weeds, and is reported to reproduce on more than 250 plant species. Two races of R. similis are recognized. Although one race attacks citrus and the other race does not, they are morphologically similar. At present, the citrus race is found attacking citrus only in Florida, U.S.A., but it is known to infect more than 250 species and varieties of noncitrus plants. Although it has many hosts, R. similis is probably most widely distributed on banana and is found worldwide. Although best known as a pest of Piper nigrum, Musa spp., and Citrus spp., it also attacks many crops that are important in world commerce and in subsistence-type agriculture, a factor which makes it a significant agricultural pest. Worldwide dissemination occurs primarily when parasitized plants are moved into areas where the pest could adapt. Yield losses of 12.5 tons/ha in bananas have been reported from R. similis infection. Infections suppress orange and grapefruit yields as much as 70-80%. Because of the severity of R. similis damage (particularly to banana and citrus), extensive control programs have been developed. Prevention, cultural practices, resistant varieties, and chemical pesticides interact to reduce losses.
PMCID: PMC2620210  PMID: 19305565
citrus; control; banana
19.  Comparative Influence of Radopholus similis and Pratylenchus coffeae on Citrus 
Journal of Nematology  1976;8(1):58-63.
Pratylenchus coffeae was as pathogenic as Radopholus sirnilis to commercial citrus rootstocks. No rootstock resistant to R. similis was resistant to P. coffeae. Both nematodes stunted citrus in three soil types. Seedling damage by P. coffeae and R. similis was greatest in fine- and coarse-textured soils, respectively. Reproduction and survival on citrus were greater for P. coffeae than for R. similis. Mixed inoculations with R. similis and P. coffeae resulted in lower populations of each species than did separate inoculations.
PMCID: PMC2620152  PMID: 19308198
Burrowing nematode; lesion nematode; rootstocks; soil type
20.  Rearing Migratory Endoparasitic Nematodes in Citrus Callus and Roots Produced from Citrus Leaves 
Journal of Nematology  1975;7(3):261-263.
Radopholus similis and Pratylenchus coffeae were reared on callus and roots developed from citrus leaves. Callus formed best when leaf petioles were immersed in Astatula fine sand and the leaves were sprayed daily with 4 ppm 2,4-D solution and maintained at 25 or 30 C. The nematodes completed one generation in 20 days at 25 C. Highest populations of R. similis (1,127) occurred after 50 days, and the highest for P. coffeae (619) after 70 days. Leaf-callus cultures from R. similis-resistant citrus rootstocks showed the same degree of infection as susceptible rough lemon callus after 30 days.
PMCID: PMC2620125  PMID: 19308168
Citrus leaf-callus
21.  Penetration of 1,2-Dibromo-3-Chloropropane in a Florida Soil 
Journal of Nematology  1975;7(3):252-255.
Gas-liquid chromatography was used to detect movement of the nematicide, 1,2-dibromo-3-chloropropane (DBCP), in soil columns containing top- and subsoil of Astatula fine sand. Topsoil contained 1.4-1.6% organic matter and subsoil 0.20-0.25%. DBCP was applied at various rates as aqueous drenches. Depth of penetration was controlled by organic matter in topsoil and varied with the amount of water applied. Maximum DBCP penetration after 14 days was 28 cm; maximum water infiltration, 115 cm. Maximum depth of penetration was obtained with a water emulsion of 30 μg/ml of DBCP applied in 15 cm of water. DBCP applied in 5 cm of water to soils containing 2.0% and 0.125% organic matter penetrated 6 cm and 60 cm, respectively.
PMCID: PMC2620123  PMID: 19308166
DBCP penetration; nematicide
22.  Postplant Fumigation with DBCP for Citrus Nematode Control in Florida 
Journal of Nematology  1974;6(1):41-48.
Eleven citrus groves of diverse varieties and ages infected with Tylenchulus semipenetrans growing in differing soils in Florida were treated with three rates of 1,2-dibromo-3-chloropropane (DBCP) applied by various means. Yield, fruit size, and T. semipenetrans populations in the roots were compared between DBCP-treated and untreated trees over a period of I-3 yr. Maximum fruit size and yield were obtained by applying DBCP at 38-58 kg/hectare (ha) (34-52 lb/acre); whereas best nematode control was with a rate of 77 kg/ha (69 lb/acre). Application of chemical emulsion with a special, drilled, low-profile sprinkler irrigation ground pipe was the most suitable method. Effect of DBCP treatment generally lasted for 3 yr. A mean annual I. 1% increase in fruit diameter, 15.2% increase in fruit yield and a 55.7% decrease incitrus nematode populations was found for D BC P-treated trees in contrast to untreated trees.
PMCID: PMC2620039  PMID: 19319363
postplant control; dibromochloropropane; citrus nematode
23.  Citrus Tree Decline Caused by Pratylenchus coffeae 
Journal of Nematology  1973;5(4):311-316.
The pathogenic effects of Pratylenchus coffeae on growth and yield of tangelo (Citrus paradisi × C. reticulata) scions grafted on rough lemon (C jambhiri), sour orange (C. aurantium) and 'Cleopatra' mandarin (C. reticulata) rootstocks were evaluated under field conditions for 4 years. Pratylenchus coffeae on inoculated trees increased to significantly damaging population densities on rough lemon rootstock the second year, on sour orange the third and on Cleopatra mandarin the fourth year after planting. Mean growth reduction of P. coffeae-infected trees after 4 years was 80, 77 and 49%, respectively, for the three rootstocks. Noninoculated trees on rough lemon and sour orange rootstocks yielded significantly more fruit than comparable inoculated trees. Natural migration of P. coffeae occurred horizontally on roots for a distance of 4.5 m.
PMCID: PMC2620023  PMID: 19319354
population densities; biology; nematode movement
24.  Preplant Fumigation for Citrus Nematode Control in Florida 
Journal of Nematology  1973;5(2):88-95.
Preplant soil fumigation experiments were conducted to control the citrus nematode, Tylenchulus semipenetrans. Generally, D-D (1,3-dichloropropene, 1,2-dichloroptopane and related chlorinated C3-hydrocarbons), Telone (1,3-dichloropropene and related chlorinated C3-hydrocarbons), Telone PBC (80% 1,3-dichloropropene, 15% chloropicrin, 5% propargyl bromide), and EDB (ethylene dibromide) controlled T. semipenetrans effectively for 4 years. The trials involved four scion varieties, two rootstock varieties and three soil types. Tree growth and yield were increased with application of D-D at 374 or 561 liters/ha (40 or 60 gal/acre) or Telone at 299 or 449 liters/ha (32 or 48 gal/acre) in broadcast and strip treatments.
PMCID: PMC2619984  PMID: 19319312
Nematicides; chemical control; Tylenchulus semipenetrans
25.  Population Fluctuation of Three Parasitic Nematodes in Florida Citrus 
Journal of Nematology  1972;4(3):194-199.
In Florida, Tylenchulus semipenetrans on citrus has two high and two low population levels each year. High levels occur in April-May and November-December, and low levels, in February-March and August-September. Population increases occur about 4-5 weeks after the spring and fall flush of root growth. Populations of Pratylenchus coffeae on citrus varied widely, and were not related to season. Populations of P. brachyurus showed seasonal variation with a high in June-July and a low in March-May. Males of T. semipenetrans and P. coffeae were found throughout the year, whereas males of P. brachyurus were rare and were found only during November and December.
PMCID: PMC2619939  PMID: 19319266
seasonal variation

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