THRIPS SPECIES ON WHITE CABBAGE

Maria Pobożniak
Department of Plant Protection, Agricultural Univwersity of Cracow, Poland

ABSTRACT

This work covers the three years of observations on the species composition of thrips on the white cabbage, the periods of occurrence of the particulars species of thrips and their numerousness. Among the found species, the most numerous over all years of observations was Thrips tabaci Lindeman. Its percentage participation in the collected material was from 76.4% in 2003 to 95.9% in 2001 and because of this, it can be qualified to the group of eudominants. In 2002-2003, very numerous Anaphothrips obscurus Müller and Frankliniella intonsa (Trybom) were found. These species constituted 6.9% of collected thrips in 2002 and 16.5% in 2003. Other species were rarely observed: Aeolothrips intermedius Bagnall, Frankliniella pallida (Uzel), Thrips major Uzel, Thrips atratus Haliday, Thrips fuscipennis Haliday, Limothrips denticornis Haliday and Chirothrips manicatus Haliday.

Key words: Thysanoptera, Thrips tabaci, Frankliniella intonsa, Anaphothrips obscurus, cabbage.

INTRODUCTION

Thrips are very important group of pests attacking various cultivated plants. One of the major species is the onion thrips Thrips tabaci Lindeman. Although there are some reports on the onion thrips damaging white cabbage, this species had not been considered as important cabbage pest until the 1980s. Then the onion thrips appeared to be a new pest of cabbage [7].

In Poland over recent years onion thrips was noted as serious pests of cabbage, leek and onion [4, 5, 9]. On cabbage the thrips start feeding on external leaves which are then covering with small, convex spots. Next, they can be observed between the leaves creating the head. According to North and Shelton [7] all stages of thrips can be found in the first 11 leaves of mature head. However, sometimes the symptoms of infestation occur down to the 38^th leaf of the head [4].

The research works about the harmful influence of the thrips on the cabbage are very intensive, although they are mainly focused on Thrips tabaci Lindeman [3, 11].

Among the bibliography about fauna of Thysanoptera on cabbage, only the work by Legutowska [4] can be noted. In the research of Legutowska [4] Thrips tabaci Lindeman was evidently predominant on white cabbage cultivated in central Poland. The remaining specimens mainly belonged to the following species: Limothrips denticornis Haliday, Frankliniella intonsa (Trybom) and Thrips fuscipennis Haliday.

There is no information about the species composition of thrips occurring on cabbage in the South Poland, whether there are the harmful species, and if yes, what are the periods of the occurrence. Because of these factors, this research work was started.

MATERIAL AND METHODS

This work covers three years of observations on the species composition of thrips on the white cabbage, the periods of occurrence of the particular species of thrips and their numerousness. The experiments were carried out at the Experimental Station in Mydlniki near Cracow during 2001-2003. The method of randomized blocks with four replications was used. In 2001, 23 cultivars of white cabbage were planted: early: Eton F1, mid-late: Krautkaizer F1 and Vestri F1, late: Amtrak F1, Atria F1, Azan F1, Balaton F1, Bartolo F1, Brutus F1, Galaxy F1, Hurricane F1, Impala F1, Insistor F1, Kamienna Głowa F1, Kronos F1, Langendijker F1, Lennox F1, Masada F1, Saratoga F1, Stilon F1, Theras F1, Zerlina F1 and very late Donar F1. In 2002 because of the difficulties to obtain the seeds of some cultivars: Brutus F1, Insistor F1 and Krautkaizer F1 late cultivars of cabbage: Ancoma F1 and Kalorama F1 were used. In 2003, only 18 cultivars were sown, because the following cultivars were not available: Brutus F1, Donar F1, Insistor F1, Kalorama F1, Krautkaizer F1, Langendijker F1 and Stilon F1. The number of cultivars of cabbage was different during the successive years. The method of randomized blocks with four replications was used. In each replication, two rows of the same cv. of cabbage were planted in the random order. 15 plants were planted in each row and spaced about 0.45 m apart. The distance between rows was 0.5 m. The plots belonging to the successive replications were separated by footpath with the width of 1.5 m. In 2001, cabbage was planted on 11 June, in 2002 on 10 June and in 2003 on 3 June. No insecticides were used during experiments, and the weeds were removed mechanically and manualy. Every two weeks, three plants of cabbage from every cultivar were sampled from each plot. The cabbage plants were cut just above the soil and were placed into plastic bags to transport them to the laboratory. In the laboratory, leaves were cut and the number of adults and larvae feeding on both sides was recorded. Next, the thrips were placed in 20% solution of alcohol with the addition of fluid lowering the surface tensions, and after 5-7 days they were moved to the conservation fluid (60% solution of alcohol with the addition of glycerin). To determine the species, the microscope preparations according to Zawirska [12] were made. The identification to the species level was made using the keys by Mounded et al. [8] and Zawirska [12].

RESULTS AND DISCUSSION

During the period 2001–2003, 2337 adult and 25 larvae of thrips belonging to different species of Thysanoptera were collected from cabbage (tab. 1). Over the years of observations, the number of collected species was from 8 to 11. Among the found species, the most numerous was Thrips tabaci Lindeman (phot. 1).

Thrips tabaci Lindeman belongs to popular and harmful cosmopolitan species. It occurs and develops on many plants. Both the larvae as well as the adults feed on the various parts of the plants, usually on the leaves, young sprouts and young fruits [6]. This species is very common in the area of whole Poland [12].

The percentage participation of Thrips tabaci Lindeman in the collected material was from 76.4% in 2003 to 95.9% in 2001 and because of this, this species can be qualified to the group of eudominants (tab. 1). Over all years of observations, the adult T. tabaci were collected over the whole period of sampling. The most intensive occurrence was noted in the first and second decade of July. From the first decade of August, the numerousness of onion thrips was significantly lower (fig. 1). Especially high number of thrips T. tabaci on white cabbage was noticed in 2002, when it was twice greater than in 2001 and over three times greater than in 2003. (tab. 1). The small number of larvae of T. tabaci were observed on cabbage which proofs that this species is able to reproduce on this host plant. Also Legutowska [4] informs that the adult Thrips tabaci feeding on cabbage in the Central Poland constitute 90% of the thrips population.

During the analysis, the second most numerous species was grass thrips Anaphothrips obscurus Müller although its frequent occurrence was noted only during the period 2002-2003. Its percentage share in the collected material was 3.7% in 2002 and 9.3% in 2003. Because of the numerousness, this species was classified as the subdominant in 2002 and as the dominant in 2003. (tab. 1). Over the years 2002-2003 A. obscurus was noticed on white cabbage mainly in July, with the most intense occurrence in the first decade of July (fig. 2).

Anaphothrips obscurus Müller is very common in whole Poland (phot. 2). It can damage the young leaves and the inflorescence of grass and corn [6, 12]. It is a very important pest of corn [13]. Also according to Legutowska, Theunissen [5] the small number of this species can be found in Thysanoptera fauna on leek.

The third most numerous species observed on cabbage was Frankliniella intonsa (Trybom) (phot. 3). This species was noted over all years of observations, although it was the most numerous during the period 2002-2003. The percentage share of F. intomsa in the collected material was 3.2% in 2002 and 7.2% in 2003, which allowed to classify this species to the group of subdominants in 2002 and dominants in 2003 (tab. 1). The adult F. intonsa were collected from the start of sampling i.e. from the first decade of July in 2001 and third decade of June in 2003. Nevertheless, the great number of F. intonsa was noticed in both years only in the first decade of July. In this period, 62.2% in 2002 and 62.8% in 2003 of total number of this species found on cabbage was collected. After this period, the majority of F. intonsa leaved the cabbage and the numerousness of this species decreased from 1.8 thrips/10 plans to 0.7 thrips/10 plants in 2002 and from 1.9 thrips/10 plants to 0.5 thrips/10 plants in 2003, although this species was not very numerous until the end of observations. The last F. intonsa were collected in the first decade of August (fig. 3).

Frankliniella intonsa (Trybom) is a very common polyphagous species in Europe. It can be found mainly in the flower of various plants, belonging to different families, and develops more or less numerously nearly on each plant. It is a very active species, good flying and easy moving from one place to another [10, 12].

During the research on species composition of thrips on cabbage and leek Legutowska [4] and Legutowska, Theunissen [5] observed the numerous occurrence of Frankliniella intonsa, beside Thrips tabaci and other species belonging to Frankliniella genus i.e. Frankliniella tenuicornis (Uzel). Atakan, Özgür [1] and Deligeorgidis et al. [2] enumerate Franklinella intonsa as the serious pest of young bolls, flowers and leaves of cotton.

The realized observations shows that Anaphothrips obscurus Müller and Frankliniella intonsa (Trybom) amounted in total about 6.9% in 2002 and 16.5% in 2003 of the collected thrips. No F. intonsa and A. obscurus larvae were found during the observations so it can be assumed that these species does not develop on cabbage.

The role of Anaphothrips obscurus Müller and Frankliniella intonsa Trybom in such conditions should be more detaily investigated.

The other species belonging to Frankliniella genus which was noted sporadically during the period was Frankliniella pallida (Uzel) (phot. 4). According to Zawirska [12] F. pallida is a species which doesn’t cause any damage economically significant.

Additionally, the following species were found: Aeolothrips intermedius Bagnall, Thrips major Uzel, Thrips atratus Haliday, Thrips fuscipennis Haliday, Limothrips denticornis Haliday and Chirothrips manicatus Haliday (tab. 1).

During the period 2001-2002 Aeolothrips intermedius Bagnall was seldom noticed on cabbage. Only in 2003 this species was more numerous and classified to the subdominant group (tab. 1). Adult A. intermedius were observed mainly at the end of the first decade of July and on the beginning of the second decade of July. Also Legutowska [4], Legutowska, Theunissen [5] noticed the small occurrence of this species in the Thysanoptera fauna on cabbage at this time of the year.

Aeolothrips intermedius Bagnall is a predatory, phytophagous species, very common and numerous in whole Europe (phot. 5). Mainly larvae, but also adults feed on larvae of other thrips, aphids, springtails, small larvae and eggs of other insects and mites [6, 12].

Thrips fuscipennis Haliday is a species very common in whole Europe (phot. 6). It occurs on flowers and leaves of many plants and is treated as the serious pest of roses [4]. It is not very numerous on cabbage, recedent (tab. 1).

Rose thrips Thrips major Uzel is a species very common in whole Europe and can be found on the flowers of various plants (phot. 7). It is not very numerous on cabbage, recedent (tab. 1).

Thrips atratus Haliday – the single individuals were noticed only in 2003 (tab. 1).

It is a species very common in whole Europe (phot. 8). It occurs on flowers of various plants. Also it is very active, good flying, very often changes the place and shows the tendencies for the accumulation on the flowers of various plants [12]. Its main hosts are the plants belonging to the Caryophyllacea family (for example the very common weed – Stellaria media.) Very often is observed on flowers of various plants from Labiatae, Compositae and Papilionaceae families [10]. Sławiński, Zawirska [10] observed very numerous occurrence of this species on flowers of Nicotiana [10].

Also Legutowska [4] during the research works on the species composition of thrips on cabbage noticed the sporadic occurrence of Thrips fuscipennis, Thrips major and Thrips atratus.

Barley thrips Limothrips denticornis Haliday and Chirothrips manicatus Haliday were sporadically noticed on cabbage (phot. 9, 10, tab. 1). They are very common and very numerous pests on seeds of many grasses [6]. They are very common all over Poland [12].

The representative of genus Haplothrips was noticed only in 2001 (phot. 11, tab. 1).

CONCLUSIONS

1. The evident eudominant was Thrips tabaci Lindeman. Its share in the collected material was from 76.4% in 2003 to 95.9% in 2001. The most intensive occurrence was noted in the first and second decade of July.

2. Anaphothrips obscurus Müller and Frankliniella intonsa (Trybom) were relatively numerous during the period 2002-2003. These species constituted 6.9% in 2002 and 16. 5% of the total number of collected thrips.

3. The following species were sporadically noticed: Aeolothrips intermedius Bagnall, Frankliniella pallida (Uzel), Thrips major Uzel, Thrips atratus Haliday, Thrips fuscipennis Haliday, Limothrips denticornis Haliday and Chirothrips manicatus Haliday.

REFERENCES

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2. Deligeorgidis P. N., Athanassion C. G., Kavallieratos N. G., 2002. Seasonal abundance, spatial distribution and sampling indices of thrips populations on cotton; a 4 year survey from central Greece. Journal of Applied Entomology 126 (7-8), 343.

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4. Legutowska H., 1997. Thrips on cabbage crops in Poland. Biul. Warz. XLVII. Instytut Warzywnictwa – Skierniewice, 55-62.

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13. Zwahlen C., W., Nentwig F., Hilbeck A., 2000. Tritrophic interactions of transgenic Bacillus thuringiensis corn, Anaphothrips obscurus (Thysanoptera: Thripidae), and the predator Orius majuscules (Heteroptera: Anthocoridae). Environmental Entomology 29, 846-850.

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