Keywords: Curculio nucum, Balaninus nucum, Xyleborus dispar, Phytoptus ... ambrosia beetle (Xyleborus dispar), big bud mites (Phytoptus avellanae and.
POPULATION DENSITIES AND SEASONAL FLUCTUATIONS OF HAZELNUT PESTS IN SAMSUN, TURKEY İslam Saruhan and Celal Tuncer Department of Entomology Faculty of Agriculture Ondokuz Mayõs University 55139 Samsun, Turkey Keywords: Curculio nucum, Balaninus nucum, Xyleborus dispar, Phytoptus avellanae, Cecidophyopsis vermiformis, Obera linearis, Hyphantria cunea, Myzocallis coryli Abstract Surveys conducted in hazelnut orchards in Samsun province during 1997–1998 showed that the most important and widespread pests were nut weevil (Curculio nucum), ambrosia beetle (Xyleborus dispar), big bud mites (Phytoptus avellanae and Cecidophyopsis vermiformis) and hazel longhorned beetle (Obera linearis). Pest populations varied over the four districts. Nut weevil adults appeared from early May to late June, and population density varied between 1-8 adults/10 “ocak”. Çarşamba and Salõpazarõ districts had higher populations than the other two districts, and mean nut damage was nearly 14%. Big bud mites were widespread and were found in high populations. Big bud numbers varied from one to 7 per trunk, and Ondokuzmayõs district had the highest population. Ambrosia beetle was a very serious problem in the Çarşamba and Terme districts. Ambrosia beetle adults were seen in late April and early June. Hazel longhorned beetle produced very serious damage in Çarşamba, Terme and Salõpazarõ districts and numbers of injured twigs varied between 5-14 per “ocak”. Pentatomid bugs (Hemiptera:Pentatomidae), fall webworm (Hyphantria cunea), filbert aphid (Myzocallis coryli), brown scale (Parthenolecanium corni, P. rufulum) and Gypsonema dealbana were found as secondary pests at varying population densities. 1.
Introduction
Hazelnut is a very important export crop grown on almost 500,000 ha in Turkey. Samsun province is one of the primary hazelnut producing areas of Turkey, accounting for approximately 10% of the total hazelnut area and production. Annual production is around 55,000 tons in Samsun (Anonymous, 1999), and almost 35,000 families live on the income from their hazelnut orchards. Insect and mite pests are the major concern of hazelnut growers in Samsun province and throughout the hazelnut growing areas of Turkey. Hundreds of pest species have been found in the Turkish hazelnut region (Işõk et al., 1987; Tuncer and Ecevit, 1997). Only a few of them are serious pests; most are seen only in low populations. The types of pests and their severity vary from area to area and from year to year. C. nucum, X. dispar, O. linearis, P. prasina, P. avellanea and C. vermiformis are the most common and widespread pests. But, since the hazelnut production area includes several provinces and districts, pest problems may vary from one place to another. Although some attempts have been made to determine which pest species are present in hazelnut orchards in Samsun province (Tuncer and Ecevit, 1996), there has been no detailed study of the pests and their population levels. Because pest populations are very dynamic and there have been changes in cultural practices in the hazelnut agroecosystem, it is advisable to monitor population density over time. This study was carried out to determine the serious hazelnut pests and their population densities and fluctuations in Samsun province by Proc. V Int. Congress on Hazelnut Ed. S.A. Mehlenbacher Acta Hort. 556, ISHS 2001
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periodic field surveys. The results of these surveys are summarized in this paper. 2.
Materials and methods
Research was conducted in four main districts of Samsun province for a period of two years (1997-1998). These districts are Çarşamba, Terme, Ondokuzmayõs and Salõpazarõ; the first three are at or near sea level. Two different orchards in each district were selected for observation. Each orchard was almost one hectare. Pesticides were not applied in these orchards during the study. The mean values for the two orchards in each district were calculated. The population trends of the major pests were examined by periodic field counts. Orchards were visited about every 15 days from April to the end of September and populations of the following pests were monitored: Curculio nucum, pentatomid bugs (Hemiptera: Pentatomidae), Hyphantria cunea, Xyleborus dispar and Myzocallis coryli. Counts of C. nucum and pentatomid bugs were obtained by shaking the insects onto a cloth sheet (3 x 3.5 m) for 10 randomly selected “ocak” in each orchard on each date. An ocak consists of a group of 8-10 individual hazelnut plants. At harvest time, from each of these ocak, 100 nuts were picked and inspected for damage by C . nucum. The number of H. cunea colonies was counted from early May to the end of September in 10 “ocak” of each orchard. M. coryli populations were checked by recording the total number of aphids per leaf on four randomly selected shoots per ocak and 10 ocak per orchard from April to September. During this same period, all trunks in the 10 ocak of each orchard were checked for presence of X. dispar. Additionally, five ocak heavily infested by X. dispar were selected and adult emergence was followed from early April to late September by inspecting all trunks and limbs and counting the number of exit holes. The population level and damage caused by Gypsonama dealbana were checked on 30 randomly selected leaves from different sides of each ocak, in 10 ocak per orchard during September, after most leaf damage had occurred. Big bud mite damage was assessed by examining all of the buds and counting the number of big buds on four limbs of each ocak in February. For this pest, three ocak per orchard in a total of 26 orchards in different districts were visited. The population density of brown scales (Parthenolecanium corni, P. rufulum) was determined by counting insects on twigs, each 30 cm long and 1-3 years old, during May and June before egg hatch. Three shoots from each side of the ocak were checked in 10 ocak in each of two orchards in every district. Larval damage from Obera linearis was assessed by inspecting all of the twigs of 10 ocak per orchard in each of two orchards in every district during July and August. A general survey was conducted in 25 orchards in different districts of Samsun during July and August of 1997 and 1998 to check for incidence of secondary pests and to help assess the general situation of hazelnut pests in the province. 3.
Results 3.1. Nut weevil (C. nucum )
Nut weevil this is the key pest in almost all hazelnut orchards of Turkey. Adult emergence begins in early May and reaches a peak in late May and early June (Table 1). Adults were observed from early May until early July; counts ranged from 0-8 adults per 10 ocak in 1997 and 0-5 in 1998. Çarşamba and Salõpazarõ districts had higher population densities compare to Ondokuzmayõs and Terme. Larval damage to nuts was very low (Table 2); the frequency of nuts with holes was 0-2.5%. But other types of damage (browned and blackened nuts) which are generally attributed to feeding by adult C. nucum were excessive. The range of total damage attributed to C. nucum was 10.5-19.0%.
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3.2. Big bud mites (P. avellanae and C. vermiformis) Big bud mites were very widespread in the sampled hazelnut orchards. The number of big buds per trunk ranged from one to seven. Ondokuzmayõs district had the highest population, and Salõpazarõ district the lowest (Table 3). 3.3. Ambrosia beetle (X. dispar) Farmer complaints in recent years indicated that ambrosia beetle had become a very serious pest, especially in hazelnut orchards at low elevations in Çarşamba and Terme districts. Our research confirmed that X. dispar is a very serious problem in these two districts. The numbers of infested trunks in each ocak varied between 0-6 and 0-12 in Çarşamba district and 0-5 and 0-7 in Terme district in 1997 and 1998, respectively (Fig.1). On the other hand, infestation levels were very low in Ondokuzmayõs and Salõpazarõ districts. There are almost 10 hazelnut trunks per ocak, and almost half of the trunks were infested by X. dispar in Çarşamba and Terme districts. X. dispar adults emerged from trunks between early April and early August, and two main periods were noted. The first period, which accounted for nearly 30% of the emergence, was between 4 April and 7 May. The second period, which accounted for 38.7% of the emergence, was 7 June – 14 July (Table 4). 3.4. Hazel longhorned beetle (Obera linearis) O. linearis is another hazelnut pest which has become very common and is found in high populations in hazelnut orchards in Samsun. The mean numbers of injured twigs in 1997 ranged from 6.7 per ocak in Ondokuzmayõs to 10.7 in Salõpazarõ. The next year, the numbers of ranged from 4.6 per ocak in Ondokuzmayõs to 14.0 in Terme. Obviously these counts do not indicate the damage only in that year, because this pest develops in twigs over a two-year period and damaged twigs can remain on the trees for a while (Table 5). 3.5. Secondary pests of hazelnut in Samsun province Altough a number of minor pests such as pentatomid bugs, filbert aphid, fall webworm, brown scales and G. dealbana were noticed during the study, some of them were present in numbers too small to be of economic significance and others cannot be classified as serious pests because of their feeding habit and low damage level. Pentatomid bugs were very common pests throughout the hazelnut orchards of Samsun. Eight species of Pentatomid bugs were found: Aconthosoma haemerrhoidale L., Arma custos F., Dolycoris baccarum L., Holcostethus vernalis W., Polomena prasina L., Polomena viridissima P., Pithaeus sanguinipes F. and Raphigaster nebulosa Pd. Additionally, two bugs belonging to the Coreidae family, Coreus marginatus L. and Gonocerus acuteangulasus Goeze, were found. Pentatomid bugs were seen from early May to late September, but the average was less than one bug per ocak (Fig. 2). The general survey of 25 orchards revealed similar counts. Filbert aphid (Myzocallis coryli) was another very widespread secondary pest, occurring on the undersides of leaves from early April to late September. Although the degree of infestation was as high as 300 aphids per leaf in June, 1997 in Ondokuzmayõs district, the population level rarely exceeded 50 aphids per leaf in 1997 and 20 aphids per leaf in 1998. No visible damage was observed and no apparent economic loss was sustained from aphids in any of the orchards. Fall webworm (Hyphantria cunea) colonies were seen between late May and late September. None were observed in Ondokuzmayõs district in either year. Çarşamba and Terme had higher populations than Salõpazarõ. The number of larval colonies per ocak varied between one and 7, but rarely exceeded 2-3. Counts were especially high after the
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second generation appeared in early August, sometimes reaching 7 colonies per ocak. The general survey of 25 orchards also showed an average of 2-3 colonies per ocak. It is fortunate that the second generation of this pest feeds on leaves after harvest time. Brown scales (P. corni and P. rufulum) were seen only in Ondokuzmayõs district, where counts were as high as 5-16 scales per twig in 1997 and 10-27 scales per twig in 1998. G. dealbana population levels were very low, and were similar in all four districts, ranging from 2.5% - 3.6% injured leaves in 1997 and 1.0% - 2.6% in 1998. In addition to the pests mentioned above, Lymantria dispar and Lepidosaphes ulmi were noted at very low levels. 4.
Discussion
Nut weevil is the key pest in hazelnut orchards in Turkey as well as many European countries (AliNiazee, 1998; Tuncer and Ecevit, 1997; Ioachim and Bobarnac, 1997). In Turkey, orchards at slightly higher elevations are more likely to be infested by this pest than those at lower elevations (Tuncer and Ecevit, 1997). In Samsun province, where this study was conducted, most hazelnut plantations are at sea level. For this reason, the population level was lower in this study than in previous reports from other provinces in Turkey (Işõk et al., 1987; Ecevit et al., 1996). In spite of the low counts, total damage by this pest (including nut with holes, browned and blackened nuts) averaged 14%. Big bud mites are the most widespread pests of hazelnut throughout the world (AliNiazee, 1998; Ozman and Toros, 1997; Stamenkovic et al., 1997; Ioachim and Bobarnac, 1997). During this study, every orchard was infested by big bud mites, and the number of big buds per trunk ranged between 1 and 7. According to Ozman (1995), cultivars vary in their susceptibility to bud mites, and up to 26% of the buds can be infested. Ambrosia beetle was a very serious problem of hazelnut orchards of Çarşamba and Terme districts where almost half of the trunks were infested. The number of farmers who complain about this pest is increasing, and some prefer to cut the hazelnut bushes out because of this pest. This pest is mostly seen in orchards with poor drainage along the coast and in orchards weakened by other factors. A second contributing factor may the old and debilitated forest and shade trees bordering the hazelnut orchards, as they are also hosts of this pest. Infestation levels in Salõpazarõ and Terme district were lower than the other two districts, which are at higher elevations and generally do not have drainage problems or border trees. Hazel longhorned beetle is another pest which deserves attention in hazelnut orchards on the Black Sea coast of Turkey. Because of its damage and feeding behavior, many farmers do not realize its potential as a pest and do not apply any control methods. We found high populations of this pest in all four districts. Bugs were very widespread in the hazelnut orchards of Samsun although population levels were low. Bug feeding on young nuts could easily go unnoticed, and the establishment of a cause-and-effect relationship is difficult (AliNiazee, 1998). Ten bug species were identified in this study, and most of them are also very common in other hazelnut growing areas and countries (Tavella et al., 1997; Tuncer and Ecevit, 1997). Filbert aphids are generally present at very low levels, but occasionally reach the economic threshold in Turkish hazelnut orchards (Tuncer and Ecevit, 1996; Tuncer at al., 1997). During the first year of this study, aphid populations reached large numbers in June, especially in Ondokuzmayõs district, although no visible damage was observed. In general, we conclude that filbert aphid is not a major problem. Even though populations are large in May and June, this pest is suppressed by the chemicals applied for nut weevils in addition to hot summer days and predators (AliNiazee, 1980; Tuncer et al., 1997). Although fall webworm is seen in other provinces of the Black Sea region of Turkey, it is only a problem in Samsun (Tuncer, 1992; Tuncer and Ecevit, 1996). During this study, three of the four districts of Samsun province had comparatively high
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populations, especially after the second generation began to emerge in August. In spite of the large populations, most farmers do not use any control method because most of the injury to leaves occurs after harvest. Brown scales are not a common problem of hazelnut orchards of Samsun, and were found only in Ondokuzmayõs district. But long-term observations in this area indicate that its importance as a pest is increasing. G. dealbana, L. dispar and L. ulmi were minor pests found in this study. Although these pests were comparatively widespread in Samsun, their populations were always very low. References AliNiazee M.T. 1998. Ecology and management of hazelnut pests. Annu. Rev. Entomol. 43:395-419. AliNiazee M.T. 1980. Insect and mite pests of filberts. Bull. Oreg. Agric. Exp. Stn 643. 12 p. Anonymous. 1999. Fiskobirlik Bilgi İşlem Kaynaklarõ, Giresun. Ecevit O., Özman S., Hatat G., Okay A.N., Kaya A. and Mennan S. 1996. Karadeniz bölgesinde önemli fõndõk çeşitlerinin zararlõ ve hastalõklara karşõ duyarlõlõklarõnõn belirlenmesi. Fõndõk ve Diğer Sert Kabuklu Meyveler Sempozyumu. O.M.Ü. Ziraat Fakültesi. p. 77-93. Ioachim E. and Bobarnac B. 1997. Research on the hazelnut pests in Romania. Acta Hort. 445:527-536. Işõk M., Ecevit O., Kurt M.A. and Yücetin T. 1987. Doğu Karadeniz Bölgesi fõndõk bahçelerinde entegre savaş olanaklarõ üzerinde araştõrmalar. O.M.Ü. Yayõnlarõ No. 20, 95 p. Özman S.K. and Toros S. 1997. Life cycles of Phytoptus avellanae Nal. and Cecidophyopsis vermiformis Nal. (Eriophyoidea:Acarina). Acta Hort. 445:493-502. Özman S.K. 1995. Karadeniz Bölgesinde Fõndõk kozalak Akarlarõ [(Phytocoptella avellanae (Nal.) ve Cecidophyopsis vermiformis (Nal.) (Eriophyoidea:Acarina)] üzerinde populasyon değişimleri ve konukçu ilişkileri ağõrlõklõ ökolojik araştõrmalar. Yayõnlanmamõş Doktora Tezi, Ankara Univeristy, Ankara. 186p. Stamenkovic S., Milenkovic S., Pesic M. and Mitrovic M. 1997. Population dynamics, harmfulness and control of Phytoptus avellanae (Nalepa) in western Serbia. Acta Hort. 445:521-526. Tavella L., Arzone A., Sargiotto C. and Sonnati C. 1997. Coreidae and Pentatomidae harmful to hazelnuts in northern Italy (Rhynchota heteroptera). Acta Hort. 445:503510. Tuncer C. 1992. Amerikan Beyaz Kelebeği (Hyphantria cunea Drury, Lep.: Arctiidae)’nin Samsun ve Çevresindeki Biyolojisi ve Özellikle Konukçu Bitkilerin Değişik Açõlardan Etkileri Üzerinde Araştõrmalar. Basõlmamõş Doktora Tezi, 149p. Tuncer C. and Ecevit O. 1996. Fõndõk zararlõlarõ ile mücadelede entegre model tasarõmõ. Fõndõk ve Diğer Sert Kabuklu Meyveler Sempozyumu, Samsun. p. 40-54. Tuncer C. and Ecevit O. 1997. Current status of hazelnut orchards. Acta Horticulturae 445:545-552. Tuncer C., Ecevit O. and Akça İ. 1997. Observations on biology of the filbert aphid (Myzocallis coryli, Homoptera:Aphididae) in hazelnut orchards. Acta Hort. 445:485492.
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Tables
1. Population density and fluctuation of C. nucum in four districts of Samsun during 1997-1998 (mean number of adults/10 ocak). Date April 18 May 5 May 18 June 2 June 20 July 1 July 25 Total
1997 Çarşamba Ondokuzmayõs Salõpazarõ Terme 0 0 0 0 0 0 1 0 4 1 3 3 8 2 5 4 6 3.5 6 3 1 1.4 1 1 0 0 0 0 19 7.9 16 11
Mean 0.00 0.25 2.75 4.75 4.62 1.10 0.00
1998 Date Çarşamba Ondokuzmayõs Salõpazarõ Terme April 22 0 0 0 0 May 5 3 0 4 0 May 24 5 2 3 1 June 7 2 3 2 2 June 21 1 0 1 0 July 10 0 0 0 0 Total
11
5
2. C. nucum damage (%) prior to harvest in four districts of Samsun province in 1998. Districts Çarşamba Ondokuzmayõs Salõpazarõ Terme Mean
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Healthy 73.2 76.2 72.6 72.8 73.7
Empty 16.3 11.2 10.6 8.2 11.6
Browned 0.5 2.3 0.5 1.2 1.1
C. nucum damage (%) Blackened Holey 8.9 1.1 10.3 0.0 13.8 2.5 17.8 0.0 12.7 0.9
Total 10.5 12.6 16.8 19.0 14.7
10
3
Mean 0.00 3.00 2.75 2.25 0.50 0.00
3. Big bud mite in four districts of Samsun province in 1997 and 1998. District Çarşamba Ondokuzmayõs Salõpazarõ Terme
Numbers of orchard visited 8 4 7 7
Mean number of big buds per trunk 1997 1998 4.9 3.7 6.4 4.6 1.4 2.0 4.6 3.3
4. Adult emergence of X. dispar during the growing season in Samsun province. Ocak 1 2 3 4 5 Mean
Percentage of adults exiting 4 April-7 May
27.8 27.7 21.4 60.0 12.5 29.9
7May-7June
11.1 0.0 21.4 0.0 37.5 14.0
7 June- 14 July
44.4 61.1 42.8 20.0 25.0 38.7
14 July-3 August 3 August-7 Sept.
16.7 11.1 14.3 20.0 25.0 17.4
0.0 5.5 0.0 0.0 0.0 1.1
5. Number of hazelnut twigs injured by O. linearis in four districts of Samsun province. District Year Çarşamba Ondokuzmayõs Salõpazarõ Terme 1997 7.9 6.7 10.7 9.1 1998 9.3 4.6 8.4 14.0
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1997
O.mayõs
Salõpazarõ
1998
Çarşamba
8 7 6 5 4 3 2 1 0
Terme
No. of infested trunk/ocak
Figures
1997
O.mayõs
Salõpazarõ
1998
Çarşamba
8 7 6 5 4 3 2 1 0
Terme
Mean number of bugs / 10 ocak
1. Mean infestation of hazelnut trunks by X. dispar during 1997 and 1998.
2. Population of pentatomid bugs in hazelnut orchards of Samsun province during 1997 and 1998.
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