On Wheat and Barley in Northern Syria

Incidence of Wheat Stem Sawflies and Their Natural Enemies on Wheat and Barley in Northern Syria

R.H. Millerr, Samia El Masri2, K. At Jundi2.

(1) Cereal improvement Program, International Center for Agricultural Research in the Dry Areas, P.0. Box 5466, Aleppo, Syria

(2) Faculty of Agriculture, Tichrin University, Lattakia, Syria

Abstract Miller' R.H.; S. El Masri and K. Aljundi. 1992. Incidence of VYheat Stem Sawflies and their Natural Enemies on Wheat and Barley in Syria. Arab J. Pl. Prot. 10 (1): lO- 25

Durum wheat (Triticum turgidum L. var. durum). bread lies were collected from late March until early May. Para- wheat (Triticum aestivunt L.) and barley (Hordeum vulgore sitoids appeared several days after sawflies and generally L.) fields were sampled for stem sawflies in northern Syria in reached their maximum numbers coincidentally with T. 1987188 and 1988189. Collections from yellow water traps judaicus in wheat. C.pygmeaus was the most frequently trap- contained Cephus pygmoeus L.,Trachelus judaicu.r konow, ped sawfly with T. judaicw second. Dry,cold weather condi- and Trachelus libanensis Andre (Hymenoptera: Cephidae) as tions in L988189 contributed to lower sawfly catches than in well as the parasites Collyria coxator Villers and Collyria 1987188. Peak sawfly emergence both years corresponded to a orientator Aubert (Hymenoptera: Ichneumonidae), and Bra- level of wheat development optimal for sawfly attack. con terebrella Wesmael (Hymenoptera: Braconidae). Sawf- Key words:Barley. natural enemies. sawflies. wheat.

Materials and Methods Introduction Field surveys were conducted in breat wheat, durum wheat Wheat in Syria is commonly infested by a number of insect and barley fields at ICARDA's 1000 ha main research station pests that frequently cause either relatively minor damage located near the village of Tel Hadya ( 36" 01'N, 36" 56'E. over large regions or severe damage over small areas. The elevation2S4 m) approximately 26km south of Aleppo, Syria European wheat stem sawfly, Cephus pygmaeus L. (Hyme- during the cropping seasons of 1987188 and 1988189. The noptera: Cephidae), is one of the more serious pests infesting ICARDA farm is characterized by phosphorus-deficient cal- wheat and barley in the rainfed areas of northwestern Syria, careous soils, medium to heavy in texture (Cooper et al., although it is not the only stem sawfly that attacks cereals in 1987). The long-term rainfall average for the Tel [{adya farm the region (Benson, 1968; Gentry, 1965; Hariri , 1971; Miller. is about 350 mm. occurring mainly between october and 1991). Wheat stem sawfly infestations as high as 38 % in April. The area experiences a Mediterranean-continental cli- barley and 28 Vo in wheat were recorded near the village of mate. with summer temperatures approaching 40 C during Suran, about 40 km south of Aleppo (Rashu'ani. 1983). From July and August and winter temperatures occasionally de- 1986 to 1990 wheat stem sawfly' infestations averaged about scending below - 5o C. Wheat and barley in northern Syria 20 % in wheat and barlv in farmers' fieldsnear Aleppo and at are normally sown from late October through early December ICARDA's main research farm at Tel Hadya, in the moder- following the first autumn rains. Barley is harvested in late ate rainfall zones (250 mm to 350 mm) of northern Syria (R. H. May and is followed by wheat harvest in early June. Miller, unpublished data). Infestations at ICARDA occa- Adult sawflies were collected throughout the spring flight sionally reached as high as 10 Vc (ICARDA, 1987). In addi- season in round yellow plastic basins (27 cm wide by 8 cm tion, sawfly infestations up to 22 7o have been observed in deep) filled with soapy water. Two traps were placed along farmers' fields in wild grasses bordering wheat and barley each of 3 field edges I m from the crop of each barley, bread fields (ICARDA, 1988). wheat, and durum wheat field sampled during 1987/88 and The purpose of this study' \,\:as to describe the incidence and 1988189 in early March before the flight season began. An phenology of wheat stem sawflv and some of its natural ene- additional three traps were placed along a transect within each mies in wheat and barley fields at ICARDA's primary re- field at 50 m intervals, making a total of nine traps perfield. search farm in northern Syria Sawflies were removed from the traps twice a week and

30 : l0 preserved in 70 Vo ethanol. Counts and preliminary identi- Results and Discussion fications were made in the laboratory at ICARDA, with C. pygmaeus L., Trachelus judaicus Konow,and Trachelus confirmation of identification provided by staff of the British libanensrs Andre (Hymenoptera: Cephidae) were identified Museum of Natural History, London. Plant height and crop from water trap catches in 198188 and 1988189 (Table L). developmental stage (Zadoks scale;Zadoks et al .,1974) were Calamenta idolon Rossi (Hymenoptera: Cephidae) and an recorded at each sampling interval. unidentified Trachelus sp. near libanensts were also collected on the Tel Hadya farm in sweep nets but were never found in Weather data were collected from a centrally located water traps. More sawflies were trapped in bread wheat than weather station on the ICARDA farm approximatelv 500 m in either durum wheat or barley in 198T88. During the from the wheat and barley fiels sampled for sawflies in this 1988/89 season more sawflies were trapped in durum wheat study. than in bread wheat. In both years the fewest sawflies were trapped in barley.

Table 1. Total wheat stem sau'flies and parasitoids' captured per nine \\'ater traps in durum wheat. bread wheat, and barley in the

198188 and 1988,,89 seasons.

19t7 198t Total 75,2

Durum Wheat 453 486 939 1.1.60n'

C. pygntoeus Bread Wheat 989 375 1364 276.390 * *

Barley 133 192 325 l0.7tt * *

xr 712.6549 * {r t25.6t7 * * 622.961 * *

Durum Wheat 79 277 306 7l .582 * {r

T. Judaicus Bread Wheat r43 209 352 12.37 5 {r *

Barley l0 9I 101 64.960 {r * x t14.422* * 62.132* * t4t.t62* *

Durum Wheat 24 0 24 24.000* *

T. libanensis Bread Wheat 57 0 57 57.000 * *

Barley 0 0 0 0. 000n' x 60.666* * 0.000n' 60.666* {r

" Collvria sp. and B. terebrella n' P > 0.05; 'P < 0.05; ooP < o.ol

The number of parasitoids trapped in the three crops was creasing to 5?'lCI in 1988/g9. proportional to the total number of sawflies captured in that field (r:0.97, df :4, P<0.01; Table 1). Parasite collections Fig. L. shows the species composition of trap catches for consisted primarily of Collyria coxator Villers, and Collyria both seasons in the three crops. In durum wheat (Fig.1A), orientaror Aubert (Hymenoptera: Ichneumonidae), with few- C. pymaezs began flying 14 days earlier than T. judaicus, er numbers of Bracon terebrella Wesmael (Hymenoptera: and 18 days earlier than T. libanensis in 1987188 and numbers Braconidae ) (ICARDA. 1988). were consistently higher. No T. libanensis were captured after May 8, while other sawfly species were captured until May 12. Overall sex ratios of C. pvgmaeus were skewed in favor of Catches of T. judaicus were higher than T. libanensis on most females both vears. The sex ratio of C. pyg^aeus in durum dates. Similar observations were recorded on durum in wheat in 1987 88 r*as 10?:tgf uhile it decreased to 7? lCin 1988/89 (Fig. 1B), except that no ?'. libanensrs were trapped. 1988189. Similarlr'. femdes outnumt'ered males 99'l d in In 1988'89. C. p)'gmaeus appeared in the traps earlier and bread wheat in 1987 88 decreasing to -l:l d in 19,1s s9. \\ ere generallr more numerous than those of T. judaicus until Female sawflies greatlv outnumbered mala ln trap catchc tn 3buru: .{pnl it-r. u he n T. .iudaicus populations began to consis- barley both seasons. averagng J39 .ld rn i96- EE and de- te:il" 3\.-ieci those r-rf C. p: g^aeus.

29 -{.tl .rtJt r,-[i-p _{ 1 e87 /88 120 Du ru m Wheot 100 C. pygmoeus T. judoicus 80 T. libonensis r Porositoids 60

280 240 E 140 q) \- l -+J 120 o_ o (-) 100 \- O _o 80 E _) 60 Z- +o

120

100

flg. 1. Breakdown of water trap catches in durum wheat at Tel Hadya, Syria in 1987/88 (A) and 1988/89 (B); in bread wheat in 1987/88 (C) and 1988/89 (D); and in barley in 198T98 (E) and te88l8e (F).

28 - L:ll .rL.rJl t,_Li-e ib.,. The pattern of sawfly captures in bread wheat in 1987188 for both sawfly species on April 9. and 1988189 resembled that of durum wheat for the sam e year, cnly one parasite was found in any trap in barley on any though catches in 1988/89 were generally lower. In 1987188 C. sampling date and parasitoids first appeared in the traps 'f pygmaeru first appeared on March 31 while . iudaicus several days later than sawflies. No distinguishable peaks of appeared on April 15. There was an obvious peak in C. parasite capture were observed in either season. pygmaeus catches observed on April 28 which coincided ex- Difference in numbers observed between sawfliescollected actly with the greatest catch of parasitoides that season. In in barley,, durum wheat, and bread wheat fields are likely due contrast, numbers of T. judaicus showed no obvious peak and to developmental differences between sawfly species and be- were insignificantl.v- different from those of T. libanensis tween barley, durum wheat, and bread wheat. Barley normal- throughout the season. In 1988189, Do prominent peaks were ly matures more rapidly than durum wheat or bread wheat, obserued in catches of C. pygmaeus. Rather, the number of and may therefore escape the heaviest period of sawlfy flight. insects captured gradually decreased from the initial levels at If the peak adult sawfly density in the field corresponds to the the beginning of the flight season. In constrast, catches of 7'. period when barley is ripening and desiccating, sawflies are judaicus were first observed on April 3 and peaked on April more likely to select succulent younger plants of other cereal 10. Parasite numbers were similar in 1987188 and 1988/89. The specles. grearest number of parasitoids in 1987188 were captured on The peak trap capture of L libanensis occurred relatively April 28 which corresponded to peak capture of C. pygmaeus, late in the growing season, when barley was an unsuitable host though a second smaller peak of parasite capture occurred on because it was ripening and drying out. Past work has shown season. 1988189 the greatest parasite catch May 8 that In that sawflies prefer the elongating internodes of relatively 15, five days after the peak T. occurred on April iudaicus young plants. Holmes and Peterson (1960) suggested that did not appear catch. In both L987188 and 1988/39 parasitoids different development rates in different wheat varieties, the traps until well after the sawfly flight had begun. in grown in North America, caused differences in infestation Trap catches of sawflies and parasitoids in barley were rates between those varieties. substantially lower than those in corresponding years on Peterson et al. (1968) found that adequate soil moisture durum wheat and bread wheat, and T. libanensis was not produced lush plant growth, which in turn resulted in high found on barley in either season. In 1987188 C. pygmoeus was adult sawfly populations and a high (78.5 Vo) rate of stem first trapped on March 29, reached a peak on April 10, and cutting. Conversely, they also found that dry soil conditions was last trapped on May 12 (Fig. lE) . T. iudaicus was first lead to lower sawfly emergence from stubble. The 1987188 captured two weeks later than C. pyg^aeus on April 12 and growing season had good rainfall and adequate moisture for was last captured on April 28. Trap data were insufficient to plant growth (Fig . 2A). This allowed relatively high larval detect any population trends for T. iudaicus.In L988189 C. survival in moist stems. However, the very dry 1988/89 grow- pygmaeus was again captured substantially earlier than T. ing season resulted in rapid plant maturation, generally lower judaicu.r', on March 8 versus April (Fig. 1F). Sawfly numbers grain yield, lower larval survival and a shorter sawfly flight in 1988/89 were low as in 1987l88with peak captures occurring season (Fig .2B-).

B Tel Hodyo Mc-.,nthly We,:tlrer 1ggg,,/ g!) A Tel Roinfotl E Roinfoll E O Min Ternp O Mox Temp V Meon temp O Mox Ternp 100 4C 90 ,r'G-O 15 80 50 YV 30 70 C? L 25 Qrtr 25 \-') 60 oo oo 20 + ?o 9E I 50 \lr o o 15 (J 15 t&'CO 40 V o F o l0 30 o'ooo 5 20 5 10 0

0 _tr .g stP s

Fig. 2. Average monthly rainfall. maxrmumtempeftrture. nummum temperirture. and mean temPerature at Tel Hadya, Syria during te87/88 (A) and te8S/8e (B).

27 -4./l .rLJl i1U.; ilz Ambient temperature, along with rainfall, also affects lar- the season progressed. The highest sawflv collections coin- val survival and adult emergence. Villacorta et al. (1971) cided with the booting-flowering stage in wheat (Zadoks 40 to suggested that rainfall prior to sawfly flight promotes adult 65), approximately March 30 to May 9 in 1987188 and April 2 emergence from stubble when the temperature reaches or to April 18 in 1988189. Should agronomic or environmental o exceeds 12 C, while a temperature of 10o C or less suppres- factors alter adult sawfly flight during this period, or signifi- ses postdiapause development. They also suggested that the cantly alter plant development, plants may then escape signi- developmental threshold for most sawfly populations was ficant sawfly attack through nonselection for oviposition. as about 15o C, and that post-diapause development occurred apparently occurred in barley in 1988/89. within a temperature range C - 28" C. Daill' max- of 15o Parasitism did not seem to significantly affect sawfly imum temperatures were higher in the L988189 season and populations. Gol'berg (1986) reported from 5 Vo to 12 % probably accounted for adult emergence occurring 19 days parasitism in sawfly-infested wheat due to Tetrastichus sp. earlier and the adult flight period being 27 days shorter than in (Hymenoptera: Eulophidae) and Collyri4 sp. in the Negev L987188. T. judaicus appeared later the season than C. in Desert, and Miller (cited in ICARDA, 1988) reported slightry pygmaeus both seasons and was not affected b\' 1988/89's higher parasitism rates of 17 Vo and 5 Vo for Collyria spp. and greater daily fluctuations. drought conditions or temperature B. terebrella in wheat, respectively in northern Syria. Parasite Our data suggest that the peak sawfly flight period was populations observed in this study were likely strongly influ- associated with the wheat plant growth stage optimal for enced by both the number of sawflies available at parasite sawfly selection and oviposition. Females began ovipositing in emergence and by the weather and plant conditions during young plants in the uppermost portion of the lou'er t\r'o inter- their emergence and development. nodes, and then selected progressivelv higher internodes as

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References

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25 -Lll .)liJl qUr il+,