Biological and Chemical Research Institute, Department of Agriculture, Rydalmere, N.S.W., 2116, Australia

Phytophagous mites and their predators in an apple orchard at Bathurst (N. S. W., Australia)

11. The influence of a ryania-captan-benomyl spray schedule

By E. SCHICHA

With 3 figures

Abstract

Populations of three native mites (Acarina: Phytoseiidae) and Stetborus spp. (Coleoptera: Coccinellidae) were studied on Granny Smith apple trees in an experimental orchard at Bathurst, New South Wales, Australia, during the 1973-1974 growing season. Typhlo- dromus helenae Schicha and Dosse was the dominant predator of Tetranychus urticae (Koch) (Tetranychidae). Smaller numbers of Phytoseius fotheringhamiae Denmark and Schicha, Amblyseius lentiginosus Denmark and Schicha, and Stethorus sp . developed late in the season. A spray programme of ryania, captan and benomyfallowed native phytoseiid mites to survive and led to better control of T. urticae than that obtained during the two previous growing seasons when a ryania-captan-dinocap spray schedule was used (SCHICHA 1975b, 1975~). The influence of these pesticides on the microfauna of the apple trees is discussed.

1 Introduction

Commercial apple orchards at Bathurst, New South Wales, Australia, have been sprayed with insecticides such as azinphos-methyl and carbaryl during the past ten to thirteen years to prevent damage to the fruit by pests like codling mot'h, Cydia pomonella L., and light-brown apple moth, Epiphyas postvittana (Walker). Other insecticides such as DDT have also been applied against apple dimpling bug, Campylomma livida Reuter, and plague thrips, Thrips imaginis Bagnall, while fungicide sprays have been used agaihst powdery mildew, Podosphaera leucotricha, and apple scab, Venturia ine- qualis.

The broad spectrum insecticides, DDT, carbaryl and azinphos-methyl in particular,_have completely eliminated native mite and insect predators of two-spotted mite, Tetranychus urticae (Koch). T. urticae has therefore as- sumed considerabie economic importance, requiring two to three applica- tions of acaricides each year to control it (READSHAW 1971; UNWIN 1971, 1973). A reduction of the azinphos-methyl dosage per spray application to 0.56 kg/ha, less than half the commonly used dosage, did not result in the development of significant numbers of native mite or insect predators in an

2. ang. Enr. 84 (1977), 38-47 @ 1977 Verlag Paul Parey, Hamburg und Berlin ISSN 0044-2240 I ASTM-Coden ZANEAE

Phytophagous mites and their predators in an apple orchard at Bnthurst 39

experimental orchard at Bathurst from 1971 to 1974 (THWAITE 1976). But on neglected, unsprayed trees T. urticae was limited to less than pest pro- portions by the native phytoseiid mite predator Phytoseius fotheringhamiae Denmark and Schicha (other mite predators, Stethorus spp. and Neuroptera were rare) (SCHICHA 1975a).

Spray programmes during the 1971-1972 and 1972-1973 seasons in another experimental orchard incorporated the insecticide ryania as a re- placement for azinphos-methyl, with the fungicides captan and dinocap. That allowed predacious Stethorus spp. to survive in large numbers and limit T. urticae populations. Native predacious mites developed at the end of the growing seasons when spraying had ceased (SCHICHA 1975b, 1975~) .

During the 1973-1 974 investigation, dinocap was replaced by benomyl because benomyl was thought to be less detrimental to native phytoseiid mites; ryania and captan were applied again. The new spray programme allowed phytoseiid mite populations to survive better than during previous years. This paper discusses their importance in the natural control of T. ur- ticae during that season.

2 Materials and methods

The studies were made in an experimental block of 159 mature apple trees (cv. Granny Smith and Jonathan) a t Bathurst Agricultural Research Station. This block was used continuously from 1966 to 1973 in studying different methods of integrated control of apple pests. Its spray history has been dealt with in SCHICHA (1975b).

Fifteen Granny Smith apple trees were selected on the basis of similarity in the initial mite fauna, and divided into three plots of five trees each. All three were sprayed in spring 1973 with one application of copper oxychloride (0.40/0 Cu) against apple scab; four applications of benomyl (0.025 O/OJ at approximately fortnightly intervals against powdery mildew and apple scab; m e application of naphthalene acetic acid (NAA 40 ppm) for chemical crop-thinning; and one application of ryania (0.6 C/o) for the control of codling moth (see figs. 1-3). From the beginning of November the spray schedule of the three plots differed markedly. The control plot remained unsprayed for the rest of the season. The other two plots were sprayed a t approximately fortnightly intervals: one, the ryania plot, received ryania (0.60/0) plus captan (0.1 V o ) until mid-January, 1974, then three ryania applications until mid-February (fig. 2). The other, the captan plot, received captan (0.1 O/o) plus ryania (0.6 O/o) until mid-January, 1974, then three captan applications until mid-Februar (fig. 3).

At two-weekg intervals, from November, 1973 to April, 1974, 20 leaves were sampled at random from the lower section of each of the trees. The leaves were taken alternately from the inner and outer branches of all four quarters of the trees. Both leaf surfaces were examined by stereomicroscope a t 20 to 50 times magnification for the presence of mites and the larvae and pupae of Stethorus spp. Population densities of mite species were determined by counting the numbers of different developmental stages per 100 leaves. However, eriophyid mite densities were determined by counting the percentage of leaves infested with mites per 100 leaves (figs. 1-3; table).

3 Results

3.1 Population trends in the control plot

On the control trees, T. helenae was the dominant predator (fig. 1, table). It showed one population peak in November, 1973 followed by a sudden

40 E. Scl?icha

v) w z W ~ 100-

P a a

0

W

v) W

P !i 10-

t; a m W

t

decrease to near zero in December. The populations then increased quickly to a second peak, paralleling the development of T. urticae populations and indicating a close predator-prey relationship between the two species.

Other predacious mite species were absent during the first half of the season. Only in February and March did A. fentiginosus and P. fothering- hamiae develop. Both populations increased during February and reached their peak at the end of the growing season in April. P. fotheringhamiae populations, however, showed a somewhat slower increase.

Eriophyid and tydeid mites were an additional source of food for the predacious mite species (table). Tydeid mite densities increased steadily from November onwards until they reached a high peak at the beginning of

......... Amblyseius lentiginosus m . ~ , ~ .

,.I. * \ Phytoseius fotheringhamiae ,' \ - . o .vDs..

I \

Stelhorus spp. ' . .-.

....

C0.B' B B*NAA B+R*

1 1 1 1 1 1

I ..-• . i : ' '$ s z : ; I . . . . $ 2 :

1 1 1 1 I I I I I I I 1

.___-_. Tetranychus urticae . i u n l .

.-. Typhlodromus helenae -.bl,. st's.. I0001

Sept Oct Nov Dec Jan Fe b Mar Apr

1973 1974

Fig. 1. Population trends of T. wrticae on leaves of sprayed Granny Smith apple trees at Bathurst in the 1973-1974 growing season under the influence of the activity of three native species of predacious phytoseiid mites and Stetborus spp. Control plot; no sprays from November until the end of the season. - B = benomyl 0.025 O/o, C = captan 0.1 O/o,

Co = copper oxychloride (0.4O/o Cu), NAA = a-naphtalene acetic acid 40 ppm, R = ryania 0.6 O/o, * = wetting agent (agrd)

February. They then decreased slightly until April. Low densities of erio- phyid mites were present in the first half of November. From then until mid-December none were observed. But their populations increased again to rea& peaks in January andFebruary before a dramatic decline to zero.

The first eggs, larvae and pupae of Stethovus spp. were seen very late in the season. In Mar& sufficient T. uvticae had developed to allow the beetles to increase in numbers during the month.

Phytophagous mites and their predators in an apple orchard at Bathurst 41

1000-

v) W

W -I

0

Lz W a

s 0

3.2 Population trends in the ryania plot

. - - - - - .

.-1

. A .-. Go 6. 6

1 1 1

T. helenae populations showed a similar trend to those of the control plot, but they had a small additional peak in early January. There were other differences. The main population increase of T. helenae occurred a fortnight later and it did not follow the T. urticae populations as closely as in the control plot. A . lentiginosus developed a fortnight earlier, its population peak occurring in March. The T . urticae populations began to develop four weeks later but showed a faster increase and reached a higher peak in March. Stethorus spp. developed at the same time but their peak was slightly higher. P. fotheringhamiae was not recorded during the year (fig. 2, table).

Tydeid and eriophyid mites showed a similar trend in their development to those of the control plot, but the following differences were observed. Tydeid mites were absent during December. Their main increase in numbers occurred three weeks later and their peak in February was lower. Eriophyid mite populations recovered three weeks earlier immediately after a decline to zero in late November but their second population peak in February was lower and they disappeared in mid-March (table).

0 W 0

5 LL lo- 0 Lz

.... i J : i 2 i $ 2 ;

Tetranychus urticae -dU(,,

Typhlodromus helenae -.w. .TnI..

Amblyseius lentiginows ...L.I.

Stethorus SPP ,. ."... L Y e O .

6 c c c c 6' R* R R R R R k

1 I 1 1 I L 111 il

Fig. 2. Ryania plot; from November until mid-January four applications of ryania plus captan, then three ryania sprays until mid-February

3.3 Population trends in the captan plot

T. helenae populations had a similar trend to those of the control plot, but the species was not recorded during the four weeks between late December and late January. Other differences were that during February and the beginning of March T. helenae populations were suppressed and did not closely follow the T. urticae development. A. Zentiginosus and P. fotheuing-

42 E . Schicha

1. urticae, tydeid and eriophyid mites on leaves of Granny Smith apple trees at Bathurst spp. (Counted were the number of stages

30. 10. O R

T. urticae Tydeidae Eriophyidae

T. helenae T. helenae T. helenae T. helenae A. lentiginosus P. foth. Stethorus spp.

adults adults & nymphs 010 of infested leaves adults nymphs larvae eggs mobile stages mobile stages larvae & pupae

- - 2 - 3 6

10 10 9 9 3 2 5 5 - - - - - -

Date

O R 20. 11.

C 20. 12.

O R C

2 - - 1 8 - 5 - 8 4

(0 = Control plot (cf. fig. 1); ii = Ryania plot (cf. fig. 2); C = Captan plot (cf. fig. 3)

hamiae populations declined from late February onwards. During February and March T . urticae populations increased to a higher peak than in the control plot but later in the season. Stethorus spp. developed two weeks earlier than in the control plot and had a later and higher peak at the beginning of April. Eriophyid mites were absent during November (fig. 3; table).

1000

m w

W _I

2 0 100 0 III u n m w 0

m F ;; 10'

s a m w

z

.------. Tetranychus urticae .dull,

Typhlodrornus helenae m.~,l. .,.,.. Arnblyseius lentiginosus ,,.... Phytoseius fotheringhamiae n.b,l. ,,...,

.-. _._______. _--- ,---- -. . . . . . . . . .. I D . _ . _ . _ . _ D

Stethorus spp. I..~~..~~... .-. R R R R

Go. B* B BWAA B* c c c

1 1 1 / 1 1 1 1 1

Sept Oct Nov Dec J a n Fe b Mar Apr

1973 1974

Fig. 3. Captan plot; from November until mid-January four applications of ryania plus captan, then three captan sprays until mid-February

Phytophagous mites and their predators in an apple orchard at Bathurst 43

in the 1973-1974 growing season, preyed upon by native phytoseiid mites and Stethorus per 100 leaves at each sampling date)

21 .1 . 5. 1. 20. 2. 14. 3. 3. 4. O R C O R C O R C O R C O R C

I 8 11 8 17 105 42 22 390 520 25 580 74C 21 86 720

100 33 50 393 135 155 363 150 250 175 78 140 92 47 94 Prey 12 18 23 15 35 34 17 35 36 7 - 12 - - -

- - - 13 2 4 80 31 22 110 78 80 190 130 130 - - - 12 - 2 62 28 18 64 50 15 48 54 52 - - - 5 - 3 22 12 10 13 13 5 2 4 1 - - 21 2 23 70 30 21 56 64 24 33 21 4; 'red- - 2 1 - 7 8 21 8 42 32 41 1 1 36 22 9

- - - - - - 1 I 3 19 29 24 4 5 34 - - - 3 - 1 4 - 5 2 1 - 1 3 1 - 2

3.4 Population trends of T. helenae

The numbers of eggs, larvae, nymphs and adults of T. helenae in the ryania plot and in the captan plot showed a similar trend to those of the control plot. However, all graphs of the developmental stages show that the popu- lations are somewhat depressed in the ryania plot, and even more in the captan plot (table).

4 Discussion

During 1971-1973 it appeared that dinocap was toxic to native phytoseiid mites on apple trees at Bathurst (SCHICHA 1975b, 1975~). In other countries dinocap has shown acaricidal properties and is highly toxic to predacious phytoseiid mites (MORGAN et al. 1958; DOWNING 1966; DABROWSKI 1968, 1970) so it was decided to exclude it from integrated control experiments at Bathurst. This is contrary to practices in America where it has been used as a selective miticide in apple orchards (ROCK and YEARGAN 1972).

Dinocap was replaced by benomyl in the 1973-74 season in the same experimental orchard at Bathurst, while ryania and captan were applied again. Benomyl is known to reduce the hatch of eggs of T. urticae (SPADA- FORA and LINDQUIST 1972). In America, however, it has had a moderate to severe effect on various life stages of the phytoseiid mite predator Am- blyseius fallacis (Garman) (NAKASHIMA and CROFT 1974). We applied be- nomyl only in September and October, 1973 in the hope that it might suppress the early development of T. urticae but not unduly impair the phytoseiid mite populations. As a result, native phytoseiid mites survived in larger numbers than in the previous two years. T. urticae populations began to develop relatively late in summer - in January, after benomyl application had ceased - and increased to only one peak at the end of the growing season. This was contrary to the two previous years, when this mite developed in the same blocks as early as November, with one peak in No-

44 E. Scl~ich~1

vember and a second one in February (the peaks were closely followed by increases in the populations of Stethovus spp., which ultimately controlled T. uvticae) (SCHICHA 1975~). The late appearance of T . uvticae during this 1973-1974 season might, in addition, have been assisted by the unusual wet conditions at Bathurst. Rainfall from October to February was extreinely high and well above the past 100-year average. These were hardly ideal conditions for a mite species which is known to thrive best in hot, dry con- d’ itions. ’

The spray history of the experimental orchard block (SCHICHA 1975~) had a major influence on the composition of the mite-predator complex during 1973-1974. While on neglected apple trees which had never been sprayed with pesticides, P. fothevinghamiae has been the dominent predator from 1971 to 1974 (SCHICHA 1975a), T. helenae has been the most abundant mite predator in the experimental block. Predators of lesser importance were P. f otheringhamiae, A . lentiginosus and Stethorus spp. which occurred only from January to April, 1974.

The 1973-1 974 spray programme, especially, seems to have influenced the development of native phytoseiid mites. In the spring of 1973, after one copper oxychloride, one ryania, one NAA and four benomyl sprays had been equally applied in all three plots, T. heienae remained the only preda- tor on the leaves. It declined to near zero numbers in December in all three plots. This seems to be a reaction tc the declining numbers of eriophyid and tydeid mites, but also a result of the suppressing effect of the sprays on the predator and/or the prey. Ryania does not seem to have had a noticeable harmful effect on T. helenae in the spring, unlike its influence on phytoseiid mites in other countries (MORGAN and ANDERSON 1957; BARTLETT 1964). Captan was not unduly toxic to predacious mites in other countries (MUIR 1965; OATMAN 1973) but in the spring it seems to have had some depressing effect on T. helenae in our experimental block. This was already suspected in the 1972-1973 investigations (SCHICHA 1975~).

During summer and autumn 1973-1974, T. helenae populations did not follow the T. urticae populations as closely in the ryania plot as they did in the control plot. P. fotheringhamiae was completely absent in the ryania plot, while present in the control plot late in the season. In the captan plot T. helenae, A. lentiginosus and P. fotheringhamiae populations seem to have been suppressed by the last three captan sprays. It appears therefore that ryania impaired the development of P. fotheringhamiae and that captan suppressed all three native predaceous mite species. All life stages of T. he- lenae, eggs, larvae, nymphs, and adults, were suppressed in the captan plot by the last three captan sprays, while they were less suppressed by the last three ryania sprays in the ryania plot.

In the three plots T. helenae populations showed similar trends, with a peak in mid-November, followed by a dramatic decline to near zero in December. In all plots they had a rapid increase approximately four weeks later at the end of January. T. helenae populations seem to follow the developmental trends of food mites as during their decline, the eriophyid and tydeid mites (the only food available) had their lowest densities for the year. From December onwards T. helenae increased in numbers together with eriophyid mites, tydeid mites, and T. urticae. Although T. helenae was observed feeding on eriophyid and tydeid mites, a close predator-prey relationship was not established in this investigation as it was in the summer

Phytophugous mites und their predutors in an apple orchard at Ratburst 45

and autumn 1972-1973 (SCHICHA 197%). However, eriophyid and tydeid mites always occurred together with T. helenae on the leaves, and during 1973-1974 they were a supplementary food supply. The principal prey of T . helenae during summer and autumn 1973-1974 was T. urticae, and here a close predator-prey relationship was observed.

The T. urticae populations showed a similar trend in the three different plots, appearing during December and January and reaching a single peak in March. The highest peak occurred in the captan plot, the second highest in the ryania plot, and the lowest in the control plot. This is probably a reflection of the different activity of the predators in the plots: the larger the number of predators (especially of T. helenae) the fewer the numbers of T . urticae. Stethorus spp. appeared very late in the season, in March, in low densities in all plots. The beetles were not influenced by either of the sprays. But their impact on T. urticae was minimal because of their low numbers and late appearance, in comparison to previous seasons.

Leaf damage by T. urticae, assessed in March 1974 in all plots, was con- sidered economically insignificant. The least damage was observed in the control plot, and the other two showed only slightly more leaf mottling. The three native predacious phytoseiid mite species, particularly T. helenae, which occurred on the Granny Smith apple trees at Bathurst in 1973-1974, were the most important biological control agents of T. urticae.

5 Conclusions

These and previous observations show that native phytoseiid mites on sprayed apple trees at Bathurst can only be studied when experimental orchards are submitted to a special spray programme. In selected orchards a spray programme should be applied which is similar to the 1973-1974 programme reported here. It would include captan against apple scab, and benomyl at the beginning of the season, when powdery mildew is most troublesome. This would keep the trees free of fungus diseases. Cultural methods could include slashing, fertilizing, and pruning but broad spectrum insecticides or superior winter oil should not be applied. Since this would lead to the development of codling moth, ligth-brown apple moth, thrips, and apple dimplin bug to pest proportions, the young fruit from such

commercial orchards (ryania is not very effective against codling moth). Such “clean” trees would then develop populations of native phytoseiid predacious mites during the first or consecutive seasons. Particularly in the latter half of the year the three most common phytoseiid mite predators, T. helenae, P. fotheringhamiae, and A. lentiginosus would be abundant. Field trials could then be conducted on the influence of pesticides on these predators, involving (only) one field trial every year towards the end of the growing season. This is now thought to be the only method available for testing pesticides against native phytoseiid mites from apple trees at Ba- thurst, since it is extremely difficult to mass culture these mites. They could be collected from the trees and tested in the laboratory, but the advantage of the above method is that in field trials the influence of pesticides on the whole microfauna and flora could be studied.

trees would have to gb e removed to avert a threat by the pest species to other

46 E . Schicha

Zusammenfnssung

Phytophage Milben und ihre Pradatoren in einer Apfelanlage bei Bathurst (N.S.W.: Austyalien). 11. Wirkctngen von Bekampfungsmajlnahmen mit Ryania-Captan-Benomyl-

Sprays auf die Populationen Es wurden die Populationen der phytophagen Milbe Tetranychus urticae (Koch) und

ihrer wichtigsten Pradatoren in einer Granny-Smith-Apfelanlage bei Bathurst wahrend der Vegetationsperiode 1973-1 974 untersucht, als die Anlage einer kombinierten Spray- aktion mit Ryania, Captan und Benomyl unterworfen wurde. Bei Abwesenheit breiten- wirksamer Insektizide und Acarizide wurde T . urticae hauptsachlich von rauberischen Milben der Familie Phytoseiidae, und nur zu geringem MaBe von Marienkafern (Stethorus spp.), reguliert. Als haufigste Raubmilbe trat Typhlodromus helenae auf.

Das Sparprogramm dieser Saison erlaubte es, daK rauberische Milben besser iiberlebten als wahrend vorjahriger okologischer Untersuchungen, und das Programm kann nun als Grundlage fur gezielte Experimente uber die Wirkung von Pestiziden auf einheimische rauberische Milben dienen.

References

BARTLETT, B. R., 1964: The toxicity of some insecticide residues to adult Amblyseius hibisci, with a compilation of the effects of pesticides upon phytoseiid mites. J. econ. Ent. 17, 559-563.

DABROWSKI, 2. T., 1968 : Badania nad toksycznoscia pestycydow stosowanych w sadach w Polsce dla roztoczy drapieznych (Phytoseiidae). Roczn. Nauk Rolniczych 93 (A),

- 1970: Badania nad dzialaniem nastepczym pestycydow na przedziorki (Tetranychidae) i drapiezne roztocze (Phytoseiidae) w sadach jabloniowych. Roczn. Nauk Rolnictych, Seria E, 1, 7-26.

DENMARK, H. A.; SCHICHA, E., 1974a: A new species of Amblyseius Berlese (Acarina: Phytoseiidae) from apple in Australia. Proc. Linn. SOC. N.S.W. 99, 145-150.

- 1974b: A new species of Phytoseius Ribaga (Acarina: Phytoseiidae) from apple in Australia. Proc. Linn. SOC. N.S.W. 99, 177-180.

DOWNING, R. S., 1966: The effect of certain miticides on the predacious mite Neoseiulus caudiglans (Acarina: Phytoseiidae). Can. .J. P1. Sci. 46, 521-524.

MORGAN, C. V. G.; ANDERSON, N. H., 1957: Some aspects of a ryania-glyodin spray schedule in British Columbia apple orchards. I. Entomological, horticultural, and economic aspects. Can. J. PI. Sci. 37, 423-433.

MORGAN, C. V. G.; SWALES, J. E., 1958: Influences of some fungicides on orchard mites in British Columbia. Can. .J. P1. Sci. 38, 94-105.

MUIR, R. C., 1965: The effect of sprays on the fauna of apple trees. I. The influence of winter wash, captan, and lime-sulphur on the interaction of populations of Panonychus ulmi (Koch) (Acarina: Tetranychidae) and its predator, Blepharidopterus angulatus (Fall.) (Heteroptera: Miridae). J. appl. Ecol. 2, 31-41.

NAKASHIMA, M. J.; CROFT, B. A., 1974: Toxicity of benomyl on the life stages of Arnbly- seius fallacis. J. econ. Ent. 67, 675-677.

OATMAN, E. R., 1973: An ecological study of arthropod populations on apple in north- eastern Wisconsin: population dynamics of mite species on the foliage. Ann. Ent. SOC. Amer. 66, 122-131.

READSHAW, J. L., 1971: An ecological approach to the control of mites in Australian orchards. J. Aust. Inst. Agric. Sci. 37, 226-230.

ROCK, G. C.; YEARGAN, D. R., 1972: Laboratory studies on toxicity of dinocap to Neo- seiulus fallacis and its prey. J. econ. Ent. 61, 932-933.

SCHICHA, E., 1975a: Bionomics of Phytoseius fotheringhamiae Denmark and Schicha, 1974 IAcarina: Phvtoseiidae) on a d e in Australia. 2. ang. Ent. 78, 195-203.

655-670.

- 1975b: Predacious rniies [Acarina: Phytoseiidae) on sprayed apple trees at Bathurst (N.S.W.). J. Aust. ent. SOC. 14, 217-219.

- 1975c: Phytophagous mites and their predators in an apple orchard at Bathurst (N.S.W., Australia). I. The influence of a ryania-captan-dinocap spray schedule. 2. ang. EnL. 78, 7974119 -_ . .-,.

SCHICHA, E.; DOSE, G., 1974: A new species of Typhlodromus Scheuten (Acarina: Phyto-

SPADAPORA, R. R.; LINDQUIST, R. K., 1972: Ovicidal action of benomyl on eggs of the seiidae) from apple in Australia. Proc. Linn. SOC. N.S.W. 99, 79-84.

two-spotted spider mite. J. econ. Ent. 61, 1718-1720.

Phytophagous mites and their predators in an apple orchard at Bathurst 47

'FHWAITE, W. G., 1976: Effect of reduced dosage of azinphos-methyl on control of codling moth, Cydia pomonella (L.) and light-brown apple moth, Epiphyas postvittana (Walk.) in an apple orchard. 2. ang. Ent. 80, 94-102.

UNWIN, B., 1971 : Biology and control of the two-spotted mite, Tetranychus urticae (Koch). J. Aust. Inst. Agric. Sci. 37, 192-211.

- 1973 : Chemical resistance in populations of Tetran,ychus urticae (Koch) (Acarina: Tetranychidae) from apple orchards in New South Wales, Australia. .J. Aust. ent. SOC. 12, 59-67.

Aus dem Institut fur Forstentomologie und Forstschutz der Universitat fur Bodenkultur, Wien

Einspinnen und Oberwinterung der 1. Generation der Gewohn- lichen Kiefernbuschhornblattwespe, Diprion pini Linnaeus (Hym., Diprionidae) in der Baumkrone der Weii3kiefer

(Pinus sylvestris Linnaeus)

Von A. KURIR

Mit 7 Abbildungen

Abstract

Spin and overwintering of the first generation of Diprion pini in the tree-crown of Pinus sytwestris

In the localities with mixed populations was Diprion pallidum between 94.91, and 95.41 O/o

and D . pini between 4.58 and 5.08 O/o present. D . pini in the first generation spin the cocoons as a rule individuel (never collectively);

cocoons on the bare branches: individual 99.18 O i o , by pairs (exceptionaly) 0.61 O/o; on thin branches 50.31 O/o, in branch-twirls 30.43 O/o, below the wreath of the buds on the lateral- shoots 18.01 O/o, upwards then 0.62 O/o and on the rest of leafs 0.62 O/o.

The preferable spin on the thin branches in diameter: between 2.00/0 and 2.9O/o mm 34.96 O/o, between 3.0 and 3.9 mm 31.28 O/o, between 4.0 and 4.9 mm 14.72 O/o.

Position of heads in the cocoons on the shoots: upwards 81.01 O/o, downwards 14.04 O/o,

lateral 4.13 O/o. Colour of cocoons: after the overwintering in the tree-crown: faint dark brown. The parasitism in the cocoons 21.11 O/o, the predatory on the cocoons 1.24 O/o.

1 Einleitung

Anlai3lich der Gradation der Blassen Kiefernbuschhornblattwespe (Diprion pallidurn Klug) in Unterkarnten 1969-1972 (KURIR 1975) gab es ma.nche Lokalitaten, wo auch die Gewohnliche Kiefernbuschhornblattwespc (Di- prion pini Linnaeus) vertreten war. Und genauso wie bei D. pallidurn vor-

2. ang. Ent. 84 (1977), 47-52 @ 1977 Verlag Paul Parey, Hamburg und Berlin ISSN 0044-2240 I ASTM-Coden ZANEAE