УДК 632:595.771:591.526:632.7.08

PHEROMONE MONITORING OF THE RASPBERRY CANE MIDGE Resseliella theobaldi (Barnes) IN THE CONDITIONS OF NOVOSIBIRSKAYA OBLAST’

A.A. Belyaev, T.V. Shpatova, M.V. Shternshis

The phenology of the raspberry cane midge has been studied and the monitoring has been made by the use of pheromone and water traps under the Novosibirsk region condition. The preference of pheromone traps compared with water ones for the determination of the onset of flight of adult male raspberry cane midge and maximum number of pest was discovered.

Key words: raspberry, raspberry cane midge, pheromone traps, pheromone monitoring.

 

In Western Siberia, raspberry cane midge (RCM) Resseliella theobaldi (Barnes) was first discovered in 1982-1983 in homestead plantings near the city of Biisk and in the industrial plantations of specialized farms in the Novosibirsk Region (1, 2). Earlier, the pest’s natural habitat in the former Soviet Union were the central region of Russia, the Baltics and Ukraine. Midge causes death of up to 80% raspberry canes. In the Novosibirsk region, the massive death or raspberry shoots has been described since mid-1970's. Due to the secretive way of life and small size of adults and younger larvae, only the orange-yellow larvae of older ages are usually visually identified at opening of the cortex near cracks. At the end of feeding, the larvae go into soil for pupation, and the shoots remain damaged with necrotic spots of fungal infection (so-called «midge blight» - a conjugated mycosis complex) (3), which are often misidentified for independent mycosis - purple blotch, stem botritiosis etc.
The effectiveness of protective activities depends on completeness and accuracy of pest monitoring. Entomological manuals for catching adult midges recommended the use of water traps - vessels of 25-30 cm diameter, painted yellow inside (so-called Merike cups) (4, 5). Currently,  there are the actively developing monitoring methods using pheromone traps (6, 7); the traps based on pheromone chemical communication between sexes are considered as the most promising. In Russia, pheromone traps are used to lure lepidopteran pests, as well as beetles (Coleoptera , Elateridae ) and bark beetles Ips typographus L. (6-9). For the phytophagous midges, there are the overseas data on pheromone monitoring of the orange cereal midge Sytodiplosis mosellana Gehin (10).
The purpose of this work - to study the phenology of raspberry can midge using pheromone traps in conditions of the Novosibirsk region.
Methods. The object of research (2006-2007) were the 6-years old industrial plantation of raspberry the variety Zorenka Altaya, grown in the collective farm “Sady Sibiry” (“Gardens of Siberia”; the area of a quarter - 4 hectares), the 11-years old plantings of 15 raspberries varieties grown in Novosibirsk I.V. Michurin  Zonal Fruit-Berry Experimental Station (NZFBES; the area of plantings - 1 ha), the model annual shoots the variety Barnaul'skaya, and the phytophagous pest - raspberry cane midge. Pheromone traps for RCM were kindly presented by Dr. J. Cross (United Kingdom).
Two pheromone traps were placed in the heart of each raspberry quarter at a distance of 20-30 meters from each other so that their base was at a height of 50 cm above the ground. One trap was oriented parallel to raspberry rows, another one - at a right angle (11). Inside the trap, there was a white sticky base (20 Í20  cm). Capsules with 10 mg RCM sex pheromone were hung inside the trap at a height of 5 cm above the base. The capsules were replaced  once a month, and the sticky base - weekly.
Every week in 20 canes of Barnaul'skaya raspberry, a single artificial crack 10 cm long in 30-50 cm above the ground was made using a dissecting needle, and the cracked stripe 1-2 mm width was peeled off to attract midge females.  In 1 and 2 weeks after that, 10 marked shoots were cut off for laboratory counting of pest eggs and larvae in the cracks.
The detailed observations were carried out in the Station; simultaneously with pheromone traps, there were placed three Merike cups in which water was replaced once in 1-2 weeks (as needed). In addition, the pheromonitoring of imago flying was studied in the farm “Sady Sibiry”.
The traps were located in the plantation before the onset of flying the 1st  pest generation in spring (III decade of May), accounts of adults in traps, as well as eggs and larvae in the artificial cracks were performed weekly until the end of pest’s flying at the end of growing season (late September). The number of insects in each trap up to 200 individuals were determined by direct counting, from 201 to 1000 - up to a dozen, more than 1000 - up to hundreds.
Results. Imago. According to the data of accounts in pheromone traps in 2006,  the 1st RCM generation emergence was observed from 28-30 May till the end of III decade of June (maximum - June 6-13), the 2nd generation - from 25 June until the end of II decade of August (maximum - July 25), the 3rd – from II decade of August (was stopped by regular night frosts of September 23-25); in year 2007 – respectively, from 25 May until the end of I decade of July (maximum - in the II half of June, 331.0 ind. per trap, or 1,7 times more than in 2006) (HCP05 = 16.5 ind. per trap), from the II decade of July until the beginning of the III decade (33-125 ind. per trap) and from August 17 to the II decade of September (maximum - September 5, 66,5 ind. per trap) (Fig. 1).


Fig. 1. The dynamics of imago emergency of raspberry cane midge in the surveyed areas by years of study, established upon the data of accounts in pheromone traps and water traps:
1 - Novosibirsk I.V. Michurin  Zonal Fruit-Berry Experimental Station (NZFBES), pheromone traps (PhT), 2007;
2 – the farm “Sady Sibiry”, PhT, 2007;
3 – NZFBES, PhT, 2006;
4 - NZFBES, water traps, 2006;
HCP05 for years = 16.5 ind. per trap; HCP05 for terms = 49.5;   HCP05 for quotient averages = 69,9.
Note:
abscissa – Term of account
under the axis from left to right – May 25, June 13, June 27, July 11, July 25, August 8, August 22, September 5, September 19, September 30
ordinate left – Number of imago ind. per pheromone trap
ordinate right – Number of imago ind. per water trap

During the observation period, the number of imago in the trap located closer to the windward side of a garden quarter was always higher than in the leeward side (due to the greater area of pheromone distribution sector and, consequently, the increased sector of imago gathering).
Upon the data from water traps in 2007, imago emergence was registered in June 5 (0,50 ind. per trap for 1 week), the maximum was reached in the II-III decades of June (0,75 ind. per trap) in approximately the same time periods with pheromone traps. Thus, the efficiency of water traps in June was about 100 times less than for the pheromone traps. Low lure effectiveness of water traps did not allow the identification of imago in early period of flying (delay - about 1 week). The start of flying of the 2nd RCM generation (July 11, 1.00 ind. per trap) was also recorded a week later (maximum - I-II decade of August, 1.67 ind. per trap), 3rd - from August 22 (maximum - August 29, 1.00 ind. per trap); from the 5th to 12th of September, the imago emergence gradually decreased (up to 0.33 ind. per trap), and in the second half of September no adults were detected in water traps.

 

Fig. 2. The dynamics of egg laying in raspberriy cane midge during the growing season (A) and number of larvae in bark cracks  (B) by years of observation: 1, 2 – respectively, 1 - and 2-weeks-old cracks in 2006, 3, 4 – 1- and 2-weeks-old cracks in 2007.
A:  HCP05 for types of cracks = 0,9 eggs per crack; HCP05 for terms = 2,7; HCP05 for years = 0,9.
B: HCP05 for types of cracks = 1,2 larvae per crack; HCP05 for terms = 3,7; HCP05 for years = 1,2 ( Novosibirsk I.V. Michurin  Zonal Fruit-Berry Experimental Station (NZFBES).

Note:
Fig A :
abscissa – Term of account
under the axis from left to right – May 25, June 5, June 13, June 20, June 27, July 4, July 11, July 17, July 25, August 1, August 8, August 15, August 22, August 29, September 5, September 12, September 19, September 26
ordinate – Number of eggs, pcs.per crack
Fig B :
abscissa – Term of account
under the axis from left to right –June 5, June 12, June 19, June 26, July 3, July 10, July 17, July 24, July 31, August 7, August 14, August 21, August 28, September 4, September 11, September 18, September 25
ordinate – Average number of larvae, pcs. per crack

In raspberry plantations of the farm "Sady Sibiry" in 2007, the emergence of 1st RCM imago generation was detected in late May. The maximum of pest flying was identified in the III decade of June (June 23) - 2348 ind. per trap. The 2nd generation flying began on July 14, maximum - 25 July (1057 ind. per trap), and it finished by the III decade of August. The 3rd RCM imago generation was recorded from August 25 (maximum - 12 September: 1443 ind. per trap), and the pest flying was completely stopped by the night frost on September 25. The number of pest imago weekly catch  in raspberry plantations of  the farm “Sady Sibiry” was about 10 times higher than in NZFBES; this fact can be explained by the greater RCM population due to the higher (4 times) area of plantings and the younger age of plants with high intensity of stem growth accompanied with bark cracking  providing conditions for  egg laying and larval feeding.
Egg laying. In both years of observations, the start of egg laying by the 1st RCM generation was recorded in early June (maximum in 2006 -  June 13, in 2007 - June 27) (Fig. 2, A).
 In 2-week-old cracks, the number of eggs was significantly (P> 0,95) higher (20-30%) than in 1-week-old ones. In the cracks of both types in both years, the egg laying by the 1st generation was completed by the end of I decade of July.
In 2006, the intensity of egg laying by the 1st generation was 2-4 times higher than in 2007, due to weather peculiarities. In 2006, the temperature regime in June  (20,5  °C) exceeded the average annual rate at 4,0 °C, while the amount of precipitation was close to normal; in 2007, the temperature in June (15,0 ° C) was at 2,0 °C below normal at the precipitation exceeding the norm. For the same reason, the maximum of egg laying was observed 7-10 days later. The egg laying by the 2nd generation in both years occurred from the II decade of July until the III decade of August (maximum - during the I decade of August) with less intensity than in the 1st generation (in both years  - 3-4 times less intense).
In 2006, the 3rd RCM generation started egg laying in the end of II decade of August, in 2007 - 10 days later. In 2006, the egg-laying was finished by the end of III decade of September, in 2007,  pest eggs were sporadically detected in all cracks till the beginning of II decade of September. The cracks aged 2 and 1 weeks were equally attractive to females of the 1st and 2nd generations, but the 3rd generation laid more eggs in 2-week-old cracks, at the more prolonged period of eggs accumulation and their slow development (delayed due to cold weather).
Larvae. The 1st generation of larvae were found in cracks in both years of observations by the end of I decade of June (see Fig. 2, B). In the beginning of II decade of July, larvae completed their development and left cracks to pass pupation in soil. In 1-week-old cracks, the greatest number of larvae was observed in 2006 in early July (in 2007, a maximum was not detected due to a small population).
In 2-week-old cracks, the highest number of larvae population in 2006 (20,0-24,0 ind. per crack) was observed from June 22 to  July 11 (with a small break), while in 2007 the peak was detected in early July (3.4 ind. per crack). During the feeding period,  the  number  of the 2nd larvae generation in 2-week-old cracks averaged 3-4 times higher than in 1-week-old cracks.
The 2nd larvae generation of RCM were annually identified from the end of the II - the beginning of III decade of July until the beginning of the III decade of August. In 2006, the population peak of  2nd larvae generation in 2-week-old cracks was in August 1 (22,6 ind. per crack), while the 1-week-old cracks were settled 5-6 times more intense compared to the 1st generation, with a peak on August 8 (33,8 ind. per crack). In 1-week-old cracks, the larvae of younger ages were detected, because the average daily  temperature in the III decade of Jule (19 oC) and the precipitation (27 mm per decade) were close to normal.
A week later than the population peak in 1-week-old cracks (by August 15), the number of larvae found in 2-week-old cracks decreased in 3 times compared with that in the 1-week-old ones. Cold weather and the increased precipitation (4 times higher than normal) in the I decade of August contributed to early departure for pupation of older larvae and to the increased mortality - in younger ages. The development of 3rd RCM larvae generation was suppressed in 2006 under this stress.
In 2007, the population maximum of the 2nd  larvae generation was observed on August, 1 - respectively 6.6 and 4.7 ind. per crack in 2- and 1-week-old cracks; the number of the 3rd generation was very small (a peak - September 12, 0,8 ind. per crack).
The obtained results showed an equal or slightly greater attractiveness of 2-week-old cracks for larvae feeding and development. It is possible, that bark delamination along the periphery of inner part of a crack increasing when larvae feeding, and the raise of cane thickness have some importance. Larvae of older ages are capable to distribution in the primary bark layer under stem epidermis (especially near a petiole attachment to stem) few inches up or down from the place of oviposition. The pest larvae promote the expansion of tissue damage, whose smell attracts females, they also disturb plant to form periderm isolating the affected area, which provokes a traumatic infection of cracks by phytopathogenic fungi.
Thus, in the Novosibirsk region, it has been found that the raspberry cane midge Resseliella theobaldi (Barnes) (RCM) produces three generations. Development of the 1st generation depends on weather conditions in the III decade of May - June, the 3rd  - on September weather. In favorable years, the 1st larvae generation is the most harmful. Rainy, cool weather in June may suppress the development of the 1st larvae generation even at presence of suitable places for laying eggs (artificial or natural bark cracks). Under these conditions, the higher decrease has been observed for the activity of egg laying and number of larvae in cracks (perhaps owing to the increased mortality of eggs and larvae of younger ages) rather than imago emergence. The 2nd larvae generation usually develops in stable, favorable conditions of July-August; it restores the pest population and creates its reserve for next year. According to our data (2, 12), the harmfulness of this generation is 4-5 times less than the 1st one. However, cold weather and abnormally high precipitation in the I decade of August 2007 had violated larvae development and caused death in larvae of younger ages, which significantly reduced the pest population and has led to the suppression of the 3rd generation. In Western Siberia, the third generation of larvae is absent or incomplete, because only small part of the larvae have time to reach pupation (most larvae gradually die from early autumn frosts). The harmfulness of the 3rd larvae generation for corky and lignified raspberry stems is minimal. The active ingredient of pheromone traps revealed its high specificity: almost no male of other midge species were lured, and the catch of insects from other orders and families (imago of black-veined white butterflies, scorpionflies, wasps, parasitoid wasps) was quite random. Using pheromone traps, in contrast to water traps, has allowed the 1 week earlier reveal of flying RCM imago. Laying eggs by the pest is entirely connected with presence on canes of suitable damaged bark areas.
These facts suggest the prospects for combined use of results obtained by pheromonitoring, the information about timing and extent of natural bark cracking in different raspberry varieties, and the data on laying eggs and larvae hatching in artificial cracks on model shoots.

 

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Novosibirsk State Agrarian University,
Novosibirsk 630039, Russia
e-mail: tshpatova@ngs.ru; shternshis@mail.ru

Received June 30, 2008

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