SCIENTIFC ARTICLE

DEVELOPMENT OF A PEST MANAGMENT SYSTEM FOR BACTROCERA OLEAE (CDPT TEPHRITIDAE) IN CRETE BY UTILIZING ECOLOGICAL CRITERIA.

E.N.Psyllakis and N.E.Psyllakis

Zymbrayos, 730-06 Kolymbari, Chania, Kreta, Greece.

ABSTRACT

This paper represents the methodology and some initial results, during the transitional period from conventional to ecological olive-oil production, in hilly and plain groves situated in East Kissamos, Kolimbari area in north-west Kreta. Special attention was given in improving ecological management of insect pests and pathogens, especially the Bactrocera oleae pest. Five thousand trees under drip irrigation, c.v. mainly Koroneiki, all belonging to a family estate, were used. For the population monitoring 20 Mc-Phail traps were hanged while, for the control of the pest Rotenone Derris bait spraying and a combination of pheromone, olfactory and colour Deltametrin trap were used.

The effectiveness of the biotechnical control proved sufficient to suppress Bactrocera oleae fruit fly population five times less, as an average, when compared with the integrated treated groves, leading to a High Quality production index, by preventing and selectively controlling Bactrocera oleae with the minimum exposure of the environment to biocides.

INTRODUCTION

Reduction or complete elimination of insecticide sprays for the olive fruit fly, is possible with a mass trapping system utilising sex pheromones and food attractants (G.E. Haniotakis and al) also adequate protection of the olive crop from Bactrocera olea is possible by mass trapping with a pest-specific trap under conditions (T.Broumas and al). Experiments for studying the bio-ecology of the olive fly were carried out in plains as well as in the highlands of Creta (S. Michelakis). The above integrated pest control programs were used in order to design and implement the ecological management of Bactrocera oleae pest during 1995 and 1996 in the Psyllakis olive groves, during transformation from conventional into biological ones.

MATERIALS AND METHODS

Experiments sites: The experimental area included 5.000 trees, of which 4.500 are situated in the Zymbragos area 280-550m high, divided in 15 hilly groves and 500 of them are divided in 2 plain groves, situated 200-250m high northern in the Nochia area, both areas in the Kolymbari region.

In the Zymbragos groves the majority of the trees are of the “Koroneiki” c.v and only one percent of the “Tsounati” c.v. The Nochia groves are consisted only  of  “Koroneiki” c.v. The majority of the trees are between 25 and 75 years old and the distances between them is around 7 meters. Approximately 20% of the trees are with 3 legs. Levelling of land within highland groves varies and is mostly more than 15%.The whole olive grove is under drip irrigation and has been divided in 5 replications, the first one belonging to the Nochia grove. For the year 1995 ecological pest management was done by the use of traps and Rotenone Derris bait spraying. Vioryl traps are like green envelope rectangles, covered with deltametrine at a concentration of 0,15%.Attractants:Traps were baited with one pheromone dispenser containing 0,080gr of pheromone and with one ammonia releasing dispenser-the whole green envelope- perforated, and containing 70 gr. ammonium bicarbonate salt, as well as with the specific green colour of the envelope paper. Trap installation: In the beginning of June 2800 Vioryl traps were installed and on the mid of June 200 of them were installed additionally in sites where population density was high. Traps were placed one in every other tree at a north orientation at an inside point of the canopy. From 6-9 September the above operation was repeated but traps were hanged at an east orientation. Also, ground bait sprays were done with Rotenone solution,10% active compound,2% protein hydrolysate  (Dakus Bait 100) and 2,5% of sugar.

Additionally there were done four (in Nochia) and five (in Zymbrayos) ground bait sprays in neighbouring olive trees with a solution of 2% proteine hydrolysate  (Dakus Bait 100) and 0,6% fenthion, in order to isolate the ecological groves.

A network of 20 McPhail-traps,17 for the four replications, in the 8 bigger irrigated ecological groves in Zymbragos were installed immediately after the Vioryl ones and 3 in the Nochia.

As control the rest of the olive groves in Zymbragos with 80.000 and in Nochia with 30.000 trees were used. In the first, 7 ground bait sprays (2% protein and 0,6% fenthion) were done by the Kolymbari union, but 6 in Nochia with 2 additional ones focused only in sites with high population density.

For the year 1996 ecological management of Bactrocera oleae pest changed in order to reduce or eliminate the Rotenone Derris bait spraying as well as isolating with preventive bait sprays.

In the same 5 replications during the first five days of June 3.000 Vioryl traps were installed in the ecological grove, additionally 1000 Vioryl traps without pheromone dispensers were used in order to isolate the ecological grove. The same procedures, as described for 1995,were done in the control area during 1996.To establish fruit infestation levels, fruit samples were picked at the end of each month from 10 olive trees from each replication,25 fruits were picked at the head height from each tree.

For monitoring pest population changes the Zymbragos control area has been divided into 2 subgroups: one with McPhail traps in a distance until 100m. from the eco-olive grove and the other with McPhail traps in a distance bigger than 100m.

Results and Discussion

A general characteristic of both subgroups is the high population density comparing with the eco-ones but this difference is quite smaller in the nearer traps.Figures1,2 and 3,4 shows population curves for Nochia and Zymbrayos respectively. For Nochia the F test has been proven to be significant during 1995 and 1996 at a p<0.01.For Zymbrayos mean separation by Duncan’s Multiple Range test at p<0.05 was: 

Rotenone Derris applications doesn't seem to have the desired effect comparing with the control on population density, throughout the olive growing period.

As it can be seen from the figures, fruit infestation is smaller in the control with respect to the ecological olive groves. The fruits of all replications of the eco-olive grove were plumper and more open to attack, due to the crop irrigation conditions. In Zymbragos, the low fruit infestation levels during August and September were also due to the arid conditions of the whole control area. In Nochia half of the control is under drip irrigation and with regard to its rather small fruit size had low fruit infestation levels due also to the additional sprays. For both summers (1995-1996) weather conditions were quite favourable for the development of the fruit fly population due to the absence of the usual high temperatures during  July and August (The mean max temperature for the decade 1971-1980 were 36/36/34/34/31 for the months June, July, August, September and October with a Sn-1 2.2/2.6/2.3/3/2.1 and a cv (%) 6.2/7.2/6.8/8.8 and 7)

During 1996 olives gained weight quicker so they were more quickly infested than 1995 which has been an on crop year, nevertheless due to the efforts in order to control the alternate bearing differences in yields between an on and off crop year are around 20%. The E.M.I.P. achieved the desired results in Q.P.I. (Quality production index) and E.E.B.( Effective Exposure to Biocides) because the produced eco-olive oil achieved a very low acidity from 0,3 to 0,5.Even if E.E.B. is very low, we do use a selective  pesticide in the traps in order to control Bactrocera-oleae.

References

Haniotakis G. E., M. Kozyrakis, K. Bonatsos. Area wide managment of olive fruit fly by feeding attractants and sex pheromones on toxic traps.P.549-560

S. E. Michelakis. Bio-ecological data of the olive fly(Dacus oleae (Gmel)) in Crete Greece.P.397-406.

T. Broumas, G. Haniotakis. Further studies on the control of the olive fruit fly by mass trapping.P.561-566.

Fruit flies: Proceedings of the second international symposium 16-21 September 1986, Colymbari, Crete, Greece.

F. Florelli. Deltametrin and environment. Proceedings of the second national entomological symposium Athens1989 P.160-171.

G. Stavroulakis, A. Nikolaydis, A. Kalaitzaki and S. Michelakis The use of Rotenone against olive fly (Bactrocera oleae Gmel) Third ENOF workshop:"Resourse use in organic Farming" Ancona 5-6 July,1997.

We also have the diagrams - if interested contact us.