Forster, B.; Knizek, M.; Grodzki, W. (eds.) 1999: Methodology of Forest Insect and Disease Survey in Central Europe.
Proceedings ofthe Second Workshop ofthe IUFRO WP 7.03.10, April20-23, 1999, Sion-Chateauneuf, Switzerland.
Birrnensdorf, Swiss Federal Institute for Forest, Snow and Landscape Research (WSL) 136-143.
NEW CONTRIBUTIONS TO THE PROBLEM OF INTEGRATED CONTROL OF FOREST DEFOLIATORS IN ROMANIA
George Mihalache-ICAS-Bucharest; Constantin Ciornei-Forest Research Station Hemeius- Bacau-Romania, -Daniel Lupu-RNP-Bucharest
1. INTRODUCTION
In Romania, in silviculture the researches in the field of integrated control began in the period 1970 - 1975 when within the framework of a scientific program, were carried out some applicative researches to elaborate the first technologies of integrated control.
During the period 1996 - 1998 were carried out new researches in this field (Mihalache, Ciomei, Rang, Lupu) which had as principal purpose, elaboration of new complexes of integrated control of forest defoliators.
The researches were carried out in oak stands infested by two important species of forest defoliators -Lymantria dispar and Tortrix viridana.
2. MATERIALS AND METODS
In the program of the researches were included the practical experimentations in infested forests to apply three complexes of integrated control, depending on the species of defoliator and the level of the infestations.
2.1. Preventive complex of integrated cQntrol of gypsy moth
In the integrated control of gypsy moth (Lymantria dispar) were experimented two different complexes of integrated control, depending on the density of the pest populations (phase of outbreak). In the selection of the type of the complex of integrated control it had in view that in the incipient outbreaks (phases I - II), when the density of the pest population is very low and when there is no the danger of heavy defoliations, could be applied a preventive complex composed by nonchemical measures (table no. Thus within the framework of this complex were included the following measures:
- Mechanical measures of pest control by collecting the egg-masses in the forests with low densities (phases I-ll of outbreak).
It was appreciated that by using this method in the conditions of low infestations, it could be possible to diminish the density of the eggs with 30 - 50% (the most of the egg-masses of gypsy moth are laid at the basis of the trees).
- Biological control by the following measures:
-spray of the egg-masses with the viral suspensions (nuclear polyhedrosis virus- NPV) before hatching of the larvae;
- introduction of entomophagous insects (egg parasitoids and egg predators), collected from the forests with old outbreaks, where the degree of the parasitism is very high; these entomophagous species were transferred in the forests with incipient outbreaks, when the parasitism is very low.
- Silvotehnic measures by the followings:
As part of preventive complex of integrated control of gypsy moth the biological control with viral preparation constitutes the principal method. For this reason it is interesting to present some aspects concerning this virus.
2.1.1.The viral preparations
To be able to apply the preventive complex, was produced a new viral product on the basis of nuclear polyhedrosis virus (NPV). The name of this preparation is Inf-Ld and it was produced during 1997 - 1998 by two biotechnologies, elaborated in the laboratory of Plant Protection Institute at Bucharest (a group of the researchers coordinated by Dr. M. Ciuhrii).
The biological material consisted of infected larvae of gypsy moth collected from acacia forests and poplar forests where has appeared heavy natural epizootics produced by NPV.
The virused larvae were collected during of June 1996- 1998, from the basis of the trunks of the trees. The infected larvae on the last two instars get off from the crown of the trees and die on trunk.
2.1.2. Technique of the treatment with NPV
In the selection of the technique of the NPV treatment was took in consideration the capacity of the virus to transmit from a generation to another, the high level of the sensibility of the young larvae Gust after hatching), and the role of the entomophagous insects in the dissemination of the virus. Having in view these aspects was adopted a technique of spraying of the egg-masses before hatching, by alternate the treated bands with those nontreated (the breadth ofthe bands was 5- 10 m).
Depending on the density of the egg-masses were applied doses between 20- 30 g Inf-Ld I ha in water (50 - 60 1 water/ ha).
2.1.3. Method to establish the efficacy of the viral treatments
The observations carried out in the forests showed that after treatment of the egg-masses there are three periods of the mortality:
- the first period is during of 5 - 6 days after hatching of the eggs, when the larvae remain on the surface of the egg-masses; during this short period the larvae are very sensitive to NPV;
- the second period occurs after rising of the larvae in the crown of the trees, in the fust, second and third instars; during this period (11 - 15-th day after treatment) the dead larvae can be ftnd on the leaves and branches of the trees;
- the third period of mortality occurs during the last instars of the larvae (L5 - L6), when the infected caterpillars migrate from the crown to the basis of the trunks and die on the bark.
Thus the mortality of the larvae in the viral treatments must be established in those three different periods.
2.2. Repressive complex of integrated control of gypsy moth (table no. 2)
In the forests with heavy and very heavy infestations was experimentated a repressive complex composed by biological measures, chemical treatments and silvicultural measures.
Among the biological measures were applied bacterial preparations (Dipel 8L).This type of the treatments was applied in the forests where the predicted defoliations arrived at maximwn
100%.
In the forests where the predicted defoliation was more than 100% has been considered that is better to apply chemical treatments with biodegradable pesticides.
The analysis of the structure of the repressive complex of integrate control shows that at this complex were eliminated the mechanical measures (collecting of the egg-masses in very heavy infestations is not justified of economically point of view), the viral treatments with NPV (the high density of the egg-masses I trees in heavy infestations require the high doses of virus) and entomophagus insects.
2.3. Repressive complex of integrated control of Tortrix viridana and Geometridae (table no. 3)
The repressive complex against Tortrix viridana and Geometridae were tested in the forests of Quercus petraea from hill region. This complex was applied in the forests with mean and heavy infestations by using the biological and silvicultural measures.
Among the biological measures were tested the following three methods:
-bacterial preparations (Dipel 8L), by ULV treatments in Ll -lA instars (1,0- 1,5 kg /ha in 2,0 - 3,0 1 water);
-introduction ofthe nests of Formica rufa (in the hill regions there are the favorable climatic conditions for development of Formica sp.);
- introduction of artificial nests for birds (especially for the species of Parus )- the larvae of Tortricidae and Geometridae constitute the preferable food for insectivore birds.
Among the silvicultural measures were proposed especially the interdiction of grazing, cultures with flower plants and setting up mixed forests.
From integrated complex against Tortricidae and Geometridae were eliminated the chemical treatments, because it considerate that, the larvae of these species are very sensitive to the bacterial preparations and are preferred as food by Formica and birds.
3. RESULTS AND DISCUSSIONS
3.1. The results of integrated control by the preventive complex of gypsy moth By the collecting the egg-masses in the forests with low and very low infestations managed to decrease the density of the egg-masses with 33,3 - 76,7%. In this manner were created the ecological conditions in forests, to prolong the incipient phases of the outbreaks and to assure a great accwnulation of the entomophagous species. Regarding the efficacy of the viral preparation, was established that in all the forests treated with NPV it has been realized a high
efficacy obtained in the forests where we introduced the NPV preparation was produced not only by the viral preparation, but this effect is due to the natural· mortality too.
Among the natural factors of mortality can be noticed the parasitoids of young and old larvae, parasitoids of the pupae and especially the natural epizootics. It was very difficult to evaluate the contribution of each factor of mortality and this aspect must be elucidated in the future.
On the other hand, must be mentioned that it was demonstrated by our experimentations that the young larvae, after hatching are very sensitive to NPV and thus outlines a new perspective in biological control of gypsy moth.
3.2. The results of repressive complex of integrated control of gypsy moth
The principal measures of integrated control of this complex were the biological treatments with bacterial preparations and chemical control with biodegradable pesticides (Dimilin, Mimic, Rimon).
The results concerning the efficacy of the treatments with bacterial preparations demonstrate that in the forests treated with Dipel 8L registered a high level of the efficacy (98,5 - 100% ), and practically the outbreaks of the pest were liquidated. In the same time, in the treated forests the real defoliation was very low (3 - 15% ).
One interesting aspect is those that in our experimentations were used the low doses of Dipel 8L (1,2- 1,5 Dipel I ha). Is necessary to show that these doses can be recommended only for mean and heavy infestations (predicted defoliation until100 %).
Probably for very heavy infestations (more than 100 %), these doses cannot assure the preventing of heavy defoliations.
Other important aspect of the repressive complex is those concerning the efficacy of the chemical treatments with Dimilin. This pesticide proved to be very efficacy, because in all the forests the larval mortality was very high (83,0- 100 %); practically the outbreaks were liquidated and the real defoliation of the trees was nonsignificantly (5 - 20 % in most of the forests).
3.3. Some results of repressive complex of integrated control of Tortrix viridana Within the framework of repressive complex against the defoliator Tortrix viridana, were included only the biological and silvicultural measures. Among these measures, the principal importance were gave to bacterial treatments, which proved to be very efficacy against the larvae of Tortricidae and Geometridae. Very important proved to be at this defoliator biological measures, namely introduction of the nests of Formica rufa and artificial nests for the insectivore birds especially in the hill regions.
The results of these measures, show that the treatments with Dipel 8L with a dose of 1,3 1 I ha proved to be very efficacy (89- 97,4%).
The results obtained by introduction of the artificial nests show that this method stimulated the limitation activity of the insectivore birds. The new nests which were introduced in the forests were occupied by the birds in a percentage of about 30 - 69%. The most important in the destruction of the larvae of Tortricidae proved to be the species of Parus, Passer and Sturnus.
CONCLUSIONS
In the last years in Romania were carried out new researches in the problem of integrated control of forest defoliators.
Within the framework of a practical program were experimented three complexes of integrated control in the oak stands infested by forest defoliators (Lymantria dispar, Tortrix viridana, Geometridae).
The preventive complex of integrated control of gypsy moth included only the nonchemical measures. In this complex were introduced the mechanical measures (collecting the egg- masses in the forests with low infestations), biological measures (treatments with viral preparation on the egg-masses before hatching; entomophagous insects), and silvicultural measures.
The repressive complex of integrated control of gypsy moth included the biological measures by bacterial treatments, chemical measures by using the biodegradable pesticides (Dimilin, Mimic, Rimon) and silvicultural measures.
The repressive complex of integrated control of Tortricidae and Geometridae, included the biological treatments with bacterial preparations, introduction of the nests of Formica rufa, and artificial nests for birds and silvicultural measures.
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Table no.l
Preventive complex of integrated control of gypsy moth in the oak stands with incipient outbreaks (phases 1-11) - low and very low density of pest population
Type of the Characteristics of Type of the Measures of integrated control Economical and ecological complex of the outbreaks in the measures of proposed to by applied effects of the integrated control
integrated infested forests integrated
control control
Collecting the egg-masses from the -Decreasing of the density of the Mechanical trunks of the trees before hatching in egg-masses with 40-50%
measures the forests with low density of the pest -Prolongation of the incipient
population phases of outbreaks
Incipient outbreaks -Appearance of the chronically viral
(phases I-ll) with epizotics of the type NPV for a
Preventive complex low and very low Spray of the egg-masses before long period
of integrated control density of the egg- hatching (1-15 April) with suspension -High efficacy in the year of
masses (0,1 - 0,5 of viral preparation-Inf-Ld treatment
egg-masses I tree) Biological -Protection of entomophagous
control insects
Introduction of parasitoid and predator -Increasing ofthe degree of the insects in the forests with incipient parasitism
outbreaks
Silvicultural - Grazing in forests in prohibited. Stimulation of the development of measures - Culture with flower plants. entomophagous insects
- Establishment of mixed forests - - - · - - - -
...
.j:>.
N
Typeofthe complex of integrated
control
Repressive complex of
integrated control
Table no. 2
Repressive complex of integrated control of gypsy moth applied in the oak stands with old outbreaks (phase lll - eruption) - High and very high infestations
Characteristics of the Typeofthe Measures of integrated control proposed Economical and ecological effects of
outbreaks in the measures of to be applied integrated control
infested forests integrated control
Microbiological treatments with bacterial - High efficacy against the larval Biological preparations (Dipel8L) by aerial spray population.
control UL V installation - instars L 1- L3 - Preventing the heavy defoliation.
- Predicted defoliation = 50 - 100%. - Protection of entomophagous species Old outbreaks (phase
m
Treatments with biodegradable and - High efficacy against larvae.-eruption) with high and selective pesticides applied by aerial spray - Preventing heavy defoliation .
very high density of the ULV. - Partial protection of the
egg-masses (more than Chemical Pesticides: Dimilin SC 48; Mimic 480 LV; entomophagous species
1-2 egg-masses /tree) control Rim on
Predicted defoliation= 100-500%
Chemical treatments with pesticides of - High efficacy and very rapid action shock action, applied in the forests with (1-2 days after treatment).
excessive infestations. - Preventing heavy defoliation.
Predicted defoliations = more than 400 - - Very low protection of
500%. entomophagous insects
Karate - 0,8 UL V;
Sumi-Alpha 0,5 UL V
Silvicultural Grazing in treated forests is prohibited. Stimulating of the development of
I
...
w
Type of the complex of integrated
control
Repressive complex of
integrated control
Table no. 3
Repressive complex of integrated control of Tortrix viridana and Geometridae in the oak stands with mean and heavy infestations - hill regions
Characteristics of the Type of the Measures of integrated control proposed Economical and ecological effects of
outbreaks in the measures of to be applied integrated control
infested forests integrated control
Microbiological treatments with bacterial - High efficacy after treatment (97 - preparations (Dipel 8L) UL V treatments in 98%).
L 1- L4 instars - Preventing of defoliation.
-Doses= 1,0- 1,5 1/ha in 2,0- 3,0 1 water - Protection of entomophagous insects Old outbreaks (phase
m
Introduction of the nests of Formica rufa - Diminution of the density of pest-eruption) with mean Biological (1-2 nests/ha in the first year) population.
and heavy infestation. control - Assurance of the ecological
Predicted defoliation equilibrium a long time.
between 50 - 100%.
Introduction of artificial nests for the Destruction of the larvae and assurance insectivore birds (species of Parus) -3 - 4 of ecological equilibrium
nests I ha in the first year
Silvicultural - Grazing in treated forests is prohibited. Stimulating of the development of measures - Culture with flower plants. entomophagous insects, by assurance
- Mixed forests of supplementary food for tlie adults of parasitoids
I
