TRICHOGRAMMA ENTOMOPHAGE IN INTEGRATED PLANT PROTECTION AS MEANS TO REDUCE PESTS’ POPULATION DENSITY ON ANNUAL CROPS

During the 2000 to 2017 years average biological efficacy after 4 and respectively 6 treatments with Trichogramma on annual crops such as cabbage, corn, tomatoes, peas, sugar beet and soybean varied in the first variant from 74% to 90.0% whereas in the second variant varied from 60% to 76%. Pests attack on agricultural crops researched varied from 2% to 10%, after Trichogramma launching. In the untreated field, the same index varied from 16% to 90%.

A very important role in integrated plant protection belongs to biological measure for plant protection. Conservation and activation of the natural mechanisms in harmful organisms density regulation must be based on pro found knowledge of all the factors and biocoenotic bounding. In general it is noticed a very notable trend in ambient protection in the activities that depend on environment.
The basic principle of the biological control is the biocenotic balance through which the population of a species (prey, host) is conditioned by other species (predators, parasites and pathogens). But this balance is swing ing, has dynamic character and can be disrupted by agro technical practices as well as of plant protection. Therefore it is necessary to create favorable conditions to entomophage organisms for their development.
Trichogramma species parasitize many species of pests and are used in biological plant protection. Considering [1]. data from year 2000, annually 45 million hectares are being treated with Trichogramma sp. in the world. Considering, Knutson, 2001 [2]. information, Trichogramma is the most used entomophage in the world, which was launched annually on approxi mate 32 million hectares on agricultural cultures and forests in 30 different countries.
A pest example against which Trichogramma is used is Helicoverpa armigera Hb, which brings harm to a vast gamma of cultures. Helicoverpa armigera Hb is a polyphagous species, attacking over 120 species of crops and wild, causing significant damage to nature. Annual harvest losses of vegetables, corn and other crops are 15-80%. Correct and appropriate time launching of Trichogramma spp. entomophage in combating (con trolling) these pests helps reduce the number of pest's density from 60 to 80% 1995 [3].
Pest Helicoverpa armigera Hübner (Lepidoptera: Noctuidae) control with Trichogramma evanescens Westwood (Hymenoptera: Trichogrammatidae) in cotton cultures (Malvaceae) in Turkey. Helicoverpa armigera H. has 5 gen erations per year. Trichogramma launching was done twice for each of the three generations of H. armigera in 2004 and 2005 years. For every release of Trichogramma in field, 120.000 parasitoids were used per hectare. Percen tage of parasitized eggs was -62.9% and 71.6%.The percentage of larvae of H. armigera was reduced to 76.8 % and 80.6 %, respectively [4].
The "Biotop" Company from Europe produces and sells the Trichogramma entomophage, which is used against Lepidoptera pests. Trichogramma is produced for farmers in biological protection against Ostrinia nubilalis (corn) and Tuta absoluta (tomatoes) and is used yearly on 100.000 hectares in France, Germany, Switzerland and Czech Republic, Frandon, 2012 [10]. About Trichogramma brassicae's use as parasite on pests eggs in Germany, which was reared in laboratory conditions and applied in field against Ostrinia nubilalis for corn and other cultures like apple, plum, grapes and some crops in greenhouses, on a total surface of 11,000 hectares, several papers were written by the author, Zimmermann, 2004 [11]. In Ukraine, in present time, biological methods are used on an overall area of about 1.2 million hectares, where 65 laboratories are functioning and where 35-40% inclusively of the reared material is Trichogramma, Fiodorenco et al., 2009 [9]. Use of the biological methods for agricultural cultures protection, inclu sively with Trichogramma in Latin America (Brazil, Colombia, Costa Rica, Cuba, Ecuador, Panama, Venezuela) emerged to a total area of about 9 million hectares in 2002 [5].
In the Republic of Moldova, as well as in other countries, specialists' goal is to minimize yield losses caused by illnesses and pests without influencing negatively the fauna in biocoenosis and to obtain ecologically pure yield.
Within the Institute of Genetics, Physiology and Plant Protection of the Republic of Moldova, in 1976 was created the "Trichogramma laboratory", under the initiative of the academician Popusoi Ion, directed by Dr. habilitat Grinberg Alexandru and succeeded by Dr. Lidia Gavrilita. The main goal of the laboratory is to research, analyze, elaborate data in rearing and application of the Trichogramma entomophage in pest's control.
In order to apply Trichogramma in plant protection, profound knowl edge in Ecology, Biology of entomophage and phytophagous organisms is required. There are several factors to be considered which influence the efficacy in field. Obtaining satisfactory results in the Trichogramma appli cation for pest's control leads to variables continuous analysis and results driven focuses knowing the role and place of entomophage for regulating pest's density.
Materials and methods. Researches were done in field and laboratory conditions during various institutional and state projects with the Innovation and Technological Transfer Agency. Implementation took place in various farms in the Republic of Moldova and on the Institute's agricultural ter ritory along the 2006-2010 years. Trichogramma has been collected from annual cultures (cabbage, tomatoes, maize, peas, sugar beet and soybean). Trichogramma evanescens was reared on different host eggs preliminarily irradiated and nonirradiated with gamma rays.
Collecting, identification, storage and accumulation of Trichogramma species were done according [6]. Rearing of the laboratory host -grain moth for Trichogramma production was done by Аbaschin et al., 1979, [7] author's methods. Mathematical data elaboration was done according to Меncer & Zimerman, 1986 [8].
Steps to obtaining maternal cultures of entomophage: 1. For the reason that the Trichogramma entomophage is applied several times at different stages of pest's maturity for agricultural production protection, it is neces sary to collect annually from the natural environment the entomophage for its geophone renewal, because from reared several generations in laboratory conditions, it is known that Trichogramma looses from its qualities; 2. The annual natural collecting is done from the same cultures to which it is going to be applied afterwards; 3. It follows: identification, rearing and mainte nance along the year of the species collected from nature; 4. Use of differ ent procedural methods for quality increase during rearing process of the Trichogramma entomophage before launching it in the field; 5. Biological indexes (quality) analysis before launching in field for protection of crops.
Steps and periods for entomophage field application: 1. To make ac curate assessment of pest density in field, records necessary to determine the specific pest for each species and crop, which depend largely on their bioecological peculiarities, must be taken. Field pest monitoring with pher omone traps; 2. Deciding the rules and terms of release of Trichogramma entomophage, which have to be taken depending on the pest density at dif ferent developmental stages (egg, larvae, pupae, adults), also must take into account the damaging Economic threshold for each pest and crop; 3. De termination of the biological efficacy in field, made after each launching of Trichogramma, based on the period of pest development (1-3 generations), to which 4-6 launches can be made with entomophage in different cultures; 4. During the launch of the Trichogramma a strict record of the "control" (no launches) takes place which gives knowledge about the natural density of the entomophage, which helps in tracking and taking decisions for further launches; 5. Entomophage releases in our experiments were performed in capsules, to be protected by various predators.
In the Republic of Moldova, it was organized and functioned until recently an integrated system for producing biological resources for biological plant protection. For some years now the system is stationary, currently working partly, only two biological laboratories (Cahul, Soroca) out of 14. Trichogramma spp. is one of the most important biological agents in plant protection. In the Republic of Moldova, the volume of utilization of Trichogramma in field constituted 80% to 85% of the agricultural territory (1984-1992 years). Nowadays, the volume of production decreased considerably, which covered only 30 to 663 thousands hectares.
From 1994 to 2002, in the Republic of Moldova, the biological agent Trichogramma has not been produced. Starting from 2002 the production process had been reinitiated. Protected crops areas with Trichogramma spp, in Moldova, during the 2002-2011 years constituted a total of 47.7 thousands hectares at different annual crops (cabbage, tomatoes, corn, peas, sugar beet and soybean), from 2002 to 2008 years, and ranged from 2-9 thousand hectares.
Trichogramma spp. entomophage is one of the most important biological agents in biological plant protection and in integrated plant protection, which rears easily in the laboratory conditions and accumulate fatly because of its short development period of a generation. Trichogramma entomophage is used at its initial development stage (eggs). One of the most significant problems in mass rearing of Trichogramma is its quality which decreases easily while rearing several generations consecutively on host laboratory eggs, respectively its field efficacy decreases. For this reason several researches were made for augmenting its efficacy. One of the procedures with high success is rearing Trichogramma on preliminarily gamma rays irradiated eggs. The results are presented in the following Table 1.
In the Research Institute for of Genetics, Physiology and Plant Protection of Repub. Moldova, to increase the quality and effectiveness of Trichogramma, different rearing methods were used on various hosts for plant protection. T. evanescens' prolificacy reared on Mamestra brassicae L. eggs treated with different factors, ranged from 33.1 to 60.4 eggs/female. In untreated host eggs the results were the following: 23.2 eggs/female. Reared on Ostrinia nubilalis' eggs, the results ranged from 21.3 to 26.6 eggs/female whereas in untreated host eggs -13.3 eggs/female. Reared on Ephestia kuhniella's eggs the results ranged from 24.8 to 50.8 eggs/ female, whereas in untreated eggs the results were -25.3 eggs/female.  Table 2.
For T.evanescens, T. pintoi (tomato, corn), biological indicators in the first variant varied as follows: female prolificacy -from 30.9 to 36.8 eggs/ female, individuals hatching from 88.3% to 94%, female number -56.7 to 60.0%, static criteria of quality -from 16.2 to 19.6. In the second variant these indices ranged as follows: Prolificacy of females -from 18.0 to 21.5 eggs/female, individuals hatching from 79.6% to 86.0%, female number -53.5 to 56.0%, static quality criteria -8.4 to 9.4.
During the development period of 2-3 generations of the annual re The role of entomophages' application as an element in integrated plant protection is the following: Economic effect: Cost reduction for plant protection by 3-4 times relative to chemical treatments. Ecological effect: Preservation of useful organisms in nature, minimizing the number of chemical treatments in integrated system, creating conditions to reduce environmental pollution and the production of organic farming.

CONCLUSIONS
1. During the 2006 to 2010 years, the average biological efficacy after 4 and respectively 6 treatments with Trichogramma, on annual crops such as cabbage, corn, tomatoes, peas, sugar beet and soybean, varied from 74% to 90% in the first variant, whereas in the second one from 60% to 81%. Pests attack on agricultural crops researched varied from 2% to 10% after Trichogramma launching. The same index varied from 16% to 90% in the untreated field.
2. During the development period of 2-3 pest's generations on annual crops (cabbage, tomatoes, corn, sugar beet, peas, soy, etc.), a very important role in reducing pest's density belongs to entomophage. For this reason the following steps have to be performed in crop protection: -In the adult stage, pheromone traps are mounted to monitor and capture in mass butterflies; -In the pest's egg stage, 5 to 6 Trichogramma releases must be applied, having the norm of 200.000 to 300.000 individuals per hectare; -In the larval stage of pests, other entomophage can be released -Bracon, Apanteles; -Treatments with biological compositions in pest control can be applied; -1-2 treatments with fungicides to be carried in combating diseases; -1-2 treatments with selective insecticides to be carried in combating the complex of pests (if necessary); -Mechanical and physical means, crop's rotation; -Preservation of useful organisms in nature; -Minimizing (or avoiding) the number of chemical treatments in integrated protection; -Creating conditions to reduce environmental pollution; -Getting organic ecological and qualitative products.