Biological pest control with mass-produced arthropod natural enemies is well developed in greenhouse crops and has often resulted in the evolution of complex ecosystems with persistent populations of multiple arthropod natural enemy species. However, there are cases where arthropod natural enemies are either not effective enough, not available, or their use is rather costly. For these reasons, biological control based on microorganisms, also referred to as ‘microbials’, represents a complementary strategy for further development. Although commercially available microbials have been around for quite some time, research on and the applied use of combinations of arthropod natural enemies and microbials have remained relatively under explored. Here, we review current uses of entomopathogenic fungi, bacteria and viruses, and their possible direct and indirect effects on arthropod natural enemies in European greenhouses. We discuss how microbials might be combined with arthropod natural enemies in the light of new methodologies and technologies such as conservation biological control, greenhouse climate management, and formulation and delivery. Furthermore, we explore the possibilities of using other microorganisms for biological control, such as endophytes, and the need to understand the effect of insect-associated microorganisms, or symbionts, on the success of biological control. Finally, we suggest future research directions to optimize the combined use of microbials and arthropod natural enemies in greenhouse production.

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Fungi belonging to Order Entomophthorales are considered the major pathogen of aphids in natural ecosystems and also in agroecosystems. They are known to cause large scale epizootics, but none of the species of this order have been developed as commercial biological control products. They could be one of the best candidates for controlling aphids in greenhouses because entomophthoran fungi require shorter periods of high humidity for transmission than fungi belonging to the order Hypocreales (Beauveria sp., Lecanicillium sp., Paecilomyces sp. etc), are more effective at low temperatures and are also more host specific. More than 30 fungi of entomophthoralean species have been recorded as aphid entomopathogens. However, a major stumbling block to utilising these fungi as biological control agents has been the difficulties encountered in growing them in vitro. Another approach in utilising these fungi could be to try inducing epizootics by introducing inoculum of infected aphids into the crop by using banker plants.

The thermal tolerance of four isolates of Beauveria bassiana and one isolate of Beauveria pseudobassiana was evaluated in vitro, by measuring the colonial diameters, on PDA medium, at temperatures between 5 and 35 ° C, during 14 days. The data obtained were used to calculate the growth rate of fungal colonies (mm / day), using linear regression. The representation of the values corresponding to the minimum, optimal and maximum temperature for vegetative growth was a curve described by a modified beta (ß) mathematical function. The minimum growth temperature of these isolates varied between 3.4 and 4.5 °C, the optimum temperature varied between 21.8 and 22.9 °C, except for one isolate of which optimal temperature was       26.8 °C, while the maximum temperature was varied for all isolates between 35.0 and 35.7 °C.

Fruit tree culture is of particular importance as food source, from socioeconomic and environmental point of view. The fruits of fruit-bearing trees and shrubs are one of the healthiest foods that are indispensable in making an optimal food ration for the human body. Through the cultivation of trees, the best use is made of hilly areas, inclined terrains in the lowland area, as well as sandy soils in Oltenia, NorthWestern Transylvania and Southern Moldavia. Fruit growing is the livelihood of a significant part of Romania's population. Orchards balance the composition of the atmosphere by CO 2 consumption and oxygen release, attenuate thermal extremes, increase air relative humidity, reduce wind speed. Moreover, orchards have an important anti-erosion role. As a result, the fruit growing development programs in our Country include priority measures and actions, among which the promotion of organic tree cultivation technologies. Directive 2009/128/EC of the European Parliament and of the Council of the European Union, establishes a framework to achieve a sustainable use of pesticides by reducing the effects of pesticide use on human health and the environment and promoting the use of integrated pest management (IPM-Integrated Pest Management) and of alternative approaches or techniques such as non-chemical alternatives to pesticides, all of which are part of the UN 2030 Agenda for Sustainable Development. Currently, low and ultra-low consumption technologies are being promoted when applying phytosanitary treatments. A way to reduce the consumption of a plant protection products is the punctual application of spraying, a component of the "precision agriculture" system. In the case of the punctual spraying application system, the command of sprayers opening or stopping is controlled, depending on the plant mass within the range of the machine. The purpose of the paper is to study technological solutions for punctual application of spraying in fruit plantations. Cuvinte cheie: plantaţii pomicole, tratamente fitosanitare, agricultură de precizie, normă variabilă