RICERCA ITALIANA     

ARTHROPODS MECHANICAL DISTRIBUTION IN BIOLOGICAL CONTROL OF PROTECTED CULTIVATIONS

Università degli Studi di Bologna

Abstract

The target of the project is to develop mechanisation techniques that can be succesful applied on biological crops. Peculiar attention will be paid to the spreading methodologies for insects in greenhouse crops.
The schedule of these activities is the following:
- evaluation of previous experiences on this subject;
- development of two prototypes for the mechanical distribution of usefull entomophagouses;
- devices laboratory evaluation to define distribution's effects both concerning functional characteristics and living organisms behaviour after spreading
- comparison between mechanical and handmade spreading of living organisms in greenhouse crops and comparative economical evaluation of the two systems;
- adaptation of mechanical devices to different operative conditions;
- results circulation will be carried out throught articles, seminars and workshops. <<<

Principal Investigator

Gualtiero BARALDI Università degli Studi di BOLOGNA

Research Objectives

Main target of this research is the evaluation of the mechanization use in biological control of plants phytophagouses. This is carried out throught a device for living organism spreading and the analisys of biological control on entomophagous and crop.
More in detail this research will manage with:
- development of two prototypes for the mechanical distribution of organisms based on a simple use and working times reduction compared to manual distribution;
- evaluation of the operative charcterisctics of the device concerning distribution uniformity and metering regularity;
- adaptability of the prototype to different use conditions on the basis of crops conditions, spread entomophagous and used inert materials;
- check of living organism to mechanical spreading with concern to survival, mobility, fertility and longevity;
- assessment of mechanical functionality and entomophagouses behavior in areas under control of different Research Units;
-Economical evaluation of the prototype use in a farm
- results spreading to researchers and structures involved in the greenhouse cropping.
The funds requested by any Research Units are proportional to the needs of foreseen activity, on the basis of staff availability. <<<

First Results

Setting up and standardising of the trial methods.
Definition of the prototype project characteristics.Testing and choice of the methods for using the mechanical systems, effects of mechanical distribution on the quality of the released organisms.Effects of the mechanised release compared to the manual one on greenhouse crops, in terms of influence on the quality of the beneficial organisms distributed, efficacy of the biological control and work productivity.Adjustment of the prototype performances. Further evaluations on the mechanised release of arthropods in greenhouse crops.Presentation of the results obtained. Organisation of technical information for farmers, technicians and manufacturers with the aim of developing mechanisation in biological crop production. <<<

Timescale

24 months

National and international background

Biological pest control is increasing nowadays because it represents one of the main tools for reducing or avoiding the use of pesticides in crop protection. The advantages of adopting the biological method are in terms of higher environmental respect, safeguard of the agricultural workers and healthiness of the productions. For many pests it now seems to be the only approach for obviating the well-known aspects of resistance to chemicals (Ward et al., 1972; Perring et al., 1983).
In particular in all solanaceous crops the infestations due to the "two spotted spider mite "Tetranychus urticae are frequent, amplified by the particular environmental conditions and the occurring of resistance to the most effective acaricides, and they have become uncontrollable by traditional chemical active ingredients, or however their continuous use does not allow the respect of the emergency norms imposed by law. The same can be asserted for other pests, such as the whiteflies Trialeurodes vaporariorum Westwood and Bemisia tabaci, or for aphids and thrips. Also in this latter case, relatively to the more recent introduced thrip, Frankliniella occidentalis, serious cases of resistance have been observed. The scientific research, apart from verifying new active ingredients with different mechanisms of action able to escape to these phenomena and respect the present needs of safe methods alternatives to the traditional ones, has been already oriented for some time to the possibility of biocontrolling the crops; such biological methods are often effective as the traditional chemical ones and are able to offer the best toxicological and ecological guarantees.
The use of the phytoseiid P. persimilis represents the best alternative possibility to the chemical control of T. urticae. In different European Countries the use of the predator id known and has been applied on different cultivations (Hussey et al., 1965; Pralavorio and Almaguel Rojas, 1980; Vacante and Firullo, 1983; Pena Estevez, 1985). Also in the case of Orius laevigatus, active predator of F. occidentalis, many researchers obtained positive results against the thrips in different part of Europe: on sweet pepper in Great Britain (Chambers et al., 1993), in Liguria ( Tavella et al., 1991, 1994) and in Sicily (Vacante and Tropea Garzia, 1993a); on strawberry in France (Villevielle and Millot, 1991), in Portugal (Frascata and Mexia, 1995) and in Italy (Benuzzi and Tommasini, 1995).
Releasing living arthropods by inoculation or inundation methods is a crucial step in biological control strategies against pests and is currently applied mainly in greenhouse crops and, sometimes, in open field crops, as the maize, and in forests.
The large-scale commercial use of natural enemies started in 1968 with releases of P. persimilis to control spider mites. The releases are normally manual processes. Besides the economic aspects, the releases of arthropods affect the efficacy of a biocontrol strategy (Nicoli and Radeghieri, 2000). Special care is to be consider in the choice of the rate of release, that is affected by the species of beneficial and crop, and the uniformity of the distribution, affected by the size and characteristic of the crops.
Some researches concerning mechanical systems for distributing the beneficial organisms were carried out. Few studies on tools to mechanise distribution systems are found in the literature. Studies concerned mainly the mechanical release of phytoseiids on straberry in California (Giles et al., 1995), the mechanical release of Chrysoperla rufilabris larvae (Morisawa and Giles, 1995), the distribution of Trichogramma maidis parasitoid of C. rufulabris and Ephestia kuehniella eggs (Gardner and Giles, 1997) and the mechanical release of C. rufilabris eggs mixed to vermiculite (Gardner and Giles, 1996). Another application concerned the release of Trichogramma paratitoids by hover (Maini and Burgio, 2000).
In Italy a little of cases of mechanization of releases are available, including releases of T. maidis on corn, and a recent study on mechanical distribution of Phytoseiids in strawberry greenhouses (Pezzi et al. 2001). More in detail, this study maintains that mechanisation represents an efficient distribution method, permitting higher work capacity and better management compared to manual distribution. Certainly protected crops represent an ideal condition for biological control based on the use of species of natural enemies in adult life stage. In Europe pests in greenhouses are currently managed with natural organisms on 14000 hectares, compared with 200 hectares in 1970 (van Lenteren, 1995). The success of the control in these crops is primarily due to the quality of the natural enemies produced by commercial companies. Today Europe has 26 natural enemies producers, out of the 64 companies world-wide (van Lenteren et al., 1997).
In southern Italy the spider mite is the key pest on which to base all pest management strategies (Benuzzi et al., 1991). A critical phase in the management is determining the best timing for the inundatory releases and the rate of individuals per plant to provide effective control. Normally a higher rate of adults per plant is released, to obviate any inaccuracy. In Emilia-Romagna, effective control of spider mite on strawberry has been achieved releasing 5-6 predators/m2 at the beginning of the infestation, corresponding to around 1 phytoseiid per plant (Benuzzi et al., 1991).
The mechanical distribution of the mites is often difficult in the adjustment and control of the applied rates, also because the predators available commercially are mixed with moist vermiculite or shawdust, materials that help to preserve them in viable condition. When distributed, these inert materials have to be managed in such a way as to avoid mashing, because this would be lethal for the beneficial organisms and would prevent the proper adjustment of the mechanical devices.
Taking into account the biological control it has to be underlined that only the development of mechanical systems for supplemental releases of bio-control agents can increase the adoption of no-chemical strategies. In pest biological control the development of physical systems for application with operational characteristics similar to conventional pesticide sprayers can facilitate the quality of the control because of the simplicity, the controllability and the repeatability of the application.
These studies underline an interest for the rational management of crops and non crop plants which are important tools in the conservation biological control and in the modern sustainable agricultures. <<<