The national agricultural industry, especially the fruit sector, has focused its production on exports. In the period between January and September 2022, 2.9 million tons of fruit have been exported, equivalent to USD 5,991 million FOB (ODEPA, 2022). Among the main species marketed are cherries, table grapes, apples, blueberries and plums, which represent 83.1 % of the export value and are destined for some of the most demanding markets worldwide. In this context, the challenge for the agricultural export sector is to comply with the current concept of quality, which considers, in addition to the appearance and health of the fruit, optimal post-harvest, safety in terms of residues and environmental sustainability.
One of the problems inherent to fruit production is pests, and the use of chemically synthesized insecticides has been the most efficient tool in their management. However, there are increasingly more restrictions on their use in relation to permitted active ingredients, compliance with maximum residue limits and alternatives for an effective rotation of chemical groups. In this scenario, biorational products emerge as an effective alternative, with less impact on ecosystems and a lower pesticide load on the fruit.
Grandevo® WG is an innovative biorational product, compatible with conventional and organic programs, synthesized from the bacteria Chromobacterium subtsugae, strain PRAA4-1T, isolated from a soil sample collected from Canadian spruce (Tsuga canadensis) by the USDA-ARS. It contains 30 % of non-viable cells of the bacteria, plus associated compounds that are produced during its fermentation process, which have biocidal properties on some species of mites and insects. Its first authorization for use was obtained by the company Marrone Bio Innovation In 2012, the EPA granted the agency an exemption from the tolerance requirement for all food products when applied as an acaricide and insecticide under good agricultural practices. In the United States, Grandevo WG has been widely developed over the past decade and is currently used successfully in countries such as New Zealand, Mexico and Chile.
Among its attributes we can highlight that it is free of deficiencies and maximum residue limits in the main destination markets, while its re-entry period is only 4 hours; it has a low impact on pollinating insects such as Aphis mellifera (Figure 1) and Bombus spp., as well as a significant number of natural enemies such as Amblyseius californicus, Aphidius colemani, Aphidoletes apidimyza, Atheta coriaria, Cryptolaemus montrouzieri, Delphastus catalinae, Encarsia formosa and Orius insidiosus. Therefore, it is compatible with integrated management programs that incorporate some of these insects. beneficial.
Figure 1. Effect of Grandevo® WG on bee pollination in almond trees
in the USA
One of its most innovative features is its multiple modes of action, among which have been reported - and confirmed under the national reality -: repellency, digestive disturbance, reduction of trophic activity, decrease of embryogenesis and ovicidal activity. These characteristics make Grandevo WG an excellent tool in the rotation of assets for the management of resistance of different pests, without there being, to date, reports of resistance worldwide. Its greater effectiveness is seen in spotted wing drosophila and Californian thrips. However, their spectrum of action - as shown in Figure 2 - is quite broad.
Figure 2. Spectrum of action of Grandevo® WG on pests in Chile.
One of the most recent and relevant agricultural pests to arrive in our country has been the spotted wing drosophila (Drosophila suzukii). Its connotation as a pest is attributed to its ability to cause direct damage to healthy fruit by laying eggs and subsequent development of the larvae inside, exposing the fruit to secondary attack by pathogens and other insects.
Since its first official detections, this species has spread rapidly in Chile, having been reported to date from the Oasis of Pica (under evaluation), in the north, to the town of Chile Chico, in the south. It should be noted that it is officially considered an established pest only between the regions of Valparaíso and Los Lagos. While in other regions of the territory it is found as a present pest with restricted distribution or under evaluation. Only in the extreme regions of our country has its presence not yet been reported.
When implementing controls on this pest, we must take into consideration that it is a very prolific multivoltine species, which is why it has the ability to rapidly increase its populations under favorable conditions. In addition, its polyphagy allows it to develop in fruits of cultivated, wild and ornamental plants. According to Mello (2020), it has been reported in 216 species of plants, distributed in 39 botanical families. In this sense, and being a flying pest, it has the ability to move from the environment to our crops, with fruits with thin skin, with a high sugar content and moderate acidity, such as blueberries, blackberries, strawberries, raspberries and some stone fruits such as cherries, being particularly susceptible; the vine is also a host plant and its presence has been evident in the last season.
During the 2021-2022 season a study was conducted to determine the effectiveness of Grandevo® WG on Drosophila suzukii in cherry trees located in the town of Río Negro, Los Lagos region. Two applications were made, 7 days apart, for each treatment, with a coverage of 1,500 l ha-1. Prior to the establishment of the study, the level of damage in the sector was homogeneous, with an average of 25.6% of damaged fruit. After 7 and 14 days, Grandevo® WG reduced the level of damage to 8 and 6.4 TP3T respectively. The results obtained agree with other studies carried out at a national level on cherries, strawberries and table grapes. These studies support a period of effective protection of 5 days against the pest. On the other hand, the results obtained in Chile are consistent with recommendations from the University of Michigan, who establish 5 days of activity of Grandevo® WG on spotted wing drosophila in blueberries (Rufus and to the. 2015).
In light of the above and considering the current situation of national agriculture, the export of food to some of the most demanding markets globally and therefore their requirements and legislation in terms of food safety and sustainability; we must carry out integrated management to address the problem of pests in our crops. In this context, the incorporation of biorational products, such as Grandevo® WG, in control programs will allow us to: rationalize the use of chemical synthesis products, their impact on ecosystems and human health, while implementing effective pest controls, which consider resistance management, and allow us to reduce the level of residues present in the fruit.
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