Devons-nous lutter contre les insectes en viticulture Agro-Synergique ?

Should we fight against insects in Agro-Synergic viticulture?

We are less subject to insect damage in viticulture in general and particularly in my Bordeaux region; Grape moth moths are our most aggressive enemies, not because they cause quantitative crop losses, but because they then facilitate, through the perforations of their larvae, the arrival of gray rot (Botrytis cinerea) which can seriously alter the quality of a harvest (from 5% of the attacked grains) at the time of harvest. The southern sectors are seeing new lepidoptera develop on clusters such as Cryptoblabes gnidiella, certainly in relation to climate change. From one site to another, from one year to another, the pressure of these insects can be very different. . We have noticed that plots close to busy roads or hamlets benefiting from urban lighting are much more affected because the light attracts these nocturnal insects. On the other hand, the proximity of hedges and forests which shelter their natural animal predators (birds and bats), the maintenance of a diversified plant cover which maintains a population of auxiliary insects, reduces their attacks. For grape moths, there are three main categories of beneficials: predators, parasitoids and pathogens. Among the first group, we find generalist insects such as lacewings, ants and predatory bugs (Nabidae, Miridae and Anthocoridae) but also more specific predators such as the hoverfly Xanthandrus comtus. Arachnids (spiders and opilions) also play a large role in regulating cluster worms. We must also not forget the predatory megafauna composed mainly of bats, lizards and certain birds (tits). The second group is made up of numerous parasitoids which attack the different stages of cluster worms: trichogramma for the eggs, other hymenoptera such as the Campoplex capitator ichneumon for the larvae as well as certain tachinid flies. Finally, many pathogens affect the development of these pests such as entomophthorales fungi. Agro-Synergy must absolutely ban the use of non-selective chemical or biological insecticides to maintain a balanced ecosystem. This principle and the diversity of ecosystem situations has naturally led us to favor biological control by sexual confusion (which prevents the detection of females by males and therefore the egg-laying causing grape worms). We have no longer used insecticides since 1985 with the use of another biological control technique based on the use of Bacillus thuringiensis (BT) bacteria, a microorganism specifically toxic to lepidopteran larvae attacking grapes. Mating disruption, although more costly, is more effective because it saves us from having to calculate precisely when to treat with BT (the larvae must be present at a relatively precise stage because there is no persistence of the protection). Isolated plots cannot be effectively protected by confusion; we are therefore seeking to bring together other winegrowers to create islands of vineyards as large as possible in order to be technically and economically efficient, otherwise we will continue to use the BT with trapping allowing us to follow the evolution of thefts and calculate the date of laying according to microclimatic conditions. Agro-Synergy is therefore also the sharing of resources and experiences with the federation of actions (concerted phytosanitary management on a local scale) in order to help each other against adversity thanks to the pooling of knowledge and human resources. and technical equipment (loans and exchange of materials and works) to increase the effectiveness of actions while reducing their costs. Banning all non-specific insecticides is absolutely essential. I remember the sequence of disastrous extremely broad-spectrum pesticide sprayings when we were trying to eradicate unwanted insects in the 1970s: all the insects were destroyed. As nature abhors a vacuum, the violent disappearance of insects systematically led to outbreaks of biting mites, red and yellow spiders (Panonychus ulmi, Eotetranychus carpini, as well as Tetranychus urticae) which were no longer consumed by insects and which had in turn to be eradicated by monstrous acaricides...The local birds could no longer find food and disappeared in their turn. An infernal and fatal circle! Without denying a certain harmful influence of pesticides on the natural enemies of parasites, the various works of CHABOUSSOU showed that these proliferations also resulted, or even mainly, from an increase in the biotic potential of animals fed on treated foliage (increased fertility , longevity, fertility, the number of females compared to males in Mites, etc.). Moreover, many pesticides cause mites to swarm, for example, despite their safety against natural enemies. Furthermore, organochlorine products used in soil treatment multiply mites on potatoes grown on the soil thus “disinfected”. As for the resurgence of old diseases or the development of new ones (viruses in particular, wood diseases, etc.), they cannot be explained by the possible destruction of antagonists by pesticides, the latter being very rare or non-existent. Also, and without really demonstrating it, we speak, in these cases, of “resistance” to the pesticide in question. However, just as for animals, it is, more likely, a multiplication of nutritional origin also caused by the harmful impact on the plant of the fungicide, herbicide, or insecticide, used in repeated treatments. Gradually, resistant strains of parasites also develop. The situation remains complicated today when the wine grower is forced to carry out preventive and obligatory spraying in order to destroy vectors of diseases such as flavescence ore (vine degeneration disease caused by a phytoplasma) which is carried by other insects. Biters: the leafhopper Scaphoideus titanus. Whether the insecticide is chemical or biological (Spinosad™ extracted from Pseudomonas bacteria or Pyrethrums extracted from Pelargonium), these products kill almost everyone in their path because 1 CHABOUSSOU F. (1967), Study of the repercussions of various orders caused by certain fungicides used in treatment of the Vine against Downy Mildew, Vines and Wines, n 160 and n 164, 22 p. CHABOUSSOU F., Moutous G. and Lafon R. (1968), Repercussions on powdery mildew of various products used in fungicide treatment against downy mildew of vines, Rev. Zool. Agric., pp CHABOUSSOU F. (1969), Research on the proliferation factors of phytophagous mites of the vine, following pesticide treatments of the foliage, Fac. Thesis. Sc, Paris, 238 p. CNRSAO DEEP IW registration they are not specific…! Binding ministerial and prefectural decrees and on-site controls prevent evasion. It is indeed essential to fight against the development of this infectious disease without any treatment apart from the fight against its vector, but it is also essential to confine this fight to the actually infected sectors and not to the entire region. We have set up an observation group (GDON Libournais) which travels through all the plots in order to detect symptomatic vines which are marked and then necessarily eliminated for several years. Thus, the following year only the areas presenting a risk need to be treated and not the others. Biodiversity is thus protected as much as possible. When it is necessary to treat, we prefer to use vegetable pyrethrum, less persistent than Spinosad™, sprayed at night because it disappears quickly under the ultraviolet radiation of the sun, and which therefore has a less lasting impact on the ambient ecosystem without producing any residue in the environment. wine. In 2022, we were in a zone without compulsory treatment. Other leafhoppers (Empoasca vitis) can sometimes also invade the foliage of the vine at the end of summer. These attacks are localized and always linked to a physiological imbalance; they can easily be stopped by spraying calcined kaolinite, an organic clay which disturbs these insects without killing them. Their proliferation is prevented, the risk of harmful damage is eliminated and natural predators (ladybugs, bedbugs and birds) do the rest; it remains to be interested in correcting the nutritional imbalance, the fundamental cause, if this disorder were to repeat itself.  From 2023 we will set up an observatory for the biodiversity of fauna and microfauna in the vineyard in order to measure the impact of phytosanitary practices. The establishment of an apiary can usefully serve as a bio-indicator of the quality of the nearby and more distant ecosystem because the bees move several kilometers around the site; the analysis of the honey produced will also make it possible to detect the presence of pesticide residues and thus objectively qualify the purity of the ecosystem.

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