Effects of grapevine bunch exposure to sunlight on berry surface temperature and Lobesia botrana (Lepidoptera: Tortricidae) egg laying, hatching and larval settlement

Abstract

1 Bunch-zone leaf removal reduced infestation by Lobesia botrana, although the mechanism responsible for this effect is unknown. 2 Based on the mortality of eggs and newly-hatched larvae exposed to high temperatures (≥37 ∘ C) in the laboratory, the present study aimed to assess the influence of (i) bunch-zone leaf removal and grapevine-row orientation on berry surface temperature and (ii) bunch exposure to sunlight on egg and larval mortality. 3 Berry temperatures were measured using a noncontact infrared thermometer in two vineyards and showed that, in direct sunlight, the temperatures of berry surfaces were 9 ∘ C or more above air temperature, and the highest mean temperatures occurred on southwest-side bunches followed by west-and south-side bunches. 4 The results of four two-choice field assays, carried out confining fertile females in cages with two bunches, one exposed and one non-exposed to sunlight, showed that: (i) the females did not avoid laying eggs on sun-exposed bunches and (ii) the lowest percentages of both egg-hatching and larval settlement occurred on sun-exposed bunches. 5 The hypothesis that the high temperatures reached by sun-exposed berries cause egg and especially larval mortality is confirmed. 6 Bunch-zone leaf removal combined with optimized grapevine-row orientations can improve L. botrana control.

Side Effects of Sulfur Dust on the European Grapevine Moth Lobesia botrana and the Predatory Mite Kampimodromus aberrans in Vineyards

“…In the laboratory, sulfur dust reduced the preference of L. botrana larval settlement in line with the results obtained for T. absoluta [ 43 ], but in this earlier study the effect was stronger (around 90% compared to 55%). The deterrent effect of sulfur dust on the larvae, markedly observed in the laboratory, could also occur in the field and hinder the penetration of the berries by the newly hatched larvae, which, when remaining longer on the skin of the grapes, could be more exposed to the abiotic and biotic factors of mortality [ 21 ]. The prolonged wandering time of the newly hatched larvae could also increase the efficacy of insecticides active exclusively or predominantly before the larvae penetrate the berries (e.g., B. thuringiensis, indoxacarb), lengthening the period in which they can be in contact with or feed on the skin of the berries.…”

“…In the vineyard, a standard fungicide program was followed and a single application of acetamiprid (Epik, Sipcam, Milano, Italy) for the control of the leafhopper Scaphoideus titanus Ball (Hemiptera: Cicadellidae) was carried out on 20 June, i.e., almost two months before the beginning of the bioassays. Shoots holding two bunches of similar size and not in contact with each other were chosen [ 21 ]. Bunches were checked for the absence of L. botrana eggs before starting each bioassay.…”

“…Bacillus thuringiensis is rarely used due to its lower efficacy and persistence than those of synthetic insecticides [ 13 ]. Additionally, choice of cultivar [ 14 , 15 , 16 , 17 , 18 ] and cultural practices such as controlled nitrogen fertilization [ 19 ], bunch-zone leaf removal [ 20 , 21 ], and kaolin applications [ 22 ] can help reduce infestations and damage by L. botrana .…”

Efficacy of Conventional and Organic Insecticides against Scaphoideus titanus: Field and Semi-Field Trials

“…In accordance with these considerations, the higher residual efficacies obtained in the semi-field than in field conditions could be due not only to a better coverage by the insecticide solution, but also by the lower temperatures experienced due to the shading net. In fact, leaves exposed to sunlight can have a temperature even 5 degrees higher than shaded ones [ 55 ].…”

Influence of Grapevine Cultivar on the Second Generations of Lobesia botrana and Eupoecilia ambiguella

“…However, the maximum three-day difference in larval development time among cultivars reported in this last study does not seem sufficient to explain the differences in larval age composition observed in the field (data reported in [ 21 ] and in this study) because the interval between the two moultings is around a week. The differences in larval development time among cultivars could also be due to berry temperature, which is related to different amounts of sun exposure on bunches [ 20 , 36 , 37 ]. On the other hand, regarding the hypothesis that cultivar affects egg-laying periods, there is no evidence to suggest that females at the beginning of their oviposition period lay more eggs on berries of certain cultivars.…”