Effects of temperature and wetness duration on infection by coniella diplodiella, the fungus causing white rot of grape berries

Grapevine white rot, caused by Coniella diplodiella, can severely damage berries during ripening. The effects of temperature and wetness duration on the infection severity of C. diplodiella were investigated by artificially inoculating grape berries through via infection pathways (uninjured and injured berries, and through pedicels). The effect of temperature on incubation was also studied, as was that of inoculum dose. Injured berries were affected sooner than uninjured berries, even though 100% of the berries inoculated with C. diplodiella conidia became rotted whether injured or not; infection through pedicels was less severe. On injured berries, the disease increased as the inoculum dose increased. Irrespective of the infection pathway, 1 h of wetness was sufficient to cause infection at any temperature tested (10–35◦C); with the optimal temperature being 23.8◦C. The length of incubation was shorter for injured berries than for uninjured ones, and was shorter at 25–35◦C than at lower temperatures; the shortest incubation period was 14 h for injured berries at 30◦C. Mathematical equations were developed that fit the data, with R2 = 0.93 for infection through any infection pathway, and R2 = 0.98 for incubation on injured berries, which could be used to predict infection period and, therefore, to schedule fungicide applications

Fungi Associated with Foot Rots on Winter Wheat in Northwest Italy

In a 3\u2010year survey on bread and durum wheat grown in Northwest Italy, brown root rot was the most important disease of the basal part of culm. Year, wheat\u2010growing area, cultivar and their interactions significantly influenced brown root rot incidence. The most important fungal species isolated from lower stems with browning were Microdochium nivale, Drechslera sorokiniana, Fusarium avenaceum, F. graminearum, and F. culmoniliforme, and Pythium spp. were frequently isolated. F., crookwellense was also isolated. Sharp eyespot was a frequent disease; take\u2010all and eyespot occurred only occasionally. Copyright \ua9 1995, Wiley Blackwell. All rights reserve

Can Spore Sampler Data Be Used to Predict Plasmopara viticola Infection in Vineyards?

Grapevine downy mildew (DM) is caused by the dimorphic oomycete Plasmopara viticola, which incites epidemics through primary and secondary infection cycles that occur throughout the season. The secondary infection cycles are caused by the sporangia produced on DM lesions. The current research examined the relationship between numbers of airborne sporangia and DM development on grape leaves to determine whether spore sampler data can be useful to predict the potential for secondary infections of P. viticola. Three years (2015\u20132017) of spore sampler data confirmed that sporangia are a common component of the airborne microflora in a DM-infested vineyard and that their numbers depend on weather conditions. For a total of 108 days, leaf samples were collected from the vineyard at 2- to 3-day intervals and incubated under optimal conditions for P. viticola infection. The numbers of airborne sporangia sampled on 1 to 7 days before leaf sampling were significantly correlated with the numbers of DM lesions on the leaves. The best correlation (r=0.59), however, was found for the numbers of viable airborne sporangia (SPV), which were assessed by using equations driven by the vapour pressure deficit. In Bayesian and ROC curve analyses, SPV was found to be a good predictor of P. viticola infection of grape leaves, with AUROC=0.821 and false positive predictions mainly occurring at low SPV. A binary logistic regression showed that a threshold of 2.52 viable sporangia m-3 air day-1 enables a prediction of no infection with a posterior probability of 0.870, which was higher than the prior probability of 0.574. Numbers of viable sporangia in the vineyard air is therefore a useful predictor of infection and especially of no infection. The predictor missed some observed infections, but these infections were not severe (they accounted for only 31 of 374 DM lesions)

Interactions among fungicides applied at different timings for the control of Botrytis bunch rot in grapevine

Botrytis bunch rot (BBR), caused by Botrytis cinerea, is one of the main diseases affecting grapevines. Due to the complexity of the B. cinerea life cycle and the existence of different infection pathways affecting grapevine tissues at both early and late growth stages, fungicides are usually applied sequentially at the end of flowering (A), prebunch closure (B), veraison (C), and before harvest (D). Interactions among fungicides (from different groups) applied at these growth stages were evaluated in this work, with focus on the strategies in which early- and late-season applications are combined (i.e., strategies AB, CD, ABC, ABD, ACD, BCD and ABCD). The evaluation was performed in a set of 116 studies carried out in different years and locations, by comparing the observed (b(obs)) and expected (b(pred)) efficacies in controlling BBR; b(obs) was calculated as the reduction of BBR severity in treated plots compared to untreated ones, while b(pred) was calculated by using a mathematical function. Early-season sprays (i.e., A and B) showed non-additive interactions (i.e., the observed efficacy was significantly lower than expected in case of additive effect) while late-season sprays (i.e., C and D) did. No significant synergistic effects were observed among fungicide sprays. In the early-season, spraying in A was more effective than in B, and both sprays (A and B) were useful under high disease pressure only, when the full ABCD strategy was needed for effective BBR control. Otherwise, the most effective combination was ACD, able to exploit the additive control of the early-season infection pathways and the multiple infection events during berry ripening

Reduction of botrytis cinerea colonization of and sporulation on bunch trash

Botrytis bunch rot (BBR) of grapevine, caused by Botrytis cinerea, is commonly managed by fungicide (FUN) sprays at flowering (A), at prebunch closure (B), at veraison (C), and before harvest. Applications at A, B, and C are recommended to reduce B. cinerea colonization of bunch trash and the production of conidia during berry ripening. The effects of these applications were previously evaluated as reductions in BBR severity at harvest rather than as reductions in bunch trash colonization and sporulation by B. cinerea. This study investigated the effects of FUNs (a commercial mixture of fludioxonil and cyprodonil), biological control agents (BCAs; Aureobasium pullulans and Trichoderma atroviride), and botanicals (BOTs; a commercial mixture of eugenol, geraniol, and thymol) applied at different timings (A, B, C, or ABC) compared with a nontreated control (NT) on B. cinerea bunch trash colonization and sporulation in vineyards. The ability of B. cinerea to colonize the bunch trash (as indicated by B. cinerea DNA content) and sporulate (as indicated by the number of conidia produced under optimal laboratory conditions) was highly variable, and this variability was higher between years (2015 to 2018) than among the three vineyards and three sampling times (i.e., 1 week after applications at A, B, and C). B. cinerea sporulation on bunch trash was significantly lower in plots treated with FUN than in NT in only 3 of 18 cases (3 vineyards 7 2 years 7 3 sampling times). FUN applications, however, significantly reduced B. cinerea colonization of bunch trash compared with NT; for colonization, BCA efficacy was similar to that of FUN, but BOT efficacy was variable. For all products, colonization reduction was the same with application at A versus ABC, meaning that the effect of an early season application lasted from flowering to 1 week after veraison. These results indicate that the early season control of B. cinerea is important to reduce the saprophytic colonization of bunch trash, especially when the risk of BBR is high