Foliar fungicide application has become more common in soybean production, especially in years with heavy white mould pressure. Liquid in-furrow fungicide application is also now being used in some US states. This additional fungicide is aimed to protect seedlings from diseases such as rhizoctonia.
Trials are underway in 2015 to assess the value of adding products such as Priaxor in-furrow at planting to soybeans. In 2014, we planted three trials with two varieties to assess the best application timing of Priaxor on soybeans, including an in-furrow treatment. In-furrow application of the fungicide was accomplished by using Keaton seed firmers attached to a Kearney planter in 15 inch rows. Foliar fungicides were also applied using a 40 foot Hardi sprayer at the various plant growth stages indicated in Table 1. KP Plus (0-51-33) was tank mixed and applied with the fungicide on the treatments indicated.
Results
Wet conditions were typical in most areas of Ontario in 2014 and persisted throughout the growing season. The temperature was slightly below average. These conditions were ideal for white mould development. White mould was found in both the St. Thomas and Perth sites, but was not observed in the Lucan location.
Figure 1 - White mould present at two of the three research sites.
Table 1. Average Soybean Yield Response to Fungicide Application, 2014 (all sites and varieties)
# Treatment & Growth Stage - Yield (bu/ac)
- Untreated Control - 49.1 de
- Priaxor In-furrow - 48.6 de
- Priaxor V6 - 47.8 e
- Priaxor R2 - 50.9 bc
- Priaxor R4 - 50.9 bc
- Priaxor R2 + KP Plus - 49.4 cde
- Priaxor R4 + KP Plus - 51.8 b
- In-furrow Priaxor + Priaxor R2 - 49.5 cd
- In-furrow Priaxor + Priaxor R2 + Acapela R4 - 54.3 a
In Table 1, reported yields denoted by the same letters are not statistically different. There was no statistical change in yield when the fungicide was applied solely in-furrow, or at the V6 growth stage. This indicates that applying foliar fungicides in-furrow or in combination with herbicides is not beneficial. A positive yield response of 1.8 bu/ac was observed when Priaxor was applied at the R2 or R4 soybean growth stage. There was no statistical yield advantage to adding the KP Plus foliar. These results concur with previous Ontario research that showed a 2 bu/ac average yield gain when applying one application of foliar fungicides.
The greatest yield response was observed with the most intensive treatment - in-furrow and foliar R2 applications of Priaxor, with an additional foliar application of Acapela at the R4 growth stage. The average yield increase observed across all sites and varieties for this treatment was 5.2 bu/ac. This was mainly due to white mould suppression and gives strong evidence that large yield gains can be achieved with the use of a foliar fungicide if white mould is present at moderate levels. The in-furrow portion of the treatment likely had little impact on the yield since that treatment by itself (Treatment #2) did not improve yield over the untreated check.
Source: OMAFRA