Integrated Integrated Weed Management in Lentil (Lens culinaris Medik.)

In recent years global concern over the development of herbicide resistant (HR) weeds has lead to interest in integrated weed management (IWM) strategies. IWM seeks to relieve selection pressure for herbicide resistance by utilizing mechanical and cultural controls in addition to herbicides. The situation experienced by Saskatchewan lentil growers with large populations of group 2 herbicide resistant wild mustard provides an ideal model system to test our hypothesis that IWM strategies can provide robust weed management and maintain crop yields. The first study evaluated an IWM method targeting HR wild mustard in lentil. This study was conducted for 3 years between 2011 and 2013 at 2 locations at Saskatoon and Scott, Saskatchewan. It was a randomized two way factorial with weed control method and seeding rate as the main effects. Weed control treatments tested consisted of a control treated with a glyphosate burnoff, saflufenacil (Heat ™) herbicide, rotary hoeing, half rate metribuzin (Sencor ™) herbicide, a fully integrated treatment, and a full herbicide treatment. Three seeding rates representing 1, 2, and 4 times the recommended seeding rate were tested. The integrated treatment relied on increased seeding rate to reduce mustard biomass and produce yield, and at the highest seeding rate it was able to provide equivalent yield to the full herbicide system. The results of this study show that an integrated system utilizing an increased seeding rate can control resistant weeds and maintain yields to a similar level as a strategy that relies only on herbicides for weed control. The cultural practice of increasing crop seeding rate has been identified as having potential to provide non-chemical weed control and enhance the effects of herbicide application. The objective of the second study was to examine the interaction between increasing seeding rate and the dose response relationship of weeds to herbicide application. The experiment was a factorial design with four levels of lentil seeding rate and seven levels of fluthiacet-methyl herbicide application rate. The study was conducted at two locations near Saskatoon, Sk. in 2012 and 2013. Results of the experiment show that increasing lentil seeding rate decreased the total mustard biomass when herbicides were not applied or were applied at low rates. In addition increasing lentil seeding rate lowered the herbicide dose required to result in a 50% reduction in mustard biomass in 2012, though it had little effect in 2013. These results suggest that the practice of increasing seeding rate can work with herbicide application to reliably and effectively control weeds, even in situations where herbicides alone may not achieve good control.