Evaluation of Indaziflam for Greenhouse Use

Due to the relatively small market, volatility concerns, and high crop-value-per-acre associated with ornamental crops, no preemergence (PRE) herbicides are currently labeled for use in greenhouses containing plants. The objective of this study was to evaluate indaziflam SC for potential use as a PRE herbicide on gravel in greenhouses containing sensitive crops grown in extreme environmental conditions. Mini-greenhouses (MG) were designed and constructed to fit within gravel ground beds as an initial component to this study in order to evaluate herbicide volatility. Species evaluated included ‘Better Boy’ tomato (Lycopersicon esculentum Mill.), ‘Extreme Orange’ impatiens (Impatiens walleriana Hook. f.) and two species of petunia (Petunia × hybrida Juss. ‘Dreams White’ and ‘Dreams Neon Rose’). Indaziflam SC was applied at the manufacturer's labeled rate [40 g ai·ha−1 (0.04 lbs ai·A−1)] (1×) and at twice the labeled rate [80 g ai·ha−1 (0.07 lbs ai·A−1)] (2×). Each rate was applied using one of three different methods: 1) applied to only the gravel in ground beds with plants placed on gravel and covered with MG immediately following application; 2) applied over the top of plants on gravel inside the ground beds and covered with MG immediately application; and 3) applied over the top of plants outside the ground beds on adjacent gravel and left outside of MG. Two nontreated control treatments were maintained for each species and were placed either on nontreated gravel inside ground beds and covered with MG or placed outside ground beds on adjacent nontreated gravel and not covered with MG. Little to no injury was observed on any of the species after being placed on treated gravel and covered with a MG regardless of indaziflam rate. However when indaziflam was applied over-the-top, impatiens and tomatoes exhibited severe injury and death by 30 days after treatment (DAT). Additionally, fresh weights showed that all species receiving either over-the-top treatment were severely injured, while the plants placed on treated gravel inside the MG and both nontreated control treatments (both inside and outside of MG) exhibited no signs of injury or stunted growth. Results from this study indicate that while indaziflam may cause crop injury to ornamental species when applied over-the-top, it is likely that little to no injury will be observed as a result of volatility due to a gravel application in an enclosed structure.