Whether in perennial crops like walnuts or annuals like rice, the weed pressures facing growers are like a plane taking off every spring. The runway from which that plane points skyward — in this case, recent weather and environmental conditions — has everything to do with its velocity and ability to get a strong start toward its destination. Heading into the 2024 growing season, that runway’s been a smooth one, meaning weeds could be poised to exert a lot more pressure on growers this season, putting a premium on effective weed control strategies.  

There’s no one-size-fits-all remedy for easing that pressure and effectively disarming weeds from robbing perennial and annual crops of quality and yield potential. But with the right products, their timely applications and guidance from PCAs, there are steps growers can take to manage weeds so they don’t get in the way of optimal crop performance.  

Though the solutions vary by crop, weed history, environmental conditions and specific microclimate, there is an overarching theme that will likely propel a “bigger weed year” in 2024 compared to the last few years, according to Grow West Technical Service Manager Layne Wade. The moisture pendulum swung from too little to too much last year, and now that things are generally more stable on the water front moving into this spring, the recipe is right for increased weed pressure. 

“Last year was weird because we had so much water at times that we didn’t have a lot of weed germination. This year will be a bigger weed year because we don’t have that oversaturation,” Wade said. “It’s been slightly warmer too, versus cooler temperatures we had last year. And in annual crops under irrigation, we’re kind of laying the groundwork to generate our own weed issues.” 

Consider well-timed pre-emergence herbicides for annuals and perennials

Pre-emergence residual herbicides are part of the foundation of strong weed control programs in both perennial and annual crops. Knowing the right specific product to apply and when exactly to get it out into your fields, orchards or vineyards should be top of mind when making the right pre-emergence herbicide decisions, Wade said. Though growers may be thinking about ways to cut overall input costs this year, pre-emergence herbicides with strong residual control should not be one of those cuts given the season-long difference it can make in keeping weeds knocked down. 

“Pre-emergence herbicides are one major pressure-reliever. Pre-emergents are one of the things you should always think about adding to — not cutting from — your crop management strategy,” Wade said. “If you apply the right pre-emergent at the right time the first time, you will be good for months and maybe the whole season. If you don’t, you’ll have to attack weeds with contact applications throughout the year.” 

But pre-emergence residual herbicides are a lot more expensive than other herbicides, right? Though the product itself may cost a few more dollars out of the gate, pre-emergent cost savings start to add up quickly when you think about opportunity costs and the expenses associated with contact herbicide applications in season. 

“Contact products may be half the price of a pre-emergent, but you have to have labor to apply it. And if you apply it three times, you also have three times the labor expenses,” Wade said. “By minimizing or eliminating emergence and weed competition early on — in perennial or annual crops — you’re going to support your crop from day one.” 

What’s the right pre-emergence herbicide for your operation? Consider your crop mix, specific weed pressures, soil type, environmental conditions, available labor and overall crop protection budget in reaching the right decision.  

“You’ll put a pre-emergence application on at various times for perennial crops. Regardless of the crop, it must be something that fits with your operation. We are also seeing a trend toward more split applications,” Wade said, adding a pre-emergent can be applied anytime from early December to before planting as long as there’s the right amount of rainfall to incorporate the product into the soil for maximum efficacy.  

Rotate chemistries

There’s a lot to think about in applying the right herbicide, pre-emergence or otherwise. For perennials, the specific chemistry, target weeds and crop structures should all be considered in making the right choice. Your Grow West PCA is your best ally in diagnosing these key variables for perennial crops. 

“The chemical characteristics of an herbicide are critical to its overall use pattern, and PCAs know those characteristics well. In a perennial crop, you typically want the pre-emergent herbicide to stay in the upper 3 inches of the soil, with the longevity that matches the germination patterns of common weeds,” Wade said. “You don’t want it leaching down to the roots of the trees. That’s a function of the chemistry, its interaction with soil and water, and how it’s broken down. It also changes depending on the water source, location and architecture of an orchard because how much light hits the ground can change an herbicide’s longevity. Knowing these things with perennials is important.” 

Because of the frequency of herbicide applications in perennial crops in successive years, it can be easy to overuse one specific product, mode of action or active ingredient. The same is also true in annual crops like rice because the presence of water limits the number of effective herbicides. Still, it is important to rotate products with different active ingredients to help maximize both short-term weed control and long-term efficacy. 

“A large part of managing a rice crop is dealing with weeds. In rice, weeds are always a threat because of the flooded conditions that often encourage germination, and it may take three or four sprays to control them. That can enable weeds to select for resistance if the same chemistries are applied too much,” Wade said. “I’ve seen some rice fields that have been abandoned because of weed pressures. You can avoid that by applying various combinations around seeding with the intention of getting longevity of control.” 

It will be especially important to pay close attention to both short-term efficacy and the residual endurance of every herbicide this year given recent lessons learned, according to JJH Solutions LLC PCA, plant physiology Ph.D. and California Weed Science Society (CWSS) Director Josie Hugie. Though the supply chain situation isn’t as dire as it has been in recent years, the right herbicide decisions should consider product availability and resistance management.    

“With active ingredients being burned out because of resistance in crops like rice, this is no time to ignore rotating chemistries appropriately. You have to manage programs so you don’t lose chemistry efficacy quickly,” Hugie said. “We need to keep the attention on control strategies instead of doing the same thing every year. When supplies were short a couple of years ago, everybody panicked about what they could buy and resistance management practices weren’t consistently a top priority. That can lead to dangerous practices when there are shortages and you don’t have many product options. We can’t let our guard down.”   

Engage your PCA to make the best weed control decisions

Wade expects weeds like marestail, Bermudagrass and Johnsongrass to be among the major species growers face in 2024. But that won’t be the case everywhere; he recommends accounting for past weed pressures in planning for any herbicide applications or cultural practices to keep them at bay this year, especially given 2024 is starting with near-ideal conditions for weed growth. Your PCA can help audit your past weed pressures and make effective treatment decisions that fit within your budget for this year’s crops.   

“Your PCA knows there’s not a general cure-all for weeds across the board. It’s site-specific. You need to have that expertise and understand how the weed history will impact inputs for that site,” Wade said. “You’re going to spend money on weed control, but your PCA can help be efficient with that spending so you’re applying what’s necessary and not being wasteful.” 

If you haven’t already, get in touch with your Grow West PCA to start laying the groundwork for your weed control strategy in 2024.