Weeds: sneaking up on you this summer

With showers and storms across the cotton growing valleys recently, it's important to monitor fields and fallows for summer weeds.

Trial results from Colin McMaster from NSW DPI provide some sobering facts around the benefits of summer weed control.

Colin found that summer weeds can remove valuable soil moisture down to 1.2m and deeper. And for every millimetre of moisture lost, mineral nitrogen is also depleted (for example, saving 75mm of moisture in the profile can provide 50kg of nitrogen/ha to the following winter crop).

It doesn't just make good agronomic sense. If you put a dollar figure on it: for every $1 spent on summer weed control you can expect up to $8/ha return in the following crop.

Summer weeds also act as hosts for pests and diseases in cotton crops. With an expected La Nina (waiting, waiting..) summer weed control will be important. We can expect to see increased germinations over the summer months if the predicted wet conditions eventuate. Selecting the right herbicide and adding a mix partner such as a group G can add extra punch, especially when chasing broadleaf weeds.

In this e-news, we outline what you can do to help stop summer weeds: 

Be on time: 

Timeliness is the key for all summer weed control. A few days can make a big difference to the condition of the target weed. Often growers have a narrow window of 5-7 days before the weeds are stressed and the efficacy of the herbicide is compromised.

Read more.

Consider your set up:

The correct set up of your boom - especially nozzle selection, boom height and travel speed - are key ways to reduce herbicide levels in the atmosphere. Most importantly, avoid potential inversion periods just prior to sunset and sunrise. There are resources available from CottonInfo, Cotton Australia and Nufarm to assist.

Read more.

Map your fields:

To reduce the risk of off target damage it is important to know what your neighbours are growing. SataCrop is up and running again this season. It provides imagery of farming regions overlain with sensitive winter and summer crops, eg: chickpeas, sorghum, cotton and viticulture. This provides a more comprehensive view of the crop types that are in the fields in all farming valleys. Crops are colour coded which helps to inform users about where sensitive crops are when planning spray programs. 

Read more.

Know your 2,4-D requirements:

A reminder for growers of the requirements for 2,4-D application and the risks posed to off target species. In an effort to combat the high incidence of off target damage from phenoxy herbicides, especially 2,4-D, the Australian Pesticides and Veterinary Medicines Authority (APVMA) conducted a review in 2018 and introduced new requirements for growers in 2019.

Read more.

Use double knock to control survivors: 

Having a good understanding of the herbicide resistance status of summer weeds is important. It's no-good throwing herbicides at weeds if you already have resistant individuals in the population to that mode of action. Consider the WeedSmart summer BIG 6 as part of best practice. And always look for opportunities for a 'double knock' - controlling weeds with more than one tactic. The important thing is that all survivors are controlled. This is the cornerstone of the cotton industry’s Herbicide Resistance Management Strategy (HRMS): 2+2&0 survivors.

Read more.