Amenity managers and contractors should plan weed control operations carefully in catchy spring weather, warns Monsanto, manufacturer of the Roundup range of glyphosate herbicides.

Technical manager Manda Sansom explains, "Following a long, cold winter the spring of 2015 has seen pleasant warm spells in April and early May but with high diurnal temperature ranges and overnight frosts. Applying glyphosate too early can lead to reduced weed control."


Dandelion - 2 weeks

Ms Sansom points out that understanding how glyphosate works can prove very helpful in understanding how performance varies in different situations.

"Glyphosate works by leaf uptake and translocation to the growing points in both shoots and roots. Here it blocks the biochemical pathway producing amino acids - the building blocks for protein and causes a slow death by starvation.

"Plants need to be healthy and have sufficient leaf growth to absorb the Roundup. Perennial plants like thistles, nettles and dandelions were late to emerge from winter dormancy this year. Seed germination has been delayed due to cold soil temperatures. Spraying by the calendar can result in herbicide being applied before sufficient leaf area has emerged."

The variable weather can also slow the effects of herbicide applications.

"Even with good leaf coverage, low soil temperatures and high diurnal air temperature ranges resulting in slow plant growth mean visible symptoms can take up to four weeks rather than the expected 10-14 days. However, the end result will be the same."


Dandelion - 4 weeks

Monsanto say their latest development helps amenity professionals meet the challenge of catchy conditions.

Roundup ProVantage is more concentrated at 480g glyphosate per litre and the optimised blend of surfactants as well as the high loading makes it their most advanced amenity glyphosate.

The company says superior performance includes improved rainfastness and speed of uptake. Rainfast in one hour for annuals and four hours for perennials, Roundup ProVantage reduces the risk of run off from that unexpected shower and ensures the maximum amount of glyphosate reaches the roots for the optimum effectiveness.

Improved reliability in hot and dry or cool and dry conditions helps make the most of weather windows and benefits contractors at a busy time of year.

Purchasers also have the benefit of Monsanto's long experience in getting the best out of glyphosate.

"Operators should pay close attention to correct water volumes and proper sprayer calibration, choosing appropriate nozzles and avoiding drift for optimum efficacy. To maximise results in all conditions, follow the guidance for optimum weed control using Roundup products in amenity available on request at technical.helpline.uk@monsanto.com" says Manda Sansom.