Summergrass is a term used to describe a range of annual subtropical annual weeds the seeds of which are endemic in soils in the top half of the North Island. They germinate as a function of light incidence at ground level once ground temperatures exceed about 16 -17C. Because of this they tend to cause most problems in spring or summer sown lawns in the first stage after sowing. Being subtropical plants they grow very rapidly in warm humid conditions. This group of plants includes crowfoot grass (Eleucine indica) summer grass (Digiteria sanguinalis) and smooth summer grass (Digiteria ischaemum). They are annual species and as such they will die and disappear from the sward in autumn when temperatures start to decrease. Quite often they can be mistaken for paspalum because the seed head is similar.
- Ryegrass Lawns: Apply ethofumasate (sold as Expo 500) prior to the anticipated time of germination of these species. This product achieves a high level of success if used as a pre-germination spray. It can also be applied directly onto freshly sown ryegrass seed to prevent these species germinating. Alternatively Pendamethalin can be used as a pre-germination spray. However, this is best used on mature swards over six (6) months of age. This product contains harsh solvents that tend burn ryegrass plants so it is best applied during or just prior to impending rain. Control can also be achieved by applying the active ingredient fenoxaprop-P-ethyl (sold as PUMA S) if you hold an Approved Handler's certificate. Fine Fescue lawns: Apply Haloxyfop-P-Methyl (sold as Ignite or Gallant) at 60% of label rates when these species are actively growing. Couch & seashore paspalum; Apply flazasulfuron (Katana) at label rates. Kikuyu; Apply Atrazine as a pre-germination application