Managing Lepidoptera Grubs In Late Summer & Autumn

Great attention gets paid to grub control at the start of spring with a view to all summer management through either a single or split application strategy. The targets getting the attention at this time are the African Black Beetle, Billbugs, or possibly Stem Weevil. However, very late summer and into autumn often gets overlooked and this is when a different pest can turn up in great number. They are commonly known as the autumn lawn armyworm so the hint is in the name as to when it may turn up.

Our strong focus on early to mid summer can sometimes leave us vulnerable to an attack from army worm. They can do significant damage in a short time and love a good turf surface to march through.

Biology essentials

Mature moths lay eggs in mid to late summer. Upon hatching the larvae eat through their egg masses, get to the ground and start looking for food sources to dine on. They feed solidly for 2-3 weeks before moving deeper into the soil to pupate allowing adult moths to be produced once again.

Picking the activity of army worm can be done by looking for the distinctive damage pattern. Armyworms will move across a surface, generating a discernable line like an advancing army front. Damage will often occur adjacent to structures where the egg masses were deposited (e.g. timber posts and buildings). Kikuyu has proven a very susceptible host but the armyworm is not overly fussy when it comes to its diet.

Tools to use and application essentials

The lepidoptera order of pests is the absolute strength of the newer generation diamide insecticides e.g. Acelepryn. It is hard to find anything quite as strong as this chemistry on these targets and with a fantastic toxicity profile that has this product being exempt from scheduling this is a clear preference for many.

The oxadiazine insecticide indoxacarb is a close second and a third option to consider are the synthetic pyrethroids such as Bifenthrin. Neonicitinoids however are not strong on this group and are far more suited to spring applications for coleoptera grubs such as black beetle. The difference in timing from the Coleoptera grubs which tend to reliably feature more pre-Christmas to the arrival of the army worm at the end of summer is quite significant. If spring applications were made in late September then we are 5-6 months down the track from that time. For that reason a split application strategy of Acelepryn whereby one application is made Sept/Oct, but then complemented by a further February application can be a good approach to covering both vulnerable points. If applying Acelepryn for army worm delay watering and mowing post application for 24 hours

If preferring to utilize a different chemistry for rotation or budget reasons then for many turf situations Indoxacarb is a perfect option to employ in late summer / autumn. Indoxacarb has an entirely different mode of action (MOA) to the diamides and is a proven performer on the lepidoptera grubs. Unfortunately the approved situations of use remain golf centric in regards to Lepidoptera grubs and at this time does not cover sportsfields. However, the pyrethroids e.g. Bifenthrin (Compel Pro) remain a very efficacious and cost effective option employing an entirely different MOA class and can be used with confidence on these targets.

How Nuturf can help you

We offer a full suite of options to suit budgets, preferences and application methodologies. For those preferring to use the diamides we offer Acelepryn in liquid and granular form. The granular form is increasing in use courtesy of its ease of application and the lack of need for spray equipment in public open space. The granular form received the same exemption from scheduling as the liquid so no specific PPE is prescribed for this either.