AR37 - Insects

Several insect pests attack ryegrass. These include Argentine stem weevil larvae, pasture mealybug, black beetle, porina, root aphid and grass grub.  All of these insects, except porina and grass grub, feed on ryegrass and not on clover. Porina and grass grub feed on all pasture species.

Argentine Stem Weevil	Argentine Stem Weevil Larva	Argentine Stem Weevil Eggs
Black Beetle	Black Beetle Larva	Grass Grub
Pasture Mealybug	Porina	Root Aphid

It is not uncommon for over 20% of endophyte-free ryegrass tillers to be damaged by Argentine stem weevil larvae in summer whereas both AR1 and AR37 will reduce this level to less than 5%.

Pasture mealybug can be a major problem in Canterbury and Hawkes Bay but is also found in the Marlborough and Nelson districts, Manawatu, Waikato and Northland. These insects suck plant sap from around the base of the plant causing plants to wilt and brown-off in autumn. Both AR1 and AR37 reduce populations of mealybug to very low levels (see paper).

AR37 is also very effective against black beetle, reducing damage to roots caused by the larvae in summer and early autumn (see paper).

It is also both deterrent and toxic to porina larvae in laboratory trials (see paper). In a field trial, no porina were found in plots of AR37 whereas endophyte-free and AR1 plots contained 10 larvae/m².

The root aphid is a tiny insect that sucks the plant sap from roots of grasses which is present all year. Because it has many generations in a year it can build up to high numbers when conditions suit it.  We think this aphid is responsible for reduced vigour of the ryegrass with AR1 and Standard endophyte. AR37 reduces populations of this aphid to very low levels.

AR37 has no effect on grass grub.

The increases in persistence and production of ryegrass from AR37 are largely due to the protection it provides against this broad range of insects. In an outdoor pot trial, the growth of ryegrass with different endophytes was compared when plants were treated or not treated with an insecticide. Insecticide treatment did not increase the growth of plants with AR37 but markedly increased the growth of endophyte-free ryegrass and of ryegrass infected with AR1 and the Standard endophyte (see graph below). In the field, protection against black beetle and the root aphid are thought to be the main reasons for the high yield of AR37 ryegrass in field trials in Hamilton and Kerikeri (see paper).

These graphs show how insecticide treatment of ryegrass with AR37 does not increase its growth, but insecticide increases the growth of endophyte-free ryegrass, and ryegrass infected with the AR1 and Standard endophytes.