Pasture seed dressings can provide valuable insurance to protect the significant investment of a new pasture. Seed treatment products include insecticides, fungicides and biological additives (in combination or singularly), designed to help maximise plant establishment.
The placement of pesticides in close proximity to the seed means seed treatment is cost-effective and environmentally friendly, as they provide targeted control of insect pests.
Seed treatments can protect the seed and seedling from low-moderate attack by insects during emergence and establishment. They work by forming a chemical barrier over the surface of the germinating seed, which protects it from chewing insects, such as wireworms (see Figure 1).
Systemic seed treatments result in insecticide being translocated to the above-ground parts of germinating plants, deterring or killing pests such as aphids and mites (see Figure 2). They offer protection post-sowing and can delay or remove the need to apply foliar sprays.
In some instances, using seed treatments rather than foliar sprays can preserve beneficial populations of insects. However, the benefits of seed treatments can be short-lived or the efficacy of seed treatments can be low if pest pressure is extremely high.
Seed treatments should be included in any resistance or insecticide management strategy (e.g. exposure of pests to particular insecticide groups, rotation of insecticide groups).
Although the duration of protection may be limited, a delay in pasture damage and pest establishment can boost plant survival and longer-term pasture productivity (see Figure 3).
When to use seed treatments
Planting in conditions that make the seedlings more susceptible to insect damage, for example dry or cold and wet conditions.
Sowing into paddocks where pests are known to be present and are difficult to control or detect before crop damage occurs e.g. soil insects, earthmites.
Where losses cannot be tolerated e.g. seed is expensive or sown at a low rate per hectare.
Most producers prefer the hassle-free option of buying pre-treated seed, as opposed to applying seed treatments themselves.
Store all pasture seed (even non-treated seed) in a dry, cool environment to minimise quality loss and impact on germination.
Species and the quality of the seed at purchase are the biggest drivers determining sowing rates and whether seed can be carried over from one season to another.
Some treated pasture species can be carried over from one season to another without too much impact on germination percentage, while other species will lose germination and or vigour if not sown in the year it is purchased. If in doubt, increase the sowing rate so there is no seed left over.
Always confirm the total germination of purchased seed from the seed company to determine sowing rates and potential to save leftover seed for the following season.
Always observe withholding periods specified on seed treatment labels. If buying seed be sure to know the number of weeks from sowing before a pasture can be grazed or cut for hay.
Precision targeting. Little insecticide is applied to non-target sites, or to non-target organisms, such as beneficial insects. Soil insects and insects that attack the seedlings as they are emerging can be controlled or deterred.
Low dose. Small amounts of pesticides are used in seed treatments compared to broadcast sprays. This reduces the environmental impact.
Reduce traffic over paddock. Control of early insect attack, such as redlegged earth mite (RLEM), through the use of seed treatments can reduce the need to apply insecticides by ground, saving costs and minimising potential off-target spray drift.
Limited protection under high pest pressure. Under high pest pressure, significant crop damage may occur. Duration of protection. Seed treatment may not provide protection for long enough to provide complete protection to the establishing pasture. Pesticide breakdown is most rapid under warm, moist conditions.
Phytotoxicity. Some seed treatments may be phytotoxic when applied at high rates. Cracked, sprouted, and scuffed seeds are particularly susceptible to toxic effects.
Contact: The Pasture Improvement Initiative (PII), website www.pastureimprovementinitiative.com.au.