Seed treatments provide targeted control of insect pests. They offer protection at the establishment phase and can often delay or remove the need to apply foliar sprays. In some instances, using seed treatments rather than foliar sprays can preserve beneficial populations.
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).
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. 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. Although the duration of protection may be limited, a delay in crop damage and pest establishment can reduce crop losses.
When would you use seed treatments?
- Planting in conditions that make the seedlings more susceptible to insect damage e.g. dry or cold and wet conditions
- Sowing into fields where it is known that pests are present and are difficult to control or detect before crop damage occurs e.g. soil insects, earthmites
- Where crop losses cannot be tolerated e.g. seed is expensive or sown at a low rate per hectare.
Advantages of seed treatment
- Precision targeting. Very little insecticide is applied to non-target sites, or to non-target organisms e.g. 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.
Disadvantages of seed treatment
- Limited protection under high pest pressure. Under high pest pressure, significant crop damage may occur. Even through pests are killed when they feed on the treated seedling, each ‘attack’ causes damage and cumulatively this can still be significant enough to cause seedling loss.
- Duration of protection. Seed treatment may not provide protection for long enough to provide complete protection to the establishing crop. Pesticide breakdown is most rapid under warm, moist conditions.
- Limited shelf life of treated seed. Surplus treated seed cannot be sold for grain. This is a particularly serious limitation for seeds such as soybean, where seed germination and vigour decline relatively quickly..
- Phytotoxicity. Some seed treatments may be phytotoxic when applied at high rates. Cracked, sprouted, and scuffed seeds are particularly susceptible to toxic effects.