From yield reduction to total yield loss – pests such as the Colorado potato beetle (Leptinotarsa decemlineata) and aphids (e.g. Myzus persicae), cicadas, thrips, nematodes and potato moths are endemic in almost all potato cultivating regions. The Colorado potato beetle and its larvae can eat continuously and are capable of laying waste to entire fields. In contrast, aphids do not cause direct damage, but rather as so-called vectors of viruses which they transfer. Producers of seed potatoes must be especially careful to prevent infection: seed potatoes that carry viruses cannot be certified for selling or sowing.
Safeguarding the harvest is essential but consider damage thresholds
The virus threat can be reduced by growing resistant varieties. Long-term rotations can also reduce the risk. But seasonal weather is beyond the farmer’s control – if it is favourable for the pests, they will be present in the field in large numbers. This is when it is essential to take steps to safeguard yield and quality. Damage thresholds are important considerations in deciding on exactly the right time to intervene: they indicate which level of infestation can be tolerated from an economic point of view. Damage thresholds vary from country to country – they also depend on how the potatoes are to be used after harvest.
Alternating active substance classes
Over the years, crop protection products – mainly from the organophosphate and pyrethroid classes of active substance – have been used successfully against pests. Now innovative products from the chloronicotinyl (CNI) are becoming increasingly predominant. Bayer products such as Calypso® and Biscaya (thiacloprid), Confidor® (imidacloprid) and Monceren® G (imidacloprid plus the fungicide pencycuron) belong to this class. Their major advantage compared with organophosphates: they are friendlier to both user and environment. Moreover, hardly any resistance to them has developed among the pest populations that confront potato crops. To provide overall protection during the early growth phases, Monceren G, with the systemic active substance imidacloprid, can be applied. However, if pests later reappear and go on to reach damage threshold levels Biscaya is available to the farmer as a novel, effective insecticide.
Biscaya and Proteus with an innovative formulation
Biscaya has a favourable profile with regard to beneficial insects and the environment. Moreover, it benefits from innovative technology, the so-called O-TEQ-formulation. Its main advantages: the spray solution is better retained by leaves; it is more evenly distributed over the leaf surface and, most importantly, the active substance is taken up more quickly by the plant. This is a particularly strong advantage when weather conditions are unfavourable. In general, Biscaya excels by virtue of its long-term efficacy.
Proteus is also formulated according to the O-TEQ technology. In contrast to Biscaya, Proteus has been developed to combine active substances from two classes (chloronicotinyl and pyrethroids). In regions without pyrethroid resistance, farmers thus achieve broad-spectrum control. The product is ideally suited for use in seed potatoes.
Avoiding resistance
The fewer active substance classes are available to control a pest, and the higher the number of treatments needed to achieve control, the greater the risk that resistance will develop. Resistant aphids are no longer a rarity in some European countries. The situation is similar for the Colorado beetle. “If the very same product is applied six to eight times in succession, then it is inevitable that even an extremely effective product will eventually lose its efficacy through resistance development”, notes Product Manager Julia van Bömmel. Farmers should keep the damage thresholds in mind, apply products at the recommended dose and alternate between chemical classes.
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