Written by Hanlie Geldenhuys, Marketing Lead at Syngenta
Cutworm control must start before the first larva hatches. With maize planting season fast approaching, growers need to do their planning now, especially if they want to apply the 35-day principle in time.
The damage that cutworms can do to a maize crop is one of a maize grower’s worst nightmares. In extreme cases seedlings can be destroyed to the extent that an entire field has to be replanted. The direct-cost implication is significant enough, but the real damage lies in the yield potential that is lost as a result. Early plantings have the best yield potential and the four or more weeks that are wasted when a field has to be replanted, create a backlog that is not easily overcome.
Cutworms are a seasonal phenomenon and their lifecycle dovetails with maize planting that traditionally starts in October, after the first rains have fallen. In some seasons cutworm pressure is worse than in others, and it also differs from area to area. What remains constant, however, are the practices used to control cutworm.
Preventative action is the only way to keep cutworm populations in check. The best place to start is with an analysis of previous seasons. Understand the factors in your own fields and in the surrounding environment that influenced the cutworm pressure and repeat your successes, learn from your mistakes and try something new where necessary. To really come to grips with your cutworm situation, it is important to keep records of factors such as cultivation practices, cutworm pressure in the previous season, presence of winter crops or weeds in uncultivated or fallow fields, climate conditions such as temperature and the absence of moisture, seed treatments and the new season’s plantings.
The second element of prevention is winter cultivation. Conservation cultivation practices that use cover crops and crop residues to conserve soil moisture and improve soil quality, can unfortunately aggravate a cutworm problem, especially when population pressure was high in the previous season. Mature larvae present in the field at the end of the maize season use this plant material to survive underground during winter, meaning that you already have a cutworm problem before the first maize seed is planted.
Effective weed control, also known as burndown, at least 35 days before planting, will keep the cutworm population low while the seedlings develop. In clean fields with well-prepared seedbeds larvae have nowhere to hide, thus improving the odds of them coming into direct contact with chemical control products. Winter cultivation in August or early September also damages the pupae and exposes them to predators like ants. It is important that winter cultivation is done across a wide area to prevent the ingress of moths from adjacent fields.
The third element is chemical control. Pyrethroids are one of the pillars of cutworm control – provided they are applied properly and timeously. Syngenta’s flagship synthetic pyrethroid, KARATE ZEON® 10 CS, is extremely effective when cutworm larvae are 1 cm or smaller in size and the top 3 cm of the soil is moist, and when the product comes into direct contact with the larvae.
The biggest mistake growers make is to neglect the 35-day principle and then try to get rid of worms that are already bigger than 1 cm with chemical applications. In most cases this results in super worms that are almost impossible to control.
An integrated pest-control strategy that includes all the above-mentioned elements remains the best way to keep cutworms in check. Growers must actively make management decisions with due consideration of all the relevant factors, and combine chemical crop protection with practices that safeguard natural predators and limit cutworms’ food sources. The latter primarily entails the removal of weeds and crop residues.
In this regard, there are reports of growers finding that in fields where cutworm was a problem in the previous season, it is possible to proactively lower population numbers with a burndown application of KARATE ZEON® 10 CS combined with an excellent herbicide like TOUCHDOWN FORTE®, given thate KARATE ZEON® 10 CS is stable in water with an acidic or neutral pH. Correct control measures and application practices also allow ants, spiders and beetles to naturally keep cutworm populations low.
When growers follow the right plan of attack, it is possible to effectively prevent cutworms from wreaking economically significant damage.
Photo by Kobus Beyers
Relevant Agribook pages include “Crop protection“.
