Bayer: The control of mealybugs on grapes

by | Nov 2, 2020 | Article

Safeguarding your grape crops to ensure a healthy, robust harvest and optimum yield performance this season asks for quality crop protection products. Investing in these products must therefore become an integral part of ensuring the sustainability and profitability of your farming practice.

One of the biggest challenges grape farmers face is the threats posed by mealybug infestations. High infestation levels of the vine mealybug can lead to losses in yield, decreased grape quality or even vine death. Mealybug belongs to the insect family Pseudococcidae, part of the superfamily Coccoidea, which also includes armoured scales, soft scales, and cottony cushion scale. These insects are commonly known as mealybugs because they typically secrete a white, powdery, or mealy wax that covers the body. All mealybugs feed on plants using their piercing-sucking mouthparts. They feed on most parts of the vines including the grape, leaves, trunk and roots.

Adult females are wingless and similar in shape to nymphs while adult male mealybugs are rarely seen and are tiny two-winged-insects with two long tail filaments. Mealybug is a vector for a range of plant viruses, the most commercially important being grapevine leaf roll disease which causes delayed bud break, flowering, and maturation of the berries. This is often noticed by the early red colouring of leaves. As a result of infection by the leaf roll virus, inefficient photosynthesis occurs, which results in delayed ripening and low sugar content. Infected vines also have a shorter life span which has a considerable economic impact to the grower.

This is a circulative virus and all life stages are capable of transmitting the virus upon feeding, with the first instar and crawlers showing the highest levels of transmission. The number of generations found is highly dependent on climatic conditions. Due to warm temperatures in the South African grape-producing areas, up to six generations of mealybug can be recorded in a year. The optimum temperature for the development of P. ficus ranges from 23 °C to 27 °C with the upper and lower threshold for the development between 35.6 °C and 16.5 °C.

It is key to monitor the presence of mealybug in your vineyards to ensure that the correct crop protection methods can be implemented. The release of honeydew is commonly associated with mealybug infestation in vineyards. There are two ways in which these pests are monitored, namely through visual monitoring and through a pheromone-based trap. Visual scouting can be very effective, but infestations occur in spots in a block which could lead to an incorrect assessment. A pheromone-based trap involves a trap containing a pheromone lure that’s hung out to attract the male mealybug. This is generally more effective than visual scouting; however, a combination of these two methods should be used for thorough, reliable monitoring of the mealybug.

The control of this pest can be difficult due to the fact that they tend to hide under the bark or in the dense foliage. Poor insecticide coverage and the spraying of chemicals that also kill their natural predators can lead to high infestation levels in vineyards.

Effective monitoring of mealybug infestation includes the correct timing and sufficient coverage of insecticides, natural enemy preservation by choosing insecticides safe for the natural enemies like Movento, ant control and alternative host control which includes effective weed control and good pruning practises.

The use of a programme with Confidor as a drench application prior to bud stage and Movento at inflorescence and pea berry stage provides very effective control of mealy bug.

Movento, a suspension concentrate systemic insecticide, shows excellent virus vector control and excellent control on the most important sucking insects. This insecticide shows no cross-resistance with other products and has a favourable environmental profile.

Together with Movento, Confidor, a systemic, water dispersible, granule insecticide is used to combat the spread of mealybugs.

For more information on the control of mealybug on your grapes, visit Bayer’s website or contact your nearest Bayer representative.

(Please note: When using Confidor, consult with your exporter due to the pending EU tolerance restrictions).

Contact Bayer (Pty) Ld. on 011 921 5002 | www.cropscience.bayer.co.za | www.bayer.co.za

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