Laeveld
Agrochem

Sap feeding pests in citrus

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Pest status and control measures

By Jan van Vuuren
Agronomic Solution Manager – Horticulture
Bayer

Each citrus-producing area in South Africa has its own complex of major and minor pests. There are more than 20 pests on citrus in South Africa (Bedford et al.), with most of them not of economic importance due to its sporadic appearance. However, some of the most destructive pests in citrus are from the orders Thysanoptera (picture 1) and Hemiptera (scale and mealybug) (picture 2).

Damage, by thrips, to young citrus trees is normally limited to foliage (picture 3) that may lead to stunted trees (delayed production). The major impact of thrips is when they feed on developing fruit during production which influences the marketability of the crop by scarring the fruit (picture 4). These fruits are then downgraded in export value. Thrip control form the basis of a pest control program on many citrus farms as even low infestation levels might lead to economic losses. This control is normally based on the use of agrochemicals with a good knockdown of the thrip population. However, the control strategy might lead to secondary pest outbreaks (scale and mealybug) as their natural enemies are also eliminated.

A high population density of California red scale (picture 5) may defoliate and eventually kill a tree due to the toxins that the feeding scale produce (picture 6). It may furthermore influence the marketability of the crop as pitting might occur with early damage on developing fruit.

Additional to the damage of mealybug to the fruit (picture 7), it could also lead to the rejection of the fruit because it is a phytosanitary pest.

Chemical control measures in citriculture in Southern Africa have gone through different phases over the past few decades from the use of mineral before-parathion era through the parathion and repercussions era up to the oils, pyrethroids, and IGRs era. More IPM compatible sprays for thrips were introduced and the citriculture has entered a new phase in promoting IPM.

The challenge, therefore, is to have compounds registered which provide an acceptable degree of pest control without disrupting the natural balance in the orchard. This necessitates an integrated approach with the least impact on beneficials in an orchard. The Bayer offer against sucking insects cover the key species (Table 1) that might occur at different plant growth stages.

The choice of product used in the spray program (Figure 1) should not have a negative impact on the environment as beneficial insects could play a major role in pest control. The Bayer offer (Confidor® 70 WG and Movento® 240 SC) enables the producer to tailor-make his program depending on the pest and growth stages for different production units.

Movento® 240 SC is active against immature insect pests (such as red scale, Aonidiella aurantii, and various citrus mites) feeding on treated plants by ingestion. The toxicological profile of Movento® 240 SC allows the product to be used in an IPM program without the possibility of repercussion pest development.

Effect of Movento® 240 SC on beneficials in Citrus

  • Chilocorus nigritus – Harmless
  • Coccidoxenoides peregrinus – Harmless
  • Trichogrammatoidea cryptophlebiae 
  • Harmless
  • Aphytis lingnanensis – Slightly harmful
  • Euseius citri – Harmless
  • Bees – No risk to honeybees at the maximum recommended rate.

The basis for an effective pest program:

  • Plan ahead – consider when pest will be present and ensure pesticides are available
  • Built a pest management plan for the individual crop, but take into account pest movement from adjacent fields
  • Make use of locally registered products according to window approach
  • Rotate chemicals with different mode of actions – involve area with the same plan of action to avoid resistance
  • Follow the manufactures recommendations
  • Avoid parallel or sequencing of host crop with the same pests.

Correct use of Agrochemicals in a program

Using a window approach:

  • Treatment window should not be longer than 30 days with a group of chemicals
  • Period between treatment windows should not be shorter than 35 days preferably 60 days
  • Never expose two consecutive generations to the same group of chemistry!
  • Implement IPM – plant early, rotate crops, etc.
  • Using insecticide mixtures but each product in the mixture must be effective on its own
  • Protect beneficial organism – choose products with the least impact on beneficial’s
  • Monitor during pre-plant period and if pest is present apply control strategy

Confidor® Reg. No. L7240 (Act No. 36 of 1947). Confidor® contains Imidacloprid (Harmful). Movento®
Reg. No. L8559 (Act No. 36 of 1947). Movento® contains Spirotetramat (Caution). Confidor® and Movento®
are registered trademarks of Bayer AG, Germany. Use strictly according to instructions on the label.
Bayer (Pty) Ltd. Reg. No. 1968/011192/07. 27 Wrench Road, Isando, 1601.
PO Box 143, Isando, 1600, Tel: +27 11 921 5002. www.cropscience.bayer.co.za www.bayer.co.za

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GROEI tydskrif

Seisoen 8

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