Cotton Research Institute - Entomology Section

Entomology Office Block	Insectary Inside the Entomology Block

The Entomology section develops and disseminates appropriate techniques for the control of insect and mite pests of cotton which individually or combined can result in serious yield losses. Red and Heliothis bollworms can cause yield losses of up to 60 percent. Aphids, red spider mites and soil pests can cause yield losses of up to 25, 40 and 100 percent respectively. The Pink bollworm can cause the cessation of cotton production once it invades cotton-growing areas. The major pests covered in the entomology programme are soil pests (termites and false wireworm), early sucking pests (aphids and jassids), late sucking pests (red spider mites, whiteflies and stainers) and bollworms (heliothis, red, pink and spiny).

The section examines pest/predator thresholds and scouting methods in all new varieties, screens new insecticides for low human and environmental hazards, examines spray application methods and equipment, evaluates varieties for pest resistance, looks at integrated pest management and other cultural methods for the control of pests.

Achievements

Landmark achievements include:

1. a)Closed season for the control of pink bollworm
2. b)Acaricide rotation scheme to prevent build-up of red spider mite resistance, and
3. c)Pyrethroid window to prevent bollworm resistance.

The Closed Season

The closed season for controlling pink bollworm refers to the period between 1 August and 5 October for cotton farmers in S.E Lowveld or 15 August and 20 October for cotton farmers in the remainder of the country when no cotton plant should be alive. Cotton plants are destroyed in order to create a “dead period” or “closed season” so as to minimize pest build-up, particularly that of the pink bollworm. This closed season is governed by the Plant Pests and Diseases Act [Chapter 19:08] which stipulates that any farmer who fails to comply will face either a fine or imprisonment, or both.

The Acaricide Rotation Scheme

The acaricide rotation scheme that was developed to prevent the build-up of red spider mite resistance divides the country into 3 regions and prescribes the chemical to be used for controlling red spider mite per region for 2 successive cropping seasons.

Below is a table and the map of Zimbabwe showing the regions showing the acaricide rotation to be observed for seasons 2009/10 to 2014/15.

 Region

The Pyrethroid Window

Pyrethoids are broadspectrum chemicals that are used for controlling various cotton pests such as bollworms, strainers, jassids and leafeaters. The Pyrethroid Window was developed to prevent these pests developing resistance to these chemicals. It requires that the use of the Pyrethroids be confined to the periods shown in the table below.

 Region

Recent achievements include the use of seed dressing technology (Gaucho T 45 WS, Cruiser 35 FS) for the control of aphids, termites and false wireworm. As a result, farmers have improved plant stands resulting in high cotton production. The introduction of Mospilan 20 SP, an aphicide that requires two less sprays than Marshal 25 EC has also proved to be very cost effective against cotton aphids. Currently, acetamiprid is the most popular aphicide in Zimbabwe