Plant scouting

[Nathan gomori]

Number one

This is the practical examination of a field for the purpose of identifying pests, checking pest levels of infestation, diseases and presence of predators.

It is actually a cost reduction technique as it establishes economic threshold of any pest before coming in with chemicals in the field.

Number two
Importance of scouting

• To identify the type of pest and determine the pest population within the field and decide on the chemical to apply.

• Establishes pest economic threshold level for decision making.

• To determine the level of weed infestation.

• To determine the level of disease infestation.

• Helps to assess the effectiveness of the previous spray.

• It is a sure way of saving money since you don’t spray when it’s not necessary.

• Identifies friends( beneficial insects) in the field e.g. spiders, lacewings, syphids, phonoctonus etc.

Number three

Points to consider when scouting

• Scout 24 plants per field which should be no greater than 20 hectares

• If field is bigger than 20 hectares, divide it into two or more fields.

• Discard 5-10m from edges depending on size of field.

• If parts of the field grow differently, scout separately.

• Do not scout the same plants every week and choose only average sized plants. Timing of scouting

• Scout early morning before 10:00am, before flying pests have flown away.

Number four

Diagonal (The X method)

Plants are chosen along the lines to have 24 plants scouted on 20 hectares or less.

This method is rigid in that almost the same plants may be scouted throughout.

The perfumes, soaps, lotions used by the scouters, may cause the pests to run away and this will give biased results.

This method has been discarded for this reason.

Zig-zag

This is a better method since a Z shape is formed and one can start from a different position the following week.

This gives a fair assessment.

Number five
When one is scouting he/she should knom the common pest of that plant he/she is scouting.

He/she should know the kind of pest and its location on the plant.

Cotton
The introduction of Bt cotton has resulted in a significant reduction of insecticide use against helicoverpa. However, sucking insects may require careful management.

Major pests include helicoverpa, spider mites, mirids, aphids and whiteflies.

Minor pests include thrips, green vegetable bug, pale cotton stainer bug, cotton harlequin bug, soil insects (true and false wireworm), redshouldered leaf beetle, leafhoppers/jassids, and mealybug.

Lucerne
Potential pests of lucerne stands include helicoverpa (generally only an economic problem in seed-producing stands), aphids (spotted alfalfa, blue-green and pea), lucerne leafroller, whitefringed weevil, leafhoppers/jassids and cutworm.

Maize
The main pests of maize are helicoverpa and soil insects. Other pests are infrequent, although maize leafhoppers can transmit wallaby ear diesease.

Millets and panicums
While serious insect pests are not generally considered a problem, helicoverpa, cutworm, armyworm, locusts and shoot fly can occasionally reach damaging levels.

beans
Insect pests can attack mungbeans at any stage from seedling to harvest but the crop is most susceptible from budding onwards. Monitor crops once a week during vegetative growth as the first buds are borne below the top of the canopy.

Major pests include helicoverpa, pod-sucking bugs, mirids and bean pod-borer.

Minor pests include caterpillars (loopers, cluster caterpillar, Etiella), bean fly, cowpea aphid, thrips and cowpea bruchid (post-harvest).

Peanuts
Pest damage to peanuts can occur from planting to maturity. Under intensive production a number of pests will warrant control.

Major pests include helicoverpa, mites, Etiella and peanut scarab.

Minor pests include whitefringed weevil, false wireworm, leafhoppers/jassids, cluster caterpillar, mirids, silverleaf whitefly, thrips, armyworm and cutworm.

Sorghum
Sorghum is susceptible to insect pests from emergence to late grain fill. IPM programs incorporate latest varietal releases and soft biopesticides.

Major pests include Helicoverpa armigera and sorghum midge.

Minor pests include false wireworm, cutworm, black field earwig, armyworm, corn aphid, Rutherglen bug, sorghum head caterpillar and yellow peach moth.

Soybeans
Soybeans can be attacked by pests at any stage from seedlings to close to harvest, but are most attractive from flowering onwards.

Major pests include helicoverpa, pod-sucking bugs and silverleaf whitefly.

Minor pests include brown shield bug, caterpillars (cluster caterpillar, loopers, soybean moth, legume webspinner, Etiella), redshouldered leaf beetle, lucerne crownborer, soybean aphids and mirids.

Sunflowers
Sunflowers are attacked by a number of insect pests at various stages of crop development. Sunflowers are more susceptible to seedling damage from soil insects than other field crops because damaged seedlings lack the capacity to regrow or tiller.

Other pests include Rutherglen bug, helicoverpa, whiteflies, loopers and green vegetable bug.

Winter cereals (includes wheat, barley)
Insects are not normally a major problem in winter cereals but there will be times when they build up to an extent that control may be warranted.

Pests of winter cereals include cutworm, aphids, armyworm, helicoverpa and mites.

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