About Aphid Infestations
Aphids can be found on the underside of new leaves and are small sucking insects. They come in different colours, such as white, grey, green, black, or brown, and are the most common garden and orchard pest in many regions. In Lusaka, they can be found on citrus trees, plants belonging to the hibiscus family, and various vegetable varieties. Still, they generally do not harm healthy plants. However, the drought stressed many plants, and they suffered substantial damage from aphid infestations. They are most abundant just after winter when the rains begin in summer and after using nitrogen-rich soil amendments such as manure. Nitrogen-rich fertilizers cause a surge in young shoots and leaf growth.
Effects Of Severe Aphid Infestations
Aphids spread viral diseases and cause severe damage to plants. Infected leaves develop a black layer due to sooty mold fungus attracted by aphids’ sticky sap (honeydew). Ants, in turn, protect aphids from natural predators while feeding on honeydew. Later, leaves may fold, and shoots may dry out, leading to stunted growth, low yields, and dead branches. Drought and pest infestations may also cause bolting and premature flowering in herbs and vegetables, altering their taste and texture. Stress coupled with pest pressure can kill young plants and be worsened by other pests like scale insects, mealy bugs, and leaf miners.
Managing Aphid Infestations
To manage aphids improve plant health and defences. Water plants regularly to reduce stress and mulch soil to retain moisture. Avoid excess nitrogen-rich soil fertilizers and chicken manure. For a few plants, spray under leaves with chilli oil water. If severe aphid infestation occurs, use neem-based organic pesticides or organic/non-organic pyrethrins.
Pyrethrins may be organic or non-organic formulations. The organic pyrethrins are derived from Chrysanthemum flowers. In contrast, the non-organic formulations are synthetic (created in the laboratory) versions of the same compound harnessed from the flowers. They act the same way and may require similar precautions.
Buying Appropriate Pesticides
Different manufacturers use various names for pyrethrins and neem-based pesticides. To get their available brands, ask your Agro-dealer for the mentioned compounds. Aphids discard their skins as they mature, leaving white shells on the leaves. These may appear as if the pesticides haven’t exterminated the pest, so check if the white insect shapes are moving or hollow.
Prevention is the key to saving most plants, so a preventative pest schedule should be included in the plant care regimen to avoid produce loss or plant death. Zambia is still experiencing drought or flooding in some locations, both unsuitable for plants, so that pest pressure may persist through 2024. Consult your agronomists or plant care experts to assist your plants through the year until we have more suitable plant-growing conditions.
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Different levels of aphid infestations. Curtesy of the clients who allowed us to use their pictures.
