Agronomist's notebook: Look out for this enemy of pawpaw plant

Saturday June 1 2019

Farmers learn the practice of pawpaw cultivation during a field day at the Kisii Agricultural Training College.

Farmers learn the practice of pawpaw cultivation during a field day at the Kisii Agricultural Training College. Pawpaw grows in well-drained fertile soils, and is susceptible to waterlogging. PHOTO | BENSON MOMANYI | NMG 

ANN MACHARIA
By ANN MACHARIA
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If you want to get into fruit farming and you are a rookie, one of the crops you can easily grow is pawpaw.

The fruit does well in warm climatic regions such as Machakos, the Coast and even the North Eastern part of the country.

Pawpaws grow in well-drained fertile soils, and they are susceptible to waterlogging. In most cases, the crop is propagated by direct seeding although one can also grow the seeds in a nursery and transplant them to the seedbed after two months.

Controlled pollination is critical for one to get quality seeds though you should buy certified ones for best results.

The ideal spacing for planting is 3m by 2m depending on the soil fertility and the variety. After planting, thinning is essential to retain one male plant as a pollinator in 30-100 female. However, improved varieties are capable of self-pollinating.

Pawpaw is easily intercropped with other crops such as young mangoes, coconuts, and citrus. During its early stages of growth, other crops such as capsicum, cabbages, and beans can also be intercropped.

Maturity indicators for pawpaw include yellow patches on the outer cover. When harvested early, the fruit tends to have abnormal taste and flavour.

Under good management practices, the crop can yield 40-70 fruits annually during the first 3-4 years of economic growth.

Commonly grown varieties in Kenya include Red lady F1. It can take about eight to nine months to mature and eventually produce nearly 40 fruits per tree for the fast-maturing varieties.

One of the pests that affect pawpaws is mealybugs. Attacked fruits, leaves, and stems appear to have whitish cotton masses. The heavy infestation causes leaves to yellow and gradually dry.

Mealybugs are soft-bodied wingless insects that feed by inserting their long stylets into the plants drawing the cell sap.

TOXIC SUBSTANCES

The pest produces honeydew, which makes the plants sticky and encourages the growth of sooty moulds, thus the plant is not able to make its food since the stomata on the leaves are covered. It’s a common pest in moist and warm climates.

The pest acts as a vector to plant diseases, especially the viral ones and sometimes injects toxic substances during feeding, which causes deformation such as dieback and stem weakening with short internodes.

The mealybug also affects other crops such as passion fruits, pineapples, citrus, and sugar cane, among others. The eggs are usually laid on the underside of the leaves.

As the nymphs feed, the waxy coating begins to form over their bodies, resulting to the yellowing and falling off of the leaves and stunted the growth of the plant.

The honeydew makes the plant prone to bacterial and fungal infections such as blights. The pest is easily dispersed by wind, ants, animals, birds, and during the routine management practices.

To avoid pest dispersal by human activities, it’s essential for the farmer to carry out management practices from the uninfected area towards the infected one.

To control the mealybug, regular monitoring and scouting should be done, and preventive measures such as using resistant varieties, practising crop rotation, and most importantly maintaining the farm hygiene done.

It is also vital to check on the fertiliser programme, especially on the use of nitrogen since high nitrogen levels, and soft growth attracts the mealybug. Overhead irrigation can also be used to wash off the pest.

Biologically, the pest can be controlled by use of ladybird- Cryptolaemus montrouszieri — commonly known as mealybug destroyer or use of parasitic wasp that feeds on the larvae. Lacewings can also be used to control the pest.

Use of neem oil helps to disrupt the growth and development of the pest, since it has repellent properties to the mealybug.

In most cases, ants may be found in areas where mealybugs have infested the crop since they feed on the honeydew. This makes ants protect the bugs from predators to ensure continuous food supply.