Find answers on how to ward off snails and heal tomatoes

How do I go about farming tilapia fish?

I would like to farm tilapia fish but I don’t know how to go about it in terms of making ponds, stocking, feeding and management. Please advise.

Juliet Mulaka

Tilapia is a warm water fish and can do well in most geographical locations in the county where there is adequate water which is not very turbid. There are several factors to consider in constructing an earthen pond for tilapia culture.

Preferably, the soil should not be very porous otherwise a plastic liner should be used. The pond should be sited on gently sloping land to take advantage of gravity both for inflow and draining the water.

The size of the pond depends on the population of fish the farmer should keep, but generally, the deep end should not exceed 1.2m and the shallow end 0.6m in depth. Very shallow ponds are prone to predation, weed encroachment and limit stocking density, lowering pond productivity.

Fish cultures in earthen ponds feed on natural resources but it’s advisable to supplement especially in overstocked ponds. Routine management includes weed control, pond fertilisation, among others. Kindly visit the fisheries office near you for further advise on commercial feeds availability.

James Chege Wangui,
Department of Animal Sciences,
Egerton University.

Help: snails have invaded our shamba

Snails have become a big menace in our shamba. They come in large numbers and chew up anything we plant. We have tried a variety of pesticides but with no results. Please help.

Tony Mwaro

I wish you had said where you farm since snails are not widely spread in Kenya. However, the giant East African snail (Achatina fulica), is a herbivore and eats a wide range of plants, fruit and vegetables.

It will sometimes eat sand, very small stones, bones from carcasses and even concrete as calcium sources for its shell. In rare instances, the snails will consume each other. Compared to other snails, this pest is really big, about 20 cm long, with the shell making up half its length.

It is also showy, with a light-brown shell striped with brown and cream bands. Control is mainly by use of cultural practises like good field sanitation, sprinkling their habitats and/or around crop base with table salt in dry seasons, and trapping with brewers’ waste in water container since they are attracted by the yeast and they get drowned when going for the ‘brew’.

The most effective way which may NOT be available in Kenya is use of biospesticides, mainly metal salt-based molluscicides as snail baits and snail pellets and also Sluggo Plus® (a blend of iron phosphate and Spinosad). This product is not commercially available in East Africa.

Paul Kimurto
Crop Science Expert, Crops Horticulture and Soils Dept,
Egerton University

How do I make my paw paws sweeter?

I am a first time large-scale pawpaw farmer in Machakos County. I read on November 11 in Seeds of Gold that pawpaw plants need potassium fertiliser for sweetening and better colouring. I have three questions:

(i) At what stage of the plant should the potassium fertiliser be applied?

(ii). What are the major threats (diseases) that affect pawpaw; both the plant and fruit, and what are the pesticides to be applied in both cases and at what interval?
(iii). How long does the fruit take to mature and ripen?

Kinama Maluki

It’s true papayas need quite a bit of potassium to develop sweet fruit. However, crop nutrition is important at all growth stages. You need to do some basic soil analysis to get a fertiliser regime for your soil.

In general, I would recommend the application of 500g of a compound fertiliser NPK 5:7:4 and 250g of SSP per planting hole as a pre-plant application well mixed with the hole filling mixture.

After that a post-plant application of 100g per plant of NPK 10:2:16 every 4-6 months from the second year is adequate to maintain cropping and fruit quality. If you opt for tissue analysis the critical nutrient levels are: N=1-1.4%; P=0.15-0.18% and K=2.5-3.5%.

Papayas grow for 4-6 months before they flower depending on the prevailing temperatures (especially night temperatures) and soil moisture.

Fruits take 3-4 months to mature and ripen after formation. For distant marketing, pick the fruits when they lose the deep green colour and become dull. For nearer fresh markets pick when the fruits start turning.

Common diseases in papaya in Kenya include Phytophthora root rot, Fruit anthracnose, Powdery Mildew and Papaya Ring Spot Virus. For proper control advice, please visit our website www.egerton.ac.ke for a free pdf downloadable fact sheet on diseases affecting papaya.

Richard Mulwa,
Horticulture and Fruit Science expert.

Is black cotton soil suitable for my plans?

I come from Got Nyithindo in Muhoroni and we are blessed with a good climate and predictable rainfall. However, I am not sure what crops the black cotton soil is suitable for.

I plan to venture into farming fruit, cabbage and carrot farming. Can our soils support these crops?

Maurice Osodo

You can do all these crops on black cotton soil. The only thing you need to do is to loosen the soil so it does not crack by adding a lot of plant-based decomposed manure, especially if you want to do carrots and fruits.

If you can afford this, black cotton soils ameliorated with plant based organic matter can provide very good production soil environments for most vegetables.

Richard Mulwa,
Horticulture and Fruit Science expert