- It hides in the soil and feeds on the underground parts during the day and on the upper parts at night.
- Common in weedy spots, fields with high organic matter and poor drainage.
Control
- Eliminate weeds two weeks to planting.
- Scratch soil near plants in the evening to uncover and remove them.
- Till and plough soil to expose the caterpillars.
Bio-pesticides
- Use Bacillus thuringiensis (BT) products.
Chemical control
- Use Synthetic Insecticides as recommended by PCPB.
- Examples 5% Malathion, Dipterex (Dylox) Trichorphon 5% and pyrethroids.
African bollworm Helicoverpa armigera Hb.
- African bollworm caterpillars vary from dark green, reddish, brown, whitish and orange in color and have a white band on each side of the body.
Control
- Physically checking for the caterpillars on the plants to help plan for control before the numbers increase.
- Practice deep cultivation to destroy pupae in the soil.
- Avoid planting crops that are attacked by the same pest.
Natural enemies
- Use of predators such as syrphid flies, ladybird beetles.
Bio-pesticides
- Use of microbial biocontrol agents such as Bacillus thuringiensis (B.t.), nuclear polyhedrosis (NPV) Metarhizium anisopliae (M.a) neem products and insect growth regulators such as Match.
Chemical control
- Control young caterpillars before they enter the fruit.
- Use PCPB Registered chemical products such as Deltamethrin, Carbaryl,Spinosad, Bifenthrin, Indoxacarb, Pyrethrin, Methomyl and Novaluron among others.
White flies
- The adults are white winged flies of about 1.5mm long that mostly hide under the leaves.
- They suck plant sap from the underside of the leaf resulting in wilting and leaf malformation.
- The insect excretes a sticky sugary substance (honey dew) which the ants feed on resulting into formation of a Sooty mould.
- The sooty mould affects leaf function.
- Whiteflies easily spread diseases like cassava mosaic virus, cotton leaf curl, tobacco leaf curl and sweet potato virus B.
Control
Natural enemies
- Parasitic wasps like Encarsia formosa parasitizes the larvae and eventually the larvae dies.
Bio-pesticides
- Use approved Neem products.
Chemical control
- Use PCPB Registered chemical products such as (Rogor), Diazinon or Brigade.
- Ensure good coverage on the underside of the leaves.
Red spider mite, Tetranychus spp
- It is a major problem on tomato.
- They multiply very rapidly especially in warm, dry weather thus when left uncontrolled the farmer can lose his production within a week.
- Destroy plants within a short period of time.
- The mites easily spread by wind, irrigation water, dust storms, clothing and implements.
Control
Cultural practices
- Regular scouting of the crop to determine the presence of the pest and the level of infestation in an early stage.
- Separation of infected crops and newly planted crops or nursery areas and the burning or removal of infected crop residues and weeds.
Natural enemies
- Predatory mites such as Phytoseilus persimilis are effective especially in the green house.
-
- Planting host plants of predatory mites such as pigeon peas helps control the mites.
- Inter-planting tomatoes with garlic or onion, practicing field hygiene, use of resistant cultivars and bring spider mites on check.
- Heavy rain or overhead irrigation can reduce their numbers.
Botanical pesticides
- Use of Neem (Azadirachta indica) and Tephrosia sp.
Chemical control
- Effective insecticides include Abamectin, Amitraz, Dicofol, Clofentezine, Bifenthrin, Tetradifon and Azadirachtin.
- *Red spider mite species easily develop resistance against these pesticides and acaricides therefore there is need to practice crop rotation and also alternate products of different chemical compositions.*
Leaf hopper adult
- They suck sap from the plant and excrete excess fluids in the form of honeydew.
- This sugary substance may support the growth of sooty molds.
- It feeds on leaves, leaving a mosaic of white specks and stunting growth.
- They also spread Curly Top Virus.
- The pest can cause severe stunting on young plants and eventually die.
- Older plants turn yellow, leaves roll upward, fruit production ceases, and plants slowly die.
Leaf miners
Source:Infornet Biovision.org
- Adults are small black and yellow flies about 2mm long.
- Eggs hatch into small larvae that feed by mining in the leaf making a tunnel as they move along.
- Feeding and mining on leaves can kill seedlings and in older plants allows entry of fungal diseases.
- Damaged leaves fall prematurely thus reduces plant yield and exposes the fruits to sunburn.
Control
Biological control
- Use parasitic wasps such as Diglyphus isaea.
- Use yellow sticky traps or yellow basins filled with water to attract and kill the adult leaf miner.
- Destroy old crop remains and rotate with non-host crops.
Chemical Control
- Use PCPB approved insecticides such as Abamectin, and Spinosad among others.
Tuta absoluta (Tomato leaf miner)
- The pest reproduces rapidly and can cause up to 100% yield loss.
- Caterpillars makes a tunnel inside the leaf, stem or fruit but exit when pupating.
- Pupae are light brown and are found in the soil, on the leaf surfaces or in the tunnel.
- Adults are grey- brown moths and active at night.
- Eggs are deposited on the underside of leaves.
- Serious infection leads to the leaves dying off completely.
- Mining to the plant causes malformation and damage to fruit paves way for fungal infections, leading to fruit rot before or after harvesting.
Management
- Use of Bacillus thuringiensis products (bt) and PCPB approved Chemical insecticides.
- Use sex pheromone to trap and kill the males thus help in reducing the populations.
Aphids (Aphis gossypii, Myzus persicae)
- They suck plant sap, secrete honeydew which causes sooty moulds.
- This affects plant growth, fruit quality and value.
- They also transmit virus diseases during feeding such as the cucumber mosaic virus.
Control
- Natural enemies like ladybirds feed on the Aphis.
- Use yellow sticky traps.
- Use reflective aluminum mulch to deter aphids from landing on plants.
The tomato russet mite (Aculops lycopersici)
- They are yellowish, brown or pink tiny mites.
- They feed on all above-ground parts of the tomato plant, causing spotting, twisting or folding of leaves and fine cracks on the fruits.
- Infested leaves and stems develop a greasy appearance and turn bronze.
- The plants can drop their leaves and expose the fruits to sunburn.
- Damage to the plant typically begins near the ground and spreads upwards.
Control:
- Use of Predatory mites.
- Neem extracts (Neem oil and aqueous neem kernel).
Thrips (Thrips tabaci, Frankliniella occidentalis, F. schultzeii and Ceratothripoides brunneus)
Source: https://www.greenlife.co.ke/tomato-thrips/
- Thrips are very small (about 1 to 2 mm long).
- They usually feed by sucking sap on the lower surface of leaves.
- They also attack and damage flower buds, flowers and fruits leaving a speckling silvery sheen.
- Under heavy infestation attacked buds, and flowers usually fall off and fruits may become deformed.
- They are vectors of viruses such as the Tomato Spotted Wilt Virus.
Control:
- Use Predatory mites (eg. Amblyseius sp.), anthocorid bugs (e.g. Orius spp.), ladybird beetles,
- lacewings, spiders, and the fungus Entomophthora.
- Plough and harrow before transplanting to expose and destroy pupae in the soil.
- Soil solarisation and flooding of previously infested fields prior to planting/transplanting
- Use of bio pesticides like Neem and other plant extracts.
- Spray with PCPB approved chemical insecticides and mix the spray mixture with a sugar solution to attract the thrips out of the flowers.
Major Diseases
Root Knot Nematodes (Meloidogyne spp)
- Severe infestations result in stunted plants.
- Deformed roots results in plant wilting and nutrient deficiencies.
- Swollen damaged roots may become entry point for other disease causing organisms (fungi, bacteria and viruses).
- Control
- Practice Crop rotation, and burn infested plant debris.
- Intercrop with Mexican marigold weeds that repel the nematodes in the soil.
- Use resistant crop varieties.
- Deep plough the field then leave it exposed to the sun for sometime out.
- Use registered nematicide such as Methane Sodium,
- Paecilomyces lilacinus and Azadirachtin among others.
Bacterial Wilt (Pseudomonas solanacearum)
- It is one of the most economic diseases of tomato. This disease causes wilting of tomatoes.
- It is mainly seed borne but pathogens are also found in the soil.
- Symptoms first appear on the youngest leaves and a rapid wilt of the whole plant occurs.
- Testing for this disease can be done by suspending a part of infected stem in water whereby a whitish slimy stream will be observed in the water.
Control
- Practice crop rotation with a non-susceptible crop.
- Raise seedlings in pathogen free soil.
- Remove and burn infected plants.
- Plant resistant tomato varieties.
Late blight (Phytopthora infestans (Mont.) de Bary)
- It’s a very destructive diseases of tomato.
- It attacks all above ground parts of tomato.
- Leaf lesions begin as water soaked spots which rapidly enlarge to brown lesion covering the entire leaf which then dries up.
- Infected leaves shrivel, die and dry up.
- Infected areas on stems appear brown to black.
- Decaying stems produce a rotting smell.
Control
- Maintain the field clean, free from weeds.
- Practice crop rotation.
- Use tomato seedlings from a disease free nursery.
- Apply protective fungicides e.g. Antracol (Propineb), Dithane M-45 (Mancozeb) every 7-10 days and alternte with systemic curative and protective fungicides like Ridomil (Metalaxyl) and Milrax (Propineb+Mancozeb) at 14 day intervals.
Early blight
- It is very serious disease on tomatoes during the hot weather.
- It occurs on all above ground parts and is destructive at all stages of crop development.
- It begins as small brownish/black lesions on leaves and later the whole leaf turns yellowish.
- Usually starts on the older leaves and can cause extensive dying and falling of leaves, exposing the fruits to sunburn and lowering of yield.
- On stems, cankers form and occasionally fruits are infected causing premature fruit drop.
- Stem lesions on infected seedlings will continue to enlarge and subsequently girdle the seedlings.
- The most important diagnostic feature of early blight is the formation of dark round rings around the infected spot.
Control
- Deep-plough to bury tomato debris, or remove and destroy infected plants.
- Practice crop rotation.
- Use clean planting seedlings and certified seeds.
- Spray protective fungicides e.g. Antracol (Propineb), Dithane M-45 (Mancozeb) every 7-10 days alternating with systemic curative and protective fungicides like Ridomil (Metalaxyl) and Milrax (Propineb+Mancozeb) at 14 day intervals.
Bacterial canker (Clavibacter michiganensis subsp)
Source:Plantwise.org
- Symptoms do not appear until the disease is well established in the field.
- Symptoms on young seedlings are difficult to see, but often start as dark water soaked areas on leaves and stems.
- Infections result in wilting followed by discoloration of the vascular tissue.
- Stems may split vertically with dark brown necrotic cankers developing under certain conditions.
- Disease development is favored by warm, wet soil conditions.
- The disease can reduce yields by as much as 90%.
- Lower leaves wilt and turn downwards.
- The whole leaf then starts to dry, curls upwards turns brown and withers, but still remain attached to the stems.
- When Stems are split open the middle part of is often found to be discolored.
- Fruit symptoms are patches with raised brown centers surrounded with an opaque halo.
- The most diagnostic feature of bacterial canker is the formation of fruit spots that are bordered by a distinct white halo.
Control
- Use of certified seeds and transplanting into disease-free soil.
- Remove and burn infected plant material.
- Practice crop rotation.
- When pruning, disinfect the pruning knife after every 2 plants using Jik or Dettol.
- Plant Resistant/tolerant varieties.
- Apply copper-containing fungicides to suppress the bacteria.
Fungal Diseases
Fusarium Wilt (Fusarium oxysporum f. sp. lycopersici.)
- Fusarium is common where continuous growing of tomato is practiced and can remain in the soil indefinitely
- Fusarium can come from seed and soil and also hides in weeds
- Thrives well at warm temperatures of 25 – 32 0C and acidic (pH 5.0-5.6) soils
- Infected plants get stunted because the vascular system is affected
- The leaves turn yellow on one side while the other side remain healthy and green
- It causes discoloration of the inner part of the stem and the plants eventually succumbs to the disease and decays.
Control
- Apply lime to increase the pH of the soil (pH 7.0).
- Use nitrate nitrogen rather than ammonium nitrogen.
- Practice crop rotation but avoid crops like peppers, eggplant, potatoes, sunflower, alfalfa, sweet clover.
- Remove and destroy debris and crop leftovers after harvest.
- Avoid flood irrigation.
- Use resistant varieties or graft tomatoes onto resistant rootstocks.
Verticillium Wilt
- Verticillium wilt on tomato. Photo by Lindsey du Toit. Source:Plantwise.org
- This disease is common in cool temperatures (21-25 ºC) and occurs in all tomato-growing regions.
- Symptoms are can sometimes be confused with Fusarium wilt but
- the difference is that plants show wilt symptoms during the warmest period of the day.
- Lower leaves turn yellow (interveinal chlorosis) and falls off the plant.
- These symptoms are easily seen during periods of drought or when the plant is heavy with fruit.
- There is a brown colouration if the stem is cut lengthwise.
Control
- Practice a 3 to 4-year crop rotation but avoid rotating with peppers, eggplant, potatoes, sunflower, alfalfa, sweet clover.
- Remove all debris and crop remains after harvest and control weeds.
- Use clean seeds/seedlings and resistant varieties.
Powdery Mildew-Leveillula taurica
Source: https://www.greenlife.co.ke/powdery-mildew/
- The disease is seen as white powder on the leaves.
- Older plants are more affected.
- Infection occurs when temperatures and humidity are high.
- Disease starts on the upper side and spreads to lower leaf surface.
- Damaged Leaf surface develops yellow patches which later die.
- Reduced leaves results in fruit sunburn and weak plants.
Control
- Remove and destroy crop debris after harvest.
- Keep the field free of weeds and practice crop rotation.
- Use registered chemical products such Azoxystrobin, Myclobutanil, Thiophanate, Tebuconazole,Kresoxim-methyl and Sulfur based fungicides among.
Anthracnose (Colletotrichum spp)
Source:Infornet biovision.org
- This disease is mainly a pathogen of the tomato fruit.
- As the fruit are ripening some small, circular and sunken areas are seen, which later turn dark.
- The infected spots continue to grow larger as the infection spreads deeper into the fruit.
Control
- Ensure crop rotation for 3 about years.
- Remove weeds that can act as hosts.
- Use disease-free or treated seed.
- Use recommended Fungicides (like chlorothalonil) to help reduce the disease.
Viral diseases
Tomato Common Mosaic Virus (TCMV)
Source:Infornet biovision.org
- The disease is seed borne.
- It can be mechanically transmitted through transplanting seedlings and pruning.
- Damage Affected plants show dark and light green mottling effect and some distortion of young leaves, as well as disturbed or
- elongated leaves with a fern leaf characteristic.
- Under high temperatures and high light intensity, mottling is severe while under low temperatures stunting and leaf distortion is severe.
- Fruits are discoloured as well as show brown streaks inside.
Control
- Use resistant varieties and certified disease free seeds.
- Remove crop debris and roots from the field Avoid smoking while in the farm as it is believed the virus is transmitted from tobacco.
- Field hygiene should be well practiced.
- Chemical Control -no chemicals to manage the disease.
Tomato spotted wilt virus (TSWV)
Source:Infornet-biovision.org
- Commonly known as ‘Kijeshi’,
- Important symptoms are seed as rings on the mature fruits which become red and white or yellow and red hence the name Kijeshi (like the army color).
- Other symptoms can be seen as Necrotic spots, streaking, ring spots, stunting and wilting.
- Maily spread by Thrips (Frankinella occidentalis).
Control
- Manage thrips in the field to avoid transmission of the virus.
- Remove (sanitation) and destroy all infected (symptomatic) plants and destroy all weeds. break the disease cycle by avoiding continuous cropping.
Tomato Yellow Leaf Curl Virus (TYLCV)
Source:Infornet-biovision.org
- This disease is mainly transmitted by whiteflies and causes severe loss in yield.
- Whiteflies transmit the disease into the field from infected weeds such as nightshade, Datura stramonium and jimsonweed.
- The leaves curl, turn yellow along the leaf margins (chlorotic), and become smaller than normal.
- Plants have very few flowers hence few fruits or no fruits at all.
Control
- Remove plants with initial symptoms to slow the spread of the disease.
- Practice intercrop with other plants like onions, chives and garlic that trap or repel whiteflies.
- Maize crop can also be planted as border crop to reduce the movement of whiteflies towards the crop.
- Use sticky traps to control the
- vectors population.
- Control weeds that act as alternate hosts for the whiteflies.
- White flies should be controlled to discourage spread of the virus; for instance, by use of oil sprays.
Nutritional disorders
- Common in soils that are poor in organic matter.
- They are observed as patterns of leaf discoloration or fruit abnormality.
- The common nutritional disorders in tomato are;
- Blossom end rot caused by calcium deficiency.
- Chlorosis of older leaves due to nitrogen deficiency.
- Stunted growth, purpling of leaves and late fruit maturation due to phosphorus deficiency.
- Drying of leaf margins coupled with hollow fruit due to potassium deficiency.
They can be corrected by application of foliar fertilizers (foliar feeds).