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Vernonia

Vernonia is an erect annual herbaceous weed, which can reach up to 1 m tall. It is bushy and has reddish stems. The weed produces purple flowers. Mostly found on grassland and loam soils.

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Diseases

  1. Leaf spot can cause yield losses that range from 40-60%. Early leaf spot is seen as reddish-brown spots on the upper surface of leaves surrounded by a yellow halo and brown on the lower leaf surface. Symptoms are first observed on the older leaves. L...

  2. Powdery mildew losses are as a result of losses due to reduced crop yield and quality. Crop yield losses of more than 20 % due to powdery mildew incidences have been recorded. Powdery mildew is observed by powdery splotches of white or gray fungal gr...

  3. Downy mildew is usually prevalent on older onion leaves and stalks. The first evidence of disease is a fine, furry, greyish white to purple growth on the surface of older leaves. Colonies often appear first on the underside of leaves. Small yellow sp...

  4. Common bean mosaic virus causes yield losses due to loss of photosynthetic area. Losses of up to 70% have been recorded in some fields. Common bean mosaic virus symptoms appear as a light green-yellow and dark green mosaic pattern, or they may also a...

  5. Severe yield losses of more than 50% are observed with grey leaf spot. Symptoms of grey leaf spot are usually observed on the lower leaves of the maize plant. Grey leaf spot first appears as small, necrotic spots with chlorotic halos (more visible wh...

  6. Losses due to maize streak virus are usually as a result of loss of photosynthetic area. Yield losses of up to 100% are common with the disease. Maize streak virus develops as small, pale, circular spots or flecks on the youngest leaves (older leaves...

  7. Anthracnose is a disease of economic importance in beans, causing upto to 60% losses. The leaves, petioles, stems, roots pods of bean plants are usually susceptible to infection by anthracnose. Symptoms are usually visible soon after crop emergence a...

  8. Yield losses due to corn smut may approach 100 %. Smuts appear in the stalks, leaves, tassels or ears. Whitish-gray irregularities which expand and turn black as they fill with spores are observed first. Galls on leaves remain small, fleshy and smoot...

  9. Rust can cause yield losses that can go up to 25%. Rusts develop on all parts of the plant but are more numerous on the underside of leaves, stems and pods. Initially, tiny, white, slightly raised spots which will become distinct round reddish-brown ...

  10. Early blight can cause total plant losses if it is not controlled properly. Early blight is observed by brown spots with concentric rings that form a “bull’s eye” pattern usually on lower, older leaves first. These may be observed on the stem as dry,...

  11. Total crop losses are common without proper management of late blight. Late blight first appears as small, grey-green (which darken with time), water-soaked spots (lesions) usually on the underside of the leaf. The spots will enlarge and a white mold...

  12. Severe infection with halo blight can result in total crop loss. Halo blight usually affects the foliage and pods of beans. Leaf symptoms first appear as small, water-soaked spots on the lower leaf surface. These lesions rapidly become necrotic and a...

  13. Rosette virus contributes losses of up to 46 %. Groundnut rosette disease is a combination of three diseases: chlorotic rosette, mosaic rosette and green rosette. Plants with chlorotic rosette have bright yellow leaves, except for small parts that re...

  14. Yield losses of up to 90 % have been recorded in cases with soft rots. Bacterial soft rots first appear as necrotic water-soaked spots on the outside of the fruit (also affects leaves, stems and underground parts). These spots enlarge over time and b...

  15. Blotch is observed on all above ground parts.Symptoms are first observed on the lower leaves as yellow spots. These water-soaked spots (lesions) turn dry, yellow then red-brown. The elliptical lesion enlarges, becomes zonate (target spot) and purplis...

  16. Ergot bodies are produced in place of kernels. The ergot bodies have a hard protective rind on the outside, which is black to dark purple in color, and a white to grey colored interior. They are often elongated and protrude from the glumes of maturin...

  17. Total yield losses can be seen where fields are infested with bacterial wilt. Water melons are known to be immune to bacterial wilt. The first sign of bacterial wilt is wilting of 1-2 leaves (or a part of the plant) on young plants during the day and...

  18. Cankers will cause yield losses that range from 70-80 %. Bacterial canker is observed on each growth stage of the plants’ life. Small, white, raised spots may form on leaves of seedlings. The seedling wilts. Leaves on one side wilt first. The whole p...

  19. Black rot causes damage that results in yield losses of more than 50 %. Bacterial black rot in young plants is observed by dark, discolored cotyledon margins which later drop off. Lower leaves develop lesions which are initially seen by a pale green ...

Insects

  1. Larvae occur in two principle forms: the gregarious (gregaria) form characteristic of high-density populations and the solitarious (solitaria) form found at low larval densities. Intermediate, 'transiens' forms may also be present. Gregarious larvae ...

  2. Adult maize leafhoppers are mostly pale yellow-green and very small (about 3mm long). Two small brown or black spots are found between the eyes on the front margin of the crown of the head. These leafhoppers have two small black spots and brown marks...

  3. The egg is bluish changing to grey before hatching. The body of a newly batched caterpillar is pale cream or greyish-white. Characteristic red markings appear in the second instar and it is this deep red color which makes them easily distinguishable...

  4. The whitefly life cycle begins as yellow-orange, minute cigar-shaped eggs laid on end in groups or clusters usually on the undersides of leaves near the terminal. These eggs are sometimes laid in a circular pattern. The first instar nymph that emerge...

  5. The tomato red spider mite is highly polyphagous, widely spread across the world. Under optimum conditions, it reaches a high population density, and its presence can cause a reduction in crop yield. The adult female red spider mite is very small abo...

  6. Adult tomato leaf miner has a grey-brown colour, about 6 mm in size, a wingspan of 10 mm with silver grey scales. Male leaf miner moths are darker than females. Leaf miner larvae are about 9 mm when fully grown with a pinkish colour on their back. W...

  7. Maize stalk borer larvae is cream to light brown in colour with a dark purple saddle on the front half of the body. Both sides of the larvae head have dark streaks. Head is dark brown and the prothorax is yellowish-brown. Its spiracles (breathing hol...

  8. Maize cutworm larvae are plump, smooth-skinned and greasy in appearance. The body is about 40 mm long with two spotted yellow stripes on the back and colour ranges from grey to dark brown. Fully grown larvae coil up in a c shape and remain motionless...

  9. Fall armyworm larva is brown/grey with distinct tubercles along the body. It has three thin white stripes down the back and a distinct white inverted Y on head. Young larvae may be difficult to distinguish from corn earworm (CEW). Caterpillars are of...

  10. The Bagrada bug adult is black, orange with white markings. It is oftenly found in a mating position. Adult bugs are about 5- 7 mm long with a shield-shaped body. Females lay eggs in the soil beneath host plants but may also oviposit on leaves or on ...

  11. A small, elongated, coloured pale brown moth with a wingspan of 15-17 mm and about 1 cm in length. Front wings are pale brown in colour with small blotches of brown and the hind wings are pale grey. The larvae is 15 mm long, dark brown head and has a...

  12. African bollworm moths have a 40 mm wingspan making them strong fliers. Forewings are reddish-brown and have irregular green lines. Caterpillars/larvae have an elongated creamy-white to reddish-brown body, with a brown head. The back has short fine h...

  13. The adult is a shiny black fly, with clear wings and is about 2 mm in length and 5 mm wide. Adult flies lack a visible head, has red eyes and resembles a house fly in color, but is smaller and more slender. The full grown maggot is white, about 3-4 m...

  14. Adult fruit flies are yellow-brown or brownish black in color and are 3 mm long and 2 mm wide. They have a round head, red compound eyes and short antennae. The female is slightly larger than the male whilst males have a greater amount of black pigme...

  15. Root-knot nematodes are not visible to the naked eye. They are obligate endoparasites that complete their life cycle within root of their host. In soils, nematodes survive as eggs and also second stage larvae. Identified by swollen galls/ knots on th...

  16. Young larvae of the cabbage looper start off as dusky white and hairy and eventually turn green (with a distinct white stripe marked on each side) and hairless as they grow and feed on leaves. The head and thoracic legs are pale green or brown. Larv...

  17. The aphid is small to medium sized, 1.2-2.5 mm long and colour ranges from yellow, all shades of green, to pink, red and almost black. Adult wingless damaging females are oval-bodied, 1.2-2.1 mm in body length, of very variable colour; whitish green...

  18. The maize weevil is a dull red-brown to nearly black winged snout beetle with fine microsculpture and is shiny. The antennae has eight segments and are often carried in an extended position when the insect is walking. The species usually have four pa...

  19. Adult flies are principally yellow and black in color, range 1.25 -1.7 mm in length with black hind margin of the eyes. This is a legless maggot with no separate head capsule, transparent when newly hatched but colouring up to a yellow-orange in late...

  20. Onion thrips are pale yellow (occasionally black), small 'cigar' shaped insects with fringed wings. They are tiny and just visible to the naked eye. There are many different species and most cause injury to plant tissue. A heavy infestation of thrip...

  21. Sorghum shoot fly is similar to housefly but smaller in size (3-5 mm long), greyish in colour, yellow with brown patches on abdomen. The male is more blackish. The larvae or maggots are yellowish or whitish in colour, up to 8 mm long. The full grown ...

  22. Diamondback moth has been recorded everywhere where cabbage is grown and it is highly dispersive. The diamondback moth has four instars. Throughout their development, larvae remain quite small and active. If disturbed, they often wriggle violently, m...

  23. Although the Larger Grain Borer develops best at high temperature and relatively high humidity, it tolerates dry conditions, and may develop in grain at low moisture in contrast to many other storage pests, which are unable to increase in number unde...

  24. Hot, dry weather favours sweet potato weevil development. At optimal temperatures of 27-30 oC. C. formicarius completes development (from egg to adult) in about 33 days. The adult weevil is 5-7 mm long, slender, smooth and hard-bodied ant-like insect...

Weeds

  1. Bur grass is an annual tufted, herbaceous weed that can reach heights of up to 1 m. The branches are spreading geniculately and often develop roots at the lesser nodes. It has glabrous (smooth) nodes, which are usually dark in color. The leaves are u...

  2. Jungle rice is an annual grass, which can grow up to 1 m tall with fibrous and rather shallow roots. It is tufted, stoloniferous with green to purple flowers. Seedlings have rolled leaves with pointed tips. The blades and sheaths are usually, but no...

  3. Shamva grass or Itch grass is an erect annual grass, which can grow to 4 m or more in height. The plant is stout, strongly tufted with a dark red base and frequently with aerial prop roots with 15-60 cm long and 0.5-2.5 cm broad leaves. Its inflores...

  4. Wild oat is an erect, tufted annual grass, which can grow up to 1.2 m. It has a typical oat appearance with an anti-clock wise direction leaf spiral. The leaves have dark green blades, up to 40 cm, with a membranous ligule 1-6 mm long and often irreg...

  5. Yellow nutsedge is an erect grass-like perennial sedge with shiny yellowish-green leaves, triangular stem, golden brown flowers, underground rhizomes and many nuts-like tubers. Yellow nutsedge is troublesome in the tropics, however it is most problem...

  6. Billygoat weed is an erect, branching and annual herbaceous plant with shallow fibrous roots. Depending on environmental conditions, it can grow up to 1.5 m tall. Its stems, which are cylindrical, may root at the base, and becomes strong and woody as...

  7. Black Jack is an annual herbaceous erect weed, which can grow up to 1.5 m tall. It has four sided deep purple stems with dark green opposite leaves and branches. The weed produces black-dark brown linear seeds, yellow barbed awns. Black Jack can usu...

  8. Black Nightshade is an annual or sometimes biennial herbaceous weed, which can reach up to 1.0 m in height. Its stems are cylindrical, green to purplish, but vary from prostrate or erect and are branched. The leaves are alternate, ovate and are carri...

  9. Creeping sorrel is a stem-less perennial weed with a tap-root, which reaches up to 6 cm long. It has 1-2 cm diameter bulbs, which are complex with two main types of scales which are referred to as membranous and true scales. Membranous scales are the...

  10. Upright Starbur is an annual erect herbaceous plant, which grows up to 90 cm tall. Its stems are covered in stiff hairs and leaves are in opposite pairs. Upright Starbur produces small and yellow flowers and a spiked fruit. The fruit consists of wed...

  11. Dwarf marigold is a delicate, branched annual herb. Its leaves are mostly pinnately dissected with filiform segments. It produces many yellow flowers on numerous erect stems, which becomes woody as it grows. Mostly found on disturbed lands. The plant...

  12. Fat hen is a green, erect, branched (occasionally un-branched) annual herbaceous plant, which is more or less coated with white mealy pubescence. The leaves are simple, alternate and stalkless with a white mealy covering. The weed is common in arable...

  13. Field bindweed is a climbing or creeping perennial herbaceous weed with slender twining (anti-clockwise) stems, which can reach up to 1.5 m long. It has a very deep root system on which shoots develop from the buds. The leaves alternate, petiolate, v...

  14. Gisekia is an annual or perennial herbaceous weed with erect red tinged stems, which can reach up to 50 cm tall. It is similar to Purslane with green stems, narrow elongated and fleshy leaves with distinct midrib. It produces pale to deep pink flower...

  15. Gallant Soldier is an annual herbaceous and erect plant, which can reach 80 cm in height. Its leaves are simple, alternate and the lower leaves have petioles. The leaf blades are oval to oblong with sharp apex. It bears yellow hermaphrodite flowers....

  16. Iron weed is an annual herbaceous weed, which can grow up to 60 cm tall. It has a woody stem, which is ribbed, hairy and leafy especially at flowering time. The weed reproduces from seeds.

  17. Mexican clover is a perennial (or possibly annual) herbaceous plant, which produces small white flowers with triangular lobes. It has a distinct groove which divides the leaf into two. The leaf is hair less and the plant is an indicator of low soil p...

  18. Mexican Marigold is an erect annual herbaceous woody plant, which can grow up to 2 m tall. The stems and branches are pale brownish and sometimes reddish in colour. Leaves occur in opposite pairs on the main stem and usually singly on the laterals. T...

  19. Mexican poppy is an annual herbaceous plant with erect stems up to 1.5 m tall. The plant is prickly, pale bluish-green in color and exudes an unpleasant-smelling yellow sap when cut. It has alternate leaves, without petioles. Mexican poppy produces ...

  20. Morning glory is a herbaceous annual climber, which can grow up to 3 m in height. It has cylindrical, slender and pilose or hairy stems with heart shaped leaves. The weed forms red-violet-blue or purple and or sometimes white flowers with a white cen...

  21. Painted euphorbia or Wild poinsettia is an erect herbaceous weed, 2 m tall. It secretes milky latex when plant parts are broken. Its stems are branched and cylindrical, with nodes at regular intervals and the surface is smooth and reddish-green. It h...

  22. Pigweed is an annual herbaceous plant with branched erect stems up to 20 m tall. The stems are thick and usually red ribbed. Pig weed produces numerous green flowers, which are crowded into finger-like spikes forming a long, dense terminal panicle, w...

  23. Purple garden sorrel is a stem-less perennial weed with a tap-root, which reach up to 6 cm depth. It has 1-2 cm diameter bulbs, which are complex with two main types of scales which are referred to as membranous and true scales. Membranous scales are...

  24. Spindle pod is an erect annual herbaceous plant which occurs in a wide variety of habitats. Its stems and leaves have glandular hairs. The leaves are simple and narrowly lanceolate. Spindle pod produces inflorescences with purple markings on the peta...

  25. Spiny sida is a small erect perennial shrub with copious branching from the base and can grow up to 1.5 m tall. When young, it is similar to stock rose but the leaves are more pointed and later on serrated. Its stems are more or less densely covered...

  26. Stock rose is an annual or biennial herbaceous erect weed, which can grow up to 1.5 m high and habitually, branched from the base. The weed has sharp and shortly tomentose stems. Occur mostly in disturbed lands. It aggressively competes for nutrients...

  27. Thorn apple or Stinkblaar is a smelling, bushy and erect annual herbaceous weed, which can grow up to 2 m tall. Its roots may be shallow and extensively branched, but in some soils a stout, branched peg-like taproot with extensive stringy lateral roo...

  28. Thorny pigweed or Spiny amaranth is an annual, herbaceous erect plant, which can grow up to 3 m tall. It has divergent spines on stems and branches. The striated, often reddish, stem with two sharp, long spines at the base of the petioles, and the fr...

  29. Vernonia is an erect annual herbaceous weed, which can reach up to 1 m tall. It is bushy and has reddish stems. The weed produces purple flowers. Mostly found on grassland and loam soils.

  30. Wild celery is an annual herbaceous plant with erect stems reaching up to 0.5 m maximum height. The stems are sometimes branched from the base with thread-like green leaves, spherical flowers. The leaves have 3 to 4-pinnate which are finely divided. ...

  31. Wild Cucumber is a climbing annual vine plant. The weed has long twisted vines, which tangle the leaves, stem and branches of crops. It has light green leaves, up to 14 cm wide, with 3-7 large pointed lobes. Wild cucumber characteristically can crea...

  32. Wild gooseberry is an erect annual herbaceous weed, which can reach heights of 2 m. The stems are hollow and usually glabrous (hairless) with tap roots. Its leaves are dark dull green, rounded (asymmetric) at the base and are usually unevenly toothed...

  33. Wild jute is an annual branched herbaceous plant, erect when young and growing up to 60 cm high (spread branches when old). Its leaves are oblong to lanceolate, up to 11 cm in length and are hairless or sparsely hairy on the veins, margins crenate-se...

  34. Alectra vogelii is an annual parasitic broadleaf weed of legume crops. It has hairy erect stems which can reach heights of 45 cm. Yellow flowers appear singly on a short stem in the axils of upper leaves or bracts. The Witchweed is constantly linked ...

  35. Striga asiatica is an obligate, annual herbaceous hemi-parasitic weed, which can normally reach 30 cm in height. Its stems and leaves are sparingly covered in scabrid hairs. The witchweed/ strains have different morphotypes with different flower colo...

  36. Annual timothy is an annual tufted weed, which can reach up to 1 m in height. Its stem is cylindrical in shape at seedling stage and at a later stage becomes flat. The inflorescence has green spikelets with long orange or reddish-brown bristles. It p...

  37. Couch grass is a perennial runner grass, which forms stolons and rhizomes underground. The runners spread horizontally and bear nodes with internodes of about 10 cm length. They may be flattened or cylindrical, mostly un-haired. Each node roots in th...

  38. Crab finger grass is an annual, herbaceous grass with leaf blades which are 5-15 cm long and 3-12 mm wide. It has green to purple leaf blades, which are silky on both sides with shiny hairs. The sheaths are green to reddish violet, with long blister-...

  39. Crowfoot is a tufted, stoloniferous annual grass, which can grow up to 0.75 m tall. The seed heads are typical bird's foot, which looks like a crow's foot, hence the name Egyptian crowfoot grass. It is found in arable and uncultivated areas, especial...

  40. Garden urochloa is a tufted annual grass, which grows to 0.6 m tall. Its leaves are loosely to densely hairy with tubercle-based hairs and blades up to 12 mm wide, expanded with light green thickened and crinkled margins. It tends to prefer damp pla...

  41. Natal red top is an annual erect weed, which grows up to 1.5 m tall and produces red flowers. The weed tolerates shallow, infertile, alkaline and neutral soils. Mechanical disturbance to the soil crust and fire both favors establishment of Natal re...

  42. Purple nutsedge is a perennial, herbaceous weed (sedge) with fibrous roots that typically grow from 7-40 cm tall and reproduce extensively by rhizomes and tubers. It has flattened and linear spikelets ranging in length from 10-30 mm long, and general...

  43. Rapoko grass also known as goose grass is an annual, tufted herbaceous grass, which can be erect to about 40 cm tall. It does not usually have roots at nodes and the root system is very well developed and strong. The inflorescence consists of 3-8 rac...

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