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HEMIPTERA OR HETEROPTERA

They have piercing-sucking mouthparts formed into a slender beak. Some are plant-feeding, while others are predatory. Southern green stinkbugs are pests on beans, tomato, cabbage, and macadamia nut. Nymphal stages are dark colored with whitish markings; adults are mostly light green and shield-shaped. Black stinkbugs are small, rounded, and shiny black with pale stripes; they are an occasional pest on beans and some other legumes. Lace bugs cause stippling of leaves similar to other sucking insects. Others bore into seeds. Assassin bugs are important predators of other insects.

True bugs

They have piercing-sucking mouthparts formed into a slender beak. Some are plant-feeding, while others are predatory. Southern green stinkbugs are pests on beans, tomato, cabbage, and macadamia nut. Nymphal stages are dark colored with whitish markings; adults are mostly light green and shield-shaped. Black stinkbugs are small, rounded, and shiny black with pale stripes; they are an occasional pest on beans and some other legumes. Lace bugs cause stippling of leaves similar to other sucking insects. Others bore into seeds. Assassin bugs are important predators of other insects.

Family: Pentatomidae

True bugs have piercing and sucking mouthparts formed into a slender beak. Some are plant feeding, some are predatory. Green stinkbugs are pests in beans, tomato, cabbage and macadamia nut. Black stinkbugs are small, rounde and shiny black with pale stripes; they are an occasional pest on beans and some other legumes. Lace bugs cause strippling of leaves similar to other sucking insects. Others bore into seeds. Assassin bugs are important predators of other insects.

Stink Bugs

Stink bug (Nezara viridula)

Common name: stink bugs

Scientific name: Nezara viridula

They produce the evil-smelling defensive fluid that is associated with all bugs of this family. The bugs themselves are shades of green, and about 15mm by 8mm in dimensions. The long, piercing proboscis lies, when at rest, between the forelegs underneath the body. The nymphs are different from the adults, lacking the green wings. Their bodies are at first colored in a series of black, yellow and white dots, and they are more rounded in shape. Later they are more predominantly green, but still with the colored spots

Host plants

Green stinkbugs are cosmopolitan insects, and have a wide host range. They feed on fruits, crops, vegetable and garden ornamentals, cotton, deciduous fruit, tomatoes, legumes, soyabeans and garden beans, wheat abd nut crops such as macadamia are amongst recorded hosts.

Damage

The bugs feed on developing fruit. Their feeding punctures cause local necrosis, presumably due to a toxin in their salivary juices, with resulting fruit spotting, deformation or even shedding, if inflicted early enough. Sharp indentations are quite commonly seen on still green peaches, and the bugs can inflict damage on soyabeans, causing discolouration of the developing seeds. Obviously the level of plant damage depends on the population level.

Life cycle

Begs are laid in batches of 50-60, stuck together in rafts on the underside of the leaves. They soon hatch into tiny first instar nymphs, which cluster by the eggs and do not feed. There are five instars, with the preferred food being developing seeds or fruit, until, after some eight weeks, the bugs reach adulthood. After mating, they disperse and feed by piercing soft plant tissues and sucking the sap.

Control

Control of stinkbugs in a field crop is seldom necessary. Stinkbugs are sap- suckers, do not succumb rapidly to systemic insecticides, because their large size and short feeding period (often not in the main sap stream) probably mean that they do not pick up enough chemical. This means that stinkbugs must be controlled with a chemical that has contact properties such as;

  • Monocrotophos
  • Trichlorfon
  • Carbaryl
  • Synthetic pyrethroids
  • Endosulfan

 

Cotton Stainer

Cotton stainer

Order: Hemiptera/ Heteroptera

Family: Pyrrhocoridae

Genus; Dysdercus

Identification

They are brightly colored in black and red and reach 10-15mm in length. In general, they have reddish heads, reddish thorax and underside of the body, brownish-orange wings with a black transverse bar about halfway down and a black section at the distal end. They have long bent antennae, red legs and a strong beak projecting forward from the front of the head, with which they pierce the plant tissue. The nymphs, lacking the wings that hide their bodies, are usually recognized by their bright red color.

 

Host plants

The main hosts are cotton and other Malvaceae, but are also found feeding more generally on the baobab fruits.

Damage

Cotton strainers are the most destructive cotton pest. They cause mechanical damage by inserting their long proboscis into developing bolls to feed on the seeds. They may render the seed sterile or at least reduce germination percentages by their feeding, but this would not be serious unless the crop was grown as a seed crop. They cause indirect damage by injecting spores of a fungus known as Nematospora.  Leading to bolls dropped by the plants, or staining of the lint thus affecting their quality. Pale cotton strainers feed on developing and mature cotton seed. Seed weight, oil content and seed viability decline as a result of cotton stainer feeding. Loss of seed viability can be substantial so should be a careful consideration in pure seed crop. Staining of cotton lint has occurred as a result of feeding in young bolls. The bugs transmit a fungal pathogen during feeding causing a reddening of the lint.

Life cycle

After mating, during which adult remain coupled together for a few days, quite large orange hued oval eggs are laid singly or in small loose clusters or batches of up to 100 in moist soil or decaying vegetable matter. Further mating may take place and egg laying can continue for a couple of months. Hatching takes place after 5days at 27c and 8 days at 23c.  There are five nymphal stages or instars, with the first remaining underground without feeding near the place they hatched. They do, however, require moisture to survive. After moulting, the second instar nyumphs go in search of seeds on or near the ground, still congregating to feed and moult. Later instars spread further a field hunting for fruits and seeds on which to feed. The duration of eachof the first four typically four to five days, but the fifth stage commonly takes twice as long. All five stages require from 21 to 35 days to complete. The total nymphal period takes about a month in warm temperature, but may be considerably longer towards the winter months. The nymphs are generally red. The fourth and fifth instars have dark wing pads, and the dividing lines between abdominal segments become very distinct as maturity is approached. The nymphs feed gregariously on the open cotton bolls near the ground. Later they wonder freely on the plant sucking sap from the seed and fruits. Adults are strong flyers and migrate to suitable hosts by this means. This adult is narrow, around 3/5 inch long, long legged, has a bright red thorax, and brown wings crossed with yellow. There is a pre-oviposition period of 5-14 days and the female may live for 70 days. On the plants, they have the habit of dropping to the ground when disturbed.

Control

A crop is not often sprayed specifically to control cotton strainers, as the normal bollworm spray programme of contact insecticides keep them under control. In small plots they may be hand-picked or destroyed. Strict adherence to cotton crop destruction dates assists in keeping the pest numbers down between growing seasons. A range of natural enemies such as Tachinids (parasitic flies) and predatory bugs (e.g. assassin bug). However, they have mainly exerted pressure when cotton strainers have been feeding on native hosts rather than in cropping situations.

The pest can be controlled by

  • Carbaryl
  • Lindane
  • BHC
  • Fenthion
  • Cotton dust

The pest in general can be controlled by;

Close season

  • Insecticide dusts
  • Complete sprays
  • Insecticide use
  • Implements used
  • Timing of application
  • Variations in pest incidence

 Summary

The order Hemiptera has different of families. Pests have piercing and sucking mouth parts. Insects undergo incomplete metamorphosis.  Early and heavy infestations of the crops can lead to significant yield losses

 

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