Mosquito Bug

Pests of Field Crops in Southern Africa

MOSQUITO BUG

(Hemiptera/Heteroptera: Miridae)

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Text Box: The mosquito bug is, as its name suggests, a small, slender flying bug but there the resemblance ends as it has very bright colouring. The most common species found is Helopeltis schoutedeni although several species occur. The adult bug is elongated, measuring 7-9 mm long and about 1.5 mm broad, with black head and long black, angled antennae, red or orange thorax and abdomen, and slender orange wings with dusky areas in their centres and at their tips. The legs are also orange and very slender. Despite these bright colours, the bugs are seldom seen, as they are particularly elusive, taking cover at the least disturbance. The eggs are curved and white, with two filaments of unequal length at one end. The nymphs are quite unlike the adults, being delicate cream-coloured creatures with red spots and bands, and a projecting vertical filament on the thorax. TOP

The mosquito bug has a long list of recorded hosts. Among these are cotton, pigeon pea, sweet potato, guava, avocado, mango, cashew and pecan nuts, paw-paw, granadilla, several garden plants such as begonia, fuchsia, zinnia, Brazilian pepper trees (Schinus braziliensis), Tibouchina trees, and many weed species.

Text Box: Both nymphs and adults cause damage when they suck the sap of the plant. Their toxic saliva, which is injected when feeding, causes the formation of brown areas of dead tissue, often resembling disease symptoms. Feeding in young green leaves results in distinctive angular spots bound by the leaf veins, and puckering – this is frequently seen in fuchsia, begonia, etc, at the growing points. On young stems, the damage is more extensive, resulting in black and deadened areas, and often death of the twigs, so that stunted growth of the branches occurs – this is seen particularly on Brazilian pepper trees, which may sometimes be severely affected. Feeding on fruits or cotton bolls causes the formation of shallow, circular depressions with a hardened area beneath, which eventually turn black. This dead tissue can no longer expand to accommodate growth, with the result that it splits away to form a scab. These scabs are very commonly seen on guava, mango and avocado, but while they are unsightly, they do not render the fruit completely inedible. If the population of mosquito bug is high, very young fruits can be extensively damaged, however, and may abort. TOP

Text Box: Eggs are laid individually in slits in the stem, petiole or leaf veins and their incubation period is one to two weeks. Between 30 and 60 eggs are laid per female, depending on temperature and host plant. The nymphal period is about three weeks, and there are five nymphal stages. Adults live for several weeks. Populations can maintain themselves with ease on alternate hosts when the cotton or other crop is dry, and several generations are probable each year, particularly in a garden situation. TOP

Text Box: Attack by Helopeltis spp. is very sporadic and the insects are seldom seen, as they are elusive and very mobile. Usually the damage is noticed long after it is done, such as is the case with scabs on subtropical fruits. If one is aware of the pests’ presence, through scouting or awareness from past seasons, plants can be protected by a single spray of a contact insecticide early in the fruiting period. For example, guavas should be sprayed when the fruits are very small and green, taking care to spray after the flowering period is over so as to avoid a kill of pollinators. For years, carbaryl has given good results, but other contact insecticides such as synthetic pyrethroids should do an equally good job. Systemic insecticides do not give good control, despite this pest’s sap-sucking habit. TOP

Helopeltis and damage on Fuschia.

Helopeltis damage.

Scabbing damage on mango fruit.