Calotropis (Calotrops procera) is a common weed in Katcho area (riverine belt) of District Khairpur. This weed plant, is locally known as the Akh.
It belongs to the Asclepiadaceae family which includes 280 genera and 2000 species of world wide distribution but most abundant in the sub-tropics and tropics, and rare in cold countries.
Calotropis yields a durable fibre useful for ropes, carpets, fishing nets and sewing thread. It is also used as a medicinal plant but here it is considered a useless weed.
However, a few Katcho area dwellers reported the use of floss, obtained from the seed, for stuffing purposes. The poisonous nature of this weed protects it from insect pests and animals.
It is a favourite food plant of a locust species locally known as the Akh Makri (calotnopis locust). The calotropis locust is not a true locust as it does not form swarms like that of the desert locust, the African migratory locust, the red locust, the Moroccan locust or the Italian locust.
The locusts exhibit swarming (mass migration of large bands), whereas, the grashoppers do not, although they may multiply rapidly and become pests of local importance.
Following the low rainfall in the riverine belt this year, a rapid increase in the population of calotropis locust took place and by mid July it was conspicuous and became the topic of discussion among the Katcho area dwellers. A survey undertaken by this scribe by the end of July indicated 20 to 50 locust (nymphs and adults) per bush of calotropis.
Calotropis weeds on hundreds of acre were almost completely denuded, following vigorous feeding of its leaves. Later some population of locusts were also observed from the denuded calotripis plants to the cotton crop standing in the vicinity. However, no damage to cotton crop was observed during the survey.
In the subsequent survey, the locust population was found at low ebb which may be due to the spraying of the cotton crop by the pesticides. By the end of August these had completely disappeared.
On inquiry it came to notice that the Akh locust became the victim of predatory birds, especially the Rosy pastors locally known as the “Wahyo” or tillear. According to the farmers of the Katcho area, (Sadi bello, of District Khairpur) the swarms of Wahy were seen attacking the locusts on bushes of calotropis.
The attacks continued till the locust population subsided to zero. The writer had to believe it because birds function as an important natural check on the increase of insect populations.
The destruction of locusts by birds continues not only when the former are at the peak of their periodical abundance, but even when their population is at a low ebb.
According to the Uvarov (1928), certain birds can play an effective part in the suppression of an outbreak of locusts, when it is already on decline. Hussain and Bhalla (1931) listed 35 species of birds, belonging to 19 families, attacking the locust in Punjab. Important species includes the common Indian crow, the Rosy pastor, common Myna and the northern grey partridge.
No doubt this July, the outbreak of calotropis locust was not of the economic importance for an ordinary dweller as it proved lethal for an unwanted weed plant.
The potential of the outbreak of this locust species could have been harnessed using the increased population as a test insect for locust control with the bio-pesticides by the Locust Control Division of the Federal Plant Protection Department, Karachi.
Whenever locusts invade, it is handled with the highly toxic insecticides including the banned ones. Persistent use of it may be lethal for the desert ecosystem as well as its biodiversity.
No efforts have been made to monitor the healthier environmental impact of locusticides used aerially or by ground equipments during or after anti-locust campaign.
Since research carried out over many years has shown that the Bio products based on spores of the entomopathogenic fungus Metarhizium anisopliae var acridium (Maa) are very effective against, and at the same time specific to locust, it is warranted that the Federal Plant Protection Department, responsible for controlling the desert locust, take the notice of these development.
Reportedly, the Biological Control Product Ltd of South Africa now produces the Green Muscle (GM) which demonstrated highly successful field trials in many African countries.
A similar product called the “Green Guard” (GG), which is based on Maa, is being produced in Australia, where it has been used successfully in controlling the indigenous locust species. An FAO expert commission has attested to the excellent efficacy and absolute harmlessness in environmental terms of both the products.
The importance of locust control with bioinceoticides may be viewed in the backdrop of the UN warning about locust plague which may hit Pakistan and India in the months ahead.
According to the UN locust control officer swarms of locusts sweeping through much of West Africa, may advance as far as Saudi Arabia or even Pakistan and India, depending on whether the creatures take root in Sudan.
Courtesy: The DAWN