Ants, a threat for crop pollination
Pollination is an important valued ecosystem service in the world. It is worth of several trillions of US dollars. Both the agricultural crops and wild plants require pollination from the animals, such as bees, bats, birds and so on.
The world, as per the recent report of International Panel for Biodiversity and Ecosystem Services reported, is experiencing the pollinator decline and the yield of pollinator-dependent crops. Several factors - increased use of pesticides, honey bee colony collapse syndrome and diseases, decline of flowers, land-use change, invasive bees and so on - have been proposed for this global phenomenon. A recent study published in Scientific Reports published by the Nature group by the researchers led by Dr. Sinu in Central University of Kerala suggests that the flower-visiting ants can be a threat for pollinators and pollination process in the plants in tropics.
Dr. Sinu of CU-Kerala and his team of researchers, Anjana Unni, Rajesh T.P., Prashanth Ballullaya U. and an academy summer fellow to his lab, Dr. Sajad Mir of Sher e Kashmir University showed that the yield of pumpkin crop can go down due ant colonization in pumpkin flowers.
They have studied this in the small-scale agricultural farms of Kasaragod and Kannur districts. Pumpkin, because having male and female flowers borne on different nodes, needs visits of honey bees - the major pollinator of the crop - on both the types of flowers to ensure pollination. They, therefore, watched both the sets of flowers immediately after their opening for the visits of pollinators and ants.
They found that the female flowers, because produce relative good amount of good quality nectar, received more visits of both the pollinators and the ants. Because the flowers resecrete nectar throughout the flower opening period (about 6 houss) the ants hardly leave the flowers once colonized.
They recorded 10 species of both the native and a globally notorious invasive ant (Yellow Crazy ant) on the flowers. Irrespective of the origin of ant species, the flowers when occupied by the ants were deserted by the bees. Those ventured to linger on or land on the flowers were either chased by the ants or preyed upon. However, depends on the ant species, their numbers can be varied between 1 and over 100s. For instance the Yellow Crazy ant (Anoplolepis gracilipes) - the invasive ant species - is normally seen over 50 numbers on any plant. They not only seen in many numbers in flowers, covered on almost all flowers bloomed in the field. The researchers recorded no fruit set in ant-infested flowers, a major setback for the farmers.
Although ants may sometimes function as a pollinator of flowers, in pumpkin, it is unlikely that they pollinate flowers, Sinu said. Pumpkin is monoecious - a situation when male and female flowers are on two separate nodes. Also, they are male dominated in plants and in fields. Over 90% of the flowers produced by a plant belong to male. Ants, are unlikely to communte among flowers. Their dependence on male flowers for pollen or nectar is very less.
The farmers grow pumpkin in orchards but mostly as a rotational crop in paddy lands after paddy season. They are good habitats for ants because of organic wastes and soil characters. The farmers should be utmost care to keep their farms clean to avoid ants in their farmlands. We have restrictions for using pesticides, particularly in Kasaragod. Also, the pesticides that we use for targeting ants can also stop the bees on flowers, so must be avoided, Dr. Sinu emphasized.