15 Jan 2017

The Ministry of Agriculture Development and Food Security has confirmed a new pest known as tomato leaf miner (Tuta absoluta) which affects  both greenhouse and open field tomato crops in North East district, Central, Chobe and North West of Botswana.

A press release from the ministry also states that by December last year, the pest had also reached Kgalagadi district.  

The release explains that the tomato leaf miner,   Tuta   absoluta,   which originated  in South America in the 80s, was first detected in Spain in 2006, has rapidly spread  across  the  Mediterranean region  and  has  now  reached  Southern Africa.

It also explains that crop damage from this pest can reach 100 per cent.  

Meanwhile, the release states that the pest comes from eggs which are oval-cylindrical, usually laid on the underside of leaves, on buds or on the calyxes of green fruit.    

They are cream-colored and very small, being about 0.2 mm in diameter and less than 0.4 mm on the longest axis.  

Larvae are white or cream in early instars, with a black head.  

As they grow older, they turn pink or green with a brown head.  

The prothoracic shield just behind the head has paler patches in later instars, though the exact markings are variable.    

There are no other distinctive markings. Larval identification can be made from leaf mines, as few other larva mine tomato leaves.  Pupae are brown, and less than 6 mm long.                  

The adult moths are small, with a body length of around 7mm.  They are a brown or silver color with black spots on the narrow wings.   The antennae are long, and the legs and palps are ringed with black and brown.

The release further explains that the Tuta absoluta can produce 10-12 generations per year with females laying up to 260 eggs in each generation with a total life cycle completed within 30-35 days.   

Adults are nocturnal and hide between leaves during the day time.   

Further, it says the larval period is the most damaging period, usually completed within 12-15 days.

However since the larvae can delay maturity as long as food sources are available, they may be active feeders for the entire crop cycle.

The pest attacks tomato leaves, stems, flowers, and fruits.   It also attacks potato,   eggplant   and   bean   crops.

Most feeding damage is done to the leaves and stems of tomatoes creating blotch leaf mines that are visible on both sides of the leaf.   

There can be several mines on a single leaf.   

The mines have dark frass (excrement) attacked if the infestation of Tuta absoluta is heavy, but even small amounts of damage mean that the fruit will not be suitable for market. Secondary   rot   can   occur   in   the wounds, rendering the fruit unfit for consumption. BOPA