Board warns farm­ers of new de­struc­tive pest

Chronicle (Zimbabwe) - - Business - Con­rad Mwanawashe Harare Bureau

THE To­bacco Re­search Board has warned of a threat posed by Tuta ab­so­luta, a new in­va­sive and highly de­struc­tive pest, to the to­bacco in­dus­try, one of Zim­babwe’s lead­ing for­eign cur­rency earn­ers.

This year alone, Zim­babwe earned $670 mil­lion from to­bacco ex­ports and this fig­ure could be com­pro­mised if the pest is not con­trolled. In an alert, TRB said Tuta ab­so­luta, orig­i­nat­ing from South Amer­ica re­cently in­vaded Zim­babwe and cur­rent re­ports in­di­cate high lev­els of dam­age in tomato. The tomato is the pre­ferred host of the pest, both in its na­tive and in­vaded ter­ri­to­ries.

The pest is fast spread­ing in Zim­babwe and has al­ready caused heavy losses in tomato. How­ever, in the ab­sence of the pri­mary host, Tuta ab­so­luta is known to at­tack closely re­lated crops such as to­bacco, potato, pep­per, egg­plant and solana­ceous weeds. In ex­treme cases it has been re­ported on cab­bage, kales and other veg­eta­bles of the Bras­sica fam­ily. Fur­ther­more, TRB said what makes the pest a real but silent threat, is its close re­sem­blance to the or­di­nary leafminer cur­rently known in the to­bacco agrosys­tem. The adult moth lays eggs on the tomato plant leaves, stems or fruit. When eggs hatch, lar­vae bur­row into the leaf lam­ina caus­ing loss of pho­to­syn­thetic area thus re­sult­ing in large blis­ter like por­tions of merged tun­nels or mines.

The lar­vae also gnaw away stems and leaf stalks and bur­row into fruits caus­ing ex­ten­sive rot­ting.

“Tuta ab­so­luta has a high propen­sity of de­vel­op­ing re­sis­tance to var­i­ous in­sec­ti­cides that are known to ef­fec­tively con­trol other leafmin­ers. Cur­rently in Zim­babwe, no tests have been con­ducted to es­tab­lish ef­fec­tive in­sec­ti­cides that can be used to con­trol the pest,” the board said.

Grow­ers who have al­ready en­coun­tered this pest on tomato are en­cour­aged to ex­er­cise ex­treme re­straint and cau­tion in us­ing in­sec­ti­cides. There are in­ci­dences in Bin­dura where Tuta ab­so­luta pop­u­la­tions are al­ready show­ing in­creased tol­er­ance to in­sec­ti­cides as a re­sult of unco-or­di­nated con­trol pro­grammes in­volv­ing spray­ing var­i­ous pes­ti­cides that have not been tested.

In other parts of the world, grow­ers have man­aged to de­lay the on­set of in­sec­ti­cide re­sis­tance by us­ing a com­bi­na­tion of spe­cific pes­ti­cides with dif­fer­ent modes of ac­tion, pheromone traps, bi­o­log­i­cal con­trol and cul­tural prac­tices.

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