PES­TI­CIDES

Garden News (UK) - - GARDEN OF THE WEEK -

Pes­ti­cides, specif­i­cally those used to kill plant pests such as in­sects and mites, is the group of gar­den chem­i­cals ex­pe­ri­enc­ing the greatest over­haul and change, with more prod­ucts con­tain­ing nat­u­ral or ‘or­ganic’ ac­tive in­gre­di­ents be­ing made avail­able.

Syn­thetic sys­temic pes­ti­cides

These broad-spec­trum, non­nat­u­ral sub­stances kill by be­ing ab­sorbed into plant tis­sues and in­gested by the or­gan­ism.

One of the most con­tro­ver­sial in re­cent years has been the race of broad-spec­trum sys­temic chem­i­cals called neon­i­coti­noids, or ‘neon­ics’, due to their dev­as­tat­ing ef­fects on the health of bees and bee pop­u­la­tions, through their paralysing ef­fect on in­sect cen­tral ner­vous sys­tems. Sup­ported by a size­able body of sci­en­tific anal­y­sis, the ef­fects were found to be detri­men­tal to bee and pol­li­na­tor health, even at low con­cen­tra­tions, through con­tin­ual in­ges­tion of con­tam­i­nated plant sub­stances, such as nec­tar and pollen.

As a con­se­quence, use of neonic chem­i­cals was se­verely re­stricted in 2013, mainly af­fect­ing agri­cul­ture and com­mer­cial hor­ti­cul­ture, but prod­ucts con­tain­ing im­i­da­clo­prid, pri­mar­ily to con­trol vine wee­vil, were with­drawn to gar­den­ers.

In April this year the with­drawal was made per­ma­nent, with many of the Provado range of prod­ucts from Bayer (SBM Life Sci­ence) con­tain­ing the neonic thi­a­clo­prid for con­trol­ling in­sects and vine wee­vil lar­vae now with­drawn.

Only ac­etamiprid, which is con­sid­ered to have lower bee tox­i­c­ity, now re­mains, used in prod­ucts such as Scotts Bug Clear Ul­tra for sprays, and Bug Clear Ul­tra Vine Wee­vil Killer as a compost drench.

Syn­thetic con­tact pes­ti­cides

These non-nat­u­ral, broad­spec­trum sub­stances kill on con­tact with the in­sect and are largely de­rived from chem­i­cally al­ter­ing nat­u­rally oc­cur­ring sub­stances, such as pyrethroids, from the flower pyrethrum.

They have low tox­i­c­ity to an­i­mals, but some can re­main ac­tive for many weeks, while oth­ers break down af­ter a few days. Some can be used on food plants.

● Deltamethrin can be used on or­na­men­tals and a wide range of food crops, and is found in Baby Bio House­plant Bug Killer, Provado Ul­ti­mate Fruit and Veg­etable Bug Killer and Spray­day Green­fly Killer, both from SBM Life Sci­ence. West­land Hor­ti­cul­ture’s Re­solva Bug Killer, con­tain­ing lamb­da­cy­halothrin, can also be used on or­na­men­tals and ed­i­bles, as can Py Bug Killer from Vi­tax, con­tain­ing cyper­me­thrin.

Or­ganic or nat­u­ral in­sec­ti­cides

The ac­tive in­gre­di­ents in these prod­ucts are de­rived from plant prod­ucts or other nat­u­rally oc­cur­ring sub­stances. They’re gen­er­ally safe to use on ed­i­ble crops, as well as or­na­men­tals, (but check la­bel for timings). They’re not per­sis­tent, so mul­ti­ple ap­pli­ca­tions may be re­quired.

While gen­er­ally not harm­ful to mam­mals and birds, they can harm aquatic or­gan­isms, such as fish and am­phib­ians.

Pyrethins, de­rived from the plant Tanace­tum cinerari­ifolium, will kill a wide range of in­sects and some beetle pests and are found in De­fend­ers Bug Killer and Bug Clear Gun for Fruit and Veg.

● Prod­ucts based on plant oils, largely pro­duced from rape and sun­flower seed, act by block­ing the breath­ing tubes (spir­a­cles) of in­sects. For­mu­la­tions in­clude Ori­gins Bug Con­trol and Bug Clear Fruit and Veg, while Vi­tax Or­ganic 2 in 1 Pest & Dis­ease Con­trol also con­tains fish oil, and can treat pow­dery mildew and black spot on roses.

● So­lu­tions con­tain­ing fatty acids or in­sec­ti­ci­dal soaps will help con­trol a wide range of suck­ing in­sects, es­pe­cially aphids, white­fly and red spi­der mite. Prod­ucts in­clude So­labiol Bug Free and Doff Green­fly & Black­fly Bug Killer. Sea­weed ex­tract is con­tained in Agralan White­fly Killer for use in green­houses.

Mol­lus­ci­cides

There are many types of prod­ucts avail­able to gar­den­ers to con­trol slugs and snails, in­clud­ing bi­o­log­i­cal con­trol us­ing eel­worms, and phys­i­cal bar­ri­ers and traps. The two main chem­i­cal con­trols are based on fer­ric phos­phate, which is ap­proved by or­ganic grow­ers, and met­alde­hyde, which isn’t, and usu­ally comes in the form of pel­leted blue­coloured bait. Prepa­ra­tions con­tain­ing fer­ric phos­phate in­clude Grow­ing Suc­cess Slug Killer and Neu­dorff Sluggo Slug & Snail Killer. Those con­tain­ing met­alde­hyde in­clude Ul­ti­mate Slug & Snail Killer and Eraza Slug and Snail Killer.

Plant oil-based pes­ti­cides such as Bug Clear Ul­tra can be used on fruit and veg

Be­fore us­ing chem­i­cals in the gar­den, such as slug pel­lets, find out what ef­fects they have on the en­vi­ron­ment first

Left, Ne­maslug con­tains eel­worms. Right, try a nat­u­ral in­sec­ti­cide on aphids

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