MAN­AG­ING IN­SECT PESTS IN OR­GANIC VEG­ETABLE PRO­DUC­TION

Agriculture - - How-to - BY PIO A. JAVIER, PHD & TONY A. RO­DRIGUEZ

IN­SECT PESTS are a ma­jor hin­drance to prof­itable veg­etable pro­duc­tion, as these may cause more than a 50 per­cent re­duc­tion in yield. Dam­age caused by pests is ir­re­versible; the plants may not be able to re­cover from the re­sult­ing in­fec­tions to their shoots and other parts.

An im­por­tant first step in man­ag­ing in­sect pests is be­ing able to rec­og­nize and iden­tify those that at­tack veg­eta­bles. Farm­ers gen­er­ally find it dif­fi­cult to rec­og­nize the pests and the dam­age they cause, so they tend to im­me­di­ately spray in­sec­ti­cide upon notic­ing the pres­ence of in­sects with­out mon­i­tor­ing them.

The main phys­i­cal char­ac­ter­is­tic of in­sects is their hav­ing three body re­gions: the head, tho­rax, and ab­domen. Aside from this, in­sects have three pairs of legs in their adult stage, one or two pairs of wings, and a pair of an­ten­nae. In­sects un­dergo two gen­eral types of de­vel­op­ment: com­plete meta­mor­pho­sis from egg to larva (first to fifth in­star) to pupa and to adult, and in­com­plete meta­mor­pho­sis from egg to first in­star nymph up to the fifth in­star nymph to adult.

The two clas­si­fi­ca­tions of in­sects ¬¬¬are ac­cord­ing to their tax­o­nomic or­der and ac­cord­ing to their mouth parts, which clas­sify them as chew­ing (re­mov­ing pieces of plant tis­sue and eat­ing leaves), suck­ing (pierc­ing plant tis­sue and re­mov­ing plant sap), and bor­ing (get­ting into stalks or fruits and eat­ing plant tis­sue).

In­sects are suc­cess­ful in de­stroy­ing veg­eta­bles be­cause of the short time that it takes for them to de­velop (only a month from egg to adult), their abil­ity to pro­duce many off­spring. Many of them can fly and travel long dis­tances. They are small and dif­fi­cult to de­tect, and their pop­u­la­tion and the dam­age they cause are dif­fi­cult to con­trol. Fi­nally, they have a wide range of hosts as they feed on a wide va­ri­ety of crops.

COM­MON IN­SECT PESTS AT­TACK­ING MA­JOR VEG­ETABLE CROPS

For egg­plant, this is the fruit and shoot borer, the com­mon cut­worm, the corn semi-looper, white­fly, leaf­hop­per, and lady bee­tle. A sin­gle adult borer lays up to 121 eggs at night; these hatch in four to six days. The lar­vae bore into and feed on the egg­plant shoots, flow­ers, and fruits, with the to­tal lar­val pe­riod of about 15 days with six in­stars, af­ter which the ma­ture larva spins a leath­ery co­coon within the plant. Pu­pa­tion takes from 9.44 to 11.5 days. The male adults live for four days; the fe­male, for 7.5 days. Borer dam­age causes egg­plant flow­ers to fall, with sur­viv­ing ones de­vel­op­ing into small and ir­reg­u­larly-shaped fruit. In­fested shoots wilt and yield re­duc­tion can be from 20 to 80 per­cent. The cut­worm, on the other hand, feeds on the leaves and outer por­tions of fruit.

For tomato, these are the tomato fruit worm, white­fly, corn semilooper, com­mon cut­worm, leaf­hop­per, lady bee­tle, and leafminer. The fruit worm bores into the peti­oles, flower buds and flow­ers, and fruits, which even­tu­ally fall off. Both the nymphs and adults of the white­fly suck plant sap and trans­mit the Tomato Leaf-Curl Virus.

For bras­sica or cab­bage fam­ily veg­eta­bles, there are the di­a­mond­back moth (DBM), cab­bage moth, com­mon cut­worm, cab­bage web­worm, bee­tle, and aphids (Aphis gossypii Glover). DBM dam­age ap­pears as ir­reg­u­larly chewed patches in the leaves with their veins and up­per epi­der­mis still in­tact. Cab­bage moth larva feed on leaves, of­ten re­sult­ing in the non-for­ma­tion of heads and leaf per­fo­ra­tions in non-head-form­ing Bras­si­cas.

For legumes, these are the bean­fly, aphids, leaf­hop­per, cut­worm, bean pod borer, and ear­worm. Plants in­fected by aphids (Aphis crac­civora Koch) stop grow­ing, curl, crum­ple, and lose color. The sooty mold that grows on the in­sects’ ex­cre­tions cov­ers the leaves and in­ter­feres with the plants’ pho­to­syn­thetic ac­tiv­i­ties. The bean pod borer’s new­ly­hatched cater­pil­lar feeds on the flower buds whose un­con­sumed outer petals sub­se­quently dry up.

For cu­cur­bits, there is the squash bee­tle, melon worm, aphids (Aphis gossypii Glover), and fruit fly. Squash bee­tle grubs bore into the roots and plant por­tions close to the ground and feed on their tis­sues. The adult bee­tle feeds on the epi­der­mis of the leaves and flow­ers, leav­ing be­hind what look like shred­ded leaves. Melon fruit fly mag­gots feed on the stems and fruits, caus­ing stem and fruit rot. Se­vere in­fes­ta­tion re­sults in many fruits drop­ping or im­ma­ture ones de­cay­ing.

OR­GANIC PEST MAN­AGE­MENT (OPM) OPM is the in­tel­li­gent ma­nip­u­la­tion of the pest pop­u­la­tion us­ing a com­bi­na­tion of tech­niques in cul­tural prac­tices, le­gal con­trol, and phys­i­cal and other meth­ods in con­sid­er­a­tion of nat­u­ral reg­u­la­tory fac­tors to re­duce eco­nomic dam­age. It in­volves a se­ries of man­age­ment de­ci­sions as to the right man­ner for the con­trol or sup­pres­sion mea­sures.

The tech­niques to be used are: en­hanc­ing the pres­ence of bi­o­log­i­cal con­trol agents; the use of re­sis­tant crop va­ri­eties; the ap­pli­ca­tion of com­pat­i­ble cul­tural farm prac­tices; and the need­based ap­pli­ca­tion of botan­i­cal in­sec­ti­cides.

Bi­o­log­i­cal con­trol is the use of liv­ing or­gan­isms such as par­a­sitoids ( Tri­chogramma, Di­adegma semi­clausum, Cote­sia plutel­lae, Snel­le­nius mani­lae, Te­leno­mus, Trathala flavoor­bitalis, Opius long­i­cau­da­tus, etc.); preda­tors (ear­wigs, stink bugs, Coc­cinel­lid bee­tles, flower bugs, lacewings, etc.); and mi­cro­bial pathogens like nu­clear poly­he­dro­sis Virus (NPV),

Beave­ria bassiana, Bacil­lus thuringien­sis, etc. to sup­press pest pop­u­la­tions.

Par­a­sitoids, which are par­a­sitic dur­ing their im­ma­ture stage, at­tack the eggs or lar­vae of in­sect pests. They need a sin­gle host to com­plete their life cy­cle, al­ways kill their host, and are free-liv­ing as adults.

In us­ing Tri­chogramma for tomato, re­lease 50 T. chilo­nis cards per hectare twice a week two to three weeks af­ter trans­plant­ing (WAT), and re­peat four times at weekly in­ter­vals at 25 cards per hectare. For egg­plant, start­ing at two to three WAT, re­lease 25 T. chilo­nis cards per hectare twice and re­peat four times at weekly in­ter­vals.

The par­a­sitoids D. semi­clausum and C. plutel­lae ef­fec­tively con­trol DBM lar­vae. The com­mon cut­worm’s eggs are par­a­sitized by Te­leno­mus, its lar­vae by S. mani­lae, or preyed on by ear­wigs or NPV. T. flavoor­bitalis, which is all-fe­male and re­pro­duces with­out males, has po­ten­tial as a par­a­sitoid against the egg­plant fruit and shoot borer, while O. long­i­cau­da­tus adults lay their eggs on fruit fly lar­vae.

Preda­tors, which are usu­ally big­ger than their prey, re­quire sev­eral vic­tims to com­plete their life cy­cle. Ear­wigs (chiefly Eu­borel­lia an­nu­lata and E. philip­pinen­sis), which are elon­gated and flat­tened in­sects whose mo­bile ab­domens ex­tend into a pair of for­ceps, feed on the egg masses, young lar­vae, and pu­pae of Lepi­doptera, Coleoptera, and Diptera in­sect pests. More ac­tive at night, ear­wigs also prey on leaf­hop­pers, aphids, and other soft-bod­ied in­sects. Stink bugs are preda­tors of cut­worms and the lar­vae of other lep­i­dopter­ous pests, as Coc­cinel­lid bee­tles prey on the in­star lar­vae of those pests, and flower bugs on those in­sects’ eggs and early in­star lar­vae.

Mass-rear E. an­nu­lata in plas­tic trays for bi­o­log­i­cal con­trol pur­poses. Place 2.5 to three kilo­grams of a ster­il­ized mix­ture of three parts soil and one part sand in each tray, wet the medium to 27 to 30 per­cent mois­ture con­tent, and main­tain this through­out the rear­ing pe­riod. Re­lease 36 fe­male and 12 adult ear­wigs in each tray and feed the in­sects weekly with 10 to 20 grams of fish­meal and a mix­ture of 20 grams each of corn­cobs and dog food.

Re­lease the adult E. an­nu­lata in an egg­plant field with mulched plots two to three WAT. Place 2,000 sec­ond to fourth in­star nymphs in each plas­tic tray with moist soil among the plants. Re­lease 20,000 in­di­vid­ual ear­wigs per hectare at three WAT and another 20,000 at four WAT.

Mi­cro­bial pathogens like the NPVs are highly spe­cific in­sect pathogens used as mi­cro­bial pes­ti­cides. Their in­fec­tion route is through in­ges­tion and they mul­ti­ply in in­ter­nal or­gan tis­sues, killing the host in­sects. They do not af­fect mam­mals, birds, fish, and non-tar­get in­sects.

Another mi­cro­bial pathogen is Bacil­lus thuringien­sis (Bt), a bac­terium iso­lated from the soil that can pro­duce tox­ins for con­trol­ling spe­cific in­sect pests. In­ges­tion by the in­sects se­verely af­fect their di­ges­tive sys­tem and lead to star­va­tion and death. The Univer­sity of the Philip­pines-Los Banos’ (UPLB) biotech depart­ment pro­duces a com­mer­cial Bt for­mu­la­tion called Bac­trolep which is ef­fec­tive against the DBM in bras­si­cas and the Asian corn borer. It’s spe­cific and kills only its tar­get pests.

PLANT EX­TRACTS AGAINST IN­SECT PESTS

Plant ex­tracts have been used world­wide as botan­i­cal pes­ti­cides since the 1940s. Lo­cal plants used for that pur­pose in­clude lemon­grass, ser­pentina, oregano, marigold, langkauas, luyang di­law, gar­lic, black pep­per, cit­ronella, sili, chichir­ica, and makahiya. Whole plants, stems, leaves, roots, flow­ers, fruits, pods, seeds, sap, bark, pods, bulbs, and tu­bers are used. Ex­trac­tion pro­cesses use wa­ter, vine­gar and wine. Nat­u­ral­ly­oc­cur­ring tox­ins in the plant parts are ef­fec­tive against pests, although many re­ports on these have not been prop­erly doc­u­mented, ex­trac­tion pro­ce­dures are not valid, proper ex­po­sure meth­ods are not fol­lowed, and tar­get in­sect age is not spec­i­fied.

Many plant ex­tracts are less toxic to mam­mals than syn­thetic in­sec­ti­cides, although sev­eral are harm­ful to fish and other wildlife. Ex­tracts tend to break down fast in the en­vi­ron­ment so they need fre­quent ap­pli­ca­tion.

Fresh juice ex­tracts can be ob­tained from suc­cu­lent plants like luyang di­law (rhi­zomes), oregano (stems and leaves), pan­sit­pan­si­tan, and ka­man­tigue. Wash the parts thor­oughly be­fore ex­tract­ing their juice.

Ex­trac­tion with a blender is also doable for non-suc­cu­lent plants like langkauas (rhi­zomes), mak­abuhay (stems), and ser­pentina and lan­tana (leaves). Chop 500 grams of the ma­te­rial and grind in the blender. Soak the blended ma­te­rial overnight in a liter of wa­ter then press and fil­ter in the morn­ing for the stock so­lu­tion. Re­frig­er­ate the so­lu­tion when not us­ing it.

In pre­par­ing ex­tracts of oregano stems and leaves, and luyang di­law and langkauas rhi­zomes, chop or mac­er­ate two ki­los of the ma­te­ri­als and soak in four liters of wa­ter with one-half bar crushed Perla soap for 24 hours for the rhi­zomes and 72 hours for oregano. Af­ter the re­quired time, fil­ter the so­lu­tion and place in a 16-liter knap­sack sprayer. Fur­ther mac­er­ate the residues in about 11 liters of wa­ter and add the so­lu­tion to the one in the sprayer. Spray to the point of run-off in the af­ter­noon, re­peat­ing this ev­ery seven to 10 days, depend­ing on the pest pop­u­la­tion. A hectare gen­er­ally re­quires 10 sprayer loads.

Eval­u­ate the ex­tract’s con­tact tox­i­c­ity by top­i­cal ap­pli­ca­tion or leaf spray­ing. Record mor­tal­ity data at 24 and 48 hours af­ter treat­ment. An ef­fec­tive anti-feedant ex­tract gives in­sects the op­por­tu­nity to feed on the treated plants but grad­u­ally re­duce their in­take un­til they starve to death. Re­pel­lants, on the other hand, drive away the in­sects af­ter ex­po­sure even with­out feed­ing on the treated plant parts. Feed­ing may also ex­pose the in­sects to growth-in­hibit­ing ef­fects when they bear ab­nor­mal pu­pae and adults.

NON-PES­TI­CIDE CON­TROL METH­ODS

Cul­tural con­trol tech­niques are farm oper­a­tions that are fa­vor­able to crop pro­duc­tion but not for pests. One is thor­ough land prepa­ra­tion in plow­ing and har­row­ing for ex­pos­ing pest and dis­ease in­ocu­lum and re­duc­ing weeds. Another is syn­chro­nized plant­ing so that the pest-sus­cep­ti­ble crop stage does not co­in­cide with the peak of pest in­fes­ta­tion.

Rou­tine san­i­ta­tion tasks like re­mov­ing de­bris and old leaves rids the farm of pests’ breed­ing sites and food sources, while in­ter­crop­ping or mul­ti­ple crop­ping, such as with mongo whose flow­ers pro­vide nec­tar to ben­e­fi­cial in­sects, are also help­ful.

The use of pest-re­sis­tant veg­etable va­ri­eties is another non­pes­ti­cide con­trol method. Se­lec­tive weed­ing also helps in that some wild plants serve as a refuge for spi­ders and other preda­tory in­sects. Me­chan­i­cal or phys­i­cal con­trol is also ad­vis­able, such as hand-pick­ing when only a few plants are in­volved, and bag­ging fruits with plas­tic, news­pa­per, or net to pre­vent flies from lay­ing eggs there—though this is a method re­quir­ing proper tim­ing.

Plant­ing trap crops is another con­trol method. A trap plant should be more pre­ferred by pests over the main veg­etable crop and must be planted ahead of it. Kadyos and mus­tasa-mus­tasa­han are ex­am­ples of trap crops. Plant­ing re­pel­lent herbs around veg­eta­bles is another method.

Another means of con­trol is the use of traps, such as with sex pheromones which fe­male in­sects se­crete. Used to at­tract male fruit flies in cu­cur­bits and fruit trees, the traps can greatly re­duce fer­til­iza­tion in the fe­male pests and re­sult in very few off­spring. Im­pro­vised traps like plas­tic bot­tles with basil leaves that at­tract fruit flies in­side and holes through which the in­sects can en­ter are also ef­fec­tive.

Semi-ul­tra­vi­o­let lamps have been found to trap the adults of pests im­me­di­ately af­ter these emerge and pre­vent them from lay­ing eggs, thus greatly re­duce pest pop­u­la­tion.

Although many or­ganic farm­ers now use botan­i­cal pes­ti­cides, the use of par­a­sites, preda­tors, and mi­cro-or­gan­isms in the bi­o­log­i­cal con­trol of in­sect pests in gen­eral is not yet pop­u­lar with farm­ers. The rea­sons for this are the nat­u­ral en­e­mies are highly spe­cific and can­not con­trol the wide ar­ray of pests that at­tack crops, and the dif­fi­culty of mass-pro­duc­ing bio­con agents.

The en­hanced use of bio-pes­ti­cides and bio­con agents re­quires vil­lage-level mass pro­duc­tion and the ag­gres­sive dis­sem­i­na­tion of the tech­nolo­gies through or­ga­nized pest man­age­ment pro­grams for or­ganic veg­etable grow­ers.

This ar­ti­cle on how or­ganic veg­etable grow­ers can man­age in­sect pests in their gar­dens or farms was one of the lec­tures de­liv­ered dur­ing the well-at­tended Ur­ban Agri­cul­ture Trade Show held re­cently by the Manila Bul­letin’s Agri­cul­ture Monthly Mag­a­zine at the Rock­well Cen­ter in Makati City. Dr. Pio Javier is a re­search pro­fes­sor with the Crop Pro­tec­tion Clus­ter of the Univer­sity of the Philip­pines at Los Baños (UPLB) Col­lege of Agri­cul­ture.

Dr. Pio Javier de­liv­ered his lec­ture on the sec­ond day of this mag­a­zine’s re­cent Ur­ban Agri­cul­ture trade show at the Rock­well Cen­ter in Makati City.

The ear­wig Eu­borel­li­aan­nu­lata is a preda­tor that feeds on the egg masses, young lar­vae and pu­pae of Lepi­doptera, Coleoptera and Diptera inset pests, as well as on leaf­hop­pers, aphids and other sodt-bod­ied in­sects.

Lar­vae of the fruit and shoot borer and the com­mon cut­worm in­flict heavy dam­age on egg­plants.

The tomato fruit worm bores into the peti­oles, flower buds and flow­ers, and fruits of tomato plants.

Other preda­tors of in­sect pests are Coc­cinelid bee­tles that prey on the in­star lar­vae of lep­i­dopter­ous in­sects, and stink bugs that feed on the lar­vae of those in­sects and cut­worms.

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