COVER PHOTO: Larva of Erinnyis ello being preyed on by Polistes sp.

CIA T i; a nonprofit organizutiuu de> ut<1d tu th,• agricultural and economic development of the iowland tropics. The Government of Columbia ¡>ru' id es support as hust country for CIA T and furnishes a 522· hectare farm near Cali for UA1\ h•·au4uartcr>. In addition. the Fundación para la Educación Superior (FES) makes available tu (.JA 1 the lll-4-hl'(tare substation uf Quilichao, situated near Santander de Quilichao, Departamento dd ( au(a. tullalwrati•·e work with the Instituto Colombiano Agropecuario (ICA) is carried out on se-eral uf it> c.,pcriutcntal stations a nd similar work is done with national agricultural agencies in othcr Lat111 Antcrican cuuntries. ('(A T is financcd h} a number of donors represented in the Con~ultati' e(, toup fur lntcrnational A¡:ricultural Research ( CGIA R ). During 1977 these donors were the Unitcd S t a tt ~ A~cll() for lntcrnational Development (\ ~A JO ), the Rockefeller Foundation, the Ford ~ oundaltvn. lhc \\'.h. . Kellogj! f oundatinn, the Canadian lnternational Development Agenc} (CIDA¡. thc llltcrttatitJJIJI Uank fc;H Rcco_nstruction and Oevclopment (IBRD) through thc lnternational Ot,dupmcnt A»ucialiun (lif\ )/th_~ ~~~~American Ocvelopment Bank (IDB) and the governments of Au,tralta, lhl~ium . illl' l· cdcral Republic of Germany. Japan. the Nctherlands, Switurland and the Lnit~d Kut~d u n1. lu auuitiun, 'pccial project funds are ~upplied b y ,·arious of the aforementioned entitie~ plu> thc I11Lcruatiuual U e• dop,ncnl llesearch ( entre (! DR (') uf Ca nada and the United Nations Oevelopmcm Pru ~•antn,.·t l .'\UI'¡.

This publication was financed b) th• (assa,·a lnformation Center al CIAT, a special pruject funlletl juintly by JDRC (Cassava Information P roject - Ph~• ll) and CL\ r's core budget. 1 7 Series 09EC-2 November, 197o

CASSAV A PESTS AND THEIR CONTROL

Anthony ,Bellotti Aart van Schoonhoven

CCM~lJ Edited by BlBL \0 EC Trudy Brekelbaum 551l&c

CASSAVA INFORMATION CENTER- CIAT Contents

lntroduction 5 The host plant 6 Distribution of pests 6 Crop losses due to insects and mites 6 Mites and insects attacking foliage 9 Mi tes 9 Thrips 14 Cassava hornworm 17 Whiteflies 21 Leaf-cutter ants 22 G rasshoppers 25 Gall midges 26 Cassava lace bug 26 lnsects attacking stems 29 Stemborers 29 Fruit flies 33 Shoot flies 34 Scale insects 37 Mealybugs 41 lnsects that attack roots. cuttings and seedlings 45 Grubs 45 Cutworms 46 Termites 46 Crickets 49 Storage pests of dried cassava 49 Crop protection 50 The role of different control methods 53 The status of cassava entomological research 55 Literature cited 57 Appendix 1ndices for classifying pest damage 65 The cassava mite and insect complex 69 Cassava pests and their control* Anthony Bellotti Aart van Schoonhovenu

1ntr oduction

Cassava ( Manihot esculenta). a major energy source for 300 to 500 million people, is grown throughout the tropical regions of thc world. lt is cultivated mainly in developing countries on small farms with little t cchnology. As a result. it has received limited attention from scientists and tcchnologists. FAO estimates for 1977 indicate an annual global production of 105 million tons on 11 million hectarcs. of which at lcast 55 mili ion are consumed by humans. Although cassava is now cultivated in sorne 90 countries. 80 pcrcent ofthc world's production comes from only 10; the six leading producers are Brazil (31%), Indonesia, Zaire, Nigeria, Thailand and 1ndia (98). 1n many parts of thc world, especially Wcst A frica, cassava appears to be the most economical. lowest risk subsistcnce crop for the small farmer.

Thc increasing world population and the limited availability of energy has prompted a recent surge of interest in cassava, not only for traditional uses as a human food and for specialized starches including tapioca but also for animal feedstuffs and industrial uses (65). There is an cxcellent potcntial for increasing both yicld and arca under cultivation. Two international ccnlers for tropical agriculture. one in Colombia (Centro Internacional de Agricultura Tropical, CIAT) and another in Nigeria ( 1nternationall nstitute ofTropical Agriculture, liTA), carry out cxtcnsive research on cassava in addition to other tropical crops (98). Emphasis is placed on dcveloping high-yiclding germplasm for low-input conditions. Present world cassava yiclds undcr small-farm conditions average only 5 to 15 t f ha. Experimental yields of 55 t in Colombia (27) and 70 t/ ha elsewhere (97) ha ve been obtained. Commercial yields with low input in Colombia ha ve cxceeded 40 t / ha. Thcse figures indica te that undoubtedly there are severa! fa ctors limiting production undcr farm conditions, one of which is pests.

1t has frcquently becn reported that cassava is gencrally free of arthropod pests; however, prcsenl rescarch at C IAT and othcr centers rcveals that mite and insect damage does limit cassava production; e.g .. the recent introduction into A frica and the conscquent epidemic of the green mitc A1ononychellus tanaioa has caused serious crop losses (86, 104).

Cassava pcsts represen! a wide range of arthropods: approximately 200 species have been rccorded. Although many are minor pests. causing little or no economic losses, severa! must be classified as major pests. These include mites. thrips, stemborers. hornworms. whiteflies and scale insects.

Atmd~ed \cnwn appe:u(·d ongmally in lhc Annual Rc\itw of Fntomolog)' 23:39-67. 1978 1 ntornolog•:,t!ll. CIA f. Cah. Colomh1a

5 What little information is available on this subjecl- scattered in numerous journals and monographs- has been collected and made available to researchers through CIAT's Cassava lnformation Center. There is a paucity of data on cassava pest biology, ecology, dislribution, seasonal occurrence and economic damage, often resulting in confusion as lo iden1ifica1ion, laxonomic classification, delermination of synonyms and effective control measures. An attempl has been made to galher informalion on lhese pests with recent observation~ by th..: authors, whose experience has been mainly in Latín America. The host plant

Manihot esculenta, a member ofthe Euphorbiaceae, is a perennial shrub that originated in the Americas; it was la ter taken to Africa and more recently introduced into Asia. Common names include mandioca, yuca, manioc and tapioca. Because of the different levels of cyanogenic glycosides it conlains in the roots, it has often been classified into "sweet" and "bitter" varieties.

Leaves are formed at active apices and consist of an elongated petiole anda palma te leaf blade. The plant exhibits apical dominance, producing a single stcm; the petioles are borne on raised structures, giving the slem a characlerislic nobby appearance. When the main apex becomcs reproductive. apical dominance is broken; and two, three, or four axillary buds immediately below the reproductive slruclure become active and branching occurs. The roots accumulate carbohydrales in the parenchyma lo form swollen storage organs. Depending on ecological conditions, lhe planl is cultivaled from 8 to 24 months. Although the plant can be grown from seed, it is usually reproduced vegetatively for commercial purposes by planting stem cuttings. Cassava is grown commercially at altitudes between sea leve! and 2000 meters.

Distribution of pests

The greatest diversity of insects reported attacking cassava is from the Amcricas. Representatives of the 17 general groups of pests described in this review are f ound in the Americas, 12 are reported from A frica. and only 5 are from Asia. U ndoubtedly, pesl distribulion is more widely dispersed than the literalure indicates.

Mites. whiteflies, whitegrubs. scales and termiles are reported from all major cassava-growing areas. The green mite Mononychellus tanajoa is reported only from the Americas and ccrtain parts of Africa ( 105). whereas the lwo-spotted spider mite Tetranychus urticae (T 1elariw) is reported worldwide. The white scale Aonidomytilus albus is reported from Asia. Africa and thc Americas whercas severa! other scale species are more localized. White grubs are reponed damaging cassava in severa! regions. but no single species appears universal. The cassava hornworm (Erinnyis ello), shoot flies, fruit flies, lace bugs (VatiKa manihotae) and gall midgcs are rcported only from the Americas. Stemborers. thrips. mealybugs and leaf-cutter ant~ are reported from the Amcricas and Africa. Grasshoppcrs are rcporled as a major pest only in Africa. Cutworms and crickets are found worldwidc but have nol been reponed as attacking cassava in all arcas.

lt appcars that lhc pest complex varíes greatly overthe main cassava-growing arcas; therctorc. careful quaranline measures should be employed to preven! their introduction into uninte~tcd arcas. Crop losses due to insects and mites Insects can cause damagc to cassava by reducing photosynthetic arca. which results in} 1cld reductions: by attacking stems. which weakens the plant and inhibils nutricnt transpon: and by

6 MITES

Oamage b) ¡\4onom ch t>llus tanaJoa (~ la nt un the righ t ) MITES

~r>rrt' allac~ h) .11. tonaioa attack i ng planting material. which reduces germination. Those mi tes and insects that attack the stcm a lso b sen the 4uantity and quality of planting material ta ken from these plants. thus affccting product ion. Soil-borne insects attack cuttings. causing wounds o r boring boles th ro ugh wh ich soil -borne pat hogens can en ter; thcy m ay al so complctely dest ro y t he epidermis and or hud ~ of the cuttings. Othcrs cut thc roots and 1or shoots shortly aftcr cmcrgcncc. Sorne insccts are vcctors of diseases as wcll. lndications are that pests such as miles. thrips. whitcflies,scalcs. mealybugs. lace bugs and ~ t c m horcrs. which attack the plant over a prolongcd period. will reduce yield more than those that dcfoliatc or damage plant parts for a brief period; e.g .. hornworms. fruit flies. shoot flies a nd lcaf-cuttcr ants. This is bccausc the cassava plant appcars able to recover from thc latter typc of damagc under fa vorable environmcntal conditio ns. with rainfall and soil fertility bcing critica! factors. Cassava is often grown in regions with prolonged dry seasons and infertile soil s. Thcsc a dditional factors o f water stress and poor fe rtility will compound damage caused by mi tes. thrip ·. lace bugs and scales,whose populations tend to increase during dry periods. M nst of·thc litcraturc reviewed did not include good cconomic loss data. When quantitativc figu re~ wcrc available. they are prescnted in the tcxt for each insect group.

Mites and insects attacking foliage Mites Rccent rescarch indica tes that mi tes are one of the most serious cassava pests througho ut thc \\ o rld . ;\ cumplcx of 22 species of spider mi tes. all helongi ng to the family Tet ranychidae. ha ve hccn idcntificd as fccding on cassava. The criteria used for identifying these mites and thcir taxonomic dcscription have been rcviewed by F lechtmann (49). The more important sp ccie ~ ol thc genera Tetranychus. Mononychellus and 0/if{onychus are shown in Table l.

Thc two species of greatest economic conscquence appear to be M. tanajoa and T unicae (T telarius). T urticae is found throughout ca ssava-growing regions of the world and is reponed to cause seri ous losses in parts of As ia ( 117) whcreas M. tanajoa is native to the Americas ( 1ó). lt was possibly introduced into A frica around 1970(86. 87) but m ay ha ve been present earlicr( 106) and has sprcad 4tlickly beca use of favorable environmental conditions ( 104, 106). 7: urtime has a wide host ra nge. whereas both the M. tanajoa and 0 /igonychus peruvianus miles a ppear limitcd to Ma nihot spp. but may attack other Euphorbiaceae. O. peruvianus has been identillcd only in the Americas (49) but O. gossypii has been fo und in Africa as well.

Yicld los ses as a res ult of mi tes are considera ble. Nyiira ( 106) reports yield losses as high a~ 4ó perccnt ca u sed by M. tanajoa in experimental pl ots in Uganda. Studies in Venezuela (E. Do reste. personal communication) place losses from M. tana;oa in the 15 t o 20% range. Field experiments al C I/\T ( 30) involving a complex of four mi te species (M. tana;oa, M. mcgregori. 7: unicueand O. peruviunus) rcsulted in 20 to 53% loss. depending u pon plant age and the duration of thc attack.

Damage The Mononychellus mite is usua lly found around the growing points of plants, on buds, young !caves and stems: the lower part of the plant is less affected. U po n emerging. !caves are marked with yellow spots, lose their normal green color. develop a mottled. bronzed. mosaiclike appearance a nd bccome deformed . Under severc attack. pla nt growth is stunted. shoots lose thei r grecn color and stems become scarified. first turning rough and brown and eventually presenting dieback. S tems and leaves necrose progressively from top to bottom (29. 106). 9 Table l. Importan! spec:ies of the cassava mite complex.

Species Synonyms Reported from Referen~:es

Mononyche/lus tanajoa Tetranychus tanajoa S. America 27, 40 Mononychus tanajoa E. Africa 86-87, 104

M. caribbeatrae T. caribbeanae S. America 11 5 Eotetranychus caribbeanae Caribbean 111 Mononychus caribbeanae Caribbean 111

M. planki T. pianki S. America 111 E. planki S. America 4

M. bondari Mononychus bondari Brazil 87

M. chaemostetosus Mononychus Brazil 111 chaemostetosus

M. mcgregori Mononychus mcgregori Colombia 28 Mononychellus planki Colombia C HWF* (partim)

Tetranychus urticae T. telarius (partim) Americas. A frica, As1a 39, 50. 117 T. bimaculatus A~a 75

T. cintrabaritrus T. telarius (partim) Brazil, Uganda C HWP

T. wmidus Brazil. Mexico C HWI-* Asia, Caribbean 8

Oligotrychus peruvianus T peruvianus Colombia 27 Paratetranychus peruvianus Colombia C HWI- * P. trinitatis Colombia C HWf*

O. I(Ossyp ii P. gossypii Brazil 50

•c.H.W. t-lectltmann. personal communicalion

Damage from the Tetranychus mi te appears initially on the lower lea ves of the planl. It first shows as yellow dots a long the main leaf vein, eventually spreading over the whole leaf, which turns reddish, brown or rusty in color. Beginning with the basa lleaves, severely infested leaves dry and drop, and plants may die (29). The presence of the Oligonychus mi te is characterized by small white spots, which are webs t he female spreads on the leaf undersides, commonly along the central and lateral leaf veins and

lO MITES

Close-up of web fo rm ~

Sevcre alta e k 2Í' on g alJ¡.H· ar'" "· ~ uf wilchcs'·broom margin. Eggs are dcposited under this web whcre the immature stages develop. Corresponding yellow-to-brown dots form on the leaf upper surface. Damage is more pronounced on the lower leaves (82).

Life history, appearance and habits

M ites are pests primarily during the dry sea son when favorable environmental conditions permit populations to build up to high levels. At CIAT (29) mi te populations increased during the dry season and as the plant increased in age.

The Mononychellus female oviposits on the leaf undersurface, along the midrib or other veins, or in leaf concavities. As the mite population increases, eggs are deposited at random. Nyiira (lOS) states that mite density and egg production are enhanced by dry periods, new leaf growth and high quantities of chlorophyll; they decrease during and after rains ( 107). Preoviposition lasts 1-3 days. with females laying from 15-111 eggs each ( 105). Laboratory conditions produce the f ollowing time periods for the various stages: egg. 3-S days; larvae, 1-2 days; protonymph, 1-2 days; deutonymph, 1-2 days; and adults up to 30days (30, 105). Laboratory studies at CIAT (30) revealed a sex ratio of 62% fe males and 38% males and an egg viability of 92%. The adult M. tanajoa is green in color and has an average body length of 350 mJJ. M. mcgregori is similar in behavior to M. tanajoa. We have often observed M. tanajoa feeding on leaves still within the bud. whereas M. mcgregori feeds on the young lea ves after they have expanded from the bud. Both species have been found on the same plant in Venezuela (E. Doreste, personal communication) and Colombia. Laboratory studies indicate that optimal temperature for M. tanajoa development is 28-320C with a relative humidity of 60% (30. 107). Studies by Nyiira ( 107) and Bennett & Y aseen (8) show that wind is the primary means of dispersa! for M. tanajoa. These mites form ballooning threads by which they lower themselves from the leaves. They are picked up and carried by air currents for long distances; thus movement of the mi te is usually in the direction of the wind. Dispersa! is most active on ht>t days (250C). between the hours of 9-11 a m and 3-S pm. Dispersa! via man, animals or other insects, as well as by walking, is al so important. This mite was probably introduced into A frica vía cuttings. The two-spotted spider mite (T. urticae) is considered a major agricultura! pest worldwide and has been studied by severa! workers (often as T. te/arius) ( 17); however, there are few st\idies in relation to its association with cassava. Laboratorj and screenhouse studies at CIAT (30) indicate that cassava is an acceptable host for this mite.

Oviposition is initiated on day 2 of the adult stage, on the undersides of basal lea ves. Each female is capable of depositing 40-50 eggs over a 20-day period, with the peak period occurring from days 3-9. Laboratory studies (25-2SOC, 60-70% RH) resulted in an egg period of 3-4 days, a larval pertod of 2-S days. a protonymph period of 1-2 days. a deutonymph period of 1-3 days andan egg-to-adult period of 7- 11 days; adults survived up to 22 days(30). Dispersa! occurs vía wind ( although not by ballooning threads). walking or phoresy.

Studies of the 0/igonychus mite on cassava are incomplete. The female spreads a small whitish web along the central and lateral veins on the undersidcs of basal leaves. Eggs are oviposited under this web, where Iarvae and nymphs develop by feeding on the leaf (28). Control

The use of pesticides to control mi tes should be avoided. Their short life cycle enhances the development of resistance to acaricides, and predators are more adversely affected by broad­ sprectrum pesticides than mites are (8). There is also sorne evidence that the application of

13 pesticides can stimulate the fecundity a nd migration of m!tes. To preven! mite infestations on c uttings, pesticides such as malathion a nd Tamaron should be used. These products can be applied by dipping the cuttings in a solution for ti ve minutes (84). The two primary methods of control under study are biological control a nd host plant resistance.

Biological control. Numerous predators have been reported feeding on cassava mites. These include Coccinellidae (Stethorus sp., Chilo menes sp., Verania sp.) Staphylinidae (0 /igota minuta). Cecidomyiidae, Thysanoptera, Phytoseiidae (Typhlodromus limonicus, T. rapax)and Anthocoridae (Orius insiduous). O. minuta, Stethorus sp. and the P hytoseiidae mite complex appear to be the more common predators of M. tanajoa (8, 104).

Bennett & Ya seen (8) hav e evaluated the effectiveness ofbiological control of M. tanajoa with O. minuta. The development period of O. minuta is only 15-18 days, enabling it to react quickly toan increase in host number. 8oth larva e and adults feed voraciously on the mite (as many as 88 larvae and 32 adults per 75 leaf samples ha ve been observed) and can feed on other tetranychids when M. tanajoa is scarce (59). Predator populations were greater during the dry season when mite density was highest and decreased during the rainy period, as did mite density. O. minuta populations were highest on leaves 6- 10 (measured from newest leaf), coinciding with highest mi te populatio ns; its activity is therefo re synchro ni z.ed with that ofthe mi te. The introduction of this predator into East Africa has begun.

Var ieta/ resistance. Systematic evaluation of the CIAT germplasm bank under greenhouse and screenhouse conditions indica tes only low levels of resistance to T. urticae and intermediate or modera te levels to M. tanajoa (30). Nearly 98% of the varieties were highly susceptible to T. urticae, as compared to 45% fo r M. tanajoa. Only 0.4% of the va rieties were in the intermediate resistance range fo r T. urticae, as compared wit h 14% for M. tanajoa. These results indicate tha t there is a higher leve! of resistance to M. tanajoa tha n to T. urticae in cassava germplasm.

Bennett & Yaseen (8) observed large differences in population levels of M. tanajoa on different varieties. Nyiira ( 104) found the lowest M. tanajoa population on the varieties Kru 46, 301, 15 and K. Kawanda. D uring heavy attacks, he observed three times as many leaves on tolerant varieties as on susceptible ones, and leaves developed about four times more slowly on susceptible varieties. Root yield of resista n! varieties was about twice that of susceptible ones. Reports from Braz.il ( 130) a nd Venezuela (4) have also identified varieties resistant to Mononychellus and Tetranychus. 1n recen! field evaluations in Colombia (31). severa! varieties were selected as promising for resista nce.

T hrips Severa! species of thrips are pests of cassava throughout the Americas. T hese include Frankliniel/a williamsi (28). Frank liniella sp. ( 102. 122), Corynothrips stenopterus ( 42. 122), Euthrips manihoti ( 14. 15), Scirtothrips manihoti (39) and Caliothrips masculinus (27). T hrips a ttacks ha ve also been reported from A frica (Z. M. yiira. persona l communication) a nd 1n dia ( Retithrips srriacus. Bellotti, personal obscrvation). Yield reduction ra nges from 5.6-28.4% depcnding on varietal susceptibil ity. T he average reduction for eight susceptible varieties in Colombia was 17.2% (30, 123). These results a re consisten! with reports in literature, which estímate a 15% yield red uct ion (102).

Damage F. wi/liamsi, which damages the terminal bud of the pla nt, is the species of grcatest economic importance. Leav es do not develo p norma lly, leaflets are deformed and show irregular chlorotic

14 ......

. ~ CASSAVA HORNWORM

( Erinnyis ello )

Adult mal~

Fifth in~har hu'" lccUIII!; u u k<~ H~ CASSA V A HORNWORM

Varialion~ in larval color•

Tht live larv1l instars spots. Stylet damage to leaf cells during expansion causes deformation and distortion, and parts of the leaf lobes are missing. Brown wound tissue appears on stems and petioles, and interuodes are shortened. Growing points may die, causing growth of lateral buds which, in turn, may be attacked, giving the planta wi~ches'-broom appearance (6, 102, 122, 131). Symptoms of asevere attack ar~ similar to those for cassava mosaic ( 102).

Life history, appearance and habils Limited information is available on the biology ofthrips on cassava. Larvae and adults of E. manihoti and F. williamsi live in the growing points and onyoung leaves( 14, 122). Frankliniel/a sp. andE. manihoti aregolden yellow and measure about 1.1 mm in length( 14). C. masculinus, a black species, is found mainly on expanded leaves of young plants (27). Adult C. stenopterus measure 1.5 mm and are yellow in color; the head and the last two abdominal segments are darkened. Thrips insert their eggs in the midrib of the leaf undersurface. The greenish colored nymphs live near the veins where they go through two nymphal and two pupa! stages (46). Thrips attack is most frequent during dry periods, and plants recover with the initiation of the rainy season ( 131 ).

Control The use of resistan! varieties, which are readily available,is the best method of control. In the CIAT germplasm bank high levels of resistance to Frankliniel/a sp. and C. stenopterus exist. Approximately 20 percent of the varieties are highly resistant to thrips attack, andan additional 29 percent show only minor damage symptoms (27, 122). Resistance is based on leaf bud pilosity. 1ncreasing pubescence of unexpanded leaves increased thrips resistánce (122).

The cassava hornworm The cassava hornworm Erinnyis ello is generally considered to be one ofthe most serious pests beca use it can rapidly defoliate plants. lt occurs only in the Americas, where in severe outbreaks large cassava plantations are defoliated. This pest has been reviewed in detail by Winder (.134). The hornworm has been previously recorded as Sphinx ello, Dilophonota ello (24, 57) and Anceryx ello ( 13). A less important species Erinnyis a lo pe has been reported in Brazil. Cassava is the principal host of E. ello, which appears to be confined to Euphorbiaceae. Additional hosts reported are Aleuritis /rilaba (24), Manihot glaziovii. poinsettia, rubber, papaya and milkweed ( 13, 36, 99). When heavy attacks occur, larvae may migra teto adjacent crops such as cotton(27, 102). Yield reductions of 10~50% have been estimated ( 110) depending upon plant age and intensity of attack; at CIAT yield was reduced by 18%(31). A decrease in starch content has also been suggested (52). Transmission of bacteria! blight by hornworm larvae has also been reported (27, 99). Damage Hornworm outbreaks with populations of more than 90 larvae per plant have been reported (30). Populations ofthis magnitude will defoliate plants rapidly, and the1arvae will subsequently feed on growing tips and lateral buds. Young plants may be killed. The i nfluence of hornworm attack on the roots is severer in poor than in fertile soi1s (57). Damage simulation studies indicate that defoliation ofyoung p1ants (2-5 months) reduces yields more than that of older plants(6-10 months). Although each lar.va consumes an average of 1107 cm2 of ieaf area dunng 1ts five instars, large populations can be tolerated (28) since under favorable environrnental conditions there can be up to 80% defoliation with no reduction in root yield.

17 Life history, appearancc and habit~

The gcncrally gray nocturnal adult moth has five to six black bands across thc abdomen, '' 1t h gray forewings and reddish hind wings. The smaller males have a longitudinal dark bando ver th.: forcwings. Femalcs live 5-7 days, and thc males livc a fcw days lcss (24). Ovi position occur~ 2-3 days after emergcnce, usually on the upper surface but also on thc petiolc, stcm~ and leal undcrsurfaces (57). A femalc may deposit from 30-50 eggs (30) although rccent observations at C IAT (unpublishcd data) indicatc an average of 850 eggs for individual pairs a'ld 450 whcn there wcrc 11 pairs in the cagc. The eggs hatch in 3-6 days ( 43, 57).

The first instar larvae consume the egg shell befa re moving to the leaf undcrsurface to bq~111 feeding. The duration of the five larval instars is from 12- 15 days (57}. Larvae prefer leedmg on upper leaves, consuming approximately 75% of the total leaf area in the fifth inst.ar. 1 h.: hydrogen cyanide content of the leaf appears to have no effect on larval mortality but leal agc does (28). All instars show color polymorphism, but this is more common during the third in~tar. Colors vary from yellow. green, black, red and dark gray to tan (57).

Fifth instar larvae may reach 10-12 cm in length; they migrate to the soil where thcy lorm chesnut brown. black-hned pupae under plant debris. Larvae may crawl considerable distancc~ prior to pupation. Pupae can diapause for severa! months ( 13. 125). but thc adults normally emerge within 2-4 weeks. H ornworm outbreaks generally occur at the onset of either rainy or dry periods, but attacks are sporadic and the inscct can be virtually absent for severa! years. In Brazil thcy are found all year but are most abundant from January to March; severa! generations may occur. In Colombia outbreaks occur mainly during the dry periods (57).

Control

A biological control program that combines parastllsm of eggs and larvae, as well as predation, appears to be the most effective. Severe outbreaks can be reduced by applying Bacillus thuringiensis. Chemical control should be avoided as infestation is less frcqucnt in nonchemically treated than in treated fields (29, 57).

Egg parasitism by Tricltogramma minutum (99), T fasciatum (27), Trichogramma spp. and Telenomus dilophonotae (57) has been reported to be as high as 94-99% ( 110). An average ol 23 Trichogramma adults emerge per egg (28). Experiments at CIAT were designcd to measure thc effect of Trichogramma release on hornworm egg parasitism. Egg parasitism was measurcd prior to release and periodically postrelease. Results showed a 22-23% increase in parasiti~m four days after release (5, 31). Trichogramma are being released in large cassava)'lantation~ in Colombia. Egg predation by ants ( Colichorerus sp.) and wasps ( Polibias sp.) has also bccn reported (57). Of the reported insect and vertebrate predators of larvae. thc paper wasps (Polistes canadiensis and P. erythrocephalus) appear to be thc most effective (27). Each wasp requires severallarvae per da y. for its own consumption as well as for its brood. Control is most effective when tentlike protective shelters are provided for the wasp in the centerofthe cassava field (57). This practice has been successful at CIAT and on sorne farms in Colombia (30). Othcr larval predators are a pentatomid, Alceorrhynchus grandis. and a cara bid, Ca/osoma retusum ( 36, 51). Predation by birds is also importan! in severa! arcas of B¡azil and Colombia (57, 99).

Importan! larval parasites in Colombia are Apanteles congrega tus and A. americanus (57). These braconid parasites oviposit in the hornworm larvac where the parasite larvac dcvdop. Mature larvae migrate from the host and pupa te on .the outer skin, forming a white, cottouhl..~

18 CASSAVA HORN WORM

Nest of Pulisll!l ~p. CASSAV A HORNWORM

Podisus sp .. a soldier bug th>~t preys on larne

J.arva 11ffected b ) &cillus thuringiensis mass. These cocoons are approximately 3.8 cm wide by 4.1 cm long. Each cocoon contains an average of257 Apanteles pupae. of which sorne 80% will emerge. Liberations at CIAT resulted in an increase in parasitism of hornworm larvae (5. 31 ). Hyperparasitism of Apamele~ by severa! hymenopteran parasites was recorded at CIAT. resulting in an average of 56% hyperparasitism ( 5). Similar bchavior i..~ reported for the ichneumonid wasp Microgaster flaviventris(24). Larval parasitism hy tachinid flies is also reported ( 13. 24. 57.91 ). B. thuringiensiscontrolled hornworm larvae effectivcly at CIA T. Six. days after application, the larval population was 8% of thc control; i.e .. onc pcr plant versus 13 on the control (30). Additional cxperiments show that H. tlwrin¡riensis is cffcctive against alllarval instars but most effective against the first (5). Studics also show that application of B. thuringien:;is does not havean adversecffect on 7i·ichugramma egg parasitism (31).

Laboratory studies at CIAT werc designed to determine length of larval survival aftcr initiating fceding of &cillus-treatcd foliage. Results showed that larvae can survive for 1 to 4 days; h owcver~ the lcaf tissue they are able to consume is reduced by 86%for the third instar, 93% for thc fourth instar and 98% for the fifth instar larvae (30-31).

Cultural control practices such as plowing between rows and after harvest, as well as mcchanical weed control, will destroy mature larvae and pupae. Hand-picking of larvae is rccommended for farmers with small plantings.

Whiteflies

Whiteflies (Aleyrodidae) attack cassava in the Americas, Africa and certain parts of Asia. Although they may not cause economic damage by their feeding, they are of particular importance as vectors of African mosaic disease in Africa and lndia(60, 80). Bemisia tabaci is the most important species in these arcas. B. gossypiperda and B. nigeriensis are also reported from !\frica. The species ~ost frequently found on cassava in· the Amei-ica's are Tria/eurodes \'llriabilis. Aleurotraclrelus sp .• B. tuberculata and Aleuroth'rixus sp. Although B. tabaci has been reported from the Americas, there is sorne doubt asto its capacity to feed on cassava (39a). , African mosaic disease, reviewed by Lozano & Booth (83),is not present in the Americas.

Damage

H igh whitcny populations m ay cause yellowing and necrosis of the lower leaves of the cassava plant. Scvcrc infestations of Aleurotrachelus sp. havc been observed in Colombia, where leaf damage was manifested as severe mottling or curling, with mosaiclike symptoms on susceptible varietics. A sooty mold. often found growing on whitcfly excretions, may havean adverse effect on plant photosynthesis (29). Yield losses as·high as 76% have been recorded at CIAT (unpublished data).

l.ife history, appearance and habits

fhe biology of Bemisia spp. has been rcviewcd by Leuschner (80). Thc cycle varies wilh temperaturc; at 260C. 17 days are required from egg to adult; within a range of mean temperaturcs from 12-260. the cycle varies from 11-50 days. During hot, dry weather and low relativc humidity, no eggs are laid. One generation of B. tabaci lasts 4-5 weeks. depending on climatic conditions; there may be up to ten generations per year (79).

S tudies on t he biology of T mriabilis (29) showed that femalcs depositan average of 161 cggs with 72"; ~urv i val from egg to adult. Average longcvity for females was 19.2 days; for mate:.. !U~ 21 days. The obiong pupal stage is normally pale green, but that of Aleurotrachelus sp. is black, with a white waxy excretion around the outer edge (30). Heavily infested leaves are almost covcred with immature stages, which gives the undersurface a glistening white effect. Infestations have been observed on upper as well as lower leaves.

Adult whiteflies are almost always found on the undersides of dcvcloptng leaves, where they oviposit. Activity depends on temperature, light and rainfall: temperaturc and light seem to have an intcracting effect on flight activity. Temperatures of 27-28°C increase activity but do not induce flight; as light becomes more intense, flight increascs (80).

H igh populations are usually associated with the rainy season when plants are more vigorous (80. 100). Detailed population studies of Bemisia sp. have been conductcd at liTA (79-80): possible factors involved in f1uctuations of population may be a combination of ecological factors. physiological conditions o( the plant. parasitcs and predators.

Virus/vector relationship

Experimcnts conducted at liTA (80) have shown that vector density and Atrican mosaic incidence are related. In screenhouse studies on the virus ' vector relationship, Chant (32) demonstrated that whiteflies haveto feed for at least 4 hours to acquire the"virus" and anothcr 4 hours to become viruliferous; they are then ab1e to transmit the diseaseafter a minimum tccdmg period of 15 minutes. There are no results avai1able for vector efficiency under field condlllon~ : however, it is probab1y dependen! on f1ight activity of the adults. popu1ation d c nsit~ and avai1ability of young (succulent) infected 1eaves (80).

Control

One way of controlling. the vector is by using insecticides (23. 116. 117). but repeatcd treatments are necessary to maintain low populations, making this praetice uneconomical. In addition. numerous wild hosts for Bemisia spp. would ha ve to taken into consideration a~ nc\.\ populations can build up quiek1y from these sources (80). Transmission pressure can be reduccd by using resistan! ·;arieties (61). Studies at CIAT (29. 30) indicate that rcsistance to Aleurutrachelus sp. is available.

Biological control may be feasible. The coccinellid Serangium cinctwn preys on immatures; the mite Typholodromite sp. feeds on adults. The wasp Prospaltella sp. (Encyrtidae) has been reported to parasitize whiteflies ( 108).

Leaf-cutter ants

Several spccies of leaf-cutter ants, all belonging to the genera Alla and Acrumyrmex. havc been reported feeding on cassava in the Americas. especially Bra7il (23. 24, 26. 42. 94. 131) and Guyana ( 12). The most commonly reponed are Atta cephalotes, A. sexdens. A. lea viga la. A. insulans and A. opaciceps; Acromyrmex rugosus. A. octospinosus and A. cliselager.

Damage

Cassava plants can be defoliated when large numbers of worker ants move into a crop. A semicircular cut is made in the leaf: during sevcre attacks, the buds may also be removed. 1 hc~c parts are carried off to the underground nest and chewcd into a paste, on which the lungu~ Rhozites gon!:ylophora ís grown( JI , Í 2). Outbreaks frequently occur during the early months ol the crop; the effect on yield is not known. 22 WHITEFLIES (Aieurotrache/us sp.)

Severe attack

Fonnation of sooty mold on lea ves as a result of attack LEAF-CUTTER ANTS

Ant hill Control 1nsecticides are the most effective means of control. Nests, often readily visible by the sand pites around the entrance hole (6), can be destroyed by fumigation with carbon disulfide and sulfur smoke or arsenales (24). Chlorinated hydrocarbons around the nest (26, 85) or granular M irex baits applied along t he ant trails give effective control ( 112). Varieta! differences t o ant attack are mentioned (94). Cacao, a host preferred to cassava by sorne of the ant species, has been planted with cassava as a protective meas u re (25, 131 ).

Grasshoppers Numerous species of grasshoppers are reported attacking cassava, principally in Africa (53, 67-69, 127). lt is reported that resistance of cassava to the migratory locust has stimulated cassava production in many arcas of Africa (88). Grasshoppers have been observed feeding on cassava in the Americas but are not considered to be a major pest there. The two species of major economic significance are Zonocerus elegans and Z. variegatus (69), both widespread in Africa between JOOn orth and south ofthe equator. Yield losses as high as 60% ha ve been reported whe.1 younger plants are attacked (79). They may also be disseminators of cassava bacteria! blight (J.C. Lozano, personal communication).

Damage

Feeding damage is usually restricted to defoliation but can include young tender bark and seed coats( 121 , 127); in heavy outbreaks the bark is stripped. Immature plants are more severely affected than mature ones, which can withstand defoliation and have successful regrowth. Damage is of major importance during the dry season when cassava, which is tolerant to drought, is often the only available food source. It has been reported from sorne arcas that the roots of defoliated plants are inedible because of excessive hardness (68).

Life history, appearance and habits

The biology of Z. variegatus in N igeria has been studied by J erath ( 67) and T oye ( 128, 129). Adults generally lay eggs in April, placing them in eggpods a few centirneters below the soil surface; hatching occurs about 8 months la ter (79). The five nyrnphal stages last about 2 rnonths. Z. variegarus is a mass migrator whereas Z. elegans migra tes individually. Migration and feeding ha bits of Z. variegatus have been studied in Nigeria (9, 121, 127, 128) and Ghana (68). Increased cassava cultivation appears to intensify problems with Zonocerus (69). Bernays et al. (9) studied the survival of Z. variegatus on cassava and showed that young nyrnphs normally reject cassava after biting it and die if they are confined on growing lea ves. Later instars, if deprived of alternate food sources, will eat cassava, but adults progressively lose weight. Readiness to feed on growing cassava was associated with low HCN levels in the lea ves.

Control

Definite varietal preferences have been noted in studies of feeding habits of Z. variegatus ( 127). possibly related t o acceptability of the bark of certain varieties. On the other hand, the HCN content of varieties has been linked with resistance; however, its role has not been sufficiently confirmed ( 121 ).

With regard to cultural control, p1anting shou1d be done ata time that would ensure plant 2.5 maturity when peak grasshopper populations occur since they prefer young. de..,elopmg plants. The use of chlorinated hydrocarbons has also been recommended (79).

Biological control may also be feasible as Z. variegatus is parasitizcd by mermitlud "orm ~ and the dipteran 8/aesoxipha filipievi ( 129).

Gall midges

Gall midges (Cccidomyi idae) havc bccn reponed on cassava only in the America~ ( 73. IUlJ. 131 ). The species Jatrophobia brasiliensis ( = Eudip/osis hrasiliemis. Clinudiplo~ t s brtl.llltf!ll>l.>) appcars to be the most widespread ( 14. 15. 20. 21. 56).

Damage

Gall midges are considered of little economic importance and generally do not require control. However. in Peru and Mexico. 6- to 7-month-old plants were totally deformed. measuring only 20-30 cm high as a result of a severe atlack. U.nder high populations leaves yellow. retarding plant growth; roots become thin and fibrous (21. 73).

Life history, appearance and haiJits

Adults la y from 4 to 5 individual eggs perleaf ( 131 ). When thc larva e t:merge. thc) penetra te t he parcnchyma tissue. causing abnormal cell growth and the formation of a gall (onc lanae pcr gall) during thc first larval instar. The second and third instars are passed here. Leal galb generally meas u re 5-1 S x 3-5 mm ( 14) and are found on the upper leaf surfacc; thcy arqcllu" •~h grcen to red. narrower at thc base. often curved and casily noticeable. Larval duration • ~ 15-2 1 days. Pupation ( 10-15 days) occurs in the gall; prior to pupation. the larva enlarge~ thc ex 11 hule. which is surrounded by a ~ing of elevated tissue. through which the adult emt:rgc~ (73¡.

Control

Varieta! resistance to gall midges has been reponed ( 130). The collection and destrul:t1on ul affected leaves at regular intervals has bccn recommended to reduce pest population ~.

Severa! larval parasites of gall midgcs ha ve becn observcd. including Tetra.wchu.\ ~p. 1. fasciatus, Dimerumicrus auriceps. Aprostocetus sp. and A. {idius (21. 73. 95).

Cassava lace bug

Lace bug (Vati}!a manihotae) damage is rcportcd from Colombia (23 ). Bnt7il\119) antl ~<., ..:~

Life histor}. a ppearance and ha bit-

The grayish adults. about 3 mm long. are generally found on thc undcrsurfacc of the uppcr leaves. The whitish nymphs are smaller and are usually found fccding on the central part of the plant (27). Laboratory studies at ClAT (2tl) show five nymphal stagcs. lasting 2.9. 2.6. 2.9. 3.3 and 4.8 days. respcctivcly (totaling 16.5 days). The egg stagc is about tl days: fcmalcs depositan average of 61 eggs. Adult longcvity averagcs about 50 days. Prolongcd dry periods wcre 26 GRASSHOPPERS

Dtfoliation ol phmt iu uurlh<·a~t~rn UraLil GALL MIDGES

(Jatrophobia brasiliensis)

Lellf galls favorable for increased lace bug populations, which were highest during the first 3 months of plant growth (29). ).

Insects attacking stems

Stemborers Numerous insect species have been reported to feed on and damage stems and branches of cassava (Table 2). Although nearly worldwide in distribution, they are of particular importance

Table 2. The common stemborers of cassava.

Family and species Reported from References

CU RCULIONIDAE Coelosternus rugicollis Brazil 22, 26, 43, 48, 77. 92, 119 C. /arpides Mexico, Central 22, 78 America, Caribbean

C. granicollis Venezuela, Brazil 22, 26, 43, 48, 58, 63, 77, 119

C. manihoti Brazil, W. Africa 22, 26, 43, 48, 77. 92, 119

C. notaticeps Brazil 26, 43, 48, 77, 92, 119

C. alternam Brazil, Caribbean 22 Eulecriops manihoti Brazil, Colombia 22, 23, 48, 92, 119 Eubulus sp. Colombia 23

CERAMBICIDAE Lagochirus obsolews Cuba, Nicaragua, Indonesia 24, 101, 114 L. rogersi Colombia CIAT Lagochirus sp. W. lndies, Florida 24

Acanthoderes nigricans Colombia 23

BOSTRICHIDAE Sinoxylon brassai W. Africa 76 Heterobos/ruchus brunneus A frica 76,77

PYRALIDAE Chilozela bifilalis Venezuela 47 Chilomina clarkei Venezuela, Colombia 47, CIAT = Pyrausta clarkei Phlyrtaenodes fibilialis Colombia 23

29 in thc Americas, especially in Brazil (93). They gcnerally cause sporadic or localizcd damage. and nonc can be classified as universal pests.

The most important stemborers bclong to the orders Coleoptera and Lcpidoptera. ·¡he dipterans Anastrepha spp. (fruit flies) and Silba spp. (shoot nies), which may abo bore 111 to the stem, are described separately in this report. Stemborers appear to be highly h o~ t ~p e.c1l1e. ;lllJ few are reported to fecd on alternate hosts. T wo spccies, Megasvma elepha~ and .)) llt'¡Jiu Jl.Orclialis, a re rcported to feed on swollen roots in Venezuela (63). Severa! lcpidoptnan anJ coleoptcra n stemborers are idcntified f ro m A frica ( 76. 77. 114); the only o nc reponed l1 om !\ ~"' is La!(ochirus sp. ( 114) from Indonesia. Sevcn species of Cvelo.vternus are reportl'd attad.lllg cassava in the Ame ricas (22. 24. 26. 48. 5!!. 63. 77, 78, 92). and C. manihori is report..:d a~ a pe~llll Afriea (22). O nly Cvelvsrernu.\· spp. and Lagochirus spp. are discussed in dctail h..:r..:.

Coelosremus spp.

Damage. l.a rvae of the Coe/osternus wcevils cause damagc by penctrating the stcm and tunneling into the center or pith region. which weakens thc plant; stems and branches may eventually dry and break reducing the quantity and quality of planting material (22. 63). Although larvac of e sulcolwu.1· have been observcd feeding o n undcrground parts ofthc stem, they ha ve nevcr bcen found attacking roots(92). butthcy can reduce root production (78). Frass and cxudate from the stem wood, cjccted from burrows by feeding larvae, can be found on infestcd branches or on the ground bclow the plants (22). Adults al so fecd on thc tips of young shoots or stems, which may retard growth (77, 92. 93).

LA[e hisrory. appearance and habirs. Females may oviposit on various part~ ol thc plant but prefer the tender parts (35). 1n e alrernans. oviposition has bccn obscrved near brokcn \JI' cut ends of branches or beneath the bark in cavities made by thc proboscis (22). Ovipo~i tion by C. granicollis begins 3 d ays after copulation; the female penetrates the stem. dcpo~iting up to severa! whitc eggs. often no more than one pcr day (93). Larvae vary in si1e depending upon the species. Fully grown larvac of e alternan\ an.: ló mm in lcngth. with a maximum width of 4 mm, whereas those of e rarpidel are 9 x 2.5 mm (22). Mo~ l larva e are curved, with a yellowish white to pale brown body, a rcddish brown hcad cap~ u k and black mandiblcs (78). 1n C. rugicollis only a single larva is found in cach stcm. w h erca~ in the other spccies there may be severa! (22). Thc larval pcriod rangcs from 30-60 da y~ (93). 1 he lully grown larvac of all specics pupate within a cell constructed in the pith region. 1 he pupa • ~ hclJ securely in place in its chamber at one end of the burrow with larval frass; d uration o l thc pupa! pcriod is a bout 1 month (22, 78). After emerging from thc pupa! case, the adult m ay 1cmain in thc chamberfor severa! days befo re leaving the stem. Adults range in size from 6 mm in lcngth for C. granicollis to 12 mm for e alrernans and C. rugicollis. Adults are lightto dar k brown and m ay be almost complete!y covcred with yellowish sea les (22, 92). They are active throughout thc ycar. but activity may decrease during cooler months in sorne arcas (93).

La!(ocllirus spp.

Larvae of Lagochirus spp., lo ng-horned beetles, cause damage similar to that ol Coelo.\rernus.

Ufe hisrory. appearance and habirs. Adults oviposit in stems and branches about 2.5 cm bdow the bark; eggs hatch in 5-6 days. Thc larvae, which takc about 2 months to develop, meas u re up to 29 mm; thcy feed at the base of the plant and many can be found in one plam. 1 he pupa! period, which lasts about 1 month, takcs place in the larval chambers in thc stem. Adults are 30 LACE BUGS ( Vatiga manihotae) TEMBOR ERS

Larvae. pupae and ~dulh uf Coelosternus sp.

Lana of Chilu: ela hifilalis nocturnal, rapid fliers, active throughout the year. They are brown in color, about 17 mm long and feed on leaves and bark (24).

Control Since adult stemborers are difficult to kili and larvae feed within the stems (22, 103), pesticida! control is impractical. Resistance to Coelosternus spp. has been found in the lines 103 Brava de ltu and 192 ltu (103). Cultural practices that will reduce pest populations include removal and burning of infested plant parts (22, 24, 89, 93). Only uninfested and undamaged cuttings should be used for propagation (24).

Fruit flies Two species of fruit flies, Anastrepha pickeli and A. manihoti (Tephritidae) have been identified attacking cassava in Colombia. The fruit fly was originally reported attacking the fruit, where it causes no economic losses (71, 136). We have observed fruit flies causing severe damage to stems in Colombia, Venezuela and Central America.

Damage

When oviposition occurs in the fruit, the larvae bore throughout the fruit, destroying the developing seed. The infested fruit will shrivel and become soft, turning yellow green in color (30). Larval tunneling in the stem results in brown galleries in the pith area. A bacteria! pathogen (Erwinia carotovora var. carotovora), often found in association with fruit fly larvae, can cause severe rotting of stem tissue (29). A white exudate may flow from the larval tunnel and exit holes. As a result of severe attacks, growing points may collapse and die, retarding plant growth and encouraging growth of lateral buds. This secondary rotting may cause a reduction of yield anda loss of planting material. Damaged stems have a rotted pith area, and germination of cuttings from this material can be reduced by as muchas 16% and may be delayed by severa\ weeks (30-31). In experiments at CIAT, as niany as 84% of the plants have been attacked (29). Root losses are suspected but not known. lt appears that plant age at the time of attack is important; younger plants (2-5 months) suffer more damage. Cassava plants can apparently recover rapidly from fruit fly damage, given adequate, well-distributed rainfa\1. Plants that had severe rot at 3 months, with dead or rotted growing terminals, were compared to healthy plants over a 6-mnnth period. Plant height measurements showed that within 5 months the damaged plants had recovered and attained the same height as the nondamaged ones (30). lnvestigations were carried out at CIAT to determine germination and yield losses dueto the use of Anastrepha-damaged planting material. Cuttings were separated into five groups, based on damage grades ranging from O (no damage) to 4(severe rotting and tunneling throughout the pith area). Results showed a decrease in cutting germination, ranging from 5%for grade 1 to 16% for grade 4, an average of 9% reduction ingermination for damaged cuttings.ln addition, plants from damaged cuttings yielded 17.4% less than those from undamaged cuttings; this means a loss of nearly 7 t roots f ha ( 31 ).

Life history, appearance and habits The yellow- to tan-colored female inserts the egg in the succulent part of the stem, about 10-20 cm from the tip, so that about one third of the egg with a slender white rod protudes. After

33 hatching, the white to yellow larvae bore up- or downward in the stem pith regions. Since numerous eggs may be deposited in one stem, severallarvae may be found per stem. The fruit fly 1b acterium association is not fully understood (30). It appearsthat the bacterium is present on the stem, where it can liveepiphytically. Although it is probably not transported by the fly, the boring action of the larvae under high humidity conditions provides the wound needed for bacteria! entrance into the stem. Under favorable environmental conditions of adequate rainfall and high humidity, rotting develops (29). Rotting does not seem to favor larva e; inspection of rotting stems showed 40% larval mortality. Thus major fruit fly population increases may result from infestations of the cassava fruit or alternate hosts rather than from stem infestations. Mature larvae lea ve the stem or fruit and pupate on the ground. The larval exit hole is clearly visible in the stem. Adults emerge in about 17 days. High fruit fly populations occur year round, but extensive damage is usually associated with the rainy season.

Control Since st:verest damage coincides with the rainy season, rapid plant recovery is facilitated and control meas u res may not be required. An evaluation of CIAT's germplasm bank indicated varietal düferences in degree of larval attack. Larval parasitism, as high as 16%, by a braconid Opius sp. has also been observed in the fruit (30); however, parasitism oflarvae in the stem has not been found. Hydrolyzed maize was the most successful attractant used in traps for adults. As regards chemical control, it was found that fenthion, applied as a foliar systemic, gave nearly 100% control of the larvae in the stem (30).

Shoot flies Shoot fly damage has been observed in most of the cassava-growing regions of the Americas ( 10, 136). This pest has not been reported from Africa or Asia. Severa! species, all belonging to Lonchaeidae, have been described, but Silba pendula (JO) and Lonchaea cha/ybea ( 10) are the most important. S. pendu/a [ =Carpo/onchaea pendu/a ( 136). Lonchaea pendula ( 103, 136 ), L. batesi (73), L g/aberrina ] is known to attack severa! other hosts including Mamrnea americana, Mangiera indica, lngafeullei, Eugenia sp., Atrus sp. and Capsicurnfrutescens (72, 136). Other shoot flies are Silba perezi ( 118), Antherigona excisa ( 103), A. excelsa (45), Euxesta eluta ( 103) and Neosilba perezi ( 133). Only S. pendula will be discussed in detail, the behavior of which is similar to that of L chalybea and S. p erezi.

Damage Larval feeding damage is manifested by a white to brown exuda te flowing from the growing points, which eventually die. This retards plant growth, breaks apical dominance and causes germination of side buds, which may also be attacked. These symptoms resemble witches'­ broom disease ( 102). 1n sorne cases only part of the tip is killed, and the shoot continues to grow. Younger plants are more susceptible to attack; repeated attacks may cause plant stunting (30, 103. 131). During severe outbreaks, 86% of the plant population has been reported affected (24). At CIAT (27, 28) simulated damage studies, removing 50 and 100% of the shoots on plants 2-5 and 6-9 months of age, showed that the degree of economic damage is dependen! upon plant variety and age. The late-branching variety Mecu.l50 was more susceptible than Llanera at early stages (2-5 months), and yield was reduced by about 30%. Shoot removal from 6-9 months did 34 FRUIT FLIES

(Anastrepha sp.)

Adult emale

Stem section ~ho" ing hlrHI~ allll rol Cllused by Erwtnia sp. rRl 'IT rl.IES

r~ pical '~ mplumalulu~: ~ ul ull~<~ . 'hcm ing apic;tl rnl and lale' e'11dale

Propaaation mattrial affecled by Erwinia sp. as a result or fruit fiy attacl not affcct yields of either variety. On an individual plant bas is. thcrc was a 15.5. 16.7 and 34. 12 ma) he overestimatcd ( 30).

Studies in Costa Rica showed tha t shoot fl y a ttack resulted in increased branching. loliagc and production ( 120). S_imu!atcd damagc studics in Florida ( 133) resulted in reduccd hc1ght ol damaged plants ( 159 cm vs. 241 cm) and an increased number of terminals for plants attacked once a month. H owever. there were no significan! yield differences. Damaged plants had approximately the same number of )caves as undamaged o nes.

Life histor). appearance and habits

fhl' dark meta llic biUl' adult of Si/ha pene/u/a oviposits bctween the uncxpandcd lca\Cl> 111th o.: growin¡¡ point:; o rin a small eavity made in the tissue by the ovipositor( 136). A~ man) al> 22 q~g~ pl·r , IJoot ha ve hcen observed but 3-8 eg.g~ per shoot is average ( 24). The cggs hatch m ahout 4 da ~'· and the young larvae tunnd in the soft tissue. eventually k illing the growing point ( 24. 1.1 1). Sc\l'ral whitish larva e m a ~' he found in thc affected ti p. lt is claimed that the )anal exudatc gl\c' protcction against pa rasites and inseeticides (24). The larval period is about 23 da)~: lanac rupate in thc soil and thc adult fly emerges a ho ut 26 days la ter ( 13 1) . The fly is c~pcci all) acll\ e o n sunny days. '

Devclopment of the immature stages of N. perezi appears similar toS. pendula. but the adult of N. perezi lives 3-5 times longer than that of S. pendula ( 133).

Attacks m ay occur throughout the ycar (M): but in many arcas they are scasonal (24. 35. 103). oftcn at th.: onsct of the rain y sea son ( 131 ). At C lA T (30) the dry period was favorable lo r h1ghcr shoot fly populatio ns.

Control

fhc lack of da ta showing significan! yield losses due to shoot fly damagc indicat es that control mea~urcs m ay not be necessary. lnsecticide applications should be avoidcd since thcy a re co~ lly and their effecti\·cness. in tcrms of increased yields. has not been provcn.

Cultural practices. D cstruction o f infestcd shoots a t weekly intcrvals has bcen rccommcnded but is no t bclicvcd effective since there a re alternat e hosts ( 136). Plantingdates can be adjustcd ~u that the youngcr growing stage is passcd during low shoot fly populations (27. 30. 103).

Re.l'istance. Distinct varietal differences in susceptibility to shoot flics havc bccn obscrved. but no extensivc scrccning has been done ( 100. 101 ). In Guadcloupe. the varictics Petit Bcl A1r 4. Rais Blanc. Campestre 10 and Gabela wcre more resistan! to L. chalybea (66). In Bratil. tho.: varicties IAC 141 R and Ouro do Vale showed sorne rcsistancc toS. pendula (19).

Chemical comrol. Larvae are difficult to control. Systemic organophosphates have been used during early a ttacks when populations are high (23. 101). lnsecticides anda sugar solution sprayed on plants actas a bait for adult control (96. 101 ). F ly traps with insecticide. using decomposing fruits, casein or yeast as attracta nts. are also effective ( 136, 137).

Scale insects

Severa) species of scales have been identified a ttacking stems in many cassava-growing regions of the Americas (24, 27, 29, 38, 109), Asia ( 44, 53, 88) and Africa (33, 53, 126) (Table 3). 37 1- arnd~ and 'P~CIC' Rcpurtcd frum

DI \SI'II >II>AE A omtlom rtilu.1 all'lll i\mcrica>. AlrKa. """ =Con""' l'li/111 ditpar A'lól ( 1a1wan. lnll•al =lr¡,itl tllap ill'.\ di.'flar Afm·a =1 .< 'f'llltJIIIJilll'v alha Cuha PuulliiJlfl muwr Pcru = 1/t'lllll JruJntl\f,¡, nrinor Pcru

('()( t'IDA I Slllllt'tlll ilt·nu1plwnim Madaga,car =l.t 'lraC'nca Maurit iw• .\ . 11/)!fil Madaga>Cal. M.da~a. l ndnnc\la S . coflt•ue M ada¡!;"ca r .\ mmmdu Colomhia

( ·,,, , 11' n ndt' Madaga,car \f¡fl/alfl/1 tl11¡wr Madaga,l·ar

l:urlu:or 1111!11 'P Bra11 l 1Jra11l " """"'"'"'" >P·

The most tmportant sea les appear to be Aonidomyti/us albus (34) and Saüsetia sp. ( 44. 53). A. a/bus has been observed on cassava throughout rnost of the cassava-growing regions of the "orld. This sea le. which may ha ve been dissemina ted from one continent to another on planting material. is now the most widely distributed cassava pest.

lhmagc

l . l·av~:' o n attacked stcms ycllow and fall: in scvcrc attacks the plants are stuntcd. thc 1.:1 m111a l hud can hc k illcd and ' tems can dcssicate. cau~ing plant mortality. Hcavy seale po pulallon" m;t) co\cr th~: 'tcm and lateral buds. Sai.uetia co{{eae is repon ed attacking lca\t:,. cau,mg kal curlmg (44). Sea le damagc appears to incrcase whcn cassava i ~ plantcd conti nuall ~ o n thc 'ame la nd. Outhreak, are scvere't d uring thc dry season. thu' aggravatmg drought '11<.:"'·

1 he )!rca t~:'t dam;~gc from sea le attack appears to be thc lo"s of planting material a" a t<:,uh o l thc dcath t>f lateral huds. Studics at C IAT (27) with cuttings hcavily intc,!l.:d with /1. allm.1 rC\ulted in 50-()01 ; '"''in gcrmination. Sto red cuttings can also be lost b~:cau'~: ol '~:a k~ ( 11·, ¡.

R~: c~: nt ,tudit:s al C l i\T ,}lOwcd that yicld losscs duc toA. alhw can rcac.:h II.J ' 1 on a ,w,c.:c ptthk \aricty '' hcn thl· ' 11:111 t~ almost completcly covcred with ' cales. causing SC\<.:rt: dl'l oltauon and occa,io na ll~ dcath of thc lt:rminal hud ( J 1) . Rcduction in yicld (53) and rool 4ualll) ( 126¡ ha\l· hecn rc pnn~:d .

3~ SHOOT FLIES (Silba pendula)

Typical damage

Interior of shoot ~hu" in¡: harne SCALE INSECTS

Close-up ot A. alhus: nulc nil hui~' on scales. made by parasiles Life history, a ppearance and habits

Thc hi ology of A. a/b us has heen studied in dctail by Swaine ( 126). Thc female sea le ul rl. alhu., is musscl shapcd and covcrcd with a white waxy cxcretion. The cast skins ofthe f i r~ t and 'c~:u nd nymphal stagcs are incorporatcd i.n the sea le. Unlikc the females. males ha ve \\ell-dndopcd kg' and wings. T hc fcma lc produces an average of 47 cggs. dcpositing them bet.,., een thc uppo.:r 'ca k covcring and thc lowcr cottony secrction. During ovipositi on the femalc shrinh and ~hr 1\ o.:b u p. Eggs hatch in 4 days: the first nymphal instars (crawlers) are locomotive and candispcr'c. ·¡ ho.:"· crawlcrs become fixed in 1-4 days. cover themselves with numerous fine threa d ~. mo lt 111 11da )' and become immobile. After 4 days the adult female appears a nd commcnces o~ ipo ~ 111 on 111 1-l days. One female generation is passed in 22-25 days.

1n laboratory studies at CIA T (31) o n excised cassava stems. m ale sea les pass through two nymphal stages. averaging 10 and 6.5 days. respective!y. anda prepupal and pupa! stage of 4.5 days in tota l. Adults live from 1-3 days and the male life cycle is about 23 days. T here are threc female nymphal instars. averaging 10. 5 and 9 days. respectively. The third instar is the adult stage. Eggs a re oviposited under the sea le and nymphs emerge du~ing a 7-day period. with peak cmcrgence occurring from the 3rd to 5th da y. Each female produces an average of 43 nymphs.

Females of Eurhizococcus sp. are described as very mohile; they en ter the soil and 1n 5- i da)~. the ootheca with eggs appears on the soil surface. There are three nym phal i nstar~. totailng 2ll days, beforc the female appears. No ma les were observed (38).

Dispersa! occurs by wind. active crawling or infcsted cuttings. The m ost importan! mcan~ ' '' d issemination is by storing infested cuttings with healthy ones ( 126).

Control

T he most effective means of control is through the use of uninfested planting matcnal and cutting a nd burning infested plants to prevent the spread of infestation (84).

Chemical control. Chemical control may be reqúired during the dry scason. M ~:;t ~ lll ~:d 111 pcrc(;ntage of adults killed. systemic insecticides a nd parathion were most effcctivc (3. 124). A, for chemical control of cuttings. dipping those that are infested with crawlers in DDT cmub 1 o n ~ for 5 minutes reduces infestation; however, heavily infested cuttings still germina te poorly (27. 126). The insecticides malathion 4%( 1 gfliter). Hostathio n ( 1 cc/ liter). Tamaron ( 1 ce litcr) and Trio na + malathion (2 ce+ 1 g / liter) all prevented a rapid increase of sea le po pulatio r" al ta planting (J I, 84)

Bio/ogical control. Heavy predation of A. a/bus by a coccinellid, Chilocorw lil.lltgnw. r~ reported (76). Hymenopterous parasites, Aspicloiphagus citrinus a nd Signiphora ~p .. aro.: reported in C uba (24).

We have observed heavy parasitism and predation of Saissetia miranda in the ficld. but th~: species have not been identified. W e ha ve a lso found a brown, spongelike fungus. Sepwba.\ldtwn sp .. growing o n A. a/bus.

Mealybugs Mealybug damage to cassava has been reported from Colombia (28, 30). Brazil (2. 64¡ and parts of A frica (88). The species at C IAT has been identified as Phenacoccus gulsJpll, th o.: Mexican mealybug; and P. gossypii and Phenacoccus sp. a re reported from Brazil (ó4). l'.

41 manihoti has recent ly been reported from Africa (Zaire) and South America (7). Oth..:r mcalyb ug~ reported from A frica are Pseudococcus virgatus ( = Ferrisiana virgata, Da~tu luptu~ virgatus). P~eudo coccus citri and Pseudococcus adonidum (88).

Damagc

Thcrc is no record of economic losses in cassava rcsulting from mealybug attack; o h~c r va u o n~ indicate that this pest is capable of causing crop losses. Albuque rque (2) reported a se' ere attat:k of mcalyhugs causing plant mortality at the Centro de Pesquisa Agropecuária do 1 rópi<.:o U mid o in Belém. Brazil in 1975. This was the fi rst time this pest was reported from thc Ama1.0 n region. I\JI I50cassava varieties at the center_were susceptible. High mealybug populations ca u ~e dcfolíation and drying of stem tissue, resulting in a loss of planting material. Lea' es will turn ycllow and dry, and defoliated plants form néw·buds. which are a lso attacked (30).

In :\frica. P. manihoti first attack.s the terminal points of the shoots, then the petiolcs and ex pa nded leav.es. 1ntern odes are shortened. t here is leaf curling and reduced new-leaf growth. A ~ population density increascs. all green parts of the damaged shoot eventually die. Infestation of the lower leaves, together with natural Ieaf fall during the dry season, gives the plant a "candlestick" appearance (81).

Life history, appearance and habits

P. ~ossrpii has a widc host range. including food crops as well as many ornamentals (90). Femalcs deposit sacks containing a large number of eggs around the axil of bra nching stems or lea ves. on the undersidc of the leaf where the leafpetiolejoins the leaf, or around the buds on thc main stem. The young nymphs. sho rtly after initiating feeding, exude a white, waxy material from their bodies. which fo rms a cover over the insect. High populations give a cottony appcarance to thc green or succuit'nt portion of the stem and on the leaf undersurface. They do not rema in fixed but movc slowly o ver the plant surface (2. 30). Adults measure about 2.4 by 1.5 mm.

l.ife cycle studies of P. gossypii were conducted on excised cassava stems and l eave~ in the lahoratory (temperature 26-28°C. RH 75-85%) at CIAT (31). There are three femalc nymphal instars averaging 8.6. 5. 7 and 6.3 days. respectively. Adult females a re able to survivc fo r up to 2 1 da y~ : oviposition occurs over a 5-day period, with an average of 328 eggs per fcmalc. Egg~ are located in an egg pouch which the female carries o n the posterior end of her body unt!l thc nymphs hatch. l\ymphs are mobile throughout their life cycle but may rema in fecding in ono.: area for severa( days. Thc female remains wingless whereas the male develops wings, cnabling fli ght. ~1al cs pass th rough two nymphal stages (8.5 and 6.0 days. respectively),a prcpupal (2.1 da y~ ) and pupal (2.1 days) stage befo re adults emerge. Adult males live from 1-3 days. -1 hcr..: i~ a scx ratio of o ne mate to threc females.

l.cuschner (81 ) describes P. manihoti as probably being parthenogenetic since no mat e~ ha ve bccn obscrvcd in the field or laboratory populatior.s. He reports that the female lays about 440 cggs during its life span. Eggs hatch in about 8 days. The duratio n ofthe nymphal stage~ 1s about 25 da,·s at 25•JC and thc fcmalc adult life span is about 29 days. T he dry season a ppcar~ to la\ or rncalyhug population buildups.

Control

Reports indicate that this pest may be difficult to control. Albuquerque (2) s •. a t e~ that IW 42 SCALEINSECTS

The black scale Saissetia sp. MEALYBUGS

( Phenacoccus gossypii)

T~ pie al damag~ tu plowl

Adult Cleothera onerata. a w.:cinl'llid predator

Pupa and adult of Ocyptamus '1'·

n~mph insecticide gave complete control but that parathion was most effective. Biological control and host plant resistanr.e studies have been initiated. Several predators and parasites of P. gossypii have been collected at CIAT (31). Predators include Cleotera onerata, Cleotera sp., Scymnus sp., Coccidophilus sp., a Coccinellidae; the neuropterans Chrysopa ario/es and Sympherobius sp.; the dipteran Ocyptamus sp. (stenogaster Will. complex) and the lepidopteran Pyroderces sp. The only natural enemy of P. manihoti found in Zaire was the predator lycaenid butterfly Spalgis lemolea (7, 81).

Insects that attack roots, cuttings and seedlings

Grubs Grubs are pests of cassava all over the world and are reported as a serious problem in 1ndonesia (74). Although severa! species are mentioned in the literature, Leucopholis rorida (Indonesia) and Phyllophaga sp. (Colombia) appear to be the most important. The adult stage of the grub is a beetle, usually of the family Scarabaeidae or Cerambycidae. Those reported in literature (29, 44, 74, 114) include Leocopholis rorida, Lepidiota stigma, Euchlora vírídis, E nigra. E. pulchripes, Anamala obsoleta, A. atcharalis, Phyllophaga sp., Heteronychus plebejus, Opatrum micans, Corphopilus margirellus, Dactylosternum sp., lnesida leprosa, Petrognatha gigas and Sternotomis virescens.

Damage White grub damage is characterized by the destruction of the bark and buds of recently planted cuttings and the presence of tunnels in the woody part. These cuttings m ay rot and dic. When young plants (1-2 months) are attacked, they suddenly wilt and die. Larvae will feed on bark of the lower stem just below the soil, roots and swollen roots (6, 74).

Studies with Phyllophaga sp. at CIAT (29) show that germination could be reduced by 95% in experimental plots; losses of 70% have been reported from Madagascar (44).

Life history, appearance and habits The biology of L rorida on cassava has been described in Indonesia (74). Adults become active after the rains ha ve started, and the most severe damage occurs about 4-6 months later. The adult beetles initiate oviposition about 9 days after mating, Jáying up to 37 pearly while eggs singly, 50-70 cm deep in the soil. Larvae hatch in about 3 weeks. The larval stage is about 10 months, with the 4- to 6-month-old larvae being the most destructive. Larvae live about 20-30 cm deep in the soil where they feed on roots. Pupation takes place ata depth of about 50 cm. The prepupal stage is 14 days and the pupal stage is about 22 days. Additional hosts include maize, rice and sweet potatoes. Observations of Phyllophaga sp. in Colombia indicate that there is a one-year cycle, with heaviest damage occurring at the onset of the rainy season. Attacks often occur if cassava is planted in land previously used for pasture orina weedy, abandoned field. High populations can often be detected at the time of land preparation.

Control Biological control. Severa! larval parasites of the grub have been identified (74) including severa! species of Dielis (D. lectuosa, D. tristis, D. thoracica, D.javanica, D.formosa and D. annulata). Parasitism in one study reached 26% (74). A muscardine fungus Me10rhizium 45 anisopliae is pathogenic to the grub, and recent experiments at CIAT indica te that this may be an effective control method (30). Diseased grubs have been found under natural conditions (30, 74). Chemica/ control. White grubs were controlled with aldrin and carbofuran as a dust or in granular form applied below the cutting in the soil (29); insecticida! dip treatments for cuttings were not as successful.

Cutworms

Cutworms, a universal pest, have been reported to attack cassava in the Americas (28, 37) and Madagascar (53). The species reponed are Prodenia litura [ = Hadema liuoralis (53) J , P. eridania [ = Xylomyges eridania (37)]and Agrotis ipsilon (28).

Damage Cutworm damage to cassava can be grouped into three categories: (a) Surface cutworms, such as A. ipsilon and P. litura, chew off plants just above, at, ora short distance below the.soil surface, leaving the plant lying on the ground (6, 53). Plants will recover and continue to grow. A similar type of damage by crickets is reponed (1). The larvae of A . ipsilon are greasy gray to brown, with faint, lighter stripes ( 6, 28). (b) Climbing cutworms ascend the stem, feeding on buds and foliage; they may also girdle the stem, causing the upper part of the plant to wilt aild die. Larvae of the southern armyworm P. eridania have been reponed to cause this type of damage in cassava-growing arcas (37). They are dark gray to black in color, with lateral yellow stripes. (e) Subterranean cutworms remain in the soil, feeding on roots and underground parts of the stem, causing a loss of planting material. The bark and buds may be completely stripped. We have al so observed A. ipsilon attacking cuttings in Colombia (6). Losses of young plants as a result of cutworm damage may reach 50% making it necessary to replant. 1n simulated damage experiments at CIAT (28), shoot removal of recently germinated cuttings showed that sorne varieties and shorter cuttings are more susceptible to this damage.

Life history, appearance and habits Thc biology of the cutworm species that attack cassava is similar. Eggs are la id in masses on the undersides of lea ves near the soil. Eggs hatch in 6-8 days and develop in 20-30 days. The pupa! stage (8-11 days) is passed in the soil or under plant debris. Oviposition is initiated about onc week after adults emerge. A generation lasts about 2 months; under favorable environmcntal conditions. severa! generations will occur in one year (37, 53).

Control Cutworm attacks are sporadic but occur more frequently when cassava follows maize or sorghum,or is planted adjacent to these crops. Longer cuttings (30 cm) will allow plants to recover from surface cutworm attack. Cutworms attacking plants at or above ground levcl may be controllcd effectively with poison baits ( 10 kg ofbran orsawdust, 8-10 liters ofwatcr, 500 g of sugar or lliter of molasses, and 100 g of triclorfon for 0.25.0.5 ha). Underground cutworms can be controlled by applications of aldrin or carbofuran around the cuttings.

Termites Termites attack cassava mainly in the tropicallowlands. They are reported as pests in severa! arcas of the world but primarily in A frica (53). Coptotermes voltkowi and C. paradoxts havc

46 MEALYBUGS

Larn of Sympherobius ~p . (Neuroptera) altacking mealybug ovisac

Adull Sympherobius ~p .

Larvu and adull Pyroderces ~p. (Lcpidoplera). predator and pesl of crops such as sorghum WHITE GRUBS ( Phyllophaga sp.)

Larvae attacking prupa¡:atitJII m a terial

C' ullin g~ ~hn ,.lll l( tlo llto cl ot tlc¡:r<'l'' of t.lam a)!C

O eath of secdlin¡: tiUl' tu " ll"d' been identified fro m M adagascar(53). T hey feed o n propagation material roob . swollen root ~ u r growing plants. Principal damage appears to be loss of cuttings; pla nt establishment ca n a bo b.: a ffected severely. especially during prolonged d ry periods (33. 53).

1n Colombia tcrm ites ha ve been observed causing considerable losses in germination. a~ w ~.: l l a~ death of young plants. in several cassava-growing arcas. espccially where soils are sand). In studies done at C lA T ( 3 1) nearly 50% of stored propagating material was lost due to t ermll ~: fecding. and germinatio n losscs of 15-30% have been recorded. We have also obscrved ~wollc n roo! da mage by termites with subsequent root rot.

Control

P ropagation material can be effectively protected by dusting with aldrin, Clorvel or Sevin. .-\ ld rin. a pplicd as a dust al the rate of 1 g per cutting at thetime ofplanting, prevented termite ;¡ttack ol gcrminating euttings (J I ).

C r ickct s

C riekets damage plants by clipping recently emerged young shoots or feeding on the base of the plant. making it mo re susceptible to lodging (55). Gryllotalpa africana, reported from West A frica. is described as cutting a nd piercing róots and basal parts of the stem ( 1). Brachytripses ackatimes has been reported from M alaya (62). Po ison baits such as those described for cutworms appear t o give effective control.

Storage pests of dried cassava

Approximately 38 insects. mainly Coleoptera. are reported as found on dried cassava chips or prod ucts (54. 11 3. 132. 135). Many a re polyphagous; only those able to reproduce on dried cassava are impo rta n t. These include Stegobium panicewn ( 11 3). Araecerus f ascicufatus (54, 11 J. 132. 135). Rhizopertha dominicana (54, 11 3. 135). Dinodew s minutus ( 132), Tribufium ca.\ltmew ll ( 1 l l 132) a nd Latheticus oryzae ( 132). M ost d amage is reported from Asia ( 11 3) and /\frica ( l. 54). and o n imported dried cassava in Europe (132).

:\o data are availahle on losses in dried cassava resulting from insects. Cassava chips were n:duced to dust in 4-5 months in 1ndi a ( 113). Recent studies at CIAT indica te that A . /rl\ciculaws. the coffee bean weevil, and D. minutus. the bamboo powderpost beetle, can cause considerable losses.

Life history. appearance and habits

Cotton (41 ). a rno ng others,gives detailed references and info rmation on the biology ol many of t h e~c storage pests. 1nd ications are that d ried cassava roots a re not a good nutritional medium for i nsccts beca use they lae k prote in. vitamins and m icro nutrients ( 132, 135).

Contro l

P roper sa nita ry mcasures. such as cleaning and disinfecting warehouses prio r to re~ t oc k ing and rap1d re m oval (ll inft·sted material. are the most effcctive control measure!> ( 1). Bittcr 'a r ie ti e~ of ca~sava a re reported to be more resista n! to wecvils than sweet ones (70); ho" ~.:ve r. this necds confirmatio n. Standard grain fumigations also give effcctive control ol t h ~: ~~: p t:~ t ~ ( I IJ l 49 Crop protection

The recent mterest in cassava asan energy source for human. animal and industrial nc;.;d ~ is bringing about an increase in production of this crop, as well as a change m production technology. The need for a relevan! and sound crop protection program take~ on addcd importance. As previously stated, cassava has historically been cultivated on a small sea le with severa! varieties being grown in one region or even on one farm. The genetic variab.ility in this system has helped to safeguard against major cpidemics of pests and diseases. In recent years there has been a shift in this system toward large cassava plantations. employing a limited number of high-yielding hybrids or varieties. These varieties or hybrids are often ideal plant types; that is. efficient plants that will not produce excessive foliage as many traditional varieties do at present. The reasonably stable equilibrium that presently exists between pest and genotype in subsistence agriculture will be almost impossible to maintain in modern agricultura! systems.

The major objective of a cassava pest management program is to suppress insect p;.;~ t ~ and maintain populations below their economic threshold. This should be done with a minima l use of costly inputs. especial! y pesticides. The accomplishment of t his goal requ i n:~ grcatcr knowledge than we now possess of the biology and ecology of many of these pesb. Advantagc should be taken of the favorable factors involving the insect / plantfenvironment intcraction and socioeconomic considerations that make a cassava pest management system an auracti"e and practica! goal. The~e factors include: l. Cassava is cultivated from 8 to 24 months. making the continua! use ot pcsllcld;.;s costly.

2. Being a long-season crop. cassava is ideally suited for a biological control p1ogram, especially in arcas where there is considerable acreage and continua! planting of ca s ~a\i.l . Biological control agents have been identified for many of the major pcsts.

3. The cassava plant is often able to recover from insect damage. During periods ot adcquat~: rainfall. high levels of defoliation can result in little or no yield reduction.

4. Many pests are not widely distributed and pest incidence is often seasonal. The dry pcriuds favor population buildup of many pests, but the plant's ability to withstand long p..:nuds of drought will usually result in its recovery at the onset of rains.

5. Cassava has a high economic threshold; vigorous varieties can lose considerable tuliag;.; (40% or more), and there are periods when the plant can undergo much higher dctoliauon with no significan! reduction in yield. However. the new varieties developed may ha" ;.; a lower tolerance to defoliation.

6. Few. if any. pests will actually kili the plant, enabling it to recover from damag;.; and produce edible roots.

7. The selection of healthy, vigorous planting material, combined with a low-cost tung1c1dal and insecticida! treatment, initiates rapid and successful germination, ensuring ;.;a rl) plant vigor during this important phase and ultimately increasing yield. 8. Studies have shown that there are sources of pest resistance in cassava which, a tthough often low levels. may be adequate to prevent serious crop losses.

9. Cassava is often grown on small farms and under multicropping conditions; th1 ~ ~ ) ~ t ;.;m not only reduces pest incidence but also ensures against pest outbreaks over extended areas. 50 CUTWORMS TERMITES

1nfested planting mat~rilll

Damagr to thickened roob 10. [,·idence is that insects can cause yield rcduction~ during specilic penod~ 111 plam dcvd opmcnt. These period s should he identifíed so that contro l pracllce~ can be intcnsificd during this time.

Sincc cassava pe~ t controi has receivcd only limited attention until recentl). lc\1., il any. n.:al tn:nds or practiccs ha\'e hecome established o ver a wide arca. Cassava is a low-value crop m most area~. so the u'e of costly pcsticides has not beco me a common practice as is thc case with cutton. The use uf p esticide~ does not appear economically justifiable; therefore. their applicatton should be limited. The mention in this paper of the use of insecticides for co ntrolling cassava pests is not necessarily an endorsement of this practice.

The role of different control methods

fhere are severa! methods for reducing pest populations below theireconomic mjur") h.:\ e l. An rntegrated control program utili7ing cultural practices. selection of planting matcrml. r e~ r~tant \aru:tie ~ . biological control and altcrnative methods such as pheromones or attractant~ ~hould he d~·' doped. 1nsecticidc s will be u sed beca use they offer the most immcdiatc and raprd mean~ of reductng pcst populations over a short period. However. it is strongly lelt that no pest managcment program ~hould be dependent upon pesticides and they should be u~cd un!) as a la~t rc~Nt. on a sho rt-time basis. Nevertheless. treating planting material v. ith pc~llcrde~ i~ economical and cffecti,·e for certain pests.

1nsecticidal applications to cassava foliage may temporarily reduce pe~ t populauon ~ . but indications are that thcy are ineffcctive over a long period as thcy may also reduce p a ra~lle and predator populatio ns ( 8. 57). This can lead to rapid buildups of pcst population~ orto ~econuary pc~b ( normally suppressed by natural enemics) becoming more destructive.

1 here an: ~evc ra l cultural practices that can reduce pest populations. These include the u~e ol m ~cct-free planting material. the destruc..tion of plant parts containing shoot nies. stemborer~ and ~cal e in~ect~. and thc planting of severa! varictics on a single plantation. The implementation and practicability o f sorne of these practices may be reduced as more modern agricultura! technology is applied lo cassa,·a production.

Alterna te means of control such as the u ~c of pherom

Sine·~· man~ cassa\ a pests are not widely distributed. especial! y from one continentto another. it '' importan! that an efficicnt quarantine program be developed and enforccd withm and het\\ee n continenb. As new high-yielding hybrids are developed. there will be incrcased rnm emcnt of planting material. Since ca~sava is vegetativcly propagatcd. man) rnsect~ and d 1,ea~e~ can be tran~ported from one area to another. Prccautions should be taken to ~..:nd only 1 n~ect- and di~ea~e -frec planting material. and all vegetative material should be treated with an ¡n~ecllcid c 111 pre\·ent thc di ~~c mination of insects such as scales. mites. mcalybugs. thrip~ ano (l( hl'J" re ~t~ . :'vlatcrial sho uld also be free of stemborers or fruit ny larvae.

\\"e ~~ rongh · feel that an integra1ed control program for cassava pesb should be ba~cd un hll,logll',il con! rol a nd host plan! resistance. Thesc two links in an intcgrated control cham '"JI p la~ unportant role~ in future cassava pcst management programs. Extcnsive studtc~ rn bott. ul th.-,e a re

53 Biological nmtrol

:\umcrous natural encmics ha\e been identified and found efficicnt in reducing po pulatio ns of cassava pests. Cnncentratcd hiological control studics for cassava pcsts are a ra ther rcccnt effo rt: three systcmat•c studics a nd consc4ucnt programs havc hccn inititatcd. Bennett & Y aseen (8) have evaluatcd the effectivcness of hiological control ofthe rnitc M. tanajoa with the Staphylinidac 0/igow minwa. Studies on thc hiological control of thc mcalyhug Phenacoccrts manihoti involvc a collahorativc program betwccn the Commonwcalth 1nst itute of Biological Control in T rinidad. liT/\ a nd CIAT.

A program studyi ng t he hiological control of th.: ca~s a va hornworm. / .. el/u. ha~ hcc11 ' ' ' ..:llú 1 fo r nearly six years at C l AT ( 2!!-J 1 ). Thi~ program combine, egg and la n a l p

Severa! other cassava pests offcr thc possibility of heing controllt:d d kctl\c l\ h~ n.llu•.d cncmics. Thcrc are severa! parasitcs or prcdato rs of \Cale i n".:c t ~. whitd l ie~. thc ga ll llllltg..: .~n J fruit flics that have bccn idcntificd and rc4uirc furthcr study. Prclimanary ~ ludie s at C IAT o n control of thc white grub ( Phylloplwga s p.) using the mu~cardi ne fungus J1ewrhi::ium aniJupliae are promising. Thcre is exccllent potcntial for implementing hiological control a s a low-cost. cnvironmcntal­ ly sound and compatible componen! of a cassava pest managcment program.

Host plant resistance

H ost plant rcsistancc offers thc most cconomical and environmcntallv ~ound ml·an' ul controlling cassa va pcsts. Resistance to pests attacking cassava i ~ no t repo ned cxte ibl\t: l) llith~ literature: most reports deal only with field ohscr\'ations. Ongoing ~y~ t ema t u.: t:'

T hc dccision to idcntify and utili 7c host pla nt resistance for ' pccilll.: ca' "l\ a pt:'" d..:p..:mh u pon various critcria that should be takcn into considcration '' hen estahli,hlllg a pi ogi an1 ol 1 111~ nature. Thesc criteria include:

l. The leve! of cconomic damage hcing causcd h) a particular pe~ t ~ho u l d h..: ~•glll i•l ·"' ' ·

2. Rcsistancc s ho uld be sought only for thosc pcsts where it is co n ~idcrcd ' " '"hit:.

3. Thc a vailability of adcquatc. low-cost alterna tivc mcthods of control ol ccruun p..:''' l "ll'l' negate thc need for cntering into an cxtcnsive resistance hrccdmg prograrn.

4. The levels of rcsistancc needed to reduce pcst population~ below an c<.:o nom•<.: " '.llll) •l' u sho uld be considercd. S ince some cassava varietics havc a high ccono mi<.: th•c~IH>iu. l.,gt• lcvcls of resistancc may not be ncccssary.

5. Low levels of rcsistance can he comhincd with othcr control rncthod' (1.<.: .. bto lug•l..

Cassava is a lcafy. highly heterozygous naturally cross-pollinated.woody perennial. It has a l·m~ p.rowth cyck and is ~:asily propagatcd hy seed or cuttings. lt is grown in a ~call~:l~o:d nilti\atinn pattcrn with many traditional varictics that havc variousdegrees ofsuscep!ihdil) to in,~:cts and disL·ascs. Thcsc charactcristics indicate that thereis a mínimum ofselecti•~: ¡Hc~~llll: hL·inp. ncrtcd hy pc~ts in cassava cultivation. Vertical resistance in terrns ol the gcn~:-lol-g<:nc th~:or y would prohahlv not C\'olvc within such a system: thcrefore. resistance is prohabl) ol thl· hori1ontal typc. inhcritcd multigcnically. Rcsistancc to major cassava diseasc~ appca1' 10 confirm this a~surnption. Sincc horizontal rcsistancc is more stable and entails les' ri,J.. a' to th<.: dc,·ciopml·nt of hiotypcs. cassava inscct rcsistance studies should havc hori1ontal rc~l,l

/\ cassa\ a pcst management program should place emphasis on comhination' ol thl<.:l' lundam~:ntaltactics: (1) host resistancc. (2) hiological control and (J) cultural control. lt 1~ i:nportant 10 note that pcst damagc lo thc cassava plant docs not necccssarily rcsult in a y~<.:lu ·wluct ion <>r lnss ofljuality of thc harwstcd nop: t hcrcforc. control mcthod' nccd not be apph.:d unlcss thcrL~ is an cstirnation ofyicld reduction. Thc ahility ofthe cassava plant to reco\cr trom pcst injur~' is an importan! criterion that should always be takcn into considcration.

The status of cassava entomological research

Concentrated research in cassava entomology is recent. At CIAT. for example, the researeh program is less than 7 years old. anda full-time entomologist has been assigned only forthe las! 4 years. Few national governments have cassava research programs. and entomology seldom occupies a significan! role in any program that might exist.

We are presently confronted with an extensive range of studies that needed to be done beforc an effective pest management program can be developed. These studies should be oriented towards a mínima! use of pesticides and the development of alternatíve control methods that will not destroy the ecological balance between pests and parasites found in cassava plantations. Emphasis should be placed on t he following aspects: determination of yíeld losses and levels of economic injury for the major pests or combínation of pests; the role ofthe envíronment and thc influence of plant age on pest incidence and severity of damage; studíes on thc biology and ecology of all importan! pests, determiníng the most feasíble control methods (host plant resistance for mites. whiteflies. thrips. mealybugs; biological control for hornworms. scaks, white grubs. mi tes; cultural practices for cutworms. fruít flíes, shoot flies); studies on potcntial pest problems that could occur if cassava acreages increase and monocultures and continuous planting of cassava are practiced; investigatíon of the danger of major or secondary pcsts becoming increasingly importan! as high-yielding varieties are released; studies into alternate control practices such as attractants. pheromones. or insect-growth regulators; invcstigating pest problems during the storage of planting material and the establishment phase of the plant; and production of insect- a nd disease-free planting material (as the basis for an efh:ctivc quarantine program, a worldwide survey should be undertaken to identify cassava pcsts accurately and establish their true distribution).

Sincc cassava entomological research is concentrated in only a few institutions, it is feasible to establish guidelines and recommendations for future research goals and the ímplementation of a pest management program. The time todo this is now while cassava entomological research is still in its infancy. In November 1977. a Cassava Protection Workshop, sponsored by CIAT 55 brought together researchers and pest management specialists from al! over the world to consider these problems (18).

Acknowledgments

We wish to thank Carlos H .W. Flcchtmann for his valuableassistance in preparingTable 1 on the cassava mite complex. Severa) researchers. technicians and other personnel havc contributed significantly to the CIAT cassava entomology program. Theirefforts have influenced the writing of this manusc11pt and are gratefully acknowledged by the authors. They includc Jorge Peña and Bernardo Ana~, research assistants; Octavio Vargas, rescarch associate; Jesús Reyes. visiting scientist: J o~e Guerrero, Julio Bonilla. Carlos Olaya, Ana Milena Vareta. Ornar Estrada, Carlos Marun and Luis de la Pava, technicians; and Ofelia Gamba, secretary.

56 Literature cited

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. ~ APPENDIX

Indices for classifying pest damage

Anthony Bellotti Jesús A. Reyes Octavio Vargas H. •

Thus far little attempt has been made to standardize procedures for evaluating pest impact on cassava. Based on our observations in the screenhouse as well as in the field, we have drawn up the following scales with the hope that they will be used by cassava entomologists and agronomists in order to obtain standardized reports, which is basic for comparing results from one country to another. We would also welcome an interchange of experiences in this regard.

Leve! of Type of damage and/ Pest damage or leve! of infestation

Thrips ( Frankliniella o No damage williamsi, DJrynothrips stenopterus. Caliothrips A few yellow spots on terminalleavcs masculinus, Scirtothrips manihoti) 2 Shoots and/ or adjacent lea ves slightly deformed and with yellow spots 2.5 Shoots and/or leaves with moderate deformation (reaching the veins) 3 Severe deformation of leaves and/ or shoots 3.5 Same as in J. plus great reduction in leaf arca 4 Shoots completely deformed or dead; no adjacent leaves 5 Witches'-broom appearance; death ol terminal and lateral growing points

White scales ( Aonidomyti­ o N o sea les present lus albus) A few scales found around lateral or terminal buds 2 Same as in 2; sorne internodes attackcd 3 Scales completely covering growing point> and 50% of intemodes; loss of lower leavcs 4 Approx 75% of stem and branches covcrcd with scales; loss of intermediate leaves S Scales completely covering stem and branchc,; desiccation of terminal shoots

Termites (Coptotermes o No damage spp.) Tunnels in <25% of the cuttings; viable plant

• Entomologist. Vlsiting Scitntist and Rcscarch Aasociate, respectively, Cauava Program, ClAT 65 Level of Type of damage and or levcl Pes! damage of infcstation

2 Tunneb in 26-5~ of the cuumg: '1:thk plau1 3 Tunncls in 51-759é of the culllng: lca\C, " "' and plan! bcgins lo die

4 Tunnels in> 75% of the cuumg: planl~ tl 1<

ShoN f1ics o No damage (Silba pendula. Lonchaea cha~1'bea) U p lo 25% of shools a uackcd 2 26-50% of shoots auackcd

3 51-75% of shools auackcd: plant gro\\th •~ ta•ti~J

4 76-100% o1 shools·aHackcd: plan! g1o\\th •~t.11J~J

Cassava hornworm o o damage (Erin nyis ello) Up lo 10% defoliation 2 11-25% defoliation 3 26-50% defoliation 4 51-75% defoliation

5 76-100% defoliation and/ or growing pOIOl~ ano >lCnl auacked

Fruit f1ies o No damagc ( Anastrepha pickeli A. manihoti) Larval tunneling in stem: plant appcar~ no1mal

2 Tunnels and white exudate or latex m ~~~m. plant appears normal 3 Same as in 2: deformation of shoots 4 Shoots die. rot and terminal collapses

Mealybugs (Phenacoccus o o nymphal stages or adults present gossypii) Nymphs found on undcrsidcs ol lower lca\t'>

2 S ame as in 1: chlorotic spots bcgm to app~a• 011 t he se leaves 3 Adults. nymphs and ovisacs present: partaal chlorosis of basal !caves

4 Adulls. nymphs and ovisacs on pello le~ antl u• >l~m•: total chlorosis of lower !caves and or ncc• o>~> ul their margins; sooty mold on pctiolc> and leaves 5 Death of growing· points and ne" lateral butl, attackcd: leaf necrosis and fall, dc>iccat•on ol >l~m

66 Leve) of Type of damage and/ or Pest damage leve! of infestation

Lace bugs ( Variga o No lace bugs present manihorae. Variga spp.) A few yellow spots on lower leaves 2 Many spots on lower leavcs; leaves turn )'CIIowish

3 Many yellowish red spots on lea ves; lowcr leave~ curl

4 Lower leaves curl and dry up; intermcd;:\le lea ves curl

5 Defoliation of basal and intermediate leav e~; ilpical lea ves turn yellow

Whitenies (Aieurorrachelus o No infestation by adults{no pupac prc~cnt sp .. Bemisia ruberculata, Trialeurodes variabilis) < 20% infestation of !caves/ <5 pupae pcr lcaf 2 20-40% infestation of leaves/ 5- 10 pupae pcr lcaf 3 41-60% infestation of leavesj 11-25 pupac pcr h:af

4 61-80% infestation of leaves/ 26-50 pupac pcr lcaf

5 8 l -100% infestation of leavesj > 50 pupac pcr lcaf

M ites ( Terranychus urricae, Mononychellus ranajoa) •

Beca use of the variations in severity of damage ca u sed at different levels ofinfestation, a sea le was established for each of these species, based on leve! of food preference and symptoms observed on cassava plants grown in pots under isolation (screenhouse and glasshouse) in o rder t o establish favorable conditions for the development of high mite populations.

T. urticae prefcrs the lower a nd intermediate leaves; when infestation is high, they reach the apical region of the plant. lnitia l symptoms are generally in the form of yellowish spots at the base of the !caves or ye ll owish spots forming s·mall patches on the leaf surface. The numbcr of spots increascs as the mi te population increases: there are a large number ofwebs that may cover the wholc pla nt. T otal defoliation finally occurs.

M . ranajoa develops on the shoots and terminal growing points ofthe plan t. Embryonic !caves do not dcvelop no rma lly. In sorne cases the shoot does not develop, remaining complctcly closed: in Other cases the embryo nic leaves devclop. but are deformed. Jnitial sy mpt om~ are fou nd on thc lea ves of the shoots in the form of small translucent spots. scattcred over thc wholt: leaf or at the base of it. As the leve! of damage i n crea~es . there is a widespread mottling ot lea ve~ . Hcavily attacked plants lose thcir leaves progressively. from top to bottom.

Level of 1) pe of damagc and or Pcst damagc leve! of infcstation

T urlicae lnitiation of ycllowish spots on sorne of the lower and/or intermediate leaves

• Prcpared by Dav1d H. Byrnt. V1 s111ng R <"!oearch A ssocia1c and José M . Guerrero, t cchn1c1an ol thc Ch~,\~ PwgJ..tOI "' Ll1\ 1 67 l.evcl of T ypc of damagc and l o r Pest damagc leve! of infcstation

2 Fairly abundan! yello wish spots on lo"~r and/ or intcrmediatc leaves 3 Damage manifest; many spots. small ncc1 u t•~ ton~> and curling of leaves. especially t hc ba>al antl intermediate ones: ycllowing and lm,, o t >om~ ka\n 4 Severe damage. heavy defoliation ot ba>al and

intermediate parts of plant: a largc numh~ • of mites as wcll as webs can be obscncd 5 Total defo liation of plant; shoots redu ~ctl lll wc. with a great number of webs: dcath ol plan!

M. tanajoa (field S hoot and/ o r adjaccnt lea ves with a le\\ cvaluations as well) faint yellowish spots 2 Sorne lea ves have a fcw ycllowish >poi> that >tantl out 2.5 Shoot and 1or nearby lea ves with man) )ClluY. l>h >Jl<>b J S hoot and/ or adjaccnt leaves affcctcd "'1th a >ltght) dlowntg; yellow spots sprcad ovcr thc cntire leal >lllla~c. a slight reduction in shoot si1c can be >c~n 3.5 Considerable dcfonnation of shoot or rcdu~uon 111 "'"· yellowish spots are easily scen

4 Shoot severely deformed or red uccd 111 ,,,,•• m<~ n )

ycllow spots: heavy mottling: widcsprcad ) ello\\ 111g 4.5 Shoot totally affectcd; no leaves u n >hoot: ) cllu\\111)!, a nd dcfoliation of thc intcrmcdiatc pa1t ol thc pb 111 5 Shoot dics: plant docs not dcvclop

68 The cassava mite and in,ed tumplex.

Common name lmporta nt species Reponed from Alternate hosts Yield losses Type of damage

White grubs I.Rucopholis rorida All regions but Numerous 95% loss Feed on planting material Phyllophaga sp. mainly Americas germination and roots and Indonesia

Termites Coptotermes voltkevi. All regions but Numerous Unknown Tunnel in planting material C. paradoxis mainly Africa roots. stems and swollen roots

Cutworms ' Prodenia lirura, Americas and Numerous Unknown Feed on planting material, Agroris ipsilon Madagascar girdle stems and consume foliage

Scales '·' Aonidomytilus albus. All cassava-growing Unknown (a) 20%. (b) SO- Attack stems. which d ry, O' -.o Saissetia sp. areas 60% loss in causing lea ves to fal l. (b) ·Use of germination infested stems reduces germinatio n of planting material

Fruit flies ··• Anastrepha pickeli. Americas Unknown (a) Unknown: (a) Boring of fruit (seed) and stems: A. manihoti (b) 20-30% causes rotting of pith area. (b) Use of infested stems for planting material results in yield loss.

Cassava Erinnyis ello Americas Manihot 20% Foliage. tender stems and hornworml glaziovii single buds consumed poinsettia. attáck rubber, papaya. milkweed

Grasshoppcrsl Zonocerus elegans. Mainly Africa Numerous Unknown Defoliation and stripping of bark l . variegatus Con/.

Common name lmportant species Reported from A !terna te hosts Y ield losses ·¡ y pe of damagc

Leaf-cutter Atta sp .. A meneas '\umcrou~ Unknown Remove foliage e ants2 Acromyrmex sp.

Mitesl Monon_rchellus tana;oa Americas and Africa 'vfanihot sp. Up to 46% Lcaf deformation and dcfohation: hcavy yield reduction or death

Te1 ranrchus urticae All regions Numerous Unknown Leaf necrosis and defoliation

0/igonychus p<'Tuvianus Americas \1anihot sp. Unknown Lcaf spotting and defoliation

Whitcflies' Bemisia tahaci Africa. Asia :-.lum.:rous Unknown Vector 0f African cassava mosaic Aleurotrachelus sp. Ame ricas l lnknnwn Up to 76% Scvcrc motthng or curling of leavc~. prescnce of sooty mo ld e-. J Mcalybugs' Phenacoccw !(OS.\ rpii. Ame ricas '\ umcrou> Unknown Foliage and >tem> attacked. causing P. manihoti Africa stcm drying and leaf fall

l.ace bup' Vatiga manihotae Ame ricas l lnknown Unknown LNtvC> 11 ith ycllow spots that turn rcddish hrown

Thrips• Frankliniel/a ..-il/iamsi. Mainly tn Amcri- Unknown 6-28o/é Dcformation of foliagc. death of bud' Cor_rnothrips stenoprerw. cas but also in and hrowning of ~tcm tissuc Caliothrips masculinus A frica

Gall midgcs• Jarrophohia Americas l ' nknown Unknown Ycllowish grccn to red galls formcd on brasiliensis uppcr lcaf surfacc

S t cmhorcr~' Coi'lusrernus spp .. All regions but Unknown link no" n Boring into and tunncling into ' tcm' Lagochirus spp. mainly Americas and possihly swollcn rc-.ntS" Con t.

Common name Importan! species Repon ed from Alternate hosts Yield losses Typc of damagc

Shoot Oiesl Silba pendula, Ame ricas M a m mea americana, U p lO 34% Larvac borc into and kili Lonchaea chalybea Mangifera indica, apical buds. causing plant lnga feullei deformatio n and stunting -.1 Eugenia sp., Atrus sp.

t lnsecu attaclong plantin¡ matt-ria1

l lnsecu auackmg 1he growtng plan1 : rohi\ge consumto

1 Sap-sucktng 1nsccts and mitc1 • Leaf defonners

> Bud and sttm bomt