TECHNICAL BULLETIN 197 ISSN 0070-2315

CHEMICAL CONTROL OF THE CITRUS LEAFMINER, PHYLLOCNISTIS

CITRELLA (STAINTON) (LEPIDOPTERA, PHYLLOCNISTIDAE), IN CYPRUS

N. Iordanou and P. Charalambous

AGRICULTURAL RESEARCH INSTITUTE

MINISTRY OF AGRICULTURE, NATURAL RESOURCES

AND THE ENVIRONMENT

NICOSIA CYPRUS

OCTOBER 1998

Editor - in Chief

Dr A.P. Mavrogenis, Agricultural Research Institute, Nicosia, Cyprus.

All responsibility for the information in this publication remains with the author(s). The use

of trade names does not imply endorsement of or discrimination against any product by the

Agricultural Research Institute.

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CHEMICAL CONTROL OF THE CITRUS LEAFMINER, PHYLLOCNISTIS CITRELLA (STAINTON) (LEPIDOPTERA, PHYLLOCNISTIDAE), IN CYPRUS

N. Iordanou and P. Charalambous

SUMMARY

The citrus Ieafminer, Phvllocnistis citrella (Stainton), was first observed in Cyprus in ]994. Chemical control of this pest is considered justified only for the protection of stock in nurseries, newly scaffold-budded trees and young citrus groves, which are prac­tically in continuous vegetative growth from spring onwards, and consequently are ex­posed to Ieafminer infestation. In producing citrus groves, biological control and appli­cation of suitable cultural practices is expected to provide satisfactory control.

Laboratory trials were first carried out to select effective insecticides and suitable application methods for economic control of the pest. Then, the residual effectiveness of single applications of selected insecticides, applied with the most suitable method for each, was determined in the field. Following this. the number of insecticide applications required during the year for the most economic and effective control of the pest was de­termined. Out of a number of insecticides found to be effective as high volume sprays, in admixture with summer oil, against larval infestation of the Ieafminer, only acetamip­rid SP and, to a lesser extent, spinosad provided long enough protection (exceeding one month and three weeks, respectively). About five spray applications of acetamiprid SPI year were required to achieve nearly complete and economic control. Other insecticides (imidacloprid SL, abamectin, lufenuron, pyriproxyfen and hexatlumuron) provided pro­tection not exceeding two weeks. A single application of acetamiprid SL or imidaclop­rid SL with the stem paint method on the trunks or on lignified shoots of young trees, or at the base of lignified shoots of newly budded trees, at about I cc f.p./year of tree age, provided effective protection exceeding three or two months, respectively. Therefore, two applications of acetamiprid, or three of imidacloprid are required for nearly com­plete seasonal control of the pest. Imidacloprid applied with the drench method at about 2 cc fp./year of tree age was effective for longer than three months and, therefore, two applications are sufficient for year-round control. However, the most economic control was the application of high volume sprays of acetamiprid SP, and the least economic the drench application of imidacIoprid SL Application of acetamiprid SL or imidaclop­rid SL, by the stem paint method were intermediate.

High volume sprays would be expected to pose some threat to the ecosystem. How­ever, as the young trees to be sprayed comprise only a small percentage of total citrus plantations, such threat is minimal. Conversely, insecticides applied with the stem paint or the drench application method will not affect beneficial insects, thus fitting well in an integrated pest management program.

nEPIAH'I'H

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INTRODUCTION

In Cyprus, the citrus leafminer, Phylloc­nistis citrella (Stainton), was first observed in 1994. It spread rapidly on the island seri­ously attacking new vegetative growth in cit­rus orchards. The insect is a native pest of

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subtropical and tropical Asia (CAB Institute of Entomology, 1986) and is now a serious citrus pest, in China (Zhang et af., 1994), USA (Heppner, 1993; Knapp et al., 1995), Israel (Argov and Rossler, 1996), Australia (Beattie and Smith, 1993; Beattie et at., 1995a, b), Greece (Anagnou et at., 1995), Italy (Nucifora, 1996), Pakistan (Niaz et at., 1993), Egypt (Rezk et at., 1996) and Spain (Lucas-Espadas, 1995; Carijo-Alba et aI., 1995; Garcia-Garcia, 1995).

The damage is caused by the larvae as they feed inside mines in young leaves, leav­ing a distinctive dark line of faecal pellets along the axis of the mine. Infested leaves become twisted. Leaves with two or more mines may dry up. In young nursery plants, in newly planted citrus and in newly budded trees, growth can be seriously retarded. The mines have a silvery appearance owing to the air trapped under the epidermis.

During summer and autumn the citrus leafminer (CLM) completes one generation in 14 to 17 days, whereas in late autumn, winter and early spring completion of one generation can take up to three times longer (Beattie and Smith, 1993). Under Cyprus conditions it completes 11 to 12 generations/ year (Orphanides, personal communication).

Depending on climatic conditions, infes­tation starts from the middle to the end of spring and becomes more serious during the summer and autumn months. It then gradual­ly declines and ceases in winter. In Japan, (Ujiye, 1990) found that there were 5 separ­ate moth flight peaks from May to Decem­ber, more or less synchronized with the flush growths of host plants in spring, summer and autumn.

Despite the potential effectiveness of cul­tural and biological control measures, broad­spectrum insecticides were used in many countries against CLM creating serious prob­lems by disrupting the biological balance. In China for example, routine use of wide­spectrum insecticides disrupted the balance of natural enemies not only of CLM, hut of other citrus pests as well (Chen, 1988), in­cluding Panonychus citri (Huang et al., 1989b) and of scale insects (Du et aI., 1994).

Effective chemical control of CLM is difficult because larvae are protected in their mines, and pupae in their pupal chambers. Repeated applications of insecticides are re­quired to protect the new flushes, as the pest

has many generations per year. However, broad-spectrum insecticides (organophos­phorous, carbamate and pyrethroids) have an adverse effect on biological control agents. Therefore, chemical control of CLM can be justified only for the protection of young vig­orous plants in nurseries, and of newly­planted trees. In mature commercial citrus groves biological control and application of proper cultural practices are considered a more realistic approach for CLM manage­ment (Beattie and Smith, 1993).

Extensive research work on the chemical control of eLM has been conducted in near­ly all citrus-producing countries of the world. In Pakistan, Niaz et al. (1993) report­ed that ethofenfox (Trebon®) and decameth­rin (Decis®) reduced leaf damage up to 97 and 82%, respectively. Rae et al. (996) also reported that a narrow-range oil provid­ed control of leafminer equivalent to that of cartap and methomyl, and that abamectin plus petroleum oil provided complete control of the leafminer in Southern China. In India, Katole et al. (1993) reported that monocroto­phos, phosphamidon, resin soap, fish oil and pangamia oil were the most effective treat­ments against CLM followed by dimethoate, mahna and neem oil, while Bhatia and Joshi ( 1991) reported fen valerate, deltamethrin, cypermethrin, monocrotophos and quinal­phos as the most effective. Neem seed ex­tract was also found very effective in another area of India (lothi, 1993). Valand et al. (1992) reported that three days after treat­ment the most effective compound against CLM was fenpropathrin (Danitol®) followed by tluvalinate (Mavrik®). Shidharan et al. (1989) recommended that phosphamidon should be used for CLM control in manda­tins in India. Permethrin and fenvalerate also provided good control of CLM for 72 hours after treatment in India (Radke and Thakare, 1989). In Australia, Wilson (1991) recom­mended the use of carbaryl, diazinon and omethoate for CLM control. Beattie and Smith (1993) reported that narrow range pe­troleum spray oils (C21 and C23) are gener­ally as effective as insect growth regulators or broad spectrum organophosphate and car­bamate insecticides, and recommended that petroleum spray oils arc the only products to be used in nurseries, home gardens and or­chards. They are safe to handle and of low toxicity to warm blooded animals, they do

not upset the biological balance, do not stim­ulate outbreaks of secondary pests, rarely lead to the development of resistance and their deposits break down rapidly.

The present work was conducted in the laboratory, and in young citrus groves (less than 6 years old) in the Akaki and Meneou areas for two consecutive years in an effort to select effective insecticides and find suita­ble and economic insecticide application methods for the control of CLM throughout the year.

MATERIALS AND METHODS

Laboratory Trials Potted sour orange seedlings of 15 to 20

cm height and 6 mm stem diameter were used in early 1996. Six seedlings at a time were artificially infested with sixty laborato­ry-bred CLM adults in insect-proof cages (40x40x50 cm) for three days under con­trolled conditions (20 to 22 0(', 75% relative humidi ty, natural light). They were used for the laboratory trials after larval mines devel­oped in 3 to 5 young leaves per plant, bear­ing first to second instar larvae. Three trials were conducted, and each treatment was rep­licated three times. In the first two trials the effectiveness of four granular insecticides and four other insecticides, applied to the soil with the irrigation water, were tested. In the third trial eleven insecticides and sum­mer oil alone, were assessed as high volume sprays. The insecticides were assessed on the basis of the number of adults recovered fol­lowing placement of all infested leaves in plastic cups 20 days after treatment.

Granular insecticides. The granular insecti­cides aldicarb (Temik® 15 g) and oxamyl (Vydate® 109) were applied at the rate of 0.4 g f.p. Iplant, while carbofuran (Furadan® 109) and chlorpyriphos (Dursban® 5 g) were applied at the rate of 0.8 g f.p.lplant. Granules of test chemicals were applied on the soil surface in each pot and were subse­quently covered with I em of soil. Irrigation with 100 cc of water per pot followed.

Insecticides applied through the soil with irrigation water (drench method). In this trial imidacloprid (Confidor®) applied at the rates of 0.5 and 1 cc f.p.lplant, oxamyl at 0.4 cc f.p.lplant, dimethoate (Perfekthion®) at

5

0.5 and 2 cc fp.!plant and thiocyclam (Evi­sect®) at 1 g fp.!plant were tested. Each chemical was dissolved in 100 cc of water, which was used to irrigate each potted plant.

High volume sprays. Eleven insecticides, all in admixture with Ultra Fine® summer oil (at 3 cell) and summer oil alone applied at 3 and 6 cc/l, were applied with a small handy sprayer as high volume sprays to the run-off point to potted young sour orange seedlings bearing CLM larval infestation. Imidaclop­rid, acetamiprid (Mospilan®), pyriproxyfen (Admiral®), lufenuron (Match®), spinosad (Tracer®), and fenoxycarb (Insegar®) were tested at the rate of 0.5 cc f.p.lI; hexaflumu­ron (Consult®) was tested at the rate of 0.75 cc f p.!l, abamectin (Vertimec®) at the rate of 0.6 cc fp.lI, cartap and thiocyclam at 1 g or cc fp.!l, carbosulfan (Marshal®) at 1.75 cc fp.!l and Ultra Fine® summer oil (hereafter to be called simply summer oil) alone at the rates of 3 and 6 cc /1.

Field Trials Based on the results of the laboratory trials, two series of field trials were conducted. The first series was calTied out in 1996 at Akaki to study the initial and residual effectiveness of selected insecticides applied once with dif­ferent application methods; the second series was carried out in 1997 at Akaki and Meneou to study the number of applications required for year-round control of the leafminer. In all field trials the treatments were replicated three times. Plots consisted of one lO-tree row. Assessment of effectiveness was based on the number of living larvae and pupae re­corded per 25 young leaves (l to 2 em long) per plot at different time intervals after treat­ment. Effectiveness of each treatment was calculated by applying the formula:

Effectiveness (%) = 100 -(TA/CA)/IOO

where:TA= No of live larvae and pupae in the treated plot, and CA=No of live larvae and pupae in check.

Effectiveness of selected insecticides ap­plied once with different methods, Akaki, 1996. The trials were carried out on young Valencia orange trees (2, 3 and 5 years old). Different rates of imidacloprid, applied ei­ther with the stem-paint application method

6

(application of the commercial emulsion for­mulation of the chemical on the stem (trunk) of trees with a brush), or through the soil with irrigation water (drench method) were tested.

In another trial, two granular insecticides (aldicarb and oxamyl) applied through the soil, and acetamiprid SP (soluble powder) applied with the stem paint method, were assessed.

In all trials, test insecticides were applied once, at the initiation of larval infestation on young leaves (beginning of June).

In another trial, conducted at the peak of CLM infestation in July, ten insecticides in admixture with summer oil were tested as high volume sprays in a 5-year-old Valencia orange grove at Akaki. The objective was to study the initial and residual effectiveness of a single application of test insecticides com­pared to that of imidacloprid applied once with the stem-paint and the drench applica­tion methods.

In all field trials, treatments continued to be assessed for as long as effectiveness ex­ceeded 35%.

Application of imidacloprid with the stem paint or the drench-method. Four trials were carried out with imidacloprid applied with the stem-paint method, and one trial with the same insecticide applied with the drench application method. In all trials the insecticide was applied once on 11 June. In the first two trials, imidacloprid was ap­plied with the stem-paint method on the trunk, 40 cm from the ground, of 2-year-old Valencia orange trees, either undissolved or after it had been dissolved (l: 1) in water. The rates tested were 0.5, 1.0 and 1.5 cc fp.! tree. A 1 em wide paint brush was used to apply the insecticide. In the third trial, imid­acloprid was applied on 3-year-old Valencia orange trees at the rates of 0.5, 1.0, 1.5 and 2.0 cc f.p.!tree, and in the fourth trial on 5­year-old Valencia orange trees at the rates of 2 and 3 cc fp.!tree.

For the drench application of imidaclop­rid 2.5 or 5.0 cc fp.!tree was used on 2-year­old Valencia orange trees. The incecticide was dissolved in 10 1 of water and the solu­tion was applied at the middle of an irriga­tion, individually to each tree, to the area wetted by the sprinklers.

Application of two granular insecticides through the soil and of acetamiprid (SP) with the stem-paint method. The granular insecticides aldiearb and oxamyl were ap­plied uniformly in the basin of each tree at the rate of IS g f.p.!tree, and ilTigation fol­lowed. Acetamiprid dissolved I: I in water was applied at the rate of 0.5, 1.0 and 1.5 g f.p.!tree with the stem-paint application method. All treatments were applied once, on 17 June to 2-year-old Valencia trees.

Application of ten insecticides as high vol­ume sprays, and of imidadoprid with the stem-paint and the drench method. This trial was conducted in a 5-year-old Valencia orange grove which did not receive any chemical treatment against any pest during the year. The test chemicals were applied in July at the peak of eLM infestation. The ex­perimental design was Randomised Com­plete Block with 3 replications. Each plot consisted of one IO-tree row. Ten insecti­cides, each in admixture with summer oil (at 3 cc fp.ll), were applied as high volume sprays with a tractor-mounted high pressure sprayer on 27 July. The effectiveness of these insecticides was compared with the effective­ness of imidacloprid applied on the same date with the stem-paint method, at 5 cc f.p.!tree, and with the drench application method, at the rate of 10 cc fp.ltree. Assessment of the effectiveness of each treatment started on the fourth day after treatment and continued at about weekly intervals thereafter.

~umber of insecticide applications re­quired for year-round control. Experi­ments were can-ied out in 1997 at Akaki with four-year-old Valencia orange trees and at Meneou with two-year-old ortanique trees. which had bean top-grafted on ten-year-old lemon trees. In both trials, the experimental design was Randomised Complete Block with three replications. A plot consisted of a single row of nine trees. Insecticide treat­ments in each experiment were repeated when effectiveness fell below 75%. Effec­tiveness was assessed at biweekly intervals. An account of treatment costs was kept.

Application of insecticides with the stem­paint method. The insecticides imidac10prid and acetamiprid, both as emulsions, were ap­plied undissolved at the rates of 0.4 and 0.6

cc fp.lstem to two-year-old ortanique trees at Meneou. On average, there were three stems per tree. Application required two per­sons' work for approximately two min/tree. The first application of all treatments was made in early June with the first signs of lar­val infestation. Two additional applications of imidacloprid and one of acetamiprid were necessary to achieve nearly complete protec­tion of the trees. In a second trial at Akaki. imidacloprid and acetamiprid were applied at the rate of 4 cc f.p./tree on the trunk of 4-year-old Valencia trees about 40 cm above ground level. The first application was made in mid June with the first signs of larval infestation. Addition­al applications of both insecticides, either at the same height or I() cm higher on the trunk, were made in mid August and in mid November.

Application of insecticides as high volume sprays. This large scale trial was conducted on 500 newly budded (top-grafted) ortanique trees at Meneou. Pyriproxyfen and acetamip­rid (SP) were applied at the rate of 0.5 cc or 0.5 g fp., respectively, in admixture with 3 cc summer oil/I. Two applications of pyri­proxyfen and three of acetamiprid SP were made during the year for the combined con­trol of the California Red Scale (Aonidiella aurantii) and CLM. Pyriproxyfen was ap­plied in early June and in late September, and acetamiprid SP at the end of June, be­ginning of August and end of October. Sprays were applied with a high pressure sprayer to the run-off point. An account of treatment costs was kept.

Application of imidacloprid with the drench method. In this trial, imidacloprid was applied at 8 or 12 cc f.p.!tree through the soil (drench method) in a 4-year-old Va­lencia orange grove at Akaki. The insecti­cide was applied individually to each tree dissolved in 10 I of water at about the middle of a 4-h irrigation with mini sprinklers. Two applications of imidacloprid were made (mid June and beginning of September) to achieve nearly complete protection of the trees.

Observation trial with a combination of three application methods. This unreplicat­ed trial was conducted at Akaki in a plot of 40 4-year-old Valencia orange trees. Initially

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-- --------------- ---- -- -----

imidacloprid was applied in mid June at 4 cc fp.!tree with the stem-paint method. Aceta­miprid (SP) was subsequently applied at the end of July as a high volume spray at the rate of 0.5 g fp. + 3 cc summer oil/I. Finally, a second application of imidacloprid was made in mid September with the drench applica­tion method at 10 cc fp.! tree. It was expect­ed that this combination of insecticide and application methods would provide nearly complete protection throughout the season.

Pest population dynamics In all field trials conducted in 1997 at Mene­ou and Akaki, the number of living larvae and pupae recorded at the different assess­ments were used to draw-up the popUlation curve of the pest from early June till the end of December.

RESULTS

Laboratory Trials

Granular insecticides. Aldicarb and oxamyl completely controlled CLM larvae, carbofu­ran provided moderate control and chlorpyri­phos was ineffective. Aldicarb and oxamyl were later assessed in a field trial.

Insecticides applied through the soil with irrigation water (drench method). Imida­cloprid, oxamyl and thiocyclam provided complete control of larvae. Dimethoate, at both rates tested, caused serious leaf burn to the sour orange seedlings.

High volume sprays. Imidacloprid, aceta­miprid, pyriproxyfen, spinosad, lufenuron, phenoxycarb and cartap completely con­trolled CLM larvae. High levels of control were obtained with abamectin and, to a less­er extent, hexaflumuron both in admixture with summer oil. Cartap, however, was phy­totoxic. Summer oil alone, at both rates test­ed, and carbosulfan provided moderate pro­tection. Thiocyclam was the least effective (Table 1).

Field Trials

Imidadoprid applied with the stem-paint or the drench method. On two-year-old trees effectiveness of imidacloprid (undis­solved or dissolved in water) at all three rates tested with the stem-paint method was very

Table 1. CLM adults obtained one month after insec­ticide application in admixture with 3 ccll summer oil, as high volume sprays, to infest­ed sour orange seedlings in the laboratory

Rate Mean number

lnsecticide (cc or g f.p.lae) of adults

/seedling

lmidacloprid Acetamiprid SP Pyriproxyfen

0.5 0.5 0.5

De De De

Hexatlumuron 0.75 0.6cd Lufenuron 0.5 De Carbosulfan 1.75 Ib Thiocyclam 1.0 1.6ab Abamectin 0.6 0.3d Spinosad 0.5 De Spinosad Cartap* Phenoxycarb

1.0 1.0 0.5

Oe De De

Summer oil 3.0 Ibc Summer oil 6.0 Ibc Check 2a

* Phytotoxic; Means followed by a different letter are significantly different using Duncan' s New MUltiple Range Test (P<O.05).

high until 16 and 26 days after treatment (DAT). However, at 40, and especially at 50 DAT effectiveness was higher with undis­solved imidaclorpid. At 57 DAT, imidaclop­rid continued to provide levels of effective­ness exceeding 75% at all three rates tested. Effectiveness was reduced substantially at 69 DAT and fell close to zero at 83 DAT (Table 2).

On three-year-old trees, higher levels of effectiveness were obtained with the highest rate used (2 cc/tree) at 50, 57 and 83 DAT. At 57 DAT effectiveness still exceeded 90%. Imidacloprid applied with the stem-paint method to 5-year-old Valencia orange trees was less effective. Although at 57 DAT, ef­fectiveness at the higher rate used (3 cc/tree) was 82%, at 83 DAT effectiveness with both rates tested fell to 16%.

Imidacloprid applied with the drench ap­plication method, at two rates to 2-year-old Valencia orange trees at Akaki, provided high levels of protection. Effectiveness was 95% at 57 DAT and remained high (67%) at 110 DAT in the higher rate used (Table 2).

Application of granular insecticides through the soil, and of acetamiprid SP with the stem-paint method. At 10 DAT all chemicals, irrespective of method or rate of

8

- - -----

Table 2. Effectiveness (%) of imidacloprid applied on 11 June 1996 with the stem-paint method. either undissolved or dissolved 1: 1 in water (figures in parenthesis). and with the drench method on Valencia orange trees at Akaki

------- ---------- -- -"--- ..__. -- ----- ----­

Rate Method (cc f. p.Itree ) Days after treatment

--­ - -----­ -----­ --------_ .._~

Stem-paint 2-year-old trees 16 26 40 50 57 69 83 96 110

0.5 100(92) 93(93) 23(24) 4(15) 75 30 1.0 100(89) 95(94) 53(13) 54(27) 79 41 4 1.5 100(97) 99(100) 78(66) 71(0) 81 21

3-year-old trees 0.5 98 73 50 73 II 1.0 98 83 53 52 22 1.5 89 83 67 81 26 2.0 100 78 100 92 22

5-year-old trees 2.0 94 46 61 42 63 16 3.0 95 72 81 82 45 16

Drench 2-year-old trees 2.5 97 89 93 66 57 10 5.0 58 100 100 100 95 83 72 67

----­--­---­ - -­ ---­--­ ._-­ --­ -- ­ "------._-----­ --------­------­

application, provided effectiveness ranging miprid SP and spinosad provided 100% con­from 53 to 89%. However, effectiveness of trol, and hexaflumuron and lufenuron provid­all treatments was significantly reduced at 20 ed 99 and 96% control, respectively. At 18 DAT and more so at 34 DAT, except for the DAT most of the chemicals applied as high highest rate of acetamiprid, which provided volume sprays lost most of their effective­39% effectiveness (Table 3). ness. However, acetamiprid SP still had 96%

effectiveness and spinosad 74%. Imidaclop­Application of 10 insecticides as high vol­ rid applied as a spray lost most of its effec­ume sprays, and of imidacloprid with the tiveness but when applied with the stem­stem-paint and drench methods. At 4 DAT, paint or the drench method, it continued to all test chemicals applied as high volume provide 100% control. At 27 DAT spinosad sprays, except summer oil alone, provided lost most of its residual action. On the con­levels of effectiveness exceeding 80% (Table trary, acetamiprid SP continued to have very 4). On the contrary, application ofimidaclop­ high levels of effectiveness (97%). Effective­rid with the stem-paint or the drench method, ness of imidacloprid applied with the stem­provided low levels of effectiveness (48 and paint and the drench methods remained at 23%, respectively). At 11 DAT, all test insec­ 100%. Effectiveness of sprayed acetamiprid ticides, except carbosulfan and summer oil, SP, gradually fell to 28% at 79 DAT. Over provided effectiveness exceeding 85%. All the same period, effectiveness of imidaclop­imidacloprid treatments, abamectin, aceta- rid applied with the stem-paint or the drench

Table 3. Effectiveness (%) of the granular insecticides aldicarb and oxamyl applied on 11 June 1996. to the soil and of 3 rates of acetamiprid SP applied with the stem-paint methods to 2-year-old Valencia orange trees at Akaki

Days after treatment Rate Method of

Insecticide (g f.p.ltree) application 10 20 34

Aldicarb 15 Soil 53 26 0 Oxamyl 15 Soil 72 0 0 Acetamiprid* 0.5 Stem-paint 72 41 0 Acetamiprid 1.0 83 25 17 Acetamiprid 1.5 89 22 39

* Each dose di luted with an equal amount of water.

9

----------------- - ------ ------

- ----------- --- --------- -- ----- - --- - - ------------

Table 4. Effectiveness (%) of ten insecticides applied on 22 July 1996 as high volume sprays, in combination with Ultra Fine® summer oil (3 cc/l), and of imidacloprid applied with the stem-paint and drench application methods. against CLM infestation in a 5-year-old Valencia orange grove at Akaki

-------------.-,----------_ .. _---------------------------------- ----------------------- ­

Days after treatment Rate

(ccorgf.p. Method of Insecticide /100 I) Application+ 4 II 18 27 43 56 68 79 91 114

Pyriproxyfen 50 S 95 85 32 Imidacloprid 50 S 98 100 31 Abamectin 60 S 98 100 31 Acetamiprid SP 50 S 100 100 96 97 66 46 29 28 Spinosad 50 S 100 100 74 17 Hexat1umuron 150 S 94 99 14 Lufenuron 50 S 92 96 8 Carbosulfan 150 S 100 47 2 Dit1ubenzuron 50 S 80 85 2 Summer oil 300 S 60 63 12 Imadacloprid SL 5 cc/tree SP 48 lOa 100 100 66 57 26 54 8 Imidacloprid SL 10 cc/tree D 23 100 100 100 100 100 48 60 83 72 ----------. --_._-------------------------- ­

+ S= Spray; SP= Stem paint; D= Drench method.

Table 5. Effecti veness (ek) of two insecticides applied at two dosage rates with the stem-paint method against CLM in newly budded (2-year-old) trees at Meneou

Date Rate

Insecticide (cc f.p./bud) 19/6 J/7 17!7 JI/7 14/828/8 11/9 25/9 9/10 23/10 6/1120/114/12 18/12

Imidacloprid 0.4 100 48.6 100 92.0 77.6 98.0 42.6 100 100 96.3 84.3 92.3 69.6 63.3 Imidacloprid 0.6 100 90.3 35.0 100 95.3 88.6 74.6 9 1.0 98.3 lOa 83.3 81.3 80.6 69.0 Acetamiprid 0.4 100 100 87.3 63.0 lao 100 96.3 96.0 98.3 93.3 83.3 86.6 56.3 47.0 Acetamiprid 0.6 100 100 100 97.0 916 100 85.0 100 lOa 100 96.6 91.6 58.3 39.3

--~--.-_._-

*Treatment dates: I. 5/6. 8/7, 15/9; 2. 5/6, 23/7, 15/9; 3. 516 and 5/8; 4. 5/6 and 15/9. Notc: At the application made on 15 September, the dosage rate in treatment No I was 0.5 cc/bud and in treatments 2 and 4, 0.7 cc/bud, due to increased vegetative growth of trees.

method was 54 and 60%, respectively, Imida­ (Table 7). However, two applications of cloprid applied with the drench method pro­ acetamiprid might be sufficient. Application vided protection exceeding three months, of the insecticide at the same or at a different with effectiveness of 83 and 72% recorded at area on the trunk resulted in the same effec­91 and 114 DAT, respectively (Table 4). tiveness of treatment. The cost was about

£0.60/tree or £ 165/ha (270 trees) for 3 appli­Application of insecticides with the stem­ cations. paint method. Three applications of imida­cloprid or two applications of acetamiprid SL (soluble liquid), with the stem paint Table 6. Cost (£) of 3 applications of imidacloprid or two method at 0.4 cc f.p./stem, provided effective applications of acetamiprid (SL) applied with the

stem-paint method to control CLM in newly bud­control (Table 5). The cost of applying these ded trees at Meneou treatments was about £0.86 for imidacloprid (3 applications) and £0.57 for acetamiprid (2 Expenses Imidacloprid Acetamiprid applications) per tree or £232 and £ 154/ha

Cost of insecticide(270 trees), respectively (Table 6). (4.5cc x fO.08/cc) 0.36 0.24

Three applications of imidacloprid or aceta­ Labour * (4 min/tree) 0.50 0.33 miprid SL to 4-year-old Valencia trees at Total cost/tree 0.86 0.57

Total cost/h (270 trees) 232 154Akaki with the stem paint method at 4 cc f.p./tree provided nearly complete control * Cost of I man-hour=£2.5.

10

------ ---- - ------- ---- ----

---- ------- ---- ------------

Table 7. Effectiveness (%) of two insecticides applied at 4 cc f.p./tree with the stem paint application method against CLM in 4-year-old Valencia orange trees at Akaki

Date

Insecticide* 26/6 10/7 24/7 7/8 21/8 4/9 18/9 2110 16110 .'lOll 0 Dill nil I 11/12 23/12

Imidacloprid*" 96.6 98.3 89.3 39.0 100 100 88.7 62.0 100 97.0 78.0 46.5 77.3 48.7 Imidacloprid-r 97.0 98.3 89.3 39.0 100 99 95.3 68.7 98.3 92.7 90.7 91.0 94.3 70.0 Acetamiprid" 100 98.3 87.3 17.7 100 100 98.7 93.3 100 100 lOa 100 100 92.7 Acetamiprid+ 100 98.3 87.3 17.7 100 lOa 100 97.0 100 82.0 92.7 lOa 100 100

Dates of applications for the first 3 insecticides: 11/6, 11/8 and 7110: For the last insecticide 11/6. 11/8. and 31/10: '*Application to the same area: +Application to a different area.

Application of insecticides as high volume (Table 9). The cost of the two treatments of sprays. Two applications of pyriproxyfen this chemical applied at the lower rate (8 cc plus three applications of acetamiprid SP, f.p./tree) was about £l.28/tree or £3451ha each applied in admixture with summer oil, (270 trees), which is twice as high as that of as high volume sprays were necessary for the stem paint method. nearly complete control of eLM. The cost of applying these five sprays was significantly Combination of insecticide application lower than that of the stem-paint method methods. The combination of treatments ap­

plied provided, as expected, excellent control (Table 6), not exceeding £0.30/tree or about of the pest till the end of December. Three £80/ha (Table 8). months after the application of imadocloprid with the drench method, effectiveness re­Application of imidacloprid with the mained at 93.3% (Table 10). The cost of thisdrench method. Two applications of imida­chemical control programme (Table 11) was cloprid were necessary to achieve nearly

complete protection of the young growth of about £1.32/tree or £3501ha (270 trees). The 4-year-old Valencia orange trees. Both rates component with the lowest cost in this pro­tested provided excellent control of the pest gram was the application of a high volume

Table 8. Cost (£/tree) of 2 applications of pyriproxyfen and 3 applications of acetamiprid SP applied as high volume sprays for nearly complete control of CLM in newly budded trees at Meneou

Expense Pyriproxyfen* Acetamiprid

Cost of' insecticide (0.25ce x £0.036 x 2 for pyriproxylen and 0.25cc x £0.08 x 3 for acctamiprid) 0.018 0.06 Cost of summer OW ( 1.5cc x £0.0006 x 2 or 3) 0.002 0.003 Labour++ (£0.04/application/tree) 0.08 0.12 Fuel (tractor ) 0.004 0006 Total 0.104 0.189

Cost/ha (270 trees)= £79; Grand Total: 0.104+0.189= £0.293/tree; * £ 3611; *" £ 80/1+ £ 0.6/1: ++ Cost of I man - hour= £ 2.5.

Table 9. Effectiveness (%) of imidacloprid applied at two dosage rates with the drench application method against CLM in a 4-year-old Valencia orange grove at Akaki

DateRate --------- --------------.-------- --------------- -----­

Insecticide" (cc f.p./tree) 26/6 10/7 24/7 7/8 21/8 4/9 18/9 2110 16/!0 30/10 Dill 27/11 11/12 23/12

Imidac loprid 8 cc 97.0 100 100 100 40.0 85.3 lOa 98.7 100 92.7 72.3 69.0 90.7 87.3 Imidacloprid 12 cc 100 100 100 99.0 100 95.0 100 90.0 91.3 92.7 90.0 72.0 93.3 97.0

"Date of application= 11/6/97 and 1/9/97.

11

Table 10. Effectiveness (%) of two insecticides applied in a combination of three methods to 4-year-old Valencia orange trees at Akaki

Date

Insecticide 26/6 10/7 24/7 7/8 21/8 4/9 18/9 2/10 16/10 30/10 13/11 27/11 11/1223/12

Imidacloprid" .,* 100 100 47.7 Acetamiprid SP 100 100 91.7 Imidacloprid+ 100 100 100 100 96.7 90.3 86.0 93.3

;0 Applied with the Stem-paint method at 4 cc f.p./tree on 11/6/97; q Applied as high volume spray at 0.5 g Lp. + 3 cc summer oill1 on 30/7/97; +Applied with the drench method at 10 cc f.p./tree on 9/9/97.

spray of acetamiprid SP, representing about Of a considerable number of insecticides 9% of the total cost, and the most expensive applied as high volume sprays, in admixture component was the application of imidaclop­ with summer oil, that were very effective rid with the drench application method repre­ against larval infestation of CLM, acetamip­senting about 61 % of the total cost. rid SP and, to a lesser extent, spinosad re­

tained their effectiveness longer. Other in­Pest population dynamics secticides, i.e. imidacloprid SL, abamectin, In general, populations at Akaki were higher lufenuron, pyriproxyfen and hexaflumuron than at Meneou (Fig. 1). However, the popu­ provided much shorter protection (not ex­lation curve was similar at both sites with the ceeding two weeks) and, therefore, if these higher pest populations recorded from mid insecticides were to be used in field applica­June till the end of August. Moderate popu­ tions, more sprays would be required. Cole­lations were recorded in September and Oc­ man (1994) reported that abamectin mixed tober gradually declining to the lowest level with oil has been registered for use against at the end of December. CLM in Florida. However, current recom­

mendations in this State, limit the use of ab­DISCUSSION amectin to 3 applications/year to manage re­

sistance (Knapp, 1995). In Cyprus, summerIn Cyprus, young citrus stock in nurser­oil alone, applied as high volume spray, pro­ies, trees in newly established groves and vided only moderate control at the rate test­newly scaffold-budded trees are practically ed. It is known, however, that petroleumin continuous vegetative growth from spring spray oils control small immobile insects by onwards, and are therefore exposed to CLM suffocation (Beattie, 1990; Davidson et aI.,infestation from the end of May till Decem­1991), and Beattie et al. (1995a) indicated ber. Consequently, a number of insecticide that petroleum oils act as ovipositional deter­applications is required for effective protec­rents to CLM. Acetamiprid SP, which pro­tion, and the most economic combination of vided the longest control, has, like imida­chemicals and methods of application must cloprid, high systemic and transl aminar be sought.

Table 11. Economic analysis of combined application of two insecticides with three application methods for nearly complete control of CLM to 4-year-old Valencia orange trees at Akaki

Cost/tree (£) Insecticide Application Cost Iha Proportion---,----_._---­

method* Insecticide+ LabourH Total (£) ('7e)

Imidacloprid (SP) 0.32 0.08 OAO 108 30 Acetamiprid (SP)+ (S) 0.042 0.08 0.12 32 9 Summer oil Imidacloprid (D) 80 Nil 0.80 216 61 Grand Total (£) 1.32 352 100

-'---- -----------_._---------------- -- ------- -----------,----- ---­

* (SP) = Stem-paint method (4 cc f.p.ltree); (S)=High volume spray (0.5 cc/l+3 cc summer oilll; (D)=Drench method (10 cc/ tree); += £ 80/1; ++= Cost of I man-hour=£2.5.

12

paint method is suitable for protecting young trees, with stems aged t\\'o years or older. in newly planted groves or in newly scaffold­budded trees. Application of these chemicals to very young shoots, Jess than one year old, are phytotoxic as observed in preliminary trials in the laboratory anu in nurseries. From the field trials with 'acetamiprid and imida­cloprid applied with the stem-paint or the drench method, it was also observed that when trees are under water stress. absorption and translocation of the chemicals is drasti­cally rcuuced. Absorption, and increased ef-· fecti veness. were restored after irrigation, It was also observed that insecticides applied with the stem-paint method to trees over three-years-old, (about I cc of the chemical! main branch of the tree) provideu bctter re­sults than the application of the full dose on the main trunk.

In conclusion, chemical control of eLM in young citrus trees can be achieved at a reasonable cost. If biological control and ap­plication of cultural practices in commercial citrus groves requires further strengthening, the usc of acetamiprid SL and imidacloprid SL with the stem paint method or of imida­c10prid SL \\'ith the drench method \vill be 01 great value in an integrated pest managemr2nt program, as these chemicals will control at the same time other serious citrus pests with­out upsetting the ecosystem.

ACKNOWLEDGEMENTS

The authors wish to thank D. Kourris and A. Petrides for their valuable technical assis­tance and P.I. Olvhanos and G.M. Orpha­nides for reviewing the manuscript. Thanks are also due to the Managers of Meneou and Karantokis farms for making available their citrus groves and for providing facilities.

REFERENCES

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Argo\', Y.. and Y. Rossler. J996. Introduction. re­lease and reco\'ery of several exotic natural enemies ror biological control or the citrus leafmineI'. P/n'//licllistis cltre//a. in Israel. P/rvtop(f/([sit/c·;t 24:3:2,-38,

Beattie. G.A.C. 1990. Citrus petroleum spray oils. Agfast H2. AE 5 NSW Agriculture and Fish­eries. Sydney. Australia.

Beattie. G.A.C .. and D. Smith. 1993. Citrus leaf­miner NSW Agric. Agract H2. AE 4 NSW Ag­riculture and Fisheries. Sydney. Australia. 6]1.

Beattie, G.A.C., V. SOIm:onk, D.1\1. Watson. A.D. Clift. and L. Jian~. 1995. Field ev,<!uation of Stcincmcnw CWPocu!'sac tWeiser) (R/I"hdili­duc: Stpl/lcl'I1('{!1utidoc) and selected L'hemi­cals ror control of citrus kafmincr. P/I\'!Io,'­nls//I eltrd/a Stallltllll (Lcpidopter,,: Croci//arlidoc) . .Io/lrt/,,/ A/lstm!iol1 E/lIO/lIO­/ogiwl Sociel\' 34:335-342.

Beattie, G.A.C.. I.M. Liu. D.M. Watson. A.D. Clift. and L. Jiang. J995b. EnluCltion of pe­troleum spray oils and rnlysaccharides ror contrlll or citrus leafminer P/I\-//OCl1illi.1 ei­Ire/I" Stainton (LejJidoptero: Gruell/orlldue). .10/1 mll/ Austra!io/! ElltOlll%glcl// S'liCiC/\, 34:349-35~.

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Heppner. J.B. 1993. Citrus leafl1liner. Phrlloel/islis ei­Irella Stainton (Lcjiidoplcra: Groeillunidac: Phr/­locl/islil/ac). Floridu Dejiurt/l1cl/l Agriclliture ul/d COII.I/I/I/I'r Sen·iei's. EI/Illil/ologr Circular NLJ . .159, 2p

14

20

110

100., 4Il 90>'".!!

'" 80t:: c:i .s 70 4Il

'" Q.

60J Q.

"t:l c: 50'" 4Il

'" ~ 40'" ...J

30 .•....

Figure 1. Population curves of larvae and pupae of eLM per 75 young leaves recorded in the untreated checks of all experiments conducted at Meneou and Akaki from June to December 1997.

action and has rapid and long lasting activity. Both insecticides can be absorbed by the roots and they are said to provide excellent control of other citrus pests such as aphids, whiteflies, thrips and scale insects. Aceta­miprid SP has been recently registered in Cy­prus. Although the retail price of this chemi­cal is high (about £80lkg), it provides effective and economic control of CLM when applied as foliar spray in admixture with summer oil, because a low rate (0.5 gil) is required and only about five sprays need to be applied during the year.

The granular insecticides aldicarb and oxamyl, applied through the soil, failed to provide satisfactory control of CLM under field conditions. On the contrary, imidaclop­rid, applied with the drench application method, provided high levels of effective­ness for a period exceeding three months af­ter treatment, depending on the rate used. Two applications were sufficient for year­round control. However, the cost is about 2.5 times higher than that of 5 applications of acetamiprid SP as high volume sprays for achieving the same level of control. In any case, for successful application of imidaclop­rid with the drench method, its manufactur­ers recommend that the chemical should be applied through the irrigation system, which must be in perfect condition, and the trees must be in full sap flow, well fertilized and irrigated, and free of weeds. Roots must be

healthy and well developed. Results are bet­ter in sandy and sandy loam soils. Applica­tion of the insecticide must be followed by light irrigation to move the chemical to the upper root zone.

Acetamiprid SL and imidacloprid SL ap­plied with the stem-paint method on the trunks, on well developed branches of young trees, or at the base of lignified shoots of newly budded trees, can provide effective protection against CLM attack. For nearly complete control of the pest during the year, two applications of acetamiprid or three ap­plications of imidacloprid are required, with an intermediate cost as compared to foliar spraying or stem-painting.

From the ecological point of view, appli­cation of high volume sprays, which is the preferred method of controlling CLM in sen­sitive young plants, is expected to have some adverse effect on the biological balance. However, considering that no chemical con­trol measures are applied against CLM in producing commercial groves, which nor­mally represent the majority of citrus trees in each area, biological control agents will not be seriously disturbed.

Application of acetamiprid SL or of imidacloprid SL with the stem-paint method, is not expected to have any detrimental ef­fect on beneficial insects or to the ecosystem in general. The same applies to imidacloprid applied with the drench method. The stem­

13

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15

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