Agriculture, Ecosystems and Environment, 21 (1988) 67-83 Elsevier Science Publishers B.V., Amsterdam - - Printed in The Netherlands

67

The Role of P h e r o m o n e s in the M a n a g e m e n t of P i n k B o l l w o r m Infes tat ion in Egypt ian Cotton Fields

M.M. HOSNY

AinShamsUniversi~ Cairo(Egyp~

ABSTRACT

Hosny, M.M., 1988. The role of pheromones in the management of pink bollworm infestation in Egyptian cotton fields. Agric. Ecosystems Environ., 21: 67-83.

In Egypt, season-long control of pink bollworm (Pectinophora gossypiella) has been accom- plished with 3-4 applications of the pheromone, Gossyplure.

Gossyplure applied at the pin-square stage of the cotton plant is achieving control by mating disruption comparable to 3-5 applications of broad-spectrum chemical insecticides. This has re- sulted in the abolition of all chemical-insecticide treatments in some pheromone-treated cotton fields, and in a reduction of up to three pesticide applications in the areas where the spiny boll- worm (Earias insulana) infestation is common or where the pink bollworm infestation is excep- tionally high. In the latter areas, a single insecticide treatment at the end of the cotton-growing season (when beneficial insects are no longer abundant) is applied for suppressing bollworm populations.

The area of cotton treated commercially with Pectinophora pheromone is continually rising in Egypt and in 1986 about 20 000 ha have been treated with three formulations. By the time of preparing this report on 10 September, 1986, most of the data and results of this season were either still coming in or awaiting analysis. However, some of the 1986 preliminary results are included in this report.

INTRODUCTION

Co t ton in E g y p t is a s ta te -cont ro l led crop. G o v e r n m e n t cont ro l of co t ton p roduc t ion and m a r k e t i n g via coopera t ives s t a r t ed in the 1950s, when consol- ida ted blocks of co t t on receiving insect icide appl ica t ions were first t r ied in the land reform areas. An ou tb reak of co t t on leafworm (Spodoptera littoralis) in- fes ta t ions in 1961 was a major fac tor in ex tend ing the coopera t ive sys tem to the whole c o u n t r y in 1963, and co t ton -pes t con t ro l t hen came to be regarded as a major g o v e r n m e n t responsibi l i ty. Pes t cont ro l in co t t on accoun t s for abou t 70% of agr icul tura l use of pest icides (Hosny , 1980), which are very largely appl ied by aircraft .

68

The Ministry of Agriculture's annual expenditure on cotton insecticides and their application is about US$100 million; 85% of which can be attributed to control of bollworms, mainly pink bollworm. Because cotton is a "government crop" farmers' cotton plantings are consolidated in contiguous blocks, to fa- cilitate measurement, supervision and especially pest control.

Against a background of economic disincentives for cotton production, cot- ton-yield gains are noteworthy. These have been attributed to the effectiveness of cotton-pest control programmes, though it should be pointed out that other factors are also likely to have contributed.

DEVELOPMENT OF COTTON AREA AND PRODUCTION IN EGYPT

In the early 1950s (1950-1952) cotton accounted for almost two thirds (65%) of all summer-cropped land in Egypt and almost one third (30%) of the total annual agricultural labour use. By the early 1980s (1980-1982) cotton's share of the summer-cropped area had fallen (65% (1 400 000 ha) to 21% (45 000 ha)) and its labour use to less than 15% of the total annual farm labour input. Yet cotton production in absolute terms and its contribution to agricultural and industrial exports has been sustained to a substantial degree, notwith- standing an increase in domestic utilisation of cotton.

Despite the area of cotton being almost halved during the last three decades, average production in 1980-1982 was only 7% down on that in 1950-1952 (yield increases largely sustaining output) as appears from the statistics below (Heb- blethwaite, 1984).

Seedco~on yield Index

1950-1952 average 1585 100 1980-1982 average 2827 178

CONVENTIONAL CONTROL OF COTTON PESTS IN EGYPT

Until the late 1960s, government-directed cotton-pest control programmes, implemented through the cooperatives, consisted of manual removal of egg masses of cotton leafworm (Spodoptera littoralis) by children in June (still a common practice today) and of ground application of insecticides against leaf- worm and bollworm larvae. The introduction of aerial spraying under govern- ment control in the late 1960s reinforced state responsibility in cotton-pest control. On average, 4-5 protective aerial insecticidal sprays are applied per season, the first in early July, irrespective of pest populations, for managerial simplicity. In addition, local ground spraying is undertaken: (1) against early season sucking pests (aphids, thrips, spider mites etc.); (2) against sporadic

69

infestations by cutworms (Agrotis and Spodoptera); (3) where aerial spraying is not practical.

In addition to control of cotton pests through insecticides and handpicking of cotton leafworm (Spodoptera littoralis) egg masses, cultural practices are also followed. Irrigation of berseem (clover) after 10 May is prohibited by law, to reduce the carry over of leafworm to cotton. Legal at tempts have also been made to encourage the destruction of cotton crop stalks and residues and hence the carry over of pink bollworm larvae in diapause, but these at tempts have not been successful so far.

Because of the widespread use of insecticides on cotton during the last 25 years, there have been certain factors favouring the consideration of any new non-insecticidal practices which may become available. One important factor is the concern over the harmful side effects of insecticide use and over the need to rotate and replace insecticides, with the possibility of becoming caught on the "insecticide treadmill" of ever more frequent use and replacement in as- sociation with a loss of control over pests. Another factor is that alternative new pest-control methods have begun to become available. One such method is the use of pheromones.

DEVELOPMENT OF PINK BOLLWORM CONTROL BY PHEROMONES IN EGYPT

After 4 years of experimentation and field trials (1980-1983) Egypt became the first developing country to use pheromones commercially for the control of the pink bollworm (since 1984). The trials that led to that step were carried out through a collaborative project between the Academy of Science and Tech- nology of Egypt, Ain Shams University, Cairo and the Overseas Development Administration of the U.K.

1980

In 1980, two formulations of the synthetic PBW pheromone "gossyplure" (1:1 (Z,Z), (Z,E)-7,11-hexadecadienyl acetate) were used in small plots in the Governorate of Fayoum (100 km SSW of Cairo). The I.C.I. microencapsulated formulation (a 2% a.i. aqueous suspension of polyurea microcapsules) was applied, by knapsack sprayers, at the rates of 10 and 20 g a.i. h a - 1. The Albany hollow-fibres formulation (Nomate PBW) was applied, by hand, at rates of 11.2 and 22.3 g a.i. h a - 1. Mating disruption was measured by male-moth catches in funnel-type traps baited with gossyplure hollow fibres. The hollow-fibre formulation caused 94% reduction in trap catches for nearly 4 weeks when applied at 8 fibres m-2 (11.2 g a.i. ha-1) , and 99% reduction when applied at 16 fibres m -2 (22.4 g a.i. ha -1) over the same period (Fig. 1).

The microencapsulated formulation caused similar reductions in trap catches (Fig. 2). Mean catches in the untreated plots were high, a maximum of 171 moths being caught per night (Hall et al., 1982 ).

70

u

0 ~ .

E &

E~

150

100

50

0 5 10 15 2o 25 days after application

Fig. 1. Communication disruption of Pectinophora gossypiella in 0.01-ha plots in Egypt with 'NoMate PBW" hollow fibres applied at 16 fibres m -2 22.4 g a.i. ha -1. Key: control (O); treat- ment ( • ).

150 c ~

c -

5_7= ~0

o

E. ~.

5o

0 0 5 10 15 2o 25

days after spraying Fig. 2. Communication disruption of Peetinophora gossypieUa in 0.01-ha plots in Egypt with microencapsulated pheromone applied at 20 g a.i. ha-1. Key: control (©); treatment ( • ) .

1981

In 1981, four almost similar cotton fields, each of approximately 50 ha, were selected, again in Fayoum, as experimental sites. The sites were arranged in two pairs separated by about 30 km. The sites within each pair were about 1 km apart, and one site was treated, aerially, with the I.C.I. microencapsulated formulation (2% a.i.) at the rate of 10 g a.i. (25 1 of the diluted suspesion) per hectare. The other "control" site was given the recommended t rea tment with conventional insecticides.

In tha t year (1981), several criteria were used for assessing the efficacy of the pheromone and insecticide treatments. Samples of mature green bolls were examined for evidence of pink and spiny bollworm attack. Green boll sampling is done as a mat ter of routine in Egypt, and is a reasonably accurate indicator of both pink and spiny bollworm infestations, the damage caused by these two

71

species being easily discernible from one another. Adult male moths were mon- itored using pheromone-baited funnel traps put out at a density of one trap per 10 ha. Results showed that the percentages of bolls infested with PBW larvae were essentially similar within each pair of sites. Most important from the farmer's point of view, no reductions in yield of seed cotton were recorded in the treatment sites (Critchely et al., 1983). Moth-trap catches in the phero- mone-treated areas fell to zero after the first application and stayed mostly at this level in the two pheromone-treated sites at the end of the season, the increase in catches was delayed by at least 5 weeks when compared to the adjacent insecticide-treated sites.

1982

Three pheromone formulations (I.C.I. microcapsules, Albany hollow fibres and B.A.S.F. laminate flakes) were applied in 1982, each in a 50-ha cotton area in the Governorate of Fayoum. The microcapsules were applied aerially (by a Bell 47-5 helicopter) while both the fibres and flakes were applied by hand (one boy completed one hectare in 1-2 days).

Mean nightly moth catches in the pheromone traps were very low in the pheromone-treated areas compared with those in the insecticide-treated areas.

Analysis of variance of the percentage infestations of cotton bolls by pink bollworm larvae showed no significant differences for any of the three phero- mone formulations when compared with their respective insecticide-treated area, at P = 0.05 (Critchely et al., 1985 ).

The numbers of insect predators found in pheromone-treated cotton were more than three times those in insecticide-treated cotton (Table 1). Average yield of seed cotton from the pheromone-treated sites was either equal to or slightly higher than in the insecticide-treated area (Fig. 3).

1983

The pheromone trial area was increased to 150-200 ha for each formulation in Fayoum, in addition to another 100-200 ha per formulation in the adjoining Governorate of Beni-Suef. Table 2 summarizes the data and results of the three Fayoum experimental districts. The results of the Beni-Suef trials were as promising as the Fayoum results, and, together, were instrumental in inducing the Egyptian Ministry of Agriculture to use pheromones, commercially, in 5000 ha of cotton at Fayoum and Beni-Suef for the control of pink bollworm infes- tation during 1984.

72

TABLE 1

Numbers of predatory insects per hectare sampled by D-Vac suction apparatus from pheromone- treated and insecticide-treated sites in mid-and south Fayoum, 18 August 19821

Species Insecticide -treated Pheromone -treated

Biahmo Bandarel Mean E1A'lam Abgig Menshat Mean Fayoum Rahmi

Coccinellid adults 33 Poederus adults 0 Scymnus adults 33 Chrysoperla adults 33 Chrysoperla larvae 0 Orius adults 433 Total predators 532

33 33 333 33 0 122 33 17 967 0 0 322 33 33 100 33 33 55

167 100 300 533 1234 689 33 17 0 167 33 67

667 550 567 1934 934 1145 966 749 2267 2700 2234 2400

1After Critchely et al. (1985)

35O0

30O0

2500 J c

"-2000

500 c -

"~ 1000 --$

>-500

0

I~ Pheromone t reotmen ' l O Insec t i c i de t r ea tmen t

AB CD EF5

Fig. 3. Average yield of seedcotton in pheromone- and insecticide-treated areas (Fayoum 1982) (A) F I.C.I. pheromone (microcaps); (B) (D) g insecticides; (C) B.A.S.F. pheromone (flakes); (E) Albany pheromone (fibres).

1984

T h e to t a l a r ea of co t t on t r e a t e d in 1984 wi th P B W p h e r o m o n e s , on a com- merc ia l bas is , was 4400 ha. T h i s a r ea was d i s t r i bu t ed in t h r ee dis t r ic ts , two in B e n i - S u e f a n d one in F a y o u m , as follows:

(1) 2000 h a in t he d i s t r ic t of I h n a s i a ( B e n i - S u e f G o b e r n o r a t e ) t r e a t e d wi th t he hol low-f ibre p h e r o m o n e f o r m u l a t i o n " N o M a t e P B W " ( p u r c h a s e d f r o m Sandoz Ltd. , S wi t ze r l and ) . T h e ra te of app l i ca t i on was 37.5 g of the f ibres ( c o n t a i n i n g 3 g a.i. ), m i x e d wi th 250 g of I ndopo l glue, pe r hec t a r e (each f ibre is 1.5 c m long wi th a n i n t e r n a l d i a m e t e r o f 0.2 m m ) . T h e p h e r o m o n e is he ld in the f ibres by cap i l l a ry ac t ion a n d is re leased by e v a p o r a t i o n f r o m the open e n d ( B r o o k s e t al., 1979). A f ixed wing "Ai r T r a c t o r " a i r c ra f t was used in dis t r ib-

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74

uting the fibres through a pair of specially-designed applicators (Furkhouser and Las, 1981 ), one attached to each wing. The dates of the four treatments of this formulation were 26 June, 15 July, 5 August and 26 August.

(2) 400 ha in the district of E1 Wasta (Nei-Suef Governorate) treated with the laminated-flake formulation produced by B.A.S.F. of F.R.G. Each flake is a 3-layered dispenser (3 × 3 mm in size) and consists of a reservoir layer im- pregnated with pheromone sandwiched between two protective layers of plas- tic. The pheromone is released from the edges of the flake and by diffusion through the protective layers (Quisumbing and Kydonieus, 1982 ) A fixed-wing aircraft was used in distributing this formulation at the rate of 150 g (contain- ing 7.5 g a.i. ) mixed with 140 g of the adhesive "Biotac" per hectare. A pair of special applicators, one on each wing, was used for the application of the flake- sticker mixture. Application dates of the 4 treatments were 14 June, 27 June, 18 July and 7 August.

(3) 2000 ha in the district of Sinnoris (Fayoum Governorate) sprayed 4 times with the I.C.I. microencapsulated pheromone formulation, a stabilized aqueous suspension of polyurea microcapsules containing 2% a.i. Application rate was 500 cc of the formulation per hectare (containing 10 g a.i. ha-1) di- luted with water to give a nominal application rate of 25 1 ha- 1. During appli- cation the aircraft (a helicopter) flew so that the nozzles were about 3 m above the crop canopy to ensure an even distribution of the material (droplet size 240-300 tt v.m.d. ) and to reduce evaporation and windborne spray drift. The first treatment was started on 9 June, the second on 2 July, the third on 21 July and the fourth on 14 August. Standard Delta traps were positioned in all the above pheromone-treated areas as well as in nearby insecticide-treated fields, at the rate of one trap per 40 ha, to compare catches of male moths and to evaluate and time the treatment. Boll sampling was started by early July and continued, at weekly intervals, until the end of August.

Results of 1984

Table 3 summarizes the results of the bollworm infestation (averages of 8 samples) in green bolls from both pheromone- and insecticide-treated fields in the three treatment areas of 1984. The corresponding yield weight averages in each case are also shown in the table. On the whole, comparisons indicated that adequate levels of control were achieved with all three pheromone for- mulations which were at least as effective as the insecticide sprays. This en- couraged the Ministry of Agriculture to agree to double the area to be treated, commercially, with PBW pheromone in the following season (1985). Fayoum and Beni-Suef Governorates were chosen, again, for the 1985 treatments. In the meantime, it was decided that large-scale field trials should be started in that year (1985) in one of the main cotton-producing governorates in the Delta (Dakahleya Governorate).

75

TABLE 3

Average boll worm infestation from samples of 100 cotton bolls, and yield of seed cotton from insecticide- and pheromone-treated fields at 3 locations in 1984

El Wasta Inhasia E1 Fayoum

Insecticides Pheromones Insecticides Pheromones Insecticides Pheromones (B.A.S.F.) (Sandoz) (I.C.I.)

Total boll-worm 7.93 5.48 6.59 3.85 2.72 3.49 infestation ( % ) Spiny boll-worm 1.17 0.69 0.67 0.87 0.99 1.95 infestation ( % ) Yield of seed 2185.3 2635.2 1649.3 1461.9 1825.5 2072.9 cotton (kg(ha-1))

The 1985 commercial applications

The total area treated, commercially, with PBW pheromone in 1985 was 8140 ha distributed as follows: (1) 3540 ha in Fayoum and 1400 ha in Beni- Suef treated with the I.C.I. formulation (microcaps); (2) 1200 ha in Beni-Suef treated with B.A.S.F. formulation (laminate flakes); (3) 2000 ha in Beni-Suef treated with the Sandoz formulation "No Mate" (hollow fibres).

In other words, all three formulations were used, during 1985, in Beni-Suef whereas only one of them (I.C.I.) was used in Fayoum. However, the number of treatments, doses, dates, evaluation etc. were practically the same in 1985 as in 1984 except for a few minor details. Fixed-wing aircrafts were the means of application at Beni-Suef for pheromones and conventional insecticides.

Results of 1985

Table 4 shows a comparison between the area treated in one flight and the application time for the different pheromone and insecticide treatments. Fac- tors to be considered in such a comparison, hence an economic appraisal of pheromone and insecticide application, include the area which can be treated with a single payload and the time involved, both in treatment and turnround. These are indicated in Table 4 which shows the similarity between the mi- croencapsulated pheromone formulation and insecticides, where both are ap- plied in high volumes of water. The laminate-flake and hollow-fibre formulations, by contrast, are applied with small quantities of adhesive to en- sure adherence to the foliage and weigh less for a given area of application, thus a larger area can be covered by a single payload.

The cost of pheromone and insecticide aerial application was fixed at L.E. 18.00 per ha for four applications, with no allowance made for the different

76

TABLE 4

The area treated in one flight and the t reatment t ime for 3 PBW pheromone formulations and conventional insecticides using an air Tractor aircraft (Beni-Suef, 1985)

B.A.S.F. Sandoz I.C.I. Insecticides Laminate flakes Hollow fibres Microcaps

Av. no. of ha treated in 200 one flight

Flight t ime per load 75 ( min )

Aircraft reloading 5 ( min )

130 50 50

60 30 30

5 15 15

U.I rr 0 .75

D c~ u3 ~ o.6o U.I

U ' ) Z

0 c ~ - 0.30

( D

gg o.15 C:) z:l::

INSECTICIDES

,-., BASF ,..(,."" • ~ ..tk ~ . . . r o . ¢ , : . ."

. o . . . . . 1

,. ..... SA NDOZ / " f

.,.J Cl / /

_ I i I | |

A U G U S T 1985

Fig, 4. Average number of individuals of red spider mites (Tetranychus urticae and T. cucurbi- taearum) per square inch of cotton leaves in insecticide- and pheromone-treated fields at Beni- suef Governorate.

products. Differences were evident, however, in costs of pheromones versus insecticides. Insecticides varied in price from L.E. 22.00 to L.E. 34.00 per ha giving an average seasonal total of L.E. 135.00.

The price of the pheromones, however, was fixed at L.E. 25.00 per ha (sea- sonal total L.E. 100.00). Overall seasonal totals were, accordingly, L.E. 153.00 and L.E. 118.00 per ha for insecticides and pheromones, respectively.

Weekly counts were made, in August 1985, of red spider mites on cotton leaves in pheromone- and insecticide-treated fields at Beni-Suef. Populations of red mites are known to respond quickly and negatively to variations in their predacious natural enemies. Figure 4 shows the average number of individuals

77

of two red spider mite species, Tetranychus urticae and T. cucurbitacearum per square inch of cotton leaves sampled during August 1985 from insecticide and pheromone-treated fields. As appears from the figure, the population level of spider mites in pheromone-treated fields was only a third to a quarter its level in insecticide-treated fields. The reduction could be attributed to the increased activity and abundance of predators which, in an earlier study conducted dur- ing August 1983 at Fayoum (Critchely et al., 1985 ), were found to be about 3- 4 times as many in pheromone-treated as in insecticide-treated cotton (Table I).

The bollworm infestation percentages and the yield averages were insignif- icantly different in all treatment sites either at Beni-Suef or Fayoum.

The 1985 trials in Dakahleya

Ever since the first large-scale trials with pink bollworm pheromone in 1981 in Fayoum, there was a feeling that while pheromones might succeed in rela- tively-isolated agricultural areas of Fayoum and the narrow band of cultiva- tions along the Nile in Middle and Upper Egypt, they would not stand up to the pest challenge in the large agricultural area of the Delta. To put that theory to the test it was decided that hollow-fibre, laminate-flake and microencap- sulated formulations of the PBW synthetic sex pheromone be applied aerially in large-scale trials at Dakahleya in the Delta region of Egypt in 1985. Accord- ingly, 100 ha blocks of cotton were treated at regular intervals throughout the season as the sole means of controlling the pest and compared with a 100 ha block of cotton sited in the same locality which was treated aerially with con- ventional insecticide spray applications.

The amounts of hollow-fibre and laminate-flake formulation approximated to application rates of 3 and 7 g a.i. ha - 1 while the microencapsulated formu- lation was sprayed at the rate of 10 g a.i. ha-1. A number of criteria (monitor- ing pheromone trap catches, boll infestation, yields of seed cotton, beneficial arthropods etc. ) were used for assessing the efficacies of the pheromone and insecticide treatment.

Results indicated that in all pheromone-treated areas moth catches were greatly reduced following treatment compared with those in the insecticide- treated areas.

Comparisons of the percentage infestation of cotton bolls by the PBW larvae in the pheromone and insecticide-treated blocks have shown that in none of the areas did boll infestation reach significantly damaging levels (usually taken as around 10% ). Statistical analysis of the season's data revealed practically no significant difference between treatments (Fig. 5).

This was reflected in the generally high yields of seed cotton (3350-3550 kg ha-1) as appears from Fig. 6.

There were nearly 8 times as many beneficial arthropods found in the areas

78

t - O

L~

2,

1.

Microcops

I i i In'.s¢ct- SiNDOZ 19ASF SiNDOZ iciaes hollow Laminate hollow

fibres fibres B A

Fig. 5. Mean percentage infestation of cotton bolls by pink bollworm in pheromone- and insecti- cide-treated fields. Dakahleya Province (mean of 10 samples: 27 July-28 September 1985 in each case).

t reated with hollow-fibre and microencapsulated pheromone formulations as in the insecticide-treated area (Table 5). Tha t there were only three times as many beneficials in the area treated with the laminate-flake formulation com- pared with insecticide-treated area might be at t r ibuted to the application of the carbamate insecticide "Lanna te" on 24 June and 13 July to control a cotton leafworm infestation.

The above results reflect the obvious success of pheromones in the large scale trials in the Delta in 1985. This success motivated the Ministry of Agri- culture not only to increase the cotton area to be treated, commercially, with pheromones to 20 000 ha in 1986, but also to have most of this 20 000 ha in the Delta.

3500

-~ 3CO0

E E 293O

o 2O3O v

c

Laminate flake hollow microencaps insecticides fibre

pheromone formulations

Fig. 6. Average yield of seed cotton in pheromone- and insecticide-treated areas, Dakahleya Gov- ernorate 1985.

79

TABLE 5

Numbers of beneficial arthopods sampled by sweep net from pheromone- and insecticide-treated areas during June-September 1985 in Dakahleya

Months Pheromone-treated cotton Insecticide-treated cotton

B.A.S.F. I.C.I. Sandoz laminate- microcaps hollow- flakes fibres

June 1574 3042 2986 24771 July 4482 2734 2656 382 August 1766 3993 4123 434 September 2832 4694 4962 801

1Prior to insecticide application. 2Sprayed twice with "Lannate" (on 24 June and 13 July) for control of cotton leafworm (Spo- doptera littoralis ) infestation.

The 1986 commercial applications

During the last 2 years, commercial applications have been confined to the Governorates of Fayoum and Beni-Suef. In 1986, however, the areas treated with the same three formulations, totalling 20 000 ha, were mostly in the main Egyptian cotton-growing area of the Delta at selected districts within the gov- ernorates of Gharbeya (5000 ha), Menoufeya (5000 ha), Sharkeya {4000 ha) and Kalubeya ( 3000 ha). The pheromone- t reated area in Fayoum was approx- imately 2000 ha. Five types of aircraft (Air Tractor 400, Ayres Turbo Thrush, Cessna Husky, Cessena Agtruck and Kruk 106) undertook the pheromone (and insecticide ) applications in the Delta governorates. Rates were the same as in 1985. The dates of the first application were, on average, 2-3 weeks late. Sub- sequent applications were at intervals of 2-3 weeks.

In 1986 further large scale experimental trials were also conducted to eval- uate the following: (1) The Mitsubishi "rope" or "twist- t ie" Pectinophora pheromone formulation (in 350 ha in Sharkeya) , applied by hand at the rate of one dispenser (containing 36 mg a.i.) 10 m -2 (i.e. 1000 dispensers contain- ing 36 g a.i. ha -1) (one boy completed one hectare in 2 days); (2) The new pheromone of the spiny bollworm Earias insulana formulated in both hollow fibres and twist-tie ropes (in 350 ha at Fayoum); (3) The I.C.I. microencap- sulated Pectinophora pheromone formulation at a reduced spray volume of 12.5 1 ha -1 (in 350 ha in Kalubeya) .

1986 Results (to date)

The usual criteria for assessing the efficacies of the different pheromone treatments , such as moth monitoring by pheromone traps, comparisons of the

8O

TABLE 6

Development of bollworm infestation in some cotton fields treated with PBW pheromone and conventional insecticides (Fayoum Governorate, 1986)

District Saiedeya-Sanhour Biahmo E1 A'lam Sandoz hollow fibres I.C.I. microcaps • insecticides

Area (ha) 1280 745 100 Dates of treatment 17 June 16 June 25 June

6 July 5 July 12 July 19 July 19 July 28 July

4 August 20 August

Infestation in green bolls (%) sampled on: 26 June 1.0 1.0 2.0 5 July 2.0 2.0 2.0

13 July 3.0 2.5 2.5 21 July 8.0 6.5 5.0 28 July 9.01 11.01 12.0 6 August 12.5 15.0 10.0

14 August 14.0 15.0 14.0 Total 49.5 52.5 47.5 Mean 7.1 7.5 6.8

1In view of these rather high infestations, local agricultural authorities insisted on having all pheromone-treated areas sprayed with insecticides as soon as possible. Insecticide spraying was started in the ICI-pheromone fields on 28 July and in the Sandoz-pheromone fields on 30 July, thus limiting the pheromone applications to only 3 in Fayoum Governorate.

percentage infestations of cot ton bolls etc., were used in 1986. By the t ime of preparing this report, on 10 September 1986, most of the data and results for this season were ei ther still coming in or awaiting analysis. However, the re- sults shown below can be presented at this stage.

(1) Table 6 summarizes the data and boll infestation percentages per ta ining to applications in the Fayoum area. Only three of the four scheduled applica- t ions were applied in tha t region in 1986. The rapid development of bollworm infestat ions by the end of July caused the local agricultural authori t ies of Fay- oum to spray all pheromone- t rea ted fields with conventional insecticides.

Insecticides were also applied in the pheromone- t rea ted areas of the Delta, s tart ing on 8 August in Kalubeya (the microencapsulated formulat ion area), then in Gharbeya on 12 August (hollow-fibre and laminate-flake formula- t ions) , on 18 August in Sharkeya (hollow-fibre and laminate-flake formula- t ions) , and finally on 21-23 August in Menoufeya (laminate-flake and hollow- fibre formulat ions) . However, all of the pheromone area in Menoufeya re- ceived the four scheduled applications of pheromone before the onset of insec- ticide spraying.

( 2 ) Table 7 gives the data and results of the Menoufeya applications.

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TABLE7

Development of bollworm infestation in green cotton bolls sampled from fields treated with PBW pheromone and with conventional insecticides

District Quesna Quesna Shebin E1 Kam E1 bagour Sandoz hollow- B.A.S.F. laminate- B.A.S.F. laminate- Insecticides fibres flakes flakes

Area (ha) 2000 1935 1205 500 Dates of treatment 21 June 18 June 24 June 5 July

10 July 8 July 10 July 22 July 2 Aug 30 July 1 Aug 10 Aug

17 Aug 17 Aug 17 Aug 27 Aug Infestation in green bolls (%) samples on:

9 July 0.6 1.0 1.1 2.4 16 July 1.7 1.5 2.7 4.7 23 July 1.2 0.7 1.7 2.4 30 July 2.7 3.2 4.3 7.5 6 Aug 4.6 3.6 6.6 12.5

13 Aug 5.3 8.8 7.1 10.6 20 Aug 7.6 5.5 10.41 6.1 27 Aug 10.5 9.9 9.8 7.0

Mean 4.6 4.6 5.5 6.7

1In view of this rather high percentage of infestation the agricultural authorities in Menoufeya decided on having all pheromone areas in that Governorate sprayed with conventional insecticides as soon as possible. This was carried out on 21-23 August.

Both Tables 6 and 7 infer tha t effective control of mating within the pher- omone- t rea ted areas was mainta ined unti l late July in Fayoum and up to mid- August in the Delta. After this, substantial numbers of moths were caught in the pheromone traps and it was assumed tha t mating disruption was no longer achieved. Late-season infestat ions of bolls were correspondingly high in the pheromone- t rea ted fields, but they were also equally high in the fields t reated with insecticides; and the differences between means were insignificant.

The apparent increase in boll infestat ion in August is caused by a decrease in the number of green bolls susceptible to insect a t tack towards the end of the season, giving a higher percentage figure for the infestation, and also by the fact tha t these bolls represent the least impor tan t par t of the crop (Pearson, 1958). Thus boll-damage assessments af ter mid-August and up to harvest have little economic significance.

(3) Pre l iminary results of the field trials with the Mitsubishi P B W phero- mone dispensers (ropes or twist-ties) in Sharkeya indicate tha t this formula- t ion gave a very high level of disruption. For 7 weeks after first application {by hand) trap catches were practically zero and boll infestat ion did not exceed 5% as against 12-16% in adjacent insecticide-treated areas. This could be due to the effect of a high rate of active ingredient (36 g ha -1 ) in the initial appli-

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cation of the Mitsubishi formulation. A similar effect was observed in 1980 when the hollow-fibres were applied, in Fayoum, at more than 7 times the present rate, and the microcapsules at twice the present rate. Complete dis- ruption, as measured by moth-trap catches, was achieved for 4 weeks (Figs. 1 and 2) and would probably have continued for a longer period had the trials not been stopped after 28 days.

(4) The trials in Kalubeya in which the microencapsulated formulation was applied at 12.5 I ha -1 instead of the regular 25 I ha -1 appeared to be quite promising. In the trial area (400 ha ) boll infestations reached only 6.6% during the first week of August, just before insecticidal spraying, as compared with 9.9% in the nearby areas treated with insecticides. Although this was a large- scale trial it was unreplicated and should, therefore, be repeated in 1987 but in replicated plots of at least 100 ha each.

(5) The trials carried out for the control of the spiny bollworm using pher- omone suffered from organisational and technical problems which reduced the value of the data obtained. However, if these problems can be overcome, the trials should be repeated in 4 replicated plots of 100 ha each.

DISCUSSION AND CONCLUSIONS

Since the use of pheromones to achieve mating disruption is most effective when populations are low (Hagstrum and Davis, 1981 ), so application early in the season is necessary to prevent a build-up in the population. In selected areas of Egypt the primary objective is to use only pheromones for the control of PBW. However, it is accepted that in some areas, for various reasons (highi infestation, poor application etc.) it may be necessary to use insecticides, as happened in 1986.

The present extensive use of aircraft for application of insecticides in Egypt can easily be adapted to control strategies based on pheromones since area- wide application of the formulation in a short time is possible. An alternative to aerial application could be hand application of pheromones by the same labour force that is employed in collection of Spodoptera littoralis egg-masses. This, however, might be affected, in the future, by changes in the relative cost of aerial application and labour.

Wide fluctuations of field temperature, ranging between 20 and 46 ° C, occur during the treatment programme. Since temperature affects the emission rate of the pheromone active ingredient, the range of field temperatures must be taken into account in the formulation design. Tests have shown that some dispensers are more effective in controlling emission rate over varying tem- peratures, thus preventing large increases in pheromone release when field temperatures become very high.

Work in the U.S.A. (Lyle Gaston, personal communication) has suggested that a 3:2 ratio of the Z,Z to Z,E isomers of "gossyplure" rather than the I:I

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ratio at present in use may provide a more effective compound for mating dis- rupt ion of PBW.

Bet ter results have also been demonstrated, in the present report, by appli- cation of higher levels of pheromone a.i. h a - 1. It would thus appear that , in future years, we may be presented with a slightly altered ratio of the most effective compounds of the P B W pheromones and with higher doses per ha than applied now. This may provide bet ter mating disruption and hence con- trol of the insect.

The pheromonal control strategy for 1987 is expected to include technical and organisational measures to avoid the difficulties encountered in 1986. Un- til suitable mathemat ical models are prepared, t imings of applications should be more closely controlled, for example the first should begin when the cot ton is at the pin-square stage or 85 days after plant ing (i.e. by late May or early June) , with the second following after 14 days. The third and fourth treat- ments should then be applied after intervals of 20 days.

REFERENCES

Brooks, T.W., Doane, C.C. and Staten, R.T., 1979. Experience with the first commercial phero- mone communication disruptive for suppression of an agricultural pest. In: Ritter, F.J. (Edi- tor), Chemical Ecology : Odour Communication in Animals. Elsevier, Amsterdam, pp. 375- 388.

Critchely, B.R., Campion, D.G., McVeigh, L.J., Hunter-Jones, P., Hall, D.R., Cork, A., Nesbitt, B.F., Marrs, G.J., Jutsum, A.R., Hosny, M.M. and Nasr, E.A, 1983. Control of pink bollworm, Pectinophora gosspiella (Saunders) (Lepidoptera: Geleichiidae), in Egypt by mating disrup- tion using an aerially applied microencapsulated pheromone formulation. Bull. Entomol. IRes., 73: 289-299.

Critchely, B.R., Campion, D.G., McVeigh, L.J., McVeigh, E.M., Cavanah, G.G., Hosny, M.M., Nasr, E.A., Khidr, A.A. and Naguib, M., 1985. Control of pink bollworm, Pectinophora gos- sypieUa (Saunders) (Lepidoptera: Gelechiidae ), in Egypt by mating disruption using hollow- fibre, laminate-flake and microencapsulated formulations of synthetic pheromone, Bull. En- tomol. Res., 75: 329-345.

Furkhouser, W.A. and Las, A.S., 1981. Aerial dissemination of insect pheromones; in Proc. Winter Meeting of American Society of Agricultural Engineers, Chicago.

Hagstrum, D.W. and Davis, Jr., L.R., 1982. Mate-seeking behavior and reduced mating by Ephes- tia cauteUa (Walker) in a sex pheromone-permeated atmosphere. J. Chem. Ecol., 8: 507-515.

Hall, D.R., Nesbitt, B.F., Marts, G.J., Green, A.St.J., Campion, D.G. and Critchely, B.R., 1982. Development of microencapsulated pheromone formulations. In: B.A. Leonhardt and M. Be- roza {Editors), Insect Pheromone Technology; Chemistry and Applications. American Chem- ical Society, Washington, DC. ACS Syrup. Set., No. 190, pp. 131-143.

Hebblethwaite, M.J., 1984. An economic assessment of pheromones in cotton pest control in Egypt. Tropical Development and Research Institute report No. 1224 (R), London.

Hosny, M.M., 1980. The control of cotton pests in Egypt. Outlook Agric., 10 (4): 204-205. Pearson, E.O., 1958. The Insect Pests of Cotton in Tropical Africa, London, Emp. Cott. Gr. Corp

and Commonw. Inst. Entomol., 355 pp. Quisumbing, A.R. and Kydonieus, A.F., 1982. Laminated structure dispensers, In: A.F. Kydonieus

and M. Beroza (Editors), Insect Suppression with Controlled Release Pheromone Systems. Vol. I. CRC Press, Boca Raton, FL, pp. 213-210.