Ecological Studies On Boll Worms And Effect Of Some New Methods In Their Control:

Karima Abd El-rhman El-lebody

SUMMARYThe present study aims to investigate the effect of ecological factors(biotic and abiotic) on the pdiapaused pink bollworm (PBW), Pectinophoragossyplella (Saunders) larvae, the biological and histological effects of the bioinsecticide(Xentari) against the spiny bollworm (SPW), Earlas lnsulana(Boisd.) larvae; and evaluation of certain control programs against cottonbollwonns. The obtained results revealed the following:I. Studies on the dipaused larvae of the pink bollworm (Pectinophoral1ossypiella) seasons :1.1- The excluded dipaused larvae from cotton seeds during the rest periodseolt~ (H’Jof 1994/95 and 1995/9~The excluded P. gossypiella resting larvae from cotton seeds wereclassified to dead larvae (266 & 108) and alive larvae (140 & 169) during therest period of both years 1994 - 95 and 1995· 96, respectively.Follow-up the excluded alive larvae obtained from the cotton seeds. during 95 & % years revealed that some of these larvae reached to the adultstage (78.57, % & 55.03 o/~respectively), while 21.43 %& 44.97 % of the”,died either as larvae or pupae. However, at the end of the lSI and 2nd restperiods only 27.10 % and 33.57 % of the larvae completed their metamorphosisand reached the adult stag~..It was found that the death of PBW during diapause was due to eithernormal or due to bacterial and/or viral infection as well as to the effect of theparasitoids Pyemotes heFfS; and P. robarlltor.1.2- Spring emergence of P. gossypiella in both years of 1995 and 1996 :Emergence of PBW adults took place from March until May and thepeak of emergence occurred during April.1.3- Forecasting of timing of PBW spring emergence on the basis of degreedays(dd’s) or aeeumutated heat units (A.H.U.) during 1994-95 and1995-96 seasons :Adult emergence started in 9th and Slh of March and nearly completed,However, in 14th and 261h of May for lsI and 2nd season. respectively.However, present study indicated that PBW spring emergence was initializedwhen about average of 433.5 dd’s were accumulated. Also, It was found thatthe low rate of heat units accumulatiou worked as a mortality factor on thepink bollwonn; so it was concluded that A.H. U. is an important factor fortiming and detennining size of pink bollwonn spring emergence (1.”generation).II. The biological effects of the blo-~nsecticide(Xenlari) against thespiny bollw’ormneonate lantae :Six concentrations ofXentari (1.25, 0.63, 0.31, 0.16, 0.08 and 0.04) gil.at rate of 2.5 rol/50 gm of diet were tested against neonate larvae of E.im.’ulana. The mortality percentages were 87.5, 80.0, 65.0, 37.5, 15.0 and12.5%. respectively after two days of feeding on contaminated diet.The LCSO and LC90 values of Xentari against Eo tnsuiana neonatelarvae were 0.29 gil and 1.30 gil, respectively with upper and lowerconfidence limits of (0.29 & 0.18 gil) and (1.96 & 0.88 gil).Xentari displayed latent effects during the subsequent stages. The~ ..obtained effects were :1) death ”),the different larval instars due to feeding theE. im”ulana neonate larvae for 2 days on contaminated artificial diet containedthe LC50 of Xentari; the percentage of surviving subsequent larvae was31.’JO/~ 2) increase in larval and pupal durations and 3) decrease the Iongivityof the adult and the number of deposited eggs/female comparing with theuntreated check.III. IIIstopathol.,glcal enet:ts of Xentarl 011 the spiny boIlWOnn larvae:Feeding the 4th instar larvae of E. insy/ana on Xentari - eon8l1;l;Ii.n-:adteddiet, using the highest coneentration( 1.25 g / I ) at the nit of Sml / 100g liK, f{)l”24 hrs caused many pathological eff~ in the mid-gut of the treated larvae.These effects, as shown in cross sections of the mid-gut, were separation ofthe ’epithelial cells from the basement membrane as well as elongation,vaeulization and breakdown of the larval epithelimn mid-gut. Also, Xentaricaused disorganization and disintegration of pretrophic membrane.IV-Evaluation of certain control pntgrams against cotton hollWOnns:Three control programs were evaluated against the cotton bollwonns(P. gossypiella, E. insulana and their complex) during 1994 cotton season.Another three control programs were rested during 1995 cotton season. During1996 cotton season, the previous six control programs were reevaluated.The tested control programs during 1994 season were program ”A”. (asequence of 4 sprays with the bio- insecticide Dipel.2X at the. nile of 400gmlfed; program ”B” a sequence of 3 sprays with the mixture of Dipel. 2X at400 glfed. with chemical insecticides at the half recommended rate and in therecommended sequence; and program ”C”, recommended. sequence and rate ofchemical insecticides, Dursban EC 450/0, Cutabron EC 500.4 and Bundock EC0.15•During 1995 cotton season. the tested control programs were : program”D”, sequence sprays with the bio-insecticide Xentari at 500 g/fed; program”E”, a sequence of sprays with the mixtures ofXentari (500 glfed.) + chemicalinsecticide at half of the recommended rates; and program ”F” (a sequence ofsprays with chemical insecticides (Cyanophos EC 500/~Cutabron EC 500.4 andBundock EC 150/0) at the recommended rates and sequence).144During 1996 cotton season. the efficacy ofll.c progran.s1. 13.C D. Eand F was evaluated against the bollw()TIIISPBW & SBW and their complexBWS.The cotton plants received the lsI spray in July 241h. August 2nd and71h during 1994. 1995 and 1996 seasons. respectively. Spraying of eachprogram was perfonned when the correlation betWeensmall larvae (lsi instar)and all counted larvae in infested bolls was significant,The conclusions of this set of experiments were :1- ProgflUU”Co (DutSban. Cutabron and Bulldock) was the most effectiveprogram against PBW. SBW and their complex BWS.2- The tested control programs were more effective against PBW than SBWespecially program ttott (Xentari alone).3- The efficiency of prognun ”D” (Xentari alone) against PBW larvae washigher than that of program ”F” (Cyanophos, Cutabron and Bulldock).while prognun ”F” was most effective against SBW and BWS.4- ProgflUU”13” (mixture of Dipel-2X + chemical insecticides) revealedhigher potential protective efficacy against bollworms than the two bininsecticides,Dipel-2X and Xentari when used alone.