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The highly oligophagous tephritid Chaetostomella cylindrica infests the flower heads of six genera and ten species of thistles in Lebanon. It predominantly utilizes two hosts occurring in sympatry, Notobasis syriaca and Onopordum illyricum. Previous work showed that adult flies emerging from N. syriaca fit more closely the description of the species, particularly with respect to the colour and pattern on the mesonotum; furthermore, significant differences were observed between the aculeus shape and length. This study investigates the biology of the immatures and compares adults from the two host races behaviourally and genetically. Larvae of both races fed in a similar way, with each larva destroying 3-10 achenes; however, the oviposition behaviour of females differed. Females of the Onopordumassociated flies laid an average of three eggs per head, and deposited the eggs glued to each others in a cluster, while females of the Notobasis-associated flies deposited their eggs unattached, usually with one egg per head. Subtle differences were also observed in the post-mating behaviour of adult males. DNA sequencing of an amplified fragment of the mitochondrial NADH-dehydrogenase subunit 1 gene revealed 44 single nucleotide polymorphisms in 622 base pairs. A PCR-RFLP method was developed to distinguish the two host-associated populations. Together with previously published morphometric studies, our data show that C. cylindrica consists of distinct host races, which seem to be reproductively isolated as two separate genetic lineages were observed. [ABSTRACT FROM AUTHOR]

The in flu ence of sev eral types of plas tic mulches in en hancing earliness, maximizing production, and reducing insect infestation of strawberries grown in a tun nel green house in a mild Med i ter ra nean cli mate was eval u ated in two grow ing sea sons. In 1996-1997, yield of 'Oso Grande' dur ing the first three weeks of har vest was the high est on the black on white mulch (B/W), fol lowed by black (B) white (W), and clear (C). Total yield was comparable among all mulches. Mite in fes ta tion (mites being the main pest of straw ber ries in the re gion), and the heavi est weed growth occurred un der C, re sulting in weaker plants. In 1998-1999, yield of 'Camarosa' was con sis tently higher on re flec tive mulch (R) in comparison to C, B, and green (G). We ob served a high de gree of re sis tance to mite infestation in 'Camarosa', where mites ap peared only dur ing the last week of harvest. The R mulch had the low est count of mites, thrips, aphids and whiteflies at all sam pling dates. The high est counts of those pests were on C mulch. We rec om mend the R mulch, for its en hance ment of yield, reduced in sect and mite in fes ta tion, and weed con trol prop er ties in a mild winter-spring grow ing climate. [ABSTRACT FROM PUBLISHER]

Tomatoes grown under greenhouse conditions were sprayed with radiolabelled maneb and zineb to determine the extent of degradation of these fungicides to ethylenethiourea (ETU) and to study the persistence of ETU on the fruits. The total ([sup 14]C) residues decreased from 0.082 mg/kg and 0.11 mg/kg at day 0 to 0.023 mg/ kg and 0.05 mg/kg at day 20, on zineb- and maneb-treated fruits, respectively. This reduction was mainly due to the rapid growth of the fruits. ETU residues on tomato fruits were found to decline with time. A sharp reduction in ETU content was observed during the first 24h after treatment, followed by a slow decline in the following 5 days. ETU content was reduced by about 80% by day 20 after the fungicide application, and the concentration of EU, the major degradation product of ETU, doubled during the same period. Studies with tomatoes fortified with ([sup 14]C) ETU (0.006 mg/kg) prior to processing into tomato paste showed that 70% of the radioactivity was lost during washing of the tomatoes in water. Further losses of ETU occurred during boiling of the juice (6%) and during storage of the tomato paste for a period of 3 weeks (3%). [ABSTRACT FROM AUTHOR]