Chemical control of the citrus nematode, Tylenchulus semipenetrans Cobb, has consistently increased yield of grapefruit on sour orange rootstock in Texas. In this study, data from chemical control tests conducted from 1973 to 1980 were analyzed to determine the relationship between nematode counts and grapefruit yield and fruit size. The correlation between yield and nematode counts was negativ...

Soil application of DBCP (l,2-dibromo-3-chloropropane) and foliar applications of oxamyl (methyl N',N'-dimethyl-N-[(methylcarbamoyl)oxy]-l-thiooxamimidate) were compared for control of Tylenchulus semipenetrans in a grapefruit (Citrus paradisi) orchard, DBCP reduced nematode populations and increased fruit growth rate, fruit size at harvest, and yield compared to the untreated controls in the 2...

Distribution of the citrus nematode (Tylenchulus semipenetrans) was studied over 18 months in a 6-year-old orchard of grapefruit (Citrus paradisi cv. Ruby Red) on sour orange (C. aurantium) rootstock. The 1.8-ha orchard was under chemical weed control, no tillage, and flood irrigation. Highest numbers of nematodes were found in the top 15 cm of the soil profile. The nematode population peaked i...

In a survey of antagonists of nematodes in 27 citrus groves, each with a history of Tylenchulus semipenetrans infestation, and 17 noncitrus habitats in Florida, approximately 24 species of microbial antagonists capable of attacking vermiform stages of Radopholus citrophilus were recovered. Eleven of these microbes and a species of Pasteuria also were observed attacking vermiform stages of T. se...

Pasteuria penetrans Sayre & Starr parasitizes several nematode species and is considered a promising biocontrol agent of the root-knot nematode, Meloidogyne spp. (1,7). Numerous plant-parasitic nematodes, including Tylenchulus semipenetrans, however, are seldom if ever infected by this biocontrol agent (3). Tylenchulus semipenetrans Cobb is the most economically important and widespread nematod...

The infectivity of five populations of Tylenchulus semipenetrans were compared and differentiated on 10 hosts (5 Citrus spp., 1 Poncirus trifoliata, and 4 hybrids of Citrus spp. X P. trifoliata). Differences in levels of infection and development (P = 0.01) occurred between Citrus spp. and P. trifoliata cv. 'Pomeroy' and their three hybrids, C. paradisi X P. trifoliata cv. 'Swingle' citruntelo ...

In lraq, treatment of producing citrus trees with a 75% emulsifiable formulation of 1,2-dibromo-3-chloropropane (DBCP), applied in irrigation water at rates of 66-88 kg (a.i.)/hectare, gave excellent control of the citrus nematode (Tylenchulus semipenetrans) greatly improved tree vigor, and increased the fruit yield for at least 3 years after treatment. Applications made during the spring gave ...

The presence of two biotypes of the citrus nematode (Tylenchulus semipenetrans) in Italian citrus and olive orchards has been confirmed by comparing host specificity. Host reaction to California biotypes C1 and C3 and to three populations from Arizona, Texas, and Florida indicates that of these five United States biotypes, all except C3 consistently fit biotype C1. These findings, and the resul...

Karyotype, host preference, isozyzme patterns, morphometrics, and mating behavior of two burrowing nematode populations from Hawaii, one infecting Anthurium sp. and the second infecting Musa sp., were compared with Radopholus similis and R. citrophilus populations from Florida. The population from Anthurium sp. had five chromosomes (n = 5), and that from Musa sp. had four (n = 4). Neither of th...