Adrian G. B. Hunsberger

Citrus leafminer (Lepidoptera: Gracillariidae) in lime: Assessment of leaf damage and effects on photosynthesis

Abstract Studies were conducted to quantify leaf area damage to ‘Tahiti’ lime by citrus leafminer (CLM) (Phyllocnistis citrella Stainton) and to relate leaf damage to larval density and the length of time mining per leaf. Visual estimates of leaf damage were similar among five evaluators and were positively correlated with image analysis determinations. The number of CLM larvae per leaf and the number of days of mining were positively correlated with visual estimates of leaf damage and negatively correlated with net photosynthesis. Leaf damage by CLM was negatively correlated with net photosynthesis of potted trees and trees in an orchard. The data indicate that visual estimation is an accurate and rapid technique to assess leaf damage by CLM, and that leaf area damage and reductions in net photosynthesis due to CLM are related to the number of larvae per leaf as well as to mining duration.

Citrus Leafminer (Lepidoptera: Gracillariidae) Density: Effect on Yield of ‘Tahiti’ Lime

Abstract The relationship between damage by citrus leafminer , Phyllocnistis citrella Stainton, and ‘Tahiti’ lime yield were investigated in a 15-yr-old and a 5-yr-old lime orchard. Citrus leafminer population densities were controlled by insecticide applications of abamectin plus FC 435 oil, abamectin plus FC435 oil plus imidacloprid, and methomyl. The control was not treated. To ensure adequate citrus leafminer densities, adult citrus leafminer were periodically released in the experimental plots during fall and winter. For the 15-yr-old trees, the least amount of leaf area damage occurred in the abamectin plus FC 435 oil plus imidacloprid (1.9%) and the abamectin plus FC435 oil (2.3%) treatments compared with the control treatment (10–21%). In the 5-yr-old orchard, the least amount of leaf area damaged occurred in the abamectin plus FC 435 oil plus imidacloprid (0.4%) and the imidacloprid (0.1%) treatments compared with the control (20.85%). The percentage of leaf area damaged was linearly correlated with the average number of mines per leaf, average mine days, and cumulative mine days in both orchards. In both orchards, the percentage of leaf area damaged and cumulative mine days was linearly correlated with the number of fruit per tree and total fruit weight per tree. Calculating the economic injury levels indicated that 16–23% and 18–85% of leaf area damaged caused significant yield reductions in 15-yr-old and 5-yr-old trees, respectively.

OVIPOSITION AND LARVAL SURVIVAL OF DIAPREPES ABBREVIATUS (COLEOPTERA: CURCULIONIDAE) ON SELECT HOST PLANTS

Abstract In a preliminary survey in four commercial ornamental nurseries in south Florida (1998), Diaprepes abbreviatus (L.) (Coleoptera: Curculionidae) egg masses, feeding damage, or adults occurred on numerous field-grown ornamental plant species. Live oak (Quercus virginiana Mill.), silver buttonwood (Conocarpus erectus L. variety sericeus Fors. Ex DC), and black olive (Bucida buseras L.) had the highest percentage of plants with egg masses. Adult feeding damage was found on all examined plants of dahoon holly (Ilex cassine L.), cocoplum (Chrysobalanus icaco L.), black olive, live oak, Bauhinia sp., and Cassia sp. Oviposition of D. abbreviatus was evaluated in no-choice, two-choice, three-choice and multiple-choice caged tests. In no-choice tests, silver buttonwood had the highest mean number of egg masses. In two-choice tests, egg masses were laid on all plant species tested but there were significantly more egg masses on silver buttonwood than the alternate choice. The number of egg masses in the three-choice tests was low and there were no significant differences among the plant species tested. As in the no-choice and two-choice tests, significantly more egg masses were found on silver buttonwood in multiple-choice tests. Survival of larvae and their effect on plant growth was examined on several commonly grown plant species in southern Florida. Larval survival was highest on silver buttonwood and Sorghum sudanense Pers (sorghum-sudan) compared with other plant species. Root and/or total biomass was significantly reduced on green bean (Phaseolus vulgaris), silver buttonwood, Tahiti lime (Citrus aurantifolia), and sorghum-sudan.

Symptoms and Population Dynamics of Rhynchophorus Cruentatus (Coleoptera: Curculionidae) in Canary Island Date Palms

We documented the decline of a 2-hectare Canary Island date palm (Phoenix canariensis) nursery caused by the palmetto weevil (Rhynchophorus cruentatus) in Dade County, FL. External palm symptoms were defined, divided into nine categories, and representative palms were destructively harvested to assess internal weevil associations. Apparently healthy palms declined and died in a mean of 49 days. At the beginning of the study, 42% of 950 palms appeared healthy but within seven months only 3% were alive. Economic losses were estimated at

Egg Distribution and Sampling of Diaprepes abbreviatus (Coleoptera: Curculionidae) on Silver Buttonwood

285,000-

Effects of Temperature and Host Age on Suppression of Diaprepes abbreviatus (Coleoptera: Curculionidae) by Entomopathogenic Nematodes

380,000 for the nursery studied. Palm decline was patchily distributed in the field. The mean palm weevil counts ranged from 0.3 to 223.3 weevils per palm, for healthy to collapsing palms, respectively. Twenty-four weevil grubs were sufficient to kill one mature palm. External symptoms did not allow preventative diagnosis and treatment of internal R. cruentatus infestations. By the time that external symptoms were unambiguous, the mean total weevil counts per palm were over 100 with more than 65% as larvae and more than one quarter of these were >2.5 cm in length. Palms in these categories were dying because of irreparable damage to their apical meristems and attempts to save them would have been ineffectual. Thus, phytosanitation (palm removal and destruction) for management of R. cruentatus in Canary Island date palms should be implemented as soon as host leaves droop and weevil frass is observed. Growers and buyers of P. canariensis in regions where R. cruentatus exists should be aware of the potential lethal risk that it poses for this non-native palm. The costs of aggressive phytosanitation at the first symptoms of R. cruentatus infestation and prophylactic pesticide treatment at times of pruning, stress, or transplanting should be factored into the predicted cost of production and maintenance of Canary Island date palms in Florida.

Catolaccus hunteri (Hymenoptera: Pteromalidae), a Parasite of Anthonomus macromalus (Coleoptera:Curculionidae) in South Florida

Abstract Taylor’s power law and Iwao’s patchiness regression were used to analyze spatial distribution of eggs of the Diaprepes root weevil, Diaprepes abbreviatus (L.), on silver buttonwood trees, Conocarpus erectus, during 1997 and 1998. Taylor’s power law and Iwao’s patchiness regression provided similar descriptions of variance-mean relationship for egg distribution within trees. Sample size requirements were determined. Information presented in this paper should help to improve accuracy and efficiency in sampling of the weevil eggs in the future.