Curculio Caryae Research Articles

Development and Validation of Prediction Equations for Estimation and Control of Pecan Weevil 1 Populations 2

Data collected in 1972, 1973, and 1974 were used to develop equations for estimating pecan weevil, Curculio caryae (Horn), populations from trap catch at 2-day intervals. Two of these equations were modified by adding a survival factor, validated under field conditions for estimating the number of pecan weevils in a tree, and for timing insecticide applications. Timing of insecticide applications based upon a threshold of 40 weevils/tree as estimated by the prediction equation resulted in 2.4, 0.6, and 0.4% of the nuts with grubs in 1974, 1975, and 1976, respectively. The high number (>350 collected in traps under a tree with a history of a high infestation) of weevils emerging under pecan trees in 1974 and low numbers (<40 collected in traps under the same tree) in 1976 was a further check on the accuracy of the evaluation of weevil damage (nuts with grubs) and control in 1974. The pecan weevil has predominately a 2-yr life cycle and grubs entering the soil in 1974 emerged as adults in 1976. Also, a method is provided which allows practicing entomologists or pecan growers to readily predict number of pecan weevils in a tree from trap catch.

Pecan Weevil Adult Emergence, Onset of Oviposition and Larval Emergence from the Nut as Affected by the Phenology of the Pecan12

Emergence of adult Curculio caryae (Horn) from the soil apparently is unaffected by pecan variety. Hardness of the pecan shell and the gelatinous condition of the ovule appear to have an effect on initiation of oviposition. Larval emergence from infested pecans also varied consistent with the onset of oviposition and the phenology of the pecan. These findings indicate that a pecan weevil pest management program can be developed to concentrate on preventing oviposition as a management strategy.

Antennal sensilla of the pecan weevil, Curculio caryae (Horn) (Coleoptera:Curculionidae)

Scanning electron microscopy revealed 2 types of sensilla trichodea, 4 types of sensilla basiconica, and one type of sensilla styloconica on the antennal club of the pecan weevil, Curculio caryae. All receptor types are found on both male and female weevils and their distribution is similar. The total number of sensilla on the antennal club of the male is estimated to be 1467 and on the female 1491. Significant differences in numbers of basiconica type I exist for dorsal and ventral surfaces on the male but not on the female. A significant difference in number exists between the sexes for trichodea type I and for dorsal/ventral surfaces on the female. Significant differences exist in length between the sexes for trichodea type I on segments 2 and 3 and trichodea type II on all 3 segments. The porous surface present on basiconica type I sensilla indicates a possible olfactory function.

PECAN WEEVIL, CURCULIO CARYAE (COLEOPTERA: CURCULIONIDAE): 1. COMPARISON OF ADULT SAMPLING TECHNIQUES

AbstractIn 1972, limb jarring, tanglefoot trunk barrier, emergence trap, and insecticide spray knockdown methods of sampling for adult pecan weevil, Curculio caryae (Horn), were compared. The latter two methods were most efficient in detecting onset of adult emergence, seasonal fluctuations in emergence, and population differences among sample dates and among trees. In 1973, further comparisons of the latter two methods gave results similar to 1972 results. The required sample size was influenced by population density. The number of pecan trees to be sampled for a 20% standard deviation of the mean was small enough to be practical for grower use for most sample dates in 1973 and at dates near peak emergence in 1972.

Study of the Pathogens of the Pecan Weevil Larvae

Larvae of the pecan weevil, Curculio caryae (Horn), were surveyed monthly for naturally occurring pathogens in Mississippi and Arkansas from April 1972 to May 1973. Weevil larvae pathogens found in this survey were Metarrhizium anisopliae (Metch.), Beauveria bassiana (Bals.), Pseudomonas aeruginosa (Schroeter) Migula, and Serratia marcescens Bizio.

Hydrocarbons from males, females, and larvae of pecan weevil:Curculio caryae (Horn)

As part of a program to identify as many as possible of the components of the pecan weevil, Curculio caryae (Horn), the hydrocarbons from males, females, and larvae were isolated by solvent extraction and column chromatography and subjected to gas lipuid chromatography-mass spectrometry analysis. n-Alkanes from C14-C32 in the larvae and unsaturated and branched chain hydrocarbons from C20-C32 in males and females were found. There are no significant differences between the hydrocarbons of the male and female pecan weevils.

A Modified Cone Emergence Trap with Increased Capabilities for Pecan Weevils

A cone emergence trap for the pecan weevil, Curculio caryae (Horn), was constructed of hardware cloth with a Leggett trap top attached to the apex of the cone. This modification enabled the trap to sample pecan weevils emerging beneath it as well as those which crawl up the outside of the cone. With use of pheromones, the trap's efficiency could be further increased. The trap was as efficient as the presently used cone traps and collected over 9 times as many weevils during peak emergence than did cone emergence traps without the Leggett top modification. This modified trap also detected weevil emergence later in the season.

A Bibliography of the Pecan Weevil, Curculio caryae (Coleoptera: Curculionidae)

The pecan weevil, Curculio caryae (Horn), a native American species and an important and often persistent pest of pecans, is considered a major insect pest in many pecan-growing States. Moreover, as annual production of pecans increases, weevil populations increase, and as management practices become more intensive, control becomes more difficult and more complex.

Lipid composition of the pecan weevil,Curculio caryae (Horn).

The lipids of larvae, male adults, and female adults of the pecan weevil,Curculio caryae (Horn), were studied, and special attention was given the fatty acid composition. The larvae contained an unusually high amount of lipid material (40.6%), most of it concentrated in the neutral lipid fraction. Male and famale adults contained more conventional quantities, 5.8 and 8.2%, respectively. Oleic acid was the major fatty acid in the total and neutral lipids of all stages; linoleic acid was the most abundant in the phospholipid fractions.

Pecan Weevil: Suppression of Larvae with the Fungi Metarrhizium anisopliae and Beauveria bassiana and the Nematode Neoaplectana dutkyi13

Metarrhizium anisopliae (Metschnikoff) Sorokin, Beauveria bassiana (Balsamo) Vuillemin, and Neoaplectana dulkyi Jackson, were evaluated in the laboratory and in the field as pathogens of larvae of the pecan weevil, Curculio caryae (Horn). Selected treatments with these pathogens significantly increased mortality of larvae in field experiments within 20 days after soil treatment. Effectiveness of pathogens varied with isolate, culture technique, and method of application.

Population Density of the Pecan Weevi1 Under ‘Stuart’ Pecan Trees12

Two methods were used to estimate the population of adult Curculio caryae (Horn) emerging under ‘Stuart’ pecan trees. Weevils were trapped and collected by enclosing the area under the tree within the drip-line with a tent of cotton or nylon cloth. By this method the population per tree in 1969 was estimated at 3785 weevils. The second method used 100 screen wire traps arranged in 5 concentric circles 5.0 ft apart except for the innermost circle of 7.5 ft from the tree trunk. By this method tree populations were estimated at 1762 weevils in 1968 and 6130 in 1969. In addition to population-per-tree estimates, the trap method depicted the distribution of the population at 100 different points under the tree, thus reflecting the effects of positional factors. More adults emerged in the north and east quadrants than in the south and west, and emergence from the soil close to the trunk was above average.

Structure of the Reproductive System of the Pecan Weevil (Curculionidae)1

The pecan weevil, Curculio caryae (Horn), is noted for its extremely long and slender beak which it uses for drilling the coverings of the host fruit for feeding and in preparation for egg-laying. There is a parallel development in the reproductive organs and the extended ovipositor has been found to be as long as the female beak, about 11 mm. The object of this paper is to describe in detail the reproductive system, male and female, using what seems to be the most appropriate and best established nomenclature. It is believed the male organs offer characters of taxonomic value but no other species of the genus has been carefully studied.

Experiments on Controlling Larvae of the Pecan Weevil By Cultural Methods

Experiments covering one season show that larvae of the pecan weevil ( Curculio caryae Hom) can be prevented from burrowing into the soil under pecan trees by hand raking and rolling and to a lesser degree by raking alone when such operations are performed just previous to the time of emergence of the larvae from the nuts.