Matthew Hentz

A COMPARISON OF TRAPS AND STEM TAP SAMPLING FOR MONITORING ADULT ASIAN CITRUS PSYLLID (HEMIPTERA: PSYLLIDAE) IN CITRUS

Abstract Studies were conducted at 2 different field sites to compare yellow sticky card traps, blue sticky card traps, Multi-Lure traps, and CC traps (red, blue, black, white, yellow, and dark green bases) for monitoring adult Asian citrus psyllid, Diaphorina citri Kuwayama, in citrus. The Multi-Lure and CC traps were charged with either ethylene glycol or a dichlorvos kill strip to kill psyllids entering the trap. We also investigated a stem tapping method for monitoring adult D. citri. Yellow sticky card traps captured significantly more adults than blue sticky card traps over a 4-week period in one study but not the other. Over all sample weeks, each of these traps captured significantly greater numbers of adults than any of the other traps. Yellow and blue sticky traps were equally effective in detecting the presence of adults in trees given the infestation levels present at the 2 study sites. The CC and Multi-Lure traps captured so few adult psyllids and provided such poor detection of trees infested by adults that they appeared to have no value for monitoring D. citri. Tap sampling was easy to conduct and provided relatively good detection of trees infested by adults given the infestation levels present at the 2 groves. An advantage to stem tap sampling over sticky trap sampling is that tap sampling provides information on the presence and relative abundance of adult D. citri during a single visit to a block of trees while sticky trap sampling requires 2 visits. Research to develop standard protocols for sticky trap and stem tap sampling for adult D. citri in citrus would be advantageous.

Development, longevity, and fecundity of Sipha flava (Homoptera: Aphididae) feeding on Sorghum bicolor

Abstract Sipha flava is a serious pest in sugarcane in southern Florida, so efforts in better understanding its biology were initiated. Development, longevity, and fecundity of alate and apterous S. flava (Forbes) feeding on Sorghum bicolor [L.] Moench., cultivar ‘Kow Chow,’ were examined under near-ambient temperature and lighting conditions within a glasshouse. After examining several body dimensions during apterous aphid development (antennal length, head width, body length, and abdominal width), antennal length was found to be the best indicator of an instar. Apterous aphids completed development from nymph to adult in ≈8 d and passed through four instars. A comparison between the sizes of apterous and alate morphs indicated that apterous females were larger and weighed more than the alates. Both morphs survived equally as long during reproduction (21 d) but produced slightly different numbers of nymphs over their life (apterous = 54.3, alate = 48.2). During the first 8 d of reproduction, apterous adults produced 3.3 nymphs/d and alates produced 2.3 nymphs/d. However, during the following 8 d, nymphal production by apterous females dropped to 2.7 nymphs/d but increased to 2.9 nymphs/d by alates. The estimated intrinsic rate of natural increase (rm) for apterous aphids was 0.314. The net reproductive rates (Ro) for alate and apterous adults based on 0% nymphal mortality were 45.80 and 53.09 and for 21% nymphal mortality were 36.3 and 41.9, respectively.

MORPHOLOGY AND BIOLOGY OF DIOMUS TERMINATUS (COLEOPTERA: COCCINELLIDAE), A PREDATOR OF SIPHA FLAVA (HOMOPTERA: APHIDAE)

Sugarcane is an important crop in several counties around Lake Okeechobee in south Florida (Hall & Bennett 1994). It has been a commercial staple since the 1920s, and in the year 2000, 450,000 acres were planted (Dovell 1947, FASS 2000). There is a diverse pest complex associated with sugarcane which includes insects from a broad spectrum of Orders such as Lepidoptera, Homoptera, Coleoptera, Hemiptera, and Acarina (Hall 1988, Hall & Bennett 1994). One of the pest species that can cause severe plant damage is the yellow sugarcane aphid, Sipha flava (Forbes). This aphid has been a resident and important pest of sugarcane for many years (Ingram et al. 1938, Ingram et al. 1951, Hall & Bennett 1994). It feeds mostly on the underside of leaves. After several days of feeding the leaves can exhibit red discoloration followed by chlorosis and necrosis (Ingram 1951). Prolonged feeding can result in plant stunting and death (Nuessly and Hentz, pers. obs.). Effective insecticides are available, and recently these have been used during the spring to reduce damage to the young plants. As a result, midto lateseason aphid populations can rebound to damaging levels. Therefore, sugarcane growers also rely on abiotic and biotic control measures such as weather, disease, and natural enemies to reduce yellow sugarcane aphid populations. One natural enemy with potential to control yellow sugarcane aphid is the small coccinellid, Diomus terminatus (Say) (Hall & Bennett 1994). Previously named Scymnus terminatus Say, it is a generalist aphid predator belonging to the tribe Scymnini (Thompson 1928, Gordon 1976). Its range is large and encompasses most of the eastern and southeastern United States (Gordon 1976). Gordon (1976) has provided a good description of the adult, but little descriptive information is available on its other life stages (Chittenden 1906, Watson 1926). Hall (2001) provided some information on the biology of D. terminatus . The purpose of this study was to present a general description of some of the life stages and basic biology of D. terminatus . Adults of D. terminatus were collected from sugarcane fields in Pahokee, Florida. Five groups of 10 beetles of mixed sexes were placed in separate petri dishes (150 × 15 mm) and held at 27.5 ° C ± 1 ° C, 16:8 L:D photoperiod. Yellow sugarcane aphid—infested Sorghum—Sudan hybrid (Var. ‘Kow Chow’) leaves were placed in the petri dishes daily. The aphids served as a food source. A moist filter paper was placed in the bottom of each petri dish to maintain a humid environment. Female beetles began to oviposit after several days. Eggs of a similar age were collected and held until larvae emerged. Fifty neonate larvae were separated and housed in individual petri plates and observed once per day until their death. Observations on the development and morphology were recorded and summarized. Four measurements for each larva were recorded: head length (anterior most to visible posterior end), head width (distance between simple eyes), body width (width of third thoracic segment), and body length. Figure 1 is provided to aid in the recognition of some of the life stages.

Field Survey of Asian Citrus Psyllid (Hemiptera: Liviidae) Infestations Associated with Six Cultivars of Poncirus trifoliata (Rutaceae)

Summary The Asian citrus psyllid (Hemiptera: Liviidae) transmits a bacterium responsible for huanglongbing, a serious citrus disease. Insecticidal control of the psyllid is a key tactic used to manage the disease, but host plant resistance may hold some promise and clues in the search for alternative tactics. Results of a field survey revealed that relatively large infestation densities of the psyllid developed on conventional Citrus (Rutaceae) and citrange (Rutaceae) cultivars but not on any of 6 Poncirus trifoliata (L.) Raf. (Rutaceae) cultivars. Poncirus trifoliata is a species closely related to Citrus, and citranges are hybrids of sweet orange and P. trifoliata. Reduced colonization by the psyllid on P. trifoliata was largely a result of reduced rates of oviposition. Poncirus trifoliata resistance to oviposition was not observed in 4 citrange cultivars.