Overwintering Survival, Phenology, Voltinism, and Reproduction Among Different Populations of the Leaf Beetle <I>Diorhabda elongata</I> (Coleoptera: Chrysomelidae)

Abstract

The classical biological control program for exotic saltcedars (various Tamarix species and hybrids) has involved the assessment of different populations of the leaf beetle Diorhabda elongata (Brullé) s.l. that are promising for release in areas of North America that are located south of 37 degrees N latitude. We report here the overwintering survival, phenology, and voltinism of four D. elongata populations (Tunisia, Crete, Uzbekistan, and Turpan) in eastcentral Texas. In addition, we studied their developmental and reproductive biology, which also included the previously released population from Fukang, China. Overwintering survival of the adult beetles of the Crete and Tunisia populations was 90-99 and 75%, respectively. The Uzbekistan and Turpan beetles had <31% overwintering survival. All D. elongata populations began ovipositing in late March. The Turpan beetle may produce three summer generations and ceased oviposition by September. The Crete beetle produced four summer generations plus a partial fifth generation and ceased ovipositing by mid-October. Both the Tunisia and Uzbekistan beetles produced five summer generations plus an unsuccessful partial sixth generation; oviposition extended into late November. Larval development and survival were generally similar among D. elongata populations. The Turpan and Fukang beetles had a shorter preoviposition period and produced more but smaller egg masses than the other beetle populations. However, this did not alter a female's lifetime fecundity and generally did not affect the innate capacity for increase compared with other populations. The Crete beetle seems to be the most promising for release in central Texas and points further south.

Open field host selection and behavior by tamarisk beetles (Diorhabda spp.) (Coleoptera: Chrysomelidae) in biological control of exotic saltcedars (Tamarix spp.) and risks to non-target athel (T. aphylla) and native Frankenia spp.

“…The northern tamarisk beetle Diorhabda carinulata (Desbrochers) (Coleoptera: Chrysomelidae) (Tracy and Robbins, 2009), collected from Fukang, China and Chilik, Kazakhstan, was released at 10 sites in 6 western U.S. states (NV, UT, CO, WY, TX, and CA) beginning in May 2001, and have defoliated over 50,000 ha of saltcedar in Nevada and Utah (Geraci, 2006;DeLoach et al, 2007, in press), but enter diapause too early in southern latitudes (below 38°N), and do not overwinter or establish (Lewis et al, 2003b;Bean et al, 2007). Three species, collected from Uzbkeistan (the larger tamarisk beetle, Diorhabda carinata (Faldermann)), Greece (Crete and Posidi) (the Mediterranean tamarisk beetle, Diorhabda elongata (Brullé)), and Tunisia (the subtropical tamarisk beetle, Diorhabda sublineata (Lucas)), are compatible with summer daylengths in Texas and other areas south of 38°N latitude (Milbrath et al, 2007;Tracy and Robbins, 2009). Mediterranean tamarisk beetles released in Texas in [2004][2005] have defoliated 6 ha of saltcedar along 9 km of riparian habitat and established satellite colonies over a 21-km area near Big Spring, in west-central TX (DeLoach et al, 2008, in press;Hudgeons et al, 2007a).…”

“…25 eggs (average 7-8) on the foliage singly or in tight clusters. In the laboratory at 28°C (Lewis et al, 2003b;Milbrath et al, 2007), development requires 5.7 days for the egg stage, 13 days for the larval stages (three instars), and 5 days for the pupal stage (larvae drop from the foliage into leaf litter for pupation), followed by a 6-day female preoviposition period and a 16-day oviposition period. The mean generation time is 39 days, and the average female produces 281 (D. elongata), 209 (D. sublineata), or 194 (D. carinulata) eggs.…”

“…Population doubling time is 6.2 days. In the field, the life cycle requires about 30-35 days during the summer, with four generations in Texas below the 38th parallel) (Milbrath et al, 2007;DeLoach et al, in press), as adults emerge from overwintering in late March-early May and exhibit overwintering/diapause behaviors beginning in mid-September to early November. Adults overwinter under litter on the soil surface or in clumps of grass.…”

Distribution of the subtropical tamarisk beetle,Diorhabda sublineata(Lucas, 1849) (Coleoptera: Chrysomelidae), in Mexico

“…The four species in general responded similarly, with heavy damage to saltcedars, much less to athel, and very little or none to Frankenia. On 28 unrelated agricultural or habitat associated plants, the larvae all died during the 1 st instar with no feeding (Milbrath et al, 2007) who also studied the biology and ecology of D. elongata at Temple.…”

“…Initiation of overwintering diapause (hibernation) is regulated by summer daylength , Milbrath et al 2007, Bean et al 2007a. The Fukang/Chilik beetles require the long summer daylength (more than 14 hr 45 min) of their native area in Asia (43° to 44° N latitude) to overwinter properly.…”