squash silverleaf disorder ( Perring et al., 1993 ). Sweetpotato whitefly biotype B is also associated with the appearance of a new crop plant disorder in tomato termed irregular ripening ( McAuslane, 2007 ; Schuster et al., 1990 ). Symptoms of this
Cindy L. McKenzie and Joseph P. Albano
David J. Schuster
The silverleaf whitefly (Bemisia argentifolii Bellows & Perring) is an important pest of tomatoes in Florida and elsewhere. Associated with populations of the whitefly is an irregular ripening disorder of fruit characterized by inhibited or incomplete ripening of longitudinal sections of fruit and by an increase in the amount of interior white tissue. Experiments were conducted during the spring and fall tomato production seasons of 1995 and 1996 to elucidate the relationship of nymphal and pupal density with severity of the disorder. Insecticides or insecticide combinations were applied at predetermined densities of whitefly nymphs and pupae and the subsequent severity of the disorder was rated separately for external and internal symptoms on red ripe fruit harvested weekly. Expression of irregular ripening symptoms, especially external symptoms, were correlated positively to the density of whitefly nymphs and pupae (number·10-1 terminal leaflets on the seventh to eighth leaf from the top of a main or lateral stem) increased. Expression of external symptoms tended to be better correlated with whitefly density when symptom severity was rated 1 and 3 weeks after estimating whitefly density for the spring and fall seasons, respectively. Expression of internal symptoms tended to be more consistently correlated with whitefly density when symptom severity was rated 2 and 3 weeks after estimating whitefly density for the spring and fall seasons, respectively.
Charles A. Powell and Peter J. Stoffella
Mature-green and mature-red tomato (Lycopersicon esculentum Mill.) fruit were harvested from spring- and fall-grown plants infested with sweet potato whitefly (SPWF; Bemisia tabaci Gennadins). The mature-green fruit were either ripened at 20 to 22C or cold-stored at 10 to 13C for 3 weeks and then were allowed to ripen at 20 to 22C. There was no significant difference in the appearance of either external or internal tomato irregular ripening (TIR) symptoms between the two storage–ripening regimes or in the appearance of internal TIR symptoms among the two storage regimes and vine-ripened tomatoes. Thus, removing the tomatoes from the SPWF during ripening does not reduce TIR symptoms. About half of the mature-green tomatoes, ripened with or without cold storage (10 to 13C), developed no external TIR symptoms, but about half of these tomatoes had internal TIR symptoms. About one-third of the tomatoes developed external symptoms during ripening, but these symptoms disappeared after ripening was complete. A high percentage (71%) of these tomatoes with external symptoms also had internal symptoms. The remaining tomatoes developed external TIR that did not disappear, and almost all of these tomatoes had internal symptoms. These data suggest that culling tomatoes that develop external TIR during ripening will reduce but not eliminate tomatoes with internal TIR from the fresh-fruit market.
Shahab Hanif-Khan, Robert C. Bullock, Peter J. Stoffella, Charles A. Powell, Jeffrey K. Brecht, Heather J. McAuslane, and Raymond K. Yokomi
Silverleaf whitefly (SLW) (Bemisia argentifolii Bellows and Perring) feeding was associated with development of tomato irregular ripening (TIR) symptoms. `Micro-Tom', `Florida Basket', `Florida Lanai', and `Florida Petite' dwarf cherry tomatoes (Lycopersicon esculentum Mill.) were infested with adult SLW to observe oviposition preference, plant tolerance, and TIR symptom development in two experiments. There was no oviposition preference among the cultivars in either of the trials. TIR fruit symptoms were expressed as longitudinal red streaks with yellow, green, pink, or red blotches externally and white tissue internally. External TIR symptoms at the pink stage of ripening ranged from 32% (`Micro-Tom') to 82% (`Florida Basket') in Expt. 1 and 44% (`Micro-Tom') to 93% (`Florida Petite') in Expt. 2. In Expt. 1, external TIR symptoms disappeared from 18% (`Florida Lanai') to 37% (`Micro-Tom') and, in Expt. 2, 16% (`Micro-Tom') to 39% (`Florida Basket') of the fruit during ripening. SLW-infested plants exhibited 82% (`Florida Lanai') to 99% (`Florida Basket') and 76% (`Micro-Tom') to 90% (`Florida Petite') of fruit with internal white tissue regardless of external symptoms in Expts. 1 and 2, respectively. Tomatoes with severe TIR symptoms rarely ripened to full red. Postharvest characteristics of ripening SLW-infested and control fruit were evaluated (Expts. 3 and 4). Generally, the SLW-infested fruit were lighter in color than the control fruit. The control fruit developed normal red color while the SLW-infested fruit developed a blotchy, streaky color that was overall more of an orange-red. SLW-infested fruit were firmer than the control fruit in both experiments. Ethylene production was higher in SLW-infested fruit. While the total soluble solids contents were not significantly different between the treatments, the SLW-infested fruit were more acidic than the control fruit. Each cultivar was susceptible to oviposition by SLW and induction of TIR symptoms. However, TIR symptom expression differed among the cultivars. Despite higher ethylene levels, the ripening process in the SLW-infested fruit appeared slower or may have been inhibited by factors induced by the SLW compared with the control fruit, which ripened normally.
A. A. Csizinszky and D. J. Schuster
Two insecticidal spray frequencies, 0 and 3x per week, against the sweetpotato whitefly, Bemisia tabaci Gennadius, were evaluated at three K rates, 190, 380 and 760 kg.ha-1, for their effect on whitefly population, fruit yield and incidence of irregular ripening on tomato, Lycopersicon esculentum Mill., cv. Sunny. Whitefly populations were reduced with three weekly sprays, but not by K rates. Early yields were best with three weekly sprays and with the highest K rate. For the season, yield of extra large (≥ 70 mm diameter) fruit was reduced with three weekly sprays and with increasing K rates. Proportions of irregularly ripened fruits were similar with either spray frequency, but were reduced at the highest K rate.
S. Hanif-Khan, R.C. Bullock, P.J. Stoffella, J.K. Brecht, C.A. Powell, and H.J. McAuslane
Silverleaf whitefly (SLW) (Bemisia argentifolii Bellows and Perring) feeding has been associated with development of tomato irregular ripening (TIR) symptoms. Four dwarf cultivars of cherry tomato (Lycopersicon esculentum L.) were infested with adult SLW to observe oviposition preference, tolerance and TIR symptom development. Oviposition preference was observed at low SLW population. Florida Petite was the most preferred and Micro-Tom the least preferred cultivar, with Florida Lanai and Florida Basket intermediate. Each cultivar exhibited TIR symptoms associated with feeding by the SLW. TIR fruit symptoms were expressed as longitudinal red streaks with yellow, green, pink or red blotches externally, and white, yellow or green tissue internally. External TIR symptoms ranged from 32% (Micro-Tom) to 82% (Florida Basket). However, external symptoms disappeared from 34% (Florida Lanai) to 56% (Micro-Tom) of the fruits during ripening. SLW infested plants had 82% (Florida Lanai) to 99% (Florida Basket) of fruits with internal white tissue regardless of external symptoms. Tomatoes with TIR symptoms rarely ripened to a mature red, and sometimes had empty locules, were smaller in size and were seedless.
S. Hanif-Khan, P.J. Stoffella, J.K. Brecht, H.J. McAuslane, R.C. Bullock, C.A. Powell, and R. Yokomi
External and internal tomato irregular ripening (TIR) symptoms have been associated with the feeding of silverleaf whitefly (SLW), Bemisia argentifolii Bellows and Perring. Soil drench application of gibberellic acid (GA3) (100 ppm, Trial 1 and 2) and cycocel (CCC) (2000 ppm, Trial 1; 1000 ppm, Trial 2) were applied to dwarf cherry tomato (Lycopersicon esculentum) in the presence and absence of SLW to mimic the TIR disorder induced by the SLW. Application of GA3 induced external and internal TIR symptoms similar to the SLW-induced disorder in `Florida Petite'. There were essentially no TIR symptoms in fruit treated with CCC, an inhibitor of GA biosynthesis. In Trial 1, internal white tissue in GA3, SLW, and CCC treatments was expressed in 97%, 95%, and 4% of the total fruit, respectively. Incidence of external TIR symptom was highest (56%) in the GA3 plus SLW treatment. In Trial 2, GA3 application in the presence (83%) or absence (85%) of SLW resulted in the highest incidence of fruit with internal white tissue. External TIR symptoms induced by GA3 in the presence and absence of SLW were reduced with CCC application. These results suggest that the TIR disorder in tomato is induced by the SLW may be a GA3-regulated disorder.
Charles A. Powell and Peter J. Stoffella
D.J. Schuster, T.F. Mueller, J.B. Kring, and J.F. Price
A new disorder of fruit has been observed on tomato (Lycopersicon esculentum Mill.) in Florida. The disorder, termed irregular ripening, was associated with field populations of the sweetpotato whitefly, Bemisia tabaci (Gennadius) and is characterized by incomplete ripening of longitudinal sections of fruit. An increase in internal white tissue also was associated with whitefly populations. In field cage studies, fruit on tomato plants not infested with the sweetpotato whitefly exhibited slight or no irregular ripening, whereas fruit from infested plants did. Fruit from plants on which a whitefly infestation had been controlled before the appearance of external symptoms exhibited reduced symptoms compared to fruit from plants on which an infestation was uncontrolled.
J.K. Brecht, S.J. Locascio, and K.A. Bergsma
Tomatoes (var. Sunny) were grown using drip irrigation and polyethylene mulch in a three-year study with water applied to plots at 0, 0.25, 0.50, 0.75 and 1.00 times pan evaporation in one application per day. Breaker stage fruit were harvested twice each season at 7 to 10 day intervals and evaluated after storage for 11 days at 20C. Response to water application varied with seasonal rainfall levels. Soluble solids levels decreased with increasing water quantity only in the first (relatively dry) season, while titratable acidity levels decreased with increasing water in all three seasons. Fruit color was not affected by water quantity in the first season but hue angle increased and chroma decreased with increasing water in the second and third seasons. Decay incidence (associated primarily with blossom end rot) was higher in nonirrigated than irrigated treatments and in the second harvests. Internal white tissue, a symptom of irregular ripening, was more common in irrigated treatments and in the wetter second and third seasons