|Spotted Alfalfa Aphid Resistance
Therioaphis maeulata (Buckton) PDF Version
R. C. Berberet, J. L. Caddel, and A. A. Zarrabi
Container ....Flat (6 x 31 x 55 cm or similar size)
Medium .......Soil mix (eg. 8 parts sand; 3 peat; 3 perlite; 1.4% by lime)
Temp/Light ...26+ 4°C and 18 hour daylength
No. of plants .... 50 to 70 per replicate in rows 3 cm apart
No. of reps ..3 minimum
Other ........Scarify seed and treat with fungicide to
Source .......Colony consisting of blend of several field collections from area of adaptation, replenished annually
Rearing ......Susceptible plants in greenhouse (eg. Arc, Caliverde)
Temp/Light ...26 + 4°C and 18 hour day length
Age of plant ..... 7 to 8 days after emergence; unifoliolate stage; count plants at time of infestation
Method ..........Sprinkle aphids onto plants
Rate ............Minimum of 2 aphids per plant
Length ..........Approx. 18 days or when over 85% of susceptible check plants are dead and resistant check is within the expected range; spray with malathion or diazinon to terminate infestation; rate plants 10 to 15 days after spraying
1-2 Resistant ....Plant has formed at least one trifoliolate (includes plants with both high and moderate levels of resistance)
3 Susceptible ....Plant has developed very little during infestation
4 Susceptible ....Plant living but has formed no trifoliolates
5 Susceptible.....Dead (= total emerged - classes 1 to 4)
Values for resistant standards are totals of l's and 2's. Percentage of plants surviving may be higher but may include many plants with little or no resistance.
DISTRIBUTION AND SEVERITY OF SPOTTED ALFALFA APHID
Spotted Alfalfa Aphid, Therioaphis maculata (Buckton)Click on the map above for a larger version. Se e also the KEY.
SCIENTIST WITH EXPERTISE
Name........R. C. Berberet
Address ....Department of Entomology
|CORRELATION TO FIELD
Field performance of alfalfa selected for resistance to spotted alfalfa aphid has conformed closely with expected results based on greenhouse evaluations.
Several biotypes of spotted alfalfa aphid are known to exist in the Southwest, and performance of resistant cultivars may vary depending upon the biotype(s) present. It would be advisable to test cultivars against aphid populations in areas where they will be grown.
The best procedure for collecting aphids from fields for colony establishment is tapping from infested stems. Fewer will be injured and chances of including natural enemies will be much reduced compared to sweeping. Field collected aphids should be held in isolation for 2-3 weeks to check for presence of parasites.
1. Jimenez, H.O., J.L. Caddel, and R.C. Berberet. 1988. Selection and characterization of tolerance to the spotted alfalfa aphid (Homoptera: Aphididae) in alfalfa. J. Econ. Entomol. 81:1768-1774.
2. Kindler, S.D., and R. Staples. 1970. The influence of fluctuating and constant temperatures, photoperiod, and soil moisture on the resistance of alfalfa to the spotted alfalfa aphid. J. Econ. Entomol. 63:1198-1201.
3. Nielson, M.W., and R.O. Kuehl. 1982. Screening efficacy of spotted alfalfa aphid biotypes and genetic systems for resistance in alfalfa. Environ. Entomol. 11 :989-996.
4. Nielson, M.W., and D.L. Olson. 1982. Horizontal resistance in 'Lahontan' alfalfa to biotypes of the spotted alfalfa aphid (Homoptera: Aphididae). Environ. Entomol. 11 :928-930.
5. Turner, J.W., D.L. Lloyd, and T.B. Hilder. 1981. Blue green aphid and spotted alfalfa aphid: a glasshouse study. Aust. J. Exp. Agric. Anim. Husb. 21:227-230.