The Susceptibility of Certain Cotton Varieties to Empoasca spp. (Jassidae)‐Infestation Under Some Different Agricultural Practices in U.A.R.
Authors: Hosny M. M. , El.‐Dessouki S. A. 
Published: July 2010

The different tests of the susceptibility in several cotton varieties to jassid‐infestation lead to the following conclusions:

a. At Shoubra experimental area the means of jassid numbers on 4 varieties of Egyptian cotton were relatively low and insignificantly different from each others in the “unfertilized” treatment. The means increased gradually with the increase in the rate of fertilization (75, 150 and 225 kgms/feddan). The varieties in the latter cases showed varying susceptibilities and it could be arranged ascendingly according to the rates of infestation on them as follows: Bahteem 185 (least susceptible), Ashmouny, Giza 47 and finally Dandarah (most susceptible).

b. When 12 varieties of cotton were tested, at the Bahteem experimental area, for their susceptibility to jassids irrespective of any special treatment, a new pubescent strain of G. barbadense proved to be most resistant to jassids. On the other hand the cotton variety Triespecies No. I (H. recurrent) was the most susceptible. The remaining 10 varieties showed varying degrees of susceptibility and resistance between the above two extremes (Table 6).

c. Comparing the susceptibility in five Egyptian cotton varieties at Abouzabaal, with regard to 3 sowing dates, 3 sowing‐spaces and 3 rates of fertilization; the Giza 66 variety was found to be the most susceptible species among those tested throughout these treatments. The remaining four varieties hardly showed any difference within themselves in this respect.

d. In the general test of the relation between jassid‐infestation and sowing‐dates of cotton, 3 dates were applied at Abouzabaal during 1964, viz. 10th March, 25th March and 8th April. The middle date, however, was repeated in the Shoubra experiment while a later fourth sowing date, 3rd May, was followed in the Bahteem area (in the same year). By comparing the jassid‐infestation averages in those dates irrespective of locality it could be concluded that the jassid infestation was markedly reduced on the second date of sowing, on 25th March (at both Abouzabaal and Shoubra). The mean number of jassids was relatively higher on the plants sown on either 10th March or 8th April and was considerably higher still on the plants sown later, on 3rd May (at Bahteem).

e. In a brief test of the corelative dependence between the jassid‐infestation and both the length and density of the hairs on the cotton leaves, the following two remarks could be drawn:

1. There was a general tendency in the jassid infestation‐averages to decrease which the increase in hair‐density.

2. The hairiness could hardly be regarded as a primary to characteristic of resistance in the cotton leaves unless the dens hairs extend to the mid‐rib and other veins on the lower surfaces of the leaves.

3. The hair‐lengths within the ranges common on the tested varieties (514.3 μ‐690.1 μ) had apparently no significance in the mechanism of resistance to jassids.

Zusammenfassung

Verschiedene Versuche über die Anfälligkeit einiger Baumwollsorten gegenüber Jassiden zeigten folgende Ergebnisse:

a. In Stickstoff‐Düngungsversuchen zeigten die geprüften Sorten in den ungedüngten Reihen keine signifikanten Unterschiede im Jassiden‐Befall. Mit steigender Düngergabe konnte jedoch eine unterschiedliche Anfälligkeit beobachtet werden, wobei die Sorte “Bahteem 185” die geringste und die Sorte “Dandarah” die höchste Anfälligkeit aufwiesen.

b. Beim Test von 12 Baumwoll‐Sorten auf Jassiden‐Befall ohne unterschiedliche Behandlung erwies sich ein neuer Stamm von Gossypium barbadense als am meisten restistent gegenüber Jassiden, während ein anderer Stamm (Triespecies No. I, High recurrent) sehr anfällig war. Die übrigen 10 Sorten zeigten einen unterschiedlichen Grad der Anfälligkeit bzw. Resistenz, die zwischen den beiden obengenannten Extremen lag (Tab. 6).

c. In einem anderen Versuch mit 3 Aussaat‐Terminen, unterschiedlichen Reihenabständen und steigenden Düngergaben war die Sorte “Giza 66” zu allen 3 Varianten am anfälligsten. Die übrigen Sorten zeigten untereinander nur geringe Differenzen.

d. Bei der Prüfung unterschiedlicher Aussaat‐Termine (10. März, 25. März, 8. April, 3. Mai) konnte bei Baumwolle, die zum zweiten Termin ausge sät wurde, der geringste Befall festgestellt werden. Am höchsten war der Befall bei den am 3. Mai ausgesäten Pflanzen.

e. Ein Test über die Auswirkung von Behaarungsdichte und Haarlänge auf Jassiden‐Befall zeigte, daß mit zunehmender Haardichte der Befall zu rückgeht. Die Haarlänge der getesteten Sorten (514.3–690.1μ) hatte da gegen keinen gesicherten Einfluß auf die Resistenz gegen Jassiden.