Resistance to fungicides

The answer to the first question is in fact negative. The answers to the second were many, different, varied, and sometimes contradictory. In the section of this paper that follows, we will explore this matter of practical resistance to fungicides. 

In the next few paragraphs we will briefly summarize some recent experiences relating to practical resistance to fungicides. 

Table 12.5 Occurrence of practical resistance to fungicides. (After Brent Hollomon [23], supplemented.)...

Insecticides for resistance management. There are no equivalents to the mixture partners available for combating resistance to fungicides (the so-called contact materials) or herbicides (2,4-D. glyphosate, and paraquat here cultivation is also an option). Indeed, currently registered insecticides share a disturbingly few modes of action. 

The almost exclusive use of tria2oles foi ceieal powdery mildew control up to the mid-1980s has resulted in a shift in E.Tysiphe populations toward reduced sensitivity or resistance to this class of fungicides. However, use has continued because field performance of most tria2oles has remained adequate (43). Decreased a2ole sensitivity in the population to a2oles has also been noted. 

Akhunov et al. (2008) purified chitin-specific PO with fungicidal activity from cotton and observed the increase of its activity in plants, penetrated by Verticillium dahliae. Golubenco et al. (2007) showed the presence of the chitin-binding PO isozyme in Hibiscus trionum, which activated dramatically after inoculation by V, dahliae. The plants of Nicotiana tabacum overexpressing the anionic PO (chitin-specific according to our data) were more resistant to Helicoverpa zea and Lasioderma serricorne as compared with the wild-type (Dowd et al., 2006). 

Apart from the resistance of insects to insecticides, resistance has been developed by plants to herbicides, fungi to fungicides, and rodents to rodenticides. Rodenticide resistance is discussed in Chapter 11, Section 11.2.5. 

Up to 1952, over 30 fungicides had been tested by this method at La Lola farm of the cacao center (U3). Bordeaux mixture properly prepared was found to be resistant to tropical weathering and the most effective. In some experiments Phy-gon-XL fungicidal powder, Bioquin I, Crag 531, and others were as effective as... 

The methods of control include selection for resistance or field tolerance and Manis has announced excellent clones of this type that, remarkably enough, include resistance to both Phytophthora and Dothidella. The other control is by fungicides. Of several sprays tried, Dithane with sticker gave best results. Under usual moist weather conditions, applications are put on at 8-day intervals. During the more severe rainy season it is necessary to spray as often as twice a week. However, when continuous rainfall occurred for 10 days or more without cessation, and no spraying was possible, Phytophthora damage increased, and it was a struggle to get the disease under control when less difficult conditions returned. 

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