Weeds Act As Alternate Host To Insects, Pests And Diseases

weeds act as alternate host to insects, pests and diseases

Although they technically have different purposes and meanings, the words “alternate” and “alternative” are frequently used colloquially and interchangeably. The word “alternative,” which is used as a synonym for “substitute” or “replacement,” relates to “one that substitutes for or alternates with another,” “happening, occurring or succeeding by turns,” or “serving in place of another.”

One of “two or more available possibilities or options” or “an option or a choice that stands in place of the other” is referred to as a “alternative” in this context. An alternate host is a host that aids a crop pest in finishing its life cycle and comes from a different family than the main (or primary) host.

Additionally, it helps the crop pest survive in unfavourable circumstances. Numerous plant diseases (fungi, bacteria, and viruses) have a variety of alternative hosts where they may complete at least a portion of their life cycle. Because they are so common, invasive weed species guarantee the continuation of infection chains between weeds and crop hosts for a wide range of illnesses (White 1970).

It will become evident through an illustration of a typical heteroecious rust pathogen (Puccinia graminis var. tritici), which causes stem rust or black rust in wheat (Triticum spp., Poaceae family) and lives on barberry (Barberis vulgaris, Berberidaceae family). The primary and backup hosts are required for the pathogen’s life cycle to be completed.

For instance, the Pyricularia grisea (Teleomorph: Magnaporthe grisea) phytopathogenic fungi that causes blast disease in rice (Poaceae) infects grasses including Brachiaria mutica, Digitaria marginata, Dinebra retroflexa, Echinochloa crus-galli, Leersia hexandra, and others. Weeds as additional and different hosts for agricultural pests In the absence of a rice crop, 6 Panicum repens and other members of the same family subsist on these grassy weeds. The conidia (inocula) from the weed hosts are released during the next rice season, grown on bunds or nearby places, and then dispersed by wind or other means to infect the new crop by starting the disease in the rice nursery and/or main field. The continuing development and multiplication/reproduction of these diseases throughout the non-cropping season is made possible by the alternate hosts that are vulnerable to the phytopathogens of crop plants.

Alternate hosts of some important pest and diseases

Crops	Pest	Alternate host (Weeds)
Redgram	Gram caterpillar	Amaranthus, Datura
Castor	Hairy caterpillar	Crotalaria sp
Rice	Stem borer	Echinochloa, Panicum
Wheat	Black rust	Agropyron repens
Perl millet	Ergot	Cenchrus ciliaris
Maize	Downey mildew	Sacharum spontaneum