Notes from Your Extension Agent

Ayman Mostafa and Shawna Loper

Cotton Planting Date Management: Now is the time to start planning for deciding when to plant. You can do this by watching the 5-day forecast and checking soil temperatures. Remember that the soil temperature plays an important role in cotton planting. For cotton seed emergence, optimum soil temperature is 65°F for at least 3 consecutive days at seeding depth. Soil temperature at 8am should approach 60°F when planting. A good weather forecast for planting should call for sunny skies with highs above 80°F and lows above 47°F. Check out: Planting Date Management publication by Dr. Jeff Silvertooth for some tips on cotton production efficiency to help decide on a planting date in Arizona. To help with your planting decisions, the weekly UA Cotton Advisories will be starting next week.

Root-Knot Nematode: With planting cotton just around the corner, something else to be thinking about is root-knot nematode (RKN). The root-knot nematode (RKN), Meloidogyne incognita, is a serious pest that infects cotton as well as sorghum, corn, melons, watermelon, peppers, beans, and many other crops. As we know the presence of nematodes can cause significant yield reductions in AZ cotton. The RKN is usually found in sandy or sandy loam soil, and is most active in the summer when soil temperatures are warm. This plant parasitic nematode is an obligate parasite that must complete its life cycle in a plant host; however, eggs are persistent and can remain inactive in the absence of a host and/or in fallow fields for months or years. Infection by RKN causes swellings (galls) on the roots. In cotton, these swellings are usually small and hard to detect. As a result, plants may be heavily infected even though galls are not easily visible. Management decisions must be made before or at planting; since there are few control options during the season. Some management decisions include planting tolerant or resistant cotton cultivars, rotating crops, sanitizing equipment to minimize the spread of nematodes, or using a nematicide. Accurate diagnosis of RKN infestation usually requires laboratory analysis for detection and identification. Good samples are important for accurate identification and quantification. For more information on “Sampling Soils for RKN”, check out this publication from Dr. Mary Olsen on Root-Knot Nematode.

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