Specialists Speaking
Randy Norton
ARIZONA
Many of the pests that are of economic importance in Arizona cropping systems are readily identifiable through scouting of fields. However, one of the most damaging pests in our production systems that often go unseen is the plant parasitic nematode. There are several plant parasitic nematodes in Arizona, but the most widespread, and the one of most economic significance in our cotton production systems, is the southern root-knot Nematode (RKN – Meloidogyne incognita). Significant positive yield response has been observed in Arizona cotton systems with the use of effective nematode management techniques.
A significant portion of the soils across Arizona that are utilized for growing cotton are stream- and river-deposited alluvial soils containing the remnants of old streambeds and washes. This type of soil development and deposition is characteristically variable in factors such as soil texture. These variations in soil texture have been shown to affect both the population dynamic and the distribution of nematodes and have been suggested as a useful predictor of areas within a field of high potential for crop damage from nematodes.
Effective nematode management in Arizona hinges on an integrated approach that combines crop rotation, resistant cotton varieties, cultural practices, and chemical controls. Because nematodes persist in soil for many years and are difficult to eradicate completely, management focuses on reducing populations below economic thresholds.
Recent advances in cotton breeding have greatly improved access to varieties with strong resistance or tolerance to RKN. This may be an effective option if the variety with nematode resistance is also a well-adapted variety to the low desert growing conditions in Arizona. Chemical management options provide immediate, but often temporary, population reductions. In Arizona cotton, commonly used tools include pre‑plant fumigants and non‑fumigant nematicides applied in‑furrow or at planting. Because nematicides can be costly, economic returns are greatest when applied only to high‑risk zones identified through soil sampling or historical yield data.
The complexity of Arizona’s alluvial soils and the patchy distribution of root‑knot nematodes underscore the potential benefit associated with site‑specific management. By integrating tools such as soil mapping, resistant varieties, crop rotation, and targeted nematicide use into a proactive management strategy, Arizona cotton producers can significantly reduce losses from this “hidden enemy” and improve the resilience and profitability of their cropping systems. ∆
Randy Norton
ARIZONA
